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Journal Article

FEA Development of Spot Weld Modeling with Fracture Forming Limit Diagram(FFLD) Failure Criteria and Its Application to Vehicle Body Structure

2015-04-14
2015-01-1316
Spot weld separation in vehicle development stage is one of the critical phenomena in structural analyses regarding quasi-static test condition, like roof strength or seat/belt pull. It directly reduces structural performance by losing connected load path and occasionally introduces tearing on surrounding sheet metals. Traditionally many efforts have been attempted to capture parent metal ductile fracture, but not applied to spot weld separations in automotive FEA simulations. [1,2,3] This paper introduces how to develop FFLD failure criteria from a series of parametric study on ultra high strength sheet steel and deals with failure criteria around spot weld and parent metal. Once the fracture strains for sheet steels are determined, those developed values were applied to traditional spot weld coupon FEA simulations and tests. Full vehicle level roof strength FEA simulations on a typical automotive body structure were performed and verified to the physical tests.
Technical Paper

Investigation of Fracture Behavior of Deep Drawn Automotive Part affected by Thinning with Shell Finite Elements

2020-04-14
2020-01-0208
In the recent decades, tremendous effort has been made in automotive industry to reduce vehicle mass and development costs for the purpose of improving fuel economy and building safer vehicles that previous generations of vehicles cannot match. An accurate modeling approach of sheet metal fracture behavior under plastic deformation is one of the key parameters affecting optimal vehicle development process. FLD (Forming Limit Diagram) approach, which plays an important role in judging forming severity, has been widely used in forming industry, and localized necking is the dominant mechanism leading to fracture in sheet metal forming and crash events. FLD is limited only to deal with the onset of localized necking and could not predict shear fracture. Therefore, it is essential to develop accurate fracture criteria beyond FLD for vehicle development.
Technical Paper

Evaluation of Force-Based Spot Weld Modeling in Quasi-Static Finite Element Analysis

2012-04-16
2012-01-0537
Evaluating spot weld separation is one of the most challenging tasks in a quasi-static simulation. There are several factors that exist in modeling welds analytically that can influence correlation to physical test. This paper presents 4 specific factors: spot weld representation, weld thickness, weld strength, and metal forming effects around spot welds. There are many ways in which a spot weld can be modeled within an FEA model from mesh independent beams to mesh dependent hex clusters. While each modeling technique comes with its unique sets of advantages and disadvantages, a method is chosen to best balance correlation, model setup timing and computation time. Dependent on the way the thickness of the spot weld is represented, artificial moments can be induced which misrepresents structural behavior. The assigned yield strength of the spot weld influences the behavior of the joint.
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