engleski

Computer simulation of mechanical properties and distortions during the quenching of steel

The research main stream in this paper is to upgrade the mathematical modelling and computer simulation of quenching of steel. Based on theoretical analyse of physical processes which exist in quenching systems of steel workpieces, the mathematical model for computer simulation mechanical properties and distortions during the quenching has been developed. The mathematical model of steel quenching is focused on physical phenomena such as heat transfer, phase transformations, mechanical properties and generation of stresses and distortions. Because of that the numerical procedure of computer simulation of steel quenching is divided in three parts: numerical calculation of transient temperature field, numerical calculation of phase change and numerical calculation mechanical behaviours of steel. The numerical procedure is based on control volume method. Relevant physical properties about which cooling rate depends are specific heat capacity of steel, heat conductivity coefficient of steel, steel density, linear thermal expansion, transformation expansion, and heat transfer coefficient of quenchant. Also, the transformation plasticity has been included in the model. Physical and mechanical properties that were included in such model have been predicted by taking into account their temperature dependences. In the developed computer program for simulation quenching the hardness at different workpiece points is estimated by the conversion of the calculated cooling time from 800 to 500 °C, t8/5 to the hardness by using both, the relation between cooling time, t8/5 and Jominy distance and the Jominy hardenability curve. Other properties of steel have been estimated based on as quenched hardness of steel. Based on the developed algorithm, computer software is developed for simulation of 3D situation problems, such as the quenching of complex cylinders, cones, spheres, etc., can be simulated. The established numerical model and computer softwaire for simulation of steel quenching can be successfully applied in the practical usage of quenching.

Computer Simulation, Quenching, Mechanical Properties, Residual Stresses, Distortions

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