Extraction of Fracture Toughness Parameters by Ring-Notched Small Punch Specimen Using Cohesive Model

doi:10.16183/j.cnki.jsjtu.2020.129

Abstract

Abstract:

The fracture toughness of in-service equipment and irradiation materials can be obtained from the ring-notched small punch specimen. The cohesive model was used to describe the ductile fracture behavior and crack propagation process of T91 steel, and the two parameters of material required by this model were calibrated by using the inverse finite element method. The successful implementation of this method requires that the load-displacement curve in the fracture damage stage is sensitive to the two model parameters, which can be optimized by the geometric design of the specimen and notch. The influence of the ratio of diameter to thickness, the depth of notch, and the presence or absence of prefabricated cracks on parameter sensitivity was studied, and the optimized design of the ring-notched specimen was obtained, based on which, a set of parameters was selected for finite element simulation to obtain the load-displacement curve. This curve was chosen as the target, and the genetic algorithm and the random walk algorithm were used for iterative fitting by using the inverse finite element method to extract the parameters of the cohesive model. The calculated results show that the error between the obtained parameters and the pre-selected parameters is less than 1%, which verifies the sensitivity of the specimen design and the accuracy of the inverse finite element method.

Key words: small punch, cohesive model, parameter sensitivity, inverse finite element method, fracture toughness

CLC Number:

TB302.5

ZHANG Yu, LIU Haiting, WENG Lin, SHEN Yao. Extraction of Fracture Toughness Parameters by Ring-Notched Small Punch Specimen Using Cohesive Model[J]. Journal of Shanghai Jiao Tong University, 2021, 55(7): 850-857.

Figures/Tables 10

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物理量	输入参数组1	反算结果	输入参数组2	反算结果
σ_c/MPa	800	794.4	1000	970.1
Γ₀/(MPa∙mm)	5	4.88	6	6.36
迭代次数与时间	约1500次,72 h

物理量	输入参数组1	反算结果	输入参数组2	反算结果
σ_c/MPa	800	798.605	1000	1001.37
Γ₀/(MPa∙mm)	5	5.03555	6	5.99272
迭代次数与时间	约500次,24 h