LCF Initiated - HCF Propagated Crack Life Estimation of Gas Turbine Bolts

2018 ◽  
Author(s):  
Amit K. Paspulati ◽  
Krishna Veluru ◽  
Kashinath Akki ◽  
Rohit Khattar ◽  
Sudeep Bosu ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Gas Turbine ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Evaluation Studies ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Turbine Rotor ◽  
Cycle Fatigue ◽  
Compressor Rotor

This paper discusses the methodology to calculate high cycle fatigue (HCF) crack propagation life of gas turbine bolts and compares two dimensional (2D) HCF crack propagation life to three dimensional (3D) HCF crack propagation life. Gas turbine bolts when exposed to fatigue loading are prone to crack initiation and propagation (structural failure) during operation. In such cases cracks mostly are initiated by low cycle fatigue (LCF) and propagated by HCF. Therefore in current illustration the authors have evaluated crack propagation primarily initiated by low cycle fatigue and propagated by high cycle fatigue. 2D and 3D fracture methodology approaches had been used for analytical evaluation. The authors conclude on the efficacy of both the methods based on the data from the field. The coupling joint bolts located in the engine mid-section, which are used to join compressor rotor with turbine rotor are being considered for crack evaluation studies. The coupling bolts located in mid-section are primarily loaded by high axial bolt pre-loads needed to keep the joint intact, as well as loaded in bending due to rotor gravity sag. The crack propagation life is evaluated and validated with field data using cracked bolt specimen from the field.

The Fatigue and Fracture Analysis of Steam Turbine Rotor Shafts Containing Defects

2019 ◽  
Vol 795 ◽  
pp. 254-261
Author(s):  
Shang Wang ◽  
Wei Qiang Wang ◽  
Ming Da Song ◽  
Hao Zhang
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Steam Turbine ◽  
Fatigue Crack Propagation ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
Initial Surface ◽  
Cycle Fatigue ◽  
Steam Turbine Rotor ◽  
Fatigue Crack Propagation Life

In this study, the assessment and calculation methods for the crack propagation life of steam turbine rotor shafts containing defects are presented. The analytic methods for estimating the average stress and the alternating stress amplitude of the steam turbine rotor shafts are introduced. The defects on/in the rotor shafts were regularized by the method of fracture mechanics, and the high cycle fatigue crack propagation life and low cycle fatigue crack propagation life of the rotor shafts are estimated from Paris formula. Taking the 60MW turbine rotor shafts containing an initial surface defect and an initial internal defect as the examples respectively, the crack propagation life of them were calculated. The results indicated that the assessment method for the crack propagation life can preliminarily be both used to estimate the safety-operating life and to analyze the fracture reason of a steam turbine rotor shaft containing defects. This paper can provide reference for periodic maintenance and safety evaluation of turbine rotor shafts.

Fatigue Crack Modeling and Simulation Based on Continuum Damage Mechanics

2006 ◽  
Vol 129 (1) ◽  
pp. 96-102 ◽  
Author(s):  
Masakazu Takagaki ◽  
Toshiya Nakamura
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Present Theory ◽  
Continuum Damage ◽  
Cycle Fatigue

Numerical simulation of fatigue crack propagation based on fracture mechanics and the conventional finite element method requires a huge amount of computational resources when the cracked structure shows a complicated condition such as the multiple site damage or thermal fatigue. The objective of the present study is to develop a simulation technique for fatigue crack propagation that can be applied to complex situations by employing the continuum damage mechanics (CDM). An anisotropic damage tensor is defined to model a macroscopic fatigue crack. The validity of the present theory is examined by comparing the elastic stress distributions around the crack tip with those obtained by a conventional method. Combined with a nonlinear elasto-plastic constitutive equation, numerical simulations are conducted for low cycle fatigue crack propagation in a plate with one or two cracks. The results show good agreement with the experiments. Finally, propagations of multiply distributed cracks under low cycle fatigue loading are simulated to demonstrate the potential application of the present method.

scholarly journals Process Induced Residual Stress Effect on Fatigue Lifetime of Automotive Steel Components

2014 ◽  
Vol 996 ◽  
pp. 808-813
Author(s):  
Elias Merhy ◽  
Ngadia Taha Niane ◽  
Bastien Weber ◽  
Philippe Bristiel
Keyword(s):  
Residual Stress ◽  
Heat Affected Zone ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Welding Process ◽  
Fatigue Loading ◽  
Stress Effect ◽  
Cycle Fatigue ◽  
Residual Stress Field ◽  
Fatigue Lifetime

Metal Active Gas (MAG) welding process of steel sheets generates, in the vicinity of the welding joint, the well-known Heat Affected Zone (HAZ) in which the material presents more microstructural defects compared to the original metal. Since high cycle fatigue is largely dependent on the material microstructure features, the HAZ is considered as the weakest zone under high cycle fatigue loading. In addition, the welding causes, in the Heat Affected Zone, irreversible plastic strains that induce important residual stress fields in this critical zone of the structure. Therefore, in order to properly predict the high cycle fatigue life time of the welded automotive components, it is of primordial importance to first identify and then consider, if necessary, the welding induced residual stress field in the structure modeling. In this work, it is found that residual stresses have non-negligible impact on high cycle fatigue lifetime, while its effect is minor in the low cycle fatigue domain.

FE Modeling of FRP-Concrete Interface for very High Cycle Fatigue Behavior

2013 ◽  
Vol 577-578 ◽  
pp. 165-168 ◽  
Author(s):  
M. Mahal ◽  
T. Blanksvärd ◽  
B. Täljsten
Keyword(s):  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Finite Element Program ◽  
Element Program ◽  
Three Dimensional Finite Element ◽  
Concrete Interface

The fatigue damage of FRP-concrete interface is a major problem in strengthened structures subjected to fatigue loading. The available FRP-concrete interface models published in the literature usually deal with fracture mechanism approach, which is unsuitable for high cycle fatigue damage. In this study, a constitutive micro model is developed for FRP-concrete interface for high cycle fatigue and incorporated into a three dimensional finite-element program. Numerical analysis of a double lap joint is carried out, and the results show that the proposed model is reasonably accurate.

An Energy-Based Approach to Determine the Fatigue Strength and Ductility Parameters for Life Assessment of Turbine Materials

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
M.-H. Shen ◽  
Sajedur R. Akanda
Keyword(s):  
Experimental Data ◽  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
Life Assessment ◽  
Cycle Fatigue ◽  
Strength Parameters ◽  
Strength And Ductility ◽  
Good Agreement

An energy-based framework is developed to determine the fatigue strength parameters of the Basquin equation and the fatigue ductility parameters of the Manson–Coffin equation to predict high cycle fatigue (HCF) and low cycle fatigue (LCF) life of a steam turbine rotor base and weld materials. The proposed framework is based on assessing the complete energy necessary to cause fatigue failure of a material. This energy is considered as a fundamental material property and is known as the fatigue toughness. From the fatigue toughness and the experimentally determined fatigue lives at two different stress amplitudes, the cyclic parameters of the Ramberg–Osgood constitutive equation that describes the hysteresis stress–strain loop of a cycle are determined. Next, the coefficients and the exponents of the Basquin and the Manson–Coffin equations are computed from the fatigue toughness and the cyclic parameters of a material. The predicted fatigue life obtained from the present energy-based framework is found to be in a good agreement with the experimental data.

scholarly journals Structural integrity of shot peened Ti6Al4V specimens under fretting fatigue

2021 ◽  
Author(s):  
Sabrina Vantadori ◽  
Jesús Vázquez Valeo ◽  
Andrea Zanichelli ◽  
Andrea Carpinteri ◽  
Raimondo Luciano
Keyword(s):  
High Cycle Fatigue ◽  
Structural Integrity ◽  
Low Cycle Fatigue ◽  
Fatigue Loading ◽  
Fretting Fatigue ◽  
Fe Analysis ◽  
Flat Specimen ◽  
Cycle Fatigue ◽  
Experimental Campaign ◽  
Standard Configuration

AbstractIn the present paper, an experimental campaign performed on shot peened Ti6Al4V specimens under fretting fatigue, available in the literature, is simulated by using the Carpinteri et al. criterion. The experiments examined were carried out using a standard configuration, that is, a cylinder against a flat specimen. The fretting loading is a combination of low-cycle fatigue and high-cycle fatigue, and the corresponding stress field is determined by a FE analysis. A theoretical law is applied to describe the relaxed residual stress produced by shot peening treatment and fatigue loading.

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