Modelling and predicting spotweld failures in automotive crash structures

The project has developed spotweld failure models capable of industry application for a range of steel grades to support development of automotive products, and their compliance to international crash safety requirements. An important consideration in this project is a requirement to balance the cost to develop the data input to models and their application capability in CAE based crash simulation tools to predict spotweld failures. Shear and tension spotwelded joint specimens in a variety of automotive sheet steel materials with thickness varying in the range 0.8 to 2 mm have been tested at low and high speed. The joint specimens have been spotwelded under controlled laboratory conditions and simulated factory assembly conditions to compare performance, and validate spotweld models for industry application. All specimens have been subjected to a heat treatment that simulates the paint bake conditioning applied to the BIW. All spotwelded specimens are tested under controlled laboratory conditions. At low rate, spotwelds are tested at 1 mm/s and these may be referred to as quasi-static tests. At high rate, spotwelds are tested at 2 m/s and these may be referred to as dynamic tests. Accordingly test procedures were developed and refined to support the development of quasi-static and dynamic test results. In total some two hundred tests were performed. A method to characterise the test results, and calibrate models to predict spotweld failure under quasi- static and dynamic-impact conditions is described.