共查询到20条相似文献,搜索用时 31 毫秒
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采用计算机模拟了位错和位错偶沿单一滑移系从裂纹尖端的发射,考察了滑移面取向、外加载荷、晶格摩擦力以及位错发射的临界应力强度因子对所发射的位错数量、塑性区与无位错区大小以及裂关残余应力强度因子的影响研究表明,位错从裂纹尖端发射的临界应力强度因子对无位错区的存在和其大小起决定作用,而外加载荷与晶格摩擦力主要影响位错发射的数量以及塑性区大小.在I型载荷作用下,滑移面与裂纹面的夹角越大,从裂尖发射出的位错数量越多,位错对裂纹的屏蔽效应也越大当裂纹发射位错后的残余应力强度因子仍然较大时,位错偶就有可能在裂纹尖端附近产生井沿着几个滑移面发射,但发射出的位错偶对裂纹没有明显的屏蔽作用在滑移面不垂直于裂纹面时,发射出的位错或位错偶关于裂纹面呈不对称分布 相似文献
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ZHUANG Tao WANG Zhongfang Central Iron Steel Research Institute Ministry of Metallurgical Industry Beijing Dept.No. Central Iron steel Research Institute Ministry of Metallurgical Industry Beijing China 《金属学报(英文版)》1989,2(5):354-358
The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzedusing finite element calculations.The crack initiation and steady propagation behaviours havealso been investigated by means of slip line pattern etching technique and mechanical tests.The results show that there are HRR near field and distant field in the crack tip region,andthe later depends on the specimen configuration.The crack initiation behaviour is controlledby a single parameter J.In contrast,the steady crack propagation is affected by the distantstrain field and can not be described by single parameter only. 相似文献
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根据有限元计算分析的弹塑性裂纹体在平面应力条件下的裂纹尖端应力应变场,采用滑移线浸蚀以及断裂力学的试验方法,研究了该条件下的起裂和稳态扩展现象。结果表明,在裂纹尖端存在着HRR近程场以及取决于试样几何类型的远程场。起裂由单参数J控制,而稳态扩展行为则受远程应变场影响,不能由单参数描述。 相似文献
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DENG Rongying YE Zhijun Institute of Mechanics Academia Sinica Beijing China LIU Shuhua ZOU Dingqiang China Academy of Railway Sciences Beijing China Institute of Mechanics Academia Sinica Beijing China 《金属学报(英文版)》1990,3(6):424-428
The effect of ferrite content in ferrite-martensite dual-phase steel on the initiation and prop-agation of fatigue crack and the plastic deformation at crack tip has been studied.In the rangeof ferrite content from 24.2 to 41.5%,the optimum seems to be 33.8%,of which the crack ini-tiation will be prolonged,the threshold value increased,the propagation rate decreased and theclosure stress intensity factor increased.As the propagation force is described by effectivestress intensity factor,three steels with various ferrite contents will show the same propagationbehaviour on da/dN vs △ K_(eff)curve.It is shown that the closure effect increases with thedecrease in △K at the fatigue crack tip.When △K equals to △K_(th),the closure effect reachesa maximum value of0.7 in a dual-phase steel with 33.8%ferrite. 相似文献
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借助于扫描电镜,全面分析了截齿硬质合金刀头在使用过程中的开裂及裂纹的疲劳扩展行为。结果表明,硬质合金刀头在使用过程中的开裂是由针焊开裂、热疲劳和冲击疲劳所造成的微裂纹引起的。裂纹扩展的疲劳行为主要源于硬质含金的高Co含量和大的WC颗粒造成的对裂纹扩展的阻碍、裂纹扩展路线的拐折造成的裂纹尖端应力强度因子的降低及刀头承受的交变冲击载荷的共同作用。 相似文献