MIL-STD-1660A APPENDIX A
A.1 SCOPE
VIBRATION (REPETITIVE SHOCK) TEST
A.1.1 Scope. This procedure is intended to indicate whether or not a unit load is adequate to prevent damage to either the packaging or the contents when the unit load is tested unattached on the platform of a vibration testing machine at frequencies below 5 hertz. Either the unit load bounces on the platform and receives repetitive shock and vibration of an indiscrete and variable nature; or the unit load does not leave the platform. Shocks applied to the unit load excite each component at its own natural frequency, but when the unit load does not leave the platform only those components that vibrate in resonance with the platform vibration are excited. This procedure is useful to predict whether or not such vibrations in transportation are likely to cause damage to the packaging or contents when the shipment is not securely tied down to the floor of the vehicle. Supplementary functional tests of the package contents may be necessary to evaluate functional damage. The procedure is not intended for the development of design parameters for shock and vibration isolation systems. This Appendix is a mandatory part of the standard.
The information contained herein is intended for compliance. A.2 DEFINITIONS
A.2.1 Shock. A blow, impact, collision, jar, or similar instantaneous application of energy or force. (A shock will cause some vibration in an item or package.)
A.2.2 Vibration. The continuous oscillation of an element or body relative to a suitable reference point. A.3 APPARATUS
A.3.1 Platform. A platform of suitable size and weight-carrying capacity supported on a mechanism that will maintain the surface essentially horizontal as it vibrates the platform so that the vertical component of the motion is approximately sinusoidal. (A rotary motion of the platform is acceptable.) The amplitude of the vibration shall be
½ inch (1-inch double amplitude). The frequency shall be variable within the approximate range from 3 to 5 hertz
and shall be controlled to produce the platform vibration specified in A.6.
A.3.2 Restraining devices. Fences, barricades, or blocking that can be attached to the platform to keep the specimen in position on the platform without unnecessarily restricting the vertical or rotational movements of the specimen.
A.4 SPECIMENS
A.4.1 Contents. One unit load and its contents shall constitute a single specimen. The unit load shall be loaded for the test with the interior packing and the actual contents for which it was designed. If use of the actual contents
is not practical, a dummy load shall be substituted to simulate such contents in weight, weight distribution, rigidity, shape, and position in the container. The contents, or dummy load, shall be blocked, braced, and cushioned in place
as for shipment.
A.4.1.1 Specimen condition. If the intended contents, or a fully representative dummy load such as a reject item are to be used in the package, their condition, before and after test, must be determined by appropriate methods to establish the extent of damage suffered in the test.
A.4.1.2 Dummy load. If a dummy load is to be used, unless it is fully representative of the intended contents, the ability of the package to prevent damage can be determined only by indirect methods such as comparison of accelerations measured on the dummy load and fragility factors for the intended contents.
Source: https://assist.dla.mil -- 1D9ownloaded: 2014-09-28T13:04Z Check the source to verify that this is the current version before use.
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