Transient Stress Analysis and Fatigue Life Estimation of Turbine Blades

2004 ◽  
Vol 126 (4) ◽  
pp. 485-495 ◽  
Author(s):  
Deepak Dhar ◽  
A. M. Sharan ◽  
J. S. Rao
Keyword(s):  
Fatigue Life ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Element Analysis ◽  
Life Estimation ◽  
Start Up ◽  
Fatigue Life Estimation ◽  
Transfer Equations ◽  
Number Of Cycles

This paper is concerned with life estimation of a turbine blade taking into account the combined effects of centrifugal stresses, vibratory stresses and thermal stresses. The stresses are determined by accounting for the rotor acceleration. The blades are subjected to aerodynamic excitation force obtained from thin cambered aerofoil theory under incompressible flow. The thermo-elastic forces are obtained from the three-dimensional non-linear heat transfer equations using the finite element analysis. The fatigue life is estimated using two well known theories, from the number of cycles in various blocks during start-up and shut-down periods of the turbine operation when the stresses peak.

Three-dimensional coupled thermo-mechanical analysis for fatigue failure of a heavy vehicle brake disk: Simulation of braking and cooling phases

2020 ◽  
Vol 234 (13) ◽  
pp. 3145-3163
Author(s):  
Mohammad Rouhi Moghanlou ◽  
Hamed Saeidi Googarchin
Keyword(s):  
Fatigue Life ◽  
Hot Spots ◽  
Thermal Stresses ◽  
Hot Spot ◽  
Circumferential Stress ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Brake Disk ◽  
Life Estimation ◽  
Fatigue Life Estimation

In this paper, transient coupled thermo-mechanical finite element analysis of a three-dimensional model of braking pairs (brake disk and brake pads) is accomplished in order to estimate temperatures and stresses in brake disk during a braking cycle, including braking and cooling phases, and calculate fatigue life. A nonuniform distribution of temperatures is revealed on the surface of the brake disk, gradually generating surface hot spots and hot bands with temperatures up to 800 °C that lead to an uneven distribution of thermal stresses on the frictional surfaces. According to the simulations, variations in the circumferential stress, which is mainly responsible for the cracking of the brake disk, can reach up to 400 MPa in the hot spot areas, depending on the braking configurations. The numerical results are also used to estimate the fatigue life of brake disk using the Smith–Watson–Topper model. The numerical model demonstrates a high accuracy of fatigue life estimation when evaluated by prior experimental studies, signifying the effects of hot spots in reducing the service life of brake disk. Results of the fatigue life estimation show superiority to the analytical method both in the accuracy of calculation and detection of the failure location.

Transient Stress Analysis and High Cycle Fatigue Life Estimation of a Gas Turbine Shrouded HP Compressor Blade

2016 ◽  
Author(s):  
Vinayaka Nagarajaiah ◽  
Nilotpal Banerjee ◽  
B. S. Ajay Kumar ◽  
Kumar K. Gowda ◽  
Tulsidas Dalappa
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
High Cycle Fatigue ◽  
Structural Integrity ◽  
Resonance Condition ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Life Estimation ◽  
Fatigue Life Estimation

This work is focused on developing a technique to assess high cycle fatigue of shrouded HP compressor blades subjected to thermo-mechanical loads like centrifugal stresses, vibratory stresses and thermal stresses in a gas turbine rotor. In practice, the blades are also subjected to resonance condition during steady or transient conditions of operation when passing through critical speeds. Hence, shrouds are added initially at 3/4 length along blade height which helps in reducing vibration amplitude by providing suitable stiffness to the blade and hence better structural integrity. Industrial best practice like Campbell diagram is used for the above purpose. Two approaches employed here for fatigue analysis are linear Finite element analysis (FEA) and Elasto-Plastic FEA. Fictive elastic results are recalculated using Neuber’s Rule. Strain amplitude approach is followed and Coffin-Manson Equation is used to determine the number of start-up and shut-down cycles. Design and analysis is performed using ANSYS 14.5 tool for reliable fatigue life estimation and to predict catastrophic failure due to High Cycle Fatigue.

Fatigue Life Estimation in Notched Geometries

2013 ◽  
Author(s):  
Sebastian Cravero ◽  
Hugo Ernst
Keyword(s):  
Fatigue Life ◽  
Experimental Tests ◽  
Crack Size ◽  
Initial Crack ◽  
Life Estimation ◽  
Threaded Connections ◽  
Fatigue Life Estimation ◽  
Initiation Stage ◽  
Study Techniques ◽  
Number Of Cycles

The fatigue failure in components is divided in two stages: an initiation stage that defines the number of cycles that it takes for a crack to appear in the material and a second stage that estimates the number of cycles where the crack grows until it becomes unstable. Usual fatigue life estimation procedures (in crack free components) only consider the initiation stage and assume that the crack propagation period is relatively small compared with the total life. However, in the case of severely notched geometries like threaded connections, the propagation stage can be an important part of the component fatigue life and must be evaluated. A fundamental issue in the calculation of initiation plus propagation fatigue life is the definition of the initial crack size after the initiation stage. In the present study techniques for crack initiation and crack growth are described. Also the procedure to combine the two techniques and define an initial crack size is presented. The study is based on previous work of C. Navarro, et al. [1]. Additionally, validation against experimental tests on notched specimens is provided.

Uncertainty Analysis in Fatigue Life Prediction of Gas Turbine Blades Using Bayesian Inference

2015 ◽  
Vol 32 (4) ◽  
Author(s):  
Yan-Feng Li ◽  
Shun-Peng Zhu ◽  
Jing Li ◽  
Weiwen Peng ◽  
Hong-Zhong Huang
Keyword(s):  
Fatigue Life ◽  
Bayesian Inference ◽  
Model Selection ◽  
Gas Turbine ◽  
Model Uncertainty ◽  
Life Prediction ◽  
Turbine Blades ◽  
Gas Turbine Blades ◽  
Life Estimation ◽  
Fatigue Life Estimation

AbstractThis paper investigates Bayesian model selection for fatigue life estimation of gas turbine blades considering model uncertainty and parameter uncertainty. Fatigue life estimation of gas turbine blades is a critical issue for the operation and health management of modern aircraft engines. Since lots of life prediction models have been presented to predict the fatigue life of gas turbine blades, model uncertainty and model selection among these models have consequently become an important issue in the lifecycle management of turbine blades. In this paper, fatigue life estimation is carried out by considering model uncertainty and parameter uncertainty simultaneously. It is formulated as the joint posterior distribution of a fatigue life prediction model and its model parameters using Bayesian inference method. Bayes factor is incorporated to implement the model selection with the quantified model uncertainty. Markov Chain Monte Carlo method is used to facilitate the calculation. A pictorial framework and a step-by-step procedure of the Bayesian inference method for fatigue life estimation considering model uncertainty are presented. Fatigue life estimation of a gas turbine blade is implemented to demonstrate the proposed method.

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