Advancements in Structural Dynamic Qualification Methods.

Kurzfassung

The increase of dimensions and recent advances in lightweight design of space systems have led to the requirement of new structural dynamic qualification techniques. Dynamic qualification means experimental simulation of the structural dynamic environment in order to check the dynamic behaviour of spacecraft. The paper reviews the standard (single axis testing) and advanced test methods (multi axis testing). Two principly different multi-axis test methods are described. First, the possibilities of transient load simulation by means of multi-axis hydraulic shaker facilities are discussed. Particularly the assessment of the reproduction quality of the base acceleration is emphasized. A suitable transient comparison measure is proposed. Second, a shaker test method called Modal Force Combination technique is described which replaces the base acceleration by having a set of forces acting directly in a selected number of structural points. The forces simulate the d'Alembert's inertia forces, which arise due to the transient multi-axial base acceleration. Test results are presented. Finally, the different test methods of structural dynamic qualification are compared, advantages as well as inadequacies of each procedure are pointed out. The topics of further investigation are discussed.