Impacts of Test Fixture Connections of the BARC Structure on Its Dynamical Responses

Abstract

The Box Assembly with Removable Component (BARC) structure has been recently introduced as a challenge problem for the study of the effects of boundary conditions on vibrational testing and modal analysis. Current efforts in studying shaker input excitations on the BARC structure have focused on either varying the degrees of freedom of the test or varying the input signal. The effects that the bolted joints introduced into the BARC's dynamical response have not been fully investigated. This study presents an investigation on the influences of test fixture connections on the dynamical responses of BARC systems for the purpose of establishing a standard fixture connection for general testing and test replication. This investigation is done by varying the distance between bolted connections to compare the effects of stiffness of fixture contribution on the dynamic response. In addition to modal analysis, experimental random vibrations are carried out to determine the dominant frequencies in the system. The experimental measurements are compared to finite element simulations in order to determine the possible variability and the reason behind that. The finite element simulations show that the wider connection geometry leads to a softening effect in natural frequencies of the system. On the other hand, the experimental measurements indicate that the effects of gap between the fixture connections have a negligible impact on the system's dominant frequencies. This study shows the importance of accurately considering the same experimental setup as the computational modeling and vice versa.