We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell ...We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell at ambient temperature. The ratio of differential stress to shear modulus （t/G） is found to remain constant above -60GPa, indicating that the Ta starts to experience macro yield with plastic deformation at this pressure.Combined with independent constraints on the high-pressure shear modulus, we find that the Ta sample could support a differential stress of -4.67 GPa when it starts to yield with plastic deformation at -60 CPa under unlaxial compression. The differential stress in Ta ranges from 0.216 GPa to 4.67CPa with pressure increasing from 1 GPa to 60GPa and can be expressed as t=0.199（33）＋0.075（1）P, where P is the pressure in GPa. A maximum differential stress as high as -5.37 GPa can be supported by Ta at the high pressure of -80 GPa. In addition, we investigate the texture of Ta under nonhydrostatic compression to 80 GPa using the software package material analysis using diffraction. It is proven that the plastic deformation due to stress under high pressures is responsible for the development of texture.展开更多
The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happe...The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation;when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher.展开更多
The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decreas...The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.展开更多
It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper...It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd （doubler plate to chord wall thickness ratio） and ld/d1（dubler plate length to brace diameter ratio） on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10875142 and 11079040the Chinese Academy of Sciences under Grant Nos KJCX2-SW-N03 and KJCX2-SW-N20
文摘We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell at ambient temperature. The ratio of differential stress to shear modulus （t/G） is found to remain constant above -60GPa, indicating that the Ta starts to experience macro yield with plastic deformation at this pressure.Combined with independent constraints on the high-pressure shear modulus, we find that the Ta sample could support a differential stress of -4.67 GPa when it starts to yield with plastic deformation at -60 CPa under unlaxial compression. The differential stress in Ta ranges from 0.216 GPa to 4.67CPa with pressure increasing from 1 GPa to 60GPa and can be expressed as t=0.199（33）＋0.075（1）P, where P is the pressure in GPa. A maximum differential stress as high as -5.37 GPa can be supported by Ta at the high pressure of -80 GPa. In addition, we investigate the texture of Ta under nonhydrostatic compression to 80 GPa using the software package material analysis using diffraction. It is proven that the plastic deformation due to stress under high pressures is responsible for the development of texture.
基金supports by the National Natural Science Foundation of China(Grant No.52172353 and 52202431).
文摘The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation;when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher.
基金funded by General Motors Global Research and Development Center(Grant No.:PS21025708)
文摘The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.
文摘It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd （doubler plate to chord wall thickness ratio） and ld/d1（dubler plate length to brace diameter ratio） on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.
