The problem of scattering of SH-wave by a circular cavity and an arbitrary beeline crack in right-angle plane was investigated using the methods of Green's function,complex variables and muti-polar coordinates.Fir...The problem of scattering of SH-wave by a circular cavity and an arbitrary beeline crack in right-angle plane was investigated using the methods of Green's function,complex variables and muti-polar coordinates.Firstly,we constructed a suitable Green's function,which is an essential solution to the displacement field for the elastic right-angle plane possessing a circular cavity while bearing out-of-plane harmonic line source load at arbitrary point.Secondly,based on the method of crack-division,integration for solution was established,then expressions of displacement and stress were obtained while crack and circular cavities were both in existence.Finally,the dynamic stress concentration factor around the circular cavity and the dynamic stress intensity factor at crack tip were discussed to the cases of different parameters in numerical examples.Calculation results show that the crack produces adverse engineering influence on both of the dynamic stress concentration factor and the dynamic stress intensity factor.展开更多
The role of oxides in the formation of hole defects in friction stir welded joint of 2519-T87 aluminum alloy has been investigated by using optical microscope, scanning electron microscope, electron backscatter diffra...The role of oxides in the formation of hole defects in friction stir welded joint of 2519-T87 aluminum alloy has been investigated by using optical microscope, scanning electron microscope, electron backscatter diffraction and electron probe microanalyzer to examine the distribution of oxides and the features of hole defects, and using ABAQUS 3D thermo-mechanical coupling finite element model based on arbitrary Lagrangian-Eulerian method to simulate the material flow behavior. Oxides exist at the edge of tunnel hole and in the micropores in the joint. Based on distribution of oxygen and material flow behavior, it is believed that the oxides on the surface of the alloy tend to flow down into the bulk along the flow direction of plastic material during friction stir welding, aggregate in the weak region of material flow at the intersection of the shoulder affected zone and the stir pin-tip affected zone, and consequently prevent the material from contacting and diffusing. Due to the insufficient material flow and therefore the small plastic deformation,the pressure is not high enough to compress the accumulated oxides, resulting in hole defects.展开更多
文摘The problem of scattering of SH-wave by a circular cavity and an arbitrary beeline crack in right-angle plane was investigated using the methods of Green's function,complex variables and muti-polar coordinates.Firstly,we constructed a suitable Green's function,which is an essential solution to the displacement field for the elastic right-angle plane possessing a circular cavity while bearing out-of-plane harmonic line source load at arbitrary point.Secondly,based on the method of crack-division,integration for solution was established,then expressions of displacement and stress were obtained while crack and circular cavities were both in existence.Finally,the dynamic stress concentration factor around the circular cavity and the dynamic stress intensity factor at crack tip were discussed to the cases of different parameters in numerical examples.Calculation results show that the crack produces adverse engineering influence on both of the dynamic stress concentration factor and the dynamic stress intensity factor.
文摘The role of oxides in the formation of hole defects in friction stir welded joint of 2519-T87 aluminum alloy has been investigated by using optical microscope, scanning electron microscope, electron backscatter diffraction and electron probe microanalyzer to examine the distribution of oxides and the features of hole defects, and using ABAQUS 3D thermo-mechanical coupling finite element model based on arbitrary Lagrangian-Eulerian method to simulate the material flow behavior. Oxides exist at the edge of tunnel hole and in the micropores in the joint. Based on distribution of oxygen and material flow behavior, it is believed that the oxides on the surface of the alloy tend to flow down into the bulk along the flow direction of plastic material during friction stir welding, aggregate in the weak region of material flow at the intersection of the shoulder affected zone and the stir pin-tip affected zone, and consequently prevent the material from contacting and diffusing. Due to the insufficient material flow and therefore the small plastic deformation,the pressure is not high enough to compress the accumulated oxides, resulting in hole defects.
