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  • Other Sources  (23)
  • Structural Mechanics
  • 1960-1964  (15)
  • 1940-1944  (8)
  • 1
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    Probability Functions for Random Responses: Prediction of Peaks, Fatigue Damage, and Catastrophic Failures (1964)
    In:  CASI
    Details
    Publication Date: 2019-05-21
    Description: This report reviews a number of theoretical matters in random process theory which can be applied to physical problems such as predicting peaks, structural fatigue damage, and catastrophic structural failures. The presentation emphasizes the basic assumptions which are involved, and discusses how to properly interpret the theoretical results. Various engineering examples are given as illustrations.
    Keywords: Structural Mechanics
    Type: NASA-CR-33
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  • 2
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    Vibration of Thin Circular Rings. Part II. Modal Functions and Eigenvalues of Constrained Semicircular Rings (1963)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: The equations of motion of thin circular rings are derived and solved for in-plane in-extensional deformation. Modal characteristics are tabulated for the five lowest flexural modes of vibration of semicircular ring segments for the possible combinations of homogeneous boundary conditions that can occur.
    Keywords: Structural Mechanics
    Type: JPL-TR-32-261
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  • 3
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    Experimental Studies of Flutter of Buckled Rectangular Panels at Mach Numbers from 1.2 to 3.0 Including Effects of Pressure Differential and of Panel Width-Length Ratio (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: Experimental panel flutter data have been obtained at Mach numbers from 1.2 to 3.0 for buckled rectangular panels and the effect of a pressure differential has been determined. Increasing the pressure differential was effective in eliminating flutter on most of the panels tested. The effects of the variables in the panel flutter parameter ((square root of m(exp 2) -1) * (E/q))(exp 1/3) t/l (where M is the Mach number, q is the dynamic pressure, E is Young's modulus, and t and l are the panel thickness and length, respectively) were investigated for buckled panels clamped on the front and rear edges and a critical value of this parameter of 0.44 is indicated at zero pressure differential when the panel width-length ratio is 0.69. An estimated flutter boundary is presented for buckled panels clamped on four edges, with width-length ratios of 0.21 to 4.0. This boundary shows that the panel width is more significant than the panel length when the ratio of width to length is less than approximately 0.5. Panels clamped on four edges and buckled in two half waves in the direction of flow were found to be particularly susceptible to flutter. The results of limited tests on panels with applied damping, curvature, and lengthwise stiffeners are also presented and discussed.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-833 , L-1542
    Format: text
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  • 4
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    The Use of Higher-Order Difference Methods in Beam Vibration Analysis (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: Simple and higher-order difference methods for the solution for the natural frequencies of vibration of a uniform beam are compared. The same basic higher-order method is used throughout for the interior cells, but three different methods of boundary-condition representation are given. Tables and graphs of the error in mode frequencies, as compared with a continuous beam, are given for the various methods as a function of the number of cells. It is concluded that higher-order methods improve accuracy for a given number of cells, with essentially no change in the quantity of computing equipment required.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-964
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  • 5
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    Stress Concentrations in Filamentary Structures (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Theoretical analyses are made of the stress distributions in a sheet of parallel filaments which carry normal loads and are imbedded in a matrix which carries only shear. In all cases, uniform loading at infinity is assumed and small-deflection elasticity theory is used. Static and dynamic stress-concentration factors due to one or more filaments being broken are determined. Particular attention is paid the dynamic overshoot resulting when the filaments are suddenly broken. The dynamic-response factor increases from 1.15 to 1.27 as the number of broken filaments is increased from one to infinity. A somewhat lower dynamic-response factor is obtained when a hole is suddenly caused in the filament sheet.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-882 , L-1502
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  • 6
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    A Linear Theory for Inflatable Plates of Arbitrary Shape (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A linear small-deflection theory is developed for the elastic behavior of inflatable plates of which Airmat is an example. Included in the theory are the effects of a small linear taper in the depth of the plate. Solutions are presented for some simple problems in the lateral deflection and vibration of constant-depth rectangular inflatable plates.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-930 , L-919
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  • 7
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    Fatigue Investigation of Full-Scale Wing Panels of 7075 Aluminum Alloy (1961)
    In:  CASI
    Details
    Publication Date: 2019-10-31
    Description: Results are presented of a fatigue investigation conducted using 18 outer wing panels of T-29A airplanes. Constant-amplitude tests were performed using the resonant-frequency method at three different alternating load levels superposed on a 1 g, or level-flight mean load. Information is presented concerning crack location, cycles to crack initiation, crack propagation, and residual static strength.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-635
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  • 8
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    Theoretical Elastic Stress Distributions Arising from Discontinuities and Edge Loads in Several Shell-Type Structures (1961)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The deformation and complete stress distribution are determined for each of the following edge loaded thin shells of revolution: (1) a right circular cylinder, (2) a frustum of a right circular cone, and (3) a portion of a sphere. The locations of the maximum circumferential and meridional stresses on both the inner and outer surfaces are also found. The basic equations for the above were selected from the published literature on the subject and expanded to produce to resultant-stress equations in closed from where practicable to do so. Equations are also developed for the discontinuity shear force and bending moment at each of the following junction: (1) axial change of thickness in a circular cylinder, (2) axial change of thickness in a cone, (3) change of thickness in a portion of a sphere, (4) a cylinder and a cone, (5) a cylinder and a portion of a sphere(6) a cylinder and a flat head, and (7) a cone and a portion of a sphere.
    Keywords: Structural Mechanics
    Type: NASA-TR-R-103
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  • 9
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    The General Equations of Equilibrium of Rotationally Symmetric Membranes and some Static Solutions for Uniform Centrifugal Loading (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: The general equations of equilibrium of a rotationally symmetrical body undergoing large arbitrary deflections but small strains are derived by means of the principle of virtual work. All deflections are referred to a reference surface which, in general, may be taken to coincide with any intermediate state of the membrane. Static solutions of the general equations for steadily rotating membranes are considered for the cases in which the final or the initial configuration of the membrane is specified. For problems in which the final configuration is specified, conditions are given under which such a configuration is obtainable from a stress-free initial state. Such conditions being satisfied, it is shown that the stresses and radial displacements are determinate while axial displacements may be obtained by quadrature. For problems in which the initial configuration is given, the determination of the stresses and deflections is reduced to the solution of a second-order nonlinear differential equation for a stress function. An approximate method of solution based on boundary-layer considerations is presented for the case of a spinning sphere of constant thickness. Specific examples are given for both classes of problems.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-816 , L-722
    Format: text
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  • 10
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    Tensile Properties of 17-7 PH and 12 MoV Stainless-Steel Sheet under Rapid-Heating and Constant-Temperature Conditions (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Results are presented of rapid-heating tests of 17-7 PH and 12 MoV stainless-steel sheet heated to failure at temperature rates from about 1 F to 170 F per second under constant-load conditions. Yield and rupture strengths obtained from rapid-heating tests are compared with yield and tensile strengths obtained from short-time elevated-temperature tensile tests (30-minute exposure). A rate-temperature parameter was used to construct master curves from which yield and rupture stresses or temperatures can be predicted. A method for measuring strain by optical means is described.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-823 , L-1313
    Format: text
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  • 11
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    Cross-Sectional Deformations of Monocoque Beams and Their Effects on the Natural Vibration Frequencies (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: The variational principle, differential equations, and boundary conditions governing the cross-sectional distortions due to inertia loading of a two-dimensional model of a thin monocoque wing are shown. A theoretical analysis of this simplified model is made in order to determine the nature of the coupling between the cross-sectional modes and the spanwise deformation modes. General solutions are obtained in finite-difference form for arbitrary cross sections and an exact solution is presented for a parabolic-arc cross section of constant cover thickness. The application of these results in evaluating the coupled frequencies of the actual structure is discussed. Frequencies evaluated for a parabolic-arc monocoque beam show good agreement with experimental values.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-987 , L-1444
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  • 12
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    Experimental Investigation at Mach Number 3.0 of the Effects of Thermal Stress and Buckling on the Flutter of Four-Bay Aluminum Alloy Panels with Length-Width Ratios of 10 (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Skin-stiffener aluminum alloy panels consisting of four bays, each bay having a length-width ratio of 10, were tested at a Mach number of 3.0 at dynamic pressures ranging from 1,500 psf to 5,000 psf and at stagnation temperatures from 300 F to 655 F. The panels were restrained by the supporting structure in such a manner that partial thermal expansion of the skins could occur in both the longitudinal and lateral directions. A boundary faired through the experimental flutter points consisted of a flat-panel portion, a buckled-panel portion, and a transition point at the intersection of the two boundaries. In the region where a panel must be flat when flutter occurs, an increase in panel skin temperature (or midplane compressive stress) makes the panel more susceptible to flutter. In the region where a panel must be buckled when flutter occurs, the flutter trend is reversed. This reversal in trend is attributed to the panel postbuckling behavior.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-921 , L-1265
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  • 13
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    Skin Stresses in an Inflated Sphere During Impact (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: An analysis is made of the stresses in the skin of an inflated nonstretchable sphere during normal, nonrotating impact with a hard flat surface, assuming infinite modulus of elasticity in the skin and infinite propagation speed of stress waves. The analysis is further applied to the study of the inflated sphere landing vehicle containing a payload suspended at the center. Curves are presented showing the stress distributions during impact for cases corresponding to those calculated in previous reports in which the impact motion and payload landing performance capabilities of the landing vehicle have been studied. It is found, assuming the force from the payload-suspension cords to be distributed continuously on the skin, that is, neglecting stress concentrations,that the skin stresses along a meridian are reduced by the presence of the suspended payload during impact, but that the maximum values of skin stress normal to a meridian are little affected.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-1070 , A-471
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  • 14
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    Effects of Changing Stress Amplitude on the Rate of Fatigue-Crack Propagation in Two Aluminum Alloys (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: A series of fatigue tests with specimens subjected to constant amplitude and two-step axial loads were conducted on 12-inch-wide sheet specimens of 2024-T3 and 7075-T6 aluminum alloy to study the effects of a change in stress level on fatigue-crack propagation. Comparison of the results of the tests in which the specimens were tested at first a high and then a low stress level with those of the constant-stress- amplitude tests indicated that crack propagation was generally delayed after the transition to the lower stress level. In the tests in which the specimens were tested at first a low and then a high stress level, crack propagation continued at the expected rate after the change in stress levels.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-960 , L-1340
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  • 15
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    Correlation of the Buckling Strength of Pressurized Cylinders in Compression or Bending with Structural Parameters (1960)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: The data on nonpressurized cylinders in bending of NACA TN 3735 and the data on pressurized cylinders in compression and bending of NASA TN D-360 are correlated with structural parameters by using small-deflection buckling theory and reduced values for the extensional stiffness of the cylinder wall. The correlating procedure should prove useful in future shell-buckling investigations by reducing the number of tests required.
    Keywords: Structural Mechanics
    Type: NASA-TN-D-526 , L-1158
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  • 16
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    Compressive Strength of Flat Panels with Z- and Hat-Section Stiffeners (1944)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Compression tests were conducted on 247 panels with Z-section stiffeners and 304 panels with hat-section stiffeners. Specimens were constructed from artificially aged Alclad 24S aluminum alloy with minimum guaranteed yield strengths of 64 and 57 ksi for stiffeners and sheet materials, respectively. Height, thickness, and spacing of stiffeners, sheet thickness, and length of specimens were varied systematically to show effects of changes in these dimensions on panel strength. Results show average stresses at buckling load and maximum load.
    Keywords: Structural Mechanics
    Type: NACA-WR-L-62 , NACA-ARR-L4F01
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  • 17
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    Bending of Rectangular Plates with Large Deflections (1942)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The solution of von Karman's fundamental equations for large deflections of plates is presented for the case of a simply supported rectangular plate under combined edge compression and lateral loading. Numerical solutions are given for square plates and for rectangular plates with a width-span ratio of 3:1. The effective widths under edge compression are compared with effective widths according to von Karman, Bengston, Marguerre, and Cox and with experimental results by Ramberg, McPherson, and Levy. The deflections for a square plate under lateral pressure are compared with experimental and theoretical results by Kaiser. It is found that the effective widths agree closely with Marguerre's formula and with the experimentally observed values and that the deflections agree with the experimental results and with Kaiser's work.
    Keywords: Structural Mechanics
    Type: NACA-TN-846
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  • 18
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    Restraint Provided a Flat Rectangular Plate by a Sturdy Stiffener Along an Edge of the Plate (1942)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A sturdy stiffener is defined as a stiffener of such proportions that it does not suffer cross-sectional distortion when moments are applied to some part of the cross section. When such a stiffener is attached to one edge of a plate, it will resist rotation of that edge of the plate by means of its torsional properties. A formula is given for the restraint coefficient provided the plate by such a stiffener. This coefficient is required for the calculation of the critical compressive stress of the plate.
    Keywords: Structural Mechanics
    Type: NACA-TR-735
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  • 19
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    A Flush-Rivet Milling Tool (1942)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The investigation of machine-countersunk flush rivets for aircraft described in reference 1 revealed the necessity of having the height of the rivet heads greater than the depth of the countersunk holes if tightly riveted joints were to be obtained. If ordinary roundhead rivets were inserted from the opposite side of the joint and the countersunk heads formed in the driving of the rivets filled the countersunk holes completely, still tighter joints were obtained. In either case the rivets protruded above the skin surface after driving, and the protruding portion of the rivet heads had to be removed in order to obtain flush rivets. A number of requests have been received for a description of the tool used to mill off the protruding portion of the rivet heads. This report contains assembly and detail drawings of the latest flush-rivet milling tool used at the NACA Structures Research Laboratory. Figure 6 shows the tool in operation. This tool is quite satisfactory for 1/8-inch rivets, but a more powerful motor is recommended for use with larger rivets.
    Keywords: Structural Mechanics
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  • 20
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    Data on Compressive Strength of Flat Panels with Z-Section Stiffeners (1942)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A comprehensive series of compression tests on skin-stiffener panels with Z-section stiffeners formed from flat sheet is being made in order to show the importance of the relative dimensions in determining the strength of the panels. The results obtained to date in this investigation are presented in this report.
    Keywords: Structural Mechanics
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  • 21
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    Stress Analysis of Circular Frames (1941)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The stresses in circular frames of constant bending stiffnesses, as encountered in thin-wall shells, are investigated from the point of view of finite depth of sectional area of frame. The solution is carried out for four fundamental load conditions. The method is illustrated on a worked out example.
    Keywords: Structural Mechanics
    Type: NACA-TM-999
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  • 22
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    Restraint Provided a Flat Rectangular Plate by a Sturdy Stiffener Along an Edge of the Plate, Special Report (1941)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A sturdy stiffener is defined as a stiffener of such proportions that it does not suffer cross-sectional distortion when moments are applied to some part of the cross section. When such a stiffener is attached to one edge of a plate, it will resist rotation of that edge of the plate by means of its torsional properties. A formula is given for the restraint coefficient provided the plate by such a stiffener. This coefficient is required for the calculation of the critical compressive stress of the plate.
    Keywords: Structural Mechanics
    Type: NACA-SR-190
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  • 23
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    The Effect of Initial Displacement of the Center Support on the Buckling of a Column Continuous over Three Supports (1940)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The test indicate that "an indiscriminate single application of the Southwell method (for analyzing Exp. Observations in problems of elastic stability)--can result in definite and measurable errors" The test also indicate "that the effect of curvature due to bending on the critical load for the compression flange material of a box beam is probably small and can be neglected." We have not found this to be true in our tests. It is believed that the effect of curvature, together with a small amount of fixity at the ribs, tends to force the stiffeners to bow in each bay thus effectively increasing their end fixity and thereby raising their allowable loads.
    Keywords: Structural Mechanics
    Type: NACA-SR-166
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