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GROWTH OF SHORT CRACKS OF A537CLI STEEL UNDER FATIGUE LOADING IN 3.5% NaCl SOLUTION

PEI Hongxun YANG Jingjun KE Wei Institute of Corrosion and Protection of Metals , Academia Sinica , Shenyang , China PEI Hongxun Institute of Corrosion and Protection of Metals , Academia Sinica , Shenyang , China

金属学报(英文版)

The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of single-edge crack about 0.05—0.15 mm for A537CLI steel.The growth rate of short cracks is faster than those of long ones around the threshoht stress intensity.The threshold stress intensity for short crack growth decreases with de- creasing crack length.The acceleration effect of the salt water,as compared with atmosphere environment,on the growth of short cracks under fatigue is much greater than that on the growth of long cracks.

关键词: short fatigue crack , null , null , null

8090Al-Li合金疲劳短裂纹门槛值的研究

陈铮

金属学报

本文研究了8090Al-Li合金穿透疲劳短裂纹的门槛值,测定了不同长度短裂纹的门槛值和裂纹闭合效应,探讨了该合金疲劳短裂纹门槛值、裂纹尾迹和裂尖屏蔽之间的关系,给出了该合金穿透疲劳短裂纹的上界值和理论最低门槛值。

关键词: 铝锂合金 , short fatigue crack , threshold , crack closure effect

残余压应力场中疲劳短裂纹扩展模型及实验

崔振旗 , 徐可为 , 胡奈赛

金属学报

结合实验讨论了残余应力对裂纹扩展作用的模型及其存在的问题．指出用公式ΔＫ＿（ｅｆｆ）＝（Ｋ＿（ｍａｘ）＋λＫ＿ｒ）－Ｋ＿（ｏｐ）可较准确地计算出残余压应力场中裂纹的扩展速率．残余压应力既使裂纹闭合力提高，又使最大应力强度因子降低，两者均使裂纹扩展驱动力ΔＫ＿（ｅｆｆ）减少，因而降低了裂纹的扩展速率．

关键词: 残余应力 , short fatigue crack , crack growth rate

一种等应力试样中的疲劳短裂纹行为

洪友士 , 吕永华 , 郑哲敏

金属学报

设计了一种三角形试样,当施加弯曲载荷时,该试样等腰三角形段内的表面拉应力为常数。采用振动试验机对所设计的试样进行疲劳试验,以研究一种焊接金属表面疲劳短裂纹萌生和发展特征。结果表明,疲劳短裂纹起源于铁素体晶内的滑移带。随疲劳周次增加,短裂纹发展以裂纹密度不断增加为主要特征。短裂纹的汇合造成裂纹发展且裂纹路径以穿晶为主。

关键词: 等应力试样 , short fatigue crack , weld metal

高温低周疲劳短裂纹萌生的数值模拟

王正 , 谭伟同 , 王璐 , 陈楠

机械工程材料

基于大量的高温低周疲劳试验,编写Matlab程序修正voronoi多边形模拟了20钢表面的显微组织;用有限元软件计算得到了不同试验条件下试样表面的应力、应变状态;以基础能量表征晶界及滑移带抵抗裂纹萌生的能力,改进位错累积理论并计算获得了裂纹的萌生寿命,实现了对低碳钢高温低周疲劳短裂纹萌生的数值模拟.结果表明:在高温下,疲劳短裂纹主要萌生于应力集中处的驻留滑移带及不稳定晶界上,受表面显微组织的影响,既有沿晶萌生又有穿晶萌生;修正的voronoi多边形很好地反映了表面显微组织,数值模拟能够准确再现不同循环次数下疲劳短裂纹的群体萌生行为.

关键词: 高温 , 低周疲劳 , 短裂纹 , 萌生寿命 , 数值模拟

THRESHOLD OF SHORT FATIGUE CRACK FOR Al-Li ALLOY 8090

CHEN Zheng Northwestern Polytechnical University , Xi′an , China Lab.No.401 , Northwestern Polytechnical University , Xi′an 710072

金属学报(英文版)

Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks was discussed.The super demarcation length and lowest theoretical threshold of short through fa- tigue cracks were presented.

关键词: Al-Li alloy , null , null , null , null

SHORT FATIGUE CRACK BEHAVIOUR IN ISO-STRESS SPECIMENS

HOGN Youshi LU Yonghua ZHENG Zhemin Institute of Mechanics , Academia Sinica , Beijing , China Institute of Mechanics , Academia Sinica , Beijing 100080 , China

金属学报(英文版)

Fatigue tests were made on a vibration machine using specially designed specimens to investi- gate the initiation and propagation features of short fatigue cracks in a weld metal.The spec- imens were triangular in shape so that when loaded as a cantilever beam the surface tensile stress is constant.Test results show that short fatigue cracks mainly originate from slip bands within ferrite grains.The development of short fatigue cracks is marked by a gradual increase in crack density with fatigue cycles.Coalescence of short cracks leads to crack propagation and the crack path is predominantly transgranular.

关键词: iso—stress specimen , null , null

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