TRIBO MODELLING IN STRETCHING OF THIN SHEETS

Abstract

Stretching of sheet metal is a typical stress-strain scheme characterized by positive values of principal normal stresses, one contact surface between the sheet metal and the tool, and relatively small sliding speed at that zone. strain occurs only in the hole of the die, while the work piece flange is held firmly between the holder and the die. in course of forming the outer area of the work piece is free – not in contact, and so for sufficiently large ratio of punch radius and sheet metal thickness, the conditions of the plain stress state can be applied. In deep drawing of parts of complex geometry, parts of car body for example, such stress- strain scheme exists under the punch face and in the zone of punch rounding. in laboratory conditions the stretching has been used for years in the evaluation of the sheet metal formability for deep drawing (erichsen' s test, olsen' s test).