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Investigation of Rim Cracking in Turbine Wheels with Welded Blades

Description: Rim cracking in turbine wheels with welded blades was evaluated. The problem is explained on the basis of the occurrence of plastic flow in the rim during transient starting conditions when thermal compressive stresses resulting from high-temperature gradients exceed the proportional elastic limit of the material.
Date: February 12, 1947
Creator: Millenson, M. B. & Manson, S. S.
Partner: UNT Libraries Government Documents Department

Bending and shear stresses developed by the instantaneous arrest of the root of a moving cantilever beam

Description: A theoretical and experimental investigation has been made of the behavior of a cantilever beam in transverse motion when its root is suddenly brought to rest. Equations are given for determining the stresses, the deflections, and the accelerations that arise in the beam as a result of the impact. The theoretical equations, which have been confirmed experimentally, reveal that, at a given percentage of the distance from root to tip, the bending stresses for a particular mode are independent of the length of the beam, whereas the shear stresses vary inversely with the length.
Date: September 27, 1944
Creator: Stowell, Elbridge Z.; Schwartz, Edward B. & Houbolt, John C.
Partner: UNT Libraries Government Documents Department

Comparison of measured and calculated stresses in built-up beams

Description: Web stresses and flange stresses were measured in three built-up beams: one of constant depth with flanges of constant cross-section, one linearly tapered in depth with flanges of constant cross section, and one linearly tapered in depth with tapered flanges. The measured stresses were compared with the calculated stresses obtained by the methods outlined in order to determine the degree of accuracy that may be expected from the stress analysis formulas. These comparisons indicated that the average measured stresses for all points in the central section of the beams did not exceed the average calculated stresses by more than 5 percent. It also indicated that the difference between average measured flange stresses and average calculated flange stresses on the net area and a fully effective web did not exceed 6.1 percent.
Date: May 1946
Creator: Levin, L. Ross & Nelson, David H.
Partner: UNT Libraries Government Documents Department

Tests of 10 inch 24S-T aluminum-alloy shear panels with 1-1/2 inch holes 2 : panels having holes with notched edges

Description: Report discusses the results of testing of 10-inch 24S-T aluminum alloy shear panels with 1.5 inch holes with notched edges to determine if a notch decreases the strength of the panel and if reinforcements can overcome the negative effects of the notch. The notch did appear to increase the stress concentration around the holes, but the lack of applicability to real-world scenarios is discussed.
Date: April 1944
Creator: Kuhn, Paul & Levin, L. Ross
Partner: UNT Libraries Government Documents Department

The problem of thermal-expansion stresses in reinforced plastics

Description: Report presenting an analysis of the failure of adhesive bonds and its relation to boundary stress concentrations. A variety of material combinations, including metals and plastics, were examined and stress tested. The method of computing the thermal coefficients is applied to mixtures and especially to reinforced plastics.
Date: June 1942
Creator: Turner, P. S.
Partner: UNT Libraries Government Documents Department

Statistical analysis of the time and fatigue strength of aircraft wing structures

Description: The results from stress measurements in flight operation afford data for analyzing the frequency of appearance of certain parts of the static breaking strength during a specified number of operating hours. Appropriate frequency evaluations furnish data for the prediction of the required strength under repeated stress in the wing structures of aircraft of the different stress categories for the specified number of operating hours demanded during the life of a component.
Date: October 1941
Creator: Kaul, Hans W.
Partner: UNT Libraries Government Documents Department

A study of elastic and plastic stress concentration factors due to notches and fillets in flat plates

Description: Report presenting testing on six large 24S-T3 aluminum alloy sheet specimens containing various notches and fillets to determine their stress concentration factors in the elastic and plastic ranges. Results regarding elastic stress concentration factors, plastic stress concentration factors, a suggested formula, and stress and strain distributions are provided.
Date: December 1951
Creator: Hardrath, Herbert F. & Ohman, Lachlan
Partner: UNT Libraries Government Documents Department

A study of elastic and plastic stress concentration factors due to notches and fillets in flat plates

Description: Six large 24s-t3 aluminum-alloy-sheet specimens containing various notches or fillets were tested in tension to determine their stress concentration factors in both the elastic and plastic ranges. The elastic stress concentration factors were found to be slightly higher than those calculated by Neuber's method and those obtained photoelastically by Frocht. The results showed further that the stress concentration factor decreases as strains at the discontinuity enter the plastic range. A generalization of Stowell's relation for the plastic stress concentration factor at a circular hole in an infinite plate was applied to the specimen shapes tested and gave good agreement with test results.
Date: September 7, 1951
Creator: Hardrath, Herbert F. & Ohman, Lachlan
Partner: UNT Libraries Government Documents Department

Statistical analysis of service stresses in aircraft wings

Description: On the wing structures of modern high speed aircraft, in particular, the comparatively high-service stresses and the consistently increasing number of hours of operation during the life of the separate airplane parts make the studies of strength requirement under recurrent stresses appear of major concern. The DVL has therefore made exhaustive studies for this structural group of airplanes, some results of which are reported here.
Date: June 1942
Creator: Kaul, Hans W.
Partner: UNT Libraries Government Documents Department

A unified theory of plastic buckling of columns and plates

Description: From Summary: "On the basis of modern plasticity considerations, a unified theory of plastic buckling applicable to both columns and plates has been developed. For uniform compression, the theory shows that long columns which bend without appreciable twisting require the tangent modulus and that long flanges which twist without appreciable bending require the secant modulus. Structures that both bend and twist when they buckle require a modulus which is a combination of the secant modulus and the tangent modulus."
Date: April 1948
Creator: Stowell, Elbridge Z.
Partner: UNT Libraries Government Documents Department

Bending and shear stresses developed by the instantaneous arrest of the root of a cantilever beam rotating with constant angular velocity about a transverse axis through the root

Description: From Summary: "A theoretical investigation was made of the behavior of a cantilever beam in rotational motion about a transverse axis through the root determining the stresses, the deflections, and the accelerations that occur in the beam as a result of the arrest of motion. The equations for bending and shear stress reveal that, at a given percentage of the distance from root to tip and at a given trip velocity, the bending stresses for a particular mode are independent of the length of the beam and the shear stresses vary inversely with the length. When examined with respect to a given angular velocity instead of a given tip velocity, the equations reveal that the bending stress is proportional to the length of the beam whereas the shear stress is independent of the length."
Date: June 1945
Creator: Stowell, Elbridge Z.; Schwartz, Edward B. & Houbolt, John C.
Partner: UNT Libraries Government Documents Department

Axial-load fatigue tests on notched and unnotched sheet specimens of 61S-T6 aluminum alloy, annealed 347 stainless steel, and heat-treated 403 stainless steel

Description: From Summary: "Axial-load fatigue tests at a stress ratio of zero were performed on notched and unnotched sheet specimens of 61S-T6 aluminum alloy and 347 and 403 stainless steels. Special emphasis was placed on tests at high stress levels which produce failures in small numbers of cycles."
Date: October 1953
Creator: Hardrath, Herbert F.; Landers, Charles B. & Utley, Elmer C., Jr.
Partner: UNT Libraries Government Documents Department

A special investigation to develop a general method for three-dimensional photoelastic stress analysis

Description: The method of strain measurement after annealing is reviewed and found to be satisfactory for the materials available in this country. A new general method is described for the photoelastic determination of the principal stresses at any point of a general body subjected to arbitrary load. The method has been applied to a sphere subjected to diametrical compressive loads. The results show possibilities of high accuracy.
Date: 1953
Creator: Frocht, M. M. & Guernsey, R., Jr.
Partner: UNT Libraries Government Documents Department

Stress and distortion analysis of a swept box beam having bulkheads perpendicular to the spars

Description: Report presenting a method for the approximate calculation of the stresses and distortions in a box beam representing the main structural component of a swept wing with a carry-through section and with bulkheads perpendicular to the spars. Results regarding determination of shear-leg effects, effect of bulkhead flexibility, and extension of the method are provided.
Date: November 1950
Creator: Heldenfels, Richard R.; Zender, George W. & Libove, Charles
Partner: UNT Libraries Government Documents Department

Torsion tests of a monocoque box

Description: Report presenting testing of a monocoque box of aluminum alloy, which had torques applied to the ends. The twist, strain in the stringers, plate, and corner posts, and the buckling load were measured. A new analysis was developed for the twisting of a monocoque box reinforced by stringers, corner posts, and bulkheads, and the measured twist agreed within 10 percent of the analytical value.
Date: November 1942
Creator: Levy, Samuel; McPherson, Albert E. & Ramberg, Walter
Partner: UNT Libraries Government Documents Department

An engineering method for estimating notch-size effect in fatigue tests on steel

Description: Neuber's proposed method of calculating a practical factor of stress concentration for parts containing notches of arbitrary size depends on the knowledge of a "new material constant" which can be established only indirectly. In this paper, the new constant has been evaluated for a large variety of steels from fatigue tests reported in the literature, attention being confined to stresses near the endurance limit. Reasonably satisfactory results were obtained with the assumption that the constant depends only on the tensile strength of the steel. Even in cases where the notches were cracks of which only the depth was known, reasonably satisfactory agreement was found between calculated and experimental factors. It is also shown that the material constant can be used in an empirical formula to estimate the size effect on unnotched specimens tested in bending fatigue.
Date: October 1952
Creator: Kuhn, Paul & Hardrath, Herbert F.
Partner: UNT Libraries Government Documents Department

Critical combinations of shear and transverse direct stress for an infinitely long flat plate with edges elastically restrained against rotation

Description: Report presenting an exact solution and a closely concurring approximate energy solution for the buckling of an infinitely long flat plate under combined shear and transverse direct stress with edges elastically restrained against rotation. An appreciable fraction of the critical stress in pure shear may be applied to the plate without any reduction in the transverse compressive stress necessary to produce buckling.
Date: January 1945
Creator: Batdorf, S. B. & Houbolt, John C.
Partner: UNT Libraries Government Documents Department

Critical combinations of shear and transverse direct stress for an infinitely long flat plate with edges elastically restrained against rotation

Description: An exact solution and a closely concurring approximate energy solution are given for the buckling of an infinitely long flat plate under combined shear and transverse direct stress with edges elastically restrained against rotation. It was found that an appreciable fraction of the critical stress in pure shear may be applied to the plate without any reduction in the transverse compressive stress necessary to produce buckling. An interaction formula in general use was shown to be decidedly conservative for the range in which it is supposed to apply.
Date: November 8, 1944
Creator: Batdorf, S. B. & Houbolt, John C.
Partner: UNT Libraries Government Documents Department

The Direct-Stress Fatigue Strength of 17S-T Aluminum Alloy Throughout the Range From 1/2 to 500,000,000 Cycles of Stress

Description: "Fatigue-tests were conducted on six specimens made from 3/4-inch-diameter 17S-T rolled-and-drawn rod for the purpose of obtaining additional data on the fatigue life of the material at stresses up to the static strength. The specimens were tested in direct tension using a stress range from zero to a maximum in tension. A static testing machine was used to apply repeated loads in the case of the first three specimens; the other three specimens were tested in a direct tension-compression fatigue machine" (p. 1).
Date: September 1942
Creator: Hartmann, E. C. & Stickley, G. W.
Partner: UNT Libraries Government Documents Department

Critical Combinations of Longitudinal and Transverse Direct Stress for an Infinitely Long Flat Plate With Edges Elastically Restrained Against Rotation

Description: Report presenting a theoretical investigation of the buckling of an infinitely long flat plate with edges elastically restrained against rotation under combinations of longitudinal and transverse direct stress. Interaction curves are presented that give the critical combinations of stress for several different degrees of elastic edge restraint, including simple support and complete fixity.
Date: March 1946
Creator: Batdorf, S. B.; Stein, Manuel & Libove, Charles
Partner: UNT Libraries Government Documents Department