ALBERT

Notes: Accurate stress intensity solutions for multiple site damage (MSD) cracks in rivetedstiffened panels are difficult to determine due to geometric complexity along with variations in rivetload transfer and corrosion, especially the interaction of MSD cracks. A methodology was proposedfor efficiently depicting rivet in stiffened panel using finite elements. Rivet material properties weredetermined based on an empirical force-displacement relationship, for highly refined rivet model aswell as for idealized spring element representations of rivets. Parametric studies of panels with amiddle crack and a central stiffener indicate that rivets can provide comparable load transfer andrelative displacement if the rivets closed to the crack are explicit modeled. Using idealizedcombination of explicitly and spring element representations of rivets, the stress intensity factors(SIFs) for uncorroded and corroded one-bay stiffened panels were predicted. The results show that theeffect of MSD and thinning of the sheet is to increase substantially SIFs values compare to that of asingle crack without corrosion. But the SIF is insensitive to corrosion of stiffener. The particular rivetmaterial has relatively little effect on SIF values, while the rivet diameter has a significant effect

Notes: It is innovative to combine abrasive jet machining and conventional grinding together inthis thesis. And it realizes a new sort of grinding wheel restricted with abrasive jet processing. Thethree-dimensional mathematical model of hydrodynamic pressure of wedge-like grinding zonebetween grinding wheel and workpiece on abrasive jet finishing with wheel as restraint wasestablished, and the finite elements simulation analysis for the hydrodynamic pressure wasimplemented. This paper investigated the liquid hydrodynamic pressure, the regularities ofdistributing of velocity, influencing factors and the affection for processing technique

Notes: Based on the research achievements of the mechanical properties of concrete at uniaxial compression and steel at uniaxial tension after exposed to high temperatures, the axisymmetric- triaxial-compressive stress-strain relationships of concrete and multiaxial stress-strain relationships of steel after exposed to high temperatures was suggested. Based on continuum mechanics, the mechanical model of concentric cylinders of circular steel tube with concrete core of entire section loaded after exposed to high temperature was determined. By applying Elasto-Plastic Analysis Method, theoretical calculation formulas for composite elastic modulus and composite stress-strain relationships of concrete-filled circular steel tubular (CFST) stub columns were proposed and a FORTRAN program was developed and the load-axial strain relationships of CFST stub columns after exposed to high temperatures were analyzed. The analysis results were in reasonable agreement with the experiment ones from references

Notes: Smart concrete technology provides a new alternative way for health monitoring of reinforced concrete structures. In this paper, the piezoresistivity of two kinds of smart concrete filled with carbon black or carbon fiber was studied, and two types of embedded sensors were fabricated using the smart concrete with favorable piezoresistivity. The sensing performance, the measuring methods and the response to environmental temperature and humidity of embedded sensors were investigated. A compensation circuit was incorporated to reduce the effect of temperature and humidity on the output of embedded sensors. The sensors were embedded in concrete beams and columns to monitor the structural compressive strain under field conditions. Experimental results indicate that the embedded sensors fabricated using smart concrete filled with carbon black or carbon fiber feature favorable sensing performance (gauge factors are 55.28 and 138 respectively). The self-sensing concrete components embedded with these sensors can realize the monitoring of their local compressive strain. It therefore can be concluded that the prepared smart concrete and the developed embedded sensors have great potential to be used for health monitoring and damage assessment of concrete structures

Notes: Shape memory alloy (SMA) has many potential applications as an actuator in smart material systems due to its abilities of shape memory, pseudo-elasticity, high damping and wear resistant. In this paper, a smart concrete beam has been developed by taking advantage of the shape memory effect of SMA and the characteristic of applying large forces on the resisting member in the transformation of SMA on heating. Deformation behavior and influence of factors on the deformation behavior of SAM smart concrete beam were investigated experimentally. Actuation mechanics of SMA was analyzed. Experimental results show that SMA wires significantly increase structural survivability and allow structural to recover from residual deformation by damaged earthquake and typhoon, and the crack almost closes completely after electrically heating the SMA wires. The number or areas of SMA wires has no influence on the tendency of deformation during loading and the tendency of reversion by heating. An increasing of the initial pre-strain of SMA wire can significantly improve the capacity of self-restoration of SMA concrete beams, but the steel main bars play a very negative role in reducing residual deformation

Notes: The influence of leucite on dental porcelain properties is investigated in this paper. The nanosized leucite powder prepared by sol-gel method was added into a low-fusing temperature frit to fabricate dental porcelain fused to metal. The porcelains with different leucite contents were sintered at the temperatures ranging from 780° to 900°C. The flexural strength and the thermal expansion coefficient (TEC) of the dental porcelain containing leucite particles are evaluated. The micro- structure and phases of the porcelain are characterized and the mechanism that nanosized leucite particles strengthening the porcelain is discussed

Notes: HfB2-HfC-SiC ultrahigh temperature ceramics (UHTCs) were prepared and characterized inthis paper. It is showed that the densities of the HfB2-HfC-SiC reach 98.5% of the theory density. Theroom temperature compressive properties of the HfB2-HfC-SiC are good, while those at high temperaturedecrease rapidly. The volume expansion ratio monotonously increases (up to 2.35% at 2300°C) withincreasing temperature. Furthermore, with increasing temperature, the average linear expansioncoefficient hardly changes, while the instant linear expansion coefficient decreases first, and followed byan increase. The minimum value of the instant linear expansion coefficient is 5.65×10-6/K at 900°C andthat of the mean linear expansion coefficient is 7.39×10-6/K at 1340°C. HfB2-HfC-SiC were burned withthe plasma arc heater. After 8-second ablation, part of the SiC particles melted and spurted from thecomposites, and holes appeared

Notes: Three kinds of coatings had been prepared on the surface of 45CrNi steel plates using lasercladded technique by adding Mo and CeO2 into the Nickel-based alloys. The wear behaviors of thesethree kinds of coatings in sliding against Al2O3 grinding ring were investigated by using a MM-200Wear Tester. The results indicated that the addition of both Mo and CeO2 could improve the wearresistance of Nickel-based alloy coatings. If the original Nickel-based alloy coating was taken as thestandard sample, the relative wear resistances of Mo-modified and Ce-modified coatings are 1.31 and7.54 respectively, and the coefficients of friction appreciably decreased. SEM images of the wornsurface of the coatings showed that the wear of original Nickel-based alloy coating was dominated bythe mechanism of micro-cutting, and the Mo-modified coating and Ce-modified coating had a featureof fatigue wear in addition to micro-cutting. In sliding, the wearing resistance of Ce-modified coatingwas higher than the other two. The wear test results were closely related to the microstructures of thecoatings

Notes: The tensile plastic strains and the residual tensile stresses caused by heat input during thelaser cladding process are the main reasons for the cracking. In this paper, the laser cladding processon a type 1045 steel plate with Ni60 powder feeding was investigated and simulated by finite elementmethod to analyze the temperature field and stress-strain field of the laser cladding process. In thetemperature field model, the main considerations were given to the heat source data and the thermalboundary conditions. The interactions of laser, powders and base metal were mainly considered in theapplication of the heat source data. The relationship between the heat convection coefficient of workpiece surface and the temperature variation was mainly considered in the application of thermalboundary conditions. In the stress-strain field model, the main consideration was given to theelastic-plastic characteristics of the materials, and the materials were assumed to be linearstrain-strengthened. Moreover, the thermal stresses could be solved through the temperature field andwere subsequently applied directly to the stress-strain field model as loads. Besides the temperaturevariations, the stress variations and the strain variations of some critical points (including the crestpoint of the cladded layer and intersection point of cladded layer and plate) were also obtainedthrough the finite calculation. The temperature variations show that the heating curve isapproximately a straight line while the cooling curve is like an arm of a hyperbola. The strainvariations show that the thermal strain has a variation trend similar to the temperature variations. Theelastic strain of each point is very low when compared to the plastic strain. The calculated resultsshow that the tensile plastic strain of the crest point on the coating is the greatest in the claddingdirection and the tensile stress in this direction of this point is great too. As a result, transverse crackcan be easily initiated at the crest of the coating. While the tensile plastic strain at the intersectionpoint of the base metal and coating is the greatest in the direction vertical to the plate thickness, thestress at this point (in the same direction) is compressive. Therefore, the intersection points tend toform a limited toe crack which can not grow

Notes: Based on the fractal theories, using image processing software (IPS) to handle the scan electronmicroscope photos of particles, this paper gives a simple and applied method to pick up the boundaryline’s fractal dimension (FD) of particles’ projective numerical images. Take example for Al(OH)3material particles, adopting respectively relative Box-counting (BC) method and relative C-S method, wehave calculated the boundary FD values of the research objects and compared FD with other quantitativetoken parameters, which shows FD is a sort of more refined quantitative token parameter. Finally,utilizing the method of Generator, we get some fractal figures which have nearly same FD values withAl(OH)3 material particles, utilizing that we can simulate and analyze the complexity of the boundary andsurface micro-topography of Al(OH)3 material particles