STP803V1: On the Time and Loading Rate Dependence of Crack-Tip Fields at Room Temperature—A Viscoplastic Analysis of Tensile Small-Scale Yielding

    Little, MM
    Research assistant and professor of mechanics, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnie Institute, Troy, N. Y.

    Krempl, E
    Research assistant and professor of mechanics, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnie Institute, Troy, N. Y.

    Shih, CF
    Visiting associate professor of engineering, Division of Engineering, Brown University, Prodence, R.I.

    Pages: 22    Published: Jan 1983


    Abstract

    A finite-element analysis of stationary cracks in Mode I small-scale yielding is presented. It is asserted that the deformation of structural metals at room temperature and quasi-static loading rates can be significantly time dependent and so the theory of viscoplasticity based on total strain and over-stress is employed. Loading levels are controlled by the elastic stress-intensity factor K while loading rates are governed by the time rate of change of K. For loading rates varying over six orders of magnitude in the quasi-static range followed by subsequent periods of sustained loading, significant time dependence of the crack-tip fields is predicted. Interpreting the results using two different fracture criteria, it is predicted that the value of K at which crack growth is initiated is loading-rate dependent. Moreover, it also follows that strain-induced crack growth could be initiated during periods of sustained load. The results are strongly suggestive that time-dependent deformation should be considered in design against fracture even at room temperature. Appropriate design approaches, based on the special features of the viscoplasticity model employed, are proposed.

    Keywords:

    fracture, cracks, viscoplasticity, creep, relaxation, time dependence, finite-element analysis, Type 304 stainless steel, room temperature, elastic-plastic fracture


    Paper ID: STP37319S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP37319S


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