Open AccessSimplified measurement of the strain to fracture for plane strain tension: On the use of 2D DIC for dual hole plane strain tension mini Nakazima specimens with dihedral punch
Author(s) -
Morwan Adlafi,
Bertrand Galpin,
Laurent Mahéo,
Christian C. Roth,
Dirk Mohr,
Vincent Grolleau
Publication year - 2021
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/1157/1/012058
Subject(s) - digital image correlation , materials science , plane stress , fracture (geology) , tension (geology) , composite material , ductility (earth science) , bending , stress (linguistics) , plane (geometry) , structural engineering , strain (injury) , sheet metal , stress intensity factor , fracture mechanics , ultimate tensile strength , geometry , finite element method , creep , mathematics , engineering , linguistics , philosophy , medicine
A plane-strain-tension stress state leads to a minimum in ductility in most micro-mechanical and phenomenological fracture models as well as Forming Limit Curves. Hence, this stress state plays a crucial role in many applications and a reliable measurement of the strain to fracture under plane strain tension is of particular importance when calibrating modern fracture initiation models. Recently, a new experimental technique has been proposed for measuring the strain to fracture for sheet metal after proportional loading under plane strain conditions. The basic configuration of the novel setup includes a dihedral punch applying out-of-plane loading onto a Nakazima-type disc-shaped specimen with two symmetric circular cut-outs. 3D Digital Image Correlation (DIC) is used to measure the surface strains of the specimen up to fracture. In contrast to the widely used V-Bending test, the maximum obtainable strain is not limited when using this set up, and fracture will always initiate after proportional loading in a plane strain tension stress state. In the present study, a major simplification of the testing methodology is proposed, reducing from 3D DIC to a simple 2D DIC method for measuring the fracture strain. Comparisons are presented on three metals, a 1.5 mm thick DP600 steel, a 0.8 mm thick DP450 steel and a 1.2 mm thick AA2024 aluminum alloy.