Experimental and Numerical Investigation of the Gurson–Tveergard–Needleman Model Parameters for AISI 1045 Steel

Abstract

Void nucleation, void growth, and void coalescence are the stages of ductile fracture. [1] Initial voids present in nondeformed material as a result of previous manufacturing processes like forging, rolling. [2] The initial voids are able to grow in size. Also, new voids are initiated during plastic deformation. All the initial and the initiated voids grow and then coalescence of voids occurs. [3] Second-phase particles, such as inclusions, can also serve as sources of new voids. [4] Ultimately, ductile fracture occurs through the coalescence of voids. [5] Gurson proposes a model for void-related damage in porous domains. [6] Tveergard and Needleman also contribute to the original porous metal plasticity theory. [7,8] Their Gurson-Tveergard-Needleman (GTN) damage model has been widely used to predict ductile deformation and metal fracture. On the other hand, even if widely used to predict ductile deformation characteristics of materials, the GTN model is less effective in predicting damage behavior under low-stress triaxiality, instead under high-stress triaxiality. [9] Also, some studies exist related to low-stress triaxiality for the GTN model. [10,11] The GTN model is preferred for achieving precise modeling of metallic materials that are investigated for their deformation behavior due to their widespread use around the globe. In the literature, researchers have focused on the GTN model in three aspects: parameter identification, model modification, and model usage in applications.Researchers attempt to obtain the parameters using various methodologies such as trial and error, numerical analysis, and advanced experimental techniques. Kahziz et al. examine and identify the steps of void development by in situ X-ray laminography of CT specimens. [12] Another study identifies GTN parameters by artificial neural network and tensile test results. [13] Petit et al. characterize the deformation behavior of 6061 aluminum foam and then validate their results with GTN-based finite element method (FEM) models. [14] Cao et al. study to characterize the ductile damage mechanism of high carbon steel by utilizing X-ray microtomography and mechanical tests. [15] According to the study, void nucleation and void size increase exponentially related to effective plastic strain. Kossakowski studied the GTN model for S235JR steel for spatial stress states. [16] The study by Yuenyong et al. finds void volume fractions with a method called direct potential drop which is performed by correlating void density with the change in the electrical resistance of examined area. [17] Wcislik examines final void volume fractions of fracture surfaces of structural steel with scanning electron microscopy (SEM) images and image processing. [18] Xu et al. develop GTN and Thomson models based on the damage model which consists of size and geometry effects for void development. [19] Ouladbraim et al. utilized GTN model-based tensile test simulations to obtain to necessary data for artificial neural networks. [20]