Numerically Simulated and Experimental Results for a Deterministic Excitation with External Loads

Abstract

The ultimate goal of a laboratory simulation is to ensure that a given test item will survive when exposed to its field dynamic environment. Two previous papers [1,2] described the process of using field vibration data to define suitable test item inputs in laboratory simulations. The structural interactions that occur when the test item is attached to the vehicle in the field or to the vibration exciters in the laboratory were discussed in Ref. [1]. Numerical examples describing different test scenarios used in laboratory simulations were presented in Ref. [2]. In these test scenarios, the test item was subjected to interface forces only, i.e.; no external forces were applied to the test item while in the field environment. The first part of the present paper discusses laboratory simulations of field data when the test item is subjected to external forces in addition to interface forces in the field environment. Numerical examples of different laboratory test scenarios show that accounting for field external forces in the laboratory is of major importance. The second part of the paper deals with the force identification problem. The pseudo-inverse technique, commonly employed in modal testing is used to predict the test item input forces from field motions. Numerical examples show the feasibility of the pseudo-inverse method in predicting external loads. An experimental analysis is performed on a free beam to discuss the practical implications of this force identification technique when applied to realistic situations. This paper deals only with transient and periodic forces and motions.