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  • STRUCTURAL MECHANICS
  • 1975-1979  (181)
  • 1960-1964
  • 1955-1959
  • 1977  (181)
  • 1
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    A new method for predicting response in complex linear systems. II (1977)
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    Publication Date: 2011-08-17
    Description: The paper describes convergence and response studies in the low frequency range of complex systems, particularly with low values of damping of different distributions, and reports on the modification of the relaxation procedure required under these conditions. A new method is presented for response estimation in complex lumped parameter linear systems under random or deterministic steady state excitation. The essence of the method is the use of relaxation procedures with a suitable error function to find the estimated response; natural frequencies and normal modes are not computed. For a 45 degree of freedom system, and two relaxation procedures, convergence studies and frequency response estimates were performed. The low frequency studies are considered in the framework of earlier studies (Kayser and Bogdanoff, 1975) involving the mid to high frequency range.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 53; Aug. 22
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  • 2
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    Response of a beam on an inertial foundation to a traveling load (1977)
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    Publication Date: 2011-08-17
    Description: The response of a Bernoulli-Euler beam supported by a Winkler-type elastic foundation with inertia and subjected to a moving load is investigated. Steady-state solutions are determined for an undamped and linearly damped beam-foundation system. The effects on the response of load velocity, foundation mass, and damping are studied. For the undamped system, it is well known that the response grows without bound as a certain critical velocity is approached. It is shown that the effect of foundation mass is to reduce the critical velocity and to increase the peak deflection. The increase in peak deflection becomes more pronounced as the critical velocity is approached. As in the case of massless foundation, the deflection wave is observed to be symmetric with respect to the load. When damping is introduced, the deflection wave loses its symmetry, and the peak deflection is reduced. Results for both cases are given in graphical form.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 15; Aug. 197
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  • 3
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    Three dimensional beam elements synthesis applications with stress constraints, nonlinear size-stiffness relationships and various size-inertia powers (1977)
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    Publication Date: 2011-08-17
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 7; Aug. 197
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  • 4
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    On the role of minicomputers in structural design (1977)
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    Publication Date: 2011-08-17
    Description: Results are presented of exploratory studies on the use of a minicomputer in conjunction with large-scale computers to perform structural design tasks, including data and program management, use of interactive graphics, and computations for structural analysis and design. An assessment is made of minicomputer use for the structural model definition and checking and for interpreting results. Included are results of computational experiments demonstrating the advantages of using both a minicomputer and a large computer to solve a large aircraft structural design problem.
    Keywords: STRUCTURAL MECHANICS
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  • 5
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    Imperfection surveys on a 10-ft-diameter shell structure (1977)
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    Publication Date: 2011-08-17
    Description: The results of an extensive imperfection survey on a 10-ft-diameter integrally stiffened cylindrical shell are presented. The shape of the measured initial imperfections is clearly influenced by details of the shell construction. The modal components of the measured imperfection surface as a function of the circumferential and of the axial wave numbers are calculated. The discrete axial power spectral density functions and the corresponding root-mean-square values of the imperfections are also determined for given circumferential wave numbers. Using the Fourier coefficients of the measured initial imperfections, buckling loads are calculated by solving the nonlinear Donnell-type imperfect shell equations iteratively. The calculated lowest buckling load compares favorably with the values usually recommended for similar shell structures.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 15; July 197
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  • 6
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    A finite element technique for non-deterministic thermal deformation analyses including temperature dependent material properties (1977)
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    Publication Date: 2011-08-17
    Description: A technique utilizing the finite element displacement method is developed for the static analysis of structures subjected to non-deterministic thermal loading in which the material properties, assumed isotropic, are temperature dependent. Matrix equations are developed for the first two statistical moments of the displacements using a third order series expansion for the displacements in terms of the random temperatures. Sample problems are included to demonstrate the range of applicability of the third order series solutions. These solutions are compared with results from Monte Carlo analyses and also, for some problems, with solutions obtained by numerically integrating equations for the statistical properties of the displacements. In general, it is shown that the effect of temperature dependent material properties can have a significant effect on the covariances of the displacements.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 11; 6, 19; 1977
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  • 7
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    Forced vibrations of simply supported orthotropic sandwich plates (1977)
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    Publication Date: 2011-08-17
    Description: Force transmissibility, driving-point impedance, and transfer impedance of a simply supported rectangular orthotropic sandwich plate are investigated. The plate is driven by a sinusoidally varying point force either at the plate center or at any arbitrary location. The variation of force transmissibility and impedance with frequency, and the manner in which this is influenced by the various sandwich-plate parameters are studied and presented graphically.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America; vol. 61
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  • 8
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    Symbolic manipulation techniques for vibration analysis of laminated elliptic plates (1977)
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    Publication Date: 2011-08-17
    Description: A computational scheme is presented for the free vibration analysis of laminated composite elliptic plates. The scheme is based on Hamilton's principle, the Rayleigh-Ritz technique and symmetry considerations and is implemented with the aid of the MACSYMA symbolic manipulation system. The MACYSMA system, through differentiation, integration, and simplification of analytic expressions, produces highly-efficient FORTRAN code for the evaluation of the stiffness and mass coefficients. Multiple use is made of this code to obtain not only the frequencies and mode shapes of the plate, but also the derivatives of the frequencies with respect to various material and geometric parameters.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Proc. of the 1977 MACSYMA Users' Conf. (NASA); p 161-175
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  • 9
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    Doubly-curved variable-thickness isoparametric heterogeneous finite element (1977)
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    Publication Date: 2011-08-17
    Description: This paper describes an element streamlined for the analysis of doubly-curved, variable-thickness structural components and illustrates its effective application to vibration and static problems. The element is isoparametric, doubly-curved, thin-shell and triangular with variable thickness and accounts for anisotropic, inhomogeneous elastic material behavior. The element has six nodes (three corner and three mid-side) with five degrees-of-freedom (DOF) per node - three translations and two rotations. Quadratic isoparametric interpolation polynomials are used to express the element geometry and displacement variables in terms of corresponding nodal variables.
    Keywords: STRUCTURAL MECHANICS
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  • 10
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    Hamilton's principle - Finite-element methods and flexible body dynamics (1977)
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    Publication Date: 2011-08-17
    Description: A variational formulation is given for the equations of motion for an unconstrained elastic body, and Hamilton's principle is used to derive the equations of motion and deformation of the body. Finite-element approximations are developed for these dynamical equations with respect to a body axis system satisfying the mean axis conditions. The free-body influence matrix for the body then is developed in terms of the finite-element model parameters.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 15; Dec. 197
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  • 11
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    Strain gage calibration of a complex wing (1977)
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    Publication Date: 2011-08-17
    Description: Modern complex structural arrangements have complicated the task of measuring flight loads with calibrated strain gages. This paper examines the use of a relatively simple structural model to characterize the load responses of strain gages located on various spars of a delta wing. Strains measured during a laboratory load calibration of a wing structure are compared with calculations obtained from a simplified NASA structural analysis (NASTRAN) model. Calculated and measured influence coefficient plots that show the shear, bending, and torsion characteristics of typical strain-gage bridges are presented. Typical influence coefficient plots are given for several load equations to illustrate the derivation of the equations from the component strain-gage bridges. A relatively simple structural model was found to be effective in predicting the general nature of strain distributions and influence coefficient plots. The analytical processes are shown to be useful in obtaining a good load calibration. The analytical processes cannot, however, be used in lieu of an actual load calibration of an aircraft wing.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft; 14; Dec. 197
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  • 12
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    Scaling a discrete structural model to match measured modal frequencies (1977)
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    Publication Date: 2011-08-17
    Description: The structure modification problem, where the computer model of a structure is to be upgraded on the basis of experimental measurements of normal mode frequencies, is approached by the modal energy concept. The modes for correlation with test data are selected on the basis of relative strain energy participation. The resulting procedure can be viewed as an extension of White's (1972) method. Its advantage lies in that both the number and choice of structural parameters to be varied in the modification are arbitrary.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 15; Nov. 197
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  • 13
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    Mode I stress intensity factors for round compact specimens (1977)
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    Publication Date: 2011-08-17
    Description: Mode I stress intensity factors were computed for round compact specimens by the boundary collocation method. Results are presented for ratios At/R0 in the range 0.3 to 0.8, where At is the distance from the specimen center to the crack tip for a specimen of diameter 2R0.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Testing and Evaluation; 5; Nov. 197
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  • 14
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    Analysis and testing of adhesive bonds (1977)
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    Publication Date: 2011-08-17
    Description: An adhesive fracture mechanics approach is described with reference to the identification and design of the best tests for evaluating a given adhesive, the definition of the most meaningful fundamental parameters by which adhesives might be characterized, and the application of these parameters to the design of joints and to the prediction of their performance. Topics include standard adhesive test techniques, the theory of adhesive fracture, and adhesive fracture energy tests. Analytical methods and computer techniques for adhesive bonding, chemical and physical aspects of adhesive fracture, and specific applications and aspects of adhesive fracture mechanics are discussed.
    Keywords: STRUCTURAL MECHANICS
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  • 15
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    Automated multi-level substructuring for Sperry's version of NASTRAN (1977)
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    Publication Date: 2016-06-07
    Description: Automated multilevel substructuring was successfully implemented in the Sperry version of NASTRAN. The development was achieved with a minimum effort; only seven modules and fourteen new routines were added. Approximately forty subroutines were modified and four new user cards addeded to NASTRAN. Significant features of the new capability include: multilevel substructuring; up to 128 superelements; up to 456 boundary grid points per superelement; up to 9 user superelement files, each with multi-reel or disc option; and data storage for one or more superelements per user file.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 133-154
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  • 16
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    Structural model integrity (1977)
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    Publication Date: 2016-06-07
    Description: Many of the practical aspects and problems of ensuring the integrity of a structural model are discussed, as well as the steps which have been taken in the NASTRAN system to assure that these checks can be routinely performed. Model integrity as used applies not only to the structural model but also to the loads applied to the model. Emphasis is also placed on the fact that when dealing with substructure analysis, all of the checking procedures discussed should be applied at the lowest level of substructure prior to any coupling.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 93-104
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  • 17
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    Finite element solutions of free surface flows (1977)
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    Publication Date: 2016-06-07
    Description: A procedure is presented for using NASTRAN to determine the flow field about arbitrarily shaped bodies in the presence of a free surface. The fundamental unknown of the problem is the velocity potential which must satisfy Laplace's equation in the fluid region. Boundary conditions on the free surface may involve second order derivatives in space and time. In cases involving infinite domains either a tractable radiation condition is applied at a truncated boundary or a series expansion is used and matched to the local finite elements. Solutions are presented for harmonic, transient, and steady state problems and compared to either exact solutions or other numerical solutions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 27-52
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  • 18
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    RINA: An interactive system for the rapid interpretation of NASTRAN results (1977)
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    Publication Date: 2016-06-07
    Description: RINA is a general post-processor system which performs data reduction, post processing and post analysis of NASTRAN results. RINA can be run in either batch or time-sharing mode. The system, which is an expansion of the NASDAT program, performs the following tasks: (1) scan of extreme values for displacements, forces, stresses and margins of safety, (2) computations of envelopes for displacements, forces, stresses and margins of safety, (3) computations of allowables and margins of safety; and (4) generation of NASTRAN tables needed for reanalysis computations. Usage of all these options provides the analyst with an efficient tool for the study and interpretation of NASTRAN analysis results and their presentation for project documentation.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 341-355
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  • 19
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    Software for transferring NASTRAN datablocks between dissimilar computers (1977)
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    Publication Date: 2016-06-07
    Description: Efforts to freely exchange all types of NASTRAN datablocks between the internalized forms in any of three makes of NASTRAN-class computers and that of any other such make are described. The medium used is magnetic tape formatted in BCD (Binary Coded Decimal) character and numerical fields. The method used involves a FORTRAN-coded post-processor and a pre-processor, mostly portable but with a small assembly-coded component peculiar to each make of machine. Snags in a method reported in an earlier NASTRAN colloquium have been overcome and functional requirements upgraded as well.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 357-368
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  • 20
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    A stand-alone interactive graphics finite element modeling system (1977)
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    Publication Date: 2016-06-07
    Description: The finite element modeling (FEM) system described here is an interactive graphics system designed for use with an intelligent terminal. It offers an economical alternative to the conventional methods (hand compilation and remote terminals) of 2 and 3-dimensional model generation. Using local computing and local storage, this FEM system allows the operator to create and display 3-dimensional models entirely off-line from the host computer. This eliminates costly on-line computer and host-processing time, and makes the user more effective by greatly reducing computer response time. The system allows model generation by down-loading node and element data from the host computer or by using the system's model generation operations for digitizing and automatic creation. The system then generates completed model information in the desired analysis package's bulk data format and transmits it to the host computer for finite element analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 327-340
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  • 21
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    Application of symbolic/numeric matrix solution techniques to the NASTRAN program (1977)
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    Publication Date: 2016-06-07
    Description: The matrix solving algorithm of any finite element algorithm is extremely important since solution of the matrix equations requires a large amount of elapse time due to null calculations and excessive input/output operations. An alternate method of solving the matrix equations is presented. A symbolic processing step followed by numeric solution yields the solution very rapidly and is especially useful for nonlinear problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 193-198
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  • 22
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    New large deflection analysis for NASTRAN (1977)
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    Publication Date: 2016-06-07
    Description: A large deflection analysis was developed for NASTRAN level 16 as an alternative to Rigid Format 4. A progress report is presented for a long term, general nonlinear analysis NASTRAN project, which contains (1) the theory of the structural analysis and numerical analysis methods presently used, and (2) some simple test problems comparing the new analysis with Rigid Format 4.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 235-255
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  • 23
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    Study of the NASTRAN input/output systems (1977)
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    Publication Date: 2016-06-07
    Description: The basic characteristics of the NASTRAN level 16 I/O subsystem are presented with particular reference to blocking/deblocking aspects, I/O methods used on the IBM, CDC, and UNIVAC machines, definition of basic NASTRAN I/O control tables, and portability of parts of the I/O subsystem to other programs outside the NASTRAN environment are included. An explanation of the IBM primary, secondary, and tertiary files defined by the data definition (DD) cards in the NASTRAN JCL procedure. The explanation is intended to enlighten users as to the purpose of these DD cards, how they relate to one another, and why there are no similar type definition cards required on the CDC and UNIVAC versions. Enhancements designed to increase overall efficiency and decrease core requirements are also recommended.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 75-91
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  • 24
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    NORCK: A NASTRAN module to check input data and element geometry (1977)
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    Publication Date: 2016-06-07
    Description: NORCK, a direct matrix abstraction module, was written which allows the user the ability to define error limits for finite element geometry and properties within the solution flow, and to find these errors before the more expensive parts of the analysis are run.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 65-74
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  • 25
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    NASTRAN: Status, plans, and performance (1977)
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    Publication Date: 2016-06-07
    Description: Plans for NASTRAN, a program developed and improved over the past 13 years, were outlined in reference to a new capability of level 17. The target release date is given as December 1977 and domestic release will be through COSMIC. As an example of the improved efficiency of NASTRAN level 16, a table of CPU run time comparisons is shown.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; ix-xviii
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  • 26
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    Stress analysis of pressure vessel assembly (1977)
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    Publication Date: 2016-06-07
    Description: A radome assembly capable of withstanding large hydrostatic pressures was designed with a sapphire hemisperical dome and a plastic housing. These two parts were connected with a stainless steel flange ring. A finite-element stress analysis of this assembly was accomplished and an experimental load test was performed to verify the predicted stresses.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 405-417
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  • 27
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    NASTRAN finite element idealization study (1977)
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    Publication Date: 2016-06-07
    Description: The investigation of the effects of variations of mesh refinement and mesh pattern were conducted using a basic rectangular mesh pattern. When employing the constant strain TRMEM element, the basic rectangular pattern was subdivided into triangles. This subdivision employs two different triangular patterns and allows results to be obtained which demonstrate the effect of modelling bias. Errors in tip deflection, direct stress, and shearing stress as a function of mesh size and element aspect ratio were obtained as well as mid-span stress distributions. All problems were solved on an IBM 360/95 computer using MacNeal-Schwendler Version MSC-38 Rigid Format-1 of the NASTRAN computer program. While NASTRAN uses double precision arithmetic for the solution of the global equations for displacements, subsequent computations to obtain element stresses are carried out in single precision. This suggests that some improvement in stress recovery might be expected when using the higher precision DCD machines.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 383-403
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  • 28
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    Application of the TRPLT1 element to large amplitude free vibrations of plates (1977)
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    Publication Date: 2016-06-07
    Description: A finite element formulation is developed for analyzing large amplitude free flexural vibrations of thin plates in NASTRAN. Stress distributions in the plate, in addition to deflection shapes and nonlinear frequencies are determined. Linearized equations of motion governing large amplitude oscillations of plates and a linearized geometrical stiffness matrix are presented. The solution procedure and convergence characteristics are discussed. The quasi-linear geometrical stiffness matrix for an eighteen degree-of-freedom higher order triangular plate element is evaluated by using a seven-point numerical integration. Nonlinear frequencies for square, rectangular, rhombic, and isosceles triangular plates, with edges simply supported or clamped, are compared with earlier solutions. The present formulation is found to give results entirely adequate for engineering purposes.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 275-298
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  • 29
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    A NASTRAN DMAP alter for the coupling of modal and physical coordinate substructures (1977)
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    Publication Date: 2016-06-07
    Description: A method is described to derive a generalized coordinate model consisting of flexible cantilever modes and rigid body modes from a physical coordinate model using a direct matrix abstraction procedure alter to rigid format 3. This model can readily be coupled to other substructures using modal synthesis techniques. It allows the use of a reduced size model for structural analyses while maintaining the capability of recovering the accelerations, forces, stresses, etc., from the original, large, complex model. This output recovery is accomplished with the use of a loads transformation matrix which relates the output parameters to the modal coordinate accelerations. In addition, a method is described to synthesize structural models consisting of hybrid coordinates for use in dynamic response analyses where one structure is described using physical coordinates and the other using generalized modal coordinates.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 119-130
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  • 30
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    Addition of rigid elements to NASTRAN (1977)
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    Publication Date: 2016-06-07
    Description: Four rigid elements, namely, a rigid rod element (CRIGDR) and three rigid body elements (CRIGD1, GRIGD2 and CRIGD3), have recently been added to NASTRAN and will be available in the next public release of the program. The theoretical formulation, the bulk data information and the programming details pertaining and realistic problems are illustrated by employing them in the solution of two helicopter structural analysis problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 449-468
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  • 31
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    A condensed form of NASTRAN (1977)
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    Publication Date: 2016-06-07
    Description: The Interactive Graphics Finite Element System, IGFES, is described along with its supporting analysis software, graphics terminal support package and hardware configurations. IGFES provides an interactive design tool for structural engineers via pre- and postprocessing of finite element data. The system currently runs on an IBM 360/44 OS-MFT system or a PDP 11/40 DOS/BATCH system. Graphics devices are supported using an inhouse developed, device independent terminal support package. Support is available for the Calcomp 563 drum plotter, Tektronix 4002A storage display terminal and the Lundy Electronics 20 inch standalone refresh display system. IGFES and its associated systems are written in FORTRAN IV.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 299-325
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  • 32
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    A direct matrix abstraction procedure for a static solution during a phase 1 substructuring analysis (1977)
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    Publication Date: 2016-06-07
    Description: A directed matrix abstraction procedure is described which allows a static solution to be obtained in phase 1 of a three phase NASTRAN substructuring analysis while at the same time storing all information needed to complete the substructuring analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 105-117
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    Analysis of magnetic fields using variational principles and CELAS2 elements (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: Prospective techniques for analyzing magnetic fields using NASTRAN are reviewed. A variational principle utilizing a vector potential function is presented which has as its Euler equations, the required field equations and boundary conditions for static magnetic fields including current sources. The need for an addition to this variational principle of a constraint condition is discussed. Some results using the Lagrange multiplier method to apply the constraint and CELAS2 elements to simulate the matrices are given. Practical considerations of using large numbers of CELAS2 elements are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 175-192
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    A review of research on aeronautical fatigue in the United States, 1975 - 1977 (1977)
    In:  Other Sources
    Details
    Publication Date: 2016-03-09
    Keywords: STRUCTURAL MECHANICS
    Type: Lab. fuer Betriebsfestigkeit Minutes of the Fifteenth Conf. of the Intern. Comm. on Aeronautical Fatigue (ICAF) 80p (SEE N84-73852 14-39)
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  • 35
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    Development of an automated multi-stage modal synthesis system for NASTRAN (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: A mode synthesis development to be scheduled in the NASTRAN multi-level substructuring system for general dynamics applications is described. The method combines the better features of several state of the art mode synthesis techniques, yet is general enough to provide for any arbitrary combination of boundary degrees of freedom and normal mode boundary conditions. Normal modes or complex eigenvectors may be used in the definition of a structure component which may be combined with other components of any type. Combination structures fabricated from component modes may be processed as normal substructures, including further multi-stage mode synthesis reductions. Included are discussions of the user control of the system and advantages in actual application.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 435-448
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  • 36
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    An automated data generator for NASTRAN (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: A modeling system based on construction-in-context of geometry and physical properties data is adapted for NASTRAN finite element data generation. This system was originally developed for generating three-dimensional finite data for composite structures in PATCHES-III using parametric cubic models. These finite line, surface and volume models constructed using simple data directives will be subdivided into NASTRAN finite elements and their supporting data in the new data generator. Any geometry can be constructed as illustrated by a compressor fan blade with camber, twist and changing airfoil section and the shape then subdivided using a uniform or non-uniform mesh. Special emphasis is given to the adaption of construction-in-context to composite material property modeling. A PMAT series of directives is described for any one, two or three-dimensionally reinforced composite that allows the phase properties, as well as composite properties, to be generated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 419-434
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  • 37
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    Singular plastic element: NASTRAN implementation and application (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The elastic and plastic singularities near a crack tip are obtained from higher order isoparametric elements. This is simply accomplished by collapsing the quadrilateral element into the triangular element and by judicious choice of adjacent mid-side nodes. Specifically for the cubic element the elastic singularity is obtained by placing the mid-side nodes adjacent to the crack tip at 1/9th and 4/9th locations. The plastic singularity is constructed using the sliding node concept. These elements have been implemented in NASTRAN as user dummy elements.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 257-273
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  • 38
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    Alternate approaches to vibration and shock analysis using NASTRAN (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method that derives an approximate equivalent static load to a base excitation shock analysis is described. The transient analysis in the current level of NASTRAN, level 16, does not directly provide for either input acceleration forcing functions or enforced boundary displacement. In the suggested alternate analysis format, equivalent force input functions are applied to the constrained locations by using the artifice of placing a large mass, with respect to the total system mass, at the desired acceleration input points. This shortcut static analysis approach is presented to approximate the expensive and time consuming dynamics analysis approach to the base excitation shock analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 199-212
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  • 39
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    Unexpected dividends from level 16 automated substructuring (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The automated multistage substructuring capability now available in NASTRAN level 16 is shown to provide a number of unexpected tools for use in both project planning and the structural design cycle. The payoffs in terms of improved design, more reliable results, and confidence are extra benefits added to the savings in cost and schedule that can be realized. To realize these advantages, some old stereotypical assumptions of what substructuring entails are must be challenged.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 155-160
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  • 40
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    Modifying the NASTRAN system with a new capability (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The need for a new capability/maintenance interface specification for the NASTRAN system was discussed. Those problems are highlighted which are most difficult to resolve when a new capability is delivered for inclusion into an archive level. The guidelines presented show the objectives of new capability integration as they relate to design and development, delivery, checkout, and documentation. Examples of new capability/maintenance interface already done on an informal basis are presented to illustrate the 'test conditions' of the idea of defining implementation objectives.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 53-64
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  • 41
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    Substructure coupling: A different approach (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The substructure analysis of the Lockheed L-1011 Dash 500 long range derivative without use of the NASTRAN level 16 multistage substructuring capability is described. It is presented as an example of how a large structural analysis can be organized into manageable independent tasks and how preprocessors, model definition conventions, and data management programs can be used to simplify the data management and model documentation. A procedure is described to analyze a single substructure by modifying the static solution to solve the interface compatibility equations simultaneously with the substructure solution.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 161-173
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  • 42
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    A 3-D hydroelastic analysis in NASTRAN with general fluid and structure geometry (1977)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The implementation of a general three dimensional hydroelastic mode analysis capability in NASTRAN is presented. Finite elements with polyhedral shapes define the fluid; existing NASTRAN plate elements define the fluid/structure interface. Efficient solution methods were implemented to allow a separate structural matrix reduction and to allow connection of the fluid mass directly to a small set of grid points or modal coordinates representing the structure. Test case results for the various solution options are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 3-23
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  • 43
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    Outer planet probe engineering model structural tests (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A series of proof of concept structural tests was performed on an engineering model of the Outer Planets Atmospheric Entry Probe. The tests consisted of pyrotechnic shock, dynamic and static loadings. The tests partially verified the structural concept.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-152036
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  • 44
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    A method for the direct identification of vibration parameters from the free response (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: STRUCTURAL MECHANICS
    Type: The Shock and Vibration Inform. Ctr. Shock and Vibration Bull. Part. 4: Sep. 1977; p 183-198
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  • 45
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    Stress analysis and stress-intensity factors for finite geometry solids containing rectangular surface cracks (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement field in a finite geometry bar containing a variable depth rectangular surface crack under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Using the obtained displacement field, normal stresses, and the stress-intensity factor variation along the crack periphery are calculated for different crack depth to bar thickness ratios. Crack opening displacements and stress-intensity factors are also obtained for a through-thickness, center-cracked bar with variable thickness. The reported results show a considerable potential for using this method in calculating stress-intensity factors for commonly encountered surface crack geometries in finite solids
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 77-WA/APM-5
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  • 46
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    Elasto-plastic flow in cracked bodies using a new finite element model (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Cracked geometries were studied by finite element techniques with the aid of a new special element embedded at the crack tip. This model seeked to accurately represent the singular stresses and strains associated with the elasto-plastic flow process. The present model was not restricted to a material type and did not predetermine a singularity. Rather the singularity was treated as an unknown. For each step of the incremental process the nodal degrees of freedom and the unknown singularity were found through minimization of an energy-like functional. The singularity and nodal degrees of freedom were determined by means of an iterative process.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-155522 , SM-77-11
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  • 47
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    TV fatigue crack monitoring system (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An apparatus is disclosed for monitoring the development and growth of fatigue cracks in a test specimen subjected to a pulsating tensile load. A plurality of television cameras photograph a test specimen which is illuminated at the point of maximum tensile stress. The television cameras have a modified vidicon tube which has an increased persistence time thereby eliminating flicker in the displayed images.
    Keywords: STRUCTURAL MECHANICS
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  • 48
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    CW ultrasonic bolt tensioning monitor (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A CW ultrasonic device is described for measuring frequency shifts of the peak of a mechanical resonance in a body. One application of the device is measuring the strain in a bolt, and other applications such as measuring the thickness of a body, measuring the depth of a flaw in a body, measuring the elongation of a body, and measuring changes in velocity of sound in a body. The body is connected, by means of a CW transducer, to electrical circuit means including a narrow band RF amplifier to form a closed loop feedback marginal oscillator that frequency locks the device to the peak of a mechanical resonance in the body. When the frequency of this peak changes, because of a physical change in the body, the frequency of the oscillator changes. The device includes an automatic frequency resonant peak tracker that produces a voltage that is related to a change in frequency of the oscillator. This voltage is applied to the RF amplifier to change the center of its frequency band to include the frequency of the peak and is a measure of the frequency shift.
    Keywords: STRUCTURAL MECHANICS
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  • 49
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    Structural analysis of ultra-high speed aircraft structural components (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The buckling characteristics of a hypersonic beaded skin panel were investigated under pure compression with boundary conditions similar to those found in a wing mounted condition. The primary phases of analysis reported include: (1) experimental testing of the panel to failure; (2) finite element structural analysis of the beaded panel with the computer program NASTRAN; and (3) summary of the semiclassical buckling equations for the beaded panel under purely compressive loads. A comparison of each of the analysis methods is also included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-155334
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  • 50
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    Effect of end-ring stiffness on buckling of pressure-loaded stiffened conical shells (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Buckling studies were conducted on truncated 120 deg conical shells having large end rings and many interior reinforcing rings that are typical of aeroshells used as spacecraft decelerators. Changes in base-end-ring stiffness were accomplished by simply machining away a portion of the base ring between successive buckling tests. Initial imperfection measurements from the test cones were included in the analytical model.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1079 , L-11915
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  • 51
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    NASTRAN use for cyclic response and fatigue analysis of wind turbing towers (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A procedure is described which uses NASTRAN coupled with fatigue criteria via a postprocessor to determine the cyclic response and to assess the fatigue resistance (fatigue life) of wind turbine generator towers. The cyclic loads to which the tower may be subjected are entered either in a quasi-static approach though static load subcases (Rigid Format 1) or through the direct dynamic response (Rigid Format 9) features of NASTRAN. The fatigue criteria are applied to NASTRAN output data from either rigid format through an externally written user program embedded in a postprocessor.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 213-233
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  • 52
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    Modal identification of structures from the responses and random decrement signatures (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The theory and application of a method which utilizes the free response of a structure to determine its vibration parameters is described. The time-domain free response is digitized and used in a digital computer program to determine the number of modes excited, the natural frequencies, the damping factors, and the modal vectors. The technique is applied to a complex generalized payload model previously tested using sine sweep method and analyzed by NASTRAN. Ten modes of the payload model are identified. In case free decay response is not readily available, an algorithm is developed to obtain the free responses of a structure from its random responses, due to some unknown or known random input or inputs, using the random decrement technique without changing time correlation between signals. The algorithm is tested using random responses from a generalized payload model and from the space shuttle model.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-155321
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  • 53
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    The crack-contact and the free-end problem for a strip under residual stress (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The plane problem for an infinite strip with two edge cracks under a given state of residual stress is considered. The residual stress is compressive near and at the surfaces and tensile in the interior of the strip. If the crack is deep enough to penetrate into the tensile zone, then the problem is one of crack-contact where the depth of the contact area is an unknown which depends on the crack depth and the residual stress profile. The problem has applications to the static fatigue of glass plates and is solved for three typical residual-stress profiles. In the limiting case of the crack's crossing the entire plate thickness, the problem becomes a stressfree end problem for a semiinfinite strip under a given residual-stress state away from the end. This is a typical stress diffusion problem in which decay behavior of the residual stress near and the nature of the normal displacement at the end of the semiinfinite strip are of special interest. For two typical residual-stress states the solution is obtained, and some numerical results are given.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 77-APM-3
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  • 54
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    Stress computation in displacement methods for two-material elastic media (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The method of best fit strain tensors is extended to compute the stresses satisfying the conditions of equilibrium, compatibility, and constitutive relationships. It is assumed that the deflections at the mesh points have already been computed with acceptable accuracy. Results of examples presented show better accuracy than the usual procedure, in which equilibrium conditions are not enforced. Special emphasis is placed here upon two-material elastic media.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Methods in Applied Mechanics and Engineering; 10; Mar. 197
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  • 55
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    Crack border stress and displacement equations revisited (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: It is more or less accepted in fracture mechanics that the elastic stress and displacements very near to the tip of a plane line crack can be approximated with sufficient accuracy, for all geometries and outer boundary loading conditions, by a one-parameter representation, i.e., strictly in terms of the stress intensity factors KI and/or KII. It is shown here that this presumption which appears to be reasonable on face value, quantitatively speaking, is nevertheless unacceptable as a general proposition. The reason lies with the quite arbitrary practice of omitting the second term of the series representation for the stresses, a contribution which is independent of distance from the crack tip. It is not difficult to show by way of specific examples how such omission can lead to error of serious qualitative nature in the prediction of stress and displacement related quantities of interest.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 9; 1, 19; 1977
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  • 56
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    An optimality criterion for sizing members of heated structures with temperature constraints (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A thermal optimality criterion is presented for sizing members of heated structures with multiple temperature constraints. The optimality criterion is similar to an existing optimality criterion for design of mechanically loaded structures with displacement constraints. Effectiveness of the thermal optimality criterion is assessed by applying it to one- and two-dimensional thermal problems where temperatures can be controlled by varying the material distribution in the structure. Results obtained from the optimality criterion agree within 2 percent with results from a closed-form solution and with results from a mathematical programming technique. The thermal optimality criterion augments existing optimality criteria for strength and stiffness related constraints and offers the possibility of extension of optimality techniques to sizing structures with combined thermal and mechanical loading.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-8525 , L-11601
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  • 57
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    Transverse shear effects on the stress-intensity factor for a circumferentially cracked, specially orthotropic cylindrical shell (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The problem of a cylindrical shell containing a circumferential through crack is considered by taking into account the effect of transverse shear deformations. The formulation is given for a specially orthotropic material within the confines of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions regarding moment and stress resultants on the crack surface. Consequently, aside from multiplicative constants representing the stress intensity factors, the membrane and bending components of the asymptotic stress fields near the crack tip are found to be identical. The stress intensity factors are calculated separately for a cylinder under a uniform membrane load, and that under a uniform bending moment. Sample results showing the nature of the out-of-plane crack surface displacement and the effect of the Poisson's ratio are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-145265
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    Complex eigenvalue extraction in NASTRAN by the tridiagonal reduction (FEER) method (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An extension of the Tridiagonal Reduction (FEER) method to complex eigenvalue analysis in NASTRAN is described. As in the case of real eigenvalue analysis, the eigensolutions closest to a selected point in the eigenspectrum are extracted from a reduced, symmetric, tridiagonal eigenmatrix whose order is much lower than that of the full size problem. The reduction process is effected automatically, and thus avoids the arbitrary lumping of masses and other physical quantities at selected grid points. The statement of the algebraic eigenvalue problem admits mass, damping and stiffness matrices which are unrestricted in character, i.e., they may be real, complex, symmetric or unsymmetric, singular or non-singular.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-145258 , AMA-77-17
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  • 59
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    Biaxial load effects on the crack border elastic strain energy and strain energy rate (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The validity of the singular solution (first term of a series representation) is investigated for the crack tip stress and displacement field in an infinite sheet with a flat line crack with biaxial loads applied to the outer boundaries. It is shown that if one retains the second contribution to the series approximations for stress and displacement in the calculation of the local elastic strain energy density and elastic strain energy rate in the crack border region, both these quantities have significant biaxial load dependency. The value of the J-integral does not depend on the presence of the second term of the series expansion for stress and displacement. Thus J(I) is insensitive to the presence of loads applied parallel to the plane of the crack.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 9; 4, 19; 1977
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  • 60
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    An orthotropic laminate composite containing a layer with a crack (1977)
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    Publication Date: 2019-06-27
    Description: A laminate composite containing an orthotropic layer with a crack situated normal to the interfaces, and bonded to two orthotropic half-planes of dissimilar materials, is considered. The solutions for two different classes of orthotropic materials are presented separately. In each case, the problem is first reduced to a system of dual integral equations, then to a singular integral equation which is subsequently solved numerically for the stress intensity factors at the tip of the crack. The effect of the material properties on the stress intensity factor is investigated. Two cases, the generalized plane stress and the plane strain, are treated simultaneously.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Engineering Science; 15; 9-10,; 1977
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  • 61
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    Digital generation of alongwind velocity field (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A procedure is described for generating simulation samples of the two-dimensional fluctuating component of the wind velocity acting on the surface of a paraboloidal antenna. A numerical example shows that a simulation sample can be generated rapidly by computer with results that appear reasonable. To complete the performance evaluation of the antenna surface for the random wind velocity, it would be necessary to combine the velocity field with pressure coefficients that can be established for the antenna surface. Loading coefficients could be derived readily from this combination and then standard procedures could be applied for the evaluation of the antenna rms measure of performance in response to the loading.
    Keywords: STRUCTURAL MECHANICS
    Type: American Society of Civil Engineers; Journal
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  • 62
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    Treatment of low strains and long hold times in high temperature metal fatigue by strainrange partitioning (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A procedure for treating creep-fatigue for low strainranges and long hold times is outlined. A semi-experimental approach, wherein several cycles of the imposed loading is actually applied to a specimen in order to determine the stable hysteresis loop, can be very useful in the analysis. Because such tests require only a small fraction of the total failure time, they are not inherently prohibitive if experimental equipment is available. The need for accurate constitutive equations is bypassed because the material itself acts to translate the imposed loading into the responsive hysteresis loops. When strainrange partitioning has been applied in such cases very good results have been obtained.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-156923 , ORNL/SUB-3988-1
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  • 63
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    Methods of component mode synthesis (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A generalized substructure coupling, or component mode synthesis, procedure is described. Specific methods, applications, and such special topics as damping and experimental verification are surveyed.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Digest, Vol. 9, No. 11; p 3-10
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    Alternatives for NASTRAN maintenance, modification and dissemination (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Various alternatives to direct NASA support of the program are considered ranging from no support at one end of the spectrum to subsidizing a non profit user's group at the other. Of all the alternatives that are developed, the user group appears to be most viable. NASA's past and future roles in the development of computerized technology are also considered. The need for an institute for computational analysis is identified and NASA's possible involvement is described. The goals of the proposed institute and research funds to support an activity that has the potential of a much larger impact on the technical community are identified.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-155220 , AE-77-1
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    Stress-intensity factors for a wedge-loaded edge crack in a semi-infinite strip (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The problem of a semi infinite strip containing an edge crack is considered. It is assumed that the strip is loaded by a frictionless rigid wedge pressed into the crack. The resulting crack contact problem is formulated in terms of a system of singular integral equations. The behavior of the solution near the singular points is studied in detail. A series of numerical examples are given and the results are compared with those obtained by the method of boundary collocation and by the simple beam theory.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-145264
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    Development of a moderately sized finite element program for nonlinear structural analysis (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: AGGIE 1 is a computer program for predicting the linear and nonlinear, static and dynamic structural response of two- and three-dimensional continuum solids. The program is based on isoparametric finite elements and allows for 2-D plane stress, plane strain, and axisymmetric analyses and general 3-D analyses. Large strain kinematics is based on the total Lagrangian formulation. Materially nonlinear models include several elastic-plastic work-hardening models as well as an incompressible Mooney-Rivlin model. Included in this report is a brief description of the theoretical bases of the program, the material models used, the element library and the overall program organization. Instructions for data input preparation are given in detail. Several sample problems are given along with the required program input and program generated solutions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-150882 , TR-3207-77-1
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    A Rayleigh-Ritz approach to the synthesis of large gyroscopic structures (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The equations of motion for large structures with rotating flexible components are derived by regarding the structure as an assemblage of substructures. Based on a stationarity principle for rotating structures, it is shown that each continuous or discrete substructure can be simulated by a suitable set of admissible functions or admissible vectors. This substructure synthesis approach provides a rational basis for truncating the number of degrees of freedom both of each substructure and of the assembled structure.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal de Mecanique Appliquee; 1; 4, 19; 1977
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    Acoustoelasticity - General theory, acoustic natural modes and forced response to sinusoidal excitation, including comparisons with experiment (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A comprehensive theoretical model has been developed for interior sound fields which are created by flexible wall motion resulting from exterior sound fields. Full coupling between the wall and interior acoustic cavity is permitted. An efficient computational method is used to determine acoustic natural frequencies of multiply connected cavities. Simplified formulae are developed for interior sound levels in terms of cavity, wall and external acoustic field parameters. Comparisons of theory and experiment show generally good agreement.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 52; June 22
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  • 69
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    The problem of internal and edge cracks in an orthotropic strip (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The plane elastostatic problem of internal and edge cracks in an infinite orthotropic strip is considered. The problems for the material types I and II are formulated in terms of singular integral equations. For the symmetric case the stress-intensity factors are calculated and are compared with the isotropic results. The results show that because of the dependence of the Fredholm kernels on the elastic constants in the strip (unlike the crack problem for an infinite plane) the stress-intensity factors are dependent on the elastic constants and are generally different from the corresponding isotropic results
    Keywords: STRUCTURAL MECHANICS
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    Determination of the critical loads of shells by nondestructive methods (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Two methods for determining the location of and load level to produce instability of compressed cylindrical shells are presented. The first relates the variation in the wall normal stiffness as a function of applied compressive force to the critical load. It uses the distribution of stiffness over the surface of the shell as a guide to buckle location. The second method associates the local dynamic mass with instability behavior. The test data presented show that either method will give excellent prediction capability from low-load-level data for shells of orthodox form. Neither method appears to apply to spirally stiffened shells. This is thought to be due to the fact that there is a substantial difference between the buckle pattern under axial compression and the imperfection shape induced by the normal displacement which is used to ascertain the wall stiffness and the dynamic mass.
    Keywords: STRUCTURAL MECHANICS
    Type: Experimental Mechanics; 17; Apr. 197
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  • 71
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    An experimental-theoretical correlation study of non-linear bending and torsion deformations of a cantilever beam (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An experimental study of the large deformation of a cantilevered beam under a gravity tip load has been made. The beam root is rotated so that the tip load is oriented at various angles with respect to the beam principal axes. Static twist and bending deflections of the tip and bending natural frequencies have been measured as a function of tip load magnitude and orientation. The experimental data are compared with the results of a recently developed non-linear structural theory. Agreement is reasonably good when bending deflections are small compared to the beam span, but systematic differences occur for larger deflections.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 50; Feb. 22
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  • 72
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    Instability analysis of torispherical pressure vessel heads with triangular thin-shell finite elements (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The elastic instability of an internally-pressurized cylindrical tank with a torispherical head is investigated using a triangular, doubly curved, thin-shell finite element. The formulation of the finite element, which is based upon cubic displacement functions and a modified principle of potential energy, is first described. Then, the element is verified by comparing numerical results for the linear, stable analysis to alternative solutions for the same problem. The subsequent instability investigation includes the solution of the linearized problem of equilibrium bifurcation, that is, of the classical eigenvalue problem, and a general nonlinear analysis, based on tracing the nonlinear load-displacement path. The critical pressure, obtained with use of the general nonlinear analysis, agrees closely with an experimental result as well as with a numerical solution stemming from an axisymmetric formulation.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 76-PVP-33
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  • 73
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    Crack propagation and arrest in pressurized containers (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The problem of crack propagation and arrest in a finite volume cylindrical container filled with pressurized gas is considered. It is assumed that the cylinder contains a symmetrically located longitudinal part-through crack with a relatively small net ligament. The net ligament suddenly ruptures initiating the process of fracture propagation and depressurization in the cylinder. The problem is formulated by making two major assumptions, namely, that the shell problem is quasi-static and the gas dynamics problem is one-dimensional. The problem is reduced to a proper initial value problem by introducing a dynamic fracture criterion which relates the crack acceleration to the difference between a load factor and the corresponding strength parameter. The main results are demonstrated by considering two examples, an aluminum cylinder which may behave in a quasi-brittle manner, and a steel cylinder which undergoes ductile fracture. The results indicate that generally in gas-filled cylinders fracture arrest is not possible unless the material behaves in a ductile manner and the container is relatively long.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 76-PVP-12
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  • 74
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    Nonlinear viscoelasticity and relaxation phenomena of polymer solids (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In the light of a three-chain model of statistical network theories of rubberlike elastic models, it is assumed that the free energy function of incompressible viscoelastic polymer solids is a separable, symmetric function of the principle stretch ratios and the hidden thermodynamic coordinates along the same directions. This assumption leads to a characterization of those viscoelastic polymer solids which exhibit the property of factorizability between the time and strain functions.
    Keywords: STRUCTURAL MECHANICS
    Type: Acta Mechanica; 25; 3-4,; 1977
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  • 75
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    The effect of configuration on strength, durability, and handle of Kevlar fabric-based materials (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Five Kevlar based laminates and three Kevlar based coated materials were designed, hand made, and tested against comparative conventional Dacron based materials for strength, peel, tear, puncture, creases, and handle. Emphasis was placed on evaluating geometric orientation of constituents, use of elastomeric film in place of high modulus films, and the use of flying thread loom bias reinforcement of Kevlar yarns. Whereas, the performance of the Kevlar laminates was severely degraded by crease effects, significant gains in overall performance factors were shown for the coated Kevlar materials.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2738
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    Effects of damping on mode shapes, volume 2 (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Data values for the finite damping elements were assigned to duplicate overall low-frequency modal damping values taken from tests of similar vehicles. For comparison with the calculated admittances, position and rate gains were computed for a conventional shuttle model for the liftoff condition. Dynamic characteristics and admittances for the space shuttle model are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-150358 , D180-20572-2-VOL-2
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  • 77
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    Minimum-mass design of filamentary composite panels under combined loads: Design procedure based on a rigorous buckling analysis (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A procedure is presented for designing uniaxially stiffened panels made of composite material and subjected to combined inplane loads. The procedure uses a rigorous buckling analysis and nonlinear mathematical programing techniques. Design studies carried out with the procedure consider hat-stiffened and corrugated panels made of graphite-epoxy material. Combined longitudinal compression and shear and combined longitudinal and transverse compression are the loadings used in the studies. The capability to tailor the buckling response of a panel is also explored. Finally, the adequacy of another, simpler, analysis-design procedure is examined.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-8417 , L-11143
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  • 78
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    Method for measuring biaxial stress in a body subjected to stress inducing loads (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A method is described for measuring stress in test articles including the steps of obtaining for a calibrating specimen a series of transit time differentials between the second wave echo for a longitudinal wave and the first wave echo for each of a pair of shear waves propagated through the specimen as it is subjected to known stress load of a series of stress loads for thus establishing a series of indications of the magnitudes for stress loads induced in the specimen, and thereafter obtaining a transit time differential between the second wave echo for a longitudinal wave and the first wave echo for each of a pair of shear waves propagated in the planes of the stress axes of a test article and comparing the transit time differential thus obtained to the series of transit time differentials obtained for the specimen to determine the magnitude of biaxial stress in the test article.
    Keywords: STRUCTURAL MECHANICS
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  • 79
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    Mode I analysis of a cracked circular disk subject to a couple and a force (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Mode 1 stress intensity coefficients were obtained for an edge-cracked disk (round compact specimen). Results for this plane elastostatic problem, obtained by a boundary collocation analysis are presented for ratios 0.35 less than A/D less than 1, where A is the crack length and D is the disk diameter. The results presented are for two complementary types of loading. By superposition of these results the stress intensity factor K sub I for any practical load line location of a pin-loaded round compact specimen can be obtained.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-73692 , E-9228
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  • 80
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    A study of the effect of radical load distributions on calibrated strain gage load equations (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: For several decades, calibrated strain gages have been used to measure loads on airplanes. The accuracy of the equations used to relate the strain gage measurements to the applied loads has been based primarily on the results of the load calibration. An approach is presented for studying the effect of widely varying load distributions on strain gage load equations. The computational procedure provides a link between the load calibration and the load to be measured in flight. A matrix approach to equation selection is presented, which is based on equation standard error, load distribution, and influence coefficient plots of the strain gage equations, and is applied to a complex, delta-wing structure.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-56047 , H-984
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  • 81
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    The use of a simplified structural model as an aid in the strain gage calibration of a complex wing (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The use of a relatively simple structural model to characterize the load responses of strain gages located on various spars of a delta wing is examined. Strains measured during a laboratory load calibration of a wing structure are compared with calculations obtained from a simplified structural analysis model. Calculated and measured influence coefficient plots that show the shear, bending, and torsion characteristics of typical strain gage bridges are presented. Typical influence coefficient plots are shown for several load equations to illustrate the derivation of the equations from the component strain gage bridges. A relatively simple structural model was found to be effective in predicting the general nature of strain distributions and influence coefficient plots. The analytical processes are shown to be an aid in obtaining a good load calibration. The analytical processes cannot, however, be used in lieu of an actual load calibration of an aircraft wing.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-56046 , H-959
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  • 82
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    Evaluation of coated columbium alloy heat shields for space shuttle thermal protection system application (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A three-phase program to develop and demonstrate the feasibility of a metallic heat shield suitable for use on Space Shuttle Orbiter class vehicles at operating surface temperatures of up to 1590 K (2400 F) is summarized. An orderly progression of configuration studies, material screening tests, and subscale structural tests was performed. Scale-up feasibility was demonstrated in the final phase when a sizable nine-panel array was fabricated and successfully tested. The full-scale tests included cyclic testing at reduced air pressure to 1590 K (2400 F) and up to 158 dB overall sound pressure level. The selected structural configuration and design techniques succesfully eliminated thermal induced failures. The thermal/structural performance of the system was repeatedly demonstrated. Practical and effective field repair methods for coated columbium alloys were demonstrated. Major uncertainties of accessibility, refurbishability, and durability were eliminated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2824 , CASD-NAS-76-056
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  • 83
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    Investigation of Kevlar fabric-based materials for use with inflatable structures (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Design, manufacture and testing of laminated and coated composite materials incorporating a structural matrix of Kevlar are reported. The practicality of using Kevlar in aerostat materials is demonstrated, and data are provided on practical weaves, lamination and coating particulars, rigidity, strength, weight, elastic coefficients, abrasion resistance, crease effects, peel strength, blocking tendencies, helium permeability, and fabrication techniques. Properties of the Kevlar-based materials are compared with conventional Dacron-reinforced counterparts. A comprehensive test and qualification program is discussed, and considerable quantitative biaxial tensile and shear test data are provided.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2724
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  • 84
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    Probabilistic fracture mechanics and optimum fracture control of the solid rocket motor case of the shuttle (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Development of a procedure for the reliability analysis of the solid rocket motor case of the space shuttle is described. The analysis is based on probabilistic fracture mechanics and consideration of a probability distribution for the initial flaw sizes. The reliability analysis can be used to select design variables, such as the thickness of the SRM case, projected design life and proof factor, on the basis of minimum expected cost and specified reliability bounds. Effects of fracture control plans such as the non-destructive inspections and the material erosion between missions can also be considered in the developed methodology for selection of design variables. The reliability-based procedure can be easily modified to consider other similar structures and different fracture control plans.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-2790 , E-16-646
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  • 85
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    Statistical distribution of time to crack initiation and initial crack size using service data (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Crack growth inspection data gathered during the service life of the C-130 Hercules airplane were used in conjunction with a crack propagation rule to estimate the distribution of crack initiation times and of initial crack sizes. A Bayesian statistical approach was used to calculate the fraction of undetected initiation times as a function of the inspection time and the reliability of the inspection procedure used.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-145181
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    Influence of temperature change on optimum laminate design (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results of a laminate optimization study, which includes prescribed temperature change and mechanical loading conditions, are presented. Minimum-weight designs for balanced symmetric laminates are obtained subject to strength, membrane stiffness, and minimum thickness requirements, while including and omitting temperature change effects. Based on a first ply failure design philosophy and employing a linear thermoelastic analysis, it is shown that taking temperature decrease effects into account leads to substantial weight penalties in strength critical fiber composite laminates. Numerical results are presented for representative fiber composite materials based on three commonly used combined stress failure criteria.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 15; Sept
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  • 87
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    A study of fatigue crack closure using electric potential and compliance techniques (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The objective of this study was to compare closure data obtained on the same specimen with crack tip compliance gage and electric potential techniques. Equivalent results on closure using the two techniques were obtained on 7075-T651 aluminum center cracked panels. The results also indicated that closure was a function of stress ratio, specimen thickness and maximum applied stress intensity. Maximum stress intensity had a particularly strong effect on closure in the range of applied stresses used. This observed dependence of closure on specimen thickness and maximum stress intensity should account for many of the discrepancies in closure behavior found in the literature. Observations on potential system behavior during closure measurements are also reported.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 9; 3, 19; 1977
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  • 88
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    Mixed isoparametric finite element models of laminated composite shells (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Mixed shear-flexible isoparametric elements are presented for the stress and free vibration analysis of laminated composite shallow shells. Both triangular and quadrilateral elements are considered. The 'generalized' element stiffness, consistent mass, and consistent load coefficients are obtained by using a modified form of the Hellinger-Reissner mixed variational principle. Group-theoretic techniques are used in conjunction with computerized symbolic integration to obtain analytic expressions for the stiffness, mass and load coefficients. A procedure is outlined for efficiently handling the resulting system of algebraic equations. The accuracy of the mixed isoparametric elements developed is demonstrated by means of numerical examples, and their advantages over commonly used displacement elements are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Methods in Applied Mechanics and Engineering; 11; June-Jul
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  • 89
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    Stress-intensity factors for cracks emanating from the loaded fastener hole (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Using a series approach and the Muskhelishvili formulation in the two-dimensional theory of elasticity, stress-intensity factors K are derived for problems in which cracks emanate radially from the boundary of an arbitrarily loaded internal circular hole in an infinite plate. Numerical values are obtained for K(I) and K(II) for radial cracks from a hole containing a loose-fitted pin or rivet that is pulled perpendicular to the crack direction in the plane of the plate. The method is a general one for determining K for a set of symmetrically emanating radial cracks for a variety of concentrated or distributed tractions on the circular hole.
    Keywords: STRUCTURAL MECHANICS
    Type: International Conference on Fracture Mechanics and Technology; Mar 21, 1977 - Mar 25, 1977; Hong Kong
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  • 90
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    Stress intensity estimates by a computer assisted photoelastic method (1977)
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    Publication Date: 2019-07-13
    Description: Following an introductory history, the frozen stress photoelastic method is reviewed together with analytical and experimental aspects of cracks in photoelastic models. Analytical foundations are then presented upon which a computer assisted frozen stress photoelastic technique is based for extracting estimates of stress intensity factors from three-dimensional cracked body problems. The use of the method is demonstrated for two currently important three-dimensional crack problems.
    Keywords: STRUCTURAL MECHANICS
    Type: International Conference on Fracture Mechanics and Technology; Mar 21, 1977 - Mar 25, 1977; Hong Kong
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  • 91
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    Biaxial load effects in fracture mechanics (1977)
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    Publication Date: 2019-07-13
    Description: It is found that the standard expressions for elastic stress and displacement in the crack-tip region (i.e., the so-called singular solution) cannot be considered to be approximations that are acceptable in a completely general sense. This conclusion is best illustrated by the instance of a biaxially loaded infinite sheet with a flat horizontal central crack, where the effect of load applied parallel to the plane of the crack appears entirely in the second terms of the series representations for local stresses and displacements. An elastoplastic finite-element analysis of the same biaxially loaded finite specimen geometry shows that the global energy release rate, the J-integral, the plastic stress and strain intensity factors (in the sense of Hilton and Hutchinson), and the size of the crack border region plastic yield, all have pronounced biaxial load dependence.
    Keywords: STRUCTURAL MECHANICS
    Type: International Conference on Fracture Mechanics and Technology; Mar 21, 1977 - Mar 25, 1977; Hong Kong
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  • 92
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    Nonlinear panel flutter - A finite-element approach (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A finite-element approach has been developed for computing nonlinear flutter characteristics of rectangular isotropic panels with stream-alined side edges, based on aerodynamic forces from supersonic two-dimensional quasi-steady aerodynamic theory. Stress distributions and panel oscillation frequencies were determined from the analysis. The finite-element formulation, solution procedure, and convergence characteristics are presented. Comparisons are made with linear flutter and large-amplitude vibration results and demonstrate that good accuracy is obtained. Non-linear flutter results are presented for effects of aerodynamic damping, length-width ratio, initial in-plane forces and boundary-support conditions. Comparisons with experimental results are also presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Winter Annual Meeting; Nov 27, 1977 - Dec 02, 1977; Atlanta, GA
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  • 93
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    Vibrations of incompressible liquid-plastic tank combinations using a series representation of the liquid (1977)
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    Publication Date: 2019-07-13
    Description: A series representation is presented of the dynamic behavior of incompressible non-viscous liquids contained in partially filled elastic shells of revolution. Using a series in which each term satisfies exactly Laplace's equation, the liquid portion of the problem becomes an integral equation on the wetted wall of the shell. Physical insight required in selecting the terms of the series is such that selection may be readily programed on a computer. Liquid-shell vibration interaction is investigated by modifying an existing shell of revolution vibration program with the series expansion of the liquid pressure loading on the wetted shell wall. Application of the modified program is demonstrated on a hemispherical tank and a realistic scaled model of a launch vehicle tank having a more complex geometry. Comparison of the present analysis with a NASTRAN finite element analysis for a hemispherical tank, and comparison with test results for a launch vehicle tank shows excellent agreement and rapid convergence of the series representation of the liquid to the true solution.
    Keywords: STRUCTURAL MECHANICS
    Type: Winter Annual Meeting; Nov 27, 1977 - Dec 02, 1977; Atlanta, GA
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  • 94
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    Finite-element analysis of crack growth under monotonic and cyclic loading (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An elastic-plastic (incremental) finite-element analysis, in conjunction with a crack-growth criterion, was used to study crack-growth behavior under monotonic and cyclic loading. The crack-growth criterion was based on crack-tip strain. Whenever the crack-tip strain equals or exceeds a critical strain value, the crack grows. The effects of element-mesh size, critical strain, strain hardening, and specimen type (tension or bending) on crack growth under monotonic loading were investigated. Crack growth under cyclic loading (constant amplitude and simple variable amplitude) were also studied. A combined hardening theory, which incorporates features of both isotropic and kinematic hardening under cyclic loading, was also developed for smooth yield surfaces and was used in the analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: Cyclic stress-strain and plastic deformation aspects of fatigue crack growth; May 02, 1976 - May 08, 1976; St. Louis, MO
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  • 95
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    Response of periodic beam to supersonic boundary-layer pressure fluctuations (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The response of a periodic beam (modeling a periodic fuselage) to supersonic boundary-layer pressure fluctuations is analyzed on the basis of a scheme in which a decaying turbulence is treated as a superposition of frozen-pattern components, thus allowing the structural response to be similarly superposed and the advantage of frozen-pattern analysis to be maximally utilized. The fundamental solution required for the construction of the total response is one corresponding to the excitation of a frozen-pattern sinusoid. To obtain this fundamental solution, the formulation follows Mead's wave-propagation method (1971), but also takes into account the effect of freestream velocity on the same side of the turbulence excitation and the effect of a cavity on the opposite side of the excitation. As a numerical example, the spectral density of the structural response is computed and the results are compared with experimental data.
    Keywords: STRUCTURAL MECHANICS
    Type: Symposium on Stochastic problems in dynamics; Jul 19, 1976 - Jul 23, 1976; Southampton
    Format: text
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  • 96
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    Stress intensities for cracks emanating from pin-loaded holes (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A series of stress freezing photoelastic experiments were conducted on large plates containing central holes with cracks emanating from the edge formed by the intersection of the hole with the plate surface. Loads were applied through rigid pins with neat fits in the holes. Stress-intensity factors (SIF) were estimated by a computer assisted least squares analysis of the photoelastic data taken from slices near the points of intersection of the flaw border with the hole boundary and the plate surface. Results indicate that the local mode of loading changes from Mode 1 near the hole boundary to mixed mode near the plate surface. The analysis is extended to include mixed mode loading, and results are compared with an existing approximate theory.
    Keywords: STRUCTURAL MECHANICS
    Type: National Symposium on Fracture Mechanics; Aug 23, 1976 - Aug 25, 1976; Philadelphia, PA
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  • 97
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    The use of parabolic variations and the direct determination of stress intensity factors using the BIE method (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Two advances in the numerical techniques of utilizing the BIE method are presented. The boundary unknowns are represented by parabolas over each interval which are integrated in closed form. These integrals are listed for easy use. For problems involving crack tip singularities, these singularities are included in the boundary integrals so that the stress intensity factor becomes just one more unknown in the set of boundary unknowns thus avoiding the uncertainties of plotting and extrapolating techniques. The method is applied to the problems of a notched beam in tension and bending, with excellent results.
    Keywords: STRUCTURAL MECHANICS
    Type: Symposium on Applications of Computer Methods in Engineering; Aug 23, 1977 - Aug 26, 1977; Los Angeles, CA
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  • 98
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    Development of procedures for calculating stiffness and damping properties of elastomers in engineering applications. Part 4: Testing of elastomers under a rotating load (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A test rig designed to measure stiffness and damping of elastomer cartridges under a rotating load excitation is described. The test rig employs rotating unbalance in a rotor which runs to 60,000 RPM as the excitation mechanism. A variable resonant mass is supported on elastomer elements and the dynamic characteristics are determined from measurements of input and output acceleration. Five different cartridges are considered: three of these are buttons cartridges having buttons located in pairs, with 120 between each pair. Two of the cartridges consist of 360 elastomer rings with rectangular cross-sections. Dynamic stiffness and damping are measured for each cartridge and compared with predictions at different frequencies and different strains.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-135355 , MTI-78TR18-PT-4
    Format: application/pdf
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  • 99
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    Stiffness and damping of elastomeric O-ring bearing mounts (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A test rig to measure the dynamic stiffness and damping of elastomer O rings was described. Test results for stiffness and loss coefficient in the frequency range from 50 Hz to 1000 Hz are presented. Results are given for three different materials, for five temperatures, for three amplitudes, for five values of squeeze for three values of stretch for three values of cross-section diameter and for three values of groove width. All test data points were plotted. In addition, trend summary plots were presented which compare the effect of material, temperature, amplitude, squeeze, stretch, cross-section diameter, and groove width. O ring deflections under a static load for different material were presented; and effective static stiffness values were compared with dynamic values.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-135328 , MTI-78TR17
    Format: application/pdf
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  • 100
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    An Integrated Theory for Predicting the Hydrothermomechanical Response of Advanced Composite Structural Components (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An integrated theory is developed for predicting the hydrothermomechanical (HDTM) response of fiber composite components. The integrated theory is based on a combined theoretical and experimental investigation. In addition to predicting the HDTM response of components, the theory is structured to assess the combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and those of angleplied laminates. The theory developed predicts values which are in good agreement with measured data at the micromechanics, macromechanics, laminate analysis and structural analysis levels.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-73812 , E-9372 , Tech. Specialists Conf. on Environ. Effects on Advanced Composite Mater.; Sep 29, 1977 - Sep 30, 1977; Dayton, OH; United States
    Format: application/pdf
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