Identification of the bulk behavior of coatings by nano-indentation test and FE-analysis and its application to forming analysis of the coated steel sheet

In this study, nano-indentation tests, FE simulation and artificial neural network (ANN) technique were used to characterize the power law of the elasto-plastic stress–strain behavior of the coating layers of coated sheets. In addition, based on Oudinʹs work, two types of FE model were applied on the behavior of the coatings in FE simulations; one was a single-behavior model, which had only one stress–strain behavior and the other was a layer-behavior model, which consisted of separate coating layers and substrates. FE simulations of the cup drawing process were carried out for the two FE models, respectively. The results show that the layer-behavior model that considered the behavior of the coatings was most accurate at predicting of drawing loads.