Research On Finite Element Mechanics Analysis And Fatigue Life Of Working Roll Of Large Bending Machine

Sheet metal forming technology has been occupied an important position in the nationalproduct and manufacturing industry, with the high development of national product andeconomy and power of our country, sheet metal forming technology will gain greaterapplications. There are three methods of sheet metal forming: squeeze, drawing and rollforming. The equipment for sheet metal forming are punching machine, bending machine,reeling machine etc. In recent years, with the development of seafaring and shipbuildingindustry, especially the need for large warships, the importance of marine bending machine isgetting more and more attention.Large bending machine has strong forming force, theworking rolls sustain complicated stress, which leads it to fatigue phenomenon like crackle,abrasion, desquamation etc, sometimes even causes break. Working roll’s fatigue not only hasa bad influence on quality of drip molding, but also may causes great economic loss andsecurity problems. Research on working roll’s fatigue life of bending machine has a veryimportant significance.In this study, finite element model of bending machine is established, numericalsimulation on sheet metal rolling process is made under the process parameters of differentforming force, forming velocity and panel thickness. The calculation result is loaded in thefatigue software to compute the fatigue life of working roll. By analysing the fatiguecalculation result, the key parameters of influencing working roll’s fatigue life are found.Follows are the major research contents of this paper：1. In this paper，detailed analysis on unit type, material property, boundary condition andmesh partion of the model is made, on this basis, the finite element model of bending machineis established.2. On the basis of the FEA model, detailed analysis on working roll’s stress of eachforming stage is made. The research shows that, the maximal contact stress and equivalent stress of working roll are located in the contact area of working roll and supporting roll, thisarea is the dangerous point of fatigue. Besides, the maximal contact stress between upperworking roll and upper supporting roll is compared with the lower’s. Judging from thecalculation result of fatigue life, the minimum life point is located in the contact area betweenworking roll and supporting roll, which suggests the stress have great impact on fatigue.3. On the basis of the FEA model, the vertical comparison among influence of formingforce, forming velocity and panel thickness on the fatigue life of working roll is made.Research shows that, in a certain range, the heavier forming force is, the more damage will bemade to the working roll, and the lower fatigue life of working roll will be; the faster formingvelocity, the more damage to the working roll, and the lower fatigue life of working roll; themore thick panel thickness is, the more resistance and damage will be made to the workingroll, the lower fatigue life of working roll will be. With the same forming parameters, thefatigue life of upper working roll and lower working roll are compared. The result shows that,the structure and dimension design of the lower working roll is reasonable, which won’t causefatigue. Since the upper working roll endures more force and damage, which made it easy tofatigue. The dimension and material of the working roll should be improved when it isdesigned. In actual product, the forming force, forming velocity and the panel thicknessshould be controlled.4. On the basis of fatigue analysis, optimization of the lower working roll is made, theresearch shows that, without affecting the fatigue life of bending machine, the lower workingroll’s diameter could be reduced by50mm.