Failure Prediction of Automotive Components Utilizing a Path Independent Forming Limit Criterion

Abstract

An area in the automotive industry that receives a lot of attention today is the introduction of lighter and more advanced material grades in order to reduce carbon emissions, both during production and through reduced fuel consumption. As the complexity of the introduced materials and component geometries increases, so does the need for more complex failure prediction approaches. A proposed path-independent failure criterion, based on a transformation of the limit curve into an alternative evaluation space, is investigated. Initially, the yield criterion used for this transformation of the limit curve was investigated. Here it was determined that the criterion for the transformation could not be decoupled from the material model used for the simulation. Subsequently, the approach using the transformed limit curve was tested on an industrial case from Volvo Cars, but a successful failure prediction was not obtained.

Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability

“…Figure 3 presents the new FLC based on the four Nakajima specimens tested in the transverse direction. For the case of the 125L specimen, this experiment was performed to replicate the strain path investigated by Norz et al [4] and Barlo et al [5], where a radical change in strain direction is seen. For the strain path presented in Figure 3 representing the 125L sample, the change in loading direction results in the minor strain of the post-straining operation being added to the major strain of the pre-straining and the major strain of the post-straining to the minor strain of the pre-straining.…”

“…For the investigated approach, a transformation of the FLC into the alternative evaluation space is needed. The work presented in [5] investigated the same VDA239 CR4 mild steel and how sensitive the transformation was to the choice of material model. It was concluded that the transformation could not be decoupled from the choice of material model used in the simulation, why a transformation based on the BBC2005 material model was needed for this study, and the curve presented in [5] was adopted.…”

“…The work presented in [5] investigated the same VDA239 CR4 mild steel and how sensitive the transformation was to the choice of material model. It was concluded that the transformation could not be decoupled from the choice of material model used in the simulation, why a transformation based on the BBC2005 material model was needed for this study, and the curve presented in [5] was adopted. Combining the curve with the information presented in Table 4, the failure evaluation in the alternative evaluation space displayed in Figure 6 can be created.…”

“…With the recent changes driven by demand, the severity of the path non-linearity also increases. Recently, both Norz et al [4] and Barlo et al [5] tested different numerical approaches to predict failure in an automotive component with a critical element displaying a strain path with a radical change in the loading direction -both not successfully. This paper proposes a new tool geometry for the pre-straining of sheets and sets The tool is designed to provide a pre-straining with a uniform strain distribution in the centre of the sheet in a circular area with a diameter of 200 [mm].…”