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<£. NPS-MA-94-008 NAVALPOSTGRADUATE SCHOOL Monterey, California STRESSES IN SHIP PLATING by D.A. Danielson C.R. Steele F. Fakhroo A.S. Cricelli Technical Report for Period October 1993 - December 1994 Approved for public release; distribution is unlimited Prepared for: Naval Postgraduate School Monterey, CA 93943 FedDocs D 208.1M/2 NPS-MA-94-008 Fe I ; DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY CA 93943-5101 NAVAL POSTGRADUATE SCHOOL MONTEREY, CA 93943 Rear Admiral T.A. Mercer Harrison Shull Superintendent Provost This report was prepared in conjunction with research conducted for the Naval Postgraduate School and funded by the Naval Surface Warfare Center (Carderock Division) and by the Naval Postgraduate School. Reproduction of all or part of this report is authorized. This report was prepared by: FNCLASSIFIED SECURITY CLASSiF'CATiQN Of THIS PAGE REPORT DOCUMENTATION PAGE FormApproved OMBNo 0704-0188 la REPORT SECURITY CLASSIFICATION lb RESTRICTIVE MARKINGS UnHa.ssi fipA 2a SECURITY CLASSIFICATION AUTHORITY 3 DISTRIBUTION/AVAILA3ILITY OF REPORT Approved for public release: 2b DECLASSIFICATION/DOWNGRADING SCHEDULE distribution unlimited 4 PERFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NuMBER(S) NPS-MA-94-008 NPS-MA-94-008 6a NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a NAME OF MONITORING ORGANlZAT ON (If applicable) Naval Surface Warfare Center (Carderock Div, Naval Postgraduate School MA Naval Postgraduate School Research Program 6c. ADDRESS {City, State, and ZIPCode) 7b ADDRESS(City, State and ZIPCode) Naval Surface Warfare Center Monterey, CA 93943 Carderock Division Bethesda, MD 20084-5000 8a. NAME OF FUNDING/SPONSORING 8b OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (If applicable) Naval Postgraduate School MA 0M,N 8c. ADDRESS(City. State, and ZIPCode) I0 SOURCE OF FUNDING NUM8ERS PROGRAM PROJECT TASK WORK-UNIT Monterey, CA 93943 ELEMENT NO NO NO ACCESSION NO 11 TITLE (Include Security Classification) Stresses in Ship Plating 12 PERSONAL AUTHOR(S) D. A. Danielson, C. R. Steele, F. Fakhroo, A. S. Cricelli 13a TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT (Year, Month, Day) 15 PAGE COUNT Technical Report from 10/93 to 12/94 December, 1994 69 16 SUPPLEMENTARY NOTATION 17 COSATI CODES 18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP Stresses in Ship Plating 19 ABSTRACT {Continue on reverse if necessary and identify by block number) The subject of this paper is the mechanical behavior of rectangular plates subjected to a combination of axial compression and lateral pressure. Displacements and stresses are obtained from a Fortran code based on the von Karman plate equations. The effects of various boundary conditions, nonlinearities, and imperfections are included. 20 DISTRIBUTION/AVAILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION 13UNCLASSIFIED/UNLIMITED \3 SAME AS RPT DTlC USERS Unclassified 22a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (Include AreaCode) 22c OFFICE SYMBOL Donald Danielson 408-656-2622 MA/Dd DO Form 1473, JUN 86 Previouseditionsareobsolete SECURITY CLASSIFICATION OF THIS PAGE S/N 0102-LF-014-6603 UNCLASSIFIED STRESSES IN SHIP PLATING D. A. Danielson C. R. Steele F. Fahroo Division of Applied Mechanics A. S. Cricelli Stanford University CA Department of Mathematics Stanford, 94305 Naval Postgraduate School CA Monterey, 93943 December, 1994 ABSTRACT The subject of this paper is the mechanical behavior of rectangular plates subjected to a combination of axial compression and lateral pressure. Displacements and stresses are obtained from a Fortran code based on the von Karman plate equations. The effects of various boundary conditions, nonlinearities, and imperfections are included. INTRODUCTION Fatigue life predictions require knowledge of the stresses in a ship under its operating conditions [Sikora, Dinsenbacher, and Beach (1983)]. Stiffened plates are a basic structural component of ships and submarines. The mathematical equations governing the deformation of thin elastic plates and methods for solution of these equations are well-known [Timoshenko and Woinowsky-Krieger (1959), Szilard (1974), and Hughes (1983)]. The objective of our work is to use these known mathematical methods to predict the stresses in typical ship plating. Plates are subjected to axial tension and compression from longitudinal bending of a ship due to wave loads. In addition, plates on the bottom are subjected to lateral water pressure.' Deck plating boundary conditions may be taken to be simply-supported whereas bottom , plating boundary conditions are more closely approximated as clamped. Deck plating may be considered to have an initial geometric imperfection, whereas bottom plating is bowed in by the water pressure. We consider a rectangular plate with length a, width b, and thickness t. The structure is subjected to axial force F, and possibly uniform lateral pressure p (force per unit lateral area of the plate). ) PLATE EQUATIONS The basic differential equations of nonlinear shallow shell theory are D V4 w = P + $<yy (too + w)ixx +$,xx (tu + w),yy -2 $,ry (w + ^),xy ( 1 tt V4 $ = [(u>o + u;)4y -(u; + u>),xx (ti) + w),yy ] - (u;jjxy -uw* u;o,w ) (2) Here (x,y, z) are Cartesian coordinates measured from the center of the plate. D — Et3/12(1 — i/2) is the bending stiffness, E is Young's modulus, and v is Poisson's ratio. wo(x,y) is the initial geometric imperfection of the plate midsurface in the z-direction, while w(.r,y) is the normal displacement. <J>(x,y) is the Airy stress function. Commas denote partial differentiation with respect to x or y; e.g, '. 84w d2w 4w V W - W,xxxx +2w,xxyy +W,yyyy - ^4 + -QX2Q 2 + Qy4 We let u(x,y) and t>(x,y) denote the displacements of the plate midsurface in the x and y directions, respectively. These in-plane displacements can be related to w and $ by using the strain-displacement relations € x = ulX +wQ,x w,x +\w,x2 txy = U,y+V,x +Wo,x W,y +^ ,y W,x +W,x W,y and the constitutive relations Et Nx = — M,x + VCy) \ V* Et Ny = — v-A{,ey + vex) 1 Et xy " + 1/)^ 2(1 The membrane stress resultants (forces per unit length of side) are related to the stress function by "Ni —— <^J>iyy j Ny —— $'3?x i *a"txy = —4^>rixy