An Experimental and Analytical Method for Investigating Plastic Flow in Form Tapping

Abstract

While threaded holes made by cutting taps result in material removal, in form tapping, the tap displaces the work material by plastic flow to form the thread section. The aim of the present work is to study, both experimentally and analytically, the 3D-plastic flow in form tapping of low-alloy steels. An experimental technique for producing and measuring the 3D displacement is proposed. Experimental results of displacements are used in the analytical analysis. The Green-Lagrange strain tensor is determined from the measurements obtained. The deviator stress tensor is calculated by using the constitutive law of the work material. The stress equilibrium allows the stress distribution resulting from the form tapping process. The results obtained show the quantification of the 3D-plastic flow, demonstrating that the external layer of the thread is strongly deformed. KEY WORDS: form tapping, plastic flow, thread formation.