A Unified Creep-Fatigue Equation with Application to Engineering Design

Liú, Dan; Pons, Dirk J.

doi:10.5772/intechopen.70877

Cited by 2 publications

(2 citation statements)

References 26 publications

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“…In particular, the model provides a more economic method for fatigue-life prediction since less empirical data are required than other empirical methods such as [15,17]. In addition, the model is applicable for engineering design at the initial stage through combining with finite element analysis (FEA) [28].…”

Section: Extension Of the Empirical Modelsmentioning

confidence: 99%

An Explicit Creep-Fatigue Model for Engineering Design Purposes

Liú

Pons

2018

Metals

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Background: Creep-fatigue phenomena are complex and difficult to model in ways that are useful from an engineering design perspective. Existing empirical-based models can be difficult to apply in practice, have poor accuracy, and lack economy. Need: There is a need to improve on the ability to predict creep-fatigue life, and do so in a way that is applicable to engineering design. Method: The present work modified the unified creep-fatigue model of Liu and Pons by introducing the parameters of temperature and cyclic time into the exponent component. The relationships between them were extracted by investigating creep behavior, and then a reference condition was introduced. Outcomes: The modified formulation was successfully validated on the materials of 63Sn37Pb solder and stainless steel 316. It was also compared against several other models. The results indicate that the explicit model presents better ability to predict fatigue life for both the creep fatigue and pure fatigue situations. Originality: The explicit model has the following beneficial attributes: Integration—it provides one formulation that covers the full range of conditions from pure fatigue, to creep fatigue, then to pure creep; Unified—it accommodates multiple temperatures, multiple cyclic times, and multiple metallic materials; Natural origin—it provides some physical basis for the structure of the formulation, in its consistency with diffusion-creep behavior, the plastic zone around the crack tip, and fatigue capacity; Economy—although two more coefficients were introduced into the explicit model, the economy is not significantly impacted; Applicability—the explicit model is applicable to engineering design for both manual engineering calculations and finite element analysis. The overall contribution is that the explicit model provides improved ability to predict fatigue life for both the creep-fatigue and pure-fatigue conditions for engineering design.

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Section: Extension Of the Empirical Modelsmentioning

confidence: 99%

An Explicit Creep-Fatigue Model for Engineering Design Purposes

Liú

Pons

2018

Metals

Self Cite

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“…This was discussed and proved in [31], where the unified formulation was compared with Wong and Mai's equation. Specifically, taking 63Sn37Pb solder as an example, both Wong and Mai's equation and the unified formulation give high accuracy of fatigue-life prediction when all eight groups of creep-fatigue data are imposed.…”

Section: (4)mentioning

confidence: 99%

Physical-Mechanism Exploration of the Low-Cycle Unified Creep-Fatigue Formulation

Liú

Pons

2017

Metals

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Background-Creep-fatigue behavior is identified as the incorporated effects of fatigue and creep. One class of constitutive-based models attempts to evaluate creep and fatigue separately, but the interaction of fatigue and creep is neglected. Other models treat the damage as a single component, but the complex numerical structures that result are inconvenient for engineering application. The models derived through a curve-fitting method avoid these problems. However, the method of curving fitting cannot translate the numerical formulation to underlying physical mechanisms. Need-Therefore, there is a need to develop a new creep-fatigue formulation for metal that accommodates all relevant variables and where the relationships between them are consistent with physical mechanisms of fatigue and creep. Method-In the present work, the main dependencies and relationships for the unified creep-fatigue equation were presented through exploring what the literature says about the mechanisms. Outcomes-This shows that temperature, cyclic time and grain size have significant influences on creep-fatigue behavior, and the relationships between them (such as linear relation, logarithmical relation and power-law relation) are consistent with phenomena of diffusion creep and crack growth. Significantly, the numerical form of "1 − x" is presented to show the consumption of creep effect on fatigue capacity, and the introduction of the reference condition gives the threshold of creep effect. Originality-By this means, the unified creep-fatigue equation is linked to physical phenomena, where the influence of different dependencies on creep fatigue was explored and relationships shown in this equation were investigated in a microstructural level. Particularly, a physical explanation of the grain-size exponent via consideration of crack-growth planes was proposed.

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A Unified Creep-Fatigue Equation with Application to Engineering Design

Cited by 2 publications

References 26 publications

An Explicit Creep-Fatigue Model for Engineering Design Purposes

An Explicit Creep-Fatigue Model for Engineering Design Purposes

Physical-Mechanism Exploration of the Low-Cycle Unified Creep-Fatigue Formulation

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