In order to improve fuel economy and safety of vehicles, many advanced materials such as aluminum alloys and advanced high strength steels have been introduced in automobile body construction in recent years. A key to the adoption of such materials is their manufacturability, such as forming and welding. Resistance welding, as the major enabling technique, has been widely applied in joining these materials. Although there has been a large amount of research in characterizing static and fatigue strengths of Al or AHSS welds, their impact performance is largely unknown, even though it is extremely important for safety. In this paper, the impact strength of AHSS spot welded specimens is analyzed, as a function of welding process parameters and weldment geometry. Both energy and peak load during impacting, as well as failure mode were recorded. The geometric attributes of spot welds, such as indentation width, nugget width, indentation depth, etc. were measured before the specimens were destructively tested. Then these quantities were linked to the impact strength of the welds. Besides several advanced high strength steels, high strength, low alloy (HSLA) steels were also tested in the study for comparison. Models were developed to correlate impact strength with individual factors, both welding parameters and spot weld geometry variables. The effects of interactions between the factors were also investigated. The results showed that these parameters should be examined together in determining a weld’s impact performance.
Microstructure based modeling of deformation and failure of spot-welded advanced high strength steels sheets
