LOCAL VARIATIONS OF STRAIN AND STRAIN-RATE IN ROLL BITE REGION DURINGROLLING OF STEELS

A combined experimental-numerical approach has been developed to quant ify the strain rate variation of the workpiece in the roll bite region . In this approach, cold lolling experiments at a production mill were conducted first. Then, tensile and microhardness tests were performed on workpieces before and after cold rolling to establish the relation ship between the microhardness and plastic strain of the material. Mic rohardness measurements were also conducted in the roll bite region on a partially cold rolled workpiece. A finite element rolling simulatio n was performed to predict the spatial variations of the strain and st rain rate. Through microhardness matching, it was Sound that the finit e-element predicted strains agree very well with those actually existi ng in the rolled workpiece. Consequently, the finite-element predicted strain rates, whose time-accumulation directly gave strains which mat ched the actual strains, were verified Finally, a finite-element simul ation of both cold and hot rolling was conducted to assess the effect of several major rolling parameters on the strain rate variation in th e bite region. Results show that the spatial variations of strain rare in the roll bite region are extremely nonuniform for both cold and ho t rolling.