Sample Machining

Turning samples on a lathe is a common preparation for tensile coupons. This is often required to produce the waisted sections required and any threading needed for the gripping of the samples. While this method of preparation is not required for most PIP samples, it is often desired to be able to PIP test the ends of tensile coupons produced using turning. Work by Warren and Guo[1] shows that turned surfaces lead to a significant hardened zone on the sample surface, greater than that of grinding. If PIP testing is carried on this turned surface layer, it can cause some discrepancies with conventional tensile testing. To this end it is important to grind off this hardened layer before PIP testing to achieve more consistent results.

[1] Warren, A. W., & Guo, Y. B. (2006). On the clarification of surface hardening by hard turning and grinding. Trans North Am Manuf Res Inst SME, 34(April), 309-316.