Enveloping the Shock Response Spectrum (SRS) Does Not Always Produce a Conservative Test

When the shock response spectrum (SRS) of a test envelops the SRS of the environment at all frequencies for a given mechanical system, typically the assumption is that a conservative test will result; that is, the peak response observed in the environment will be less than the peak response observed in the test. Other suggested measures characterizing a shock include the Fourier energy spectrum (with the assumption that the energy is larger in the test than in the environment), input duration (if the duration of the test is shorter than the duration of the environment), and peak velocity or pseudo velocity (if the peak velocity is greater in the test than in the environment). If these assumptions are met the test will be conservative. This paper shows that a test that complies with all of the suggested measures mentioned above could still produce a response that is smaller than the response from a hypothetical baseline environment.