Analysis Of Springback And Crack In Closed Roll Bending Process

Rectangular tube,as a kind of economical and efficient profiles,plays an indispensable role in various industries.However,the rebound and crack defects in the production and forming process of rectangular tube damage the economic benefits,so it is necessary to study it.In this paper,numerical simulation and experiment were combined to study the forming process of rectangular tube roll bending,to reveal the influence law of technological parameters on the springback and damage value in the process of roll bending,and to obtain the optimal process optimization scheme,which provides theoretical guidance for the actual production of the factory.Topological mapping principle of roll roll pass design,and is based on the rectangular tube pass test to verify the exactness of the pass design,and analysis of the friction coefficient,roll speed,roll diameter,initial diameter circular tube and pipe thickness of process parameters on the roll bending process of forming the thickness of the tube crosssection node distribution,calculated the pipe metal flow law of roll bending process.The springback model of roll bending was established and calculated by MARC software.The thickness and size data of the rectangular tube were extracted and compared with the test results.The results show that the springback simulation model has high accuracy.Based on this model,the influence of pipe thickness,pipe diameter,rack spacing,distribution mode of pressure-down and material yield strength on the distribution of springback of rectangular pipe fittings was studied.In order to accurately predict the cracks generated by rectangular tube roll bending,Oyane ductile fracture criterion was used to conduct research.Taking 304 stainless steel tube as the research object,the material parameters of Oyane criterion based on 304 stainless steel were calibrated through finite element simulation and tensile test on standard specimens,specimens with rounded corners and shear specimens.By coupling the fracture criterion to the finite element model to calculate the fracture damage value,the influence of roll speed,tube thickness and corner radius on the distribution of the damage value in the rectangular tube roll bending process is analyzed,and the parameters that have a greater influence on the damage value are obtained.Based on the response surface method(RSM),the influence law of each process parameter on the springback and damage value of the forming pipe was analyzed.The response surface model of rectangular pipe springback and crack was established with the help of Design-Expert,a multivalate nonlinear regression software.The variance analysis of the response model was carried out,and the mathematical expression of the response model was obtained.Determine the factors that have great influence on springback and crack,and finally get the best process optimization scheme.