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Research Papers: Materials and Fabrication

The Effects of the Material's Exact Yield Point and Its Plastic Properties on the Safe Maximum Pressure of Gun Barrels

[+] Author and Article Information
J. Perry

Pearlstone Center for
Aeronautical Engineering Studies,
Department of Mechanical Engineering,
Ben-Gurion University of the Negev,
Beer-Sheva 84105, Israel

M. Perl

Fellow ASME
Aaron Fish Professor of
Mechanical Engineering-Fracture Mechanics
Pearlstone Center for
Aeronautical Engineering Studies,
Department of Mechanical Engineering,
Ben-Gurion University of the Negev,
Beer-Sheva 84105, Israel

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received November 26, 2016; final manuscript received June 9, 2017; published online August 2, 2017. Assoc. Editor: San Iyer.

J. Pressure Vessel Technol 139(5), 051401 (Aug 02, 2017) (6 pages) Paper No: PVT-16-1225; doi: 10.1115/1.4037121 History: Received November 26, 2016; Revised June 09, 2017

The design of a gun barrel aims at maximizing its firing power, determined by its safe maximum pressure (SMP)—the maximal allowed firing pressure—which is considerably enhanced by inducing a favorable residual stress field through the barrel's wall commonly by the autofrettage process. Presently, there are two distinct processes: hydrostatic and swage autofrettage. In both processes, the barrel's material is fully or partially plastically deformed. Recently, a 3D computer code has been developed, which finally enables a realistic simulation of both swage and hydraulic autofrettage processes, using the experimentally measured stress–strain curve and incorporating the Bauschinger effect. This code enables a detailed analysis of all the factors relating to the final SMP of a barrel and can be used to establish the optimal process for any gun-barrel design. A major outcome of this analysis was the fact that the SMP of an autofrettaged barrel is dictated by the detailed plastic characteristics on the barrel's material. The main five plastic parameters of the material that have been identified are: the exact (zero offset) value of the yield stress, the universal plastic curve in both tension and compression, the Bauschinger effect factor (BEF) curve, and the elastic–plastic transition range (EPTR). A detailed comparison between three similar barrel materials points to the fact that the major parameter determining the barrel's SMP is the yield stress of the material and that the best way to determine it is by the newly developed “zero offset” method. All other four parameters are found to have a greater influence on the SMP of a hydraulically autofrettaged barrel than on a swaged one. The simplicity of determining the zero offset yield stress will enable its use in any common elastic and elastoplastic problem instead of the present 0.1% or 0.2% yield stress methods.

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References

Figures

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Fig. 1

First test—uniaxial tensile straining

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Fig. 2

Second test—tension–compression loop

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Fig. 3

The zero offset yield point (ZOYP) in tension

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Fig. 4

The universal tensile stress–strain curve

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Fig. 5

Yield stress Bauschinger effect factor (BEF)

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Fig. 6

The typical tension–compression cycling test

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Fig. 7

The universal compressive stress–strain curve

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Fig. 8

Tensile stress–strain curves for different materials

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Fig. 11

The universal compressive curves for different materials

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Fig. 12

The 0% and 0.1% offset yield stresses for the three materials

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Fig. 13

The EPTR for the different materials

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Fig. 15

Material yield stresses determined by different methods

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