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复合型韧性断裂实验和控制参数 总被引:8,自引:0,他引:8
通过对不同韧性材料在各种平面复合载荷形式下裂纹启裂阶段裂端变形、启裂位置和扩展方向的系统的宏微观实验验证及计算分析,考察了韧性断裂参数空穴扩张比的分布特征和裂纹启裂及扩展方向的关系.得到:对于不同韧性的材料,在裂端的钝化变形区域,空穴扩张比的极大值区对应干裂纹的启裂位置,裂纹启裂时钝化裂端前缘空穴扩张比的临界值不敏感于复合比的变化.而对于裂纹启裂后的扩展方向,则需根据具体材料在相应的特定区域中比较空穴扩张比参数极大值的分布特征,需经进一步的分析,从而确定裂纹的扩展方向.实验及计算结果表明,尽管复合型断裂时裂纹启裂及扩展的机理极其复杂,用于韧性材料复合型断裂的空穴扩张比参数仍能很好地预测裂端的启裂及扩展方向,可作为复合型韧性断裂过程的控制参数. 相似文献
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Based on [1], the stress structures of the smooth region and shear lip of the specimens have been investigated in the paper.
The characteristics of the stress structure in the smooth region have been found that the variable z can separated out; the
stresses in the midsection can be obtained by the plane strain FEM results or HRR structure modified by the stress triaxiality.
The effects of load level and thickness on the stress structure can be reflected by the distribution of CTOD along the thickness
direction. The obtained expressions of the stresses are very simple and visualized. The analyses of the stress structure in
the shear lip show that the stresses can be obtained by different methods of interpolation to a certain precise degree.
A new degree parameter of the plane strain state has been put forward and studied. The parameter can reflect relatively well
the variation of the kind and thickness of the specimen as well as the load level. The fracture parameter has also been investigated
to be sure that it can be obtained by modified CTOD with the stress triaxiality. 相似文献
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IntroductionNickel-basehightemperatureresistancesuperalloysarsewidelyusedingasturbinesandjetengines.DireetionallysolidificationwasintroducedtoenhancecreepsbengthbyelindnahnggrainboundariesnormaltotheappliedstresswherevoidsarelikelytOoccurundercreepload.Inpractice,however,theappliedstressmaynotbeuniaxialnordirectedparalleltOthegrainboundaries.Singlecrystalswerethusdeveloped.CongregationoflowtempefAnremeltingelementsongrainboundaries,grainboundaryoxidation)etc.,areadditionalfactorsthatwoulddeg… 相似文献
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Based on[1],the stress structures of the smooth region and shear lip of thespecimens have been investigated in the paper.The characteristics of the stress structure inthe smooth region have been found that the variable z can separated out;the stressesin the midsection can be obtained by the plane strain FEM results or HRR structuremodified by the stress triaxiality.The effects of load level and thickness on the stressstructure can be reflected by the distribution of CTOD along the thickness direction.The obtained expressions of the stresses are very simple and visualized.The analysesof the stress structure in the shear lip show that the stresses can be obtained bydifferent methods of interpolation to a certain precise degree.A new degree parameter of the plane strain state has been put forward andstudied.The parameter can reflect relatively well the variation of the kind andthickness of the specimen as well as the load level.The fracture parameter has alsobeen investigated to be sure that it can be obta 相似文献
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1 引言为在细观机理基础上建立韧性材料在一定应力状态下宏观裂纹产生和发展的力学模型。一些学者已做了不少工作.人们力图通过细观研究找到一个较接近韧性材料损伤和断裂物理本质的材料破坏准则,以用来描述和预测韧性材料的损伤和断裂.直到现在,大多数研究都认为无裂纹体与裂纹体的破坏是两个截然不同的问题.人们一直是用不同的准则来判定无裂纹试件和含裂纹试件的破坏的.但若从细观角度来看,对 相似文献
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本文主要针对Ⅰ+Ⅱ型裂纹问题,论述了这一领域近几十年研究工作的现状及最新进展.对该领域研究的趋向及存在的有关问题作了分析,讨论.指出:韧性材料在近Ⅰ型和近Ⅱ型时启裂及扩展的机理可能不同,目前所用的一些单参数判据要同时对两种不同机理作恰当描述有困难,可考虑采用双参数判据.同时,材料微结构及特征对断裂机理的影响也不可忽视 相似文献
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