ALBERT

Description: This paper offers a review of univariate and multivariate process capability indices (PCIs). PCIs are statistic indicators widely used in the industry to quantify the capability of production processes by relating the variability of the measures of the product characteristics with the admissible one. Univariate PCIs involve single-product characteristics while multivariate PCIs deal with the multivariate case. When analyzing the capability of processes, decision makers of the industry may choose one PCI among all the PCIs existing in the literature depending on different criteria. In this article, we describe, cluster, and discuss univariate and multivariate PCIs. To cluster the PCIs, we identify three classes of characteristics: in the first class, the characteristics related to the information of the process data input are included; the second class includes characteristics related to the approach used to calculate the PCIs; and in the third class, we find characteristics related to the information that the PCIs give. We discuss the strengths and weaknesses of each PCI using four criteria: calculation complexity, globality of the index, relation to proportion of nonconforming parts, and robustness of the index. Finally, we propose a framework that may help practitioners and decision makers of the industry to select PCIs.

Description: The incremental sheet forming processes (ISF) are attracting lots of attentions due to their advantages on rapid prototyping, without special dies and short lead time. The numerical simulation can be a valid method to investigate the forming process and predict the defects. In this study, an extended fully coupled ductile damage model with mixed nonlinear hardening was used to simulate the ISF process. At the same time, the yield surface distortion was also considered in this model, which can enhance the capability of modeling metallic material behavior under complex loading paths. Afterwards, some simulations were conducted with the proposed model. Additionally, one tension-shear orthogonal loading test was assigned on the one representative element in order to investigate the loading path effect during ISF process. By comparing the equivalent plastic strain and ductile damage evolution of the blank, the influence of the yield surface distortion on the ISF process was proved.

Description: Automated guided vehicles (AGVs) are being extensively used for intelligent transportation and distribution of materials in warehouses and autoproduction lines due to their attributes of high efficiency and low costs. Such vehicles travel along a predefined route to deliver desired tasks without the supervision of an operator. Much effort in this area has focused primarily on route optimisation and traffic management of these AGVs. However, the health management of these vehicles and their optimal mission configuration have received little attention. To assure their added value, taking a typical AGV transport system as an example, the capability to evaluate reliability issues in AGVs are investigated in this paper. Following a failure modes effects and criticality analysis (FMECA), the reliability of the AGV system is analysed via fault tree analysis (FTA) and the vehicles mission reliability is evaluated using the Petri net (PN) method. By performing the analysis, the acceptability of failure of the mission can be analysed, and hence the service capability and potential profit of the AGV system can be reviewed and the mission altered where performance is unacceptable. The PN method could easily be extended to have the capability to deal with fleet AGV mission reliability assessment.

Description: Self-piercing riveting (SPR) is a cold mechanical joining process used to join two or more sheets of materials by driving a rivet piercing through the top sheet or the top and middle sheets and subsequently lock into the bottom sheet under the guidance of a suitable die. SPR is currently the main joining method for aluminium and mixed-material lightweight automotive structures. SPR was originated half century ago, but it only had significant progress in the last 25 years due to the requirement of joining lightweight materials, such as aluminium alloy structures, aluminium-steel structures and other mixed-material structures, from the automotive industry. Compared with other conventional joining methods, SPR has many advantages including no pre-drilled holes required, no fume, no spark and low noise, no surface treatment required, ability to join multi-layer materials and mixed materials and ability to produce joints with high static and fatigue strengths. In this paper, research investigations that have been conducted on self-piercing riveting will be extensively reviewed. The current state and development of SPR process is reviewed and the influence of the key process parameters on joint quality is discussed. The mechanical properties of SPR joints, the corrosion behaviour of SPR joints, the distortion of SPR joints and the simulation of SPR process and joint performance are reviewed. Developing reliable simulation methods for SPR process and joint performance to reduce the need of physical testing has been identified as one of the main challenges.

Description: The process planning of V-bending involves the determination of a feasible sequence of bending tasks to achieve the final desired product shape. The feasibility of such a sequence is materialized by the absence of collision between the sheet metal and the tool set or any part of the press brake. Meanwhile, efficient process planning targets the minimization of the number of bending setup and handling tasks. This paper presents an enhanced automated feature recognition system for effectively determining part shape features that are suitable for feasible and efficient process planning of the V-bending process. The developed system automatically recognizes and reasons information of bend lines, and relations between them form STEP AP-203 format. It provides additional information regarding the relationships between bend lines based on a new classification that can facilitate efficient selection of tools and bend sequences. It also provides an easier approach for the estimation of some bend parameters compared to previous methods in the literature. An example is provided to demonstrate the benefit of applying the developed system in generating more efficient process plans.

Description: This paper presents a method for machining an annular groove on the inner wall of a steel tube by ball spinning. Based on spatial analytic geometry theory and assumptions about radial helical feed, the process utilizes a simplified expression of boundary curves of radial and tangential contact area between ball and workpiece. Through curve integration, the equations of radial and tangential contact areas for calculating ball-spinning force have been obtained. Based on results from calculation examples, this paper discusses the relationships between spinning depth, ball diameter, spinning feed, and ball-spinning force. The comparison of calculation results between the analytical model and the finite element method has been supplied, and the validity of the model has been certified.

Description: A novel principle for machining of deep holes is proposed. A self-centering positioner (SCP) was invented, and the principle for locating and guiding deep-hole drills using oil films was studied. The SCP is fixed between the drill tip and the drill shank. Four wedge-shaped zones are formed between the SCP and the wall of the machined hole. The rotating SCP draws cutting oil into the converging, wedge-shaped zones, which produces a pressure in each wedge-shaped oil film. The oil films will support, locate, and guide the SCP along with the drill tip and the shank. The oil films act on the SCP in a manner similar to that by which a four-jaw chuck clamps a workpiece, thereby enhancing the stiffness of the drill system and protecting the drill from deviation. The force exerted on the SCP by each oil film is calculated. Experiments showed that hole straightness was improved when using an SCP. The eccentricity ratio and width of the SCP strongly influence the force exerted on the SCP and straightness of the hole. A deep-hole drill with an SCP follows the axis of the hole during the machining process—in contrast to the current method in which the drill is guided by the wall of the hole. This novel principle applies to both symmetric and asymmetric deep-hole drills. It is derived from dynamic lubrication in bearings and serves as a break from the convention that has guided deep-hole machining for many years.

Description: In this study, an experimental target plate jet mill was designed and used to produce CuSn10 bronze powder from its machining chips. Taguchi method with an L 9 orthogonal array was used as experimental design to determine the optimum conditions for the pulverization of the machining chips via jet milling. The effect of process variables including nozzle to target distance, impact angle, and air pressure were investigated. The optimum conditions were found to be 8 cm for nozzle to target distance, a 90° angle between nozzle and target, and an air pressure of 7 bar. Repeated impact cycles lead to the production of finer and more rounded particles, although the rate of size reduction was reduced. The jet-milled powder did not contain any contamination, and the amount of the surface oxide of the jet-milled powder was even lower than that of the initial machining chips. Investigation of the fragmentation of particles revealed that the initial machining cracks were the main sites for breakage during pulverization. In addition, the delta phase in the microstructure of the bronze alloy plays an important role in the propagation of pre-existing cracks as well as creating new cracks.

Description: To reduce tooth surface errors and improve the quality of tooth surface morphology for the spiroid face gear manufactured roughly by die-casting, a method of shaving processing for this type of gears was developed. According to the differential geometry and the meshing theory of spatial crossed axes gears, the kinematics of the shaving processing for the spiroid face gear was analyzed, while the cutting velocity of both contact tooth surfaces was derived to illustrate the feasibility of gear shaving. With the designed tooth geometry of the shaving cutter, the simulation of generation of tooth surfaces for the spiroid face gear was developed. Machining experiments for such type gears were performed on a five-axis computer numerical control machine tool (CNC machine) with the axially grooved shaving cutters. The geometric error measurement of the shaved spiroid face gears was determined by D40 CNC gear measuring center. The research results are of sound great significance to improve the engagement and lubrication for the spiroid face gears.

Description: The purpose of this study is to diagnose defaults of the TR200-roughness meter by contact measurement using the same path with two opposite directions of the probe left and right. We conducted a series of tests on the same rectified part with a roughness of 0.553 μm using a roughness meter equipped with a TS100 standard probe at a probing path of 8.5 mm, a drive speed of 0.5 mm/s and a feedback speed of 1 mm/s. The originality of this present work focuses on the measurement default diagnosis of the roughness of the surface from the change in direction of the probe after each measure in the same trajectory. This approach validates the unreliability of a roughness meter in the case of parts machined by cutting processes (turning, milling, and grinding). These tests have enabled us to limit the control of the surface state by a TS100 standard probe. For each test, a disagreement was found between the right and left directions by making the calculation of roughness parameters. Estimator fuzzy logic was implemented to solve this problem, obtaining satisfactory results with minus proportional errors between the actual displacement curve and the curve displacement obtained by this system.

Description: A mathematical model of friction coefficient was established to calculate the roll force during hot strip rolling process. Firstly, a linear regression model with four input variables was proposed to describe friction behavior, namely rolling speed, strip temperature, reduction rate, and the number of rolled strips since roll change. Then, the method of principal component regression, which can eliminate the effect of multi-collinearity among the input variables, is used to build the friction model. The obtained model was tested by statistical functions, and the results indicated that the model was valid and showed as well that the cumulative contribution rate of the first two principal components of the regression model was as high as 98% and the first two principal components contained almost all the information of original input variables. The industrial experiment confirmed that the roll force model with the proposed friction model had the higher prediction accuracy than the Sims model, and the proposed model could be used in online calculation for hot-rolled roll force.

Description: Material extrusion-based additive manufacturing (AM) is an effective tool in producing prototypes and final parts without geometrical complexity limitations. Despite having widespread applications and enormous advantages over conventional manufacturing techniques, the proliferation of extrusion-based AM has been limited by the low deposition quality and the poor surface finish of printed parts. To address these issues, an optimized path planning technique is proposed in this paper. The sharp corners and the non-uniform spacing between adjacent path elements in the final planned path are two major causes of unevenness of the deposited surface. The proposed method tries to decrease the number of sharp corners by using an implicit algorithm derived from the level sets of the input contours. The curvature information is used to smooth the generated contour paths. Subsequently, to achieve uniform spacing, local optimization is applied on the smoothed path by adaptively adjusting the locations of points on the path. These optimizations lead to a smoother part surface, when compared to those of typical fill path techniques. The proposed method is validated using several examples of parts, many of which are then constructed using a 3D printer.

Description: A detailed cutting tool design approach, tool shape-performance-application integrated design (TSpaiD) approach, is proposed to address the cutting tool specification trend. Based on the concept, a three-tier architecture, consisting of shape, performance and application layers, is developed to optimise cutting tools and machine conditions together. Within the context, multi-objective optimisation combining linear weight method is employed to address the machining requirements which are represented by each individual objective. Also, the cutting tool and the machining conditions are described by feasible set bounded by machining requirements and manufacturing resource. To implement the method, a software prototype is developed, and then a numeral validation, a genetic algorithm based optimisation, is given.

Description: The paper deals with experimental investigations of the influence of laser beam and plasma arc cutting parameters on edge quality of a range of steel grades and thicknesses. Based on the experimental results, a variety of methods have been taken to carry out the analysis of influence of laser beam and plasma arc cutting parameters on the quality and mechanical properties of cut edges of selected high-strength low-alloy (HSLA) strips and plates. In this study, three approaches were investigated corresponding to rank correlation analysis, multidimensional data analysis and decision trees. These techniques were able to elucidate the most relevant cutting parameters as well as the optimal field of values of these parameters to give the required geometrical and mechanical quality levels. As a result of this study, general rules in the form of cutting procedure specifications were established. This was needed to describe the relation between laser beam or plasma arc cutting parameters and the geometrical and mechanical quality factors of cut edges of different medium- and high-strength steel materials. The proposed rules can be also adopted for providing a comparison between the surface qualities achievable by the different combinations of cutting parameters for laser beam and plasma arc cutting processes of medium- and high-strength steels.

Description: Controlling product geometric quality is an important issue, because real parts deviate from their nominal value (e.g., in form, orientation, and position error of features, size of part, etc.). To analyze the influence of these deviations on final product, one solution is to consider the nonnominal Skin Model Shape to simulate assembly, manufacturing, or metrology. The modeling of nonnominal parts is still in its initial phases. First, methods of generating a single feature with deviations are reviewed and classified. With the combination of the single nonideal features to obtain the complete nonideal model of the part, geometrical issues appear, such as gaps and self-intersections. These can be influenced by acute and obtuse angles and the ratio between mesh size and deviation value. From an analysis of these issues, two deviation combination methods are proposed to preserve the manufacturing deviation of features and consistency of the model. These methods are qualified as local and global methods. The local method is based on the iterative calculation of mesh regularization. The global method is based on finite element analysis, with manufacturing deviations added to the nominal model by the penalty function approach. The effectiveness and efficiency of both kinds of method are compared on a trial geometry. The global method is preferred as it needs no iterative calculation, no stop criteria and gives better results. Finally, the proposed method is validated on a more complex mechanical part: a cutter body.

Description: Due to some special properties, alloy cast iron HTCuCrSn-250 is widely used to manufacture the cylinder block of the diesel engines. However, the additional alloying elements aggravated tool wear which is significantly affected by cutting parameters during machining process. In this paper, tool wear in face milling of alloy cast iron under constant material removal volume (MRV) condition was investigated. First, the relationship between tool flank wear ( VB ) and MRV was determined. Secondly, the wear morphology and mechanism were analyzed and a predicted model between cutting parameters and tool wear was proposed. Finally, the optimization was taken, and three groups of optimal parameters were obtained. This research illustrated that different combinations of cutting parameters result in different wear morphology and the main wear mechanisms are diffusion and oxidation. This research also indicated the two parameters, axial depth of cut and the radial depth of cut, which have significant impact on the tool wear. Meanwhile, a model between VB and the cutting parameters under the constant MRV condition during milling HTCuCrSn-250 was proposed.

Description: In this study, a low-cost infrared sensing system based on the analysis of the surface temperature distribution is proposed for monitoring the perturbations occurring during the aluminum alloy metal inert gas (MIG) welding process. A galvanometer scanner is employed in this real-time infrared sensing system to continually reflect the infrared energy to the point infrared sensor. By controlling the scanning mirror of the galvanometer scanner rotating in a high speed, the infrared energy at different points of the welding seam and the heat-affected zone on the surface of the plate will be continually captured by the point infrared sensor. Different conditions (changes in the welding speed, welding current, and joint gap width) of the welding process have been simulated to perturb the welding process. Three representative geometric defects such as undercut, humping, and lack of fusion were produced to validate our infrared sensing system. Experimental results showed that the sensing system is useful for monitoring perturbations that arise during the welding process and identifying welding defects.

Description: In the present paper, dry sliding wear tests were performed on S335 steel coated with hard layer (Ti–W–N) with thickness at 2 μm at different sliding velocities (2.5 and 5 cm/s), sliding distances (9.42 and 18.80 m), and applied loads (2 and 4 N). These tests have been studied using a pin-on-disc machine, and the results are presented. Mathematical models for dynamic friction coefficient, wear volume or volume loss, and total roughness were developed using the response surface methodology (RSM). Wear mechanisms for S335 steel were characterized by scanning electron microscopy. Two wear mechanisms have been identified irrespective of the applied load: crack wear occurs at the lowest sliding distances and delamination wear occurs at the highest. Also, results indicated that by increasing the sliding velocity and sliding distance, a transition from crack wear to delamination wear occurs with a corresponding maximum in the loss of volume due to wear.

Description: The great challenge of the modern industry is carrying out an online prediction in the shop floor during the machining to define the exact instant of tool breakage and simultaneously improve the quality of manufactured products. This work shows a study to examine the effect of the feed rate, depth of cut, cooling system, and type of tool on the responses: surface roughness, passive force (Fp), feed rate force (Ff), cutting force (Fc), and micro hardness in the turning of Ti-6Al-4V titanium alloy. Experimental tests were carried out with workpieces 4 mm in diameter, and the surface roughness, micro hardness, and cutting efforts were analyzed. The analysis of variance was used to define the influence of input parameters on the responses. The results showed that the lowest surface roughness was achieved using the carbide tool with code TPMT and the lower input parameters, but the most important parameter was feed rate. The cutting efforts were influenced by feed rate and depth of cut. On the other hand, the cooling system does not show good efficiency in the cutting efforts. However, the geometry of the tool and the Minimum Quantity Lubrication system were more effective to cause the hardening in micro scale at the surface of the material.

Description: Copper wire bonding process is widely used in the electronic packaging of system integration with various heterogeneous and homogeneous components due to the advantage of cost. In this paper, an achievement of parallel microgap resistance welding with 40-μm copper wire on 300-nm Au-plated quartz pendulous reed used in precision mechanical and electrical product was presented. Research on orthogonal design of experiment was carried out, and the effect of process parameters was discussed on the shape of bonding interface, tensile force, and shear force by variance analysis. It is shown that too large a heat input and electrode pressure can cause the gold layer to wrinkle or fuse and cause bonding interface mechanics performance to fall sharply. A group of optimized process parameters (0.84 N of bonding pressure, 0.45V of bonding voltage, and 17 ms of bonding time) is obtained. Reliability tests including the thermal shock, random vibration, and electric aging tests on optimized process parameters were carried out, and the mechanical properties and physical properties of the bonding interface were mainly focused. It is shown that the bonding interface resistance increases slightly and the overall bonding interface tensile strength falls slightly after 500 cycles of thermal shock test. However, there is no change during the random vibration process. When electric aging time is less than 200 h, bonding interface morphology does not change and there is no crack. When electric aging time is 360 h, bonding interface deforms and crack occurs. When electric aging time reaches 720 h, bonding interface crack area increases, and it eventually fails. It is experimentally proved that a bonding interface with better performance can be achieved by parallel microgap resistance welding with 40-μm copper wire on 300-nm Au-plated quartz pendulous reed.

Description: In the electrical discharge machining (EDM) process, the aspects of the cutting performance such as material removal rate (MRR), surface roughness, crater geometry, and tool wear ratio are affected by the energy distribution. The difference in energy distribution during the EDM processing of Al6061, Inconel718, and SKD11 has been rarely studied. However, energy distribution is one of the most important parameters utilized in most existing models of the EDM process. In this paper, the energy distribution that occurs while processing these three materials is investigated by an experimental study under different EDM parameters, including current and pulse duration. Then, the relationship between the energy distribution and the specific discharge energy (SDE) is investigated. The results demonstrate that the discharge energy transferred to the above three kind of workpiece is small, and the fraction of energy distributed into the workpiece varies with discharge current and pulse duration form 7.998 to 12.005%, 2.879 to 3.485% and 2.976 to 3.716% for Al6061, Inconel718, and SKD11, respectively. These findings are consistent with previous studies. In addition, the optimization of the process parameters is investigated for these three materials, considering the MRR and the discharge energy efficiency simultaneously. This findings presented by this paper may be further used in existing thermal-physical models to improve the technological performance of such models.

Description: Isothermal local loading forming (ILLF) provides a new way to form large-scale Ti-alloy rib-web components (LTRC). However, the material undergoes complex inhomogeneous deformation in transitional region, which influences the forming quality of the component. The purpose of this paper is to improve the deformation homogeneity of the transitional region in ILLF by optimizing unequal thickness billet (UTB), which can adjust the initial volume distribution and control material flow with low cost and high efficiency. Based on the finite element (FE) simulation, the strain distribution of the transitional region in ILLF was investigated. It is found that the strain concentration at the root of formed rib in the first-loading region is more intense than that in the whole loading forming. Besides, the most strain concentration occurs at the root of partitioning rib on the side of first-loading region, which was not observed in the whole loading forming. The material transferred into the first-loading region during the second-loading step, and subsequent rib shift is the fundamental reasons for the strain concentration. The initial volume distribution of UTB has a significant effect on the strain concentration. In order to optimize the UTB, the average strain of strain concentration zone was correlated with geometric parameters of UTB by using response surface method (RSM). Based on the RSM model, the optimized UTB was achieved. The FE simulation of optimized UTB shows that the transferred material, rib shift, average strain, and maximum effective strain were all effectively decreased compared with equal thickness billet outcomes. The present RSM-based optimization method of UTB is proven to be a promising strategy to improve the deformation homogeneity of the transitional region in ILLF.

Description: The influence of inner fillet radius, as part of the shear deformation zone, on effective strain homogeneity in equal channel angular pressing (ECAP) of AZ91 magnesium alloy was analyzed in this paper. The uniaxial compression and ring upsetting were carried out to obtain the true stress-strain curve of AZ91 billet and friction factor between billet and die, respectively. The flow net experiment and hardness testing experiment were used to verify the simulation results. The results show the inner fillet radius, as the secondary factor (as we all known, the outer corner angle was the most important factor), had an influence on both the quantity and distribution of effective strain. With the increment of inner fillet radius, the effective strain value decreased in both the inner and outer regions. This mainly attributed to the alleviating effect of compression stress of extruded billet in ECAP.

Description: White layer formed on machined surface during dry and hard high speed machining has great influence on workpiece performance. Studying machined surface white layer is significant to improve the machinability and surface quality of workpiece. Experiments of dry and hard high speed machining of GCr15 bearing steel and 40CrNiMoA alloy steel were carried out with PCBN inserts, the phase composition and the thickness of white layer were studied experimentally; the formation mechanism of the white layer were studied; effects of cutting parameters, carbon content of substrate material on white layer thickness were analyzed; effects of cutting speed on retained austenite content in machined surface were also summarized. Results show that the microstructure of white layer consists of cryptocrystalline martensite, retained austenite and carbide; the white layer is formed by martensitic transformation; the white layer thickness and the retained austenite content of machined surface increase firstly and then decrease with cutting speed; the white layer thickness increases with flank wear and carbon content.

Description: In the present paper, a simple numerical method is proposed to predict the hole contour in a workpiece due to the action of a multi-pulsed laser. A 3D transient heat conduction equation has been used to predict the temperature at various points in the workpiece subjected to multi-pulsed (Gaussian beam (TEM 00 ) mode) laser beam. Subsequently, the hole contour is predicted from the melt isotherm contour in the workpiece. A finite difference implicit splitting scheme has been chosen to solve the above 3D transient heat conduction equation because of several advantages of this techniques over other techniques. The predicted hole contour has been verified with the experimentally obtained hole contour under similar condition of laser and process parameters. It is observed that the numerically predicted hole contour is matching fairly well with the experimental hole contour. The second objective of this paper is to exploit this numerical model to obtain an optimum combination of laser and process parameters for getting a good quality hole. Hence, the proposed numerical model can be used to set optimum process parameters for laser-drilling operation in industrial applications.

Description: Control over the quality of roll-to-roll gravure-printed silver-nanoparticle electrodes such as continuity, line width, and thickness is of importance to create high-resolution patterns of low resistance. In this regard, the multi-response optimization of gravure printing is required for industrial practice. To address this problem, the Taguchi method coupled with principal component analysis has been applied for multi-objective optimization of roll-to-roll gravure printing of silver-nanoparticle electrode to attain optimal condition within design space. The three-quality characteristics including continuity, pattern line width, and pattern thickness were simultaneously considered for optimization. The process parameters with three levels considered are ink viscosity, air nip pressure, and printing speed. First, Taguchi method was utilized to determine single-objective optimization. Then, the signal-to-noise ratios obtained from Taguchi method were used in principal component analysis to define a weighting factor of three-quality characteristics for multi-objective optimization. Finally, experiments were conducted to evaluate the proposed method, and the results demonstrate an improvement to the well-defined line width, thickness, and continuity of silver-nanoparticle electrodes under optimal parameter settings.

Description: A thermo-mechanical re-meshing model of friction stir welding (FSW) process of AA6082-T6 is used with a point tracking method for the determination of the final locations of the particles. The relations between the field variables and the material flows in the FSW process are discussed. Then the grain sizes after recrystallization are calculated. The comparison with the numerical and the experimental results in published literatures shows the validity of the proposed model. Based on the Zener-Hollomon parameter, the effects of strain rate and temperature on recrystallization are further discussed.

Description: Study on the mechanism and the suppression method of wrinkling in side wall of the aluminum alloy fairing using hydroforming, and the side wall is suspended curved surface shell. The wrinkling problem of side wall is analyzed on conical parts by combined with the theoretical calculation, finite element method (FEM) and experimental verification. To reduce the complexity of forming, the suspended surface is divided into several parts, and they are analyzed by theoretical calculation and FEM to discuss the rationality of the two schemes, which is proposed. And the critical strain is the wrinkling evaluation index, the size, and the amplitude of the critical strain can be the qualitative analysis of wrinkling trend. The suspended surface is divided into two regions, the trend of material flow is studied in the geometric view, and predicts the possibility of the wrinkling. The wrinkling of the suspended surface is not only related with the geometry of the part, but also be related with the loading path. It is controlled the qualitative analysis of wrinkling by adjusting the parameters about loading path, and get the relationship of pressure and punch stroke when the wrinkle happens. The qualified parts can be obtained in each process through optimized the parameters in the process of loading.

Description: An acid digestion test has been widely used to determine the fiber volume fraction, V f and void content of the PMCs laminate. Three main testing parameters of volume of acid, digestion period, and temperature were found to influence the resin extraction during the test. The study was aimed to establish the optimum values of those testing parameters through the use of statistical method of RSM. The exact values of each parameters was evaluated based on V f , and hence, the percentage of difference in comparison to the target value. The results have indicated that the proposed mathematical model could adequately describe the performance indicators within the limits of the factors investigated. As per described via the model relationship, the optimum condition were established as 30 ml of sulfuric acid and 3.5–4 h of digestion period at 175 ± 5 °C. The error between the predicted and actual experiment values were between −1.52 and −2.43%.

Description: The laser surface processing parameters and tribological properties of a textured surface filled with Gr-MoS 2 -PI-carbon nanotube nanocomposite solid lubricant under oil lubrication were investigated. Micro-dimples were fabricated on GCr15-bearing steel material using Gaussian-shaped beam profile nanosecond semiconductor sound and light-pumped Nd:YAG laser machining equipment. Friction and wear tests were performed using MMW-1A testing machine with the flat-on-flat configuration under different conditions in air. The results show that micro-dimple morphology is affected strongly by the laser head to sample surface distance, pulse repetition frequency, and single pulse energy. Additionally, the textured surface filled with solid lubricant (TSL) exhibited an enhanced tribological performance as compared to the textured (T) and smooth (S) surfaces under dry friction condition. In the oil medium, the efficiency of the textured surface (TO) was 18%, while the textured surface filled with solid lubricant (TSO) was 22% as compared to the plateau smooth surface (SO). Furthermore, under different conditions of load and rotational speed, the solid-oil composite lubricating film effectively reduces the friction and wear on the surface of the sample. The research results identified that the good lubrication and anti-wear properties of the TSO sample were mainly attributed to the double-action lubrication system and synergistic lubricating effect generated by the composite solid lubricant and oil.

Description: In this paper, a kind of flow-solid sequence coupling technology for forming large aluminum alloy automotive covering parts was presented. Firstly, the numerical simulation of hydraulic bulging process was carried out. Then, the springback analysis and mold surface compensation for the simulation results were implemented. The hydraulic bulging test was made by using the optimized compensation surfaces of mold, and the hydraulic bulging parts with relatively accurate shape were obtained. The accuracy of the numerical simulation results was verified by comparing the experimental values and simulation values of the 3D deviation on the same measurement paths; then, in order to form the small fillet features in three different areas of the part, the numerical simulation and experiment research of the stamping technology were carried out on the part obtained by the hydraulic bulging process. The accuracy of the numerical simulation results was verified by comparing the experimental values and simulation values of the thickness distribution on the measurement path; finally, using the numerical simulation of fluid-solid sequence coupling forming process and the matching experiment, the changing rules of the first principal strain and the second principal strain in the small features were studied from the angle of the qualitative and quantitative analysis and it was fully verified that the small characteristics have deformed sufficiently at the end of local shaping process with the rigid die.

Description: The vision of smart shop floor is based on the notion of Industry 4.0 that denotes technologies and concepts related to Cyber-Physical Production Systems (CPPS). In smart shop floors, CPPS monitors physical processes, creates a virtual copy of the physical world, and makes decentralized decisions. CPPS allows virtual world to store data, process data, communicate, and cooperate with each other in real time. This paper presents architecture of smart shop floor based on physical, logical, and communication layers that embed intelligent approaches within manufacturing processes. Every physical entity in the smart shop floor is regarded as an autonomous intelligent logical unit that performs operations guided by distributed control functions. Moreover, computing power and optimization approaches are embedded into each logical unit to make decisions to agilely respond to frequent occurrence of unexpected disturbances at the shop floor. A test platform has been set up to demonstrate how physical entities can be cooperative and autonomous logical units that can automatize the shop floor operations. The results verify the feasibility and efficiency of the proposed method.

Description: A new method of optimization on the hot forging tools for connecting rods was developed in this paper by combining response surface analysis (RSA) with finite element method (FEM). The central composite design (CCD) was prepared with three experimental factors and two optimal targets. The experimental factors which are extracted from design dimensions of the hot forging tool involve cavity center distance, cavity rotation angle, and flash thickness. The targets comprise the maximum forming load and tool wear depth, both of which can be obtained from finite element simulations of hot forging processes. Response surface analysis was implemented to establish the relationships between the targets and the factors. According to the simulation results, the S-type region between die cavities that was dominated by three factors has a significant impact on the metal flowing and forming defects during the hot forging process. The steel billet and forging tools were dimensionally redesigned based on the optimal combination of experimental factors. Practice forging and physical experiments were performed to verify the simulation results, and good agreement between experimental value and simulation value was obtained.

Description: A new approach is developed in this paper to predict the three-dimensional gear surface topography in the process of gear generating grinding, and a parametric equation is derived to describe the trajectory on the tooth surface of gear left by each ideal sphere grain. To determine the final three-dimensional gear surface topography generated by thousands of single abrasive grain with randomly distributed locations and protrusion heights, an algorithm for geometrical analysis is developed to systematically process the gear surface profile. There are two steps for this method: the first step is to map the cutting path to the tooth profile in each generating stroke, and the second stage is to combine these generated surface topographies together and trim them in an appropriate manner to create a whole tooth surface. The simulation results show that the surface roughness is increasing monotonously along the tooth profile direction, which is confirmed by the experiment. In order to get uniform surface roughness, a non-uniform generation method is introduced by dividing the entire arc length into isometric n segments. With the use of this method, the surface roughness in each part is essentially equal. Besides, the surface roughness improves about 16.3 % when the machining time is the same, and the reduction of machining time is 42.8 % when the surface roughness of addendum is equal.

Description: Despite the importance of the polyphthalamide (PPA) composites in many industrial applications, especially for automotive industry, very little is known about the machinability of these composites. This paper presents the drilling characteristics of PPA matrix composite materials having glass fiber of 30 % reinforced by using HSS, TiN-coated HSS, and carbide drills. The influence of cutting parameters, for example cutting speed and feed rate, on the delamination factor and surface roughness of the composites has been examined during the drilling operations. Experimental results have demonstrated that as cutting speed increases, surface roughness decreases, and as feed rate increases, surface roughness increases as well. Higher cutting speeds and lower feed rates generate better surface quality. The drilling test results have demonstrated that the delamination factor increases through the increase of feed rate and decreases through the increase of cutting speed. It is obtained the best results of the delamination factor at higher cutting speeds and lower feed rates. The machined surface is examined by means of scanning electron microscopy (SEM). SEM images of the machined surfaces show the presence of cracks, fiber pullout, and shearing of fibers.

Description: In this work, an ultrasound force control strategy for autonomous dry contact ultrasonic inspection of an object having rough surfaces is proposed. A fuzzy rules emulated network (FREN) controller with adaptation based on IF-THEN rules obtained from the physical system is developed. The control scheme is implemented on a three degree of freedom Cartesian manipulator robot that carries a soft contact hemispherical end effector equipped with an ultrasonic sensor. This allows smooth regulation of the transmitted ultrasound energy through the contact interface between the hemispherical probe and the rough surface. The controller is a pure model-free controller which does not require a mathematical model of the contact interaction. The effect of roughness condition at the contact interface, Hertzian interaction and the hysteretic effect due to nonlinearity of the elastomer material of the probe, on the performance of the controller is studied. The system was tested on five samples with surfaces having different values of roughness. It was shown that the system using the proposed scheme with adaption parameters is stable during the transition from noncontact to contact conditions. Also, it is shown that the developed ultrasound amplitude-force controller is able to reach and maintain a desired constant ultrasonic energy transfer to the test objects under variations of surface roughness conditions.

Description: Cutting force monitoring is an important technology for tool condition monitoring. However, a high precision and wideband cutting force estimation, including cross-feed components, with a sensorless approach of the ball-screw-driven stage, is still challenging because of its multiple structural modes and non-linear friction. This study proposes a process monitoring technique that independently estimates the cutting force components in rigid body and in vibration mode coordinate systems, based on multi-encoder signals. In the rigid body mode, the cutting force components were estimated by extracting the static rigid-body motion. In the vibration mode, the cutting force was estimated by using the relative displacement, velocity, and acceleration between the motor and the table. The estimation accuracy of the cutting force in feed and cross-feed directions was evaluated through several end milling tests. In the rigid body mode, a temporal variation of the feed force components was observed. However, high-frequency variations irrelevant to the cutting force were included because of variations in motor current, which had position/rotation-dependent characteristics. On the other hand, in the vibration mode, it was possible to estimate both feed and cross-feed components with less than maximum static friction force, including high harmonics.

Description: Due to the approximation errors of interpolation methods in non-uniform rational b-spline (NURBS) interpolation, feed fluctuation is inevitable, which has great effects on the machining quality and should be minimized. Based on the idea of zero feed fluctuation, a polynomial equation-based interpolation method of NURBS tool path is proposed in this paper. Firstly, a polynomial equation with respect to the curve parameter increment is formulized according to the sampling step size, which is determined by the scheduled feedrate, acceleration, and jerk. Then, Newton’s method is utilized to solve the high-degree polynomial equation with taking both convergence rate and computational load. In order to improve the computing efficiency in real-time interpolation, a fast-evaluation and derivation algorithm is proposed, which uses the Taylor series expansion to accelerate the calculation of any order derivatives of NURBS. Simulations are conducted among the proposed method and the chord-tracking algorithm (CTA) method, and the results of each method are compared on the basis of computing time and feed fluctuation, which shows that the proposed method is better than the CTA method. Experiment is also conducted to verify the feasibility and applicability of the proposed method in practical application.

Description: A new management algorithm to improve performance and reliability of an off-battery autonomous energy system consisting of DFIG based wind energy converter (WEC) and diesel generator (DG) is proposed in this paper. Among its several constraints, the most significant ones are the limitation of wind power penetration and rotor side converter safety due to both the load demand variation and wind speed fluctuation. The proposed algorithm consists in maximizing load connection to the DFIG-based WECS and limiting the use of DG to only priority load taking into account some criteria to respect. A decision is made up with reference to specific rules on the basis of the measured wind speed and the predicted load demand. A stator flux-oriented technique for rotor side converter is presented to regulate voltage and frequency at stator/load terminals. Different possible case studies are presented to show the effectiveness of the proposed algorithm. Simulation results obtained from a 250 KW DFIG based wind power system are given and discussed in this paper.

Description: The main goal of this study is to investigate the forming kinematic and the developed loads during the countersinking process. A compression test was performed to characterise the behaviour of the used sheet metal. An elasto-plastic finite element model was used to predict the forming kinematics, the developed loads and the final shape of the countersink. A configuration with a maintained blank-holder was performed for this study. New phenomena of forming kinematic were observed and investigated. The simulation results were in good agreement with the experiments, and they showed the capability of the adopted finite element model to predict the loads and the final shape of the countersunk workpiece.

Description: In order to obtain an ultrasonic elliptical vibration device with a simple structure, a novel single-driven ultrasonic elliptical vibration cutting (SDUEVC) device with a complex-beam horn (CBH) is introduced and investigated in this paper. Using the theory of mechanical vibration, a mathematical model of the CBH is described. We studied the vibration characteristic of the SDUEVC using the finite element method (FEM). Experiments were carried out to investigate the vibration characteristics of the SDUEVC device prototype using a vibrometer, an oscilloscope, and a data processing system. In addition, the cutting characteristic of the prototype was verified. Our experimental results show that, compared to conventional cutting (CC), the SDUEVC device can reduce the cutting force and surface roughness.

Description: In order to reduce the height of the protrusion on the clinched joint, a height-reducing method by compressing the joint was studied in the present work. An investigation of effects of geometrical parameters on the strength and energy absorption of the height-reduced joint was carried out by experimental method. A series of experiments were performed by varying the geometrical parameters of the joints. Different forming displacements were applied to generate different geometrical parameters in the mechanical clinching process. The tensile strength of the height-reduced joint is higher than that of the mechanical clinched joint. The height-reduced joint with a bottom thickness of 1.5 mm has the highest tensile strength. The height-reducing method can contribute to increase the energy absorption of the joint. The strength and energy absorption of the joint depend on the neck thickness in this study. The height-reducing method can increase the tensile strength and energy absorption of the joint by increasing the neck thickness. The height-reducing method with a pair of flat dies is a helpful subsequent process of conventional mechanical clinching.

Description: In the present paper, a simple numerical method is proposed to predict the hole contour in a workpiece due to the action of a multi-pulsed laser. A 3D transient heat conduction equation has been used to predict the temperature at various points in the workpiece subjected to multi-pulsed (Gaussian beam (TEM 00 ) mode) laser beam. Subsequently, the hole contour is predicted from the melt isotherm contour in the workpiece. A finite difference implicit splitting scheme has been chosen to solve the above 3D transient heat conduction equation because of several advantages of this techniques over other techniques. The predicted hole contour has been verified with the experimentally obtained hole contour under similar condition of laser and process parameters. It is observed that the numerically predicted hole contour is matching fairly well with the experimental hole contour. The second objective of this paper is to exploit this numerical model to obtain an optimum combination of laser and process parameters for getting a good quality hole. Hence, the proposed numerical model can be used to set optimum process parameters for laser-drilling operation in industrial applications.

Description: In paper, weld joints between VT1-0 titanium and AISI 321 austenitic stainless steel using laser welding were obtained. To improve the quality and strength properties of joints, two types (SS–Cu–Nb/Ta–Ti) of explosively welded four-layered composite inserts were used. Barrier layers were different from each other by refractory metal. The effect of intermediate material inserts, in particular tantalum and niobium, on microstructure, chemical composition, strength properties, and fracture behaviour of weld joints was studied. Microstructural studies have revealed two bonding types as results of welding method combination. At copper–stainless steel interface, severely deformed zone characterized by low etch ability was observed. Technological parameter’s optimization provided high joint quality and absence of defects in the weld joints. According to results of strength tests, it was found that the composite insert material affects the strength of the joints. The highest ultimate tensile strength and yield strength were detected for joints containing niobium foil.

Description: Energy efficiency in industries is one of the dominating challenges of the twenty-first century. Since the release of the first eco-design directive 2005/32/EC in 2005, great research effort has been spent on the energy efficiency assessment for energy using products. A missing piece for finalizing the ISO 14955-2 is the quantification of a machine tool’s non-electric power demand due to external support systems such as compressed air systems, water cooling systems, air conditioning systems, and exhaust air systems. These systems are comprised to the technical building service and cause additional electrical power demand that can be assigned to a machine tool. A model is set up that links the machine tool and the technical building services. The model enables to deduce the electrical power demand of the technical building service caused by non-electric power demand of a machine tool using electrical energy equivalents. Hence, the total electrical power demand caused by a factory-integrated machine tool can be derived. The applicability of the model and the electrical energy equivalents is proven in a practical case study on a grinding machine.

Description: In this paper, ultrasonic echo signals of four kinds of stainless steel resistance spot welds, namely failed weld, stick weld, good weld, and defective weld with gas pore, are analyzed in the time domain, frequency domain, and time-frequency domain based on wavelet packet transform. Fourteen ultrasonic characteristic signals which can reflect the different kinds of spot welds are extracted and can be automatically identified and classified by back-propagation (BP) neural network. The method of this paper can realize the intelligent identification of resistance spot welding defects, and the feasibility of this method has been verified in the experiment.

Description: Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical methods for the machining of metal matrix composites and conducting ceramic blanks. However, the machining process of Ni–Al 2 O 3 functionally graded materials (FGMs) is extremely difficult because the insulating ceramic layer cannot be machined directly by EDM. In this paper, the pure Al 2 O 3 layer has been machined by self-induced EDM, using the conductive layers of Ni–Al 2 O 3 FGMs to trigger the discharges in the insulating ceramic layer. Machining experiments have been performed to investigate the effects of discharge capacitance, pulse off-time, and charging resistance on the process performance of the pure Al 2 O 3 layer using RC-type pulse generator. From the experimental results, the discharge waveform of pure Al 2 O 3 layer includes long pulse discharge waveform, in addition to conventional normal discharge of conductive layers. The shape of long pulse discharge waveform can be changed by pulse off-time. The appropriate pulse off-time not only improves the stability of EDM but also increases the material removal rate (MRR). Moreover, it was observed that the MRR increases with increasing discharge capacitance and decreasing charging resistance. The surface roughness increases with increasing discharge capacitance. Finally, a small hole with a depth-diameter ratio of 5, little tapper is machined based on the experimental analysis.

Description: A new method of optimization on the hot forging tools for connecting rods was developed in this paper by combining response surface analysis (RSA) with finite element method (FEM). The central composite design (CCD) was prepared with three experimental factors and two optimal targets. The experimental factors which are extracted from design dimensions of the hot forging tool involve cavity center distance, cavity rotation angle, and flash thickness. The targets comprise the maximum forming load and tool wear depth, both of which can be obtained from finite element simulations of hot forging processes. Response surface analysis was implemented to establish the relationships between the targets and the factors. According to the simulation results, the S-type region between die cavities that was dominated by three factors has a significant impact on the metal flowing and forming defects during the hot forging process. The steel billet and forging tools were dimensionally redesigned based on the optimal combination of experimental factors. Practice forging and physical experiments were performed to verify the simulation results, and good agreement between experimental value and simulation value was obtained.

Description: A new approach is developed in this paper to predict the three-dimensional gear surface topography in the process of gear generating grinding, and a parametric equation is derived to describe the trajectory on the tooth surface of gear left by each ideal sphere grain. To determine the final three-dimensional gear surface topography generated by thousands of single abrasive grain with randomly distributed locations and protrusion heights, an algorithm for geometrical analysis is developed to systematically process the gear surface profile. There are two steps for this method: the first step is to map the cutting path to the tooth profile in each generating stroke, and the second stage is to combine these generated surface topographies together and trim them in an appropriate manner to create a whole tooth surface. The simulation results show that the surface roughness is increasing monotonously along the tooth profile direction, which is confirmed by the experiment. In order to get uniform surface roughness, a non-uniform generation method is introduced by dividing the entire arc length into isometric n segments. With the use of this method, the surface roughness in each part is essentially equal. Besides, the surface roughness improves about 16.3 % when the machining time is the same, and the reduction of machining time is 42.8 % when the surface roughness of addendum is equal.

Description: In the present study, friction stir lap welding (FSLW) of 1 + 1.8 mm Ti–6Al–4V alloy was carried out using different rotating speeds. Effect of tool rotating speed on defect, phase transformation, and mechanical properties of the joints was mainly discussed. Results show that void defect at the joint bottom can be eliminated by decreasing the rotating speed. Microstructure shows difference along thickness due to big temperature gradient. Hardness values of the joints are higher than the base material and bigger hardness values can be obtained using low rotating speed. Lap shear properties of the joints when the retreating sides (RS) of the upper sheets bear the main loads (configuration B) are higher than those of the joints when the advancing sides (AS) of the upper sheets bear the main loads (configuration A). The maximum failure load of 19.08 KN is attained using 150 rpm and configuration B. Shear fracture mode and tensile fracture mode can be obtained during the lap shear test.

Description: Despite the importance of the polyphthalamide (PPA) composites in many industrial applications, especially for automotive industry, very little is known about the machinability of these composites. This paper presents the drilling characteristics of PPA matrix composite materials having glass fiber of 30 % reinforced by using HSS, TiN-coated HSS, and carbide drills. The influence of cutting parameters, for example cutting speed and feed rate, on the delamination factor and surface roughness of the composites has been examined during the drilling operations. Experimental results have demonstrated that as cutting speed increases, surface roughness decreases, and as feed rate increases, surface roughness increases as well. Higher cutting speeds and lower feed rates generate better surface quality. The drilling test results have demonstrated that the delamination factor increases through the increase of feed rate and decreases through the increase of cutting speed. It is obtained the best results of the delamination factor at higher cutting speeds and lower feed rates. The machined surface is examined by means of scanning electron microscopy (SEM). SEM images of the machined surfaces show the presence of cracks, fiber pullout, and shearing of fibers.

Description: In order to shorten the preparation period, dieless shear spinning is widely used in various industrial fields with advantage of economy of materials and easy control. Controlling roller path is one of the main methods for changing thickness distribution. A new discretization method is proposed by theoretical derivation in dieless shear spinning. It will generate a virtual axis by inclining the flange of the workpiece. And, the roller path is derived for spinning machine combined with the sine law in shear spinning. The derived path should be applied after the range of forming reaches the certain height. The thickness distribution of formed workpiece is basically in agreement with the theoretical value. It also illustrates that roller nose radius and axial feed will influence the surface quality.

Description: Investigation of friction is carried out in the radial drawing region between the die and blank holder and also in the stretching zone over the punch in deep drawing. Two methods are developed to calculate the coefficient of friction in each zone using the experimentally determined data such as punch force diagrams and strain distributions obtained by an optical scanning system. The current methods differ from the existing techniques which are obtained in simulative tests. The proposed methods can be applied in room temperature and at elevated temperatures. Comparisons of friction coefficients are made with those obtained by other techniques.

Description: Surface grinding is always accompanied with chatter due to self-excited vibration. It often leads to an unexpected impact on the quality of the workpiece’s topography. However, the chatter is regarded as a harmonic vibration in most topography researches. This may lose preciseness when the relative vibration and the abrasive trajectory are taken into consideration. In order to study the relationship between the system’s dynamic characteristic and the workpiece’s topography, a two-DOF (degree of freedom) dynamic model with time-delay characteristic is established accordingly. Then, reliability analysis is introduced into chatter vibration by analyzing the fluctuations of dynamic parameters with two analysis methods, namely Monte Carlo (MC) and first-order second-moment (FOSM). With the above two reliability analysis methods, the calculations are carried out as follows: firstly, the non-Gaussian distribution of the grinding wheel based on Johnson Curves and filter techniques is established. Secondly, the results of the dynamic analysis are coupled into the grain trajectory equation. Thirdly, the influence of the wheel grinding parameters and dynamic parameters on the surface height is discussed by coupling the dynamic characteristics into the simulation model. Finally, the simulations and experiments are carried out on the impact of different feeding rates and sections on the workpiece to the surface heights. The comparisons verify the prediction of the simulation model. The obtained conclusions could be applied to optimize the workpiece’s topography by regulating the grinding parameters and dynamic parameters to weaken the chatter’s influence.

Description: A new method of adaptive movement control of guide and conical rolls is proposed in three-dimension finite element (3D FE) simulation of ring rolling. The movement mathematical models of guide and conical rolls are established with combining with the node track method in an FE model. By means of the user subroutine VUAMP interface of ABAQUS, an adaptive roll motion subroutine is written by FORTRAN software, which carried out the adaptive movement control of guide and conical rolls. The simulation results show that the ring can always keep a good circular degree and ensure final deformation quality in ring rolling process. The effectiveness of FE simulation has been verified by practical experiments. It overcomes some shortcomings of the traditional method, such as the large amount of computation, low universality, ubiquitous error, time consuming, and lack of universality and so on. And, it guarantees the balance of ring rolling and the roundness of the rolled ring.

Description: Formability of aluminum alloys at elevated temperatures are of vital importance to process design and numerical simulation of aluminum hot stamping. In this paper, the hot formability of AA7075 was investigated experimentally and numerically. Firstly, a series of hot uniaxial tensile tests were performed on a Gleeble 3500 thermomechanical simulator to determine constitutive relationships of AA7075 at different temperatures and strain rates. Based on these results, a uniaxial damage model was established, and further extended to a multi-axial continuum damage mechanics (CDM) based model with the consideration of stress state and strain path effects for hot stamping. Good agreement between model fitting and experimental results was achieved. Secondly, hot formability tests were conducted to investigate deformation characteristics at elevated temperatures. Finally, a finite element (FE) model using software ABAQUS with implemented the CDM model via subroutine was established and validated by corresponding experimentations. The developed FE model was utilized to investigate effects of process variables on material deformation and damage evolution in detail. It was found that formability can be improved with decreasing forming temperature and increasing forming speed. In addition, friction has a dominant effect on determining failure location.

Description: Positioning accuracy of chip directly impacts on the quality and efficiency of LED chip production. The purpose of this paper is to improve the chip positioning accuracy by improving the camera calibration algorithm of LED chip visual positioning system. Firstly, by making the error analysis for the visual positioning system, the systematic errors of each parts of the system are obtained, and the relationship between chip positioning error and chip position distribution in image is found. Then, according to the result of error analysis and the characteristics of the chip positioning process, an improved calibration algorithm is proposed to improve the chip positioning accuracy. This improved algorithm solves the calibration parameters in two steps, which highlights the main cause of errors in calibration process and meets the requirements of chip positioning. Finally, the experiment results show that the proposed algorithm can improve the chip positioning accuracy obviously, and has good stability and robustness.

Description: Due to its excellent mechanical strength and corrosion resistance at high temperatures, Inconel 718 alloy has several applications in the aerospace and nuclear industries. This austenitic material promotes rapid hardening by self-hardening during machining, and its low thermal conductivity leads to high temperature in the cutting zone. As heat increases, cutting tool wear accelerates, compromising the final quality of the machined workpiece. These factors lead to Inconel 718’s difficult machinability and influence the presence of surface residual stresses due to thermal and mechanical loads during machining. To address a knowledge gap pertaining to Inconel 718 end milling, this study conducts a series of experiments to gather a set of important results. The optimum cutting speed is calculated by high-efficiency range analysis using the conventional flood method; then, this calculated speed was adopted in the minimum quantity lubrication (MQL) experiments, and the results of the two methods were compared. For the same cutting conditions, the cutting fluid method did not influence the cutting force and surface hardness results, which remained constant along the cutting length. In the MQL application mode, the flow rate influenced tool wear, which was greater than for the flood mode throughout the cutting length. The flood method resulted in improved residual stresses in the longitudinal and transverse directions when compared with MQL, obtaining compressive residual stresses for longer cutting lengths. Surface roughness values were similar for the two lubrication methods up to 50 mm, from which the flood method values increase. Based on the results, the flood mode was found to be the preferred method for milling Inconel 718. Graphical abstract ᅟ

Description: Some anti-reflection structures can be fabricated on the surface of high-efficiency silicon solar cells. The anti-reflection efficiency can be increased and hence the photoelectric conversion efficiency can be increased. The effects of varied anti-reflection structure are altered on the optical reflectance. The forward stochastic pyramid structure can be fabricated mechanically. Before processing the pyramid structure, a unidirectional V-groove array must be fabricated firstly. The research content of this paper was based on our previous researches. The fabrication of V-groove with different depth on the surface of silicon wafers was explored. Micro-milling tool constituted by cemented carbide was used. The quality of completed V-grooves was measured and analyzed. Then the effect of the structure for the reflectance was evaluated. The calculated reflectance of accomplished V-grooves was compared with that of the theoretical model. A satisfactory value was obtained by contrast with existing technologies. Furthermore, the tools were observed after the processing, to evaluate the tool wear. Results indicated that processing the pyramid structure using the micro-milling tool is feasible.

Description: In micro-EDM milling, real-time electrode wear compensation based on tool wear per discharge (TWD) estimation permits the direct control of the position of the tool electrode frontal surface. However, TWD estimation errors will cause errors on the tool electrode axial depth. A simulation tool is developed to determine the effects of errors in the initial estimation of TWD and its propagation effect with respect to the error on the depth of the cavity generated. Simulations were applied to micro-EDM milling of a slot of 5000-μm length and 50-μm depth and validated through slot milling experiments performed on a micro-EDM machine. Simulations and experimental results were found to be in good agreement, showing the effect of error amplification through the cavity depth.

Description: In extrusion industry, optimization of die design plays a critical role in contributing to the quality of the extruded profile as well as tooling life. This study addresses the fact that most dies today are typically designed following a trial and error approach based on empirical knowledge of the designer, which inevitably results in increasing scrap rate and cost. The purpose is to understand the effects of geometry on the performance of a porthole die in order to improve the life of tooling and quality of the final extruded shape using finite element based simulations. In this work, a finite element (FE) model is developed to simulate the extrusion of a commercial grade aluminum alloy to produce a condenser tube used for cooling systems. Using the Update Lagrange FE analysis first, the tooling components of the modular die are assumed to be rigid in order to achieve the right friction coefficients to validate the experimental data collected during trail runs of the modular die. Next, DOE is used to identify the relative influence of the three main parameters that control the geometry of the mandrel. For each parametric set, a steady-state FE analysis is run to predict the maximum weld pressure between the mandrel port webs. The insight gained from these simulations is used to optimize the mandrel geometry.

Description: Part 2 of this work looks at the simulation for the accurate control of multiple machine processes made on a machining centre. Specifically the models are based on controlling against two grinding anomalies; grinding burn and chatter, and for hole making; drilling tool wear and the onset of drill tool malfunction, which is also significant to severe scoring and material dragging. The work developed here takes the ideas of part 1 further where intelligent control based on the identification of force and accelerations in z axis time-frequency domain is applied. This work is significant to automated manufacturing, where observed anomalies significant to surfaces quality cannot be accepted and play an integral part to flexible automated manufacturing systems. The simulation models displayed in this part can easily be realised into prototype embedment promoting real-time control against unwanted surface anomalies for multiple machine processes.

Description: The z -axis motion platform is an important part of micro v-groove machine tools. A v-groove structure is the most important basic component of fiber array, dense wavelength division multiplexing device, fiber optic splitter, planar lightwave circuit, and so on. The core pitch of v-groove structure which determines the quality of micro v-groove is the most important machining parameter. Its machining precision is mostly dominated by the compensation accuracy of geometric error in the z -axis direction. The precise geometric error model of z -axis motion platform is the basis and key of precision compensation of geometric error. It is very difficult to calculate the precise geometric error with the traditional modeling method. A new modeling method of geometric error is proposed based on the z -axis motion platform of micro v-groove machine tools. The difference between the simultaneously events and the successively events is intuitively explained by comparing the new modeling method and the traditional modeling method. The results show that the new modeling method of geometric error based on the z -axis motion platform is effective and practical.

Description: In this research work, carbon nanotube (CNT)-reinforced Al 2 O 3 coatings were prepared and successfully deposited on ASME-SA213-T11 boiler tube steel. Coatings were deposited by the plasma spray process. Ni-Cr was also used as a bond coat before applying CNTs-Al 2 O 3 coatings. The coatings were subjected to metallography, XRD, SEM/EDAX, and X-ray mapping analysis. The porosity of CNT-Al 2 O 3 mixed coatings was decreasing with increase in CNT content. The CNTs were found to be uniformly distributed within the Al 2 O 3 matrix. The CNTs were chemically stable during the spray forming. It did not react to form oxides or aluminum carbides even at the very high processing temperature.

Description: This paper presents an innovative process for the fabrication of a high fill factor microlens array using thermal reflow and repeating spin coating. The repeated spin coating method creates a hexagonal microlens array after the thermal reflow processes as an alternative to the expensive gray-mask and longtime electroplating method. The first, the round base and hexagonally arranged array, precisely define the bottom shape of the liquid photoresist, and a tall hemispherical microlens array with a small radius of curvature is fabricated during the photoresist thermal reflow process. The second, the surplus photoresist, is then rotated at high velocity using a spinner. The micro-plano-convex microlens molds are then finished. The polydimethylsiloxane (PDMS) microlens array is fabricated using a replica molding process. The experimental results show that a high fill factor hexagonal PDMS microlens array is successfully fabricated. The fabricated microlens array has good surface roughness. The proposed fabrication method facilitates mass production and gives increased luminance efficiency and luminance power efficiency to produce a high fill factor microlens array that is suitable for use in the light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs).

Description: Electron beam melting (EBM), an additive method and rotary ultrasonic machining (RUM), a subtractive technique have been in great demand owing to their innumerable benefits. These techniques can manufacture components from titanium alloys (such as Ti-6Al-4 V) for industries such as aerospace, medical, and automotive, etc. However, these techniques have their own limitations since they are not yet fully developed for many materials including Ti-6Al-4 V. For example, the RUM involves high machining time due to the extremely low MRR while EBM suffers with poor surface quality of final parts. Therefore, in this work, an attempt has been made to combine the additive (EBM) and subtractive (RUM) techniques. The two techniques have been integrated to overcome the limitations of one over the other. In fact, this research has aimed to minimize the surface roughness of EBM fabricated parts using RUM. The design of experiment (DOE) has been adopted to get the best combination of RUM parameters which produce a high surface finish for EBM parts. Moreover, the artificial neural network (ANN) model has been developed to predict the surface roughness effectively. The machining parameters such as coolant pressure, frequency, spindle speed, depth of cut, feed rate, and power supply of RUM have been investigated for better surface finish. It has been confirmed from this study that the surfaces with R a value less than 0.3 μm can be achieved using the proposed methodology.

Description: The development of several novel multifunctional components to perform specific unique functions is directed towards meeting the demands for advanced components in industries. In this study, the role played by carbon (C gr ) variation on the steel part composition of cemented tungsten carbide and steel bilayer processed via powder metallurgy was investigated. Microstructural examination through field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) revealed the presence of detrimental eta carbide phase (M 6 C) distributed across the interface of sintered bilayer compacts. A significant reduction of M 6 C was observed with 0.8 wt.% C gr when interlayer diffusion was accelerated resulting in better morphology and higher hardness values of 735.70 and 150.97 kgf mm −2 in WC and Fe layers, respectively. Tensile strength property was evaluated to examine the sintering compatibility and the interfacial bond strength of bilayer specimens. Excellent bond strength was achieved in all sintered bilayer with increasing C gr level and enhanced densification which consequently improved tensile strength by 19%.

Description: In order to improve welding quality and welding efficiency of the rectangular fillet weld in the shipbuilding industry, it is necessary to identify the space posture of the arc welding gun accurately. The mathematical model of the space posture of the arc welding gun has been established, and the space posture can be determined by four variables. Within a certain range, the mathematical model about the relationship between the welding current and the wire extension has been established in GMAW, and the height deviation that the arc welding gun is relative to fillet weld can be calculated by this mathematical model. In order to accurately calculate the horizontal deviation and the inclination angle, the main analysis method has been studied. By using the designed algorithm, the rectangular fillet weld tracking experiment and the tensile experiment have been done in the laboratory and shipyard. Experimental results showed that the robot could identify the space posture of the arc welding gun accurately, and track rectangular fillet welds with high accuracy and good reliability.

Description: In this study, micro-scale textures with a single linear groove parallel to cutting edge are fabricated on the rake face of the WC/Co cemented carbide tools. Dry cutting tests on medium carbon steels (AISI 1045 steels) are carried out with this rake-face textured tool (TT) and a conventional carbide tool (CT). Results show that derivative cutting, i.e., the additional cutting to the bottom side of the chip with the micro-surface textures on the tool surface, occurred in dry cutting of medium carbon steels with the micro-textured tools. Derivative cutting always causes the filling of chip in the surface textures, which leads to the increase of friction at the tool-chip interface, cutting forces, and hardness and deformation of chip. The texture edge far from the main cutting edge is engaged in the derivative cutting as a cutting edge; wear of this texture edge results in a greater negative rake angle, which is found to be beneficial to alleviating the derivative cutting.

Description: The sidewalls of thin-walled deep cavity components can easily deform during the milling process because of their low rigidity, which seriously affects the machining accuracy. To resolve this problem, this paper proposes a novel method to predict milling errors based on the finite element method (FEM). A dynamic model of the tool is first established, and the motion state of an arbitrary point on the tool during the continuous milling process is obtained by solving for the key parameters. In addition, both the deflection of the workpiece/tool system and the springback deformation of the workpiece are considered. The material is then removed based on a Boolean operation and a hexahedral mapping algorithm for the points; finally, the continuous tooling process and the milling error of the arbitrary point on the finished surface are obtained. This study uses a typical waveguide cover as the simulation object and verifies the veracity of the simulation method through experiments.

Description: Tool performance while machining aluminum-based metal matrix composites has been investigated by developing finite element models based on particle size and volume fraction of the workpiece. Two types of finite element models are developed, i.e., with and without cohesive elements. The effects of varying cutting speed, feed rate, volume fraction, and size of reinforcement particles on tool performance are investigated using both models. It has been found that models without cohesive zone element can predict cutting forces, tool stresses, and temperatures to a reasonable degree of accuracy. The increase in tool stresses and temperatures due to cutting speeds, feed rate, particle size, and volume fraction can be visualized with these models. Models based on cohesive elements can predict localized effect of particle debonding and failure on tool stresses and machined surface. It has been noticed that increase in particle size and cutting speed increases the effects of particle rolling and sliding on the tool face due to increase in kinetic energy resulting in high wear.

Description: Due to their good mechanical and technological performances, thin substrate-supported metal layers are increasingly used as functional components in flexible electronic devices. Consequently, the prediction of necking, and the associated limit strains, for such components is of major academic and industrial importance. The current contribution aims to numerically investigate the respective and combined effects of strain rate sensitivity of the metal layer and the addition of an elastomer layer on localized necking in substrate-supported metal layers. To this end, strain rate-dependent forms for the flow theory of plasticity and the deformation theory counterpart are used to describe the mechanical behavior of the metal layer. As to the substrate layer, it is made of elastomer material whose mechanical response is described by a neo-Hookean hyperelastic model. The two layers are assumed to be perfectly adhered. Necking limit strains are predicted by the Marciniak–Kuczynski (M–K) imperfection approach. Various numerical results, corresponding to freestanding metal layers as well as substrate-supported metal layers, are presented and extensively discussed in this paper. The significant effect of strain rate sensitivity on the retardation of localized necking is first emphasized. Then, the combined and positive influence of strain rate sensitivity of the metal layer and characteristics of the elastomer layer (thickness and stiffness) on the enhancement of the ductility of the whole bilayer is analyzed and discussed.

Description: Nowadays, the widespread use of resistance spot welding (RSW) in various industries is evidence for the importance of this manufacturing process. In this paper, the finite element method (FEM) is utilized to model the weld nugget geometry and tensile-shear strength in RSW process of the galvanized interstitial free (IF) and bake hardenable (BH) steel sheets. Computational results have good agreement with experimental data. The investigation of input parameters influence, namely welding current, welding time, and electrode force on nugget size variations reveals that welding current is the most influential parameter. The examination of input parameters interaction on joint strength indicates that increase in welding current and time and also reduction in electrode force result in larger nugget size and bigger joint strength. Although by increasing the nugget size, at first, the joint strength is raised, after reaching the maximum strength, increase in nugget size results in decreasing the joint strength, and it may lead to expulsion phenomenon. The analysis of variance (ANOVA) results of response surface methodology (RSM) modeling demonstrate that beside the welding parameters, their interactions have significant effect on nugget geometry and tensile-shear strength. The relative error between RSM predicted and FEM calculated maximum strength is attained about 3% that specifies the efficiency of RSM.

Description: Automated production lines with high productivity are represented the complex and expensive systems based on mechanical, electric and electronic units, while predicting the efficiency of the automated lines is an important analytical task. Calculating the productivity rate of the automated production serial line (APSL) segmented on sections with embedded buffers of limited capacity is a complex and crucial problem for manufacturers. The productivity rate of APSL with balanced technological processes depends on the reliability of mechanism, workstations, transport and other units. Balancing the machining time leads to an increase in the number of workstations and in productivity rate of APSL. It also leads to an increase in the failure rates and hence to deceasing in the productivity rate of the production line. Solution for enhancing productivity is presented in terms of segmenting of APSL into sections with embedded buffers. This paper represents an analytical solution for the productivity rate of APSL segmented on sections with embedded buffers of limited capacity. The mathematical model for the productivity rate of APSL is derived as a function of the technological parameters, the capacity of the buffers and the number of stations and sections with different failure rates and cycle times.

Description: Liquid silicone rubber (LSR) is a family of high-technology elastomer materials. The member of this family has been identified as being very promising for development in the coming decades due to their unique properties and ease of generation in large series by the injection moulding process. In particular, the over-moulding of LSR on other materials, such as thermoplastic polymers, metals and ceramics, is possible today, which leads to the possibility of obtaining multi-material, functional multi-colour and newly featured components. The work presented in this paper focuses on the transformation of liquid silicone rubber to better understand the phenomena involved to improve production processes and to optimize the processing conditions for bi-material components in well-defined geometry and functional properties. The rheological, rheo-kinetic and thermal behaviours of silicone elastomers were investigated and characterized under real conditions of manufacture with different combined methods. A thermo-rheo-kinetic model was then developed and implemented using the moulding simulation software Cadmould ® 3D to simulate two-component injection moulding of silicone rubber into a thermoplastic polymer. For the validation of the models chosen and the parameters identified, bi-material injection moulding tests of a two-component standard peel test specimen (polyamide thermoplastic polymer/liquid silicone rubber) were performed and compared to numerical results.

Description: Refill friction stir spot welding (RFSSW) has been used to weld 6061-T6 aluminum alloy, and keyhole free joints were successfully obtained. Effect of tool rotation speed on microstructure and mechanical properties of joint was investigated. The joint was divided into four zones, i.e., the base material (BM), heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and stir zone (SZ) according to microstructural evolution. Defect was not found on the surface of welded joint, but inner defects of partial bonding, bonding ligament, hook, and voids were observed within the welded joint. The microhardness of HAZ and TMAZ was lower than that of the BM, while the maximum microhardness was obtained in the SZ of welded joints. With increasing tool rotation speed from 1100 to 1700 rpm, microhardness decreased with increasing grain size in the weld. The maximum tensile shear failure load of 7522 N was obtained for the joint under tool rotation speed of 1500 rpm. Two different failure modes of plug fracture and tensile-shear mixed fracture were observed during the tensile shear tests.

Description: Different from material removal mechanism in metals, the main form of material removal of ceramics is brittle fracture removal. Previous studies on fracture mechanics for brittle materials basically do not involve cutting temperature, and only static crack systems are discussed, without considering the kinetic energy of crack extension; however, in real turning processes, the problem of crack extension is within the domain of dynamic fracture mechanics. Therefore, kinetic energy is considered in energy balance equations. The work of cutting force is converted into surface energy, strain energy, kinetic energy and heat energy. According to the law on the conservation of energy in fracture process, the theoretical equation of cutting temperature for brittle materials in turning is established. Then, turning experiments on fluorophlogopite ceramics are conducted to verify the applicability of the theoretical equation. The theoretical values of metal model, ceramic model and experimental values are compared. Results show that the theoretical value of metal model has a very large deviation when used to predict the cutting temperature of ceramics; whereas, the theoretical value of ceramic model is basically with the same changing tendency as the experimental value. This indicates that the established theoretical equation is practical.

Description: Solving problems of stress-strain analysis in plastic deformation processes can be carried out by many methods. Almost all solutions can be reduced to an analysis of theoretical and experimental results, obtained by some mathematical models as well as by experimental testing of the plastic deforming process. The ultimate goal is to determine the stress-strain state, the field of strain rate, and deformation velocity within the volume of the material that is being plastically deformed. The aim of this investigation is to determine the parameters given earlier by tracing the grain structure microdeformations of a low carbon steel in a meridian cross section at ambient temperature by means of an artificial neural network (ANN) during bulk forming. The three key parameters selected for the description of the deformed microstructure are the angle of rotation and the major and the minor axes of the ideal grain, which are used to represent the plastic deformation in a selected point. The ideal grain model, for the selected point of the meridian cross section, represents the plastic deformation in line with the selected parameters for the defined number of ferrite grains. The ANN models were developed using steel microstructure data, which were obtained experimentally by using three experimental tool dies for forward extrusion. Their verification was carried out on three different angles of extrusion. This method yielded the size of the plastic deformation of the grain structure in the meridian cross section during forward extrusion, which can serve as a basis for further stress-strain analysis.

Description: Cam mechanism is the most difficult part in the design and manufacture of stamping dies of automobile panels. The same series of cam products need to meet the needs of different working angles. Each specification needs to design and prepare a three-dimensional model, which brings great challenges to the design, editing, and management of the models. Therefore, a new design system of full parametric association modeling based on geometric features for standard cam was proposed, which is seamlessly integrated in NX software platform. The models of different work angles of the same series of cam are integrated into a fully parametric model. The specification and assembly location of standard parts, activation and suppression of detail features will automatically change with work angle based on parametric feature and association constraint technique. By modifying the work angle, the system can automatically instantiate different specification models of cam. Furthermore, the optimized design of cam structural is easier to achieve by motion simulation and finite element analysis based on the parametric model and geometric features. The system can also output the BOM table, when the model is instantiated. The cam of KMACG 600 demonstrates that the newly developed system shows an excellent performance on the model simplification, data management, and optimization design of cam, which can generate high quality design and reduce cost and designing time significantly.

Description: Avoiding significant fluctuations of tool orientation is an important problem in five-axis machining. The dramatic change of tool orientation may greatly increase the angular acceleration of machine rotary axes, produce larger nonlinear machining errors and gouging, reduce the feed rate of machine rotary axes, etc. In this paper, we propose a tool orientation smoothing method based on machine rotary axes for five-axis machining with ball end cutters to reduce fluctuations of tool orientation in the machine coordinate system (MCS). The core idea of the proposed method is to directly smooth machine rotary angles in the machine coordinate system for the smooth variation of tool orientation. First of all, we establish the relationship between the design variables of tool position and machine rotary angles. Then, we define an objective function of tool orientation smoothing based on machine rotary angles. In order to solve the above objective function, we also develop a simplified algorithm to obtain the minimum sum of squares of compound angular accelerations. Finally, a blade surface is used as a test example, and tool paths are generated by the Sturz and proposed methods, respectively. Comparison and analysis results show that the proposed method can improve the kinematics performance of five-axis machine tool, as well as surface machining quality and efficiency.

Description: One of the most significant issues investigated in reverse engineering (RE) is the problem of finding the best surface that approximates point cloud data. In recent years, some studies have been carried out for the segmentation of industrial mesh models into primitive surfaces and simple kinematic surfaces such as revolved and extruded surfaces. But, with regard to the swept surfaces that are widely used in CAD models, most researches just investigated how to extract the generative curves and few researches investigated the segmentation of CAD model into swept surfaces. In this paper, regarding the importance of swept surfaces in the fields of computer design, RE, and tool path planning in CAM software, a method to find the swept surfaces by arbitrary central and profile curves is introduced. To this end, with the help of variational segmentation algorithm, and regarding slippable motion as a segmentation criterion, data points are segmented into regions that could be approximated by extruded surface. Then, an effective algorithm is proposed through which, by employing the concept of hierarchical classification and defining the dual graph of the segmented subregions, swept surface regions may be found. The introduced method is capable of recognizing other surfaces such as blend, extruded and revolved surfaces as well. To validate the proposed algorithm, it is implemented in several models with different conditions and various noise levels. It is observed that the results have good agreement with real model condition, which shows the efficiency of this method in finding the swept surface.

Description: Methods of economical alloying of high pipe steels were considered in the paper. Due to the large environmental, energy, and economic issues in the destruction of the pipeline, the quality of steel pipes is very important. The method described in this article is considered to be relevant not only for pipe steels but also for high-strength steels used in shipbuilding, bridge construction, etc. Review mechanisms of strengthening microalloyed steels were carried out in this work. Schema evolution of the microstructure of microalloyed steels was discussed. The influence of alloying elements in steel by means of optimal process parameters of thermomechanical rolling was analyzed. There are two methods of mathematical modeling used in the study: artificial neural networks (ANNs) which are based on the multilayered perceptron to select the optimal chemical composition and finite element analysis to optimize the process parameters. An experimental dataset was used to train multilayer perceptron (MLP) networks to allow for prediction of the yield strength, tensile strength, and elongation of steel. Due to large availability, low cost, and high accuracy of the results, these methods are considered to be the most promising ones. The mathematical model for calculating mechanical properties of a rolling pipe has been developed. Two ways to reduce the cost of a hot-rolled plate made of microalloyed steels were developed. There has been developed the complex of replacement technological impact which can make it possible to replace or reduce the amount of expensive chemical elements (vanadium, nickel, copper, manganese, chromium, and niobium) without loss of quality.

Description: Superduplex stainless steels (SDSS) are used to manufacture components in the oil and gas extraction industries. Machining of SDSS is difficult due to both built-up edge (BUE) formation on cutting tool surface at relatively low cutting speeds and rapid tool wear at higher cutting speeds caused by high strength and work hardening. Appropriate coating systems on cemented carbide tools (WC-Co) are crucial for adequate process performance, as well as SDSS/coated WC-Co tribological pair characterization. In this work, three types of coatings with chemical composition (at %) Al 50 Cr 50 N, Al 60 Cr 40 N, and Al 50 Cr 50 N/Ti 95 Si 5 N were deposited, by physical vapor deposition (PVD), on cemented carbide substrate. After, characterization was performed through X-ray diffraction (XRD), SEM, nanoindentation, tribological tests, and surface roughness. The results showed that SDSS prevailing wear mechanism was adhesion for all coatings investigated. Wear rate and friction coefficient are associated to coating chemical composition; Al 50 Cr 50 N/Ti 95 Si 5 N coating system presented the lowest interaction with SDSS, resulting in the lower friction coefficient and, consequently, reduced specific wear rate.

Description: This work presents the experimental assessment of a facile and effective method for polymer welding. The setup includes a 20-cm-diameter clear crystal sphere that concentrates solar energy onto an infinitesimally small point (0.8 mm). The motion of this focal point performs the welding operation, which is controlled with good precision by a computer-numerical control (CNC) machine that lays the path and executes it. An x-y-z platform follows the desired programmed trajectory to weld the workpiece that consists of two thin sheets of polymers, one transparent and the other opaque to be joined by transmission welding. The welding process is investigated at different speeds to determine the optimum traverse rate and focal point energy density combination for a strong weld with minimal thermal damage to the substrates. The samples are studied under the microscope, and the welding strength is determined by tensile test to establish the feasibility of the process.

Description: This paper presents a new method for tool wear estimation in milling process by utilizing the hidden semi-Markov model (HSMM). HSMM differs greatly from the standard hidden Markov model (HMM) in state duration distribution. The model structure and corresponding parameters of HSMM can be easily determined without optimization. Two groups of experiments are carried out to prove the effectiveness of the HSMM-based method by recurring to the Gamma distribution. Five types of time-domain features that characterize tool wear states are extracted from the cutting force signals during milling process. The extracted signal features are utilized to realize tool wear estimation by means of HSMM and some other published methods, respectively. The experimental and analytical results show that the HSMM-based method can reach higher accuracy for tool wear estimation. Besides, the consuming time of HSMM for the identification of tool wear state is less than 0.05 s, which makes tool wear monitoring in industrial environment become more realistic and operable.

Description: During high-speed hard turning, the cutting edge of the insert is directly responsible for cutting and bears high magnitudes of force and thermal load, etc. The geometric structure of the edge directly affects the cutting performance of the tool and the surface quality of the workpiece. In this study, the chip morphology, cutting force, and the surface topography have been compared and analyzed by PCBN cutting tool with the sine-strengthened edge and the negative chamfered arc edge through the method of experiment. It was found that the lamellar width of the chip produced by the sine-strengthened edge is smaller. Therefore, it has a smaller cutting deformation when compared to the chip with arc edge. Moreover, there are significant differences in shape of both its lateral burrs. The sine-strengthened edge can reduce the cutting force of the tool, and the ratio between radial and tangential force is smaller, resulting in significantly better cutting performance than the tool with arc edge. Compared to a negative chamfered arc edge tool, the machined surface produced by the sine-strengthen edge close to zero kurtosis and lower Sa value, and it can obtain a better machined surface quality.

Description: A highly immersive and interactive virtual environment was constructed as an experimentation platform for human–robot collaboration in constricting panels from preimpregnated carbon fibre fabrics. The application involves highly collaborative tasks such as handover, removal of adhesive backing strip and fabric layup in a mould. Furthermore, the user is expected to be most of the time within the robot’s workspace, jointly working as teammates on collaborative manufacturing tasks. The environment embeds two interaction metaphors for complex tasks and advocates use of cognitive aids to cultivate proactive behaviour of the user, thus promoting situation awareness, danger perception and enrichment of communication between human and robot. The application was put under test by a group of users. Their experience was registered scholarly through questionnaires and objective observation and is reported in the paper to explore the effectiveness and acceptability of such an environment. Overall, the application was judged positively, especially the use of cognitive aids which, under circumstances turned into alarms and readily provided mental association of collision danger to its cause. Furthermore, some deficiencies were identified pertaining to lack of hand-tracking performance and need to improve the layup metaphor.

Description: Plunge milling is an efficient machining process for roughing deep pockets. Its efficiency is mainly due to low radial forces on the cutter. This leads to reduced bendings and vibrations that allow one to improve cutting parameter values. The machining time can then be reduced with respect to machining processes with constant Z -level. Recently, another machining process has been introduced, called ”balancing of the transversal cutting force” (BotTCF), that is also characterized by a suitable distribution of forces on the cutter. It has been applied only to finishing operations on complex surfaces. In this paper, we present two main contributions. First, we extend the BotTCF concept to roughing open deep pockets and semi-open pockets opened from side to side. This is mainly based on successive parallel ramping trajectories, defined by an optimal angle which ensures a good balancing of the transversal cutting forces. This can be applied to 3-axis and 5-axis computer numerical control (CNC) machine tools. Second, we propose a new, hybrid methodology for roughing semi-open pockets (not opened from side to side) and closed pockets. It is based on the combination of ramping trajectories with BotTCF and plunge milling. The proposed methodology is developed for three-axis machining and can be extended to five-axis machining. Based on an identical criterion (identical maximum force acting on the cutters), we perform a fair machining-time comparison of plunge milling with the proposed hybrid method applied on a closed deep pocket: a simplified aeronautical housing made of magnesium-rare earth alloy. Results show a significant gain in machining time when the hybrid method is applied.

Description: The addition of a cold wire in conventional tandem submerged arc welding (TSAW), i.e., the CWTSAW process, is proposed to improve the productivity of pipeline manufacturing by increasing welding travel speed and deposition rate, while retaining adequate joint geometry without increasing the welding heat input. In addition to increasing productivity, incorporating a cold wire in the TSAW process improves the fracture toughness by refining the microstructure of the weld heat-affected zone (HAZ). In the present work, the influence of cold-wire addition on the heat input, productivity and properties of an X70 microalloyed steel welded by CWTSAW is investigated. Charpy impact testing and microhardness testing were utilized to investigate the mechanical properties of the HAZ. Scanning electron microscopy (SEM) and tint etching optical microscopy (TEOM) were used to correlate the microstructure alterations with the properties. The low-temperature fracture toughness of the HAZ was improved by 38% when a cold wire was fed at 25.4 cm/min in the conventional TSAW process with a heat input of 22.1 kJ/cm. This improvement was attributed to a reduction in the prior austenite grain (PAG) size and martensite-austenite (M-A) constituent fraction as a result of the reduction in the effective heat input (7.5% reduction) by cold wire addition. The amount of heat input reduction is a function of the cold wire addition rate and the nominal welding heat input. The increase in travel speed and deposition rate of welding by addition of a cold wire at 58 cm/min in the TSAW process with a heat input of 23.2 kJ/cm was 26 and 12%, respectively.

Description: This is the second of two papers by the authors associated with materials characterisation methods based on hardness testing. It is important to have knowledge of the tip geometry of the indenter employed in the hardness test as this affects the correctness of the value of contact area parameter used to determine the mechanical properties. In this paper, outcomes of a study concerned with the tip geometry of the Vickers microindenter are presented. Results from experiment are compared with results from published works and the most current accepted analytical models. A new non-contact methodology based on a residual imprint imaging process is developed and further compared with other methods using experimental and numerical analyses over a wide range of material properties. For confirmation, an assessment was undertaken using numerical dimensional analysis which permitted a large range of materials to be explored. It is shown that the proposed method is more accurate compared with other methods regardless of the mechanical properties of the material. The outcomes demonstrate that measuring contact area with the new method enhanced the overall relative error in the resulting mechanical properties including hardness and Young’s modulus of elasticity. It is also shown that the value of the contact area using actual indenter geometry obtained from experimental load-displacement analysis or FEM numerical analysis is more accurate than the value obtained from the assumption of perfect indenter geometry and hence can be used for materials with low strain hardening property.

Description: In this paper, an automatic recognition system of welding seam type based on support vector machine (SVM) method is presented. The hardware of the proposed system consists of an industry robot with six degrees of freedom, a vision sensor, and a computer. The system has two parts including input feature vector computation and model building. In the input feature vector computation part, the depth values of a series of points of the welding joint are taken as feature vector, which are determined by four steps including main line extraction of the laser stripe, normalization of the laser stripe, selection of the left and right edge points of the welding joint, and normalization of feature vectors. In the model building part, SVM-based modeling method is used to achieve welding seam type recognition. At first, RBF kernel function is employed for classification of welding seam types. Then, the parameters of RBF are determined by a grid search method using cross-validation. After the optimal parameters of RBF being determined, the SVM model is built, and it could be used to predict welding seam type. Finally, a series of welding seam type recognition experiments are implemented. Experimental results show that the proposed system can achieve welding seam type recognition accurately and the computation cost can be reduced compared with previous methods.

Description: Severe distortion often occurs during the production of thick Invar alloy mold using the multi-layer and multi-pass welding method. However, welding angular distortion and residual stress can be reduced greatly with the backward deformation method. The present paper is aimed at researching the appropriate backward deformation for thick Invar alloy welding, using commercial finite element software, MSC.Marc. The transition density grid meshing method was applied in this work. Besides, the double-ellipsoid distribution was employed as the heat source model. Welding process with different backward deformation was simulated. And the simulated angular distortion was compared with actual residual deformation. Both the simulated and experimental results indicated that the welding deformation of Invar alloy samples was efficiently controlled with reserved angle of two degrees. Furthermore, it was proven that the numerical simulation results were in good agreement with the experimental results.

Description: The hole series parts is widely used in the aerospace, automotive electronics, instrumentation, and hydraulic components. There are many of holes with the same machining parameter in this kind of parts, the consistency evaluation of these hole surface quality is one of the most important considerations. Based on wavelet packet energy spectrum, higher-order statistics, radar chart, and fuzzy c-means (FCM) algorithm, a method is presented to evaluate hole surface quality quickly and effectively. Vibration signal is used as the main source of information about the drilling process. In this paper, wavelet packet energy spectrum (WPES) and higher-order statistics, which can image the information on both time and frequency domain, are applied as preparatory work for cluster analysis. Then, a ten-dimensional feature vector for cluster analysis is constructed from the value of higher-order statistics and wavelet packet energy ratio of the frequency bands where the energy is abnormal. Finally, cluster analysis based on radar chart and FCM algorithm is conducted on the feature vector for classification. By comparison, it is found that the cluster analysis result is basically consistent with the artificial test result. The proposed method can be further extended to the quality evaluation of other machining processes.

Description: This article provides an application of the total productive maintenance (TPM) philosophy as a systematic means for avoiding losses and increasing productivity in an auto-parts machining line. This is achieved by strategically implementing the pillars of TPM on the basis of failure data, then performing a thorough “root cause analysis” thereof (targeted improvement). Preventive maintenance plans and the empowerment of the autonomous maintenance program operator teams become the main pillar in the implementation of this new philosophy as a result. All this is done with the full support of the general management and each area of the organization in order to guarantee the full implementation and sustainability of the program.

Description: In the present work, an accurate 3D-FE model for simulating the extrusion process of AZ31 magnesium alloy tube was established based on the DEFORM 3D software package. The metal flow behavior and formation process of weld seam in the porthole die were revealed. The evolutions of temperature, velocity, and effective stress during the whole extrusion cycle were investigated. The K welding criteria was utilized to evaluate the influence of extrusion speed on the seam weld quality. Extrusion experiments were carried out at the extrusion speed ranging from 0.25 to 4 mm/s on an 800-t extrusion press. The simulation results show that the temperature distribution in the workpiece was not homogeneous. As the extrusion process proceeded, the greater the temperature gradient of workpiece was. The maximum temperature appeared at the bearing region. The dead metal zones existed at the corner between the container and the die face and between the bottom and the sidewall of welding chamber. The effective stress near the bearing and welding chamber was maximum, followed by the inlet ports of porthole die, and the minimum value was located in the container. As extrusion speed increased, the temperature, welding pressure, and effective stress on the welding plane increased simultaneously. The calculated K value decreased rapidly when extrusion speed increased from 0.5 to 2 mm/s and then reduced slowly when larger than 2 mm/s. Extrusion speed had a negative influence on the seam weld quality. The criteria exhibited a good predicting capability as compared with the experimental results. The optimum extrusion speed was about 0.5 mm/s for the extrusion of AZ31 magnesium alloy tube at the billet temperature of 400 °C on the 800-t extrusion press.

Description: The onset of chatter vibration in milling operations will result in poor surface finish and low machining productivity. Hence, it is of crucial importance to predict and eliminate this undesirable instability. In this paper, an Adams–Simpson-based method is developed for the stability analysis of milling processes. The regenerative chatter for milling operations can be described by delay differential equations with time-periodic coefficients. After dividing the forced vibration time interval equally into small time intervals, the Adams–Moulton method and the Simpson method are adopted to construct the Floquet transition matrix over one tooth passing period. On this basis, the milling stability can be obtained by using the Floquet theory. The accuracy and efficiency of the proposed method are verified through two benchmark examples, in which comparisons with the first-order semi-discretization method and the Adams–Moulton-based method are conducted. The results demonstrate that the proposed method has both high computational efficiency and accuracy, thus it is of high industrial application value.

Description: This paper presents the integration of a robotic system in a human-centered environment, as it can be found in the shoe manufacturing industry. Fashion footwear is nowadays mainly handcrafted due to the big amount of small production tasks. Therefore, the introduction of intelligent robotic systems in this industry may contribute to automate and improve the manual production steps, such us polishing, cleaning, packaging, and visual inspection. Due to the high complexity of the manual tasks in shoe production, cooperative robotic systems (which can work in collaboration with humans) are required. Thus, the focus of the robot lays on grasping, collision detection, and avoidance, as well as on considering the human intervention to supervise the work being performed. For this research, the robot has been equipped with a Kinect camera and a wrist force/ torque sensor so that it is able to detect human interaction and the dynamic environment in order to modify the robot’s behavior. To illustrate the applicability of the proposed approach, this work presents the experimental results obtained for two actual platforms, which are located at different research laboratories, that share similarities in their morphology, sensor equipment and actuation system.

Description: Grinding temperature field analysis is very significant to achieve controlled stress grinding and controlled grinding of affected layer depth. Heat source profile is an important basis for the grinding temperature field analysis. The heat source on the finished surface is more convenient than the heat source on the contact surface to perform grinding temperature field analysis both analytically and numerically. At present, the heat source profile on the finished surface was modeled to be rectangular, right triangular, triangular, or other shapes. However, all the modeled heat source profiles are not universally applicable under different grinding conditions. Therefore, the heat source profile on the finished surface under different grinding conditions needs to be further investigated. In this research, the inverse heat transfer analysis was performed to investigate the heat source profile on the finished surface under different grinding conditions. The investigation showed that the heat source profile on the finished surface is nearly right triangular in conventional shallow grinding, is triangular in creep feed grinding, and is close to be parabolic in HEDG (high efficiency deep grinding). Based on the investigation, the heat source profile on the finished surface was modeled as simple shapes to accommodate different grinding conditions. It was modeled to be right triangular in conventional shallow grinding and in creep feed grinding, and was modeled to be parabolic in HEDG. Error analyses of the predicted grinding temperatures obtained from the modeled heat source profiles were performed. The results showed that the modeled right triangular heat source profile is applicable in conventional shallow grinding and in creep feed grinding. The modeled parabolic heat source profile is applicable to most of the grinding parameters employed in HEDG. The modeled heat source profiles can conveniently serve as useful tools for grinding temperature field analysis in engineering.