EXPLAINING SRS – PART 3 Higher Level SRS Shock Tests
Higher Level SRS Shock Tests
As noted in our earlier article EXPLAINING SRS – PART 2, manufacturers and end customers are increasingly turning away from using empirical, testing-machine-specific standards to specify the mechanical shock survivability requirements of their products and equipment. Instead they are requiring products to survive test shocks specified in the SRS domain. As mentioned in our article EXPLAINING SRS PART 1 , SRS plots of a shock provide at each frequency along the plot, the maximum acceleration of a system subjected to the shock if it was a linear system with the natural frequency of the particular point along the plot.
In the particular case of mechanical shock resistance requirements for products and components in the shipbuilding and shipboard equipment industries, end customers are increasingly requiring suppliers’ products to be tested to shock requirements specified in terms of SRS based on specifications such as BV043 or actual real-world data, rather than using the archaic, empirical and imprecise MIL-S-901D standard.
The problem is how to generate the required shocks specified in the SRS domain. For smaller shocks, testing can be performed on a vibrator. Austest has the largest commercial electrodynamic vibrator in use in Australia and thus is best equipped to conduct such testing. Unfortunately, even the largest vibrators cannot produce higher level shocks and in particular cannot come close to generating the SRS test profiles that are being specified to supersede the MIL-S-901D test for the survivability of shipboard equipment subjected to the effects of undersea explosions.
Austest engineers have now solved the problem by developing a customized SRS testing equipment. The machine can generate the shock pulse type required to produce the SRS typically required for shock tests of naval shipboard equipment as well as other products required to survive very high intensity shocks: that is a shock pulse consisting of a half-sine pulse followed immediately by a longer, lower peak absolute acceleration, negative half-sine pulse (such as one stipulated by BV043 standard). We have successfully used the machine for tests where the Customer required shocks with an SRS profile that had pseudo velocities and a total velocity change in excess of those required by typical MIL-S-901D-superseding, SRS test profiles.
Note that both the concept and the design of Austest’s SRS apparatus were entirely developed in house. Furthermore, our engineers have written a customized software streamlining complex calculations required to generate relevant machine parameters for particular SRS profiles and product masses.
Austest’s current SRS machine is capable of testing items with a total (product plus fixture) payload of up to 600kg. However, should customers require it, the concept of the existing apparatus can be scaled up to cater for even heavier items/products.
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