A comparison of stress triaxiality and strain distributions in notched bar geometries as determined by Bridgman expressions and finite element analysis
A comparison of stress triaxiality and strain distributions in notched bar geometries as determined by Bridgman expressions and finite element analysis
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通过布里奇曼表达式和有限元分析确定的缺口钢筋几何形状中的应力三轴性和应变分布的比较
DOI：
10.1016/j.prostr.2020.11.032
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Jones M
中科院分区：
文献类型：
--
作者：
Jones M
当表征材料的破坏行为时，通常需要构造一个韧性破坏轨迹，它将破坏时的应变与所显示的应力三轴度水平联系起来。轨迹所需的数据可以通过缺口棒的多轴拉伸测试来确定，使用一系列缺口半径来产生不同水平的三轴度。三轴度和应变值可以使用Bridgman导出的表达式来计算，其仅需要横截面半径和边缘轮廓曲率半径的知识。然而，这种表述的有效性可能不会延伸到尖锐的缺口。进行了缺口棒的实验测试，并通过图像捕获测量了测试期间的试样轮廓。处理这些数据，并使用Bridgman表达式计算三轴度和应变值。进行有限元分析，以模拟试样的几何形状，并将三轴度和应变的结果与Bridgman的估计值进行比较。非常差的协议被发现之间的两种方法确定的三轴度值，和布里奇曼的假设，应变是均匀的整个半径的试样被发现在这些条件下无效。据认为，这可能是由于布里奇曼的分析是针对最初光滑并在高应变下形成颈部的样本，而不是最初有缺口的样本。这些研究结果表明，这是不准确的，使用Bridgman表达式来制定一个失败的轨迹拉伸缺口酒吧测试，而不是建议，有限元分析用于这些目的。
When characterising the failure behaviour of materials, it is often necessary to construct a ductile failure locus which relates the strain at failure to the level of stress triaxiality exhibited. The data required for a locus can be determined through multiaxial tensile testing of notched bars, using a range of notch radii to produce different levels of triaxiality. The triaxiality and strain values may be calculated using expressions derived by Bridgman, which only require knowledge of the cross-sectional radius and edge profile radius of curvature. However, the validity of such expressions may not extend to sharp notches. Experimental testing of notch bars was performed, and specimen profiles measured through image capture for the duration of the tests. These data were processed and triaxiality and strain values were calculated using the Bridgman expressions. Finite element analyses were performed to simulate the test specimen geometries, and results for the triaxiality and strain were compared to Bridgman’s estimates. Very poor agreement was found between the two methods of determining the triaxiality values, and Bridgman’s assumption that the strain is uniform across the radius of the specimen was found invalid under these conditions. It is thought this is likely due to the fact Bridgman’s analysis was for specimens that were initially smooth and formed a neck at high strains, as opposed to specimens that are initially notched. These findings suggest that it is not accurate to use the Bridgman expressions to formulate a failure locus for tensile notch bar tests, and it is instead recommended that the finite element analysis is employed for these purposes.