Analysis Of The New Method Of Indirect Evaluation Of Contact Stress During Cold Rolling Based On Numerical Simulation

Strip rolling is an efficient and widely used production method.In rolling process,the abnormal vibration of rolling mill has been restricting the production quality(i.e.strip thickness,strip flatness and defect-free-surface).The vibration of the rolling mill(vertical vibration and torsional vibration)is coupled by the rolling interface,and the reason of the abnormal vibration of the rolling mill is usually the change of the contact stress distribution of rolling interface.Therefore,it is very important to study the distribution of contact stress(normal stress and shear stress)in rolling interface in order to suppress vibration and obtain better slab quality.The indirect measurement of the contact stress of rolling interface avoids the disadvantages of traditional measurement method(the sensor will be in contact with the strip).It only needs to measure the internal strain of the roll,then based on a kind of elastic mechanics inversion algorithm the contact stress of rolling interface can be inversed.However,the inversion algorithm is based on plane strain state,and it is difficult to measure the strain in plane strain section.Therefore,this article puts forward a new indirect measurement method to measure the contact stress of rolling interface.The strain of plane strain section is deduced by measuring the strain in the non-plane strain section of the roll and a mapping relation,and then the contact stress of the rolling interface is deduced through the inversion algorithm.The main contents of this paper are as follows:(1)Starting from the basic principle of indirect measurement method,its error sources and influencing factors are analyzed.Then the availability of the inverse analysis under the condition of plane strain is verified using two-dimensional finite element simulation.The specific relationships of reconstruction errors of contact stress and the corresponding influence factors are studied,and the appropriate sampling location and sampling frequency are obtained.(2)A new measuring method for contact stress during cold rolling process is presented.First,Measuring strain components of the non-plane strain cross section.Second,deducing strain components of the plane strain cross section based on the strain components' mapping relationship between plane strain cross section and non-plane strain cross section.Finally,calculating the contact stress of the rolling interface by the strain component of the plane strain section.The strain components' mapping relationship between different cross sections is studied by 3-d numerical simulation.(3)Through the experiment,the strain components of the non-plane strain cross section are measured.The contact stress of the rolling interface is performed by combining the above mapping relationship and,the rolling torque is obtained by the shear integral.The accuracy of the new measurement method is verified by comparing the torques' relative error between the torque measured by the torque strain gauge and the torque calculated by the integration.