Minimising variability in steel / weld fatigue data and developing robust durability design for automotive chassis applications.

Engineers often make use of component safety factors in order to ensure reliability and robustness of new products. To truly define a suitable safety factor for a given component, an understanding of the variability in the structural performance of the component is required, in addition to the variability in conditions of use. A large variation in either of these two factors can give rise to an overlap between the structural capability of a component and the limits of its service conditions. This may result in a situation where the component's structural capability fall below the in-service requirements, which could lead to catastrophic failure. Accurately defining the variability in the mechanical behaviour of High Strength Low Alloy (HSLA) steels used for automotive chassis & suspension applications can help design engineers decide on appropriate safety factors to avoid over-engineering products. By investigating the root-causes of this variability, the steel industry can also benefit from this research, as its findings can assist in reducing the variability of its steel products that arise during production. Variability in steel mechanical behaviour can be due to numerous factors including chemistries, processing temperatures, cooling patterns, and the strip thickness etc. By analysing the variability that exists in the mechanical properties, fatigue behaviour and thickness of strip steel, a prediction of the overall effect of variations within these parameters on manufactured components is possible. Understanding the relationship between material variability and the consistency of component structural capability is paramount for achieving robust and reliable designs. The current research attempts to uncover and present some of these relationships