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  • 1
    Electronic Resource
    Electronic Resource
    New approach to the autofrettage of high-strength cylinders (1962)
    Springer
    Experimental mechanics 2 (1962), S. 33-40 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The usual method of autofrettage (cold working) for gun tubes utilizes hydraulic pressure applied directly to the bore in order to plastically deform the wall of the tube so that favorable residual-stress patterns are produced. The strength of the tube is effectively increased, providing many associated benefits; however, ultra-high hydraulic pressures are required for high-strength steels since plastic-flow pressure is directly proportional to the yield strength of the material. A new method for the autofrettage of high-strength steel cylinders requiring greatly reduced pressures is developed and described herein. An oversize mandrel is forced through the tube to plastically deform the walls. Three methods of forcing the mandrel are investigated. Mechanical-push swaging is used in the autofrettage of short 5-in. long specimens with pull swaging and hydraulic-push swaging being used on specimens 40 in. long. All specimens are made from 4340 steel heat treated to various strengths. Cylinders with wall ratios ranging from 1.5 to 2.8, yield strengths ranging from 90,000 to 180,000 psi, and percent enlargements at the bore ranging from 1.0 to 5.0 are utilized. An engineering analysis is made investigating such factors as percent enlargement and elastic recovery at the bore, the ratio of pressure required for pushing the mandrel to the yield strength of the material, the effects of various lubricants on the frictional forces involved, and the induced three-dimensional stresses in the cylinder walls. Sach's boring-out technique is used to evaluate induced residual-stress patterns. Strains are recorded with electric-resistance strain gages and the associated dynamic and static instrumentation is described. Results are presented in graph form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325691
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  • 2
    Electronic Resource
    Electronic Resource
    Residual stresses in thick-walled cylinders resulting from mechanically induced overstrain (1963)
    Springer
    Experimental mechanics 3 (1963), S. 253-262 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Autofrettage is a process for inducing elastic response in thick-walled cylinders subjected to internal pressures which otherwise cause plastic strains. To extend the use of autofrettage to higher pressure applications and to elminate many of the problems encountered in the use of the conventional process based on the use of direct internal hydrostatic pressure, a new technique has been developed which utilizes the mechanical advantage of a sliding wedge to produce the desired bore enlargement. Since the use of a sliding wedge or mandrel will induce shearing forces at the mandrel-cylinder interface, the resultant residual-stress distribution will differ from that theoretically predicted as characteristic of the direct hydrostatic process. It is the purpose of this work to determine the residual-stress distribution as a function of magnitude of overstrain and diameter ratio, and how it affects the reyielding characteristics of cylinders autofrettaged by this technique. Residual-stress distributions, determined by the Sachs boring-out technique for diameter ratios ranging from 1.5 to 2.3 and for several different magnitudes of overstrain, are shown. The shearing force associated with this technique induces substantial longitudinal residual stresses. The increase in the magnitude of this longitudinal residual stress with overstrain and the resultant decrease in the tangential residual stress are shown and discussed. Hydrostatic reyielding tests of autofrettaged cylinders are used to substantiate the decrease of tangential residual stress with increased overstrain. The substantially lower optimum overstrain as compared to the direct hydrostatic technique is shown and discussed. For optimum overstrain, the elastic strength of cylinders autofrettaged by swaging is comparable to that characteristic of the conventional process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325841
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of microscopic plastic-strain distributions in the region of a crack tip (1969)
    Springer
    Experimental mechanics 9 (1969), S. 296-304 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Two independent experimental techniques are used to measure the strain distribution within the plastically deformed region around a crack tip. Moiré grid interference is used to measure the in-plane strain with the specimen grid engraved directly on the specimen surface. Optical interference is used to measure the through-the-thickness strain over the same engraved area. The testing arrangement allows measurement of at-load strain as well as residual strain. The measured strain distribution is compared with recent work by Swedlow using a finite-element numerical technique and with results of the etch-pit technique used by Hahn and Rosenfield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325135
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  • 4
    Electronic Resource
    Electronic Resource
    A comparison of results of axial-tension, rotating-beam and pressurized-cylinder fatigue tests (1969)
    Springer
    Experimental mechanics 9 (1969), S. 250-254 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a previous paper by Davidson, Eisenstadt and Reiner, it was noted that, as the diameter ratio of an open-end, thick-walled cylinder approached unity, the stress state due to internal pressure approaches that of uniaxial tension. It was, therefore, proposed that the fatigue life of a cyclically pressurized thick-walled cylinder might be predicted from the results of axialtension fatigue tests. In this paper, the results of the thick-walled-cylinder fatigue tests, reported in Ref. 2, extrapolated to a diameter ratio of unity, are compared with the results of axial-tension fatigue tests on the same material. The effect of oil in contact with the surface of the axial fatigue specimens and that of varying the cyclic speed from 1800 cpm to 200 cpm are investigated. Rotating beam fatigue test results for the same material are also reported. The results of the axial-tension fatigue tests do not agree with the extrapolated thick-walled cylinder results in the range of fatigue lives from 104 to 106 cycles with the cylinder results showing the shorter lives. For less than 104 cycles, the results converge. No effect of cyclic speed or of oil in contact with the surface was found. The results of the rotating-beam tests generally lie between the axial-tension and extrapolated cylinder results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325156
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  • 5
    Electronic Resource
    Electronic Resource
    A new fracture-toughness test method for thick-walled cylinder material (1972)
    Springer
    Experimental mechanics 12 (1972), S. 184-189 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new method for measuring the plane-strain fracture toughness of the material from a thick-walled cylinder is presented. This method utilizes a notched, “C”-shaped test specimen, pin loaded in tension. This specimen has the advantage of most efficiently utilizing the available material to obtain the maximum possible triaxial constraint at the crack tip. Stress-intensity-factor calibrations for this specimen were obtained by two independent experiments. These are a compliance test, as originally proposed by Irwin, and a fatigue-crack-growth test, as suggested by James and Anderson. Very good agreement was obtained between the results of these two experiments. A stress-intensity calibration for a similar geometry was also obtained using a finite-element analysis and a method developed by Kobayashi to determine stress-intensity factors from finite-element results. The results of this method appear to be low by about 10 percent. Comparative fracture-toughness tests of material from a 2-in.-thick plate of special aircraft quality, 4340 steel, were conducted using the proposed new test method and the ASTM standard bend specimen. These results agreed within 2 percent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02330271
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    Paper (German National Licenses)
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