Habit plane rotation of lath martensite transformation in Fe-Ni-Mn alloy was predicted by means of Displacement Vector Theory. Its surface relief effect was observed and a math model for the quantitative analysis of h...Habit plane rotation of lath martensite transformation in Fe-Ni-Mn alloy was predicted by means of Displacement Vector Theory. Its surface relief effect was observed and a math model for the quantitative analysis of habit plane rotation of lath martensite transformation was established by means of atomic force microscopy (AFM). The experiment showed that the largest rotation of habit plane of lath martensite transformation predicted by means of Displacement Vector Theory is 13.50°, and it's incompatible with the concept of invariant plane strain (IPS); surface relief of lath martensite revealed no character of IPS, i.e. it exhibited irregular 'N'-shaped 'surface relief packet', and 'surface relief packet' was composed of layers of several small surface reliefs, the AFM quantitative analysis of habit plane rotation of lath martensite transformation was 11.11°, which was in agreement with the prediction of Displacement Vector Theory (13.50°) and it firmly confirmed the habit plane rotation of lath martensite transformation and the correctness of Displacement Vector Theory.展开更多
Imposing compressive residual stress field around a fastening hole serves as a universal method to enhance the hole fatigue strength in the aircraft assembly filed.Ultrasonic Peening Drilling(UPD)is a recently propose...Imposing compressive residual stress field around a fastening hole serves as a universal method to enhance the hole fatigue strength in the aircraft assembly filed.Ultrasonic Peening Drilling(UPD)is a recently proposed hybrid hole making process,which can achieve an integration of strengthening and precision-machining with a one-shot-drilling operation.Due to the ironing effect of tool flank surface,UPD introduces large compressive residual stress filed in hole subsurface.In order to reveal the strengthening mechanism of UPD,the influence of ultrasonic vibration and tool dynamic relief angle on ironing coverage rate and its corresponding effect on surface integrity in UPD were analyzed.The experiments were conducted to verify the influence of ironing effect on surface integrity and fatigue behavior of Ti-6Al-4V hole in UPD.The results indicate that the specimen features smaller surface roughness,higher micro-hardness,plastic deformation degree and circumferential compress residual stress under higher ironing coverage rate.The fatigue life increases with the raise of ironing coverage rate,and the fatigue source site in UPD shifts from surface to subsurface comparing with that without vibration assistance.The results demonstrates that a better strengthening effect can be obtained by reasonably controlling the ironing coverage rate in UPD.展开更多
基金the National Natural Science Foundation of China and that of Hebei province.
文摘Habit plane rotation of lath martensite transformation in Fe-Ni-Mn alloy was predicted by means of Displacement Vector Theory. Its surface relief effect was observed and a math model for the quantitative analysis of habit plane rotation of lath martensite transformation was established by means of atomic force microscopy (AFM). The experiment showed that the largest rotation of habit plane of lath martensite transformation predicted by means of Displacement Vector Theory is 13.50°, and it's incompatible with the concept of invariant plane strain (IPS); surface relief of lath martensite revealed no character of IPS, i.e. it exhibited irregular 'N'-shaped 'surface relief packet', and 'surface relief packet' was composed of layers of several small surface reliefs, the AFM quantitative analysis of habit plane rotation of lath martensite transformation was 11.11°, which was in agreement with the prediction of Displacement Vector Theory (13.50°) and it firmly confirmed the habit plane rotation of lath martensite transformation and the correctness of Displacement Vector Theory.
基金supported by the National Natural Science Foundation of China(Nos.51905024,51975035 and 91960203).
文摘Imposing compressive residual stress field around a fastening hole serves as a universal method to enhance the hole fatigue strength in the aircraft assembly filed.Ultrasonic Peening Drilling(UPD)is a recently proposed hybrid hole making process,which can achieve an integration of strengthening and precision-machining with a one-shot-drilling operation.Due to the ironing effect of tool flank surface,UPD introduces large compressive residual stress filed in hole subsurface.In order to reveal the strengthening mechanism of UPD,the influence of ultrasonic vibration and tool dynamic relief angle on ironing coverage rate and its corresponding effect on surface integrity in UPD were analyzed.The experiments were conducted to verify the influence of ironing effect on surface integrity and fatigue behavior of Ti-6Al-4V hole in UPD.The results indicate that the specimen features smaller surface roughness,higher micro-hardness,plastic deformation degree and circumferential compress residual stress under higher ironing coverage rate.The fatigue life increases with the raise of ironing coverage rate,and the fatigue source site in UPD shifts from surface to subsurface comparing with that without vibration assistance.The results demonstrates that a better strengthening effect can be obtained by reasonably controlling the ironing coverage rate in UPD.
