Development of a unified creep-fatigue equation including heat treatment

作者：Liu Dan; Pons Dirk John

来源：Fatigue and Fracture of Engineering Materials and Structures, 2018, 41(1): 170-182.

DOI：10.1111/ffe.12670

• creep rupture
• creep-fatigue
• grain size
• strain-life

BackgroundCreep and fatigue damages in metals are known to interact and then lead to aggregated damage. While models exist for fatigue, creep and creep-fatigue, no models cover all 3 load regimes. Also, a heat treatment-related parameter is not well included in most creep-fatigue models.
NeedThere is a need to develop a creep-fatigue equation, which covers the full loading regime from pure fatigue to pure creep, and creep-fatigue. Also needed is inclusion of a heat treatment-related parameter.
ApproachThe unified creep-fatigue equation was started from the Coffin-Manson equation and integrated with the Manson-Haferd parameter. This equation was validated on Inconel 718.
OutcomesThe method of deriving the coefficients and the formula of the creep function are demonstrated, and the resulting equation shows a good ability to describe the grain-size effect and the fully integrated characteristics.
OriginalityOriginal contributions of this work are the development of a new formulation to represent creep, fatigue and creep-fatigue in metals. Also the inclusion of grain sizewhich is a proxy for heat treatmentin the formulation of this equation and in a proposed modified Manson-Haferd parameter.

• 出版日期2018-1