Introduction to shock-response spectra

A shock is a sudden and violent event. There are many examples of shocks, from earth quakes and explosions to controlled mechanical transient processes. In this report, we discuss theory, modeling and analysis methods of shock response which is how objects respond to shocks. The topic shock response is applicable to buildings, vehicles and ships and a variety of objects that can be exposed to transient forces. It is also applicable to equipment attached to these objects.

Engineers have been working with shocks and transient processes for many years, in particular within the international defence and space sector where the topic is mature and well understood. For example, equipment must be tested and qualified for certain shocks and vibrations before it is installed in a space vehicle and launched into space. The equipment must withstand tests defined according to a certain shock response spectrum. The same applies for equipment used in military vehicles.

We experience that knowledge about shock response and shock response spectra in particular the theoretical side of it, is not so well established among Norwegian defence experts, which is the reason for writing this report. The capability to perform shock simulation and testing, shock analysis and interpretation is essential for and requested by the Armed Forces. Equipment in naval ships and vehicles must withstand certain defined impacts that should be verified and tested before the equipment is purchased and installed.

The main focus of this report is to present and explain the shock response spectrum, why it is useful, how to calculate it and some examples of its use. We also explain how shock response spectrum can be used as design criteria and how they are used in the characterization of shocks. Finally, the “shock spectrum dip” is discussed.