Ultrasonic impact treatment(UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achiev...Ultrasonic impact treatment(UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe,which is considered as the main reason for the improvement of fatigue strength. In this paper,the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy(TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer,resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490 BW welded joints is related to the high density of dislocation tangles and dislocation walls.展开更多
The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top laye...The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.展开更多
目的研究时效-超声冲击(A-UIT)复合处理方法对铝合金激光焊缝耐磨性的影响。方法对7075铝合金激光焊缝进行时效处理、超声冲击处理、A-UIT复合处理,对比时效处理、超声冲击处理、A-UIT复合处理后焊缝的表面硬度、表面粗糙度、3D形貌及...目的研究时效-超声冲击(A-UIT)复合处理方法对铝合金激光焊缝耐磨性的影响。方法对7075铝合金激光焊缝进行时效处理、超声冲击处理、A-UIT复合处理,对比时效处理、超声冲击处理、A-UIT复合处理后焊缝的表面硬度、表面粗糙度、3D形貌及扫描显微组织,并分析A-UIT复合处理、时效处理和超声冲击处理对焊缝耐磨性能的影响及机理。结果超声冲击处理的焊缝与焊态进行比较,粗糙度减小了8.65μm,表面硬度增大了47HV,摩擦系数降低了0.17,磨损率降低了70%;6、24、32 h时效处理后的粗糙度分别比焊态减小了10.18、4.19、5.88μm,表面硬度比焊态高出37、55、44HV,平均摩擦系数比焊态降低0.10、0.08、0.09,磨损率比焊态低51%、54%、61%;6、24、32 h A-UIT复合处理分别与6、24、32 h时效处理相比,粗糙度减小了9.88、10.58、8.7μm,表面硬度增大了43、44、31HV,平均摩擦系数降低了0.1、0.1、0.07,磨损率降低了35%、41%、27%。A-UIT复合处理焊缝主要以磨粒磨损为主,且存在局部剥层磨损。单独时效处理焊缝主要以浅色的剥层磨损为主,且存在少量的磨粒磨损,磨损面积较大,并伴有少量的氧化磨损。结论时效和超声冲击处理均可有效提高焊缝的耐磨性能,超声冲击处理的作用要大于时效处理,摩擦系数比24 h时效处理小15.3%,磨损率为时效处理的36.1%。A-UIT复合处理后的焊缝在纳米晶和时效强化相的共同作用下,比时效处理和超声冲击处理的焊缝耐磨性能提升更为明显。24 h A-UIT复合处理后,焊缝的摩擦系数比24 h时效处理提高了28.5%,比超声冲击状态提高了8.6%,磨损率比24 h时效处理提高了40.9%,比超声冲击状态提高了76.9%。展开更多
Treating weld toes properly can improve the fatigue performance. Ultrasonic impact treatment （UIT） is a more effective and convenient method to enhance the fatigue strength of welded joints and suchlike structures. ...Treating weld toes properly can improve the fatigue performance. Ultrasonic impact treatment （UIT） is a more effective and convenient method to enhance the fatigue strength of welded joints and suchlike structures. Fatigue tests were conducted on the specimens made of X65 pipeline steel. The test specimens were investigated on the fatigue strength and the fatigue life at the same stress range level by comparing the ones peened by UIT with the others without the treatment： the fatigue strength of the specimens as UIT, 90% of the fatigue strength of the base mental, is increased by 38% compared with that of as welded only; the fatigue life of the ones as UIT is prolonged by 11 multiples of the ones as welded only.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51365014)the Industrial Support Key Project of Jiangxi Province,China(No.20161BBE50072)
文摘Ultrasonic impact treatment(UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe,which is considered as the main reason for the improvement of fatigue strength. In this paper,the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy(TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer,resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490 BW welded joints is related to the high density of dislocation tangles and dislocation walls.
基金Funded by the National National Natural Science Foundation of China(No.51505189)Open Project of Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment&Technology(No.FM-2015-5)
文摘The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.
文摘目的研究时效-超声冲击(A-UIT)复合处理方法对铝合金激光焊缝耐磨性的影响。方法对7075铝合金激光焊缝进行时效处理、超声冲击处理、A-UIT复合处理,对比时效处理、超声冲击处理、A-UIT复合处理后焊缝的表面硬度、表面粗糙度、3D形貌及扫描显微组织,并分析A-UIT复合处理、时效处理和超声冲击处理对焊缝耐磨性能的影响及机理。结果超声冲击处理的焊缝与焊态进行比较,粗糙度减小了8.65μm,表面硬度增大了47HV,摩擦系数降低了0.17,磨损率降低了70%;6、24、32 h时效处理后的粗糙度分别比焊态减小了10.18、4.19、5.88μm,表面硬度比焊态高出37、55、44HV,平均摩擦系数比焊态降低0.10、0.08、0.09,磨损率比焊态低51%、54%、61%;6、24、32 h A-UIT复合处理分别与6、24、32 h时效处理相比,粗糙度减小了9.88、10.58、8.7μm,表面硬度增大了43、44、31HV,平均摩擦系数降低了0.1、0.1、0.07,磨损率降低了35%、41%、27%。A-UIT复合处理焊缝主要以磨粒磨损为主,且存在局部剥层磨损。单独时效处理焊缝主要以浅色的剥层磨损为主,且存在少量的磨粒磨损,磨损面积较大,并伴有少量的氧化磨损。结论时效和超声冲击处理均可有效提高焊缝的耐磨性能,超声冲击处理的作用要大于时效处理,摩擦系数比24 h时效处理小15.3%,磨损率为时效处理的36.1%。A-UIT复合处理后的焊缝在纳米晶和时效强化相的共同作用下,比时效处理和超声冲击处理的焊缝耐磨性能提升更为明显。24 h A-UIT复合处理后,焊缝的摩擦系数比24 h时效处理提高了28.5%,比超声冲击状态提高了8.6%,磨损率比24 h时效处理提高了40.9%,比超声冲击状态提高了76.9%。
文摘Treating weld toes properly can improve the fatigue performance. Ultrasonic impact treatment （UIT） is a more effective and convenient method to enhance the fatigue strength of welded joints and suchlike structures. Fatigue tests were conducted on the specimens made of X65 pipeline steel. The test specimens were investigated on the fatigue strength and the fatigue life at the same stress range level by comparing the ones peened by UIT with the others without the treatment： the fatigue strength of the specimens as UIT, 90% of the fatigue strength of the base mental, is increased by 38% compared with that of as welded only; the fatigue life of the ones as UIT is prolonged by 11 multiples of the ones as welded only.
基金supported by the National Natural Science Foundation of China(No.52165050)the Natural Science Foundation of Jiangxi Province,China(No.20181BAB206027).
