Cellular Automaton Simulation On Thermoplastic Healing Of Internal Microcrack In Metal

During the processing of metal materials forming and the service processing, heat,force, environment are the main influencing factors that bring defects like micro cracks(hole) into metal components.The existence of cracks destroy the continuity of the metalmaterial texture. when encountered with stress loads, it may cause stress concentration inthe metal components, and the material tearing is often the performance results of stressconcentration, the existence of microcracks is also the result of unstable fracture、lifereduction、and even scrap of metal component. So, the controlling and prediction of thedefects in the material, as well as the repairing study of inner crack in metal are very urgenttasks, which has a far-reaching significance by improving the service life of metalmaterials and the safety coefficient of engineering construction.Aviation7050aluminum alloy is selected as the researching object based on thesubject, by using real experimental stress-strain datas of the single pass hot compressionwhich are achieved by Gleeble-3500thermal simulation pressure machine, the flowingstress mathematical model and dynamic recrystallization model of this material areestablished, which provide calculated parameters and theoretical support for CA simulationwork.Based on the increasing maturity of the cellular automaton (Cellular Automaton,referred to as CA) technology and the advantages of computer programming, the CA rulesof microstructural evolution of microcrack during thermoplastic healing includingtopological deformation mechanism, the dislocation density evolution mechanisms,“Cracks prograing” means, dynamic recrystallization behavior,the “gas-solid” surfaceenergy driven theory, grain growth model were programmed on Microsoft Visual C++platform. For the different characteristics of crack surface and grain boundary, the“gas-solid” surface energy and grain boundary energy driving the growth of grain indifferent ways are proposed in the recrystallization process.The whole microcracksrepairing process in metal materials under the conditions of thermoplastic dynamic recrystallization is simulated theoretically. On the basis of this framework, by debuggingprogram parameters, thermoplastic conditions which affect the healing of internal cracks,such as:strain, temperature, strain rate，crack morphology, this three main factors should beanalyzed and explored, This work summarizes the evolution law and characteristics ofcrack repairing process, the effect of different factors on crack healing are also studied.Finally, the microcrack repairing model of cellular automaton simulation under theconditions of dynamic recrystallization is established, the physical interface nature that canmore reflect the microcrack repair mechanism is discussed.The advantage of CA model,has a certain guiding significance to the development of production practice on heatprocessing and related simulation software.