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During the high-speed forming processes, the metallic sheets are usually deformed under the biaxial tensile condition. The strain rate of metallic sheets often exceeds 102 s− 1. It is essential to determine the strain-rate-sensitive hardening model of metallic sheets for accurate numerical simulation of the high-speed forming processes. Thus, an electromagnetic hydraulic bulge experiment is proposed to determine the strain-rate-dependent hardening model of metallic sheets under the biaxial tensile condition with the strain rate of 102 s− 1. It is convenient to numerically simulate the electromagnetic hydraulic bulge processes. Hence, the strain-rate-dependent hardening models of metallic sheets can be determined by the inverse identification procedure of updating the numerical simulation. The electromagnetic hydraulic bulge experiments of SUS304 stainless steel sheet and AA5052-O aluminum alloy sheet were performed for the inverse identification of Johnson-Cook hardening model. The discrepancy between the experimental results and numerical simulation was minimized by optimizing the parameters of strain-rate-dependent hardening models. The dynamic flow stress curves of SUS304 stainless steel sheet and AA5052-O aluminum alloy sheet were higher than the static ones. However, the AA5052-O aluminum alloy sheet exhibits more significant strain-rate hardening effect than the SUS304 stainless steel sheet. The inverse identification of strain-rate-dependent hardening model of metallic sheet was validated by comparing the simulated and experimental results of electromagnetic micro-hydroforming of micro-channel. [ABSTRACT FROM AUTHOR]

In this paper, the effects of process parameters of Magnetic pulse welding (MPW) on the mechanical properties and microstructure of dissimilar metal joints of 6063-O and 20 steel tubes were investigated according to experiments. The experimental results show that the tensile strength of MPW joint is higher than that of the aluminium tube when the discharging energy of MPW attaches a certain value as well as the process parameters are reasonable, in which the mechanical joining was happened. Through the FEM analysis and experiments verification, the metallurgical joints were obtained with the moderate discharging energy, reasonable impact angle and radial gap. The results of micro hardness test show that the transition zone has a big change because the grain structure of joints in the interface was refined.

To clarify the densification law of dry pressed MgTiO3 ceramic body during pressureless sintering, SOVS model (Skorohod‐Olevsky Viscous Sintering model) modified with creep characteristics was embedded into finite element software Abaqus. The selected model can effectively express the grain boundary characteristics and densification mechanism. The change law of relative density, shrinkage rate, sintering stress, and grain size of MgTiO3 cylindrical specimens was investigated by the above numerical simulation method. It showed that the average relative density of ceramic body rose from 60% to 97%, and the shrinkage rate respectively reached 17.28% and 11.99% in axial and radial direction. The average grain size increased from 1 to 6 μm. In order to verify the accuracy of the simulation results, corresponding sintering experiments on cylindrical specimens were carried out to obtain actual sintering densities and shrinkage rates. It showed that the errors of relative density and shrinkage were below 5% and 2%. Grain growth trend was also basically consistent with the simulation results. After that, the above numerical simulation method was applied into the prediction of fabricating MgTiO3 filter with complex structure. Therefore, the present work provided a reliable numerical simulation method to predict the densification behavior of MgTiO3 ceramics during the pressureless sintering process, which was helpful to design and fabricate microwave dielectric products. [ABSTRACT FROM AUTHOR]

Mechanical properties and curing depth of bisphenol‐α‐glycidyl methacrylate/triethylene glycol dimethacrylate‐based dental composites were systematically investigated by site‐specific nanoindentation tests. Effects of filler (20‐nm silica nanoparticle) content on the nanohardness and elastic modulus of the composites were studied in comparison with micromechanics theoretical models. Results showed that the incorporation of the silica nanoparticles at low contents (up to 5.66 vol%) significantly increases the hardness and elastic modulus of the dental composites by up to 65% and 30%, respectively. It was found that the Counto model gave good predictions for the composite modulus as a function of filler content. For the specific composites studied here, the depth of cure increases approximately linearly with the filler content, which may be ascribed to the stronger reinforcement effect of the silica nanoparticles on the dental composites at a higher particle content. These results combined demonstrate the effectiveness of silica nanoparticles as the reinforcement for dental restorative materials even at small volume fractions. POLYM. COMPOS., 40:1473–1480, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]