Assessment of Analytical Models of Pure Bending of Sheet Materials Using the Digital Image Correlation Method

Abstract

Bending of sheet materials is a common forming mode for shaping sheet components. Although many numerical models of bending, both analytical and numerical simulations based, are available in the literature, extensive experimental validations have been rather limited. A new bend test method and complementary three-dimensional finite element (FE) simulation of the experiments are employed to assess the predictions from an advanced analytical and FE model of pure bending of aluminium sheet materials. The experimental set-up developed and utilised is an open concept design that allows access to the tensile surface and through-thickness region in the vicinity of the specimen bend line to continuously record images of the deforming specimen with two cameras. The specimen images are analysed for strains using an online strain mapping system based on digital image correction method. Tangential strain distribution results from the models in terms of material thinning in the bend region are compared with those from the experiments on AA2024 aluminium sheet material by considering the responses from the specimen edges and mid-width regions at the bend line. Furthermore, the tangential and radial stress distributions on the through-thickness section of the specimen from the analytical model are compared with those from the FE model. The results from experiments, FE model and analytical model are compared and discussed in the light of the experimental data and the assumptions involved in the development of the models.

Neutral Mechanical Plane Shifting in Bending Elastomer Film Revealed by Quantification of Internal Strain

“…Although tensile and compressive stresses of materials vary as the strain increases, [43,44] hard materials like metals and ceramics yield or break before reaching the large strain where the stress difference appears. [45][46][47][48][49] In contrast to such materials, the PDMS film can largely bend by elastic deformation, leading to reversible NMP shifting. To the best of our knowledge, this large NMP shift of %160 μm during elastic bending has been experimentally quantified for the first time.…”