Abstract: Quantities AZ80 magnesium alloy billets were compressed with 60% height reduction on hot process simulator at 200,250,300,350,400,450°C under strain rates of 0.001, 0.01, 0.1,1 and 10s-1.The processing maps based on the Dynamic Material Modeling (DMM) were constructed, which is useful to analyze the deformation mechanism and the destabilization mechanism of AZ80 alloy. If the mechanical property of AZ80 alloy is taken into consideration, the optimal deformation processing parameters from the processing maps are the deformation temperatures ranging from 300 to 350°C and strain rates ranging from 0.001 to 0.01s-1. Meanwhile, a flow stress model with eight parameters is used to characterize the dynamic recrystallization strain softening of AZ80 alloy.
Abstract: In this investigation a study on vacuum diffusion bonding of as-extruded AZ31 magnesium alloys was carried out according to atomic diffusion theory. The bonding quality of the joints was checked by microstructure analysis, shear test and micro-hardness testing. The results showed that the diffusion temperature and holding time had a great effect on the the bonding quality of the joints. The maximum of joint shear strength was 76.2MPa with the bonding temperature being 420°C and the holding time reaching 90min.
Abstract: Within a micromechanical framework, the effect of surface energy is taken into account to explore the size-dependent yield criterion of nanoporous materials under complex stress states. A theoretical picture of the yield behavior on an octahedral plane is illustrated as functions of the surface properties and void size. The prominent size dependence of the yield criterion of nanoporous materials highlights the importance of the surface effect in analyzing the strength of nanostructured materials. The results demonstrate a fundamental framework to extend continuum strength theories to the nanoscale with substantial surface effect, which may be useful for evaluating the mechanical integrity of nanostructured materials.
Abstract: Solution for length-limited thin-walled cylindrical shells' deformation and stress state under non-axisymmetric uniform line load and concentrated load conditions, such as containments of rail guns, is a common engineering problem. Based on fundamental equations of the above problem, load function and displacement function are presented, and displacement and stress analytic solutions are obtained by Galerkin Method in this paper. The analytical solutions are verified by comparing them with ANSYS numerical solutions of an example problem. The results of this paper can be served as a reference for analytic solutions and engineering designs of non-axisymmetric cylindrical shells.
Abstract: The traction behavior of high-speed lubricating grease 7007 was tested on a self-made test rig. The changes of traction coefficients with velocity, temperature and load were got from the experimental results. The rheological parameters were received on the basis of experimental data. The formula of traction force of high-speed lubricating grease 7007 was based on the correctional T-J model. The result shows that the traction coefficients of high-speed lubricating grease 7007 based on correctional T-J mode agree well with the experimental data.
Abstract: The micro-machined gyroscope is a kind of typical micro-electro-mechanical sensor, its typical working mode is electrostatic drive and comb capacitive detection. As for as the transverse detection capacitance structure now commonly used, we find out that the relationship between capacitance variation and displacement is nonlinear through analyzing its detection capacitance. This nonlinearity will greatly affect the dynamic performance of micro-machined gyroscope.
Abstract: A novel technology is studied in this paper to make photosensitive resin grinding wheel based on layered manufacturing technology. The bond strength among resin layers is analyzed. An effective measure is proposed to improve the bond strength among resin layers of the grinding wheel. We add magnetic abrasive particles into the liquid resin to get rough surface and increase contact area by action of magnetic force. Some experiments are curried out for testing shear strength of resin with magnetic abrasive under different conditions. Results show that this method had a significant effect in improving the bond strength among layers of new grinding wheel.
Abstract: In this study, the elastic buckling behavior of clamped laminated composite cylindrical shells under external pressure was studied. The Finite Element Method (FEM) was used to predict the critical elastic buckling pressure behavior when composite cylindrical shells were subjected to external pressure. The edges of the cylindrical shell ends were completely constrained to simulate clamped end conditions. The influences of parameters such as wall thickness, fiber angle, number of layers and L/R ratio of laminated composite cylindrical shells on critical buckling pressure were studied. It has been found that the under external pressure, the thickness and the fiber angle of the layers have the most significant effect on the critical buckling pressure.
Abstract: In this study, the buckling behavior of optimum laminated composite cylindrical shells subjected to axial compression and external pressure are studied. The cylindrical shells are composed of multi orthotropic layers that the principal axis gets along with the shell axis (x). The number of layers and the fiber orientation of layers are selected as optimization design variables with the aim to find the optimal laminated composite cylindrical shells. The optimization procedure was formulated with the objective of finding the highest buckling pressure. The Genetic Algorithm (GA) and Imperialist Competitive Algorithm (ICA) are two optimization algorithms that are used in this optimization procedure and the results were compared. Also, the effect of materials properties on buckling behavior was analyzed and studied.