Rickhey Felix, Hong Seokmoo
Department of Automotive and Mechanical Engineering, Kongju National University, Cheonan 31080, Korea.
Materials (Basel). 2022 May 24;15(11):3738. doi: 10.3390/ma15113738.
Governing void growth, stress triaxiality () is a crucial parameter in ductile damage prediction. is defined as the ratio of mean stress to equivalent stress and represents loading conditions. Attempts at introducing material anisotropy in ductile damage models have started only recently, rendering necessary in-depth investigation into the role of here. is commonly derived via finite elemnt (FE) simulation. An alternative is presented here: based on analytical expressions, is obtained directly from the strains in the critical zone. For anisotropic materials, associated with a specimen varies with yield criterion and material (anisotropy). To investigate the meaning of triaxiality for anisotropic materials, metal sheets made of dual phase steel DP780, and zirconium alloy Zirlo are chosen. Analytical expressions for are derived for three popular yield criteria: von Mises, Hill48 and Barlat89. Tensile tests are performed with uniaxial tension, notch, and shear specimens, and the local principal strains, measured via digital image correlation (DIC), are converted to h. The uniaxial tension case reveals that only the anisotropic yield criteria can predict the expected = 1/3. The ramifications associated with anisotropy become apparent for notched specimens, where differences are highest; for shear specimens, the yield criterion and material-dependence is relatively moderate. This necessitates and, consequently, the triaxiality failure diagram (TFD) being accompanied by the underlying yield criterion and anisotropy parameters. As the TFD becomes difficult to interpret, it seems more advantageous to provide pairs of principal strain ratio and failure strain. Suggestions for deriving representative and are made.
控制空洞生长的应力三轴性（）是韧性损伤预测中的一个关键参数。被定义为平均应力与等效应力之比，代表加载条件。在韧性损伤模型中引入材料各向异性的尝试直到最近才开始，因此有必要深入研究在此处的作用。通常通过有限元（FE）模拟得出。这里提出了一种替代方法：基于解析表达式，直接从临界区的应变中获得。对于各向异性材料，与试样相关的随屈服准则和材料（各向异性）而变化。为了研究各向异性材料的三轴性的意义，选择了双相钢DP780和锆合金Zirlo制成的金属板。针对三种常见的屈服准则：冯·米塞斯、希尔48和巴拉特89，推导了的解析表达式。使用单轴拉伸、缺口和剪切试样进行拉伸试验，并通过数字图像相关（DIC）测量的局部主应变转换为h。单轴拉伸情况表明，只有各向异性屈服准则能够预测预期的 = 1/3。对于缺口试样，与各向异性相关的影响变得明显，其中差异最大；对于剪切试样，屈服准则和材料依赖性相对适中。这就需要，因此，三轴性失效图（TFD）要伴随着潜在的屈服准则和各向异性参数。由于TFD难以解释，提供主应变比和失效应变对似乎更有利。还提出了推导代表性和的建议。
