Accelerated LCF‐creep experimental methodology for durability life evaluation of turbine blade

Considering the flexible operation conditions, the creep‐fatigue performance of P92 steel plays a crucial role in manufacturing structural components of ultra‐supercritical fossil power plants at 620°C–630°C. The creep‐fatigue interaction tests of P92 steel were conducted at 630°C in air with different duration periods, where the duration periods were simultaneously added on the peak tensile strain and valley compressive strain. The addition of hold time resulted in a rapid decrease of fatigue life, where the reduction amplitude increasing with the hold time. There was more than five times reduction as the hold time increased to 300 s. Moreover, the stress relaxation behavior during hold time exhibited a saturation behavior at long dwell time, where the limited relaxed stress gradually approached to the creep threshold stress. Furthermore, a modified strain energy density exhaustion model involving creep threshold stress was proposed and provided more accurate predictions in comparison with the conventional model, reducing the conservatism.

Section: Introductionmentioning

confidence: 99%

Analysis on stress‐strain behavior and life prediction of P92 steel under creep‐fatigue interaction conditions

Zhao

Han

et al. 2020

“…The chemical compositions (wt%) of this superalloy was listed in Table 1. 56 The 0.2% yield strength of K417 alloy at 710 and 800 C were 775 and 880MPa, respectively.…”

Section: Methodsmentioning

confidence: 96%

“…A Ni‐based cast polycrystalline superalloy, namely, K417, was investigated experimentally in this study. The chemical compositions (wt%) of this superalloy was listed in Table . The 0.2% yield strength of K417 alloy at 710 and 800°C were 775 and 880MPa, respectively.…”

Section: Methodsmentioning

confidence: 99%

Residual fatigue life prediction based on a novel damage accumulation model considering loading history

Shi

et al. 2020

Self Cite

The influence of prior low‐cycle fatigue (LCF) on the residual fatigue life was investigated experimentally. A Ni‐based alloy was cyclically loaded under stress‐controlled low‐high (LH) block loading. In the first loading step, low‐amplitude loading was performed with the stress amplitude of 283.5MPa at 710°C. Different cycles of preloading were performed, varying from 100 to 10 000. Subsequently, high‐amplitude fatigue loading was carried out with the stress amplitude of 315MPa at 800°C. Experimental results show that the previous loading was beneficial to the residual fatigue life when the consumed life fraction is below 0.2 and detrimental when the consumed life fraction is larger than 0.2. A novel nonlinear fatigue damage accumulation model was proposed to estimate the residual LCF life under LH loading path considering the effects of load sequence and preloading cycles. The proposed model provided a better life prediction than some existing models, such as Kwofie‐Rahbar model, Miner' rule, Peng model, and Ye‐Wang model. Lastly, this model was further validated using various materials under LH and high‐low block loadings.

“…More recently, the full-scale turbine blades were experimentally investigated by simulating the in-service stress and temperature distributions along the critical section. [5][6][7][8] In the design phase, the current safe factor of turbine blade may be overly conservative. The accurate creep-fatigue life estimation model can help to extend the expected life of blade.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on creep‐fatigue behaviours of as‐received and service‐exposed turbine blades: Mechanism and life evaluation

Shi

Yang

et al. 2020

Self Cite

In the present study, both the as-received and the 600-h-serviced turbine blades were tested under the creep-fatigue loading. The results showed that the service-exposed blades exhibited a longer creep-fatigue life than the asreceived ones due to the refinement of grain size and the increasing of hardness during the service process. Micro structural characterization revealed that there was no directional coarsening or rafting of γ 0 precipitate after 600 h of service. Moreover, the as-received blades exhibited initial cyclic hardening followed by saturation and softening, whereas the 600-h-serviced blades only exhibited continuous softening until fracture. A conservative service life prediction approach was proposed considering the experienced mission profile. This service life estimation method provides a new way to assess the durability of turbine blade.