Modeling of Dimensional Changes and Residual Stresses After Transformation-Free Cooling

    (Received 9 January 2014; accepted 28 April 2014)

    Published Online: 2014

    CODEN: MPCOAD

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    Abstract

    Predicting thermal distortions and residual stresses after steel heat treatment is a complex task in which the solution involves the use of a number of process parameters and nonlinear variation of steel properties. Former investigations in transformation-free cooling processes of long cylindrical work pieces in a gas nozzle field showed a typical behavior of the dimensional changes which indicated the possibility of introducing dimensionless numbers to predict thermal distortions. It was found that the changes in the dimensions of cylinders correlate well with only a few dimensionless numbers which are defined as function of shape and dimensions of components, its initial temperature, temperature of the quenching media, heat transfer coefficient, heat conductivity, heat capacity, density, thermal expansion coefficient, Young's modulus, Poisson's ratio, yield strength, and strain hardening behavior. For a systematic investigation of impacts on dimensional changes and residual stresses after transformation-free cooling, a representative group of 28 austenitic stainless steels was selected from literature. Their properties were statistically analyzed and three representative combinations of steel properties have been selected. The numerical simulations were carried out by use of the commercial finite element (FE) program SYSWELD 2005 with the aim to predict residual stresses and change of dimensions of a long cylinder made of austenitic stainless steel after gas cooling from the high temperature down to room temperature. The FE results were analyzed with the nonlinear regression methods and with genetic programming methods. From these analyses, two dimensionless mathematical models were proposed, one for prediction of thermal distortions and the other for prediction of equivalent residual stresses. The proposed dimensionless regression models allow the portability of the calculation results to similar cooling conditions (temperature independent heat transfer) for a transformation-free cooling of long cylinders made from any austenitic steel selected from the considered representative group of steels.


    Author Information:

    Landek, Darko
    Univ. of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Quenching Research Centre, Zagreb,

    Lisjak, Dragutin
    Univ. of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Quenching Research Centre, Zagreb,

    Lübben, Thomas
    Stiftung Institut für Werkstofftechnik, Bremen,

    Župan, Josip
    Univ. of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Quenching Research Centre, Zagreb,


    Stock #: MPC20140005

    ISSN: 2165-3992

    DOI: 10.1520/MPC20140005

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    Author
    Title Modeling of Dimensional Changes and Residual Stresses After Transformation-Free Cooling
    Symposium , 0000-00-00
    Committee A01