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

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Shock Testing

Stuns alongside drive or steady loads are a percentage of the regular situations experienced by all hardware introduced in airplane. The tests portrayed by Section 7 of the DO-160 standard apply stuns or steady loads to the gear under test keeping in mind the end goal to reproduce occasions experienced as a feature of ordinary airplane operations. At the point when connected in the endorsed way, the operational stun tests of Section 7 check that hardware will keep on working inside determined gauges amid occasions, for example, wind blasts, landing or maneuvering. Crash wellbeing tests check that hardware won't exhibit a peril to work force by segregating from its mounting or isolating into shots amid a crisis arrival. These tests can be partitioned into three general sorts:

•             Operational Shock

•             Crash Safety (Impulse)

•             Crash Safety (Sustained)

The particular parameters and kind of test to be connected is resolved by hardware classification. Four classifications are characterized in Section 7 (A, B, D & E). The classification determination for hardware is generally picked by the prime foreman or determining power who has information of a definitive establishment area and airplane type(s) and ought to be expressed in the significant gear particular. The classification picked will fundamentally figure out if the standard or low-recurrence variation of either operational stuns or accident security will apply. Likewise with any stun or increasing speed test, an unbending apparatus reenacting the in-administration establishment and permitting simple connection to the test gear mounting example will help to guarantee a consistent and smooth streaming test succession.

For the Operational Shock test, a terminal crest sawtooth stun heartbeat is connected to the gear under test (EUT) with am plentifulness of 6 g's top and an ostensible span of 11, 20 or 100 mS as per the characterized hardware classification. Hardware is regularly tried in a working or force connected state. In the event that wanting to perform this test on a vibration exciter, there are two contemplations. First and foremost, the obliged speed and removal will increment generously with the more drawn out length of time (low-recurrence) stuns. Besides, the impacts of any connected preand post pay may change the fleeting and ghastly qualities of the reference beat. These impacts are best shown by survey the pseudo speed stun reaction range (SRS) connected with the repaid heartbeat. DO-160 additionally considers applying an identical SRS to supplant the terminal top sawtooth beat. Since these stuns are to be connected to every course of each orthogonal hub, a great delineation of the hub definition for the EUT gave in the test method will help guarantee that the testing streams easily as every pivot is finished.

Crash security (if appropriate) is performed utilizing both the drive and managed systems. For the drive technique, the abundancy for the terminal top sawtooth heartbeat is determined as 20g's top. Likewise with the operational stun system, the ostensible length of time differs as indicated by the hardware class somewhere around 11 and 100 mS. Whether performed on a drop table or shaker, the accessibility of a fake load or mass test system with a comparative focal point of gravity (CG) will help in the setup and execution of these stuns by using this unit to apply stuns amid the setup stage. A fake burden might likewise be substituted for any electro-mechanical segments mounted on or inside of the hardware case the length of it speaks to the same weight and CG to the gath.

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