An Approximate Model for Local Strain Variation over Material Thickness and Its Applications to Thick Plate Rolling Process

초록

This paper presents a three-parameter approximate model which computes the local strain variation over thickness direction of thick material in the roll gap. The three parameters were determined through finite element analysis. With the proposed model, we then carried out a series of plate rolling simulation to examine the effect of the arithmetic average aspect ratio (ratio of contact length between work roll and material to mean material thickness in the roll gap) and reduction ratio on the local strain variation over material thickness as material goes through rolling at many passes. Results reveal that a certain amount of relative difference between local strain at center and that at surface always exists as arithmetic average aspect ratio increases for whole plate rolling process. It also shows that the magnitude of local strain at material center is only 69% of that at surface during rolling no matter how we regulate incoming material thickness, radius of work roll, reduction ratio, roll speed and friction condition when arithmetic average aspect ratio is greater than 1.0. It has been found that the heavy reduction with arithmetic average aspect ratio, 0.9 might be an optimum condition for refining grain size over material thickness in an approximately uniform manner.

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