Papers by Author: Jian Xun Zhang

Abstract: Structural response of pin-supported metallic foam core sandwich beam is theoretically investigated. Effects of local denting and core strength and interaction of bending and axial stretching are considered in analysis. A rigid-plastic beam-on-foundation is employed to consider local denting deformation. The local denting continues during the overall deformation of sandwich beam. It is shown that upon neglecting the effect of local denting, the load-carrying capacity and energy absorption of sandwich beam may be overestimated, and the normal axial (membrane) force associated with plastic stretching substantially stiffens the sandwich beams.

Abstract: The resistance of metallic sandwich plates to blast loading is studied in this work. Two typical cores, i.e. trapezoidal plate core and metallic foam core are considered in the analysis. The normal and longitudinal compressive stresses of the trapezoidal plate core are analytically and numerically obtained. Large deflection and resistance of metallic sandwich plates to blast loading are numerically analyzed. The results are compared with that of monolithic solid plates made of the same material and having equivalent weight. It is shown that the well-designed sandwich plates possess higher resistance to blast loading than monolithic solid plates.

Abstract: This paper set a numerical calculation model with local mesh refined for laser welding of titanium alloy applying body heat source model which can accurately describe the shape of keyhole and molten pool on laser welded joint. It calculated the change patterns of the temperature distribution and heat conduction in region of gas, liquid, and solid phase under different laser energy density on the stage of heating and cooling. The results showed that with the increase of the laser energy density t, the dimension of keyhole and molten pool, the temperature gradient and the duration of gas and liquid phase on the stage of heating and cooling are all expected to increase. Under the same laser energy density, temperature gradient has a maximum value in the region of gas phase, secondly is in liquid phase, and minimum in solid phase.

Abstract: An in-house developed FE code, based on the idea of Iterative Substructure Method, was used to evaluate the effectiveness of fixture and pre-strain for reduction of welding distortion in a fillet welded structure. Comparison between the simulation results and experimental results has been performed to validate the basic FE model. Effects of two fixture conditions and various prestrain schemes were analyzed. The simulation results show that appropriate fixture can greatly reduce angular distortion of the work-piece and results in an appreciable reduction in residual deformation and the application of pre-strain can significantly reduce the residual distortion.

Abstract: Gas shield Tungsten Arc Welding (GTAW) is an important process method in material processing. Welding quality is vital for the product quality. It is an important way to improve the quality of product by raising the personal capability and handling technique of the welder. In this investigation, because of the deficiency in classic welding training scheme, some new technology were introduced into classic welding training field to improve the efficiency of welding training and reduce training cost. A computer simulation system that can be used to train primary welders was developed combined with three-dimensional stereoscopic vision and API interface of OpenGL, virtual reality is the kernel technology. In this system, welders were trained not in the real operating environment but in the virtual environment where has experience personally effect that simulated by computer. There is unnecessary with welding material and welding energy in virtual environment simulated by computer. It has highly automatic and intelligent and lower required to welding teachers. It is healthy to welder because that intensive arc and harmful dust are disappeared in virtual environment. It is a lower cost and high efficiency method by use of virtual training system to training new welder.

Abstract: The effects of the welding mechanical heterogeneity on the damage evolution of notched round-bar tensile specimens were investigated numerically using a fully coupled elastic-plastic damage finite element method. Some parameters reflecting the welding mechanical heterogeneity such as strength mismatching, rupture strain and weld metal width were taken into account to study their effects on the damage evolution of the weld metal. The calculation results show that the damage evolution of the weld metal is affected strongly by the welding mechanical heterogeneity. The damage evolution of the weld metal becomes larger with the decrease of both the rupture strain and yielding stress of the base metal. The effects of the mechanical properties of the base metal on the damage evolution of the weld metal decreases with the increase of the weld metal width.