Research on the correlation between the medium-weight shock test load and the design shock load for ship equipment

At present, there is a lack of research on the correlation between the shock design load specified in GJB 1060.1—1991 and the shock test load corresponding to the test conditions specified in GJB 150.18—1986 in China. Without a clear understanding of the severities of shock design loads and shock test loads, it is impossible to accurately guide the anti-shock design for the evaluation and testing of ship equipment. Taking the medium-weight shock test specified in GJB 150.18—1986 standard as a case, a multi-degree-of-freedom mass stiffness damping dynamic model is established. Considering the single-degree-of-freedom rigid installation equipment installed on the hull (the equipment itself is assumed to be rigid), the shock test load calculation under the standard conditions can be carried out. It can be found that there are upper and lower limits for the shock spectrum velocity of the test load anvil where the lower limit is about 1.75 m/s and the upper limit is about 2.40 m/s. A calculation formula of the shock test spectrum velocity is fitted. Based on the DDAM (dynamic design analysis method) method and the shock design spectrum value specified in GJB 1060.1—1991, the shock design spectrum velocity calculated is compared with the shock test load, and the influences of equipment installation frequency, equipment mass and pendulum height on the shock design load and shock test load are analyzed. Based on the comparison results, it is found that the shock design load is more severe than the shock test load. However, when the channel steel span is relatively large (greater than 90 cm) and the equipment installation frequency is relatively high (greater than 80 Hz), the shock test load may be more severe. In addition, the quantitative ratio between the velocity of the shock design spectrum and that of the shock test spectrum is provided. The research results prove the correlation between the shock design load and the shock test load, which can provide reference for the shock resistance design and shock test of the equipment and the revision of relevant standards.