Low Cycle Fatigue Life Prediction Using Unified Mechanics Theory in Ti-6Al-4V Alloys

2021

Recent developments in microstructure‐sensitive computational modeling and experimental verification have provided significant insight on how one can estimate fatigue damage and predict useful life. As a myriad of methods and approaches are available, it is important to understand how to properly utilize them in a unified and efficient framework for the quantification of damage in safety‐critical components such as jet engine fan blades, gas turbine disks, and airframe structural connections. To this end, the microstructure‐sensitive studies considering crystal plasticity are reviewed, and methods for implementing the statistical representations of material microstructure are presented. Finally, a computational crystal plasticity approach utilizing the statistical representation of parameters and a new thermodynamically based framework is suggested.

Section: Microstructure‐sensitive Studies Using Statistical Representationmentioning

confidence: 99%

General quantification of fatigue damage with provision for microstructure: A review

Jirandehi

2021

“…In fact, it has been shown 14,47,48 that the total accumulated entropy generated measured from the pristine material until the onset of failure is a material property. Using entropy as a damage metric also has been shown to forecast reliable results for the prediction of fatigue life 8,49,50 . The accumulated entropy from the start of the cyclic load ( t = 0) until the failure time ( t = t f ) can be obtained by integrating Equation 21:

FFE = \int_{0}^{t_{f}} \frac{{\overset{w}{true}}_{p}}{T} italicdt

where FFE is known as the fracture fatigue entropy (FFE), a parameter that is independent of load, frequency, and specimen geometry 14 .…”

Section: Theory and Formulationmentioning

confidence: 99%

Application of thermoelectricity in fatigue of metals

Hajshirmohammadi

2021

An online approach is proposed to predict the fatigue life of metallic specimens under cyclic loading using the concept of thermoelectricity. The working principle of the methodology is described, and experimental results are performed with a fully reversed bending fatigue testing apparatus to evaluate the efficacy of the approach. Results are presented that correlate the measured thermoelastic potential for low‐carbon steel 1018 specimens measured via an infrared camera. It is shown that the application of thermoelectricity provides a practical methodology for early prediction of fatigue.

“…7 Over time, based on empirical measurements that characterize different loading features (e.g., mean stress, load frequency, or load ratio), new methods have been developed that improve the theoretical predictions. [8][9][10] Significant progress has also been reported using a thermodynamic framework to assess material degradation. Basaran and Nie introduced a damage mechanism for solid materials based on thermodynamic principles that use entropy as a single parameter in estimating damage degree.…”

Section: Introductionmentioning

confidence: 99%

On the kinetic formulation of fracture fatigue entropy of metals

Moghanlou

2021

The kinetic concept of the strength of solids is used to determine the fatigue life of stress-controlled cyclic loading and evaluate the fracture fatigue entropy.Unlike the traditional stress or strain-based models, this theory uses the applied stress amplitude and the specimen's surface temperature to determine the lifetime. The degradation fraction in each cycle is used to calculate the life cycle. Then the material parameters of the final life equation are obtained for two materials: low carbon steel 1018 and aluminum 7075-T6. The number of cycles to fracture and the cyclic plastic strain energy (W p ) are used to calculate the fracture fatigue entropy (FFE). It is shown that the life cycle prediction of the proposed model agrees well with the experimental results from the literature. Results provide further evidence for the constancy of FFE.