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首页> 外文期刊>Journal of the Mechanics and Physics of Solids >DUCTILE CRACK GROWTH—Ⅰ. A NUMERICAL STUDY USING COMPUTATIONAL CELLS WITH MICROSTRUCTURALLY-BASED LENGTH SCALES
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DUCTILE CRACK GROWTH—Ⅰ. A NUMERICAL STUDY USING COMPUTATIONAL CELLS WITH MICROSTRUCTURALLY-BASED LENGTH SCALES

机译：韧性裂纹的发展——Ⅰ。基于微结构的长度尺度的计算单元的数值研究

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摘要

Many metals which fail by a void growth mechanism display a macroscopically planar fracture process zone of one or two void spacings in thickness characterized by intense plastic flow in the ligaments between the voids; outside this region, the voids exhibit little or no growth. To model this process a material layer containing a pre-existing population of similar sized voids is assumed. The thickness of the layer, D, can be identified with the mean spacing between the voids. This layer is represented by an aggregate of computational cells of linear dimension D. Each cell contains a single void of some initial volume. The Gurson constitutive relation for dilatant plasticity describes the hole growth in a cell resulting in material softening and, ultimately, loss of stress carrying capacity. The collection of cells softened by hole growth constitutes the fracture process zone of length l_1. Two fracture mechanism regimes can be identified corresponding to l_1 ≈ D and l_1 > > D. The connection between these mechanisms and fracture resistance is discussed. Finite element calculations have been carried out to determine crack growth resistance curves for plane strain, mode I crack growth under small scale yielding. A row of voided cells is placed on the symmetry plane ahead of the initial crack. These cell elements are embedded within a conventional elastic-plastic continuum. Under increasing load, the voids in the cells grow and coalesce to form a new crack surface thereby advancing the crack. Resistance curves are calculated for crack growth exceeding many multiples of D. The parameters affecting fracture resistance are discussed emphasizing the roles of microstructural parameters and continuum properties of the material. The effect of crack tip constraint on fracture resistance is examined under small scale yielding by way of the T-stress. As a final application, resistance curves for a deep and a shallow crack bend bar are computed. These are compared with experimental data.
机译：许多由于空洞生长机制而失效的金属在宏观上呈现出一个平面的破裂过程区域，该区域的厚度为一个或两个空洞，其特征是在空洞之间的韧带中发生强烈的塑性流动。在该区域之外，空隙几乎没有增长。为了对该过程进行建模，假定材料层包含预先存在的相似大小的空隙。可以用空隙之间的平均间距来确定层的厚度D。该层由线性维D的计算单元的集合表示。每个单元都包含某个初始体积的单个空隙。膨胀塑性的Gurson本构关系描述了孔在单元格中的生长，导致材料软化，并最终导致应力承载能力的下降。通过孔生长而软化的细胞集合构成了长度为l_1的断裂过程区。可以确定对应于l_1≈D和l_1 D的两种断裂机理。讨论了这些机理与断裂抗力之间的联系。已经进行了有限元计算来确定在小规模屈服下平面应变，I型裂纹扩展的抗裂纹扩展曲线。在初始裂纹之前，将一排排空的孔放置在对称平面上。这些单元格元素嵌入常规的弹塑性连续体中。在增加的载荷下，孔中的空隙生长并聚结以形成新的裂纹表面，从而使裂纹前进。计算了超过D的许多倍的裂纹扩展的阻力曲线。讨论了影响断裂阻力的参数，着重强调了材料的微观结构参数和连续性。通过T应力在小规模屈服下检查了裂纹尖端约束对抗断裂性的影响。作为最终应用，计算深裂纹弯曲杆和浅裂纹弯曲杆的电阻曲线。将这些与实验数据进行比较。

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