The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than lo...The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than long ones and are observed to grow at the stress intensity ranges far below the long crack threshold. The distinction of growth bahavior between short and long cracks is attributed to the difference of their crack closure effect. The growth behavior of short cracks can be rationalized with that of long ones in terms of effective stress intensity ranges. The upper demarcation value of short through cracks for aluminum-lithium alloy 8090 is presented.展开更多
In order to clarify the physical background of the scatter in fatigue behaviour, rotary bending fatigue tests are carried out using smooth speciments of a medium carbon steel with two kinds of grain sizes. The statis...In order to clarify the physical background of the scatter in fatigue behaviour, rotary bending fatigue tests are carried out using smooth speciments of a medium carbon steel with two kinds of grain sizes. The statistical characteristics of short carck initiation and growth lives are investigated by a new definition of short fatigue crack initiation. Detailed analysis reveals that the distribution of short crack initiation life can be expressed by two or threeparameter Weibull distribution, and the threeparameter Weibull distribution is well fitted to the distribution of short crack growth life, and the grain size and stress level have a great influence on the statistical characteristics of crack initiation and growth life.展开更多
Rotary bending fatigue tests were carried out by using smoothspecimens of medium car- bon steel with two ferrite grain sizes. Inorder to clarify the physical background of the scatter in fa- tiguebehavior, the statist...Rotary bending fatigue tests were carried out by using smoothspecimens of medium car- bon steel with two ferrite grain sizes. Inorder to clarify the physical background of the scatter in fa- tiguebehavior, the statistical characteristics of the initiation andgrowth of short fatigue crack were in- vestigated. Results show thatthe short crack initiation and growth life distribution can beexpressed by two-or three-parameter Weibull distribution. The Weibulldistribution of the mixed type is well fitted to the crack lengthdistribution for both steels. The knee values of Weibull plots arerelated to the grain size.展开更多
对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后...对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后微区的疲劳破坏机理。结果表明,热影响区内疲劳物理短裂纹的扩展是不连续的,K仍可作为裂纹扩展的驱动参量,材料强度水平控制疲劳短裂纹扩展方向。在完全淬火-回火区,短裂纹扩展受到大尺寸晶粒和板条马氏体的影响,裂纹易偏折,疲劳抗力最好;而回火区的晶粒尺寸和强度较小,疲劳门槛值较低,裂纹抗力较弱。在不完全淬火-回火区,晶界析出碳化物较多,疲劳裂纹主要以沿晶方式扩展,裂纹扩展抗力最差。展开更多
文摘The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than long ones and are observed to grow at the stress intensity ranges far below the long crack threshold. The distinction of growth bahavior between short and long cracks is attributed to the difference of their crack closure effect. The growth behavior of short cracks can be rationalized with that of long ones in terms of effective stress intensity ranges. The upper demarcation value of short through cracks for aluminum-lithium alloy 8090 is presented.
文摘In order to clarify the physical background of the scatter in fatigue behaviour, rotary bending fatigue tests are carried out using smooth speciments of a medium carbon steel with two kinds of grain sizes. The statistical characteristics of short carck initiation and growth lives are investigated by a new definition of short fatigue crack initiation. Detailed analysis reveals that the distribution of short crack initiation life can be expressed by two or threeparameter Weibull distribution, and the threeparameter Weibull distribution is well fitted to the distribution of short crack growth life, and the grain size and stress level have a great influence on the statistical characteristics of crack initiation and growth life.
文摘Rotary bending fatigue tests were carried out by using smoothspecimens of medium car- bon steel with two ferrite grain sizes. Inorder to clarify the physical background of the scatter in fa- tiguebehavior, the statistical characteristics of the initiation andgrowth of short fatigue crack were in- vestigated. Results show thatthe short crack initiation and growth life distribution can beexpressed by two-or three-parameter Weibull distribution. The Weibulldistribution of the mixed type is well fitted to the crack lengthdistribution for both steels. The knee values of Weibull plots arerelated to the grain size.
文摘对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后微区的疲劳破坏机理。结果表明,热影响区内疲劳物理短裂纹的扩展是不连续的,K仍可作为裂纹扩展的驱动参量,材料强度水平控制疲劳短裂纹扩展方向。在完全淬火-回火区,短裂纹扩展受到大尺寸晶粒和板条马氏体的影响,裂纹易偏折,疲劳抗力最好;而回火区的晶粒尺寸和强度较小,疲劳门槛值较低,裂纹抗力较弱。在不完全淬火-回火区,晶界析出碳化物较多,疲劳裂纹主要以沿晶方式扩展,裂纹扩展抗力最差。
