Study and Validation of Constitutive Models for AHSS Steels

• Autor(a) principal: Figueira, José Tomé Serra Afonso
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/66169
• topic: Advanced High Strength Steels (AHSS); Dual-Phase steels (DP); Springback prediction; Constitutive material models; Loading paths; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Mecânica

Advanced High Strength Steels have been extensively used in automotive industry due to their high yield and ultimate tensile strengths, allowing the production of lighter structural components for the car body structure without compromising safety requirements, however these steels exhibit a large springback phenomenon, after forming processes. To deal with this challenge, constitutive material models have been studied to capture the material behaviour under plastic deformation, and accurately predict the springback. Making use of the material characterization tests previously performed, the aim of this dissertation is to study and validate constitutive material models for Dual-Phase steels, DP1000, and DP1200. For that, FEM simulations with LS-DYNA software were performed to study which material models better describe the material behaviour under different loading paths and in springback prediction. The Nakajima and notch tensile tests simulations were performed using explicit time integration to study the different loading paths, while for the U-shaped bend tests the simulation procedure was separated into two distinct simulations. A forming simulation with explicit time integration and a springback simulation with implicit time integration to validate constitutive models in its application for springback prediction. The results of the simulations were compared with the data obtained from experimental testing. Regarding the loading path behaviour, the results indicate that most of the material models followed accurately the elementary loading paths, such as biaxial tension and uniaxial tension. As for the U-shaped bend test for the setup with the higher punch and die radiuses, the Yoshida-Uemori material model considering transverse anisotropy performed well in springback prediction.