Papers by Author: Wei Dong Song

Abstract: A coupled model of damage and plasticity is presented to describe the dynamic behaviors of TiC-particulate reinforced titanium matrix composites (TiCp/TMCs) subjected to shock loadings. The TiCp/TMCs are assumed as homogeneous continuum with pre-existing micro-cracks and micro-voids. Damage to TiCp/TMCs is caused due to micro-crack nucleation, growth and coalescence, and defined as the probability of fracture at a given crack density. In terms of crack growth model, micro-cracks are activated, and begin to propagate gradually. When crack density reaches a critical value, the smashing destroy takes place. The model parameters for TiCp/TMCs are determined using plate impact experiments. Comparison with the test results shows that the proposed model can give consistent predictions of the dynamic behaviors of TiCp/TMCs subjected to impact loadings.

Abstract: A meso-mechanical constitutive model of TiC particle reinforced titanium matrix composites (TiC/TMCs) under impact loading is established to investigate the mechanical behavior of TiC/TMCs. Based on Eshelbys equivalent inclusion theory and Mori-Tanakas concept of average stress in the matrix, the compliance tensor is formulated. By adding nucleation and growth crack models, the influences of micro-cracks on compliance tensor and damage evolution are examined. Finally, a one-dimensional dynamic constitutive model subjected to impact loading is presented to explore the mechanical behavior of TiC/TMCs.

Abstract: The microstructure evolution of TiAl intermetallics with different microstructures loaded under different strain rates and temperatures was investigated. The results showed that the deformation twinning dominated the deformation process under high strain rate, while dislocation slip was another dominating deformation mode under quasi-static loadings. The proportion of twinned grain increased with the increased strain rate. In Duplex TiAl, the plastic deformation was mainly found in equaxied grains and seldom found in lamellar grains.

Abstract: The microstructure evolution of Ti-46.5Al-2Nb-2Cr with different microstructure types loaded under a large range of strain rates and elevated temperatures is investigated by TEM. The results show that deformation twins are the main deformation mode under high strain rate loadings and both ordinary dislocation and super-dislocation are the additional modes under quasi-static loadings. The proportion of twinned grains increases with the increased strain rates.

Abstract: The high-temperature mechanical behavior of TiC particulate-reinforced titanium matrix composites was investigated at elevated strain rates. The effects of the temperature and strain rate on the mechanical properties of the composites were analyzed. According to Arrhenius flow stress model, a dynamic-high-temperature constitutive relation of TiC particulate-reinforced titanium matrix composites was established.

Abstract: Fixed point iteration method for multi-particle unit cell’s boundary condition is presented. On the basis of this method, the macroscopic effective material parameters can be obtained from a microscopic point of view. Multi-particle unit cell models containing some important microstructure characteristics of TP-650 titanium matrix composites are established. The real displacement constrained conditions are applied on the multi-particle unit cell using this method, and the mechanical properties and fracture behaviors of the composites under tensile loading are simulated. A good agreement was obtained between the experimental results and the numerical predictions, which verifying the rationality of the FE models based on fixed point iteration method.

Abstract: SEM experimental system was employed to investigate the fracture behavior of particle reinforced metal matrix composites (91%wt tungsten alloys) by in-situ experiments. The fracture patterns of tungsten alloys under tensile loading were examined. Multi-particle unit cell models containing some important microstructure characteristics of tungsten alloys were established. By using fixed point iteration method, the displacement constraint conditions were applied on the multi-particle unit cell and the mechanical properties of tungsten alloys under tensile loadings were simulated. Comparison of the experimental results and the numerical predictions shows a good agreement between them, verifying the rationality of the FE models using the fixed point iteration method.

Abstract: The plate impact experiments have been conducted to investigate the dynamic behavior of 91W-6.3Ni-2.7Fe. Lagrangian analysis technique was introduced to discuss the mechanical properties of the tungsten alloys under high strain rate and the stress-strain curves of the tungsten alloys were given. Based on the experimental observations, the three-dimensional finite element models of projectile and tungsten alloy target are established by adopting ANSYS/LS-DYNA, Dozens of cases were performed to investigate the dynamic mechanical behavior of tungsten alloy target under impact loading. A good agreement between numerical predictions and experimental results was obtained, which suggests that the finite element model is efficient and credible to simulate the mechanical properties of tungsten alloys.

Abstract: The plate impact experiments have been conducted to investigate the dynamic behavior of 91W-6.3Ni-2.7Fe with three kinds grain sizes of 1− 3μm, 10 −15μmand 30 − 40μm . The stress-time history curves at different Lagrangian positions were obtained for tungsten alloys at different impact velocities. Lagrangian analysis technique was adopted to discuss the mechanical properties of the tungsten alloys under high strain rate. SEM was introduced to analyze the microstructure properties of tungsten alloys. The influence of grain size on the dynamic behavior of tungsten alloys under high strain rate was obtained and the stress-strain curves ( 4 5 1 10 ~ 10 s− ) of the tungsten alloys were given.

Abstract: The tensile tests and the three-point bending tests have been conducted to investigate the crack initiation and propagation and the fracture behavior of 91W-6.3Ni-2.7Fe with three kinds grain sizes of 1~3μm, 10~15μm and 30~40μm. SEM was introduced to analyze the grain sizes, the micro-defects, the deformations and the fracture behaviors of tungsten alloys. The test results show that under the same loading conditions, the crack initiation and the crack propagation are not only related to grain size, but also related to the contiguity of tungsten grains and the interface between the tungsten grains and the matrix.