Applied Mechanics and Materials Vols. 37-38

Abstract: In this paper, the technology of self-piercing riveting (SPR) with half-hollow rivets was investigated using experiments and numerical simulations with 6063 aluminum alloy sheet. The failure mechanism of SPR aluminum alloy sheet was indicated with the shear model and tear model, which could accurately simulate the sheet structure. Based on the simulation results with finite element method (FEA), the effect of die geometry on static mechanical characteristics, including punch load, failure load and failure displacement, was analyzed. It was discovered that the die pip height and sheet thickness should be designed synthetically for optimal tensile behavior.

Abstract: The simulation of joint is pivotal for car body structural analysis in concept design phase. The detail simulation method was implemented by solving the detail joint model using non-decoupling method. The detail information was afforded about joint detail modeling and the process of non-decoupling. The process of solving the parameters of joint was also described with equations. By the solved parameter values, the joint concept was built with ball hinge elements and spring elements. At last, a comparison between concept model with detail joint simulation and detail model of car body shows that the detail simulation method in this paper is feasible and accurate.

Abstract: It is frequently reported by customers that the lower-left and lower-right wheels in the load fork mechanism of a kind of forward-type stacker designed based on static strength analysis are abraded faster than expected. In this paper, we studied by means of kinetics analysis and simulations the forces applied on parts of the fork mechanism. The simulation results show that the maximum values of instantaneous forces during operations are much higher than those derived based static force analysis, and thus explained the reason of the above-mentioned abnormal abrasion. The results also mean that static force analysis is not suitable for part strength design. Instead, one shall adopt kinetics analysis to explore the instantaneous forces in design.

Abstract: Combined with the structural design of left-shore drainage aqueducts in China South-to-north Water Transfer Project, the structure of cast-in-situ reinforced concrete flume (RCF) with wide and shallow drainage section superposed on longitudinal precast prestressed concrete beams (PPCBs) was drafted. The 3D finite element models were built to study the normal service behaviors of the aqueduct with or without segregating asphalt layer between RCF and PPCBs. The results show that the segregating asphalt layer changes the structural compositions of aqueduct subjecting water loads and results in some effects on loading capacities of the PPCBs and the RCF, such as the larger displacement and tensile stress of PPCBs, the many longitudinal sections of subplate in whole tensile state with larger tensile stresses and the larger vertical tensile stresses at internal surface of sidewall. It provides valuable reference for designing the same kind of aqueduct.

Abstract: This paper presents a new manufacturing technology for machine tool beds, which is composed of high stiffness epoxy concrete structure faces and lower cost steel fiber cement concrete core. After steel fiber cement concrete core is poured, epoxy concrete structure faces are poured. The technology is first applied in manufacturing of CKA6150 CNC lathe bed. Through comparing with cast iron machine tool bed and epoxy concrete machine tool bed, it is estimated by five elements value green estimate theory. The result demonstrates that composite concrete machine tool bed not only has high characteristic and lower energy cost but also meets requirements of green manufacturing.

Abstract: A fourth order transmission error was employed to improve the stability and tooth strength of circular-arc curvilinear cylindrical gears. The coefficient of fourth order polynomial curve was determined, the imaginary rack cutter which formed by the rotation of a head cutter and the imaginary pinion were introduced to determine the pinion and gear tooth surfaces, respectively. The numerical simulation of meshing shows: 1) the fourth order transmission error can be achieved by the proposed method; 2) the stability transmission can be performed by increasing the angle of the transfer point of the cycle of meshing; 3) the tooth fillet strength can be enhanced.

Abstract: The mechanical analysis of a novel plywood formwork structure with steel frame was studied with finite element method systematically. By optimizing the parameters of the section shape, node position and the number of formwork heel, a kind of the optimization design scheme was presented. Less building construction materials and better mechanical property was accomplished by the scheme. By contrasting the optimization results with experimental results, the design method is valuable.

Abstract: The basic feasibility of laser fusion welding for prefabrication and assembly of zinc-coated sheet steel auto body components has been demonstrated in a significant number of prior studies. For trouble-free high volume manufacturing, however, one leading key technical concern remains incompletely resolved. In lap or similar weld joint geometries, venting of trapped Zn vapour can seriously disturb the molten weld pool and give rise to gross fusion defects. In this paper, the technical status of the issue has been reviewed, and various experiments were planned to explore Al foil as an interlayer and dual beam laser for suppressing Zn vapour. The results have shown that the welding processing is very sTable when the lap 1+1 mm sheet steel is welded by using Nd-Yag laser at 3KW power and 4m/min travel speed (defined as single beam) with 75μm Al foil as interlayer. However, if first using 2KW power and 4m/min travel speed, secondly using 3KW power and4m/min travel speed (defined as dual beam), only 25 μm Al foil can stabilize welding fusion pool. It is found that Al foil just store the Zn vapour in the single beam method and cannot mix with Zn to form Al-Zn binary alloy, because the laser heating is too fast that Zn has been vaporized before Al was melted. But Al can mix with Zn to form Al-Zn binary alloy in the dual beam method, therefore, the boiling temperature is raised to about 1600°C. So that, in laser lap welding of Zn coated (galvanized) sheet steel, the Al-Zn alloy will be more effective than Al metal for stabilizing welding process.

Abstract: Gear honing with globoid honing worms is seldom used because it has no distinct advantages to honing with internal geared honing rings. The paper puts forward a new process to honing gear with globoid honing worms on hobbing machines. First the globoid honing worm is profiled by diamond dressing gears, which has the same geometric parameters with the machined gears. Then the profiled globoid honing worm is used to hone workpieces. Both the profiling process and honing process are implemented on same hobbing machines. Meshing and Tooth contact analysis of globoid honing worm profiling has been considered. Meshing equation of profiling process and equation of globoid honing worm tooth flank after profiling are obtained. Experiment testified that it is an applied process and has many advantages.

Abstract: The initiation, propagation and broadening of crazes in polycarbonate were studied with the aid of polarizing microscopy. A loading instrument supplying uniaxial stretch is designed to match polarizing microscopy. With polarizing microscopy, online observations of crazes and stress field can be done simultaneously. Crazes appear in bilateral anteriority of the crack tip and direction of length is perpendicular to the maximum principal stress. Stress on the boarder of the crazing zone is taken as the initiating point of the crazes and length to time of crazes follows exponent law. The initiation, propagation and broadening of crazes is a time-dependent process.