1-4.2.3 Sintjaoidal vibration. The service vibration environment in sc propeller aircraft and helicopters contains excitation iich is basically sinusoidal in nature. The excitation derives from engine rotational speeds, propeller and turbine blade passage freqviencies. rotor blade passage aitd velocity, and their harmonics. Environments such as this may be best simulated by a sinusoidal test. Caution nust be exercised to assure that the frequency range of the sinusoidal exposure is representative of the platform environment.

Most vibration problems are associated with a resonant response of the equipnent Item or conponent to the platform soijpce excitation. Thus, the traditional sweep sinusoidal vibration test technique is not used in this method for representation of the actual service condition. Swept sinusoidal testing is a useful engineering development technique.

1-4.2.4 Besponse characterization. Bsspcr,se characterisation is a tei.iqus for measuring the structural response of equipment or test fixtures to applied vibration. Response characterizations may either use broadband or swept-sine excitation. They are performed for reasons viiiich Include, but are not limited to:

(1) Identifying the frequencies at viilcdi an item resonates, especially vten those freqtiencies might be present in the service vibration enviroranent.

(2) Evaluating fixtvse/test item interactions to ensxnre reasonable duplication of knowi or expected service-induced responses.

(3) Determining appropriate locations for test control instrumentation.

Response characterizatioris should ultlsately be perfcrmsd at realistic vibration levels since non linear ities in equipssnt re9p0r.se render characterisations at other levels inconcliialve.

realistic test. Source dvvell testing should be performed using one of the following techniques:

(1) Broadband random excitation with vibration peaks centered at the fundamental and harmonic frequencies of the platform.

(2) Narro A>and random, simeriraposed over a low-level baekground broadband random signal with the narro% band portion centered at the fundamental and harmonic frequencies. (ЮТЕ: The narro tiand signals may also be cycled through a frequency band representative of the platform conditions).

(3) Sinusoidal inputs at the fiSidaraental frequencies and harmonic frequencies either singularly or sin&ilt-aneoiuly. A low-level random background may also be added to the sinusoids. (NOTE: The sinusoidal inputs may be cycled through a frequency band representative of the platform conditions).

1-4.2.5 Test axes. Unless otherwise stated in specific procedures, test items shall be excited along three orthogonal axes. Excitation shall either be directed along each axis, one axis at a time or applied along two or three cf the axes simultaneously.

1-4.2.6 Input control versus response-defined control. Input control is the traditional approach to vibration testing. Ideally, this form of testing should represent the Input from a carrying platform Into equipment on the platform. It should not be used tten the equipment mass-loading could significantly alter the platform behavior or when the actual servioe excitation Is applied to all parts of the structure simultaneously (I.e., aerodynamic turbulence) rather than through a few distinet attac>unent points.

Besponse-defined testing uses an essentially undefined input and Instead tries to achieve an equipment structural response representative of that anticipated or measured in service. This approach is especially appropriate when service vibration measurements exist and close correlation between laboratory and service conditions is readily achieved.

1-4.2.7 Test durations. Test durations should be chosen along with test levels to acconplish the test purpose. Ouidance is included in the individual test technique discussions of 1-3, 1-4.3, and 1-4.6.

Usially vibration criteria ar© written in terms of total time at a given level

and are inplemented as a continuous exposure. However, service exposure is

usually made up of a series of discrete or short-term events. Thus, continuous

application of vibration could result in unrealistic structural, isolator, or

other heat buildvp effects. Vibration should be applied for short periods

representative of service conditions. Vibration-on periods should be alternated

with vibration-off periods of sufficient length to allow heat to dissipate. Exanples of

intermittent vibration events requiring guch treatment are gimfire and aircraft

maneuver Iniffet.

1-4.3 Endurance versus functional testing. Fxinetional tests (See 1-4.6.3.1) are intended to demonstrate that the equipment will function satisfactorily in the service envircrjnsnt. ThtjS, functior.al test levels normally are the maxinun levels expected in nornal ше at which full fvnetion of the equipinent is required. Mhere partial or degraded functioning is permitted under particular environmental extremes, an additional functional test should be acconplished accordingly. In cases where the relationship between vibration stress level and equipments degree of performance is uncertain, functional testing at lower levels should be considered.

Endura-nce testing (See 1-4.6.3.2) is conducted to demonstrate that the equipment has a structural and functional life which is conpatlble wTlth the system/subsystem life requirements. An endurance environment is one in which the equipment is not required to meet all performance specifications. No damage is allowed while it is operating and the system nust exhibit unimpaired performance when the endurance environment is removed.

Endurance testing does not establish fatigue life (See 1-4.6.3.2). This is because:

(a) The teat item is tested for the ajnount of stress anticipated for one lifetime but not necessarily to destruction, and

(b) Because the sanple size Is too small.

Bather endLa ance testing assures that the required life can be achieved with reasonable .nsiintenance. The determination of the items useful life геф>1гев a combined environments test (method 520.1) wiiere all relevant environments are varied realistically and a sufficient number uf sanples are tested to failure. A test item which has survived an endurance test is not necessarily used \jp; however, the risk of failure in further use is higher than Uiat of a new xjnit. So the test xjnit should not be used for a true life test, a reliability demonstration, or a safety-eritlaal application. Other uses are acceptable if the increased risk of failure is compatible with the use.

1-4.4 Mechanical inpedance effects. Allowance should be made for mechanical impedance effects Mienever the benefits of increased realism are worth the time, effort, and cost required for inplementation.

Equipment structures dynamically influence their own response to an external forcing function. At structural natural frequencies where the response stresses are high, the structure will load the adjacent supporting strttctures (i.e., notch the acceleration spectral density at these frequencies). The magnitvide of loading effects is related

to the relative inpedance of the equipment structure and support struatm eB. As a rule of thumb, the resor.ant element exhibits a loading force in proportion tc its dynamic weight multiplied by the corresponding anpl if ication factor.

Mechanical inpedance effects can be accounted for in establishing vibration test spectra. The depths of notches are determined by measurement or by calculation. Bei 54 gives guidance in this matter.

1-4.5 Determination of dwidth for source d<wll testing. Test spectra representative of this type of testing are presented in figis*es 514.4-7 and 514.4-9. Test bandwidths should be based on measured data if possible. When data are not available, the bandwidth can be defined as:

Vhere: BW, = the bandwidth at a level 3 dB below the peak PSD level F = the fundamental frequency, f or one of the harmonics:

M. h- и

This peak bandwidth should be readily achieved by even the least sophisticated digital random vibration control system. The bands between the vibration peaks are filled with broadband random vibration at a level representative ef the platform being siraiilated. When variable RPM cases (see 1-3.4.1) are being simulated, wider bandwidth will be required.

1-4.6 Test phases.

1=4.6.1 E:r.ginssrir.g dsvslopmsnt tegtir.g. Enginesrir.g development testing is tsed t© meever desl i and construction defieieneiee as quickly as i>ossible and to evaluate subsequent corrective actions. It should begin as early as practical in the development phase and continue as the design matures. The ultimate purpose is to assure that developed equiixnent is conpatlble with the platform environment and that qualification testing does not reveal that more development work needs to be done. The tests have a vsf iety of objectives. Ther-efor-s. ccriSiderable freedom can be taken in selecting test vibration levels, excitation, frequency ranges and durations. Typical programs may Include i>esonant search acconplished by exposing the item to low-level sweep sine input over the frequency range of concern. Sine dwells are then used to obtain mode shapes. Fast Fourier transform analyses of random inputs can also be used to acconplish this. Mode shape and frequency determinations are necessary for verifying structural dynamic models and for discovering platform/equipment conpatibi 1 ity problsns. Once node shapes as well as module frequencies have been identified, the test item may be exposed to dwell, swept-sinusoidal or random excitation testing. The vibration intensity of this testing is selected to acconplish specific test objectives. The level may be lower than the field environment to avoid excessive damage to a prototype, higher to verify the test items structural integrity, or raised in steps to evaluate performance vviations and obtain failwe data.

1-4.6.2 Environmental worthiness. Wbrthiness testing is performed to verify that prototype or test versions of equipment are adequate for use in a system or siibsystem test. Levels and durations should be selected to provide confidence that the equipment will perform well enough to support the test program with an acceptable level of maintenance. In cases vd>ere safety is a factor, the test must be eidequate to assure safe operation or possible failsafe operation. Levels are xjsually typical operating levels unless safety is involved; then maxinum operating levels are necessary. Durations are either long enough to check equipment function or an arbitrary short time (5-10 minutes), whichever is greater.

1-4.6.3 Qualification. Qualification tests are used to verify that production equipment is capable of operating to specified performance criteria tbrQiighout the range of environments of its service application and to provide reasonable assurance that life requirements will be met (see 1-4.3). This normally requires functional tests to acconplish the first goal and endurance tests for the second.

1-4.6.3.1 Figictional tests. Fimctional test levels are normally the maxitrun service levels. Viien there is significant non-linearity, testing at lovesr levels should be considered. When separate fimctional and endwance teats are required, the fimetional test duration should be split, with one half acconplished before the endurance test and one half after the endurance test (in each axis). The duration of each half

VenmD 514.4

relationship to determine the time at maxinun service levels (functional levels) wiiich is equivalent to a vibration lifetime (levels are different for different mission profiles). Use the equivalent time as the functional test duration, thereby cootoining functional and endxirance tests. There may be cases when this test duration is too long to oe conpatible with program restraints. In this case, use as long a test duration as is practical and use the fatigtie relationship to define the test level. Hcwsver. in no cass should endurance test levels and durations be less than those specified in 1-3.4.9.

1-4.7 FatKue relationship. The following relationship may be used to determine the reqxilred test times at fxsictlonal levels to satisfy endurance

requirenients ОГ пёл necessary tO develop the ratio between functional oiid e.xlurance levels:

where

W = Vibration levels (acceleration spectral density) T = Time (hours)

M = №terial constant (slope of log/log random s/N curve)

This relationship is a sinplifled expression of linear fatigue damage accumulation for typical materials xsssd in electronic equi; nent. Mere scphisticatsd analysis techniques can b* used 1Ф*п warrsnted. A value of 4,0 for M Is аоягвэпХу used; other values may be appropriate. (Note: If this equation is used for sine calculation, W represents peak g and M = 6 in general case, 2.5 in the case of electronic boards.

nETHDD 514.4

shiculu be Sufficient tc fully verify equipiusnt functicn cr cne half hcur (1 hciiP per axis), whichever is greater. This arrangement has proven to be a good way of adequately verifying that equiwnent survives endurance testing in all respects.

1-4.6.3.2 Endurance tests. In the past, endurance test duration was normally set at one hour per axis. Test levels ere established by raising fijnctional levels to account for equivalent fatigue damage. Another approach is to establish levels and durations to tsst to Kaxinun service levels for a duration sufficient to reach the naterial endurance limit (approximately 10® cycles at each resonant frequency). These techniques are basically valid: however, both have shortcomings. The first technique results in test levels higher than field levels - in some cases, such higher.

The fatigtie relationships (1-4.7) used to generate these criteria are sliqiilliied representations at best arid siien structural non linearity at high vibration levels becomes a factor, the validity ef the relationship is questionable. The second technique depends on the definition of endurance limits. This is a fwther sinplifIcation of the already simplified fatlgi relationship. Fwther. It is shown that some materials do not exhibit endurance limits.

1-4.8 Vibration isolation devices. Vibration isolators (shock mounts), isolated equipment shelves, Mid other deviees designed to protect eqiiipment from platform, or shipping environments use low-frequency resonemce to attemoate high-frequency vibration inputs. Effective performance of these devices depends on adequate frequency separation between isolation resonant frequencies and equipment resonant frequencies, and sway spaice (clearance around isolated elements) to avoid impacts of the isolated elements with surrounding equipment and strxicture.

All militaay equipment should have a mini.n mi level of ruggedness even if it will be protected by isolation in its application environment. To assure that these requirements are met. sway anplitijde and isolation characteristics (transmissibi 1 ity versus frequency) should be measured during all vibration tests. These parameters should be measured at eeich test level. This is necessary becatise isolation devices are nonlinear. This is also true when sub-elements are isolated within equipment items. Further, all isolated equipment should pass the Mlninajm Integrity Test (1.3.4.9) ..

1-4.9 Test setup. Unless otherwise specified in the individual test description (section 1-3). the test item shall be attached to the vibration exciter by means of a rigid fixture capable of transmitting the vibration conditions specified. The fixture Should input vibration to racks, panels, and/or vibration isolators to simulate as accurately as possible the vibration transmitted to the test item in service. However, all equipment items protected from vibration by these means should also pass the minimum test requirements of 1-3.4.9 with the test item hard-mounted to the f ixture.

1-4.10 Equipment operation. During ail pi at form-induced vibration simulations, the test item should be functicning and its performance should be measured and recorded, if it would normally be operating under these conditions in service. Performance to full specification requirements should be required during all functional tests. Measurement of performance level attained should be required when endurance levels are higher than fvnctlonal levels (1-4.6.3).

1-4.11 Failtg deiinition. During qiial if ication testing, the equiment shall not suffer permssnent deformation cr fracture, no fixed part or assent; 1 у shall loosen, no moving or movable part of an asseirbly shall Ьесотв free or sluggish in operation, no movable part or control shall shift in setting, position, or adjustment, and equipment performance shall meet specification requirements while exposed to functional levels and following endurance tests. Any deviation from the above shall constitute a failure.

For tests other than qualification tests, success arei/or failure criteria shall be prepared which reflects the purpose of the tests. For exanple, a step stress test might be conducted to find the level at which a mechanism fails to operate properly. The test would be deemed Sijccessful when this level is found.

1. Csrr. R. L. Vibration Test M50A1~PI Tank: Final Test Report. Contractor Test. Lima, OH: Chrysler Corp., April 1S78. Contract No. DDAF-03-70-C-0075.

2. Total System Vibration Flight Test Report. UH-60 Blackhawk. Stratford. CT: Sikorsky Aircraft Corp., March 1Э80. Sikorsky Report No. SER-T0407.

3. Storey, E. M. et al. Evaluation program of the Vibration Enviroranent of Armament Systems Externally Mounted to Arnv Helicopters. December 1969. AMSMI-RT-TR-69-34.

4. Laing, E. J. et al. Vibration and Tenperatxire Survey CH-54B Helicopter. March 1973. AvsCOm Final Report.

5. Thomas, C. E. Flight Vibration Survey of.H-37A.Helicopter. June 1960. WADD-TN-60-170. DTIC No. AD-249-7S9.

6. M=Intosh, V. C. and P. Q. Bolds. Vibration and Acoxistic Environment of OH-A Helicopter Configure with and Using the XM-27 Armament System. February 1975. AFFDL-TS-74S1. OTIC No. B003-236L.

1-4.12 Qual if ication test completion. A qijial i f ication test is conplete 4)en all elements of the test item pass a conplete test. Mhen a failure occurs the test shall be stopped. The failure shall be analysed and repaired. The test shall then continue until all fixes have been exprased to a conplete test. Each element is considered qualified ien it has been exposed to a conplete test, wuallieu elements wich fall **ior to test Gcn*letion are not considered failures but wil 1 be reired to allow best conpletion.

1-4.13 Sijunarv of test infornation required. The following information is required in the test plan to adequately condvict the tests of section II.

a. Test procedure.

b. Test item configuration.

c. Operational requirements.

d. Test levels and duirations.

e. Test set-LK) description.

f. Accelerometer location and calibration.

7. Thonas. С. E. Fli<ht 5urvey of C-130A Aircraft. March 1972. ASD-TDR-62-2167. DTIC No. AD-274-904.

S. Boids. P. G. Flight Vibration Survev C-133. Aircraft. April 1972. ASD-TDE-62-3S3. DTIC No. AD-277-128.

9. Lunney, V. J. and C. Crede. The Establishment of Vibration and Shock Tests for А1г1югпе Electronics. ttk lght-Patterson AFB. OH: Weight Air Development Center, Janxjary 1958. WADC-TR-57-75.

10. Junker, V. J. and C. Crede. TheEvolution of .USAF Environmental Testing. October 1975. AFFDL-TR-e5-197. DTIC No. AD-625-543.

11. Frost, W. Q. , P. B. Tucker, and G. R. Wfaymon. Captive Carriage Vibration of Alr-to-Air Missiles on Fighter Aircraft . Journal of Environment Sciences. 21:15. (Septeidber/October 1978). pp. 11-15.

12. Dreher, J. F.. E. D. Lakin, and E. A. Tolle. Vibroacoustic E.nvironment and Test Criteria for Aircraft Stores During Captive Flight. Shock and Vibration Bulletin 39. Supplement (1989), pp. 15-40.

13. Dreher, J. F. Effects of Vibration and Acoustical Noise on Aircraft/Stores Conpatibi 1 ity. Ih: Aircraft Store Conpatibi 1 ity Synposiun Proceedings.

Vol. 6, November 1969.

14. Piersol, A. G. Vibration andoustieTestJJritgria for Captive Flight of Externally Carried. Stores. December 1971. AFFDL-TR-71-15e. DTIC No. AD-893-005L.

15. Dreher, J. F. Aircraft Equipment Random Vibration Test Criteria Based

on Vibrations Induced by Tuffbulent Air Flow Across Aircraft bcternal Swfaces . Shook and Vibration Bulletin 43. Part 3. 1973. pp. 127-139.

16. Wfeifford, J. H. and J. F, Dreher. Aircraft Equipment Vibration Test Criteria Based on Vibration Induced by Jet and Fan Engine Exhaust Noise. Shock and Vibration Bulletin 43. Part 3, 1973, pp. 141-151.

17. Bandom Vibration Teat Requirements for Equipment Installed in B-52G/H Airplanes. Wichita: Boeing Conpany, October 1977. Boeing Report No. D-675-60000.

18. EnvironmBntal.J)eaign Requirements and Test .Procedures. F-4 Jlircraf t Electronic Equipment. St Louis: MrDonnell .Aircraft, 1962. M:;Donnell Report No. C-66210.

19. Hinegardner. W. D. et al. Vibration and Acoustic Measurements on the RF-4C Aircraft. Wright-Patterson AFB. OH: ASD Systems Engineering Group. 1967. TM-sCT-67-4.

20. F-15 Vibration. Shock, and Acoustic .Design Be<juireinBnta and Teat ~1 Frocedupes for Aircraft Equipment Installations. St Louis: №Donnell

Aircraft, 1969. McDonnell Report No. 0397.

21. F-16 Air Confcat Fighter Environmental Criteria. Ft Vfcrth: Qeneral Dynamics, 1976. General Dynamics Report No. 16PS011C.

22. F-16 Nunfeer 3 Vibration and Aeovgtlc Flight Measurements. Ft Vtorth: Qeneral Dynamics, 1979. Qeneral Dynamics Report No. 16PR903, Vol. 1.

23. F-16B Nunber 1 Vibration and Acoustics Flight Measurements. Ft Worth: General Dynamics, 1979. Qeneral Dynamics Report No.loFiwOj, Vol. 2.

24. Environment Criteria Specif ication for Model F-UIA/D Weapon System-

Ft Wrth: Qeneral Dynamics, 1963. Qeneral Dynamics Report No. FZM-12-104B.

25. F-111 Final Environmental Vibration and Acoustic Analysis. Ft Worth: General Dynamics, 1965. General Dynamics Report No. FZS-12-057A.

26. Vibration Measurements for F-lllA No. 75..Clean Airplane in Level Flight. Ft Wtorth: General Dynamics. 1971. General Enamics Report No. F2S-12-32L.

27. Final Report. F-lllA Category 1 Vibration and Acoustic Measurements During Loads Testing of F-lllA No. 75. Ft Worth: General Dynamics, 1972. General Dynamics Report No. FZS-12-1040.

28. A-10 Acoustic and Vibrationport. Farmingdale, NY: Fairchlld Republic Co., 1974-1978. FairchiId Report No. SF160N004.

29. A-lOJcoustic and Vibration Report. Non-Gunfire. Farmingdale. NY: Fairchi id Repxibiic Co., 1977. Fairchi id Report No. SF160N004, pendix Б.

30. Mimura. H. H. Processing of A-7D/E ircraft Equipment Vibration Data. Final Report. January 1979. AFFDL-TR-78-177. DTIC No. AD-B036-115L.

31. Instrument and Avionics Co g?artments Environmental Survey: Production 0K-5BA Helicopter. Septenfcer 1972. AVSCOM Project No. 70-15-1.

32. Vibration and Tenjoerature Survey: Production UHIH KellcQPter. January 1973. AVSCOM Project No. 70-15-2.

33. Vibrationand Tenperature Sxirvey: Production 0H-6A Helicopter. August 1973. AVSCOM Project No. 70-15-4.

34. Vibration and Tenperature Survey: Production AH-IG Helicopter.

Nbreh 1974. USAASTA Project No. 70-15-5.

MIL=STD-810E 14 JULY 1989

35. Vibration гик! Tenperature Survey: Production CH-47C. March 1976. USAAEFA Project No. 70-15-6.

36. Schrage, D. P. and R. H. Lutz. Environmental Vibration Testing of Helicopter Stores and Equipment to the Procedures Outlined in MIL-STD-BIOC. IN: 35th Annual Fonar. of ths American Helicopter Society, fey 1978.

New York: The Society, n.d.

37. Crews, S. T. Helicopter Conponent Environmental Vibration Testing --Poor Mans Fatigue Test. IN: 35th Annual Forum of the American Helicopter Society. И(ву 1979. New York: The Society, n.d.

3B. Foley, J. T. et al. Transportation Dynamic Ep.viron.ment Sunmarv, Albuq[uei4Iije: Sandia National Laboratories, 1973. Sandia Environment Data Base No. EDB-A1354.

39. Schneider, C. W. C-5 Environmental Vibration Flight Test Report, jferietta, OA: Lockheed, 1971. Lockheed Iteport No. LGlUT78-i-2.

40. Kuhn, D. L. toalygia of the Vibration Environment for Airborne Reconnaissance Integrated Electronics System (ARIES) Installed on EP-3E Aircraft. Indianapolis: Naval Avionics Center 443. 1975. Document No. ESL-163.

41. Kuhn, D. L. and R. M. Jchjiscn. Evaltation of the Vibration Envirorjnent for the Doppler Ranging.Information System. Indianapolis; Naval Avionics Center 443. 1982. Document No. ESL-420.

42. Analysis of the Vibration Environment for ТДСАЮ IV В System Installed on Ш-1300 Aircraft. Indianapolis: Naval Avionics Center 443, 1976. Docufaent No. ESL-199.

43. Kiihn, D. L. Evaluation of Flight Data for the Big Look Antenna System 0E-319/APS Installed on EP-3E Aircraft. Indianapolis: Naval Avionics Center 443, 1981. Document No. ESL-418.

44. КгЛп, D. L. Analysis of FliKht Data for Deepwell gystem Installed in EP-3E Aircraft. Indianapolis: Naval Avionics Center 443, 1975. Document No. ESL-169.

45. Thomas, C. E. Flight Vibration Survey of SC-123D Aircraft. February 1972. Document No. ASD-TDR-62-235. DTIC No. AD-274-903.

46. Liles, C. D. Ж:-130Н Noise and Vibratior. Test P.eport. Isferietta, OA: Lockheed-Cieorgia, 1968. Lockheed Report No. ER-6707.

ЛеТНОО 514.4