Cyclic yield strength in definition of design limits for fatigue and creep

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Abstract

This study proposes a cyclic yield strength (CYS, σc ) as a key characteristic for the definition of safe design for engineering structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve, while monotonic yield strength (MYS, σm ) is defined on a monotonic stress-strain curve. Both values of σc and σm are identified using a 2-steps fitting procedure of the experimental stress-strain curves using Ramberg-Osgood and Chaboche material models. Comparison of σc and fatigue endurance limit σf on the S-N fatigue curve reveals that they are approximately equal. Hence, basically safe fatigue design is guaranteed in purely elastic domain defined by the σc . A typical creep rupture curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σc and σm . These stresses separate 3 sections on the creep rupture curve, which are characterised by 3 different creep fracture modes and 3 creep deformation mechanisms. Thus, basically safe creep design is guaranteed in linear creep domain with brittle failure mode defined by the σc . These assumptions are confirmed for several structural low- and high-alloy steels for normal and high-temperature
applications.

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Yield stress
Creep
Fatigue of materials
Stress-strain curves
High temperature applications
Alloy steel
Failure modes
Durability

Keywords

  • cyclic analysis
  • design limits
  • fatigue assessment
  • creep-fatigue strength

Cite this

@article{1128c742a6244149a7d83850a7cab7ac,
title = "Cyclic yield strength in definition of design limits for fatigue and creep",
abstract = "This study proposes a cyclic yield strength (CYS, σc ) as a key characteristic for the definition of safe design for engineering structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve, while monotonic yield strength (MYS, σm ) is defined on a monotonic stress-strain curve. Both values of σc and σm are identified using a 2-steps fitting procedure of the experimental stress-strain curves using Ramberg-Osgood and Chaboche material models. Comparison of σc and fatigue endurance limit σf on the S-N fatigue curve reveals that they are approximately equal. Hence, basically safe fatigue design is guaranteed in purely elastic domain defined by the σc . A typical creep rupture curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σc and σm . These stresses separate 3 sections on the creep rupture curve, which are characterised by 3 different creep fracture modes and 3 creep deformation mechanisms. Thus, basically safe creep design is guaranteed in linear creep domain with brittle failure mode defined by the σc . These assumptions are confirmed for several structural low- and high-alloy steels for normal and high-temperature applications.",
keywords = "cyclic analysis, design limits, fatigue assessment, creep-fatigue strength",
author = "Yevgen Gorash and Donald Mackenzie",
year = "2014",
month = "12",
doi = "10.1002/pamm.201410170",
language = "English",
volume = "14",
pages = "365--366",
journal = "Proceedings in Applied Mathematics and Mechanics, PAMM",
issn = "1617-7061",
number = "1",

}

TY - JOUR

T1 - Cyclic yield strength in definition of design limits for fatigue and creep

AU - Gorash, Yevgen

AU - Mackenzie, Donald

PY - 2014/12

Y1 - 2014/12

N2 - This study proposes a cyclic yield strength (CYS, σc ) as a key characteristic for the definition of safe design for engineering structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve, while monotonic yield strength (MYS, σm ) is defined on a monotonic stress-strain curve. Both values of σc and σm are identified using a 2-steps fitting procedure of the experimental stress-strain curves using Ramberg-Osgood and Chaboche material models. Comparison of σc and fatigue endurance limit σf on the S-N fatigue curve reveals that they are approximately equal. Hence, basically safe fatigue design is guaranteed in purely elastic domain defined by the σc . A typical creep rupture curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σc and σm . These stresses separate 3 sections on the creep rupture curve, which are characterised by 3 different creep fracture modes and 3 creep deformation mechanisms. Thus, basically safe creep design is guaranteed in linear creep domain with brittle failure mode defined by the σc . These assumptions are confirmed for several structural low- and high-alloy steels for normal and high-temperature applications.

AB - This study proposes a cyclic yield strength (CYS, σc ) as a key characteristic for the definition of safe design for engineering structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve, while monotonic yield strength (MYS, σm ) is defined on a monotonic stress-strain curve. Both values of σc and σm are identified using a 2-steps fitting procedure of the experimental stress-strain curves using Ramberg-Osgood and Chaboche material models. Comparison of σc and fatigue endurance limit σf on the S-N fatigue curve reveals that they are approximately equal. Hence, basically safe fatigue design is guaranteed in purely elastic domain defined by the σc . A typical creep rupture curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σc and σm . These stresses separate 3 sections on the creep rupture curve, which are characterised by 3 different creep fracture modes and 3 creep deformation mechanisms. Thus, basically safe creep design is guaranteed in linear creep domain with brittle failure mode defined by the σc . These assumptions are confirmed for several structural low- and high-alloy steels for normal and high-temperature applications.

KW - cyclic analysis

KW - design limits

KW - fatigue assessment

KW - creep-fatigue strength

UR - http://onlinelibrary.wiley.com/doi/10.1002/pamm.201410170/pdf

U2 - 10.1002/pamm.201410170

DO - 10.1002/pamm.201410170

M3 - Article

VL - 14

SP - 365

EP - 366

JO - Proceedings in Applied Mathematics and Mechanics, PAMM

T2 - Proceedings in Applied Mathematics and Mechanics, PAMM

JF - Proceedings in Applied Mathematics and Mechanics, PAMM

SN - 1617-7061

IS - 1

ER -