STP1332: On the Gurson Micro-Mechanical Parameters

    Zhang, ZL
    Senior research scientist and research manager, SINTEF Materials Technology, Trondheim,

    Hauge, M
    Senior research scientist and research manager, SINTEF Materials Technology, Trondheim,

    Pages: 20    Published: Jan 1999


    Abstract

    The Gurson model based approach has in recent years gained surprising popularity in describing ductile tearing phenomena. A lot of pioneer work has demonstrated the predicting power of the Gurson model. An important aspect in the application of the approach lies in how to characterize the parameters involved in the Gurson model. There is a non-uniqueness problem in determining the Gurson parameters, and how to link the Gurson parameters to material properties is generally open. In this study, the parameters involved in the approach are classified into gradient-sensitive parameter which is active when there is a strong strain gradient, and gradient-insensitive parameters, which include hardening parameters, constitutive parameters, initial micro- mechanical parameters and critical micro-mechanical parameters. It is suggested that the gradient-insensitive parameters are to be determined from smooth and notched tension tests where the strain gradient is not severe, while the gradient-sensitive parameter is fitted from fracture toughness tests. Regarding the fact that there is no built in coalescence criterion in the Gurson model, a physical mechanism based failure criterion for void coalescence is implemented, resulting in a complete Gurson model. It is pointed out that the initial parameters which describe the material's void nucleation law are the intrinsic parameters of a material, while the critical void volume fraction at void coalescence is a material specific response, which in general is dependent on stress state. A method based on the failure criterion is proposed for calibrating the initial parameters. According to the method, the number of unknowns in the approach can be reduced and the non-uniqueness problem of the micro-mechanical parameters for some materials can be solved.

    Keywords:

    Gurson model, micro-mechanical parameters, damage mechanics, material characterization, coalescence mechanism, ductile fracture, gradient effect, failure criteria


    Paper ID: STP14958S

    Committee/Subcommittee: E08.03

    DOI: 10.1520/STP14958S


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