scholarly journals Crack growth rate prediction based on damage accumulation functions for creep-fatigue interaction

2020 ◽  
Vol 14 (52) ◽  
pp. 299-309
Author(s):  
Andrey Tumanov ◽  
V.N. Shlyannikov ◽  
A.P. Zakharov
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Damage Accumulation ◽  
Rate Prediction ◽  
Creep Fatigue

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

A Model of Nonlinear Fatigue-Creep (Dwell) Interactions

2008 ◽  
Author(s):  
Xijia Wu
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Accumulation Rate ◽  
Interaction Model ◽  
Crack Size ◽  
Nonlinear Creep ◽  
Dwell Fatigue ◽  
Creep Fatigue

A nonlinear creep/dwell-interaction model is derived based on nucleation and propagation of a surface fatigue crack and its coalescence with creep/dwell damages (cavities or wedge cracks) along its path inside the material, which results in the total damage accumulation rate as given by dadN=1+lc+lzλdadNf+dadNenv where (da/dN)f is the pure fatigue crack growth rate, (da/dN)env is the environment-assisted crack growth rate, lc/lz is the cavity/wedge crack size, and λ is the average spacing between the internal cavities or cracks. Since wedge cracks are usually present in the form of dislocation pile-ups at low temperatures and cavitation usually occurs at high temperatures, the model attempts to reconcile the creep/dwell-fatigue phenomena over a broad temperature range of engineering concern. In particular, the model has been used to explain dwell fatigue of titanium alloys and high temperature creep-fatigue interactions in Ni-base superalloys under TCCR, CCCR, THCR and CHCR test conditions (see Annex A for definition of the terminology).

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