Strain energy gradient-based LCF life prediction of turbine discs using critical distance concept

165

Notch features including holes, fillets, shoulders, and grooves commonly exist in engineering components. When subjected to external loads, these geometrical discontinuities generally act as stress raisers and thus present significant influences on the component strength and life, which are more remarkable under complex loading paths. Accordingly, numerous theories and approaches have been developed to address notch effects in metal fatigue as well as damage modelling and life predictions, which aim to provide theoretical support for structural optimal design and integrity evaluation. However, most of them are self‐styled or focus on specific objects, which limits their engineering applicability. This review recalls recent developments and achievements in notch fatigue modelling and analysis of metals. In particular, four commonly used methods for fatigue evaluation of metallic notched components/structures are summarized and elaborated, namely, nominal stress approaches, local stress‐strain approaches, and critical distance theories and weighting control parameters‐based approaches, which intend to provide a reference for further research on notch fatigue analysis and promote the integration and/or development among different approaches for practice.

L = α_{1} \times e^{normalb \times R} σ_{\max}^{β_{1}} .

…”

Section: Critical Distance Theory and Its Applications To Fatiguementioning

confidence: 99%

Recent advances on notch effects in metal fatigue: A review

Liao

Zhu

Correia

et al. 2020

165

“…In most practical cases, fatigue-induced cracks initiate around notches such as rivet holes in riveted joints for local stress concentration at the notch root, where plastic strains/stresses are imposed by surrounding elastic material. 28,29 The local approaches, recognizing the localized nature of the fatigue damage to assess the fatigue life, develop the correlation of the local response amplitude (eg, stress, strain) with endurance index to failure (eg, the number of cycles), where the elastic and plastic strain amplitude can be best described by the Basquin law 30 and the Manson-Coffin law. 31,32 Based on the proposal by Morrow, 33 the relation of the total strain range (Δε) and the fatigue life can be derived from superposition the elastic strain range (Δε e ) and plastic strain range (Δε p ), as presented in Equation (1).…”

Section: Fatigue Life Based On a Local Strain Approachmentioning

confidence: 99%

Global‐local fatigue assessment of an ancient riveted metallic bridge based on submodelling of the critical detail

Liu

Correia

Carvalho

et al. 2018

Increasing traffic demands (ie, load intensity and operational life) on ancient riveted metallic bridges and the fact that these bridges were not explicitly designed against fatigue make the fatigue performance assessment and fatigue life prediction of riveted bridges a concern. This paper proposes a global‐local fatigue analysis method that integrates beam‐to‐solid submodeling, elastoplastic of material in local region, and local fatigue life prediction approach. The proposed beam‐to‐solid submodeling can recognize accuracy local stress/strain information accompanying with the global structural effect on the fatigue response of local riveted joints. The fatigue life is predicted based on cumulative damage rule, local strains, and number of cycles with consideration of traffic data, where the relation between the fatigue life and local strain is derived according to the Basquin and Manson‐Coffin law. Besides, the elastoplastic of material is considered. The proposed methodology for fatigue life prediction based on local strain parameter and the Palmgren‐Miner linear damage hypothesis is implemented in a case study of an ancient riveted bridge.

“…To improve the performance of blades, it is necessary to analyze the coupling mechanism between shockwave and boundary layer . Many valuable studies have been proposed to perform this analysis by means of numerical simulations combining with physics of failure modeling . Among them, Wang et al utilized a reliability index strategy and proposed an uncertainty‐based optimization model for the structure design problem with bounded uncertain information.…”

Section: Introductionmentioning

confidence: 99%

“…9 Many valuable studies have been proposed to perform Nomenclature: X R , continuous random variable; M XR ξ ð Þ, the moment generating function of X R ; K XR ξ ð Þ, the cumulant generating function of X R ; f XR x R ð Þ, the probability density function of X R ; e ξ, the saddlepoint; ϕ(•), the standard normal probability density function of X R ; Φ(•), the standard normal cumulant generating function of X R ; X, the vector of local design variables; X S , the vector of shared design variables; Y ji , the vector of coupling variables which are the output of discipline j; Y ij , the vector of coupling variables which are the output of discipline i; J, the compatibility constraint; Pr(•), the reliability constraints this analysis by means of numerical simulations combining with physics of failure modeling. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Among them, Wang et al 10 utilized a reliability index strategy and proposed an uncertainty-based optimization model for the structure design problem with bounded uncertain information. Correia et al 11 proposed a generalization probabilistic fatigue model which can include multiaxial loading conditions and mean-stress effects.…”

Section: Introductionmentioning

confidence: 99%

Structural reliability analysis and uncertainties‐based collaborative design and optimization of turbine blades using surrogate model

Meng

Yang

Zhang³

et al. 2018

136

In power and energy systems, both the aerodynamic performance and the structure reliability of turbine equipment are affected by utilized blades. In general, the design process of blade is high dimensional and nonlinear. Different coupled disciplines are also involved during this process. Moreover, unavoidable uncertainties are transported and accumulated between these coupled disciplines, which may cause turbine equipment to be unsafe. In this study, a saddlepoint approximation reliability analysis method is introduced and combined with collaborative optimization method to address the above challenge. During the above reliability analysis and design optimization process, surrogate models are utilized to alleviate the computational burden for uncertainties‐based multidisciplinary design and optimization problems. Smooth response surfaces of the performance of turbine blades are constructed instead of expensively time‐consuming simulations. A turbine blade design problem is solved here to validate the effectiveness and show the utilization of the given approach.