c. Test conditiona. This test is conducted by nounting the test item on a rail car in its rail shipment configuration and then i>erforming a series of at least foxir impacts. The first three inpacts shall be at 6.4, 9.7 and 13 km/h (4. О and В

iiph}, respectively, in the sarae direction. The fotsth shall be conducted at 13 nvh in the reverse direction. All fovsr ispacts sbjtll have a tolerance of Ю.В, -0.0 km/h. If the test connodity can be shipped in tm orientations (such as lengthwise and crosswise on the rail car), the four ivpactm shall be repeated for each orientation.

d. Rationale. Data for the rail inpact teat were derived from statistical data

on the frequency of inpacts with relationship to speed and frequent of сопсш^гепсе. Brakes are set on the buffer car to provide a sere ccr,servative tsst.

e. Failure analysis. A test item shall be classified as not having survived the rail inpact test and will be deemed a test fallxire If any item that is attached to or included aa an integral part of the test item breaks free, loosens or shoMS any sign

of permanent deformation beyond specification tolerances. A test item that passes this procedure should be capable cf rail trarisport without daraage tc tha item or tiedowns.

1-3.11 Procedure IX - Catapult launch/arrested landing.

a. Appl ication. This procedure is intended for equipment moisited In or on

fixed-wing aircraft that au-e subjected tc catapult lamches and arrested landings.

b. Restrictions. None.

c. Test conditions. Whenever possible, test conditions shall be derived from measured data on applicable carrying aircraft (see (Seneral Requirements, 4.3, Use of Field/Fleet Data), since shock responses can be affected by local influences such as

wing and fxiselage bending modes, pylon Interfac-es, and struct-ural damping.

However, if acceptable field-derived data are not available, the following guidance is offered in 4iich a sinusoidal burst is used to sinulate each catapult or launch event.

(1) Vbve shape - danped sine wave

(2) nuve frequsncy - deterralnsd by structwal analysis of speeifie

aircraft and location furiamsntal mode

(3) Burst anplitude - same as above

(4) Wbive danping (quality factor) - Q 20

(5) Axis - vertical, longitudinal

(6) Nvmfoer of bin-atg - determined by the specific application (for

exanple, 30 bursts, each followed by a 10 second rest period)

d. Bationale. The catapult launch/arrested landing shock environment differs from other typical shock events in that it is. in reality, a transient periodic vibration (roughly sinusoidal) at a reiatively low frequency determined by aircraft meiss and landing gear danping characteristics. Typical catapult launch and arrested landing shock time histories are shown in figure 518.4-6.

In general, catapult time histories will show two transient events corresponding to initial load application and catapult separation from the aircraft, with both transient events having a distinct oscillatory nature (reference f). For the purposes

of this procedure, however, this time history has been sinplified to a constant-anplitude sine burst of 2-secQnd duration of approximately similar characteristics.

While the pulse anplitxxles associated with this environment are low, the long periods of application and high frequency of occurrence have the potential to cause significant damaige in inproperly designed equipment.

A typical aircraft may fly as nsny as 200 sorties per year, of v*.ich more than two-thirds may involve catapult launches and arrested landings. However, for laboratory test purposes. 30 Simulated catapult/landing events in each of two axes (longitvidinal and vertical) should provide confidence that the majority of significant defects will be identified for remedial action.

Vertical

XLl I I I I

I .1 I I

J. i I

TiE* After Initialing Launch (Sec)

YertSeal

FIGURE 516.4-6

-I-L

0.5 . .

time After Initiating Arrestment. (Sec)

T,ni .al re>i>w # of aulHC * e tafttilt Iwtinehea and rrited Ipmlinea ahowlns OSUlllatorv Mturt Of

traweleni. (ИсГегепое f)

i-4 SPECIAL COKSIDERATIONS

1-4.1 Test interruption. Generally, if interruption оссгдгв during a pulse, that pulse shall be repeated. Care nust be taken to ensiire that stresses induced by the interrtpted pulse do not invalidate subseqiient test results.

1-4.2 Related shock tests

1-4.2.1 high iniaact/shipboard equipment. Shock tests for shipboard equipment shall be performed in accordance with MIL-S-901. Attention is directed to the ability to tailor MIL-S-901 tests through design of the fixture attaching the test item to the shock machine. As much as possible, the fixture should provide conpliance similar to that existing in the field environment of the test item.

1-4.2.2 Rough handling for packaiged items. Tests for shipping sufyd handling nay be performed in accordance with MIL-P-116 or FED-STD-101.

1-4.2.3 Fuzes and fuze components. Shock tests for safety and operation of fuzes and fuze conponents may be performed in accordance with MlL-STD-33i.

1-4.2.4 Corrf?ined tenperature arxi shock tests. Tests say be performed at room ambient conditions unless a high or low temperature shock test is required.

1-5 Rl!JfeJ<ENCES

a. Harris, C, and C.E. Crede, eds. Shock and Vibration Handbook, 2nd Edition, NY: McTQraw-Hill, 1976.

b. M?Grath, M.B. and W.P. Rader, Aerospace.ystems Jvrotechnic Shock Pata (Ground Test and Flight) Vol. I (NASA-CR-116437, STAR N71-17900), Vol. II NASA-CR-116450. STAB N71-17901). Vol. Ill (NASA-CR-116401, STAR N71-17902). Vol IV (NASA-CH-116402. STAR N71-17903) , Vol. V (NASA-CHl-l 16403, STAR N71-17904), Vol. VI. Rev. A (NASA-CR-116406, STAR N71-17805), 7 ftfarch 1870.

c. Qaberson, H.A. and R.H. Chalmers. Model Velocity as a Criterion of Shook Severity. Shock and Vibration Bulletin 40. Pt. 2, (1969) 31-49.

d. ANSl/ASTM D3332-77, Standard Methods for Fragility of Products Using Machines. 1877.

e. Conover, W.J. Practical Jfonparametric Statisties. New York: Wiley, 1971, Chapter 3.

f. Piersol. A.G. Analysis of Harpoon Missile Structural Response to Aircraft Launches. Landings and Captive Flight and Qtmfire. Naval Weapons Center Report NWC TP 5SS80. January 1877.

ИЕТтТ) 516.4 SHOCK SECTION II

II-l APPARATUS

II-l.l ApparatuB I. Apparatus I is used for procedures I, II. III. V. VII. AND IX.

II-l.l Test facility. The shock-prodijcing apparatus shall be capable of producing the test conditions as determined according to the appropriate paragraphs of section I of this Bsthodi The shock aprat-ja may be of the free fall, resilient reboimd. nonresilient, twdraulic. conpressed gas. electrodynamic shaker, or other activating types. Procedure VII may require pyrotechnic devices to sinulate field conditions. Procedures II and III require test apparatiis capable of producing relatively large displacement.

II-l.1.2 Calibration. The shock afparatus will be calibrated fer conforaanee with the specified test requirement from the selected procedure. Two consecutive shock applications to a calibration load shall be produced wtiich satisfy the test conditions outlined in procedure I, II, III, V, VII or IX. The calibration load shall then be removed and the shock test will be performed on the actual test item.

11-1.1.3 Controls. Tbe instrшaentation xjsed to measure shock pulses or shock acceleration spectra shall have the following characteristics.

a. AcceleromBter

(1) Transverse sensitivity of less than or equal to 5%.

(2) An anplitude linearity wdthin 10% from 5% to 100% of the peak acceleration anplitude required for testing.

(3) For procedures I, II, III, V and IX: A flat frequency response within

±\GX across the frequeney 5 - 2,000 Hz.

(4) For procedure VII: A flat frequemn responce within ±10Х across the frequency 20 Hz to the highest frequency specified in 1-3.9.

b. Analysis system

(1) Й11 not alias rers thsn a 5 percent msasurensnt error into ths frequency band of interest. (20 Hz to 10 KHz typically.)

(2) If filters are used to meet the previous requirement, a filter having linear phase-shift characteristics shall be used.

О) With filter (if used), shall have a pass band within one dB across the frequency range specified for the accelerometer (see II-l.1.3a).

c. Apparatus

(1) The shock apparatus shall be capable of prodixiing a transient that meets or exceeds the required spectral or pulse anplitude. For conparability or repeatability, the shock response spectrtm of the transient should not exceed the test condition by more than 3.5 dB for procedures I, V and IX and 6.0 dB for procedure VII (dB = 20 log A).

II-l.2 Apparatus II. The drop tester vised to conduct procedure IV (Transit Drop) tests shall be capable of producing the required inpacts to the test item(s) .

II-1.2.1 Test facility. Drops for equipment mass up to 454 Kg (1000 pounds) and having its largest dimension less than 91 cm (36 inches) shall be made from a quick-release hook, or drop tester. The floor or barrier receiving the inpact shall be of two-inch plywood backed by concrete. For equipment over 454 Kg, the floor or barrier shall be concrete.

II-1.2.2 Controls. Controls shall be adequate to assure that testing is conducted

as specified in table 516.4-11.

II-1.3 Apparatus III. The platform used for performing procedure VI tests (bench handling) shall be a solid wood bench top at least 4.25 cm (1.675 Inches) thick.

II-l.4 Apparatus IV

II-l.4.1 Test-facility. The following equiimient will be necessary to perform the rail inpact test (procedure VIII).

a. Two ordinary railroad cars, equipped with a draft gear coupling that will be used during shipment.

b. A prime mover for moving the cars.

II-l.4.2 Controls. The follomng are minimum test control requir nents.

a. A calibrated means to determine that the speed at the time of inpact is 6.4, 9.7 and 13 Km/hr (4, 6 and 8 mph) within +5%.

b. Accelerometers and associated circuitry to measure the inpact, shock, and equipment response, if these measurements are specified.

Step 1. Following the guidance of 1-3.3c, select test conditions and calibrate the shock apparatus as follows:

a. Select accelerometers and analysis techniques Miiich meet the criteria outlined II-l.1.3.

b. Mount the calibration load (the actual test item, a rejected item, or a rigid dumny mass) to the test apparatus in a nanner similu> to that of the aetiial test item. If the test item is normally mounted on vibration isolators, the isolators shall be functional during .he test.

c. Perform calibration shocks until two consecutive shock applications to the calibration load produce waveforms which meet or exceed test conditions derived from 1-3.3, for at least one direction of one axis.

d. Ramove the calibrating load and inst-all the actual test item on the shock apparatus.

Step 2. Perform a functional check on the test item.

II-2 PREPABATION FOR TEST

II-2.1 Preliminary steps. Prior to initiating any testing:

a. Choose the appropriate test procedures (1-3).

b. Deteraiine the shock levels for the pr-ocediir-es chosen.

11-2=2 Preteet.eheekQiit. All items require a pretest checkout at standard ambient conditions to provide baseline data. Conduct the checkout ais follows:

Step 1. Conduct a conplete visual examination of the test item with special attention to stress areas.

Step 2. Document the results.

Step 3. Wiere applicable, install the test item in its test fixture.

Step 4. Conduct an operational checkout in accordance with the approved test

plan.

Step 5. Document the results for conpliance with (Seneral Requirements.

Step 6. If the test item operates satisfactorily, proceed to the first test required by II-2.1a. If not, resolve the problem and restart at Step 1.

II-3 PROCEDLRES

II-3.1 Procedure I - Functional shock

Step 3. Subject the test item (in its operational made) to the test transient.

Step 4. Becord necessary data to show that the transients met or exceeded desired test levels. This includes test setup photos, test logs, and photos of actual shock transients. For shock/vibration isolated assemblies within the test item, measurements and/or- inspections should be made tc assure these assenfcliss did not impact with adjacent asse!!i>lies.

Step 5. Perform the functional check on the teat item. Becord performance data.

Step 6. Bepeat steps 3,4, 5, and 6 three times for each orthogonal axis that is to be tested in both the positive and negative directions. (If negative and positive acceleration spectra of one transient meet or exceed desired test levels for an axis, they can be counted as two transients, one in each direction.)

Step 7. Document the tests.

II-3.2 Ргосеаш'е II - Ecruipment to be..packaged

Step 1. Following the guidance of I-3.4c, calibrate the shock machine as follows:

a. Mount the calibration load (the actual test item, a rejected item, or a rigid dumiv mass) to the test apparatus in a nanner similar to that of the actvjal test item Use a fixture similar in shape and configuration to the shock

attenuation system iiich will simport the test item In Its shipping container. (The fixture should be as rigid as possible to prevent distortion of the Shock pulse inparted to the test item)

b. Perform calibration shocks until two consecutive shock applications to the calibration load produce waveforms which are all within the tolerance envelope of

ths specified waveform (figure 516.4-5).

Step 2. Bemove the calibrating load and install the actual test item on he shock apparatus.

Step 3. Perform a fvrictional test on the test item.

Step 4. Subject the test item to the test pulse.

Step 5. Becord necessary test data. This shall include test setup photos, test logs, and photos of the actvjal test pulse.

Step S. Perform a functional test on the test item.

Step 7. Bepeat steps, 2, 3, 4, and 5 once in each direction for three orthogonal axes (six shocks).

V = 2 V(2 gh)

Where V maximLin test item velocity change, cm/s (in/s) (sumnatlon of iEBpact velocity and rebouTid velocity) h = design drop height, cm (in) g - 980.6 onv/s2 (386 in/s2)

The drop height of the shock test apparatus will not necessarily be the same as the design drop height.

Step 4. Set the shock test apparatus to obtain a maxiuun acceleration (A and maintain the required velocity change below the anticipated failure level of the test item. If no information is available on anticipated failure level, set the shock test apparatus to obtain a maxinum acceleration level of 15 gs. Pulse durations can be determined using the following relationship:

V - gA (0.9td)

Step 5, Perform one shock test using pulse sho ) in figire 516.4-5.

Step 6. Examine the recorded shock pulse to be certain the desired maximum acceleration (AjjP and velocity change were obtained. Methods for determining maximum acceleration and velocity change are given in step 3.

Step 7. Examine or functionally test ths tsst item to dstermirts if dansage due to shock has OGCVB*red.

Step 8. If no damage has occurred, set the shock test apparatus for a higher maximum acceleration (Ад level while maintaining drop height (and thus velocity change) constant.

Step 8. Docunent results.

II-3.3 Procedure,III - Fragility

Step 1. Install the test item on the shock apparatus vising a fixture similar in shape and configuration to the shock attenuation system niich will support the test item in its shipping container. (The fixture should be as rigid as possible to prevent distortion of the shock pulse Inparted to the test item.)

Step 2. Select the design drop height from 1-3.5c.

Step 3. Adjust the shock apparatus to obtain a maxinun test item velocity change obtained from measured data or as given in table 516.4-1. If maxinun test item velocity change values are required for design drop heights other than those listed, the folloi dng relationahlp nmy be xmed.

Step 9. For all faces, repeat steps 5. 6, 7, axvd 8 with incrementally increasing maximum acceleration (Ащ) until test item damage оссш°а. The maxisus acceleration prior to v<hich damages occur is taken to be the shock-fragility level for the test item in the direction tested.

II-3.4 Procedure, IV - Trarit drop

Step 1. Install the test item in its transit or combination case as prepared for field use.

Step 2= From I-3.Q. determine the height of the drops to be performed, the пшпЬег of drops per test item, and the drop surface.

Step 3. Perform the required drops using the apparatus of II-l.2. The droi>s should be in accorlance lth table 516.4-11. It is suggested that the test item be visual ly and/Or operational ly checked periodical ly during the drop test to sinplif у any follow-on failure evaluation that nay be required.

Step 4. Document the inpact point or surface for each drop and any obvious damage.

Step 5. Following completion of the required drops, visually examine the test itera(s}.

Step 6. Document the results for conparison with data obtained in II-2.2, step

Step 7. Conduct an operational checkout in accordance wdth the iфproved test

plan.

Step 8. Document the results for conparison vrlth data obtained in II-2.2. step

II-3.5 Procedure V - Crash hazard

tiOTE: If calibration of the test apparatus is required, perform steps 1 and 2 cf II-3.1 first.

Step 1. Secure the test item mount tc the shock apparatus by its normal mounting means. The test item shall be a representative equlpnient item cr a mechanically equivalent mcckijp. If a mockvp is used, it will represent the same hazard potential, mass, center of mass, and mass moments about the attachment points as the item sinulated.

Step 2. Perform two shocks in each direction (as determined in I-3.7c) along three orthogonal axes of the test item for a maximum total cf 12 shocks.

Step 6. Operate the test item in accordance writh the approved test plw.

Step 7. Docunent the results for conparison wri.th data obtained in II-2.2, step

II-3.7 Procedure VII - Pyrotechnic. Same as 11-3.1, except that твавшва or analytically derived data shall always be used as test conditicr.s.

II-3.8 Procedure VIII - Rail inpact

Step 1. Position from one to five rail cars on a level section of track. Satisfy the followrLng conditiona:

Step 3. Perform a physical inspection of the test setup. Operation of the test item is not required.

Step 4. DocxjRient the results of the physical inspection including ш assessment of potential hazards created by equipment breakage or deformation.

II-3,e Progedure VI - Bench handling

Step 1. Configure the item as it would be for servicing - for example, with the chassis and front panel assenbly removed from its enclosure. Position the item as it would be for servicing.

Step 2. Using one edge as a pivot, lift the opposite edge of the chassis mtil one of the following conditions occur (whichever occurs first).

a. The chassis forms an angle of 45° with the horizontal bench top.

b. The lifted edge of the chassis has been raised four inches above the horizontal bench top.

c. The lifted edge of the chassis is jvst below the point of perfect

balance.

Let the chassis drop back freely to the horizontal bench top. Repeat, using othsr practical edges of the same horizontal face as pivot points, for a total of four

drops =

Step 3. Repeat step 2 with the test item resting on other faces until it has been dropped for a total of four times on each face which the test item could be placed practically during servicing. The test item shall not be operating.

Step 4. Visually inspect the test item.

Step 5. Docvment the results for conparison wrtth data obtained in II-2.2, step