### Abstract

A generalized threshold function for isotropic viscoplastic materials, which can also serve as a yield function in rate-independent plasticity, is suggested for materials that exhibit a strength differential and/or a permanent volume change. The motivation for this type of a threshold function is that experiments, at both 25 and 650 °C, on the nickel base alloy Inconel 718 indicate that higher stresses occur in compression than in tension. Similar results have been obtained for martensitic steels and other metallic alloys at 25 °C. A general approach for determining the inelastic flow dependence on each of the three stress invariants (I_{1}, J_{2}, and J_{3}) is to follow stress paths where only one invariant is changing. Two classical experiments that do this are hydrostatic pressure and pure torsion, however many others are possible. Unfortunately, these stress paths generally require three-dimensional stress states, which are difficult to obtain in the laboratory. Thus, for experimental expediency, tests involving axial-torsional loading of thin-walled tubes can be used to determine the significance of the first and third stress invariants, I_{1} and J_{3}, respectively.

Original language | English (US) |
---|---|

Pages (from-to) | 101-110 |

Number of pages | 10 |

Journal | American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP |

Volume | 391 |

State | Published - 1999 |

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### All Science Journal Classification (ASJC) codes

- Industrial and Manufacturing Engineering
- Mechanical Engineering

### Cite this

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**Inelastic anisotropy of Inconel 718 : Experiments and mathematical representation.** / Iyer, Saiganesh K.; Lissenden, III, Clifford Jesse.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Inelastic anisotropy of Inconel 718

T2 - Experiments and mathematical representation

AU - Iyer, Saiganesh K.

AU - Lissenden, III, Clifford Jesse

PY - 1999

Y1 - 1999

N2 - A generalized threshold function for isotropic viscoplastic materials, which can also serve as a yield function in rate-independent plasticity, is suggested for materials that exhibit a strength differential and/or a permanent volume change. The motivation for this type of a threshold function is that experiments, at both 25 and 650 °C, on the nickel base alloy Inconel 718 indicate that higher stresses occur in compression than in tension. Similar results have been obtained for martensitic steels and other metallic alloys at 25 °C. A general approach for determining the inelastic flow dependence on each of the three stress invariants (I1, J2, and J3) is to follow stress paths where only one invariant is changing. Two classical experiments that do this are hydrostatic pressure and pure torsion, however many others are possible. Unfortunately, these stress paths generally require three-dimensional stress states, which are difficult to obtain in the laboratory. Thus, for experimental expediency, tests involving axial-torsional loading of thin-walled tubes can be used to determine the significance of the first and third stress invariants, I1 and J3, respectively.

AB - A generalized threshold function for isotropic viscoplastic materials, which can also serve as a yield function in rate-independent plasticity, is suggested for materials that exhibit a strength differential and/or a permanent volume change. The motivation for this type of a threshold function is that experiments, at both 25 and 650 °C, on the nickel base alloy Inconel 718 indicate that higher stresses occur in compression than in tension. Similar results have been obtained for martensitic steels and other metallic alloys at 25 °C. A general approach for determining the inelastic flow dependence on each of the three stress invariants (I1, J2, and J3) is to follow stress paths where only one invariant is changing. Two classical experiments that do this are hydrostatic pressure and pure torsion, however many others are possible. Unfortunately, these stress paths generally require three-dimensional stress states, which are difficult to obtain in the laboratory. Thus, for experimental expediency, tests involving axial-torsional loading of thin-walled tubes can be used to determine the significance of the first and third stress invariants, I1 and J3, respectively.

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UR - http://www.scopus.com/inward/citedby.url?scp=0033318433&partnerID=8YFLogxK

M3 - Article

VL - 391

SP - 101

EP - 110

JO - American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

JF - American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

SN - 0277-027X

ER -