Strain Localisation and Damage Measurement by Full 3D Digital Image Correlation: Application to 15‐5PH Stainless Steel

The objective of this paper is to propose a method for measuring damage in ductile materials, from its inception to rupture. In the first stage of damage, which occurs before localisation, the usual method for determining damage through the measurement of stiffness variation is used. A damageable elastic–plastic model of the modified Lemaitre/Chaboche type is identified from these tests. An original method is proposed for measuring damage following the initiation of strain localisation. This method is based on a full 3D image correlation analysis using four cameras. The principle of the method consists in identifying the damage through tensile experiments on thin, flat‐notched specimens subjected to tensile loading. Speckles are applied on both faces of each specimen in order to follow the strain fields on the two faces at the same time. These two strain fields are digitised simultaneously by two synchronised sets of two digital cameras. This paper shows how this method enables one to identify strain localisation and deduce the evolution of damage directly. Here, the method is developed for 15‐5 PH stainless steel.