The report presents a review of the important contributions made to knowledge on the stability of elastic columns by experimentalists during the last 125 years. It demonstrates that while methods of dealing with the influence of imperfections on stability have been developed and great ingenuity has been expended in devising 'ideal' end restraints to compare with those theoretically described, end fixity is still a major practical difficulty. There is not a single paper, even an isolated...
Topics: DTIC Archive, Horton, W H, STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS, *AIRFRAMES,...
Studies were made to investigate the design capabilities of beryllium as a structural material and to derive and develop structural design curves and related data for efficient structural design with beryllium. The metal beryllium is believed to have high potential for aerospace structures, but is not extensively considered in design applications because of uncertainties as to the proper design procedures. This report presents information based on studies and tests which clearly shows that...
Topics: DTIC Archive, Crawford, Robert F, LOCKHEED MISSILES AND SPACE CO INC SUNNYVALE CA, *BERYLLIUM,...
This study deals with both analytical and experimental investigations of sandwich beams with cores of polyurethane foam and facings of unidirectional cord-rubber, which is bimodular (i.e., having drastically different behavoir in compression as compared to tension). This work is believed to be the first devoted to vibration of bimodular mateials in a sandwich configuration. Two different analyses are presented: one is a sandwich version of the well-known Timoshenko beam theory, which results in...
Topics: DTIC Archive, Bert,Charles W, OKLAHOMA UNIV NORMAN SCHOOL OF AEROSPACE MECHANICAL AND NUCLEAR...
Topics: DTIC Archive, LEE, GEORGE C, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB,...
Experimental evidence is presented which shows that the critical load for a compressed column can be approximated closely for a wide range of rotational end fixity conditions using a simple lateral load test of the structure. A series of tests was conducted on each of two columns over a range of rotational end fixity. Axial load vs. lateral deflection data was plotted according to the Southwell method for each end fixity condition. The results of these tests were compared to lateral...
Topics: DTIC Archive, Horton, Wilfred H, STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS,...
This report involves the investigation of the mechanical vibration damping characteristics of glass/epoxy and graphite/epoxy composite materials. The objective was to develop an analytical model which incorporates the frequency dependence of the vibration damping loss factor and to experimentally characterize the loss factor for frequencies up to 100 Hz. Numerous mathematical models have been proposed to determine the loss factor of composites, including micromechanical, macromechanical and...
Topics: DTIC Archive, Crane, Roger M, DAVID TAYLOR RESEARCH CENTER BETHESDA MD SHIP MATERIALS ENGINEERING...
This thesis models the effects in a fluid medium of a plane wave that has impinged upon a reinforced plate. The wave equation for pressure, and the equation of a thin plate combined with other equations are coupled at the interface between the fluid and the thin plate. The actual modeling is accomplished in a fortran computer program written to run on the Naval Postgraduate School's main frame computer. The program uses extensive finite differencing on a domain, assumed to be a small section of...
Topics: DTIC Archive, Kisiel, Thomas K, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *COMPUTER PROGRAMS,...
This study was an attempt to conceptualize, design, build, and test a constrained layer damping device that uses mechanical advantage for the purpose of increasing the damping of transient vibration of a five-bay planar truss. The aluminum truss was clamped to a fixed support and simulated a solar array. A conventional constrained layer treatment was designed, built, and tested to serve as a benchmark for comparison. For the conventional treatment, Plunkett and Lee's segmented constraining...
Topics: DTIC Archive, Scharpen, Mark A, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...
The aim of this report is to present a consistent theory for the deformation of a naturally curved and twisted anisotropic beam. The proposed formulation naturally extends the classical Saint-Venant approach to the case of curved and twisted anisotropic beams. The mathematical model developed under the assumption of span-wise uniform cross-section, curvature and twist, can take into account any kind of elastic coupling due to the material properties and the curved geometry. The consistency of...
Topics: DTIC Archive, Borri, Marco, POLITECNICO DI MILANO (ITALY) DIPT DI INGEGNERIA AEROSPAZIALE,...
A comparison between the maximum deflections resulting from beams symmetrically loaded into the elastic-plastic region is presented for the case of three and four point bending. The results indicate that significantly larger deflections can be obtained for the case of four point bending while keeping the maximum fiber strains approximately the same. It appears that using the four point bending approach holds certain advantages in straightening operations for the removal of permanent deflections...
Topics: DTIC Archive, Milligan, R V, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE...
A comparison between the maximum deflections resulting from beams symmetrically loaded into the elastic-plastic region is presented for the case of three and four point bending. The results indicate that significantly larger deflections can be obtained for the case of four point bending while keeping the maximum fiber strains approximately the same. It appears that using the four point bending approach holds certain advantages in straightening operations for the removal of permanent deflections...
Topics: DTIC Archive, Milligan, R V, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE...
This paper (Report no. 58) deals with the optimization of the shape of the corners and sides of a square hole, located in a large plate and subjected to in-plane loads, with the object of minimizing stress concentrations. Appreciable disagreement has been found between the results obtained previously by other investigators. In this paper new tests have been conducted and discrepancies have been corrected. Using an optimization technique, the authors have developed a quasi square shape which...
Topics: DTIC Archive, Durelli,A J, MARYLAND UNIV COLLEGE PARK SCHOOL OF ENGINEERING, *Stress analysis,...
The ability to predict torsional instability in the early stages of design can have important consequences on the design of both conventional and high performance ships. This thesis develops fast approximate methods of torsional buckling analysis for particular application in the concept, feasibility, and preliminary stages of ship design. Two simplified models of stiffeners commonly used in ship construction were presented. The first was an ideal I section stiffener. The second, a flat bar...
Topics: DTIC Archive, Coulter,S L, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING,...
Volume I of this report (1) presents the findings of a study conducted to develop a low-density polyurethane foam system that is deployable within 5 seconds, and (2) documents a study of foam/fabric cylinders as potential structural members. An especially fast-reacting foam formulation was devised, hardware for delivery and mixing of foam chemicals was designed and evaluated, various geometric shapes of constant volume that the foam could be formed into were invesigated, and the impact loading...
Topics: DTIC Archive, Smith, Alvin, CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL,...
This paper reports an investigation of the dynamic behavior of a pin- ended inelastic column subjected to a half-sine displacement pulse at one end applied with small eccentricity. It is shown that an inelastic column, like the elastic column, can support dynamic loads considerably in excess of the static load capacity. It is also shown that within the range of pulse durations studied, the smallest residual deflections generally accompany the largest maximum loads.
Topics: DTIC Archive, Defibaugh, Jr, Carl F, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *BEAMS(STRUCTURAL),...
The vibration characteristics of integrally stiffened skin-stringer panels have been investigated theoretically and experimentally. This type of structure was found to have mode shapes similar to those of flat plates due to the relatively low values of stringer bending stiffness. The experimental measurements were made by means of strain gauges and accelerometers, with the typical panel excited acoustically by travelling waves at approximately grazing incidence. Methods of damping the resonant...
Topics: DTIC Archive, Cicci, Fernando, SOUTHAMPTON UNIV (UNITED KINGDOM) INST OF SOUND AND VIBRATION...
Incipient collapse deflection data and an analysis method, reported in Phase I of this study, were used to propose an incipient collapse deflection criteria for one-way and two-way slabs. A relationship for the incipient collapse deflection of slabs, when tensile membrane action can be developed, is given in terms of the short span and steel rupture strains. Structural design details, to insure that membrane action can be developed, are discussed and experimental verification tests are...
Topics: DTIC Archive, Takayanagi,Takehira, CONSTRUCTION TECHNOLOGY LABS SKOKIE IL, *STRUCTURAL COMPONENTS,...
Procedures are developed for constructing asymptotic solutions for certain nonlinear singularly-perturbed vector two-point boundary value problems having boundary layers at one or both end points. The asymptotic approximations are generated numerically and can either be used as is or to furnish a two-point boundary value code (e.g. COLSYS) with an initial approximation and a nonuniform computational mesh. The procedures are applied to several examples involving the deformation of nonlinear...
Topics: DTIC Archive, Flaherty,Joseph E, ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMAND WATERVLIET NY LARGE...
Compacts of boron carbide powders with specific surface area = or 8 sq m/g were sintered in argon at temperatures near 2200 C. Several of these powders were prepared by attrition milling of abrasive grade boron carbide. Densification to 95+% of theoretical denstiy could be obtained only with compositions that had appropriate amounts of excess carbon. The microstructures were fined grained and uniform but underwent abnormal grain growth above 2235 C accompanied by transgranular microcracking....
Topics: DTIC Archive, Prochazka,S, GENERAL ELECTRIC CORPORATE RESEARCH AND DEVELOPMENT SCHENECTADY NY,...
Studies have shown that fiber-reinforced polymer (FRP) wraps can improve the capacity of rectangular beam sections. This technology has potential application to highway bridges that may have less shear capacity than flexural capacity or require added load capacity to handle current traffic demands. Compared with steel repair materials FRP offers several benefits, such as corrosion resistance and field-workability. Several studies have investigated the use of externally bonded FRP sheets to...
Topics: DTIC Archive, Brady, Pamalee A., CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL,...
Partial contents: Improvement to Shaikh's for torsional vibration analysis of branched systems; Study of Guyan reduction of two degree of freedom systems; A method for estimating the error induced by the Guyan reduction; Critical speeds of multi-throw crankshafts using spatial line element method; Parametric study of the Irbrahim time domain modal identification algorithm; effective dynamic reanalysis of large structures; Effect of stiffener arrangement on Random response of a flat panel;...
Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC SHOCK AND VIBRATION INFORMATION CENTER,...
The 1991 Active Materials and Adaptive Structures Conference was held to address the explosion in both theory and application of recent and ongoing developments in smart, intelligent, or adaptive structures. The many areas of intelligent systems and smart structures incorporating active materials are now emerging to include major areas of research and development. These include fiber-optic based devices; ferroelectric, shape memory, and electro-rheological- based sensors and actuators; hybrid...
Topics: DTIC Archive, Knowles, Gareth J, INSTITUTE OF PHYSICS LONDON (UNITED KINGDOM), *FIBER OPTICS,...
This report contains the Second International conference proceedings on Recent Advances in Structural Dynamics held 9-13 April 1984 at the Institute of sound and Vibration Research, The University of Southhampton, England. (Author)
Topics: DTIC Archive, Petyt,M, SOUTHAMPTON UNIV (ENGLAND) INST OF SOUND AND VIBRATION RESEARCH, *VIBRATION,...
Session topics in this volume include: Vibration suppression; Free layer damping; Laminates; Launching; Model verification; Metals; Sandwich construction; Impact damping; Space applications. Keywords: Vibration detectors; Structural control; Structural components; Damping materials; Structural beams; Viscoelasticity; Space systems; Passive vibration control; Spacecraft components; Flexible structures; Mathematical models; Viscous damping; Aluminum indium alloys; Composite materials;...
Topics: DTIC Archive, WRIGHT RESEARCH AND DEVELOPMENT CENTER WRIGHT-PATTERSON AFB OH, *COMPOSITE MATERIALS,...
This study investigates the failure modes, failure strengths and failure criteria of laminated composite plates with stress concentration and subjected to bending loading. Graphite/epoxy composites are used for the present study. Lamina material properties, such as stiffness and strength, of the composite are obtained by experiments. A series of bending tests are conducted for laminated, graphite/epoxy composite plate with and without a hole to investigate their failure modes and strengths. In...
Topics: DTIC Archive, Yang, Shih-Ting, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *COMPOSITE MATERIALS,...
A frequency domain theory for structural dynamic model error localization is applied to the damage detection problem. The localization theory is based on a transformation of the frequency response function matrix, and represents an exact solution for the location of the differences between two frequency response function models, given spatially complete data. The localization is performed at all frequencies in a chosen bandwidth, and therefore implicitly accounts for all modes of interest....
Topics: DTIC Archive, Campbell, Marvin G., NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *BEAMS(STRUCTURAL),...
Topics: DTIC Archive, Lay, M G, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB, *BEAMS(STRUCTURAL),...
A method is developed to produce a design curve for predicting the response of a given type of structure to impact loading. This curve gives the maximum strain in the structure, which may have various size and material properties, due to impacts involving different masses and velocities. An example of a simply supported beam under central impact is presented in detail. Both experimental results and numerical calculations were used in establishing the design curve. This curve implies that, for...
Topics: DTIC Archive, Chou,Pei Chi, Flis,William J, DREXEL UNIV PHILADELPHIA PA, *IMPACT, *LOADS(FORCES),...
A smart beam with embedded sensors and actuators was analyzed and tested. The smart beam studied was constructed from graphite and epoxy with piezoceramic actuators and NiTiNOL sensors embedded. It was mounted vertically and subjected to transverse dynamic loading at the free end. Analytic expressions for the open loop and closed loop response (using strain rate feedback control) of the beam (including internal damping) to external forcing were derived in detail. Experimental testing of the...
Topics: DTIC Archive, Hoffman, Terance J, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...
A procedure is developed for generating variational statements suitable for obtaining approximate solutions to boundary-initial value problems. The essence of the procedure is to introduce all boundary and initial conditions into the variational statement as natural boundary conditions. This is accomplished through the use of Lagrange multipliers in which all initial condition terms as well as boundary terms are determined analytically. The result is a variational statement in which completely...
Topics: DTIC Archive, Simkins, T E, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE...
This article examines the dynamic plastic response of an impulsively loaded ideal fibre-reinforced (strongly anisotropic) rigid-plastic beam. It is demonstrated that the response duration and permanent transverse displacements are significantly less than the corresponding quantities in an equivalent rigid perfectly plastic isotropic beam. (Author)
Topics: DTIC Archive, Laudiero,F, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING,...
The finite element solution formulation in time- and space- coordinates is extended to beam vibrations effected by a moving couple. This problem has direct application to gun motions analysis with an unbalanced moving projectile. The moving load, instead of being a time-dependent Dirac delta function as for the case of a moving concentrated force, is now the derivative of this Dirac delta function. This singular function does not present any difficulty due to the variational process employed....
Topics: DTIC Archive, Wu, J J, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER...
The finite element solution formulation in time- and space- coordinates is extended to beam vibrations effected by a moving couple. This problem has direct application to gun motions analysis with an unbalanced moving projectile. The moving load, instead of being a time-dependent Dirac delta function as for the case of a moving concentrated force, is now the derivative of this Dirac delta function. This singular function does not present any difficulty due to the variational process employed....
Topics: DTIC Archive, Wu, J J, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER...
The finite element solution formulation in time- and space- coordinates is extended to beam vibrations effected by a moving couple. This problem has direct application to gun motions analysis with an unbalanced moving projectile. The moving load, instead of being a time-dependent Dirac delta function as for the case of a moving concentrated force, is now the derivative of this Dirac delta function. This singular function does not present any difficulty due to the variational process employed....
Topics: DTIC Archive, Wu, J J, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER...
A series of simple theoretical models are discussed, representing the essential features of flexible aircraft both of the classical and integrated varieties, in trimmed level flight. Assuming linear aerodynamics it is shown that the maximum speed for trimmed flight for the classical aircraft is determined primarily by the tail-plane flexibility. For the integrated aircraft this maximum speed occurs when both the overall aeroelastic distortion and the control forces become very large, the...
Topics: DTIC Archive, Hancock, G J, ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS...
This SERDP SEED Project was focused on extending the applicability of the NRL-developed structural acoustic fault monitoring technique using laser measured surface vibration to the materials and fabrics associated with historic buildings. In this regard, flexural wave inversion was successfully demonstrated numerically on thin plates of plaster, steel, and concrete and on thick plaster and steel plates with flaws at different depths. A new orthotropic inversion algorithm was developed and...
Topics: DTIC Archive, SET INC LOWELLVILLE OH, *LASERS, *STRUCTURAL INTEGRITY, *VIBRATION, ALGORITHMS,...
The higher modal dynamic plastic response of fully clamped beams has been examined using various rigid perfectly plastic theoretical procedures and a numerical elastic-plastic computer code. The theoretical predictions agree reasonably well with the corresponding experimental values on strain rate insensitive beams which were subjected to first and second modal initial velocity distributions. However, all the experimental results for the third mode case lie below the various theoretical methods...
Topics: DTIC Archive, Jones,Norman, Soares,C A P Guedes, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN...
For the moments of a function of jointly distributed random variables, an approximate solution is derived that does not require an explicit closed form expression for the derivatives of the function. The solution is based on a linear approximation of the implicit functional relation. This technique is applied to the resistance of a reinforced concrete member subjected to combined bending and thrust, and the results are compared with those obtained from Monte Carlo simulations. The variability...
Topics: DTIC Archive, Mlakar,Paul F, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS,...
A finite element model of a two-for-one tactical shelter is presented. The model is compatible with the COSMIC*NASTRAN finite element program. Both beam and composite plate elements are used in the model. The geometric properties of the beams are given in tables. The shelter's response to racking loads is calculated for one transverse loading condition on each end of the shelter. Two computer models are used to analyze the response at the personnel door end and seven models for the cargo door...
Topics: DTIC Archive, Johnson, Arthur R, ARMY NATICK RESEARCH AND DEVELOPMENT CENTER MA, *COMPUTER AIDED...
The literature on bending of beams made of bimodulus materials (which have one value of the elastic modulus in tension and another in compression) is limited. All of the works known to the present investigators are restricted to beams with natural boundary conditions and subjected to specific distributions of normal pressure only. In the present work, the transfer-matrix approach is used to determine the small-deflection static behavior of bimodulus beams, including transverse shear...
Topics: DTIC Archive, Bert,Charles W, OKLAHOMA UNIV NORMAN SCHOOL OF AEROSPACE MECHANICAL AND NUCLEAR...
A comprehensive theory for the dynamic response of linear continuous viscoelastic structural members is formulated with a modal analysis. The constitutive relation is in the form of a hereditary integral. A general set of formulas is derived that may be used for both non-self-adjoint and self-adjoint systems of governing equations of motion. Applications include a Voigt-Kelvin beam and a viscoelastic circular plate. (Author)
Topics: DTIC Archive, Pilkey,W D, VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MECHANICAL AND AEROSPACE...
The Structural Analysis Code Kit (SACK) is a collective group of structural computer programs which solve typical problems encountered in analysis and design. The user is expected to be familiar with structural analyses typically found in textbooks or an engineering school curriculum. These programs are free from proprietary limitations and are smaller in scope than large commercial programs. The programs are very simple to use and understand. They will not become obsolete when new building...
Topics: DTIC Archive, Mack, K, NAVAL CIVIL ENGINEERING LAB PORT HUENEME CA, *STRUCTURAL MECHANICS, TRUSSES,...
Five studies were performed under contract for concept definition of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) Project. The purpose of these studies was to examine numerous hub design concepts with the potential of meeting the technical goals and specifications set for the ITR/FRR. Thirty-three concepts were proposed, including 21 bearingless designs. Although the level of effort in these studies was not equivalent to a preliminary design, many important design issues for...
Topics: DTIC Archive, Bousman, William G., ARMY RESEARCH AND TECHNOLOGY LABS MOFFETT FIELD CA AEROMECHANICS...
A quasi free-free beam, simulating a flexible space structure, was equipped with inertial proof-mass actuators and sensors capable, in principle, of functioning in the space environment. Then tuning rules were derived which determine the optimal actuator passive stiffness and damping which minimizes the control effort required while increasing the modal damping in the structure. Active control using two local and one component level processor was demonstrated next. Lastly, multi-input, single...
Topics: DTIC Archive, Miller,David W, MASSACHUSETTS INST OF TECH CAMBRIDGE MA SPACE SYSTEMS LAB,...
Partial contents: advanced composites for large navy spacecraft; flight dynamics laboratory overview; deployable truss structure advanced technology; solar dynamic power systems for space station; mast flight system beam structure and beam structural performance; conceptual design of pointing control systems for space station gimballed payloads; development and use of a linear momentum exchange device; computer aided design and distributed system technology development for large space...
Topics: DTIC Archive, Wright, Robert L, NATIONAL AERONAUTICS AND SPACE ADMIN LANGLEY RESEARCH CENTER...
General models describing the interactions between a pair of piezoceramic patches and elastic substructures consisting of a cylindrical shell, plate and beam are presented. In each case, the manner in which the patch loads enter both the strong and weak forms of the time-dependent structural equations of motion is described. Through force and moment balancing, these loads are then determined in terms of material properties of the patch and substructure (thickness, elastic properties, Poisson...
Topics: DTIC Archive, Banks, H T, INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON...
The objective of this investigation was to study, in a limited way, the relative merit of this hypothesis, using an epoxy concrete to replace the portland cement concrete surrounding the lap splice. Six series of test beams of varying length of lap and companion test cylinders were cast. Concrete compressive strength, concrete and epoxy concrete tensile strengths, and relative beam strengths were determined for each test series. A comparison of test results was made with predicted critical lap...
Topics: DTIC Archive, Benedict,William E, COLORADO UNIV BOULDER DEPT OF CIVIL ENVIRONMENTAL AND...
A theoretical study and a series of beam tests were made on concrete members reinforced with high-strength deformed bars. The influence of: (1) the amount, yield strength and ductility of the tensile steel and (2) the amount, location and yield strength of the compression steel on the strength and ductility of a concrete beam is discussed. Then, the influence of the amount and yield strength of tensile steel on the stiffness of a beam is presented. The minimum yield-load factor (ratio of the...
Topics: DTIC Archive, Keenan, William A, NAVAL CIVIL ENGINEERING LAB PORT HUENEME CA, *BEAMS(STRUCTURAL),...
The main problem considered and solved is the minimum-weight design of a horizontal I-beam of constant web and variable flange thickness. The beam is simply supported at one end and built in at the other and is designed to with stand (in plastic flow) a concentrated vertical load of fixed intensity moving slowly from one end to the other. To introduce the general techniques employed, a few discrete versions of the problem are first presented and solved as linear- programming problems.
Topics: DTIC Archive, Gross, Oliver A, RAND CORP SANTA MONICA CA, *BEAMS(STRUCTURAL), FLANGES, LINEAR...
Topics: DTIC Archive, Plunkett, R, MINNESOTA UNIV MINNEAPOLIS DEPT OF AERONAUTICS AND ENGINEERING...
