Unified Constitutive Modelling On Creep Aging And Springback Modification Of Forming Tool Surface

Abstract:Creep age forming (CAF) technology was developed to solve the forming problem of the large integral panel. As a relatively new metal forming method, CAF is a combined forming and aging hardening process utilizing metallic creep, aging and stress relaxation characteristic. However, some springback will centainly occur in the component after one CAF. According to this challenge, this paper established a set of effective solutions using2124aluminum alloy as the research object, which include unified constitutive modelling on creep aging, finite element analysis of the forming process, springback modification of tool surface and typical component forming test verification these four parts, the research content and results are as follows:(1) Based on metal lasting creep testing machine, mechanical performance testing machine, transmission electron microscope test and some analysis methods, the marco creep behavior and micro precipitates evolution process in the CAF of2124aluminum alloy was quantiutatively analyzed, and its creep aging mechanism was revealed;(2) One set of unified constitutive modelling on creep aging of high strength aluminum alloy was established, based on the analysis of the strengthen interaction mechanisms between the macroscopic creep deformation and the micro precipitates evolvement in the CAF process; and the material constants in the constitutive model were obtained via the particle swarm optimization, which achieved the regression analysis of the creep and aging precipitation behavior of2124aluminum alloy, and the constitutive model was well optimized to fit the experimental data.(3) The unified constitutive equations established was further developed via the Fortran language and embedded into the finite element analysis software MSC.Marc to simulate the creep age forming process of aluminum alloy flat plate, then the change of the stress, strain, springback and micro precipitation characteristics of the component were analyzed; lastly, experimental research were carried out under the same conditions to prove the correctness of the finite element simulation results.(4) A new tool surface weighted modification algorithm was developed based on the FEM prediction of springback. The compensate results between the new algorithm and other overall compensation algorithms on the tool surface shown that, the new weighted algorithm has better convergence and accuracy, as it not only can achieve the compensation rapidly and accurately, but also overcome the fluctuation defects of forming error with the increasing compensation number via the traditional algorithm.(5) According to a typical aerospace panel structure sample, creep age forming tool surface compensation was carried out; and the creep age forming mold clamp was designed based on the analyzed tool surface; then the result of panel forming test further proved the correctness of the finite element simulation results and the accuracy of the weighted compensation algorithm. Full total figures75, tables6, and reference91...