Research On Straightening Experimental And Simulation Of Thin Strip With Wave Shape

With the rapid development of home appliances,national defense,aerospace and other industries,especially car industry in our country,more and more amount of thin plate and strip was demanded and the requirement for quality of it was higher and higher.The wave shape of plate and strip was expanded and compressed continuously and the residual stress in plate and strip was loaded and unloaded repeatedly to realize the aim of straightening wave shape and equilibrium distributed residual stress during the process of straightening in the roller straightening machine.Nowadays,research on defects of nondevelopable flatness,such as center wave and boundary-wave,hasn't been developed into a complete theory.Especially,research on straightening model and technique became more difficult due to the complicated defects of thin metal plate and strip.Center wave was studied contrapuntally in this project to figure out straightening laws of wave shape.Considering the restriction in actual conditions,center wave was simplified as a local buckling deformation at piece of plate and strip,which was beneficial to make a wave shape.According to the characteristics of center wave,three parameters of wave height,wave width and wavelength are defined.The following conclusions were obtained through the comparison of wave shape with different parameters:(1)Parameters of wave height and wavelength had a big influence on straightening wave-shape plate and strip.The higher the wave height and wavelength is,the greater difficulty of straightening is.For the wave shape with high wave height,continuous micro wave whose wavelength is approximately half of the roller distance will be formed on original wave after straightening.(2)In the straightening process,the wave shape region extended along the width and length direction of the plate to produce compression deformation.The straightening process was mainly to change the longitudinal fibers to improve longitudinal residual stress of the plate but to improve the transverse residual stress little,which leaded to the fact that the transverse residual stress of center wave plate after straightening was smaller than longitudinal residual stress.The wave shape had an effect on the longitudinal stress near the wave shape region and had little effect on the transverse stress.(3)Through the stress and strain evolution research on finite element modeling of straightening process,research on different bending and pressure that effected stress and extention after straightening was carried out.The results showed that the stress of the plate after the straightening with negative bending will be high at center and low on both sides,and that the difference between the edge and the center of the plate increases gradually with the increase of the amount of bending roll.