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Modeling of the fracture behavior of spot welds using advanced micro-mechanical damage models

: Sommer, S.

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IOP conference series. Materials science and engineering 10 (2010), No.1, Art.012057
ISSN: 1757-8981
ISSN: 1757-899X
World Congress on Computational Mechanics (WCCM) <9, 2010, Sydney>
Asian Pacific Congress on Computational Mechanics (APCOM) <4, 2010, Sydney>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer IWM ()

This paper presents the modeling of deformation and fracture behavior of resistance spot welded joints in DP600 steel sheets. Spot welding is still the most commonly used joining technique in automotive engineering. In overloading situations like crash joints are often the weakest link in a structure. For those reasons, crash simulations need reliable and applicable tools to predict the load bearing capacity of spot welded components. Two series of component tests with different spot weld diameters have shown that the diameter of the weld nugget is the main influencing factor affecting fracture mode (interfacial or pull-out fracture), load bearing capacity and energy absorption. In order to find a correlation between nugget diameter, load bearing capacity and fracture mode, the spot welds are simulated with detailed finite element models containing base metal, heat affected zone and weld metal in lap-shear loading conditions. The change in fracture mode from interfacial to pull-out or peel-out fracture with growing nugget diameter under lap-shear loading was successfully modeled using the Gologanu-Leblond model in combination with the fracture criteria of Thomason and Embury. A small nugget diameter is identified to be the main cause for interfacial fracture. In good agreement with experimental observations, the calculated pull-out fracture initiates in the base metal at the boundary to the heat affected zone.