Research On Roll Bending Fracture Prediction Of Aluminum Alloy Profiles Considering Anisotropy

Owing to the characteristics of light weight,high strength and excellent comprehensive performance,aluminum alloy profiles have become the key materials for high-speed trains.With the advantages of material saving,energy saving and high production efficiency,roll bending has broad application prospects in the forming of profile parts.Due to the different orientation distribution of the internal grains along the extrusion direction in profiles,the profiles show anisotropy in mechanical properties,which affects the fracture prediction during roll bending.Therefore,in order to accurately predict the fracture of aluminum alloy profiles during roll bending,their anisotropic behavior needs to be taken into consideration.The main research contents and results of this paper are as follows:(1)Uniaxial tensile tests were carried out on the wings and webs of 6005 A aluminum alloy profiles at different positions,and their anisotropy were quantified by the anisotropy index IPA.The finite element model of aluminum alloy profiles was established using von Mises,Hill48 and Yld2004-18 p yield criteria respectively,and the parameters of different models of 6005 A aluminum alloy profiles were obtained by EBSD measurement and crystal finite element simulation.Comparative tensile test results show that the established anisotropic models can describe the anisotropy of aluminum alloy profiles.(2)Three kinds of 6005A-T4 aluminum alloy profiles with different sections commonly used in China’s high-speed railway were numerically simulated and experimentally researched.The ductile fracture criterion was embedded into the finite element software through Python script program,and the crack initiation location,crack initiation time and minimum roll radius of different profiles were calculated.We compared and analyzed the difference between the predicted fracture value using the three yield criteria and the roll bending experimental value.The results show that the prediction results of the fracture model based on the anisotropic yield criterion are in better agreement with the experiments.Among them,the Yld2004-18 p yield criterion has the best prediction performance with the error less than 3%.(3)The influence of forming parameters such as roller center distance,roller diameter and roller speed on roll bending fracture of 6005 A aluminum alloy profile was simulated and analyzed.The results show that(i)the appropriate increase of the center distance of rollers is beneficial to avoid the fracture caused by excessive local force when the rollers are lifted up,and the moderate center distance of the aluminum alloy profile set between 200 and 220 mm can effectively suppress the occurrence of crack defects in the roll bending process;(ii)the diameter of the rollers has little effect on the fracture of aluminum alloy profiles during roll bending;(iii)when the roll speed gets higher,the transition zone of the profile roll bending is longer and cracks are not easy to occur,and the appropriate roll speed for roll bending of aluminum alloy profiles is about 1 rad/s.(4)We analyzed the stress characteristics of aluminum alloy profiles during bending process,and studied the influence law of deformation passes and the amount of deformation in each pass on cracks of 6005 A aluminum alloy profiles.The simulation results show that the roll bending fracture of aluminum alloy profiles can be avoided through the reasonable design of forming passes and deformation amount per pass.The influence of cyclic loading on the deformation of aluminum alloy was studied by tensile test,and the cause of local error in roll bending was analyzed.A method of local profile modification based on multi-point flexible module was proposed.Local correction experiments show that this method can improve the curvature discontinuity of aluminum alloy profiles after forming,improve the forming accuracy and reduce the risk of fracture.