The Partitioning of Plastic Energy in Cutting Tests

Cutting analyses incorporating chip bending in addition to shear yielding and fracture toughness have been presented. A plastic bending term (eb/γ)(hc/h) is included which corrects the yield stress, σY, determined from the cutting data. The experimental data for seven polymers derived from measuring both the chip thickness and the residual radius of curvature show that the contribution of bending is up to about 12%. This gives a correction to σY of about the same order but Gc is unaffected as (eb/γ)(hc/h) is a factor independent of the cutting depth. The corrected σY values are compared with the σY values in simple compression and it suggests a work hardening effect for the polyolefines. Also, the low bending strain in the chips of HMWPE and PP may be attributed their large degree of non-linearity observed in the compression test.