Validation of LCF Life of Turbine Rotor Assembly of a Turbo-Shaft Engine Through Cyclic Spin Test

2014 ◽  
Author(s):  
Hardik Roy ◽  
S. Esakki Muthu ◽  
P. Udayanan ◽  
Girish K. Degaonkar ◽  
Selwyn Anbarasan
Keyword(s):  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Second Phase ◽  
Cycle Fatigue ◽  
Test Rig ◽  
Turbine Rotors ◽  
Rotor Assembly ◽  
Load Conditions ◽  
Engine Rotors

Gas turbine rotors are high speed rotating components which operate under high temperatures. These turbine rotors undergo repeated cycles of low speeds to high speeds and therefore low stresses to high stresses which lead to low cycle fatigue failure. This low cycle fatigue leads to initiation of cracks at high stress areas like bolt holes, blade slots or disc bore. During design the life obtained through numerical methods is verified by cyclic spin tests. This particular paper talks about the spin testing of turbine rotor assembly of a turbo-shaft engine to validate its low cycle fatigue life obtained through analysis. These three stage turbine rotors were indigenised for cost savings. The life of the indigenously designed rotors were required to be the same as the turbine rotors being supplied by the engine OEM’s. Since the test rig which was used to validate the life of the rotors had a limitation of applying uniform temperatures, there was a need to develop a test schedule that simulates the operating conditions of the actual engine rotors. The work was carried out in two phases. In the first phase FEA tools were utilised to find out stress and strain levels of the turbine rotors by applying actual engine load conditions. Since rotor assembly was tested under uniform temperature in the test rig a combination of centrifugal load and temperature that would result in the same factor of safety levels of the rotors as in the actual engine conditions was arrived at in an iterative manner. Once the right combination was achieved the life of the engine rotors under test conditions was estimated numerically. In the second phase cyclic spin test was carried out on the turbine rotor assembly at equivalent load conditions. At regular intervals dimensional and NDT checks were carried out on the rotor assembly to find out crack initiation. The life of the rotor assembly which was estimated with the help of FE tool was validated through spin test.

scholarly journals Estimation of Possibilities of Using Fractal Dimension and Information Entropy of Elastic Waves for Assessment of Damage to Steel 20 at Low Cycle Fatigue

2021 ◽  
Vol 24 (3) ◽  
pp. 17-25
Author(s):  
A.A. Khlybov ◽  
Y.G. Kabaldin ◽  
M.S. Anosov ◽  
D.A. Ryabov ◽  
D.A. Shatagin ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Elastic Wave ◽  
Information Entropy ◽  
Low Cycle Fatigue ◽  
Experimental Studies ◽  
Ultrasonic Signal ◽  
Second Phase ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation ◽  
Steel 20

The paper presents the results of experimental studies of specimens made of steel 20 for low-cycle fatigue (cantilever bending). A fatigue curve was obtained for the material under study in the range of stress amplitudes from 210 to 380 MPa. In logarithmic coordinates, this dependence is linear. According to the research results, it has been shown that one of the structure-sensitive characteristics is the shape of an elastic wave pulse transmitted through the medium under study. To analyze the pulse shape of an elastic wave, an algorithm is proposed for assessing the damage of materials, using the values of the fractal dimension of the attractor and the information entropy in the process of fatigue loading. It was found that according to the obtained dependences, the process of fatigue damage accumulation can be conditionally divided into 2 phases. In the first phase, the entropy of the ultrasonic signal practically does not change and remains within the range of 0.05-0.1 nat. The fractal dimension of the attractor of the ultrasonic signal increases from 1.5 to 1.8. During the transition to the second phase, the maximum values of the fractal dimension of the attractor of the ultrasonic signal are observed, the values of which decrease in the second phase to 1.4 before the destruction of the sample. The information entropy values in the second phase increase monotonically up to 0.55 nat. Studies have shown that the obtained dependences practically do not change with a change in the stress amplitude. The results of studies at various stress amplitudes have shown that the characteristics of the fractal dimension of the attractor and the information entropy of elastic wave pulses that have passed through the zones of accumulated damage in the metal expand and supplement the capabilities of acoustic methods in the problems of assessing the performance of materials with low-cycle fatigue and make it possible to identify the stage of destruction of steel 20.

Experience With Large Heavy-Duty Gas Turbine Rotors

1981 ◽  
Author(s):  
O. R. Schmoch ◽  
B. Deblon
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Rotor ◽  
Strength Properties ◽  
Operating Conditions ◽  
Material Strength ◽  
Heavy Duty ◽  
Turbine Rotors ◽  
Heavy Duty Gas Turbine ◽  
Response To Temperature

The peripheral speeds of the rotors of large heavy-duty gas turbines have reached levels which place extremely high demands on material strength properties. The particular requirements of gas turbine rotors, as a result of the cycle, operating conditions and the ensuing overall concepts, have led different gas turbine manufacturers to produce special structural designs to resolve these problems. In this connection, a report is given here on a gas turbine rotor consisting of separate discs which are held together by a center bolt and mutually centered by radial serrations in a manner permitting expansion and contraction in response to temperature changges. In particular, the experience gained in the manufacture, operation and servicing are discussed.

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.

scholarly journals Low cycle fatigue modelling of a steam turbine rotor steel

2019 ◽  
Vol 23 ◽  
pp. 149-154
Author(s):  
Ahmed Azeez ◽  
Robert Eriksson ◽  
Mattias Calmunger ◽  
Stefan B. Lindström ◽  
Kjell Simonsson
Keyword(s):  
Steam Turbine ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
Rotor Steel ◽  
Cycle Fatigue ◽  
Steam Turbine Rotor

3D Crack Growth Analysis and Its Correlation With Experiments for Critical Turbine Components Under an International Collaborative Program

2008 ◽  
Author(s):  
J. Hou ◽  
J. Dubke ◽  
K. Barlow ◽  
S. Slater ◽  
L. Harris ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Cycle Fatigue ◽  
3D Crack Growth ◽  
International Collaborative ◽  
2D And 3D ◽  
Growth Analyses ◽  
Stress Analyses

Following a reanalysis of the original material data plus supplementary Low Cycle Fatigue (LCF) specimen testing, an Original Equipment Manufacturer (OEM) reduced the low cycle fatigue life limits for a number of turbine components. To ascertain the validity of the new life limits, an international collaborative spin rig test program was initiated to provide more accurate low cycle fatigue life limits. The program covered a broad range of activities including, Finite Element (FE) stress analyses, cyclic spin rig testing, fractographic assessment and fatigue crack growth (FCG) analyses. This paper describes the 2D and 3D crack growth analyses of critical turbine components in a turboprop gas turbine engine, comparison of predicted results obtained using different software and also correlations with spin test results from the program. First, FE stress analyses of selected turbine components were carried out under both engine operating conditions and spin-rig test configurations in order to determine the maximum and minimum operating speeds required to match the stress ranges at the critical location specified by the OEM under engine operating conditions. Second, 2D and 3D crack growth analyses were performed independently by three organisations for a disk bolthole using the state-of-the-art software. Third, the predictions from different software were compared, and the relative technical merits of each software were evaluated. Finally, the predicted results were correlated against the striation counts determined by the OEM from the results of spin rig tests.

Design of a New Experimental Rig for Thermal Cyclic Testing of Combustor Liner Tiles

2008 ◽  
Author(s):  
C. Mende ◽  
O. Liedtke ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Quality Data ◽  
Test Facility ◽  
Test Rig ◽  
Design Data ◽  
High Quality Data ◽  
Damage Models ◽  
Combustor Liner ◽  
Experimental Rig

This paper describes the design and operation of a new test rig, which allows the simulation of real engine operating conditions leading to Low-Cycle Fatigue of combustor liner tiles. The experimental setup will provide high-quality data for the development of damage models. At first the design data of the test rig will be derived from the relevant damage mechanisms in Combustor Liner Tiles (CLT). Then the construction of the test rig and its integration into an existing high temperature high pressure test facility will be elucidated. Finally experimental data of a typical simulated thermal cycle is shown.

Influence of Creep on Low-Cycle Fatigue Life Assessment of Ultra-Supercritical Steam Turbine Rotor

2014 ◽  
Author(s):  
W. Z. Wang ◽  
J. H. Zhang ◽  
H. F. Liu ◽  
Y. Z. Liu
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
High Temperature Creep ◽  
Cycle Fatigue ◽  
Term Operation ◽  
Start Up

Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.

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