Research On Stretch-bending Forming Process Of Stainless Steel Outer Cover Plate Of Escalator

Stretch-bending is a forming process of sheet metal,which is widely used in vehicles,rail transit,aerospace and other fields.Due to the complex forming process,the springback after unloading is related to many factors such as material properties,stretching amount,friction coefficient,mold radius,etc.Therefore,it is very important to fully study the influence mechanism of these factors on the springback to improve the forming accuracy of the product.This paper takes the stainless steel outer cover plate of the escalator as the research object,analyzes the distribution of stress and strain on the section in the deformation stage,and uses the ABAQUS software to study the influence law and mechanism of different process parameters on the springback,which provides a certain basis for the selection of process parameters in production.The following are the research contents and conclusions of this paper:(1)In this paper,the tensile test of stainless steel SUS430 material is firstly carried out to obtain its mechanical property parameters;then the ABAQUS software is used to model and simulate the stretch-bending forming process of the outer cover,and the stretch-bending experiment is carried out verify its accuracy.(2)Based on the loading method of pre-stretching-bending-stretching,the three deformation stages are analyzed,the distribution of stress and strain on the section under different stretching amounts is described,and the residual stress on the section after unloading is analyzed.The research shows that: with the increase of the stretching amount,the whole section gradually enters into plastic deformation and the residual stress distributed on the section after unloading is small.(3)The influence of material parameters,stretching amount,friction coefficient and die radius on the springback is studied through the simulation analysis of the outer cover plate tension and bending.The research shows that the springback decreases with the increase of the elastic modulus of the plate,increases with the increase of the yield strength;With the increase of the stretching amount,the springback tends to decrease.When the stress neutral layer does not deviate from the section of the outer cover plate,with the increase of the cladding stretching amount,the springback decreases to a greater extent,and the normal warping defect can be avoided by applying a certain amount of supplementary stretching;the friction between the profile and the mold prevents the tensile force from being uniformly transmitted to each section of the profile.As the friction coefficient increases,the springback tends to increase.The smaller the die radius,the greater the bending degree of the profile and the greater the springback after unloading.Among the two die radius compensation methods,the chord cut method has higher iteration accuracy than the difference method.(4)Taking the outer cover plate as the object,the effects of four kinds of stretching amount distribution methods: uniform distribution,logarithmic increasing distribution,sinusoidal increasing distribution and linear increasing distribution on its springback under the same stretching amount are studied.The research shows that when the stretching amount is 3%,the plastic deformation at the inner side of the section under different distribution methods is quite different,and the springback under the linear increasing distribution method with small stretching amount applied in the early stage is the smallest,The reason is that the section does not fully enter the plastic tensile deformation state at this time,and the plastic deformation degree on the inner side of the section is the largest under the linear increasing distribution,so the springback after unloading is the smallest;When the stretching amount is 5%,the springback difference under different distribution methods is small,and the springback under the uniform distribution with large stretching amount applied in the early stage is the smallest.The reason is that at this time,the section fully enters the plastic stretching deformation state,and the overall plastic deformation degree of the section is the largest under the uniform distribution,so the springback after unloading is the smallest.