32. Issues in Laboratory Simulation of Field Vibration Data: Experimental Results on a Typical Structure

Laboratory tests are required in order to qualify a given test item before it is exposed to its field vibration environment, a process that is frequently referred to as vibration or environmental testing. In a typical laboratory environment, a given test article is mounted on the vibration exciter through a test fixture thus forming a combined structure. The combined system is then driven according to prescribed testing conditions while the test item dynamic response is continuously monitored such that maximum dynamic strain are confined under safe and desired levels. The process of going from the field to the laboratory involves some key steps, that include but are not limited to: (1) knowledge of the dynamic characteristics of the systems involved; (2) design of test fixture in order to properly attach the test item to the vibration exciter table; (3) definition of suitable laboratory inputs that when applied to the test article are capable of predicting or at least simulate its field response. The article aims to discuss some of these important issues, particularly the important role of modal testing principles in obtaining accurate response models for the structures involved. Reasonably accurate and experimentally verified models certainly allow that further questions be addressed in the processing of simulating field vibration data.