Research On Backup Roll For4300mm Wide Plate Mill With Abaqus Software And Calculation Of The Fatigue Life

Four-high mill back-up rolls withstand a complex alternating stress in the course oftheir work，the working condition of the backup rolls of the hot-rolling mill are moreharder. If the material selection, structure design and fabrication process of the backuprolls are unreasonable, or the accident of jamming and misoperation are happened, thefatigue failure of backup rolls will be produced. Unusual failures of the compound rollsinclude: peeling off on the roll body, breaking down of roll body, breaking down of rollneck, cracking of roll body and so on. The mill roll consumption has greatly increasedthe cost of production.This paper takes the4300mm4-high rolling mills as the object of study. It firstlyanalyzes the stress state of the4-high rolling mills by using the Hertz contact theory, andthen McEwan’s and Jonhson’s research achiecements on the stress field of the cylinder’scontact area are introduced respectively; and by using the knowledge of themicro-tribology it also analyze the micro-slip phenomenon between rollers using some ofthe micro-tribology knowledge.The type of the backup roll chamfer has a large impact on the internal stress field ofthe backup roll. And a reasonable chamfer will greatly alleviate the stress concentrationson the end of the backup roll introduced by the roll bending. In this paper we willintroduce a new type of chamfer, establish a3-D finite element model of the4-high milland then calculate the stress field by using ABAQUS. After that we establish the finiteelement model of4-high mill under different type of chamfers, obtained their stress field.These result obtained by ABAQUS can prove that the new type of chamfer in the end ofthe backup rolls are very effective to alleviate the stress concentration.Currently there are two main methods to estimate the fatigue life; they are nominalstress method and local stress-strain law respectively. The normal stress method is basedon the nominal stress of the parts and stress-life relation of the material; the resultsindicate that the method has good suitability to the parts under high stess cycle. The localstress-strain law is based on the local strain and strain-life of the material. It has abroadflexibility from the low stress cycle to high stress cycle. In this paper we will calculate the fatigue life of the backup rolls with different type of chamfers. The results show thatthe local stress-strain method is more suitable to estimate the fatigue life of the backuproll. After that we calculate the fatigue life of the backup rolls with different type ofchamfers, and the result show that the new type of chamfer is more effective to increaseworking life of the backup roll, meanwhile this research can establish a foundation forthe fatigue crack propagation of the backup roll.