Acceleration Testing

Acceleration testing is performed to assure that equipment can structurally withstand the steady state inertia loads that are induced by acceleration, deceleration, and similar maneuvers in vehicles, aircraft, and other service environments. Acceleration tests are also used to assure that equipment (or parts thereof) does not become a hazardous flying projectile during or after exposure to crash inertia loads. The acceleration test is applicable to equipment that is installed in aircraft, helicopters, manned aerospace vehicles, air-carried stores, and ground/sea-launched missiles. Equipment must usually function without degradation during and following exposure to these forces. When performing the acceleration test, the application of steady state inertial loading is most easily accomplished using a centrifuge with a rotating swing arm. Any necessary connections to the equipment under test (electrical or fluid/gas) is usually accomplished through a slip ring mounted in the centrifuge. Constant acceleration results in loads on mounting hardware and internal loads within equipment. Note that all elements of the equipment are loaded, including any internal fluids. Some of the detrimental effects that may occur due to acceleration are:

Structural deflections that may interfere with required operation. Permanent deformation, structural cracks, and fractures that disable or destroy materiel. Broken fasteners and supports that result in loose parts within equipment. Broken mounting hardware that results in loose parts or subassemblies. Electronic circuit boards that short out and circuits that open up. Inductors and capacitors that change value. Relays that open or close unexpectedly. Actuators and other mechanisms that bind. Seals that leak. Pressure and flow regulators that change value. Pumps that cavitate. Spools in servo valves that are displaced causing erratic and dangerous control system response Some of the widely recognized test standards defining acceleration tests are: MIL-STD-202 Method 212 MIL-STD-810 Method 513 RTCA DO-160 Section 7 (Crash Safety Sustained) When an acceleration test is required, some of the information that will be helpful to establish prior to testing include: A complete axis definition for the equipment to be tested. Mounting fixture designed to adapt the equipment service mount to that of the test equipment (centrifuge). The definition of the vector orientation of the test item with respect to the fixture. The definition of the vector orientation of the mounting fixture with respect to direction of acceleration. The definition of center of gravity of the test item. The major specifications and capabilities of Qualtest’s centrifuge are as follows: Arm radius: 29 inches. Maximum payload size: 15 inches x 15 inches x 15 inches (15 in3). Maximum RPM: Typically 400 RPM. Maximum power through slip rings: 50 Volts (Low Amperage). Number of slip ring contacts: 30 For more details :  http://qualtest.com/html/acceleration.htm