NIST has worked with industry, government, professional societies and others to help develop an international standard for characterising mechanical vibration and shock and its effect on systems and components.
The new standard establishes how systems from computer components to airframes and armoured vehicles respond to specific kinds of shocks.
The new standard published by the International Organisation for Standardisation (ISO) should be especially useful in environmental testing of products and components in high-technology industries such as computer and aerospace manufacturers.
The “shock response spectrum” (SRS) was developed originally as a method to describe the shock-like motions associated with earthquakes, explosions, impacts and other sources of mechanical shocks.
An SRS shows graphically the relative strength of a shock pulse across a range of frequencies. For a mechanical system, such as an airframe, it can indicate how the system responds to a well-defined shock pulse.
SRSs are used to describe the severity of mechanical shocks and the ability of mechanical or electronic systems to tolerate them. They are widely used to test airframes and aerospace instrumentation systems, military vehicles and instrumentation systems used in them, mechanical isolation provided by shipping containers, the durability of hard drives, and to characterise explosive shock events.
In the past, shock tests used a variety of analogue and digital algorithms to synthesise SRS, which often produced significantly varying results.
The new standard is based on standardised, well-defined digital technique. It is said to be a first step towards ensuring that the results of tests using an SRS can be compared reliably when performed at different laboratories.
ISO 18431-4:2007 “Mechanical vibration and shock—Signal processing—Part 4: Shock-response spectrum analysis” from the Acoustical Society of America, which sponsors the standards secretariat of the ISO Technical Committee responsible for this work, at http://asastore.aip.org/.