Downloaded from https://www.everyspec.com MIL-STO-81OC 10 March 1975 METHOD 516.2 SHOCK 1. PURPOSE. The shock test is performed to determine if equipment is constructed to withstand expected dynsmic shock stresses and that perform- ance degradations or malfunctions will not be produced by the service shock environment expected in handling, transportation,and service use. 2. APPARATUS 2.1 Shock machine. The.shock machine utilized for procedures I, III, and IV shall be capable of producing the specified input shock pulse shown on figure 516.2-1 or 516.2-2. The shock machine may be of the free fall, resilient rebound, nonresilient, hydraulic, compressed gas or other activa- ting types.
Apparatus for other procedures are included in the individual procedure. 2.1.1 Shock machine calibration. The actual test item, a rejected item, or a rigid dummy mass shall be used to calibrate the shock machine for conformance with the specified wave shape. When a rigid dummy mass is used, it shall have the same center of.gravity and the swe mass as that intended for the test item and shall be installed in a manner similar to that of the test item.
(When a rigid dummy mass or rejected item is used for calibra- tion, the waveform during the actual test may be somewhat different from that observed during calibration.) The shock machine shall then be cali- brated for conformancewith the specified waveform. Two consecutive shock applications to the calibration’load shall produce waveforms which are all within the tolerance envelope given on figures 516.2-1 and 516.2-2. The calibrating load shall ~hen be removed and the shock test performed on the actual test item.
Provided all conditions remain the same, other than the substitution of the test item for the calibrating load, the waveform shall be considered to meet the specified test requirement. The actual test waveform shall be recorded for later use should a failure analysis be required. 2.2 Instrumentation. The instrumentationused to measure the input shock pulse, in order to meet the tolerance requirements of the test procedure, shall have the characteristicsspecified in the following paragraphs: 2.2.1 Frequency response. The frequency response of the complete measur- ing system, from the accelerometer through the readout instrument, shall be as shown on figure 516.2-3.
Particular care shall be exercised in the selection of each individual instrument of the shock measuring instrumen- tation system in order to assure compatibilitywith the prescribed fre- quency response tolerance. 516.2-1 METHOD 516.2 10 March 1975