Research Of Rolling Stress State And Edge Crack Damage Of AZ31 Magnesium Alloy

The magnesium alloy is a well-known light-weighted metal.Due to its high specific strength,low density and high damping,there is broad application prospect in the fields of transportation,telecommunication,aerospace,and others.Rolling is a way to product magnesium alloy sheets.The edge crack phenomenon caused by complex load and severe plastic deformation in the rolling process lead to low productivity and high cost.As a result,the popularization and application of magnesium alloy sheets are limited.In this paper,numerical simulations were carried out to study the law of strain distribution of AZ31 magnesium alloy sheets in rolling deformation zone.The results were compared with different deformation processes.Moreover,the constitutive relation of magnesium alloy was established.Based on experiment results and simulation results,the parameters of GTN model were defined,and influence of these parameters were discussed.Finally,measurements to inhibit edge crack phenomenon in rolling process were proposed,which provided the theoretical basis for the rolling production of magnesium alloy.Main conclusions found are as follows:(1)The central area of rolled steel plate is in three-dimensional compressive stress state,and the order is according to stress value: the normal compressive stress,the transverse compressive stress,and the rolling compressive stress.Along the width edge of plate,the normal compressive stress and the transverse compressive stress gradually reduce from the center of the plate to the edge of the plate,and the transverse compressive stress of the edge reduces to zero.The rolling normal stresses gradually change to tensile stress from compressive stress.(2)The friction coefficient,reduction,and the thickness of plate can all influence the stress distribution rule in rolling zone.The analysis of rolling normal stresses in rolling zone showed that with the increase of friction coefficient and reduction,the inflection point of rolling compressive stress that changed from compressive stress to tensile stress moves from the edge of the plate to the center of the plate and the maximum value of rolling tensile stress increases.In other hand,with the increase of the thickness of plate,the inflection point of rolling normal stresses moves from the center of the plate to the edge of the plate,and the maximum value of tensile stress reduces.Therefore,either to increase the thickness of plate or to reduce friction coefficient and reduction can reduce edge tensile stress effectively,and thus reduces the occurrence of edge crack phenomenon.(3)By means of tensile experiments,the parameters of GTN damage model were defined.From simulation perspective,the reasonable finite element model were established.The numerical simulation of rolling process were conducted in ABAQUS.The research showed that the maximum damage value of the rolled piece's edge increases with the increasing of reduction ratio and reduces with the increasing of roll radius.The occurrence probability of edge crack can be reduced remarkably when the rolling temperature is between 300? and 400?.