Because of the generated residual stress after applying cold expanded technique with split sleeve, fatigue life of joint hole in aircraft can be distinguishedly prolonged. To study residual stress around cold expan...Because of the generated residual stress after applying cold expanded technique with split sleeve, fatigue life of joint hole in aircraft can be distinguishedly prolonged. To study residual stress around cold expanded hole, some hypothesises such as small deformation in radial symmetry, plane stress, plane strain, uniform distribution pressure have been presented in most papers. However, accurate result cannot be gained based on these hypothesises. In order to overcome the shortage, a 3 dimensional model is proposed which takes into consideration of the effect on split sleeve and the different distribution pressure along thick direction of specimen. The stress distributions of cold expanded hole with split sleeve under loading or unloading, as well as under fatigue tension have been stu died. To reveal the advantage of cold expanding process with split sleeve, the expansion without split sleeve has also been studied and compared with the former.展开更多
The effects of heat treatment process on microstrucature, micro-yield strength and dynamic dimensional stability of ZL114A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microsco...The effects of heat treatment process on microstrucature, micro-yield strength and dynamic dimensional stability of ZL114A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile testing and thermal cycling on-line measuring method. Fine dispersed eutectic Si phases are observed, and long strip eutectic Si and massive primary Si phases decrease in ZL114A alloy after high-temperature and long-time solution treatment, which result in the increase of micro-plastic deformation resistance. With the increasing of aging temperature, aging precipitation behaviour of ZLll4A alloy transforms from precipitation of GP zone and fl＇ phases simultaneously at lower temperature to precipitation of stable Mg2Si phases at higher temperature. Because coherent strengthening is the main strengthen mechanism for micro-plastic deformation, precipitation of stable Mg2Si phases is unfavorable to the improvement of micro-plastic deformation resistance. Micro-yield strength cannot characterize dimensional stability comprehensively, and dynamic dimensional stability under alternative temperature should also be tested cooperatively for better evaluation of dimensional stability.展开更多
文摘Because of the generated residual stress after applying cold expanded technique with split sleeve, fatigue life of joint hole in aircraft can be distinguishedly prolonged. To study residual stress around cold expanded hole, some hypothesises such as small deformation in radial symmetry, plane stress, plane strain, uniform distribution pressure have been presented in most papers. However, accurate result cannot be gained based on these hypothesises. In order to overcome the shortage, a 3 dimensional model is proposed which takes into consideration of the effect on split sleeve and the different distribution pressure along thick direction of specimen. The stress distributions of cold expanded hole with split sleeve under loading or unloading, as well as under fatigue tension have been stu died. To reveal the advantage of cold expanding process with split sleeve, the expansion without split sleeve has also been studied and compared with the former.
文摘The effects of heat treatment process on microstrucature, micro-yield strength and dynamic dimensional stability of ZL114A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile testing and thermal cycling on-line measuring method. Fine dispersed eutectic Si phases are observed, and long strip eutectic Si and massive primary Si phases decrease in ZL114A alloy after high-temperature and long-time solution treatment, which result in the increase of micro-plastic deformation resistance. With the increasing of aging temperature, aging precipitation behaviour of ZLll4A alloy transforms from precipitation of GP zone and fl＇ phases simultaneously at lower temperature to precipitation of stable Mg2Si phases at higher temperature. Because coherent strengthening is the main strengthen mechanism for micro-plastic deformation, precipitation of stable Mg2Si phases is unfavorable to the improvement of micro-plastic deformation resistance. Micro-yield strength cannot characterize dimensional stability comprehensively, and dynamic dimensional stability under alternative temperature should also be tested cooperatively for better evaluation of dimensional stability.
