Influence of the shape of stamped sheet parts on their springback and its elimination during pulse electrohydraulic calibration

Abstract

Starkov N. V. Influence of the shape of stamped sheet parts on their springback and its elimination during pulse electrohydraulic calibration. Material working by pressure. 2020. № 1 (50). Р. 159-164.

In recent years, high-strength steels with a tensile strength of 800 - 1100 MPa have become the subject of research by enterprises and scientific institutions that study their properties in sheet metal stamping processes. Along with high strength these steels meet the requirements of a high level of plasticity, manufacturability  when performing assembly operations.

High strength and significant strain hardening lead to a deviation of the dimensions of the stamped parts in comparison with the dimensions specified by the tool. This is a consequence of the action of elastic stresses, which are unevenly distributed throughout the thickness of the workpiece after removal of the deforming load. This springback is typical for parts in the form of a straight or curved groove; in the form of an open complex profile and other similar details. Springback almost absent for parts in the form of a body of revolution or box-shaped parts with a closed contour and a flange or without it.

Pulsed electro-hydraulic (EH) parts calibration is the most effective process for eliminating springback of parts after stamping on mechanical presses. In this case, EH calibration of  high-strength steels parts should be performed with preliminary creation of stresses in them close to the metal’s yield point. This allows a more complete use of the stress relaxation process, in which the elastic deformations of the metal transform into plastic ones.