ALBERT

Description: Die design is one of the key technologies for hot stamping technology, and the quality of the forming part is influenced by the structure design of the cooling system parameters. Cooling pipe size, distance between cooling pipes, and depth from cooling pipe to die surface are the most important structure parameters, and the final microstructure and property of the forming parts are influenced directly by these structural parameters. In this article, the simplified model of hot stamping die was established, and the hot stamping die cooling structural parameters were analyzed by heat transfer theory. The mathematical model of the structure parameters was set up and verified by simulation and experiment. It was shown that the mathematical model of the hot stamping die cooling structural parameters met the cooling requirements; the hot stamping parts achieved the need of the martensite structure.

Description: A common approach to the construction of surface-covering impact paths for computer-controlled manufacturing systems is to take a finite family of quasi-parallel offset curves of a seed curve on the workpiece surface. A possibility to get such curves is to consider the distance function of the seed curve in order to take the isolines of a finite sequence of increasing values. Besides several advantages, distance functions suffer from two problems which have an influence on the usefulness of the resulting curves: locations with discontinuous derivatives and local extrema. Optimization-based approaches for contour-parallel and direction-parallel offset curves, respectively, are presented to reduce these difficulties. For the contour-parallel case, the curvature, the mutual distance, and the topology of the isolines are optimized over a finite-dimensional family of scalar functions derived from the distance function of the contour. In the direction-parallel case, objectives including the number, the normal, and the geodesic curvature of isolines are optimized over the distance functions of a finite-dimensional family of seed curves. Algorithms to solve these optimization problems on triangular meshes are proposed and employed to demonstrate the usefulness of the methods.

Description: The biocompatibility of an implant material depends on the bulk physical properties as well as on the surface properties. Titanium alloy Ti6Al4V is a very popular biological implant material for its bulk physical properties resembling those of natural bone. It is possible to modify the surface properties of Ti6Al4V by laser irradiation. In the current study, using continuous wave fibre laser, grooves of different depths and widths have been created by varying laser power and scan speed. Laser frequency and duty cycle were varied to alter the inside surface topographies of the microgrooves. The surface wettability and the protein adsorption on the surface were found to be dependent on the microtexture parameters. To understand the effect of this type of texturing on the cell behaviour, MG63 cells have been cultured on the sample surfaces, and the result was studied after 3 and 5 days of cell culture. Surface features dimensionally closer to the cell dimensions are able to positively affect the viability and spreading of MG63 cells, as seen from this study.

Description: Preventive evaluation of costs is strategic for the whole manufacturing industry and especially for companies whose manufacturing technology is based on expensive machinery, tools and fixtures, such as injection moulding of aluminium. Preventive evaluation of production costs and time is even more relevant for the mould producer, in order to quickly prepare commercial offers with an acceptable degree of accuracy. In this paper, the application of a parametric approach for the evaluation of the labour content in the production of mould for injection moulding of aluminium automotive components is presented. The approach is based on simple geometrical features of the part to be produced derived from their 3D model using the basic tools of CAD systems. The data acquired from a specialized mould production company was analysed by factor analysis in order to determine the structure of the labour content and then parametric modelling was applied. The results evidenced an acceptable degree of accuracy of the estimate combined with an exceptional ease of application.

Description: The results of mathematical simulation have been carried out for the pattern of working medium motion providing the technological process of finishing–grinding treatment in an oscillating reservoir. With use of physics laws, it is ascertained and grounded that the flow of granules at the plane wall of reservoir is travelling oppositely to the source of vibrations, whereas the granules are drifting on the cycloid–trochoid trajectories from the wall of reservoir, where the looped displacement is maximal, to the center of reservoir in which the shift of granules is reduced to minimum because of damping and dissipation effect. The received theoretical regulations have a fundamental nature and can be used at the account of technological parameters of designed vibration machines.

Description: To be much closer to the cutting process and the actual cutting phenomenon, a new tool-chip friction model proposed in this paper takes account of the thickness of the material transfer layer of the chip which is ignored by most existing friction models. The material transfer layer, in which the chip material nearly stagnates on the tool rake face during machining, is located between the tool-chip contacting interface and the cutting interface in the secondary shear zone. Furthermore, the proposed model also contains the sticking, the transition, and the sliding friction regions along the tool-chip contacting surface and comprehensively depicts every region’s physical performance during dry machining. The global and the local friction characteristics between the tool and the chip are described based on coupled thermomechanical analytical method. Numerical results solved by the proposed model are compared with the existing experimental and simulated data in available literature. The results show that the proposed model was in good agreement with the experiments. The model provides an analytical method to predict friction characteristics conveniently and efficiently on the tool rake face during dry machining.

Description: This paper develops an optimization model to investigate the lengths of the optimal burn-in and warranty period, so that the mean of total product servicing cost is minimised. It is assumed that the cost of a minimal repair to a component at age t is a continuous non-decreasing function of t . Moreover, we model the customer dissatisfaction with product failures after the warranty within the product useful lifetime by introducing a post-warranty failure penalty cost to the manufacturer. The properties of the optimal burn-in time and optimal warranty policy are also analysed. Finally, under different product lifetime distributions, numerical examples and sensitivity analysis with respects to the values of the model parameters are provided.

Description: Fringe projection is a versatile method for mapping the surface topography. In this paper, it is used to measure the deformation of steel plates under static penetration. Here, the surface shape changes continuously. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with subpixel accuracy that requires only a single exposure for each registration. This is in contrast to phase shifting techniques that require at least three separate exposures.

Description: Plasma-sprayed YSZ coatings, serving as the thermal insulating top coating for thermal barrier coatings, involve thermally activated microstructural evolution, which may change the physical and mechanical properties and thereby influence the thermal barrier performance and service lifetime. In this study, 8YSZ and 20YSZ coatings annealed at 1300 °C were comparatively investigated to understand the effects of phase structure on the sintering behavior. Results show that, compared with the 20YSZ coating consisting of mainly thermodynamically stable cubic phase, the as-sprayed 8YSZ coating presented a multiphase structure mainly composed of thermodynamically metastable tetragonal phase, and significant phase transformation occurred during high-temperature exposure. The lamellar bonding had significantly improved because of the healing of intersplat pores. Fracture toughness, microhardness, and elastic modulus increased with sintering duration. The 8YSZ coating exhibiting the thermodynamically metastable tetragonal phase structure experienced a slower sintering kinetics than the 20YSZ coatings consisting mainly of thermodynamically stable cubic phase.

Description: Since the use of feature-based computer-aided systems became common in production, feature recognition has been a primary method to obtain features that contain specific engineering significance. In feature recognition, engineering significance is extracted from low-level elements and encapsulated into features to facilitate the various engineering tasks including process planning, manufacture and inspection. Due to the various classifications of features and their versatile application areas, there have been many different feature recognition approaches. These feature recognition methods are typically based on the part design models from computer-aided design systems. In this research, a new feature recognition method from computer numerical control (CNC) part programs for milling components is proposed. This approach uses feature recognition algorithms to integrate CNC part programs through the analysis of tool changes, spindle speeds, feed rates, raw material, tool geometry and tool paths to identify the manufacturing process plan. It has a major influence with the ability to extract process knowledge from the shop floor and represent it into a manufacturing feature-level data. This paper focuses on the recognition of 2½D features, but it can be extended to more complex features. Case studies are used to validate the use of the proposed method on typical milling features. Two sample parts are used to illustrate the efficacy and efficiency of the method. In addition, the proposed method is compared against traditional feature recognition techniques, and issues particular to feature recognition from part programs are discussed.

Description: Springback is the most common defect in sheet metal forming, especially for the advanced high-strength steel (AHSS) parts. The compensation method is an effective way to overcome this defect by modifying the die-face. A new geometrical springback compensation algorithm based on the advanced displacement adjustment (DA) method is proposed in this paper for automobile AHSS parts. The die-face is reconstructed by the non-uniform rational B-spline surface with the advantage of UV curves; furthermore, the continuity and topology of the die-face are also studied. The high-quality geometry compensation die-face obtained from this algorithm can be directly applied to actual machining. To reduce the time and cost of the die manufacturing, this algorithm is seamlessly integrated into the CATIA platform. A new compensation user-defined feature is created, which can meet the need for iterative compensation and parametric association. At the end of this paper, two engineering examples of AHSS parts verify the feasibility and validity of this algorithm and system.

Description: Friction stir welding (FSW) of non-linear joints receives an increasing interest from several industrial sectors like automotive, urban transport and aerospace. A force-controlled robot is particularly suitable for welding complex geometries in lightweight alloys. However, complex geometries including three-dimensional joints, non-constant thicknesses and heat sinks such as clamps cause varying heat dissipation in the welded product. This will lead to changes in the process temperature and hence an unstable FSW process with varying mechanical properties. Furthermore, overheating can lead to a meltdown, causing the tool to sink down into the workpiece. This paper describes a temperature controller that modifies the spindle speed to maintain a constant welding temperature. A newly developed temperature measurement method is used which is able to measure the average tool temperature without the need for thermocouples inside the tool. The method is used to control both the plunging and welding operation. The developments presented here are applied to a robotic FSW system and can be directly implemented in a production setting.

Description: A product manufacturing process starts from parts processing, then assembles parts into components, and forms the product finally. To obtain an expected product quality, the quality characteristics in the part level, component level, and product level must be controlled, and the deviations between their actual and target values are required to keep in specified tolerances. All these tolerances form a product tolerance system, and the quality characteristics of product levels contain the geometric and the non-geometric parameters, which are interrelated and form a complex system. General tolerance is the total amount the actual parameters are permitted to vary, which not only include the geometric parameters in machining, but also includes physical, chemical, electrical, and other parameters. What most concerns the product users is whether product quality characteristics meet their requirements, rather than a component quality characteristic or part quality characteristic, and the product quality characteristics are generally not only geometric quantities but also include many non-geometric quantities. The product tolerance system optimization design from part level to product level cannot be achieved, as it includes geometric and non-geometric quantities. In this paper, a product tolerance system model is developed on the basis of determining the quality characteristics of product levels, and the information of the product levels quality characteristics is excavated from data recorded in the product testing process using data mining methods through the support vector nonlinear regression relational model between parts quality characteristics deviations and product quality characteristics deviations. Then, the product manufacturing cost model is set up, which includes the machining dimensional tolerances and non-geometric tolerances, and the product tolerance system optimization model is developed by minimizing the product manufacturing costs as the objective function and the quality characteristics tolerances of product levels as constraint conditions. Finally, a micro-motor product is used as an example to optimize its tolerance system, and its manufacturing costs are decreased by 13.14 %. The results show that the developed method is effective and provides a new way for the product tolerance system optimization.

Description: In this investigation, the nanoscale removal of the multilayer metal film structure from the surface of glass hard disk platters is carried out by an electrochemical reaction. The electrolytic process used is assisted by the application of ultrasonic vibration at very high frequency which effectively enhances the speed and efficiency of metal layer removal. The results also show that higher concentrations of electrolyte and higher temperature also increase the rate of metal layer removal. A high electrolyte flow rate accompanied by high energy ultrasonics results in a high etching rate. The closer the anode is to the surface of the workpiece (platter) and the smaller the gap between the two electrodes, the higher is the etching rate. Further enhancement of etching rate can be achieved by using a smaller anode and cathode as well as by using electrodes with smaller edge radii. A high rotational speed of the anode and cathode module also enhances metal removal because it speeds up the flow of electrolyte across the surface of the workpiece to remove dregs and heat. A high current flow increases the rate of etching and allows a higher workpiece feed rate with a resultant increase in speed and overall efficiency. An optimal combination of processing parameters (electrical conditions, electrolyte flow and control, dregs removal, etc.) allows clean and complete removal of the multilayered nano metal film microstructure from the glass hard disk platters. The basic technology for the micro-electrochemical removal of the nano metal film from glass hard disk surfaces has been established. In addition, the results set a benchmark for the extension of basic laboratory equipment, as well as the implementation and commercial application of the method by industry.

Description: Cutting performance and failure mechanisms of the ceramic cutting tools such as TTW7, BW3, TWTN3, and SG4 in continuous machining hardened Cr12MoV mold steel were investigated. There were no microburrs on the finished surface when hardened Cr12MoV mold steel was machined by these tools with coolant. In order to obtain the optimal cutting parameters, the orthogonal tests were employed in this investigation. The optimal cutting parameters were depth of cut a p  = 0.3 mm, feed rate f  = 0.1 mm/rev, and cutting speed v  = 60 m/min. The wear resistance was BW3 〉 SG4 〉 TTW7 〉 TWTN3 when these tools continuously machined the workpiece under the optimal cutting condition. The main wear mechanisms were adhesive wear and abrasive wear.

Description: Ti–6Al–4V is widely used in the aerospace, automobile, and biomedical fields, but is a difficult-to-machine material. Electrical discharge machining (EDM) is regarded as one of the most effective approaches to machining Ti–6Al–4V alloy, since it is a non-contact electro-thermal machining method, and it is independent from the mechanical properties of the processed material. This paper aims to combine grey relational analysis and Taguchi methods to solve the problem of EDM parameters optimization. From the viewpoint of health and environment, tap water as working fluid has good working environment, since it does not release harmful gas. The process parameters include discharge current, gap voltage, lifting height, negative polarity and pulse duty factor. The electrode wear ratio (EWR), material removal rate (MRR) and surface roughness (SR) as objective parameters are chosen to evaluate the whole machining effects. Experiments were carried out based on Taguchi L 9 orthogonal array and grey relational analysis, and then verified the results through a confirmation experiment. Compared the machining parameters A 1 B 1 C 3 D 2 with A 1 B 2 C 2 D 2 , MRR increased from 1.28 mm 3 /min to 2.38 mm 3 /min, EWR decreased from 0.14 to 0.10 mm 3 /min and SR decreased from Ra 2.37 μm to Ra 1.93 μm. The process parameters sequenced in order of relative importance are: the ratio of pulse width to pulse interval, discharge current, lifting height and gap voltage. The results showed that using tap water machining Ti–6Al–4V material can obtain high MRR, decrease the machining cost and have no harmful to the operators and the environment.

Description: This paper presents a meta-heuristic method for a resource-constrained project scheduling problem. In this problem, the activities are given with multiple executive modes and there are minimum as well as maximum time lags between different activities. The objective here is to determine a mode and a start (or finish) time, for each activity such that total tardiness/earliness cost of activities could be minimized. The meta-heuristic approach was developed, as a two-phased genetic algorithm. The process of solving the proposed problem includes two stages (phases). In the first stage, through applying a genetic algorithm, the main problem is simplified so that each activity has only one executive mode. In the second phase, through developing another genetic algorithm, the best answer to the problem is achieved. Finally, the computational results obtained from the solution algorithms of this research were compared with the results existing in the Project Scheduling Problem Library (PSPLIB). These algorithms were provided in the MATLAB programming language. The findings show that our algorithm improved some of the best recorded solutions in the PSPLIB.

Description: Heavy-duty milling processes find productivity limitations due to chatter vibrations related to the dynamic flexibility of the machine tool structure. In high-speed machining, the critical dynamic properties and the resultant process stability are highly dependent on the tool or tool holder and not on the machined part, the machining position or the feed direction. The latter factors have, however, a significant impact on stability of heavy-duty operations, which makes the current stability models unsuitable for the stability prediction of this kind of operations. The present study proposes a standard stability model with specific improvements focused on heavy-duty operations, considering the whole workspace and feed directions. This model is used as the basis for the development of a universal process planning and tool selection methodology. Finally, the proposed method is experimentally verified in two practical cases, where a typical steel roughing operation is successfully optimised for two different machines. The usefulness of the developed methodology is demonstrated.

Description: We consider a multistage processing system, which includes both identical (parallel) machines that can process the same set of operations and different machines that can process only different operation sets. A release time r i is given for each job J i to be processed. For such a processing system, we minimize the makespan, i.e., problem IJ | r i | C max $IJ|r_i|C_{\max }$ is considered. The problem IJ | r i | C max $IJ|r_i|C_{\max }$ is an extension of the classical job-shop problem J | r i | C max $J|r_i|C_{\max }$ for the case when parallel (or identical) machines are also given. Both problems J | r i | C max $J|r_i|C_{\max }$ and IJ | r i | C max $IJ|r_i|C_{\max }$ are strongly NP-hard. A mixed graph model used for solving the problem J | r i | C max $J|r_i|C_{\max }$ is generalized for the problem IJ | r i | C max $IJ|r_i|C_{\max }$ . Using the mixed graph model, we developed a fast heuristic algorithm for solving the problem IJ | r i | C max $IJ|r_i|C_{\max }$ . Computational experiments were conducted to evaluate the performance of the algorithm on the 22 benchmark instances and on the 40 new randomly generated instances of the problem IJ | | C max $IJ||C_{\max }$ . For the small and moderate instances, the exact values of the objective function were compared with those calculated by the proposed heuristic algorithm. The average relative error was not greater than 2 . 4 % $2.4~\%$ for all instances with available optimal schedules. Computational results showed that the developed algorithm runs faster than some other heuristics being tested, and the schedules constructed by the developed algorithm have smaller makespans.

Description: High injury and fatality rates prevalent in all types of construction in the USA may be addressed by combining safety initiatives with process improvement through Lean. This study evaluated the impact on worker safety when Kaizen (a Lean tool) was used at a modular homebuilder. Twelve students who had completed a safety course and four safety experts rated the probability and severity of hazards (as determined by a job safety analysis, or JSA) present in three workstations; base-framing, sheet rock hanging, and painting. These ratings were provided after viewing a series of photographs taken before and after a Kaizen event performed at each workstation. The rating tool showed high reliability for all safety experts' ratings but only for students' ratings from the sheet rock hanging station. Students' and experts' ratings showed a significant reduction in risk in the base-framing station after the Kaizen, and student's ratings showed significantly reduced risk in the sheet-rock hanging station. Kaizen has the potential to improve safety in modular homebuilding and possibly, other manufacturing and construction activities.

Description: An investigation was reported on the cutting temperature in milling Ti6Al4V by applying semi-artificial thermocouple. ANOVA was conducted on the experimental results, and regression models were obtained. Analysis results showed that the tool temperature and workpiece temperature performed a similar rising trend with the increase of cutting parameters, including cutting speed, feed rate, radial feed, and axial feed. And their influence degrees decreased successively. The cutting force with different cutting parameters was also measured, and the relationship between cutting temperature and cutting force was discussed. It was found that cutting temperature and cutting force obtained in the experiment had the same fluctuation feature. Therefore, the cutting force and cutting temperature could complement each other for monitoring and analysis of the cutting process.

Description: This paper investigates how changes in chatter amplitude and frequency depend on process damping effect in dynamic turning process. For this purpose, the two degrees of freedom (TDOF) cutting system was modeled, and for an orthogonal turning system, the process damping model with a new simple approach was developed. To further explore the nature of the TDOF cutting model, a numerical simulation of the process was developed by this model. This simulation was able to overcome some of the weaknesses of the analytical model. The equations of motion for this cutting system were written as linear and nonlinear in the τ -decomposition form. The variation in the process damping ratios for different work materials was simply obtained by solving the nonlinear differential equations. A series of orthogonal chatter stability tests were performed for the identification of dynamic cutting force coefficients, using AISI-1040, Al-7075, and Al-6061 work materials, at a constant spindle speed. Finally, the experimental results were analyzed and compared with the simulation model, and it was observed that the results obtained through the experiments comply with the simulation model results.

Description: This paper focuses on the mechanism of high-speed grinding to achieve quality and efficiency for ceramics. The criterion of the brittle–ductile removal transition of ceramics is calculated and analyzed. The effects of the wheel velocity on the specific grinding forces, energy, and specific material removal rates were investigated. The influence of the wheel velocity on the surface integrity was studied in the terms of surface roughness by a 3D optical profilometer, scanning electron microscopy, respectively. The ductile removal mechanism of brittle material was validated experimentally. High quality and efficiency of grinding for SiC can been attained with high-speed grinding due to the understanding of the characteristics and mechanism for ductile grinding of brittle materials with high-speed grinding. Furthermore, based on the high-performance grinding mechanism, reasonable definitions on high-speed grinding are proposed.

Description: Frictional behavior of nano and hybrid-structured NiAl-Cr 2 O 3 -Ag-CNT-WS 2 adaptive self-lubricant coatings was evaluated at a range of temperatures, from room temperature to 700 °C. For this purpose, hybrid structured (HS) and nanostructured (NS) composite powders with the same nominal compositions were prepared by spray drying and heat treatment techniques. A series of HS and NS coating samples were deposited on steel substrate by an atmospheric plasma spraying process. The tribological behavior of both coatings was studied from room temperature to 700 °C at 100° intervals using a custom designed high temperature wear test machine. Scanning electron microscopy was employed for the evaluation of the composite coatings and worn surfaces. Experimental results indicated that the hybrid coating had inferior tribological properties when compared to the nanostructured coating, showing the attractive frictional behavior on the basis of low friction and high wear resistance; the NS coating possessed a more stable friction coefficient in the temperature range of 25-700 °C against alumina counterface. Microstructural examinations revealed more uniformity in NS plasma-sprayed coatings.

Description: This work explores the manufacturability of pyramidal fin arrays produced using the cold spray process. Near-net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using masks made of commercially available steel wire mesh. The feedstock powders used to produce the fins are characterized using scanning electron microscopy. Obstruction of the masks was investigated. The standoff distances between the substrate, mesh, and nozzle were empirically determined. Fin array characterization was performed using digital microscopy. The fin arrays’ heat transfer performance was assessed experimentally for a range of Reynolds number relevant to the application sought. The fins produced using the cold spray process outperform traditional straight (rectangular) fins at the same fin density and it is hypothesized that this is due to increased fluid mixing and turbulence.

Description: In order to realize the size measurement of large forgings in thermal state, an online measurement method based on line laser scanning is proposed in the paper. The measurement system mainly consists of a line laser projector and a charge-coupled device (CCD) camera. The laser projector is driven by the stepper motor for scanning the forgings continuously, while real-time images are captured by the CCD to provide the information for further feature extraction. First of all, particle swarm optimization algorithm is utilized to reduce the optical distortion error between actual and ideal images as a kind of optimization method. Secondly, the preprocessing is carried out to improve the image quality of the hot parts, and further two-dimensional image information of the forgings is obtained by means of center extraction. Thirdly, the size of forgings is calculated through processing the data acquired by continuous scanning the forgings and the real-time shotting. Finally, the measurement of forgings on overall outside size is achieved. The method proposed in the paper is viable according to the experiment results.

Description: The present work is meant to show the effective capability of optimizing an unbalanced Paired-Cell Overlapping Loops of Cards with Authorization (POLCA)-controlled production system by means of a heuristic algorithm. This objective is suggested by the fact that one of the most significant issues when using card-driven production control systems is represented by the optimized setting of the large number of cards within the control loops. This is particularly true in the case of unbalanced systems, where the number of cards may vary significantly among the different loops. Little law is usually adopted in literature to infer this number from historical data, but the obtained number is usually far from the optimum. Indeed, in real-world applications, the systems to be controlled are designed to process units with very different routings, each with different probability to occur. In all these situations, they result particularly difficult to set correctly. To this aim, in the present work a Genetic Algorithm is used. The objective is that of finding the correct number of cards and to reduce the overall Total Throughput Time and the average Work In Process. The proposed approach may provide a valid support tool to overcome these limitations, making the most of POLCA capabilities in many manufacturing configurations.

Description: This paper presents the design philosophy of an ultra-precision fly cutting machine tool from the machining material properties and the processing requirements points of view. Three configurations of the machine tool are proposed and compared from the aspect of the proposed design philosophy. The design philosophy has been applied to guide the development of the key machine components as well as an experimental prototype. In order to improve the dynamic performances of the machine tool, the influence of the main components on the tool–workpiece structural loop is analyzed, and the weak structural component is optimized. Preliminary machining trials have been carried out. The test results make a further proof and validate that the design philosophy proposed in this article can assure the high performance of the developed ultra-precision fly cutting machine tool for producing large diameter optics.

Description: Tribological tests were conducted on thermally sprayed silicon carbide (SiC) coatings to investigate its potential on reducing wear in offshore wind turbine bearings. The tests were carried out under dry conditions, 3.5 wt.% NaCl solution, and polyalfaolefin (PAO)-lubricated conditions. In order to obtain good quality SiC coatings, it is compulsory to modify the feedstock to limit SiC decomposition during atmospheric spraying process. The SiC feedstock used in this research has been modified with yttrium aluminum garnet (Y 3 Al 5 O 12 ) oxide additives that originated from its metal salt precursors. High-frequency pulse detonation (HFPD) technique has been utilized to produce coatings of around 100 μm in thickness. The sliding tests have recorded the lowest coefficient of friction (COF) of 0.15 in PAO condition and the highest COF of 0.50 in dry sliding. The wear tracks morphology show that during dry sliding test, the coatings experience abrasive wear accompanied by tribo-oxidation reaction that initiates crack formation along the splat boundaries. On the other two sliding test conditions (NaCl and PAO), polishing of asperities and some grain plowing from the splats were observed in the wear tracks. Tribochemical wear was found to be the main mechanism producing smooth surfaces. Nevertheless, in all cases, the wear losses were negligible.

Description: A distributed coevolutionary algorithm is proposed to solve the multiobjective hybrid flowshop scheduling problems to minimize the maximum completion time and total tardiness of jobs. The framework of the distributed coevolutionary algorithm consists of a global agent and multiple local agents. The global agent and local agents evolve independently and cooperate by interchanging a selected solution list. Unlike the cooperative coevolutionary algorithms in the literature, the proposed algorithm does not decompose the scheduling problem and executes evolutionary operations based on the whole solution of the problem in all the agents. SPEA2 is the core components in the local agents. Path relinking is applied in order to implement the evolutionary computation among non-dominated solutions in the global agent. We analyzed the time complexity of the proposed algorithm. To evaluate the performance against the benchmark of multiobjective evolutionary algorithms, it is tested on a large number of computational instances. The computational experiments show the proposed distributed coevolutionary algorithm can obtain better solution quality than other algorithms within given computational time.

Description: Fabrication of microparts has become increasingly important with an advancement of product miniaturization in various fields. Microgrooves are used as one of the key microfeatures in many microproducts like microthermal devices, microheat exchangers, microreactors, micropumps, and micromechanical systems. Electrochemical micromachining (EMM) can be effectively utilized for the fabrication of microgrooves because of its important benefits like reusability of the tool, no stress, burr-free surfaces, and ability to cut the material irrespective of the hardness. This paper presents the influence of EMM parameters like applied voltage, pulse frequency, duty ratio, tool feed rate, and electrolyte concentration on the machining accuracy, i.e., width overcut, depth overcut, and material removal rate during fabrication of a 500 μm-deep microgroove in stainless steel. An in situ-fabricated tungsten microtool of 110 μm diameter was used to generate a microgroove using the developed EMM setup. A high-quality microgroove with 55 μm width overcut and 10-μm depth overcut with an aspect ratio of 2.31 was fabricated using the optimum setting of machining parameters.

Description: Grind hardening process utilizes the heat generated in the grinding area for the surface heat treatment of the workpiece. The workpiece surface is heated above the austenitizing temperature by using large values of depth of cut and low workpiece feed speeds. However, such process parameter combinations result in high process forces that inhibit the broad application of grind hardening to smaller grinding machines. In the present paper, modelling and predicting of the process forces as a function of the process parameters are presented. The theoretical predictions present good agreement with experimental results. The results of the study can be used for the prediction of the grind hardening process forces and, therefore, optimize the process parameters so as to be used with every size grinding machine.

Description: Aimed at microplastic parts molding, we use a novel method of micro-ultrasonic powder molding (micro-UPM) on polypropylene (PP) microplastic parts and investigate the experimental process in detail. Firstly, the experimental results show that the temperature is maximum on the top outer edges of plastic parts and minimum on the bottom center. Then, the effects of experimental process parameters on plastic flashes are studied. The results show that under the same pressure, the flash thickness gradually thins with increased ultrasonic time. The ultrasonic time for the flashes to be automatically separated from the matrix of microplastic parts is obviously shortens with increased pressure. Finally, the tests on thermal properties, morphology, and mechanical properties of microplastic parts are also conducted. The results show that the melting point and crystallinity of microplastic parts produced by micro-UPM are higher than those of raw materials. The organizational structure shows no obvious “skin–core” structure, and its crystal form is α crystal form, which is the most common type of polypropylene. With increased ultrasonic time, the tensile strength and elongation at break of samples both have a trend of rise followed by drop before and after annealing. An ultrasonic time that is too long can lead to the degradation of materials.

Description: Functional micro surfaces have been recognized for their vital roles in a wide range of advanced applications. The fabrication of surface structures at the microlevel can be used to influence tribological, optical, and many other surface characteristics. To take advantage of the benefits of functional surfaces, industry and researchers have begun focusing on finding more sustainable and efficient manufacturing processes. The inclined micro ball end milling technique has become a fast and efficient method for creating micropatterned surfaces. With the right adjustments, the spindle speed and feed rate can be set so that the flutes of the cutter create periodic dimpled patterns onto a workpiece surface. This micromachining technique is an ideal method for fabricating dimpled surfaces, especially for metallic alloys such as dies and molds. Developing surface pattern algorithms for generating different dimple geometries can promote a sustainable future for a variety of novel products and lead to accurate manufacturing of surface characteristics. Accurate modeling of cutting forces is important in order to generate desired surface patterns without causing tool breakage and excessive tool deflection. In this study, a mechanistic force model for inclined ball end milling has been proposed and verified for generating micro-dimpled surface. The micro-dimple machining technique is also applied to microinjection molds to create polymeric components with micropatterns. Frictional aspects of both dimpled and inverted dimple surfaces have been investigated. The results indicate that micro-dimple machining combined with microinjection molding is a viable method of producing polymeric components with functional surfaces for advanced technological applications.

Description: High-strength wear-resisting aluminum bronze alloy is a difficult-to-machine material. Dry cutting tests were conducted on high-strength wear-resisting aluminum bronze alloy with YW1 cemented carbide tool and YBC251 coated cemented carbide tool. The wear mechanisms of the two tools were characterized with a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS) to compare their machining performances. And on that basis, the influences of cutting parameters, including cutting speed, feed rate, and cutting depth, on the tool life of the YBC251 coated cemented carbide tool and surface roughness of the workpiece were analyzed with a 3-D super-depth-of-field instrument and a surface profile measuring instrument, respectively. The results showed that the machining performance of the YBC251 coated cemented carbide tool was better than that of the YW1 cemented carbide tool. Among all the cutting parameters, it was found that feed rate had a stronger effect on tool life and surface roughness than cutting speed and cutting depth.

Description: Predicting the fragmentation process during rock cutting poses significant technical challenges. In this respect, previous research related to rock cutting using various numerical methods was reviewed in detail. A method for simulating the fragmentation process during the mechanical cutting of rock was then introduced using the explicit finite element code LS-DYNA. In the numerical simulations, the base rock material properties were defined using a damage constitutive model. This model simulates the separation of rock chips from the base rock material and the subsequent breakage of the chips into multiple fragments. In the simulations, a rigid steel cutting tool was translated at various sliding velocities (1, 4, 10, 50, and 100 mm/s) against a stationary rock material. For a given sliding velocity, simulations were conducted for various cutting depths (1, 2, 3, and 4 mm). The variation of stresses and the amount of chip formation at different depths of cut and velocities were analyzed. The simulations indicated that the cutting forces and chip morphology were significantly influenced by sliding velocities and cutting depths. Overall, the results indicate that the explicit finite element method was a powerful tool for simulating rock cutting and the chip fragmentation processes, as it was able to predict chip separation behavior from the base rock at different depths of cut accurately.

Description: Cold formed semi-finished products face an increasing demand from industry as they can be manufactured to dimensional precision and high surface quality. Products from cold formed bar, on the other hand, may contain inhomogeneous distributions of mechanical properties and residual stresses which arise from the elastic response of the material to an inhomogeneous distribution of elastic–plastic strains. These material properties may cause distortion in further manufacturing operations, and consequently, precision of components then could be reestablished at higher costs only. X-ray diffraction residual stress analysis, for example, is misleading if only slices or cross sections of a bar or a component are considered and residual stress fields and their variations are neglected. Automotive products generally are cut from drawn bars, and local differences in microstructure, mechanical properties and residual stress states are increasing the danger of dimensional changes out of a specified range. Cold-drawn bars were manufactured with different drawing angles and uncoated and TiCN-coated dies. Surface and subsurface properties were investigated along the length and around the periphery of drawn bars. Differences in material states, those affected by the contact zone and those related to the elastic–plastic deformation of the drawing process, were observed. The variation of surface residual stresses of up to a factor of 2 can be correlated with locally different friction coefficients and slip stick effects. As subsurface material states (residual stresses and strain hardening) do not show a significant variation around the periphery and along the length of bars, the effects of geometry variations of hot rolled bar, the effect of a not perfectly concentric bar at the die entrance and/or the level of pre-straightening ahead of drawing are assumed to be of minor importance, compared to the high level of plastic strain involved in cold drawing. The local properties identified here will lead to a higher degree of dimensional scatter of individual automotive components cut from these long cold-drawn bars.

Description: It is usually difficult to obtain good images for machine vision inspection in a manufacturing process. In practice, to obtain product characteristics, image enhancement methods are usually selected by trial-and-error or by experience. Therefore, image enhancement methods play a key role in image pre-processing. In this paper, we propose singular value decomposition (SVD) to extract the feature of images to automatically build image enhancement procedures. First, we completed image clustering according to the feature by using SVD. Next, the structural similarity index was used to select the optimal image enhancement method. To verify the procedures, 45 images from literature and local companies were used in the experimental analysis. For contrast value, the statistical analysis showed that the automatic enhancement result has no significant difference with the literature. The average entropy of the image relative to previous research increased to 17.54 %. The study results implied that the system could effectively improve the image quality and not over enhancement to produce noise.

Description: Self-pierce riveting has a future in the sheet metal assembly process in automotive industry. This paper aims to analyze the variation of auto-body aluminum alloy sheet metal assembly in self-pierce riveting and obtain the method of assembly variation analysis. With the help of the method of influence coefficients and the research of the assembly progress of auto-body aluminum alloy sheet metal in self-pierce riveting, a model which can reflect the effects of part variation, riveting tool variation, and fixture variation on assembly quality is established. The feasibility of assembly variation analysis is also verified by some practical cases. Finally, the orthogonal experiment has been carried out to analyze the effects of some variation sources on the variation of assembly in self-pierce riveting.

Description: A fast tool feeding mechanism with 2 degrees of freedom was proposed in this paper. The mechanism was directly driven and could compensate for changes in the cutting angle caused by contour adjustments. A turning system with constant cutting angle and speed were designed with the mechanism, which had many advantages including adjustable cutting angle, improving machined surface quality, reducing tool wear, extending the service life of tool, and so on. A model of the variable angle compensation movement of noncircular cross section part turning and its control algorithms was discussed according to the principle of inverse kinematics. With the machining of a convex oval piston taken as an example, a real convex oval piston model with a maximum ovality of 10 mm was processed through the fast tool feeding mechanism. Experiment results verified the design concept and control strategy of the mechanism.

Description: Stability prediction is important to avoid chatter and improve production efficiency in cutting process. Many methods including analytical, experimental, and numerical ones have been proposed. In this work, a stability criteria method using argument principle is proposed for a general dynamical systems. The method needs only to evaluate the characteristic function on a straight segment on the imaginary axis and the argument on the boundary of a bounded half circular region. The method is applied to three milling models in cutting process. Examples which show the evaluation of stability criteria proposed in the paper is simple and valid compared with full-discretization method.

Description: For laser surface hardening (LSH) of large-sized workpieces, a wide and uniform hardened layer of a single track is pursued. In this study, two kinds of shaped laser beams were used in LSH of 42CrMo cast steel to obtain the required hardened layer. One is a stripy spot with uniform-intensity array spots and the other a stripy spot with intensity blowup in the edge of the whole array spots. As a comparison, a Gaussian laser beam was also adopted. A three-dimensional finite element model was used to simulate the thermal history of specific points by the latter shaped beam and the Gaussian laser beam. The surface morphology, microstructure, microhardness, and uniformity of hardened layers were studied. The results showed that a wider and more uniform hardened layer could be obtained using the latter shaped beam at relative higher scanning velocities and laser power. The thermal history of a material has an important effect on the microstructure and microhardness finally formed. Due to the high peak temperature and heating rate caused by the latter shaped beam, a higher value of microhardness in the transformation hardened zone was found.

Description: Micro-electrical discharge machining (EDM) has been identified as a micromachining process for the fabrication of components of size down to the micrometer level. This process is derived from EDM, and the principles of both the processes are similar; yet, due to significant scaling down of the micro-EDM process, lots of modifications in circuit design, electrode diameter, stress developed, and energy levels are needed. The specific analysis and modification of micro-EDM process are required to understand these capability and limitations. Therefore, a numerical model based on finite volume method has been developed to solve the micro-EDM model equations and thereby predict the effect of spark ratio (spark on time/spark off time) on the temperature distribution in the material. Moreover, the results of the analysis are successfully tested against published ones.

Description: Flexible automated assembly is an emerging need in several industries. In the case of a very wide set of models and a total medium/low derived production volume, the proper assembly system to use is a single cell with high flexibility capabilities. An innovative concept in flexible automated assembly has recently been introduced [ 28 , 29 ]: the fully flexible assembly system (F-FAS). The F-FAS relies on a single-station robotized assembly system, where a unique fully flexible feeder is responsible for the delivery of the parts needed for assembly, guaranteeing a higher level of flexibility than the traditional automated FAS. The mixed-model sequencing (MMS) problem is typically related to the assembly line system. The aim of this paper is to introduce a new class of MMS problem: the single-station mixed-model sequencing problem that arises when the parts to assemble are randomly presented on the working plane, as in the F-FAS. The authors first define the MMS in such a single-station assembly system and then propose different sequencing algorithms in order to solve it. The authors first define the problem and then propose different sequencing algorithms. With the aim of finding the best sequencing approach to use in such an assembly system, the algorithms are compared through ad hoc developed benchmarking tests, using a dedicated software application that simulates the real behavior of the work cell.

Description: Al-TiO 2 -Fe 2 O 3 -MnO 2 -Fe-Sucrose-Epoxy Resin as reaction system and self-reactive quenching technology which combines flame thermal spraying, self-propagating high-temperature synthesis and rapid solidification, were used to prepare three kinds of hollow multiphase ceramic microspheres (HMCMs) in different feeding gas (N 2 , O 2 ) and dimension (coarse, fine). The characteristic results of three kinds of HMCMs indicated that various process parameters containing feeding gas and initial agglomerate size in this study can result in the change of surface organization, composition, morphology, and dimension. Investigation of microwave electromagnetic (EM) characteristics of three kinds of HMCMs showed that intrinsic characteristics play an important role in the determining the resulting properties. At 10-14.5 GHz, No. 3 HMCMs possess weak absorption intensity and narrow effective bandwidth (〈−10 dB) owing to smaller dimension, but in higher-frequency band (14.5-17 GHz), an obvious absorption peak appears due to good EM match and nano-effects. Compared with No. 1 (O 2 coarse) and No. 3 (O 2 fine) HMCMs, enhanced absorption intensity and effective bandwidth (〈−10 dB) were observed in No. 2 (N 2 coarse) HMCMs. Enhancements of absorption intensity and effective bandwidth are associated with extra nitride (AlN, FeN), partial open microspheres, M-hexagonal crystal and micro-nano thick dendrite. No. 2 HMCMs presented excellent microwave-absorption property, with the minimum reflectivity ( R L ) of −27.7 dB at 12.9 GHz. The effective bandwidth (〈−10 dB) could reach to 4.1 GHz (10.9-15 GHz). This may be ascribed to the increased conductance loss, multiple scattering, magnetocrystalline anisotropy, and shape anisotropy.

Description: Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al 2 O 3 ) powder in N 2 /H 2 thermal plasma. This study investigated the feasibility of RPS of a fine Al 2 O 3 /AlN mixture and the influence of the plasma gases (N 2 , H 2 ) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al 2 O 3 coatings with high nitride content were successfully fabricated. The coatings consist of h -AlN, c -AlN, Al 5 O 6 N, γ-Al 2 O 3 , and a small amount of α-Al 2 O 3 . Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N 2 gas flow rate improved the nitride content and complete crystal growth to the h -AlN phase, and enhanced the coating thickness. On the other hand, though the H 2 gas is required for plasma nitriding of the Al 2 O 3 particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles.

Description: Ni-based electrode coatings with enhanced surface areas, for hydrogen production, were developed using atmospheric plasma spray (APS) and suspension plasma spray (SPS) processes. The results revealed a larger electrochemical active surface area for the coatings produced by SPS compared to those produced by APS process. SEM micrographs showed that the surface microstructure of the sample with the largest surface area was composed of a large number of small cauliflower-like aggregates with an average diameter of 10 μm.

Description: Confronted with high variety and low volume market demands, many companies, especially the Japanese electronics manufacturing companies, have reconfigured their conveyor assembly lines and adopted seru production systems. Seru production system is a new type of work-cell-based manufacturing system. A lot of successful practices and experience show that seru production system can gain considerable flexibility of job shop and high efficiency of conveyor assembly line. In implementing seru production, the multi-skilled worker is the most important precondition, and some issues about multi-skilled workers are central and foremost. In this paper, we investigate the training and assignment problem of workers when a conveyor assembly line is entirely reconfigured into several serus . We formulate a mathematical model with double objectives which aim to minimize the total training cost and to balance the total processing times among multi-skilled workers in each seru . To obtain the satisfied task-to-worker training plan and worker-to- seru assignment plan, a three-stage heuristic algorithm with nine steps is developed to solve this mathematical model. Then, several computational cases are taken and computed by MATLAB programming. The computation and analysis results validate the performances of the proposed mathematical model and heuristic algorithm.

Description: In order to obtain a three-dimensional curved steel tube, a bending method is presented based on geometric curvatures with a scanning path planning decomposed into a two-dimensional model and restructured into a three-dimensional model, sequentially. In the decomposition and restructuring, tube plane bending is simplified into two-dimension curve project, while 3D tube bending is equivalent to two 2D space curves’ projects. In 2D bending, the plane deals with modeling idea based on the extreme points and inflection points of two-dimension curve. The main idea performs narrowing of scanning path near extreme point area, but widening scanning path near inflection point. In 3D bending, the forming surface is decomposed into two planar curves by projecting on two vertical planes. Respective scanning path planning and process parameters are thus acquired. By combining the data in the two-dimension planes, the three-dimension scanning path plane was obtained. Finally, an experimental verification is carried out to bend straight tubes into a two-dimension sinusoidal and a three-dimension helical tube/coil-shaped. The results show that the scanning path planning proposed in this paper is effective and feasible.

Description: One of the important design elements for a good production system is material handling. In cases where it is not well-designed, it can be the bottleneck in the system. Moreover, it can cause a lot of wastes such as waiting time, idle time, and excessive transportation and cost. In this study, material handling in lean-based production environments is taken into account. Depending on the lean structure of the production systems such as being pull-based, smooth, and repetitive, delivering the materials to the stations periodically becomes important. At this point, milk-run trains are highly used in real applications since they enable the handling of required amount of materials on a planned basis. With this study, it is aimed to develop a specific model for milk-run trains which travel periodically in the production environment on a predefined route in equal cycle times with the aim of minimizing work-in-process and transportation costs. Since the milk-run trains having equal cycle times start their tours at the same time intervals, it becomes simple to manage them. For this reason, they are used in lean production systems where level scheduling is performed. The developed model is based on mixed-integer linear programming, and since it is difficult to find the optimum solution due to the combinatorial structure of the problem, a novel heuristic approach is developed. A numerical example is provided so as to show the applicability of the mathematical model and the heuristic approach.

Description: Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate.

Description: This paper combines plasticity and circle grid analysis to investigate the deformation mechanics and failure in hole-flanging produced by single point incremental forming (SPIF). The approach is based on circle grid analysis and allows tracing strains and stresses along the deformation history of material to compare their maximum achievable values against necking and fracture limits in the principal strain and stress spaces. The overall methodology draws from the independent characterization of necking and fracture limits by means of sheet metal formability tests to the appraisal of strain loading paths in hole-flanging with blanks having different pre-cut hole diameters. The work is supported by experimentation in aluminium AA1050-H111 and the overall investigation widens previous research in the field by presenting the first set of experimental data covering the history of material strains, stresses and their corresponding formability limits.

Description: Many efforts in the past have been made to find more efficient methods for assembly sequence planning in machining area. While few researches reported in other area such as block assembly in shipbuilding industry. In general, a ship hull is built with hundreds of different blocks, most of which are complicated in structure and different from each other in assembly planning. Additionally, there may be a large number of feasible assembly sequences for any block. A better sequence can help to reduce the cost and time of the manufacture. Therefore, it is necessary to seek out the optimal sequence from all feasible ones. Currently, the assembly sequences are determined manually by some process engineers. Consequently, it is becoming a time-consuming task and cannot make the assembly plan consistent to improve productivity. In this paper, a methodology-integrated case-based reasoning and constraints-based reasoning is proposed to improve the assembly planning for complicated products. Besides, genetic algorithm is designed to evaluate and select the optimal sequence automatically from the reference ones. The validity of the method is tested using real blocks, and the results show that it can facilitate the optimal assembly sequences generation.

Description: In this paper, the effects and the optimization of cutting parameters on surface roughness (Ra) and material removal rate (MRR) in the wire electrical discharge machining (WEDM) of high hardness tool steel YG15 are analyzed. In the WEDM process, the key process parameters, such as pulse-on time, pulse-off time, power, cutting feed rate, wire tension, wire speed, and water pressure, are optimized. Experimental data were initially collected based on the Taguchi method of experimental design, which are $L_{18}\left (2^1\times 3^5\right )$ and $L_{18}\left (2^1\times 3^4\right )$ Taguchi standard orthogonal array on rough and finish cutting experiments, respectively. The level of importance of the cutting parameters on the Ra and MRR was determined on both finish and rough cutting by using statistical analyses; average gap voltage is discussed in order to balance cutting efficiency and stability on both finish and rough cutting. In addition, comparative analysis of finish and rough cutting is drawn to analyze the difference between rough cutting and finish cutting. Then, regression models and signal-to-noise ratio are used to obtain the optimum cutting parameter combination. Finally, the results present the optimized MRR and Ra of the rough and finish process, respectively, and confirm the efficiency and abilities of the model.

Description: During the classical manufacturing process of conical thread surfaces with lathe center displacement, the worm shaft is driven with the help of the driving pin through the lathe fork. As a result of the shifting of the worm shaft by half cone angle, the path curve of the driving pin will be an ellipse path instead of a circle on the perpendicular plane to axis. The peripheral speed of the spindle is constant, but due to the ellipse path, the radius is constantly changing as a function of time. That is why the angular velocity and the angular rotation are also changing, and these cause pitch fluctuation during the manufacturing process of conical worms. During the manufacturing process, we have examined pitch errors which are caused by angular velocity fluctuation and we have also determined the geometrical shaping of the driving pin by which errors of the pitch can be eliminated.

Description: Superplastic forming of titanium alloys is used for producing structural components, since it is an effective way to manufacture complex-shaped parts in a one-step operation. An optimized sheet-forming process has been designed incorporating a non-isothermal heating system to establish a fast forming process. This work sought to expand the advantages of the technology to the forming of Ti-6Al-4V alloy at 800 °C and shorter cycle time. The minimum thicknesses area was found at the outward corners, showing a maximum percent thinning of 54 %. In addition to stress variations, the cracks resulting from hot drawing and the oxidation on the sheet surface are the other reasons leading to thickness reduction. From the oxidization behavior of Ti-6Al-4V alloy, it was revealed that the decrease in forming temperature from 900 to 800 °C significantly reduced the formation rate of oxide film on the sheet surface. The study also showed that the main microstructure evolution of Ti-6Al-4V alloy under these conditions was recrystallization.

Description: In this research work, an experimental evaluation was conducted to explore the fretting fatigue life of multilayer Cr–CrN-coated AL7075-T6 alloy specimens with higher adhesion strength to substrate as the coating adhesion strength is one of the most critical issues in magnetron sputtering technique. Physical vapor deposition (PVD) magnetron sputtering technique was used for coating purpose, and a fuzzy rule-based system was established to investigate how to achieve higher adhesion of Cr–CrN coating on AL7075-T6 with respect to changes in input process parameters, direct current power, nitrogen flow rate, and temperature. Close assent was obtained between the experimental results and fuzzy model predicted values. Experimental result analysis was performed with Pareto–ANOVA variance as an alternative analysis. The fretting fatigue lives of coated AL7075-T6 alloy were improved 70 % and 22 % at high and low cyclic fatigue, respectively, compared with uncoated specimens.

Description: This article reviews the existing work in self-healing and self-repairing technologies, including work in software engineering, materials, mechanics, electronics, MEMS, self-reconfigurable robotics, and others. It suggests a terminology and taxonomy for self-healing and self-repair, and discusses the various related types of other self-* properties. The mechanisms and methods leading to self-healing are reviewed, and common elements across disciplines are identified.

Description: Turning is a widely used machining process, but the process complexity and uncertainty lead to empirical modelling techniques being preferred over physics-based models for predicting the process performance. The literature reveals that empirical methods such as artificial neural networks (ANN), support vector regression (SVR), regression analysis and fuzzy logic have been extensively applied in the modelling of turning process. The present work introduces genetic programming (GP) for the modelling of turning, but it is observed that the optimal models selected from the GP population based on training and validation errors do not perform well on testing data (unseen samples). Selecting the best GP model from the population of models is therefore a vital step. In view of this, the classification-driven model selection approach of GP (C-GP) is proposed in this paper. In this methodology, potential classification techniques such as Bayes multinomial, partitioning and regression trees, classification and regression trees and decision trees are integrated with GP to predict the class (best or bad) of the GP models. The model that is classified as the “best” by the most number of classification techniques is selected, and its performance is compared to those from ANN and SVR. It is found that the C-GP model has accuracy on par with ANN and gives satisfactory performance on testing data.

Description: In experiments, it is usually difficult to accurately determine simulation input parameters such as heat source parameters, material properties at high temperature, etc. The uncertainty of such input parameters is responsible for the large error of thermal simulation for weld-based additive manufacturing. In this paper, a new approach is presented to calibrate uncertain input parameters. The approach is based on the solution of the inverse heat conduction problem of small-scale five-layer deposition and the application of the infrared (IR) imaging technique. The calibration of heat source parameters involves a multivariate optimization search using the pattern search method, whereas the calibration of the combined radiation and convection model includes a number of one-dimensional searches using the Fibonacci search method. Based on an in-depth analysis of IR images, thermal characteristics such as mean layer temperature and cooling rate are selected as the comparison results and included in cost functions. Lastly, the validity of the approach is demonstrated by a simulation case of 15-layer deposition with calibrated input parameters. The comparison between the simulated and experimental results verifies the improved prediction accuracy.

Description: The loading path is crucial to the quality of forming parts in the process of tube hydroforming, and thus the design and optimization of loading path is an important issue for tube hydroforming. Wrinkling is a catastrophic defect for thin-walled tube hydroforming. In order to avoid wrinkling, an adaptive simulation approach integrated with a fuzzy control algorithm is used to optimize the loading path of hydroforming a T-shaped tube. The tubular material used is stainless steel and has an outer diameter of 103 mm and the wall thickness of 1.5 mm. The controlled variables are the axial feeding, the counterpunch displacement, and the internal pressure. A code is developed to make the optimization automatically, which works together with LS-DYNA. Six evaluation functions are adopted for identifying geometrical shape and quality of T-shape. Failure indicators obtained from the simulation results are used as the input of the fuzzy control, and then process parameters are adjusted according to the expert experiences in the fuzzy controller. In this way, a reasonable loading path for producing a sound T-shape is obtained, and also a T-shaped product is successfully hydroformed by experiment. The result shows that the fuzzy control algorithm can provide an adequately reliable loading path for hydroforming T-shaped tubes.

Description: In this paper, polyamide 6 single layer laser sintering process was investigated. A moving volumetric heat source model that involves the energy function morphology was simulated, and the temperature field distribution of a single layer of polyamide 6 powder was investigated using the finite element method, with different scan space and preheating temperature. The sintering processes were conducted on several batch of single layer with original thickness of 0.5 mm, which consists of 80 mesh polyamide 6 powders. Then the percentage of porosity was calculated and tensile stress of was tested. The results indicate that the scanning space strongly affect the percentage of porosity. For example, the percentage of porosity reaches 45.1 % when the scanning space increases from 0.25 to 0.45 mm. The results also indicate that the preheating and holding temperature strongly affect the mechanical properties. For example, the max tensile test stress increased from 2.04 to 4.10 MPa when the temperature rises from 50 to 150 °C, while the percentage of porosity shows very limited shift, reducing by only 9.54 %.

Description: Manufacturing capability sharing and circulation are the most important aims in cloud manufacturing (CMfg). In order to realize the above target, the issue of how to realize the formal description of manufacturing capability need to be solved. In this paper, a modeling and description method of multidimensional information for manufacturing capability in CMfg system is studied. Firstly, the concept and current research related to manufacturing capability are summarized. Then a multidimensional information model of manufacturing capability is established. Based on the model, a description method of manufacturing capability is proposed, and the related key technologies, e.g., fuzzy information description and dynamic behavior description, are systematically analyzed. Finally, the effectiveness of the proposed method is validated by a case study.

Description: One of the major manufacturing processes to produce components from flat sheets is forming. The automotive industry is one of the highest markets for stamped parts and is, thus, a major driving force for the development of new materials and technologies. In recent decades, there is increasing competition and growing demand for light weight, high-performance, and crashworthiness structures in the automotive vehicle forced steel industry, automakers, and the scientific community to focus more on efficient manufacturing. In recent decades, the increasing competition and growing demand for steel structures in automobiles was observed, especially for advanced high-strength steel (AHSS) parts. Thus, a better understanding of the formability of these materials is necessary to reduce costs and optimize the process. In order to better understand the mechanical behavior of AHSS, many authors have been researching the fracture aspects related to the stamping conditions. The main aim of this study was to analyze the type of fracture in DP600 steel when subjected to different stress/strain states (uniaxial and biaxial stress and plane strain) imposed by deep drawing and stretching. The experimentations led to a detailed understanding of the influence of stress/strain state in the mechanism of fracture, particularly, under plane strain—which showed quasi-cleavage regions surrounded by dimples. In addition, the microstructural analysis confirmed that the DP600 steel can show ductile fractures with some aspects of brittle behavior, depending of which stress/strain state was used for deformation. As a result, the DP600 forming limit curve related to micromechanisms of fracture generated by uniaxial and biaxial tensile stress and plane strain was presented.

Description: Automated manufacturing processes such as automotive tandem press lines include time dependent complex control functions. All motions and critical interactions between moving parts must be synchronised to avoid collisions and reach high production rate. It is even for a skilled operator hard to optimise these processes on-line. Therefore, a hardware-in-the-loop simulation including real industrial control systems and its control code establish an essential tool for optimisation. Additionally, an efficient optimisation algorithm is required to reach a useful simulation-based optimisation method. This paper proposes a new optimisation algorithm starting with the Lipschitzian algorithm DIRECT as global search and then switches over to the Nelder–Mead simplex algorithm for local convergence. During the switch over, the new algorithm determines all local candidates of the set of points evaluated by DIRECT and starts multiple Nelder–Mead local searches in each of these. An optimisation study for an automotive press line shows that the proposed algorithm combines the benefits of the Lipschitzian and the simplex algorithms in an efficient way. The importance of multiple local searches from all local candidates found is also shown in the study. Based on the same number of function evaluations, it is also shown that this algorithm reaches improved press line performances compared to the stochastic differential evolution algorithm.

Description: Adiabatic shear localization fracture (ASLF), which is a catastrophic fracture of the adiabatic shear band (ASB), will occur inevitably with the further increase of cutting speed. High-speed machining experiment of hardened AISI 1045 steel (HRC 45) is carried out by using a PCBN cutter with rake angle −10° at various cutting speeds up to 1,400 m/min and various feeds from 0.2 to 0.4 mm/r. Chip morphology (including discontinuously serrated chip and isolated segments), crack propagation, and blue brittleness effect in isolated segments formation are observed microscopically. Energy convergence in ASB with cutting conditions is calculated. Considering the effect of shear wave on the formation of ASB in high-speed machining, the ASLF theory under triaxial stress state is proposed and compared with the experimental results. The influences of shear band properties and loading conditions on ASLF are also discussed. The energy saturation limit of the shear band can be reasonably estimated by using the ASLF theory, which lays a theoretical and experimental foundation for further prediction study of isolated segments formation in high-speed machining.

Description: Zinc and its alloy coatings have been used extensively for the cathodic protection of steel. Zinc coating corrodes in preference to the steel substrate due to its negative corrosion potential. Numerous studies have been conducted on the corrosion behavior of zinc and its alloy coatings deposited using several techniques viz., hot dip galvanizing, electrodeposition, metalizing or thermal spray etc. Cold spray is an emerging low temperature variant of thermal spray family which enables deposition of thick, dense, and pure coatings at a rapid rate with an added advantage of on-site coating of steel structures. In the present study, the corrosion characteristics of cold sprayed zinc coatings have been investigated for the first time. In addition, the influence of heat treatment of zinc coating at a temperature of 150 °C on its corrosion behavior has also been addressed.

Description: The main aim of this study is to improve the coating properties of three-cathode atmospheric plasma-sprayed coatings with respect to porosity and residual stresses. This was done by means of numerical simulation coupled with advanced diagnostic methods. A numerical model for the triple injection of alumina feedstock, as well as acceleration and heating of the powder particles in the characteristic threefold symmetrical plasma jet cross section produced by a three-cathode-plasma torch, was developed. The modeling results for the standard injector’s position “0” were calculated and experimentally verified by laser Doppler anemometry. Based on the criteria defined for the concentrated feedstock transport and homogeneous thermal treatment of powder particles in the plasma jet, the optimal injection position was found. In the next step, a previously developed, coupled CFD-FEM-simulation model was used for simulations of the coating build-up, describing flattening, solidification, and deformation due to shrinkage for alumina particles on a rough substrate surface.

Description: Titanium-based coatings were deposited on aluminum samples using cumulative-detonation equipment. The gas mixture consumption (propane-oxygen-air) was up to 5 m 3 per 1 kg of powder. The titanium-based coatings were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) with diffraction, x-ray phase analysis, hardness measurements, and plasticity adhesion/cohesion resistance scratch tests. It was shown that the detonation titanium-based coatings are characterized by the presence of nanodispersed ceramic compounds and exhibit high values of plasticity, hardness, and adhesion strength. The titanium-based coatings had an amorphous structure, high hardness of up to 16 GPa, and a tensile bonding strength ranging from 52.5 to 53.0 MPa. A failure mode occurring in the tested samples was cohesive within the inter and intralamellar structure of coating.

Description: Behavior of an axisymmetric cold spray supersonic gas-particle jet passing through an axisymmetric aperture having a diameter smaller than the jet dimensions is considered. The particular case studied in the paper is the interaction between a supersonic jet delivered by a nozzle with a 7.8 mm exit diameter and a solid plate with a 3 mm aperture. The gas and aluminum particle parameters after passing through the aperture are experimentally and numerically studied. Under conditions used in this study, the decelerating influence of the aperture on the aluminum particle velocity is found negligible for spray distances less than 40 mm.

Description: Amorphous/nanocrystalline coatings are useful in high strength and wear-resistant applications. In the present study, the microstructural evolution of a nanocrystalline high performance steel coatings developed by different spray processes along with a novel “hybrid thermal spray” technique was studied. The hybrid-spray process combines arc and high-velocity oxy-fuel (HVOF) techniques, in which the molten metal at the arcing tip is atomized and rapidly propelled toward the substrate by HVOF jet. This so-called hybrid concept offers the benefits of productivity of electric arc spray combined with improved coating densities of HVOF. The microstructural characterization of the hybrid-spray coatings was performed by x-ray diffraction, electron microscopy, and differential scanning calorimetry, and then compared with coatings of the similar material developed by plasma-, HVOF-, and arc-spray processes individually. The HVOF- and plasma-spray coatings showed amorphous structures with very fine nanocrystals embedded, whereas hybrid- and arc-spray techniques yielded completely crystalline coatings with grain size in the range of several nanometers. The final microstructures in different spray processes could be attributed to the precursor materials employed, process temperatures, and cooling rates during the deposition process.

Description: High Cr content Ni-Cr-Ti arc-spray coatings have proven successful in resisting the high temperature sulfidizing conditions found in black liquor recovery boilers in the pulp and paper industry. The corrosion resistance of the coatings is dependent upon the coating composition, to form chromium sulfides and oxides to seal the coating, and on the coating microstructure. Selection of the arc-spray parameters influences the size, temperature and velocity of the molten droplets generated during spraying, which in turn dictates the coating composition and formation of the critical coating microstructural features—splat size, porosity and oxide content. Hence it is critical to optimize the arc-spray parameters in order to maximize the corrosion resistance of the coating. In this work the effect of key spray parameters (current, voltage, spray distance and gas atomizing pressure) on the coating splat thickness, porosity content, oxide content, microhardness, thickness, and surface profile were investigated using a full factorial design of experiment. Based on these results a set of oxidized, porous and optimized coatings were prepared and characterized in detail for follow-up corrosion testing.

Description: A cermet-supported tubular SOFC was fabricated using thermal spray. The cell performance was investigated at temperatures from 750 to 900 °C and pressures from 0.1 to 0.5 MPa to examine the effect of operating gas pressure on the cell performance. The influence of gas pressure on the cathodic polarization was studied through the electrochemical impedance approach to examine the controlling electrochemical processes during cell operation. Results show that increasing the operating gas pressure improves the power output performance significantly. When the gas pressure is increased from 0.1 to 0.3 MPa, the maximum power density is increased by a factor of 32% at a temperature of 800 °C. The cathode polarization decreases significantly with the increase of the gas pressure. The electrochemical analysis shows that the main control processes of the cathode reaction are the oxygen species transfer at the three-phase boundary and oxygen diffusion on the surface or in the bulk of the cathode, which are enhanced with increasing gas pressure.

Description: Bulk yttrium monosilicate (Y 2 SiO 5 ) possesses interesting properties, such as low thermal expansion coefficient and stability in water vapor atmospheres, which make it a promising protective layer for SiC-based composites, intended for the hottest parts in the future gas turbines. Because protective layers are commonly applied by thermal spraying techniques, it is important to analyze the changes in structure and properties that these methods may produce in yttrium silicate coatings. In this work, two SiO 2 -Y 2 O 3 compositions were flame sprayed in the form of coatings and beads. In parallel, the beads were spark plasma sintered at relatively low temperature to obtain partially amorphous bulk specimens that are used as model bulk material. The thermal aging—air and water vapor atmosphere—caused extensive nucleation of Y 2 SiO 5 and Y 2 Si 2 O 7 in both the bulk and coating. The rich water vapor condition caused the selective volatilization of SiO 2 from Y 2 Si 2 O 7 at the specimen surface leaving a very characteristic micro-ridged Y 2 SiO 5 zones—either in coatings or sintered bodies. An important increase in the thermal conductivity of the aged materials was measured. The results of this work may be used as a reference body for the production of Y 2 SiO 5 coatings using thermal spraying techniques.

Description: Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 10 3 -10 4 , which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity.

Description: An evaluation of microstructure-property relationship is important for thermally sprayed composite absorber coatings, because self-similarity in the microstructure is a key characteristic that can affect coating properties, such as flattened particle shape, pores, absorbent phase, and coating thickness. In this paper, a multiscale effective fractal model is reported to characterize the microstructure-property relationship for high-velocity oxygen fuel (HVOF) sprayed composite coatings. It shows the fractal of coating structure was presented to calculate the volume fraction of thermally sprayed absorber coatings with wavelet-fractal algorithm. As an example, the flattened particle shape, porosity, and thickness were researched for the microwave reflectivity coefficient of HVOF sprayed nanometer LBS (Li 2 O-B 2 O 3 -SiO 2 )-SiC β composite coatings. The modeling approaches to establishing the relationships between coating microstructure and absorbing property was checked.

Description: This study reports the fabrication of LZ91 magnesium alloy screws using warm heading and thread-rolling processes. The proposed method consists of a two-stage warm heading process. This study presents an analysis of the material flow pattern of the billet inside the die by using finite element analyses. This study also presents the effects of upper die velocity, temperatures, and friction factors on the heading loads and product quality. This paper also investigates the effects of the friction factor on the effective stress, effective strain, and tooth height in a thread-rolling process. Finally, warm heading and thread-rolling experiments were conducted using a self-designed die set and a MoS 2 lubricant. This study presents a comparison of the experimental values with the simulation results to verify the validity of the finite element models and the proposed warm heading procedures.

Description: In the current metal-forming industries, productivity, product quality, and production cost are three overriding issues. Product quality, however, is the most critical issue and the designed forming process must be able to produce the quality parts with desirable geometries and without defects. In micro- and meso-forming processes, the formation mechanism of flow-induced defects has not yet been fully investigated. In this paper, the flow-induced defects in meso-forming of a designed part are investigated and the defect formation mechanisms are explored and revealed via the finite element simulation of the entire process. To develop a defect-free forming process, a feature-based method for defect-free process design is proposed to identify the best forming sequence/process for defect-free deformation. By employing the proposed method, two meso-forming processes, viz., four steps extrusion and backward extrusion, are proposed to fabricate the designed part without folding defects. The applicability of the meso-forming processes for defect avoidance is verified by numerical simulation and physical experiment. The experiments also corroborate the findings of finite element simulations. On the other hand, the proposed feature-based method is further verified by the effectiveness of the generated two meso-forming processes for their efficiency in forming of the meso-scaled part without the flow-induced defects.

Description: Five-axis machining is more widely used in manufacturing of freeform surfaces. However, in five-axis machining of freeform surfaces, incomplete information exchange between computer numerical control (CNC) and computer-aided design/computer-aided manufacturing (CAM) results in many limitations need to be rectified. In the paper, a new structure of CNC based on STEP-NC standard is proposed, where tool path planning, tool offset, and inverse kinematics are transferred from CAM to CNC. In order to guarantee good openness, open platform and standard interface are applied in the development. Technology of module collaboration and design of data flow are studied. A five-axis real-time interpolator for non-uniform rational B-spline surfaces machining is realized. Based on these technologies, a five-axis CNC is developed in the manner of software realization, which consists of interpreter, task coordinator, axis group, softPLC, etc. The software CNC system has been applied on a tilt-rotary type five-axis machine tool, where the milling experiment has been performed successfully.

Description: A solid trimming method is proposed to determine cutter–workpiece engagement (CWE) maps, which are essential to investigate cutting forces, machining errors, and chatter stability in multi-axis milling. In this method, CWE maps, defined as the instantaneous contact area from the cutting flutes’ entrance to exit, are extracted by trimming the removal volume (RV) with the feasible contact surfaces. Compared to the traditional Boolean operation approach, the trimming method extracts CWE maps without the requirement of abundant surface/surface intersection operations. Moreover, instead of using the union solid model associated with all cutter locations, RV is calculated for the first time by introducing the existing concept of analytical tool swept volume, which is previously limited to tool path planning. Verification tests show that the proposed method has the advantages of high accuracy and efficiency.

Description: One of the industrial applications of computer vision is the automated detection and characterisation of surface defects. Some types of surface, such as those that are highly reflective or transparent, require the implementation of custom-made systems for automated inspections. The purpose of this article is to present a machine vision system, with an easily configurable hardware–software structure, for surface quality inspection of transparent parts. This structure permits that different products and part models may be inspected by the system. Its hardware is composed of image-capturing devices and mechanisms for manipulating and holding the part to be inspected. One such mechanism is the lighting system, which has been specifically developed to allow real-time quality control of this type of surfaces. As regards software design, a component-based approach has been adopted in order to increase reusage of the code and decrease the time required for configuring any type of part and adapting it for inspection. To test the efficiency and robustness of the industrial setup, a series of tests using a transparent industrial part, specifically, a commercial model of headlamp lens, have been assessed.

Description: Part II of the present study is a comparative study of high-speed machining of Ti-6Al-4V and Inconel 718, focusing on a comparison between the effects of dynamic tool edge wear on cutting vibrations. This paper describes in detail how cutting vibrations were measured and how vibration signals were processed using a wavelet packet transform technique. A total of 60 high-speed machining experiments were performed, covering a range of cutting speed and feed rate conditions. The experimental results show that tool edge wear has a complex effect on the cutting vibrations. The vibration amplitudes in high-speed machining of Ti-6Al-4V can be higher or lower than those in high-speed machining of Inconel 718, depending on the particular cutting speed and feed rate employed. Analysis of variance reveals that both the cutting speed and the feed rate always play a statistically significant role in affecting the vibration amplitudes in all three directions, i.e., the cutting speed direction, the feed rate direction, and the depth of cut direction. It is also revealed that in high-speed machining of Ti-6Al-4V, four significant wavelet packets (W30, W32, W33, and W36) exist, depending on the particular cutting conditions employed. In high-speed machining of Inconel 718, two significant wavelet packets (W32 and W33) exist, regardless of the cutting conditions employed. The significant wavelet packets identified in part II of the present study can be used as features to detect and monitor tool edge wear in high-speed machining.

Description: FGH95 is one kind of powder metallurgy (PM) superalloy which has excellent mechanical properties at high temperature. It has been developed for turbine disc applications to improve aeroengine efficiency under higher operating temperatures. However, this kind of superalloy is very difficult to machine because of its poor thermal diffusivity and work-hardening properties during the machining process. The machining process can lead to damage of the machined surface and subsurface. Thus, the purpose of this paper was to investigate damage of the machined surface and subsurface in hard machining of FGH95 PM superalloy. Orthogonal milling experiments using coated carbide inserts were carried out on a CNC machining center. The machined surface was observed and recorded using an optical microscope, white light interferometer, and scanning electron microscope. Machined surface defects were recorded and analyzed. The effects of cutting speed on machined surface roughness, white layer thickness, plastic deformation, and microhardness were investigated. The research results show that better surface roughness can be generated at higher cutting speeds, while several defects appeared on the FGH95 machined surface. White layer thickness and machined surface microhardness increase with the cutting speed. Also, plastic shear strain in the machined surface layer increases with cutting speed. The depth of plastic deformation decreases with the increase of cutting speed. These investigation results are essential for the evaluation of PM superalloy surface integrity and are significant for the prediction of PM superalloy service life.

Description: Electrochemical machining (ECM) is well-established in certain areas, such as the aerospace, defence, and medical industries for machining complex parts. ECM is an effective way to produce compression blades. However, with advances in the development of aero engines, the accuracy of blades becomes higher and their shapes have also become more complex. Thus, considerable attention has been devoted to improving the machining accuracy of blades by ECM. In blades machined by ECM, the angle between the cathode feeding directions and the normal of the anode profile greatly affects the accuracy of the ECM process, and it is determined by the angle combination of the anode installation and the cathodes feeding direction. It is very important to determine the best angle combinations that could minimise the angle between the cathode feeding directions and the normal of the anode profile. The present paper focuses on the optimization method of the angle combinations of the cathode feeding directions and anode installation. A theoretical model describing the optimization method of the cathode feeding directions and position of the anode was developed, and the experimental investigations were conducted in order to evaluate the rationality of the optimization method. The results show that with the optimized combination of the cathode feeding directions and position of the anode, the maximum angle between the cathodes feeding directions and the normal of the anode profile is minimised and the inter-electrode gap between the cathode and anode is more uniform. Thus, the machining accuracy could be clearly improved and the maximum errors of the convex part and concave part were only 0.054 and 0.047 mm, respectively.

Description: As a strongly NP-hard problem, the hybrid flow-shop problem with multiprocessor tasks (HFSPMT) has gained increasing attention due to its academic significance and application value. In this paper, an effective algorithm based on the shuffled frog leaping algorithm (SFLA) is proposed for solving the HFSPMT. First, three decoding methods are used together to decode a solution to a better schedule. Especially, the forward scheduling decoding method is employed, aiming at narrowing the idle time between consecutive operations in the processor as well as increasing the flexibility in selecting processors to schedule the following operations. Second, a bilevel crossover is designed to make each individual share the good “meme” within each memeplex and exchange the good “meme” between different memeplexes. Third, multiple local search operators are used in an effective way by employing the meta-Lamarckian learning strategy to enhance the local exploitation ability. Meanwhile, the use of crossover and local search together in the SFLA can enrich the memetic search behavior and balance the exploration and exploitation abilities. In addition, the effect of parameter setting of the algorithm is investigated based on the Taguchi method of design of experiment, and suitable values are suggested for the parameters. Extensive testing results based on two types of well-known benchmarks are provided. And the effectiveness of the proposed algorithm is demonstrated by the comparisons with some existing algorithms.

Description: The use of composite parts, especially in aeronautics, is increasing at an exponential rate. However, machining of this material is complicated due to different phenomena such as delamination, burned resin, and cutting edge failure. The aim of the present study is to introduce a new method for optimizing cutting conditions, using a correlation between vibration and machining defects. Down milling of a carbon/epoxy composite material with a single polycrystalline diamond insert was performed. To minimize the number of experiments, a central composite design with 20 combinations was studied, using parameters such as cutting speed, depth of cut, and feed rate. Vibration levels were measured for each cutting condition. Results obtained from the analysis of variance confirm that the mathematical models used in this study could adequately describe the performance indicators. A vibration criterion was defined to describe the regions with and without defects of the machining. This technique validated through testing should help the operator to choose the optimal cutting conditions.

Description: Sheet metal parts are widely used in various industry branches. The flat pattern development of sheet metal components is a prerequisite for sheet metal fabrication. The conventional graphic solution or the analytical method carried out manually is laborious, time-consuming, and lacks accuracy. The feature-based flattening could help to achieve the objective of automatic pattern generation; however, it is only suitable for bend formable sheet metal components composed of flat and simple curved surface. Inspired by its wide applications in cloth and shoemaking industries, the energy-based flattening for mesh surface is then introduced into the flat pattern derivation of sheet metal parts in this paper. A simplified energy model is proposed as our physical model. An innovative energy relaxation process based on variable step size is introduced to promote efficiency. Some key issues like seed triangle selection and overlap correction are also concerned. For those complex surfaces, a hierarchy flattening methodology is proposed to release the flattened distortions. A comparison between the energy method and the classic as-rigid-as-possible mesh parameterization is made to show the effectiveness of our method. The numerical experimental results show that the energy-based flattening method is a practical, intelligent, and automatic approach for flat pattern generation of sheet metal components.

Description: In order to improve the ablation resistance of C/C composites, ZrB 2 -based coating was prepared by supersonic atmosphere plasma spraying for SiC-coated C/C composites. The phase composition, microstructure, and anti-ablation property of the coating were investigated. Results show that the supersonic atmosphere plasma spraying is an effective method to prepare a dense ZrB 2 -based coating. The coating largely improves the ablation resistance of C/C composites. The linear ablation rate is 0.17 μm/s after ablation for 60 s in oxyacetylene torch. In ablation center, the ablation performance is determined by complicated mechanical denudation and chemical erosion. The formation of ZrO 2 during ablation can partly prevent the diffusion of oxygen, which contributes to the good ablation resistance of ZrB 2 -based coating. In transition zone, the generation of SiO 2 prevents inner coating from ablation and the chemical erosion becomes the leading mechanism.

Description: To protect carbon/carbon (C/C) composites against oxidation, ZrSiO 4 oxidation protective coating was prepared on SiC-coated C/C composites by supersonic plasma spraying. X-ray diffraction and scanning electron microscopy were used to analyze the phase and microstructure of the coating. The results show that the as-prepared ZrSiO 4 coating is continuous and well bonded with the SiC inner layer without penetrating crack, which exhibits good oxidation-resistant properties. After oxidation at 1773 K in air for 97 h and nine thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 0.08%. The excellent oxidation-resistant properties of the coating were attributed to its dense structure and the formation of the stable ZrO 2 -SiO 2 glassy mixture on the surface of ZrSiO 4 coating.

Description: In this study, FeBSiNb coatings were prepared by twin wire arc spraying process. The microstructure and mechanical properties of as-sprayed coatings were characterized. The results show that the coating is adhering well and very compact with porosity of 1.2% (the value range is 0.9-1.7%). The microstructure of the coating consists of full glassy structure. The crystallization temperature, microhardness, elastic modulus, and average adhesive strength of the coating are 819 K, 16.42 GPa (the value range is 14.38-18.46 GPa), 219 GPa (the value range is 201-237 GPa), and 57.4 MPa (the value range is 55-64 MPa), respectively. The relatively wear resistance of the coating is about three times than that of 3Cr13 martensite stainless steel coating. The reasons for excellent wear resistance of FeBSiNb metallic glass coating are attributed to a uniform amorphous structure, the high ratio of hardness to elastic modulus ( H / E ) and the ratio of the elastic deformation energy to the total deformation energy (η value). The main failure mechanism of the coating is brittle failure and fracture.

Description: Composite coatings containing Cu, Co, Ni, and samaria-doped ceria (SDC) have been fabricated using a novel hybrid atmospheric plasma spraying technique, in which a multi-component aqueous suspension of CuO, Co 3 O 4 , and NiO was injected axially simultaneously with SDC injected radially in a dry powder form. Coatings were characterized for their microstructure, permeability, porosity, and composition over a range of plasma spray conditions. Deposition efficiency of the metal oxides and SDC was also estimated. Depending on the conditions, coatings displayed either layering or high levels of mixing between the SDC and metal phases. The deposition efficiencies of both feedstock types were strongly dependent on the nozzle diameter. Plasma-sprayed metal-supported solid oxide fuel cells utilizing anodes fabricated with this technique demonstrated power densities at 0.7 V as high as 366 and 113 mW/cm 2 in humidified hydrogen and methane, respectively, at 800 °C.

Description: A titanium composite coating containing in situ synthesized oxides or nitrides was deposited on mild steel by reactive atmospheric plasma spraying. The relationships between the porosity, hardness, the phase composition of the sprayed coatings, and the spraying parameters were investigated. Titanium powders were used as starting powder materials. XRD analysis and microhardness test revealed that titanium oxides and nitrides were synthesized during the spraying process. The longer the spraying distance, the more the Ti nitrides’ content in the coating. It is shown that the Ti nitrides’ content has a significant influence on coating hardness. An in situ titanium composite coating with a hardness value of 1534HV 0.1 and an adhesive strength of 55.4 MPa was made with appropriate spraying parameters.

Description: In the present study, WC-12Co coatings were deposited by detonation-spraying technique using conventional and nanostructured WC-12Co feedstock at four different oxy/fuel ratios (OF ratio). The coatings exhibited the presence of phases like W 2 C and W due to the decarburization of the WC phase, and the proportions of these phases were higher in the nano WC-12Co coatings compared with conventional WC-12Co coatings. Coating hardness and fracture toughness were measured. The tribological performance of coatings was examined under dry sand rubber wheel abrasion wear, and solid particle erosion wear conditions. The mechanical and wear properties of coatings were influenced by degree of decarburization and more so in the case of nanostructured WC-Co coatings. The results indicate that the extent of decarburization has a substantial influence on the elastic modulus of the coating which in turn is related to the extent of intersplat cracking of the coating.

Description: A modified high-velocity oxy-fuel spray (HVOF) thermal spray torch equipped with liquid feeding hardware was used to spray manganese-cobalt solutions on ferritic stainless steel grade Crofer 22 APU substrates. The HVOF torch was modified in such a way that the solution could be fed axially into the combustion chamber through 250- and 300-μm-diameter liquid injector nozzles. The solution used in this study was prepared by diluting nitrates of manganese and cobalt, i.e., Mn(NO 3 ) 2 ·4H 2 O and Co(NO 3 ) 2 ·6H 2 O, respectively, in deionized water. The as-sprayed coatings were characterized by X-ray diffraction and field-emission scanning electron microscopy operating in secondary electron mode. Chemical analyses were performed on an energy dispersive spectrometer. Coatings with remarkable density could be prepared by the novel high-velocity solution precursor flame spray (HVSPFS) process. Due to finely sized droplet formation in the HVSPFS process and the use of as delivered Crofer 22 APU substrate material having very low substrate roughness ( R a  〈 0.5 μm), thin and homogeneous coatings, with thicknesses lower than 10 μm could be prepared. The coatings were found to have a crystalline structure equivalent to MnCo 2 O 4 spinel with addition of Co-oxide phases. Crystallographic structure was restored back to single-phase spinel structure by heat treatment.

Description: Wire arc spraying is an economically attractive thermal spray process that is especially interesting for the protection of large-scale parts or constructions. This study presents the results of the development and investigation of a number of cored wires based on the Fe-Cr-Al system with minor addition of alloying elements (B, Mn, Ni, Si, Ti, Mg, etc.). The microstructure of the coatings, their electrochemical behavior, and isothermal oxidation performance over a temperature range of 20-700 °C were investigated. Erosion resistance at elevated temperatures was determined with a laboratory test unit under test conditions that have simulated the work conditions in fossil-fuel-fired boilers. It was established that the oxidation resistance and the gas-abrasive wear resistance of arc-sprayed coatings depend mostly on the coating microstructure and homogeneity of element distribution rather than on the general alloying level and microhardness of the coating. A new parameter for coating characterization, namely, the coefficient of chemical microheterogeneity, K CMH , is introduced to quantify this influence. Formation of the coating microstructure at elevated temperatures and its influence on the protection ability of the coating are discussed.

Description: The capabilities of additive manufacturing technologies to fabricate multi-material structures have been investigated in many studies. However, only a few of the technologies have been used to fabricate products for direct application. The full development of the capability will enable the fabrication of innovative engineering structures consisting of function-specific material members that cannot be realized using conventional methods. In this work, a methodology for fabricating dual-material engineering structures using ultrasonic additive manufacturing (UAM) was developed. An example structure consisting of members designed to carry tension and compression loads were fabricated using composite materials and Al 3003 matrix material respectively. MetPreg®/Al 3003 and Ti/Al 3003 composite materials were respectively used as tension members in two different structure samples. Single-material copies of the dual-material structures were fabricated using Al 3003 for load-carrying capability comparison. The results of the load tests carried out shows that the dual-material structures could withstand much higher loads than similar structures entirely made of the matrix Al 3003 material. This is an indication that UAM can be effectively used to fabricate multi-material engineering structures.

Description: A method is described in this paper for measuring the spindle rotation error and a technique for separating the eccentric error caused by setup error of the master cylinder. The system consists of two non-contact capacitance sensors used to measure the radial displacement of the rotating master cylinder and an LMS Test.Lab used to collect the measurement data. LMS Test.Lab offers a complete engineering solution for rotating machinery. Based on our experimental research, it indicates that this system can be used to measuring the spindle rotary error at different speeds. It is also verified the feasibility of the error separation methods developed in this paper.