COMPUTING STRAIN FIELDS FROM DISCRETE DISPLACEMENT-FIELDS IN 2D-SOLIDS

The analysis of strain localization and damage evolution in materials requires appropriate experimental techniques to verify the complex mat erial behaviour in the damaging zone. Modern techniques are now availa ble to measure the displacement fields in small zones of a material, a nd a complementary procedure is needed to derive the accompanying stra in fields. The knowledge of the local strain fields gives direct infor mation with respect to the applied constitutive model and serves as in itial input for most parameter estimation procedures, while the fine-t uning of the model parameters should be done by comparing the computed and measured displacement fields. This study presents a theory to com pute strains from the displacements in a discrete set of points and is particularly useful in the post-processing of experimentally measured displacement fields. The theory is fully elaborated, and some practic al examples are given. A comparison is made with some analytical solut ions, and the effect of noise on the input data is evaluated. Copyrigh t (C) 1996 Elsevier Science Ltd.