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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Mechanical Shock Testing

The Qualtest EMI Test Facility has expanded from 4,100 to 8,400 square feet! Two shielded EMI Test Enclosures were also added along with more equipment and test personnel to support the increased demand for this important area of testing. In addition, test capability was expanded to include DOD-STD-1399 Section 070, which uses a Helmholtz coil to generate a DC Magnetic Field of 1600 A/m. Our Helmholtz coil has a test area of 50 cm3 but larger test items can be accommodated by using multiple position exposures. 

Shocks along with impulse or constant loads are some of the common environments experienced by all equipment installed in aircraft. The tests described by Section 7 of the DO-160 standard apply shocks or constant loads to the equipment under test in order to simulate events encountered as part of normal aircraft operations. When applied in the prescribed manner, the operational shock tests of Section 7 verify that equipment will continue to function within specified standards during events such as wind gusts, landing or taxiing. Crash safety tests verify that equipment will not present a hazard to personnel by detaching from its mounting or separating into projectiles during an emergency landing. These tests can be divided into three general types:

• Operational Shock
• Crash Safety (Impulse)
• Crash Safety (Sustained)

The specific parameters and type of test to be applied is determined according to the equipment category. Four categories are defined in Section 7 (A, B, D & E). The category selection for equipment is usually chosen by the prime contractor or specifying authority who has knowledge of the ultimate installation location and aircraft type(s) and should be stated in the relevant equipment specification.  The category chosen will basically determine whether the standard or low-frequency variant of either operational shocks or crash safety will apply. As with any shock or acceleration test, a rigid fixture simulating the in-service installation and allowing easy attachment to the test equipment mounting pattern will help to insure a compliant and smooth flowing test sequence.

For the Operational Shock test, a terminal peak sawtooth shock pulse is applied to the equipment under test (EUT) with am amplitude of 6 g’s peak and a nominal duration of 11, 20 or 100 mS according to the defined equipment category. Equipment is normally tested in an operating or power-applied state. If planning to perform this test on a vibration exciter, there are two considerations. First, the required velocity and displacement will increase substantially with the longer duration (low-frequency) shocks. Secondly, the effects of any applied pre and post compensation may alter the temporal and spectral characteristics of the reference pulse. These effects are best illustrated by viewing the pseudo velocity shock response spectrum (SRS) associated with the compensated pulse. DO-160 also allows for applying an equivalent SRS to replace the terminal peak sawtooth pulse. Since these shocks are to be applied to each direction of each orthogonal axis, a good illustration of the axis definition for the EUT provided in the test procedure will help insure that the testing flows smoothly as each axis is completed.

Crash safety (if applicable) is performed using both the impulse and sustained procedures. For the impulse procedure, the amplitude for the terminal peak sawtooth pulse is specified as 20g’s peak. As with the operational shock procedure, the nominal duration varies according to the equipment category between 11 and 100 mS.  Whether performed on a drop table or shaker, the availability of a dummy load or mass simulator with a similar center of gravity (CG) will aid in the setup and performance of these shocks by utilizing this unit to apply shocks during the setup phase. A dummy load may also be substituted for any electro-mechanical components mounted on or within the equipment case as long as it represents the same weight and CG to the assembly.

The sustained crash safety test is normally performed using a centrifuge or sled, but in special cases it may be acceptable to simulate the inertial effects by apply equivalent forces statically through the CG of the EUT. When performing the test using a centrifuge, remember that the direction of loading will be opposite to the direction of acceleration with respect to the rotational axis. Once again, a clear axis definition for the EUT will aid in the setup and performance of the test since all six directions of the aircraft mount orientation must be tested (Forward, Aft, Up, Down, Side [1], Side [2]). If the orientation of the equipment within the aircraft is not known, then the random for each of the equipment’s three orthogonal axes is defined in a table provided in Section 7. Acceleration (G’s) are calculated according to the relationship of the centrifuge swing arm radius, angular rotation (radians/sec), and the revolutions per minute (RPM) of the centrifuge. Crash safety is typically performed on non-operating equipment unless the equipment specification states otherwise. See more…!

EMC Testing

Solar radiation (sunshine) testing is one of the basic tests usually required for any military equipment planned to be deployed in the open and therefore subject to direct radiation from the solar source. The effects of this radiant energy can generally be divided into two groups or classes, heat effects and photochemical effects. Heat effects on exposed equipment can raise the internal temperatures of the equipment substantially above the ambient air temperature. Temperatures in excess of 160^oF have been recorded in parked aircraft exposed to the sun while ambient air temperature was in the 90^oF range. Photochemical effects of sunlight may hasten the fading of colors and lead to the deterioration of plastics, paints, rubber and fabrics. The combined effects may lead to the outgassing of plasticizers in some materials along with discoloration and a reduction in transparency.

MIL-STD-810G, Method 505.5 outlines two procedures for performing the Solar Radiation test. Procedure I requires a cyclic exposure based on the diurnal cycle and is most useful for determining heating effects on exposed materiel as well as materiel enclosed within a container. Procedure II is a steady state (non-cyclic) exposure most useful for evaluating actinic (photochemical) effects of ultraviolet radiation on materiel since it represents an accelerated test with a factor of 2.5. Because Procedure I is more akin to a natural cycle and does not have the acceleration factor of Procedure II, it is not an efficient cycle with which to evaluate long term exposures. Therefore, when it is used mainly to evaluate the direct heating effect, Procedure I can be performed with source lamp arrays emitting less than the full solar spectrum. Procedure II however, demands full spectrum sources emitting light in the ultraviolet range if the total effects of long term exposure are to be properly evaluated.

The solar light spectrum has been accurately measured over the wavelength range of 280 – 3000 nm as well as the power distribution within this range, and it is this range that we would seek to reproduce in the Solar Radiation test.  Reproducing this entire range using lamp sources however can be quite challenging. Sources emitting ultraviolet wavelengths between 280 and 400 nm tend to be quite costly and their performance deteriorates quickly. Some of the MIL-STD recommended sources such as xenon arc and carbon arc fall into this category.  In fact, it was reported that the first commissioned sunshine test facility in 1945 fell short of the contract requirements due to several deficiencies, one of which was the amount of UV that could be produced at the test item. Cost and reliability issues are why many test labs have chosen to perform only Procedure I  with source lamps covering the visible and infrared spectrum range of 400 – 3000 nm (0.4 – 3.0 µm).

Reproduction of the required environment for the Solar Radiation test requires a chamber space in which the ambient air temperature and airflow over the test item can be controlled as well as a solar light source which may consist of a single source in the case of arc-type lamps or a multiple source array in the case of metal halide or incandescent type lamps. The distance of the light source from the test item may be varied to achieve the required irradiance. Airflow over the test item can significantly impact test results. When MIL-STD-810D introduced the “cycling for heat effects” (Procedure I) the guidance for airflow was to use airflow as low as possible consistent with achieving satisfactory control of the ambient air temperature at the test item or between 0.25 and 1.5 m/s (50 to 300 ft/min). The current guidance from MIL-STD-810G has changed for procedure I to 1.5 to 3.0 m/s (300 to 600 ft/min) in recognition of better field data. The requirement for peak radiation intensity at 1120 W/m² has changed little over the history of the Solar Radiation test although there have been slight changes to the spectral energy distribution based on updated measurement techniques of the actual solar source. See more….!

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

hydraulic testing

Shocks along with impulse or constant loads are some of the common environments experienced by all equipment installed in aircraft. The tests described by Section 7 of the DO-160 standard apply shocks or constant loads to the equipment under test in order to simulate events encountered as part of normal aircraft operations. When applied in the prescribed manner, the operational shock tests of Section 7 verify that equipment will continue to function within specified standards during events such as wind gusts, landing or taxiing. Crash safety tests verify that equipment will not present a hazard to personnel by detaching from its mounting or separating into projectiles during an emergency landing. These tests can be divided into three general types:

• Operational Shock
• Crash Safety (Impulse)
• Crash Safety (Sustained)

The specific parameters and type of test to be applied is determined according to the equipment category. Four categories are defined in Section 7 (A, B, D & E). The category selection for equipment is usually chosen by the prime contractor or specifying authority who has knowledge of the ultimate installation location and aircraft type(s) and should be stated in the relevant equipment specification.  The category chosen will basically determine whether the standard or low-frequency variant of either operational shocks or crash safety will apply. As with any shock or acceleration test, a rigid fixture simulating the in-service installation and allowing easy attachment to the test equipment mounting pattern will help to insure a compliant and smooth flowing test sequence.

For the Operational Shock test, a terminal peak sawtooth shock pulse is applied to the equipment under test (EUT) with am amplitude of 6 g’s peak and a nominal duration of 11, 20 or 100 mS according to the defined equipment category. Equipment is normally tested in an operating or power-applied state. If planning to perform this test on a vibration exciter, there are two considerations. First, the required velocity and displacement will increase substantially with the longer duration (low-frequency) shocks. Secondly, the effects of any applied pre and post compensation may alter the temporal and spectral characteristics of the reference pulse. These effects are best illustrated by viewing the pseudo velocity shock response spectrum (SRS) associated with the compensated pulse. DO-160 also allows for applying an equivalent SRS to replace the terminal peak sawtooth pulse. Since these shocks are to be applied to each direction of each orthogonal axis, a good illustration of the axis definition for the EUT provided in the test procedure will help insure that the testing flows smoothly as each axis is completed.

Crash safety (if applicable) is performed using both the impulse and sustained procedures. For the impulse procedure, the amplitude for the terminal peak sawtooth pulse is specified as 20g’s peak. As with the operational shock procedure, the nominal duration varies according to the equipment category between 11 and 100 mS.  Whether performed on a drop table or shaker, the availability of a dummy load or mass simulator with a similar center of gravity (CG) will aid in the setup and performance of these shocks by utilizing this unit to apply shocks during the setup phase. A dummy load may also be substituted for any electro-mechanical components mounted on or within the equipment case as long as it represents the same weight and CG to the assembly. To get more details : emc testing.

emi testing lab

Solar radiation (sunshine) testing is one of the basic tests usually required for any military equipment planned to be deployed in the open and therefore subject to direct radiation from the solar source. The effects of this radiant energy can generally be divided into two groups or classes, heat effects and photochemical effects. Heat effects on exposed equipment can raise the internal temperatures of the equipment substantially above the ambient air temperature. Temperatures in excess of 160^oF have been recorded in parked aircraft exposed to the sun while ambient air temperature was in the 90^oF range. Photochemical effects of sunlight may hasten the fading of colors and lead to the deterioration of plastics, paints, rubber and fabrics. The combined effects may lead to the outgassing of plasticizers in some materials along with discoloration and a reduction in transparency.

MIL-STD-810G, Method 505.5 outlines two procedures for performing the Solar Radiation test. Procedure I requires a cyclic exposure based on the diurnal cycle and is most useful for determining heating effects on exposed materiel as well as materiel enclosed within a container. Procedure II is a steady state (non-cyclic) exposure most useful for evaluating actinic (photochemical) effects of ultraviolet radiation on materiel since it represents an accelerated test with a factor of 2.5. Because Procedure I is more akin to a natural cycle and does not have the acceleration factor of Procedure II, it is not an efficient cycle with which to evaluate long term exposures. Therefore, when it is used mainly to evaluate the direct heating effect, Procedure I can be performed with source lamp arrays emitting less than the full solar spectrum. Procedure II however, demands full spectrum sources emitting light in the ultraviolet range if the total effects of long term exposure are to be properly evaluated.

The solar light spectrum has been accurately measured over the wavelength range of 280 – 3000 nm as well as the power distribution within this range, and it is this range that we would seek to reproduce in the Solar Radiation test.  Reproducing this entire range using lamp sources however can be quite challenging. Sources emitting ultraviolet wavelengths between 280 and 400 nm tend to be quite costly and their performance deteriorates quickly. Some of the MIL-STD recommended sources such as xenon arc and carbon arc fall into this category.  In fact, it was reported that the first commissioned sunshine test facility in 1945 fell short of the contract requirements due to several deficiencies, one of which was the amount of UV that could be produced at the test item. Cost and reliability issues are why many test labs have chosen to perform only Procedure I  with source lamps covering the visible and infrared spectrum range of 400 – 3000 nm (0.4 – 3.0 µm).

Reproduction of the required environment for the Solar Radiation test requires a chamber space in which the ambient air temperature and airflow over the test item can be controlled as well as a solar light source which may consist of a single source in the case of arc-type lamps or a multiple source array in the case of metal halide or incandescent type lamps. The distance of the light source from the test item may be varied to achieve the required irradiance. Airflow over the test item can significantly impact test results. When MIL-STD-810D introduced the “cycling for heat effects” (Procedure I) the guidance for airflow was to use airflow as low as possible consistent with achieving satisfactory control of the ambient air temperature at the test item or between 0.25 and 1.5 m/s (50 to 300 ft/min). The current guidance from MIL-STD-810G has changed for procedure I to 1.5 to 3.0 m/s (300 to 600 ft/min) in recognition of better field data. The requirement for peak radiation intensity at 1120 W/m² has changed little over the history of the Solar Radiation test although there have been slight changes to the spectral energy distribution based on updated measurement techniques of the actual solar source.

When a Solar Radiation test is required,

• Perform the Solar Radiation test prior to the High Temperature test, as the product temperature measured in the solar chamber may need to be used as the ultimate high operating temperature for the product.
• Consider the orientation of the test item within the solar chamber so as to replicate the in-use conditions with respect to both the direct radiant light energy and the airflow direction. This will affect both the temperature gradients and any cooling effects provided by the airflow.
• When testing to Procedure I, remember that several consecutive cycles will likely be required for the product to achieve the ultimate high operating temperature for the most critical area of the test item to be within 2^oC of the previous cycle. This usually means 3 to 7 cycles.
• If operation of the test item is required, operational times will need to coincide with the peak response temperature of the test item in each cycle which will not coincide with the peak radiation intensity.
• See more details : http://qualtest.com/.