1、.FOR AERONAUTICS1 u N(IV IY4/TECHNICAL NOTENo. 1482 .-.-. ,A METHOD OF CALCULATING THE COMPRESSIVESTRENGTK OF Z-STIFFENED PANELSTHAT DEVELOP LOCAL INSTABILITYBy George L. Gallaher and Rolls BCALCUMTIOti OF T13EOIlRTICALELk+C,.CTICAL iOMFNESSIVX ST!KZWS, ,. . . ,dependent upon.,The”th:”(,l),. ., cr .
2、 .,12”(1.,-+l?)b2”-“ “ .“ .: “ .-:Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.NACA TN Ne. lk82 . “3,.fi *MS formula t and b are the thtckness and the width,respectively, of the plate under oonsideration E is Young*sdtius; v is Poisson?sratio; an
3、d k ig a,oopfftcient”thatis detemnined ti,omthe relativa proportions of thecross section.The sam equation maybe adapted to plato assczublios.As appliedwhere the subsoript S “refersto the skin or thestiffeners. ,.With equatfoti(2) tk elastic valw ,ofacr.-.”, (2)platebetween the,mm %e aticatedfor titf
4、fened pinreference 6“f,or i, %,and C-section plate assemblies. The,use O? the secnt”mgdulusfor.%he bucklfng of plates has dso.bcenpropadhyrmd inreferehoe 7. The test data indicate that the use of, Esec in - -.equation (2 will.give values that are slifjxtlyWconseryativeabove the elastic rsnge. 14hent
5、he averk str6i8-straince wasused, the amount of UnconservakTsmwaa faund to vary from 0.2 percen$.to 10,5 percent,and to average out 6 percen,. ,t!em$.!O_ducethe scatterby,referri.eoh tostpoint to its individual.stress- .strain curve showed only a little impfiuvement.This result wasProvided by IHSNot
6、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-.NACA TN No. lk82 5.probably due largely to the difficulty in obtaining a ood repre-sentati% stress+ train curve for each specimen because of thevariation in properties caused by fomning and by the use ofdifferent sheet
7、material in the skin and stiffeners.When buckling occurred,at high stresses,values of the averageh“ss at maximum load Vmx were found to be only slightly geater -than acr. These Fm valusehavebeen included in ftgurq 4 toshow the close agreement between” dcr !Cfcy,the plate IIuckkhg equation with Efiec
8、 substituted for Ecan also be used to calculate approximate values of mx in thisregion, (Thismethod has been suggested previously for H-, Z-, andC-section plate asseribliesin reference 6.)CONCLUSIONS.The following conclusions are based upon thetest results for 24E+T aluluinloy Z-stiffenedformed stif
9、feners strongly riveted *O the skin:1. The critical compressive stress for locallocal instabilitypanels havinginstabilitymaybe calculated from the plate buckling equation with the secsntmodulus substitutedfor Youngs modit.us. This fommla iskS#E=eJ#cCr =12(1 -v2)bS2where kS is the buckling stress coe
10、fficient; t snd bS arethe thiclmess end width of the skin plate, respectively; v isProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 NACA NO. 14%2PoissonSb ratio; tid Eec is the secant modulus. The resultsobtainedby the use of this fozmwla are reason
11、ably accurate withinthe elastic range but tqnd to be on the.average about 6 percentunconsorvative above the elastW rerge.2. The values ofthe avere streasat maximum loiaiiabovethree-fourths the yield stress are just slightly greater than thebuckling stresses. An approximatevalue of.the averae compres
12、sivestress at maximum load, cr2nsequly, can also %0 calculated fromthe previous formula when this stress is above three-fourthstheyield stress, ,“.-W *mrid Aeronautioal Laboratory .National AflvlsoryCommittae for AeronauticsLangley Field, Va., Aug. 5, 1947,.,.-.,.Provided by IHSNot for ResaleNo repr
13、oduction or networking permitted without license from IHS-,-,-.NACA TN NO a71 1482 RIWEREWCES1. Boughan, RoUa B., and B.0#” 3.422 49533.55 d ;g 3.787 3: 2.377 b.435 4.420 G 4.229.w 2*785 2.357 G s Cg 4oo.80 2,1d.7 l.- 1.338 4.061 3.905 ;.2.90 1.683 1.431 1.057 3.639 3.3161.00 1.364 1.158 .857 3.094
14、2e743 2:095=;63 %a71 = 1.OOs s0.30 4.473 s.236 3.2kk 5.264 4.346 5.075 5.090 5.098g = 4.305. .% 4.267 4.256 4230l“la *9 4.* 4.970.55 .60 4.154 4.124 ;:% z z s.70 3.9i5 3.63I 4.769 4.751 4.723.80 3.259 2.812 :1oo k.626 4.594 4.460.90 2.595 2.232 4.416 4.340 3.9101.00 2.lu 1.807 1:352 4.106 3.925 3.25
15、1. .-?TA!rIoHALADVTSORYccmmTER mm AEFmvAwlws,?.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN No. 1482789%0m%?%3hbB15YL6%019%0%1%223Zb252427282993.320.4.4.4A.5.0.3.3.3.4.4.4.h.4.4.b. :.4.4.4.k.b.4.4A.JLA“AA.5.9D.-J.375Au?.U9AC+.h15Am.353.357
16、.357.377.35.5.33.W.M5.314.m.379.*7.725.V1.002.-.359.UTIb.1 xlk.17 25.G73.9 35.201.W 25.074.25 3b.914.17 3k.2kk.39k.304.37k.334.324.334.334.33b.3gL39k.39k.39k.39b.b.kk.khk.28k.4b4.374.373.203.403.521.*4.354.404.3035.433.52yxo.s$:23:?0.3935.9935.%:;:Z36.o339.*u.3k25.0550.k350.13W(.lk27.6335X$36.8126.C
17、5.36.13$.n6%mla9-063t.s0.00316.-.W.CQ432:%.IMa.03424.00308.oo313.C0309.00306.-.=n*.wls.fl.00440.-.CC%?35.-7.00!%3.00305.ocQ8940.044.023.5.o30.429.629.823.616.k36.1;.36.530.730.132.332.13.1.12-7.525.9Jk2.2%5.516.317.835.32i.3au2k.k7.129.729.7bl.2%29.331.43.332.033.126.13J3:38.635.033.936.336.935.033.
18、233.543A2a.o25.826.936.327.824.929.417.733.532.53063P63/163/163P69.- X.ainal ratio (n . 0.09+.5TABIE 2 - Conollxkl- Mm - Ccmoladedkfi%. 2)1 I t ().*.340.*Z ;?%25:42 64626.92 725%!.2627317?.88 606535.201239W.1O 251035.14123535.45I-257b9.7524T574.96*919.114.439.117.617.9:f!l.li 8.1-I.001 9.2CKtcXJ3033
19、5 1.6.Oe 9.5.000848.6mninal X73tlo(Wlinkl = 0.064In.forallUnpubliaheildata.NATmNAIi ADvIsmYCCSWHTEE FCiR AEROHMICICS17 Rimt RlwtmX pitoh di-tuz(IMi) (in.) (in.)27.829.239.729.726.929.122.51 5/325/327j8 3/161 5/321 5/321 5/321 5/3229.6 3/424.23/4:; ;$31.0 3/425.8 3/436.1 3/432.o 3/435.3 3/4:%! jl25.5
20、 3/41. ptlram).1/81/8Ia5/321/81/8;$:1/81/81/81/8.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN No. 1482 11.(a) Test panel.It(b) dealized panel.NATIONAL ADVISORYCOMMITTEE FOR AERONAUTICS.Figure L Gross section a d dimensions ofZ-stiffened pa
21、nels.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-12 NACA TN No. 148265432Iot.79bF ,50 r% .31tNATIONAL ADVISORYCOMMtTTE FOR /iERONAUlCSo .2 .4 bw .6 .8 100q-(d f = 0.50 and 0.79.Figure 2. Values of k for a uiformly loaded idealizedw -1.0,compressi
22、on panel with Z-section stiffeners, t.*Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.TN No. 1482 13.NACA65.4k32Io-0.2COMMITTEE FOR AERONAUTICSI.6 .8 Lo4 bWFigureb= 0.63 and 1.0.2. Concluded.Provided by IHSNot for ResaleNo reproduction or networkin
23、g permitted without license from IHS-,-,-14 NACA TN No. 1482,a71(a) Rotation of the joints,I . 1_ _ .(b) Rotation plus deflection of the web-flangejoints,NATIONAL ADVISORYCOMMITTEE FOR AERONAUTICSFigure 3. Cases of local instability considered fora Z-stiffened panel,Provided by IHSNot for ResaleNo r
24、eproduction or networking permitted without license from IHS-,-,-NACA TN J)Jo. 1482 15.Stress,ksi50403020a71AMaximum stress-strain curveMinimumb stress-strain curveAverage stressat maximumload, &maX101 0.51 A xl I.63 0 b.79 AI.00 a75 , :0 0 .002 .004.006 .008Strain NATIONAL AOVISORY00MMITTSS FOR AER
25、ONAUTICSFigure 4. Comparison of local instability test results with compressivestress-strain curves for 24 S-T aluminum-alloy Z-stiffened panels.(Strain for Z-stiffened panels is calculated elastic critical compressivestrain, Ccr.)Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
