Dynamic analysis and experiment methods for a generic space station model

Abstract

Modal vibration tests in conjunction with finite-element analysis were used to characterize a generic dynamic model. The model consisted of five substructures to simulate the multibody, low-frequency nature of large space structures. Static tests were used to refine the substructure analytical models prior to full assemblage analysis. The effects of a cable suspension system were analyzed using a prestressed vibration analysis. Coupling between a cable suspension mode and model bending mode was found to be influenced by the distance from the model center of gravity to the cable-to-model attachment location. A damping characterization method using noncontacting exciters was used to measure the amplitude-dependent damping. Frequency and damping measurements in ambient air and at near-vacuum conditions were made. Ambient air decreased vibration frequencies by an average 3.1% and increased the modal damping by an average 28% in the generic model. NomenclatureC/C C = critical damping ratio /! = fundamental frequency, Hz g = acceleration due to gravity / = model rotational inertia ti = suspension cable length £ 2 = distance from model center of gravity to cable-tomodel attachment location m -vibration cycle number M = model mass X Q = initial vibration amplitude X m = vibration amplitude of the rath cycle 0JJ0J = cable rotation and rotational acceleration (Fig. 13) $2962 =m°d el rotation and rotational acceleration (Fig. 13) <j)= circular frequency, 2?r/

Effect of temperature on elastic properties of woven-glass epoxy composites for printed circuit board applications

“…35,36 One solution is to conduct the vibration tests in a low pressure environment as routinely done, for example, in vibration measurements of large space structures. 37,38 The objective of this study is to determine temperature-dependent properties of three commonly pressed boards (1080, 2116, and 7628 woven-glass fabrics and FR4 epoxy). The data will be useful for electronic engineers as they try to design more dimensionally stable, circuit boards.…”