Life Prediction Method of CC and DS Ni Base Superalloys Under High Temperature Biaxial Fatigue Loading

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Takashi Ogata
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Life Prediction ◽  
Compressive Strain ◽  
Prediction Method ◽  
Strain Range ◽  
Fatigue Loading ◽  
Normal Strain ◽  
Biaxial Fatigue

Polycrystalline conventional casting (CC) and directionally solidified (DS) Ni base superalloys are widely used as gas turbine blade materials. It was reported that the surface of a gas turbine blade is subjected to a biaxial tensile-compressive fatigue loading during a start-stop operation, based on finite element stress analysis results. It is necessary to establish the life prediction method of these superalloys under biaxial fatigue loading for reliable operations. In this study, the in-plane biaxial fatigue tests with different phases of x and y directional strain cycles were conducted on both CC and DS Ni base superalloys (IN738LC and GTD111DS) at high temperatures. The strain ratio ϕ was defined as the ratio between the x and y directional strains at 1/4 cycle and was varied from 1 to −1. In ϕ=1 and −1. The main cracks propagated in both the x and y directions in the CC superalloy. On the other hand, the main cracks of the DS superalloy propagated only in the x direction, indicating that the failure resistance in the solidified direction is weaker than that in the direction normal to the solidified direction. Although the biaxial fatigue life of the CC superalloy was correlated with the conventional Mises equivalent strain range, that of the DS superalloy depended on ϕ. The new biaxial fatigue life criterion, equivalent normal strain range for the DS superalloy was derived from the iso-fatigue life curve on a principal strain plane defined in this study. Fatigue life of the DS superalloy was correlated with the equivalent normal strain range. Fatigue life of the DS superalloy under equibiaxial fatigue loading was significantly reduced by introducing compressive strain hold dwell. Life prediction under equibiaxial fatigue loading with the compressive strain hold was successfully made by the nonlinear damage accumulation model. This suggests that the proposed method can be applied to life prediction of the gas turbine DS blades, which are subjected to biaxial fatigue loading during operation.

Life Prediction Method of CC and DS Ni Base Superalloys Under High Temperature Biaxial Fatigue Loading

2009 ◽  
Author(s):  
Takashi Ogata ◽  
Takayuki Sakai
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Life Prediction ◽  
Compressive Strain ◽  
Prediction Method ◽  
Strain Range ◽  
Fatigue Loading ◽  
Normal Strain ◽  
Biaxial Fatigue

Polycrystalline conventional casting (CC) and directionally solidified (DS) Ni base superalloys are widely used as gas turbine blade materials. It was reported that surface of a gas turbine blade is subjected to biaxial tensile-compressive fatigue loading during start-stop operation based on finite stress analysis results. It is necessary to establish life prediction method of these superalloys under biaxial fatigue loading for reliable operation. In this study, the in-plane biaxial fatigue tests with different phase of x and y directional strain cycles were conducted on both a CC and a DS Ni base superalloys (IN738LC and GTD111DS) at high temperatures. The strain ratio, φ was defined as a ratio between x and y directional strains at 1/4 cycle and was varied from 1 to −1. In φ = 1 and −1, cracks propagated in both x and y directions in the CC supealloy. On the other hand, the main cracks of the DS superalloy propagated only in the x direction indicating failure resistance in the solidified direction is weaker than that in the direction normal to the solidified direction. Although biaxial fatigue life of the CC superalloy was correlated with conventional Mises equivalent strain range, that of DS superalloy was not. New biaxial fatigue life criterion, equivalent normal strain range for the DS superalloy was derived from iso-fatigue life curve on a principal strain plane defined in this study. Fatigue life of the DS superalloy was correlated with the equivalent normal strain range. Fatigue life of the DS superalloy under equi-biaxial fatigue loading was significantly reduced by introducing compressive strain hold dwell. Life prediction under equi-biaxial fatigue loading with the compressive strain hold was successfully made by the nonlinear damage accumulation model indicating that the proposed method can apply to life prediction of gas turbine blades under biaxial fatigue loading.

A New Energy-Based Uniaxial Fatigue Life Prediction Method for a Gas Turbine Engine Material

2007 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
M.-H. Herman Shen ◽  
Tommy George ◽  
Charles Cross ◽  
Jeffrey Calcaterra
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Life Prediction ◽  
Prediction Method ◽  
Fatigue Life Prediction ◽  
Turbine Engine ◽  
Bending Fatigue ◽  
New Energy ◽  
Stress Ratios ◽  
Materials Used

A new energy-based fatigue life prediction framework for calculation of axial and bending fatigue life at various stress ratios has been developed. The purpose of the life prediction framework is to account for materials used in gas turbine engines, such as Titanium 6Al-4V, which experience an endurance stress limit as the number of cycles increase towards infinity. The work conducted to develop this energy-based framework consist of the following entities: (1) A new life prediction criterion for axial and bending fatigue at various stress ratios for Aluminum 6061-T6, (2) use of the previously developed improved uniaxial energy-based method to acquire fatigue life prior to endurance limit behavior [1], (3) and the incorporation of a statistical energy-based fatigue life calculation scheme to the uniaxial life criterion (the first entity of the framework), which is capable of constructing prediction intervals based on a specified percent confidence level. The exactitude of this work was verified by comparison between theoretical approximations and experimental results from recently acquired Al 606-T6 and Ti 6Al-4V data. The comparison shows very good agreement, thus validating the capability of the framework to produce accurate fatigue life predictions.

An Energy-Based Method for Uni-Axial Fatigue Life Calculation

2009 ◽  
Author(s):  
Hakan Ozaltun ◽  
Jeremy Seidt ◽  
M.-H. Herman Shen ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Life Prediction ◽  
Prediction Method ◽  
Strain Curve ◽  
Fatigue Life Prediction ◽  
Cyclic Process ◽  
Model Approximation ◽  
Plastic Energy ◽  
Remaining Fatigue Life

An energy based fatigue life prediction framework has been developed for calculation of remaining fatigue life of in-service gas turbine materials. The purpose of the life prediction framework is to account for the material aging effect on fatigue strength of gas turbine engines structural components which are usually designed for infinite life. Previous studies [1–7] indicate the total strain energy dissipated during a monotonic fracture process and a cyclic process is a material property that can be determined by measuring the area underneath the monotonic true stress-strain curve and the sum of the area within each hysteresis loop in the cyclic process, respectively. The energy-based fatigue life prediction framework consists of the following entities: (1) development of a testing procedure to achieve plastic energy dissipation per life cycle and (2) incorporation of an energy-based fatigue life calculation scheme to determine the remaining fatigue life of in-service gas turbine materials. The accuracy of the remaining fatigue life prediction method was verified by comparison between model approximation and experimental results of Aluminum 6061-T6 (Al 6061-T6). The comparison shows promising agreement, thus validating the capability of the framework to produce accurate fatigue life prediction.

An Energy-Based Uniaxial Fatigue Life Prediction Method for Commonly Used Gas Turbine Engine Materials

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Onome E. Scott-Emuakpor ◽  
Herman Shen ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Life Prediction ◽  
Prediction Method ◽  
Gas Turbine Engine ◽  
Turbine Engine ◽  
Bending Fatigue ◽  
Al 6061 ◽  
Stress Ratios

A new energy-based life prediction framework for calculation of axial and bending fatigue results at various stress ratios has been developed. The purpose of the life prediction framework is to assess the behavior of materials used in gas turbine engines, such as Titanium 6Al-4V (Ti 6Al-4V) and Aluminum 6061-T6 (Al 6061-T6). The work conducted to develop this energy-based framework consists of the following entities: (1) a new life prediction criterion for axial and bending fatigue at various stress ratios for Al 6061-T6, (2) the use of the previously developed improved uniaxial energy-based method to acquire fatigue life prior to endurance limit region (Scott-Emuakpor et al., 2007, “Development of an Improved High Cycle Fatigue Criterion,” ASME J. Eng. Gas Turbines Power, 129, pp. 162–169), (3) and the incorporation of a probabilistic energy-based fatigue life calculation scheme to the general uniaxial life criterion (the first entity of the framework), which is capable of constructing prediction intervals based on a specified percent confidence level. The precision of this work was verified by comparison between theoretical approximations and experimental results from recently acquired Al 606-T6 and Ti 6Al-4V data. The comparison shows very good agreement, thus validating the capability of the framework to produce accurate uniaxial fatigue life predictions for commonly used gas turbine engine materials.

Fatigue Life Prediction Under Multiaxial Variable Amplitude Loading Using A Stress-Based Criterion

2020 ◽  
Vol 10 (1) ◽  
pp. 33-53
Author(s):  
Quoc Huy VU ◽  
Dinh Quy VU ◽  
Thi Tuyet Nhung LE
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Prediction Method ◽  
Fatigue Loading ◽  
Multiaxial Fatigue ◽  
Fatigue Life Prediction ◽  
Random Loading ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
1045 Steel

This article presents fatigue life calculations for metals under different multiaxial variable amplitude loading patterns. Developed from a stress-based multiaxial fatigue criterion, a damage parameter used in the fatigue life prediction method can capture correctly different damage mechanisms (proportional and non-proportional multiaxiality, mean stress, asynchronous and variable amplitude) of fatigue loading in the high cycle fatigue domain. The method is based on a reference S-N curve and a cumulative damage law. Assessment of the accuracy of the proposed method is carried out with three different materials from literature (EN-GS800-2 cast iron, 39NiCrMo3 steel and SAE 1045 steel) subjected to different patterns of variable amplitude loading (blocks, non-proportional asynchronous and proportional random loading). Results reveal that the prediction method is in good accordance with the experimental data.

Micromechanics Method to Evaluate Fatigue Life of Ni-Based Superalloys during Morphological Evolution

2008 ◽  
Vol 385-387 ◽  
pp. 221-224
Author(s):  
Wen Ping Wu ◽  
Ya Fang Guo ◽  
Yue Sheng Wang
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Life Prediction ◽  
Morphological Evolution ◽  
Mean Field ◽  
Prediction Method ◽  
Field Method ◽  
External Stress ◽  
Equivalent Inclusion ◽  
Evolution Of Precipitates

A quantitative life prediction method has been proposed to evaluate fatigue life during morphological evolution of precipitates in Ni-based superalloys. The method is essentially based on Eshelby’s equivalent inclusion theory and Mori-Tanaka’s mean field method. The shape stability and life prediction are discussed when the external stress and matrix plastic strain are applied. The calculated results show that the fatigue life is closely related with microstructures evolution of precipitates. The magnitude and sign of the external stress and matrix plastic strain have an important effect on fatigue life of Ni-based superalloys during the morphological evolution of precipitates.

Sign in / Sign up

Export Citation Format

Share Document