Abstract The Gurson-Tvergaard-Needleman damage model is implemented in Small Punch (SP) finite element model with the purpose of evaluating the influence of crack initialization and propagation on the SP force–displacement ( F - v ) curves and the maximum force, F m , which is used for estimating the R m . Five materials, significantly different in R m and ductility are investigated. Numerical calculations are performed and compared to the experimental measurements to evaluate the accuracy of the model. It is shown that the model is capable of capturing crack initialization in cold worked 15-15Ti stainless steel samples with different levels of ductility, both in terms of the number of cracks and their positions. For these two materials and the more ductile P91, P92 ferritic/martensitic steels, the simulations indicate significant impact of damage on the F - v curves in the vicinity of the maximal force, F m . This can significantly influence the estimation of R m from the F m and v m points. However, the model tends to predict the crack initialization at a larger displacement compared to the experiments.

中文翻译：

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半脆性材料小冲孔试验裂纹的研究

摘要 Gurson-Tvergaard-Needleman 损伤模型在Small Punch (SP) 有限元模型中实现，目的是评估裂纹初始化和扩展对SP 力-位移( F - v ) 曲线和最大力F 的影响。 m ，用于估计 R m 。研究了 R m 和延展性显着不同的五种材料。执行数值计算并与实验测量值进行比较以评估模型的准确性。结果表明，该模型能够捕捉具有不同延展性水平的冷加工 15-15Ti 不锈钢样品的裂纹初始化，包括裂纹数量和位置。对于这两种材料以及韧性更好的 P91、P92 铁素体/马氏体钢，模拟表明损伤对最大力 F m 附近的 F-v 曲线有显着影响。这会显着影响从 F m 和 vm 点对 R m 的估计。然而，与实验相比，该模型倾向于预测更大位移下的裂纹初始化。