1、- 00 0 Socisty of Automotive Engineers, Inc. p E R ON A U T I C A L 28 Nsst h CS t y rest R E C O M M E N D E D P R A C T I C E ARP467 I EQUIPMENT FRAGYLITY DATA I ssusd 1“ I Revisd gEY VO Pe na aoo vv Wa o 9 W M O .o =oo ;_ ea e !m0 . :; o -fLCq 80n0 N q OF =s - E s; y 00 vijo ;eSd o,p : Mo !$gE e
2、4 .o _ -$r w,rg $w roE oe Ei po $o V MO 1. FOREGRD: 1.1 In the design of equipnent packaging te practice has been to select a cushioning material and a cushioning thickness by empirical and/or economic methods some of the time and by rather arbitrary or guess methods on other occasions. 1.2 Judgment
3、 has played a large part in cushion desin. Judnent based on safety +,o tt product tends toward excess cushion and when based on cost of cushion, tends toward inadequate cushion. The net result is a tendency for o ersize and overweight packages or inadequate packages and no common ground has existed
4、from which to judge the adequacy of a cushion. 1.3 It has become the praetice to desigm much equipnent to resist a specified nwnber of shocks in each of three mutually perpendicular directions. T hese shocks are usuall,y defined as a rnunber of gs“ or the ratio of terminal deceleration to 32.2 ft. p
5、er second per second. T he definition is sometimes annented by a specification of the time duration of the shock which is very important from the standpoint of energy imparted to the equinnent. The product of “gs and seconds (g - sec) is findin increasing use. 1.4 The manner of presentation of shock
6、 test specifications has frequently not been a concise or precise description of the desirel pr.enomenon. The test methods specified do not consistently and dependab,y duplicate the specified phenomena. It seems reasonable to expect that the method of specification and test can ultimately be rationa
7、lized and more precisely defined. 2. GENERALs If equipnent can be evaluated for a fragility rati,ng in terms of pYysical shock and duration which it will generally withstand wi*hout damage, mathematical means may be devised whereby a propei cushion can be desiPned. It is recoimnended that the manufa
8、cturer consider determination of cushion design based on the following criteria; 2.1 Degree of shock (number of gs) which the eauipment is known to withsLand and the time duration of each shock, mil.liseconds. 2.2 Total rnmber of shocks (all directions) given equipnent. 2.3 Resonant frequencies in p
9、ackaged equixnent. T hese data should ba recorded and used for design in their most severe knoWn satisfactoza+ values and as subsecuent testing may show more severe values to be satisfac+ory the new figures should be used for guidance in package re- design. 3. GTERIA FOR DETFRMFNING R.ATIVGs 3.1 Fra
10、pility rating is a group of numbers which forms a definition or specifica- tion of the largest magnitude of likely accidents and their nature which a device can tolerate without impairing its usefulness. Copyrlsht 1.976 61r Soo1tY of Automotive Enslnsrs. Inc. Printed In U. 8. A. , pp I ed 3-15-56 I
11、EtTIFMENT FPAGILITY DATA Revised - 2 - 3.2 The first siQnificant evidence of change of performance characteristics occurs when the fragilit,y rating has been exceeded. 3.3 Arryy evident mechanical damage shall be cause for suitable adjustment of the fragility rating or shall be cause for redesign at
12、 the option of the manu- facturer. 3.1 Sinificant resonances up to 55 cps shall form a part of the rating or shall be the resonant element(s) subject to redesin at the option of the manufac- turer. 3.5 It is the intent +hat the ratin rnunbers be stated at the nearest practical point above which dama
13、ge will occur and without introduction of safety factors. 3.6 It is recognized that test equipment may not be available for testing in the reion of 2 to 10 cycles per second. Important resonances in this region may be determined by such other pYsical or mathematical measurement means as may prove pr
14、actical. 1. REPORTING AND RECnRDING dF FRAGILITY DATA: 4n request of authorized persons or agencis, rag lity rat g n ormation s ould be reported in the form shown in Fi gure I. EQUI11IVP FRAGILITY DATA lu 3-1-56 467 ttrisea -3- FGUFtE I FRAGILTTY RAZTNG DEVIANT SHE.P 1. M rs Name an Ad ess. 2. r s I
15、 ent icatian iun ers. 3.Mfrs Nomenclature. I. Category - if norma nomenc ature is not escrip ive, p ease amp i. 5. Mil. Type or Designation. Mi . Spec. No. 6. Length: jdidth: Height; yleight lbs.: nensions: neares simp e geome ric proecion, inc es ?. Test c. No.: Method= No. of Shocks: Speci ieSh-oc
16、k Test ata Max. Number of rrrSn; Millisec. Duration; Remarks: includin number and direction of shock. 8. Test Spec. No.s Method: Duration: Specfied ibration est Data Max. number of gs: Freq., cps: DPL Amplitude: In. Remarks: 9. Max. recommen e mun er of g s ase on engineering es a a. 10. Natural Fre
17、uencies in the Assembled Equipment Between 2 or 15 and 55 cps F.esonatin Element: Frequency Estimated: Frequency Verified: 11. Fragility Rating Estimate or Ver ie state which Note: If the manufacturer is unable to complete the questionnaire above, give an estitnated fragility rating on the item base
18、d on test and field ser- vice experience. EXAMPIE OF FRAGILITY RATING: 25 - 3/55 eanin; g m-ax. recormnendeci shock with components resonating at 30 and cycles per second. If no resonant frequency ex sts below 55 cps and fra.ility rating should be expressed in the form 2- 55+. #See Paragraph 3.6. PREPARED BY COPfiIITTEE S-8, AIRCRAFT EQUIPMENT SHOCK & VIB?TIOi ISOLATION
