NIST And Industry Produce Improved Shock Tests

NIST, as convener of the ISO working group that coordinated development of the standard, played an essential role in keeping United States industries informed of developments and encouraging U.S. industry participation in the international technical discussions to formulate the new standard.

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 both 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 characterize explosive shock events.

In the past, shock tests used a variety of analog and digital algorithms to synthesize SRS, which often produced significantly varying results. The new standard is based on standardized, well-defined digital techniques. It is a first step towards ensuring that the results of tests using an SRS can be compared reliably when performed at different laboratories.

Reference: 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/.