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Transient dynamic analysis of vehicles riding pavements has became a reliable and important tool - whenever well carried out, in the durability and fatigue life evaluation of mechanical sub-components. Since a given vehicle or accessory is designed to operate on distinct types of terrain/roads, a detailed knowledge of these excitations is necessary for a realistic characterization of its effects over the structural parts. The most common form to obtain terrain profile is throughout profilometers installed on special vehicles. The amplitude vs. time signature of any terrain could then be used directly as the excitation applied to dynamic models, but this would restrict the analysis only to those terrains already measured and catalogued. The objective of the present work is to revist the generation of power spectrum density (PSD) functions aiming their usage as excitation on numerical dynamic models of vehicles.

Applying knowledge available at technical literature for cycle counting, damage caused by each load cycle through S-N curve, and fatigue damage accumulation by Palmgren-Miner rule, durability prediction is performed for a leafspring of a commercial vehicle with 6×4 suspension system. Max principal tension is measured by means of strain gages in the most representative points for fatigue life of the leafspring, determined with FEA, while vehicle runs over off-road track in a proving ground. Load and tension are also measured in a laboratory bench test for this component. Correlation between off-road track and bench test is then performed. Finally, representative samples of the component are tested with dynamic loading until fatigue fracture in bench test, and using data from these tests, statistical analysis is performed with application of Weibull distribution, allowing life prediction in statistical terms.