TY - BOOK

T1 - Multi-physical modelling of resistance spot welding with assessing the risk of liquid metal embrittlement

AU - Prabitz, Konstantin

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - Lightweight materials gain increasing importance in the automotive industry due to their potential to reduce fuel consumption that subsequently helps mitigating the environmental impact as well as costs. From the point of view of crashworthiness advanced high strength steels with high ductility are promising metals. For newly developed steels an important aspect to be taken into account is the processing of the material. Joining steel sheets is often accomplished by resistance spot welding, i.e., an easy to automate, quick and reliable joining process that is in high demand in the automotive industry. For corrosion protection of the car's body, the steel sheets are coated with a thin zinc layer. Under very specific conditions that may occur during welding, the presence of zinc may induce the risk of liquid metal embrittlement. The main macroscopic influences on this effect are temperature, plastic strain and material pairing. Liquid metal embrittlement leads to a weakening of the weld strength or even to catastrophic failure. In this work extensive material tests are carried out to investigate the embrittlement behaviour. Based on these experiments a set of damage-relevant material properties is determined. With this knowledge a multi-physical coupled and validated finite element model of the resistance spot welding process is developed which is capable of capturing the conditions during welding. This work deals with characterising liquid metal embrittlement and creating a predictive and experimental based risk indicator, which is then implemented in the spot welding model. With these tools the process is modified and low risk welding schedules are proposed.

AB - Lightweight materials gain increasing importance in the automotive industry due to their potential to reduce fuel consumption that subsequently helps mitigating the environmental impact as well as costs. From the point of view of crashworthiness advanced high strength steels with high ductility are promising metals. For newly developed steels an important aspect to be taken into account is the processing of the material. Joining steel sheets is often accomplished by resistance spot welding, i.e., an easy to automate, quick and reliable joining process that is in high demand in the automotive industry. For corrosion protection of the car's body, the steel sheets are coated with a thin zinc layer. Under very specific conditions that may occur during welding, the presence of zinc may induce the risk of liquid metal embrittlement. The main macroscopic influences on this effect are temperature, plastic strain and material pairing. Liquid metal embrittlement leads to a weakening of the weld strength or even to catastrophic failure. In this work extensive material tests are carried out to investigate the embrittlement behaviour. Based on these experiments a set of damage-relevant material properties is determined. With this knowledge a multi-physical coupled and validated finite element model of the resistance spot welding process is developed which is capable of capturing the conditions during welding. This work deals with characterising liquid metal embrittlement and creating a predictive and experimental based risk indicator, which is then implemented in the spot welding model. With these tools the process is modified and low risk welding schedules are proposed.

KW - Resistance spot welding

KW - Liquid metal embrittlement

KW - Advanced high strength steel

KW - Finite element model

KW - Risk indicator

KW - Widerstandspunktschweißen

KW - Flüssigmetallversprödung

KW - Hochfeste Stähle

KW - Finite Elemente Modell

KW - Risikoindikator

M3 - Doctoral Thesis

ER -