A new experimental approach to evaluate friction in ring test

A real-time measuring method is proposed to evaluate the friction by using a ring test. In this approach, two experimental procedures are developed: the image processing that used to measure the radius of contraction inner surface (convex forming) at the high friction condition and the measurement of strain by using strain gage that is used to find the expansion inner radius (concave forming) at the low friction condition. An hardening material, aluminum, annealed at 1100 °F, is used for theoretical comparison and non-hardening materials that consist of tin (63%) and lead (37%) is adopted to calibrate various friction conditions. The size of specimen is machined to the standard size so the ratio of outer diameter to inner diameter to thickness is 6:3:2. A theoretical model of non-constant shear friction approach is used to construct the calibration curves. It is found that these methods present an excellent agreement with the experimental data and the results of prior literatures, specifically in evaluating the friction situation at concave forming.