The importance of experimental measurement of the stresses at the roll/workpiece interface in the study of rolling has long been recognized. The friction on the contact surface is still not well understood, and no work has been done to study the effect of changing workpiece aspect ratio in rolling. Based on previous studies, a new stress sensor was developed to measure the interface stresses in three directions (normal, rolling and transverse), and was then used in a series of experiments to study the effect of workpiece aspect ratio. Four groups of 3003-H14 aluminum billets with aspect ratios of 2.8, 4.8, 6.8 and 10.2 were tested.;The signal validation showed the sensor functioned well when the total roll separating force was under 10,000 lbf (4,540 kgf). The comparisons of the data for different aspect ratio groups showed that the stress distributions in normal and rolling directions were not affected significantly by changing billet aspect ratio. The normalized frictions in the rolling direction showed that the torque consumption per unit width for the wider billets was less than that for the narrow billets, i.e. the rolling became more efficient with increasing billet aspect ratio. The coefficients of friction were also investigated by using Coulomb's friction model, and were found to be under 0.1 throughout the contact surface for all rolling conditions tested.
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