ML20125D155
| ML20125D155 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 03/14/1980 |
| From: | Grove R, Chris Miller CBI SERVICES, INC. (FORMERLY CHICAGO BRIDGE & IRON |
| To: | |
| Shared Package | |
| ML20125D152 | List: |
| References | |
| NUDOCS 9212150029 | |
| Download: ML20125D155 (15) | |
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PUCKLING Or CYLI!JDRICAL SHELLS WITH REINFORCED l CIRCULAR OPE!11NGS UNDER AXIAL COMPRESSION l l by { Clarence D. Miller Director of Structural Recoarch and Robert B. Grove Research Engineer 4 Chicago Bridge & Iron Company-Plainfield, Illinois March 14, 1980 t t 0
. s se ban
'9212150029 921204-PDR ADOCK 03200003-A - - -
.PDR-
BUCY. LING OF CYLINDRICAL S!! ELLS UITil REINFORCED CIRCULAR OP!:NINGS UNDER AXI AL COMPRESSION ! By Clarence D. Miller l and Robert B. Grove 2 l ! INTRODUCTION Many buckling tests have been performed on cylindrical shells with unreinforced circular and rectangular openings (2, 3, 6, 7, 8) and several tests with reinforced rectangular openings (2, 4). Several numerical studies have also been made of shells'with the geometry and tYFe of reinforcement corresponding to the test shells (1, 2, 4) and one study has been made of ring and stringer stif fened shells with rectangular openings (5). None of these studies consider - the ef fect on buckling of openings that are reinforced by the area replacement rules of the ASME Code (9). Babcock (3) performed a series of tests which considered the extreme cases of circular opening with no reinforcement and with a rigid penetration. IIe also performed a set of tests with a flexible pene tra tion. None of the se tests were made on shells with reinforce-ment added along the cylinder wall. This method is often used for reinforcement of openings in containmen*. and other type pressure vessels. The present study was per formed to de termi ne the e f fect on buck-ling of addina reinforcement along the cylinder wall as well as aor-mal to the cylinder wall. The limits of reinforcement were deterrained in accordance with the ASME Code (9). "?ests ware performed on a 15 in. diameter cylinder with a 4 in, diameter ocening. The opening corresponds to a 30' central angle which is the largest opening that has been considered for a containz.ent vessel. I Director of Research and 2 Research Engineer, Chicago Bridge and Iron Company, Plainfield, Illinois 1
P i 4 NOTATIONS A = Cutout Area , A r
= Ef fective Area of Reinforcement E = Modulus of Elasticity of the Material L = Unsupported Length of Cylinder P = Failure Load P
CL
= Classical Buckling Load, 0.605E(t/R) 2'Rt w
= Failure Load for Cylinder Without Cutout P,
R- = Centerline Radius of Cylinder , r = Cutout Radius
. i r = Centerline Radius of Nozzle n
t = Cylinder Wall Thickness t,
= Reinforcing Pad Thickness t
n
= N zzle Wall Thickness P
f i 1-A-
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,. EXPERIMENTAL PROGRAM ,
The experimental work was conducted on a cylinder made from mylar. This material was selected because the test cylinder could be buckled many times without permanent damage and still provide reproducible results. The stress-strain curve remains linear for ; stresses well above the buckling stresses of the test cylinders. The loading considered in these tests was uniform axial compression. The test shell was constructed from a flat sheet o,f mylar cut to the appropriate size. The ends were secured in steel clamping rings used on previous tests on steel cylinders (10). The test shell was fitted into, the bottom clamping ring. The upper clamping ring was then installed and aligned to make the two clamping rings parallel. Af ter alignment, the mylar sheet was se-cured to the clamping rings. The use of clamping rings resulted in a cylinder with larger imperfections than was found on similar shells with the ends secured to the end plates with a low melting tempera-ture alloy. The buckling capacity of the shell is, however, more representative of a fabricated shell. The cylinder wa.s completed by making a butt joint with both sides reinforced by 1.0 in. wide mylar strips attached with Scotch brand double stick tape. The re- - sulting cylinder was 15.0 in. inside - diamter, 0.0132 in. wall thick-ness, and 15.0 in, clear span between clamping rings. The modulus of elasticity was determined in accordance with ASTM D88L-75b and found to be 650,000 psi. The stress-s train curve is shown in Fig. 1. Poisson's ratio was assumed to be equal to 0.3. The cylinder was - tested on a 120,000 lb. Tinius-Olsen " Electro-matic Universal Testing Machine". The machine is equipped with a swivel head attachment that allows the load to be applied without any eccentricity. A 16 inch diameter steel block 'was attached to the swivel head which transmits the load to the upper clamping ring. The test apparatus can be seen in the various figures of the failed test cylinder. The cylinder was first tested without any cutout. A 4 in. diam-eter cutout was then made and the cylinder re-tested.- Successive tests were made by attaching 0.25 in, wide x 0.0132 thickness ' rein-forcing pads around the cutout with Scotch brand double stick tape 2 n q---- -c.-. e e y agr e +v a ,*.wip yw p-m~3-ee .-,,,..g --p.9m y-.7
to replace the cutout area. A cecond series of tests were made using one reinforcing pad and adding reinforcement in the form of a nozzle penetration. The first nozzle thickness was attached to the cylinder shell and reinforcing pad with Scotch-Weld structural adhesive 2216 B/A gray. Successive layers of nozzle wall thickness were attached using Scotch Brand double stick tape. The ef fective area of rein-forcement was determined in accordance with the ASME Code (9). For limits of reinforcement for test cylinder sco Fig. 2. The geometry of. t.he' cylinder and reinforcement is shown in Fig. 3. e
=
8 %' 3
EXPERIMENTAL RESULTS The results of the present tests are given in Table 1. Tests by others (3, 6, 8) show that the buckling capacity of a cylindrical shell with an unreinforced cutout is a_ function of the parameter y = r//Rt. A plot of this data is shown in Fig. 4. Tests lA where y = 0 and 1B where y = 6.36 are also shown in Fig. 4. Test 1A- failed at 29% of the classical buckling value compared to a range of 60 - 97% for other investigators. The lower buckling value of 1A is due to larger initial imperfections and dif ferent-end restraint conditions. The proposed ASME Appendix for design of containment vessels (11) gives a value of P/PCL = 0.22 for a fabri-cated steel shell. The tests by Starnes (6, 7) show that P/P CL falls in a range of 0.20 - 0.30 for y = 6.36. Test 1B failed at P/PCL = 0.22 which is within the range of the tests by Starnes. The effect of replacing the cutout area is demonstrated in Fig. 5 where P/Pg is plotted vs. A r/A. It is interesting to note that adding reinforcement to the cylinder wall was more ef ficient than adding it to the penetration wall. A value of P/P = 0.9 was obtained at a value of Ar /A = 0.4 for either type of reinforcement. There was no appreciable increase in the buckling load _for values of Ar /A '
-0.40 - 0.77 when added to the penetration wall. When additional area was added to the cylinder wall che buckling capacity continued to increase until_P/P = 1.0 at a value of A r/A = 0.86. Tests by Babcock - (3) , who used a rigid plug which more than replaced the cutout area, showed a maximum value of P/Pg = 0.95. The tests on cylinders with rectangular openings (2) compare favorably with those on cylin-ders with circular openings.
Several photographs of buchied cylinders are shown in Fig. 6. The -failure patterns were very nearly the same for all tests. Away from the opening the buckling ' pattern was identical to that of the shell without a cutout. 4 y p- .iews- -- rrne ip-y- w- e c'w +-u-*p _a.meew-w' M wm s wr's _a A - v-- a------------8--- - - - - - - '"'
i
, r CONCLUSIONS If a cutout in a cylinder loaded by axial compression is small I
enough initial imperfections and end restraint conditions will govern I the buckling load. As the cutout size increases, the ef fects of the cutout become greater than that of the initial imperfections and end restraint conditions. Tests by Starnes (6, 7) show that the buck-ling load of the cylinder is reduced when y > 0.5. Only a value of y = 6. 36 was inve s tiga ted in the present study. The buckling value of the unreinforced opening was 22% of the clas-sical buckling load. This value is within the scatter band of tests by S ta rne s . The buckling capacity of a cylinder with a cutout can be in- , creased .by adding reinforcement. By replacing 40% of the cutout area the buckling capacity was increased to 90% of the value of the cylinder without a cutout. By adding 86% of the cutout area to the cylinder wall the buckling capacity was equal to that of the cylin-der without a cutout. There was no appreciable increase in the buck-- ling capacity for values of Ar /A > 0.4 when the reinforcement was added to the penetration wall. l The penetration wall was attached with material having greater . flexibility than the penetration and shell material. possibly the effective penetration area was not fully developed. The buckling patterns of the cylinders away from the opening were the same for all tests and corresponded to that of the cylinder A without an opening. l I e 5
.. . - . - - _ -- - .-- - _ . . - - _ _ _ - . - - . - .. . .~
REFERENCES - 1. Almro th , B .O . , Brogran , F . A . , and Morlowe , M. D. , "S tabili ty Analysis of cylinders with Circular Cutouts," AI AA J. , 11:11, November, 1973, pp. 1582-1584.
- 2. Almroth , B .O . and Holmes, A.M.C., " Buckling of Shells with Cut-outs, Experiment and Analysis," Intern. J. Solids Structures, Vol. 8, 1972, pp. 1057-1071.
- 3. Seide, P. , Weingar ten , V . I . , and Masri, S .P. , " Buckling Criteria and Application of Criteria to Design of a Steel Containment Shell," International Structural Engineers, Glendale , Calif. ,
March 1979, Appendix A. .
- 4. Brogan, F. A. and Almroth , B .O . , " Buckling of Cylinder with Cutouts," AIAA J., 8:2, February 1970, pp. 236-240,
- 5. Palazotto, A.N., " Bifurcation and Collapse Analysis of Stringer and Ring-Stringer Stif fened Cylindrical Shells with Cutouts,"
Computers & Structures , Vol. 7, 1977, pp. 47-58.
- 6. Starnes, J.H., "The Ef fects of Cutouts in the Buckling of Thin Shells," in Thin-Shell Structures , Theory, Experiment and Design, edited by Y.C. Fung and E.E. Sechler, Prentice-Hall, Inc.,
Englewood Cliffs, N.J., 1974, pp. 289-304.
- 7. Starnes, J.H., "Effect of a Circular Hole on the Buckling of Cylindrical Shells Loaded by Axial Compression," AIAA J., 10:11, November 19 72, pp. 14 6 6-14 7 2.
- 8. Tennyson, R.C., "The Ef fect of Unreinforced Circular Cutouts on the Buckling of Circular cylindrical Shells under Axial Compression," J. Eng. Ind., Vol. 90, 1968, pp. 541-546.
- 9. ASME Boiler and Pressure Vessel Code, Section III, " Nuclear Power Plant Components," I Div{s. ion 1, Subsection NE, Class MC Components , NEP$tS$7 Edi tio n , fpf-6-8-fr8-2-"
- 10. Miller, g ly Compressed Cylin-
.D Q u g g.Ax,i ders," WPrcpri. t c_ 'p" Dra seate?. O t ASCE Otruc. I;uvSr. ,
M;14Lscr., ' i m AugurL2 2-25, 1926. Vd I N ) 8'
) W /7 7 7).
p . s w /rzt. 6
s fl. " Metal Containment Shell Buckling Design Methods," preyM nonmaEdster M ppamiin-for ASME Boiler and Pron _ure Vessel CodeM /
, November---,v- --- - _vv
-Section III, Division J jq g6 '
h W484 3 4 2. / e 11F 6 l 7 l l l
e TABLE 1 -
SUMMARY
OF TEST RESULTS TEST t t P/PCL P/P o e n ^r/A 1A 11 0 llOLE -
.292 1.000 in 0 0 0 .223 .764 1C .0134 0 .125 .252 .863 1D .0267 0 .250 .258 .884 1E .0400 0 .374 .264 .90'4 1F .0533 0 .499 .273 .935 1G .0663 0 .6,20 .275 .942 1 11 .0794 0 . 74 3 .284 .973 II .0926 7I~ 0 .866 .300 1.027 IJ .1059 7" 0 .990 .301 1.031
- r
.0134 .125 qdf 1x 0 .237 .812 IL-A .0134 .0125 .205 .223 .764 "/
/
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