Progress in fatigue assessment of welded hollow-section aluminium structures

摘要

Recent developments in light-weight automotive structures have included the use of aluminium alloys, particularly extruded sections. The fatigue strenght properties of the resulting welded structures are not completely understood and consequently explicit design procedures not yet available. Therefore, generally applicable fatigue design methods for welded aluminium joints are reveiewed, as are the various approaches to fatigue life estimation currently adopted in design codes across a wide range of industrial applications. The applicability of these established methodologies to the fatigue design of automotive space frame structures is critically assessed. Of the many approaches available, the hot spot stress method is identified as the most promising in terms of providing a coherent and comprehensive approach to design, embracing the many uncertainties present in the design input parameters associated with weldments. Particular problems related to implementation are considered such as failure sites and determination of appropriate stress concentration factors from physical models, finite element calucations or parametric equations. Some preliminary numerical stress analysis (finite element) and experimental fatigue test results are also presented for a T-joint configuration. Recommendations are made for a design methodology for welded rectangular hollow-section joints in aluminium space frames, including a selection of hot spot S-N curves.