Structural strength scaling law for fracture of plastic-hardening metals and testing of fracture properties
Structural strength scaling law for fracture of plastic-hardening metals and testing of fracture properties
复制标题
DOI：
10.1016/j.eml.2020.101141
复制
发表时间：
2021-02-01
影响因子：
4.7
通讯作者：
Bazant, Zdenek P.
中科院分区：
文献类型：
--
作者：
Nguyen, Hoang T.;Donmez, A. Abdullah;Bazant, Zdenek P.
塑性硬化金属的小尺度屈服断裂是一个众所周知的理论，主要是由Hutchinson、Rice和Rosengren提出的（因此被称为HRR理论）。然而，尽管已经测试了不同尺寸的试样来验证小尺度屈服理论，但尺寸效应从弹塑性行为到小尺度和大尺度屈服到断裂过程区转变的解析标度规律显然尚未形成。这种标度规律将有助于金属i型韧性断裂性能的设计和测量，也是本研究的目的。与混凝土或复合材料等准脆性材料的断裂不同，塑性硬化材料的建模非常复杂，因为在微米尺度断裂过程区（FPZ）和外部弹性（卸载）材料之间形成了毫米尺度的奇异屈服区。大规模过渡尺寸效应的关键是有效屈服区尺寸，它是根据塑性硬化区虚拟功和过渡区内弹性奇异应力场的等效计算得出的，并与裂纹平行t应力有关。尺寸效应分析不仅需要考虑通过屈服区的j积分能量通量所传递的FPZ内的耗散，还需要考虑结构和塑性材料的卸载带在前进屈服区后面释放的能量。将能量释放率和能量耗散率等同，可以得到近似的能量尺寸效应（标度）定律，该定律与计算得到的裂纹韧带包含屈服区时的小尺寸和大尺寸渐近行为相匹配。该规律与准脆性断裂相似，但其系数对断裂能和屈服区大小的依赖程度不同。该定律可简化为线性回归，可用于断裂能（或临界j积分）和屈服区有效尺寸r(p)的尺寸效应测试。高裂纹平行应力T对r(p)的影响是可能的，但这将留给未来的研究，因为它不会影响所推导的标度律。针对小尺寸范围（大规模屈服）向大尺寸范围（小规模屈服）过渡的试验，提出了一种修正的尺寸效应方法，并进行了非线性优化。通过对铝缺口试样的比例尺试验，验证了尺寸效应规律。(C) 2020 Elsevier Ltd.版权所有。
The small-scale yielding fracture of plastic-hardening metals is a well-understood theory, essentially conceived by Hutchinson, Rice and Rosengren (hence the name HRR theory). However, even though specimens of rather different sizes have been tested to verify the small-scale yielding theory, an analytical scaling law for the size effect transition from elastic-plastic behavior through small- and large-scale yielding to fracture process zone has apparently not been formulated. Such a scaling law would be useful for the design as well as measurement of mode-I ductile fracture properties of metals, and is the aim of this study. Unlike the fracture of quasibrittle materials such as concrete or composites, the modeling of plastic-hardening materials is complicated by a millimeter scale singular yielding zone that forms between the micrometer-scale fracture process zone (FPZ) and the elastic (unloading) material on the outside. Essential for the large-scale transitional size effect is the effective yielding zone size, which is here calculated from the equivalence of the virtual works within the plastic-hardening zone and elastic singular stress fields within the transition zone, and is shown to depend on the crack parallel T-stress. The size effect analysis requires taking into account not only the dissipation in the FPZ delivered by the J-integral flux of energy through the yielding zone, but also the energies released from the structure and from the unloaded band of plasticized material trailing the advancing yielding zone. Equating the rates of energy releases and energy dissipation leads to an approximate energetic size effect (scaling) law that matches the calculated small-and large-size asymptotic behaviors, when the crack ligament contains the yielding zone.. The law is similar to that for quasibrittle fracture but its coefficients depend on the fracture energy and the yielding zone size in a different way. This law, reducible to linear regression, can be exploited for size effect testing of fracture energy (or critical J-integral) and effective size r(p) of the yielding zone. An effect of high crack-parallel stress T on r(p) is likely but is relegated to future study, as it would not affect the scaling law derived. For testing of the transition from the small-size range (large-scale yielding) to the large-size range (small-scale yielding), a modified size effect method, requiring nonlinear optimization, is developed. The size effect law is verified by scaled tests of notched specimens of aluminum. (C) 2020 Elsevier Ltd. All rights reserved.