A New Method to Synthesize a Shock Response Spectrum Compatible Base Acceleration to Improve Multi-Degree of Freedom System Response

University of Minnesota Ph.D. dissertation. 2015. Major: Mechanical Engineering. Advisor: Susan Mantell. 1 computer file (PDF); x, 98 pages.A new method has been developed to synthesize a shock response spectrum (SRS) compatible base acceleration with additional parameters in the synthesis process beyond current practices. Current base acceleration synthesis methods address only SRS compatibility. However, additional information is available to synthesize a base acceleration to improve multi-degree of freedom (MDOF) system response accuracy. Expanding the synthesis procedure to include energy input and temporal information provides more constraints on the development of the synthesized acceleration. Similar to the SRS, an energy input spectrum (EIS) is a frequency based relationship for the peak energy input per unit mass to a series of single-degree of freedom (SDOF) oscillators from a base acceleration. The EIS represents total input energy contributions (kinetic, damped and absorbed energy). Temporal information includes overall shape of the transient shock pulse envelope E(t) (rise, plateau, decay) and a TE duration where strong shock occurs. When EIS, E(t) and TE compatibility are added to the synthesis procedure, an improved base acceleration results. To quantify the significance of these quantities, a regression analysis was performed based on linear and nonlinear 3DOF model responses. The regression analysis confirmed that compatibility with SRS, EIS and TE were significant factors for accurate MDOF model response. To test this finding, a base acceleration was synthesized with the expanded procedure. Four other accelerations were synthesized with current state of the art methods which match the SRS only. The five synthesized accelerations were applied to a 3DOF model based on a US naval medium weight shock machine (MWSM). MWSM model results confirmed that the SRS, EIS, TE compatible acceleration resulted in improved accuracy of peak mass accelerations and displacements in the majority of the cases, and consistently gave more accurate peak energy input to the MWSM model. Energy input to a structure is a significant factor for damage potential. The total kinetic, damped and absorbed energy input represents a system damage potential which the structure as a whole must dissipate