Creep-Fatigue Tests on Full Scale Directionally Solidified Turbine Blades

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Xiaojun Yan ◽  
Jingxu Nie
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Full Scale ◽  
Life Assessment ◽  
Directionally Solidified ◽  
Creep Fatigue ◽  
Life Tests

A new experimental method, in which a full scale directionally solidified (DS) alloy turbine blade is loaded by a special design rig employing friction force and heated by eddy current induction, is proposed to conduct creep-fatigue life tests in this investigation. The method can take factors such as geometry, volume, especially cast procedures, etc., into creep-fatigue life assessment. Principle and design of the test rig are fully explained. Creep-fatigue tests of turbine blades made of DZ4 alloy (one type of DS alloys) were conducted and test data were analyzed. Life prediction based on test data of this investigation shows good agreement with actual flight experience of these blades. The method of this article provides a new way to estimate the potential creep-fatigue or low cycle fatigue life for turbine blades.

Creep/Fatigue Tests on Full Scale Hollow Turbine Blades Considering Temperature Gradient

2016 ◽  
Author(s):  
Cao Chen ◽  
Xiaojun Yan
Keyword(s):  
Temperature Gradient ◽  
Induction Heating ◽  
Eddy Current ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Heating Furnace ◽  
Full Scale ◽  
Creep Fatigue ◽  
Cooling Hole

Working in a harsh environment with high temperature gas and high rotation speed, hollow turbine blades of gas turbine engine commonly endure both creep damage and low cycle fatigue damage at the same time. It is difficult to predict the life of hollow turbine blades accurately because of a strong coupling effect between creep and low cycle fatigue (creep/fatigue) damage. To address this difficulty, one effective way is to carry out creep/fatigue tests on full scale hollow turbine blades in a bench environment. The present creep/fatigue test methods on full scale hollow turbine blades usually do not consider the temperature gradient between the wall of cooling hole and blade surface. It does not matches the actual working circumstance of hollow turbine blades, under which the temperature gradient at the blade body can reached 150°C or even more higher. This investigation proposes a new experimental setup of creep/fatigue tests on full scale hollow turbine blades, in which real hollow turbine blades are heated by the eddy current induction heating furnace and cooled by cooling air which goes through the hollow blade’s cooling hole. During the tests, the temperature gradient between the wall of cooling holes and blade surfaces were controlled by adjusting the power of eddy current induction heating furnace and the flux of cool-air. Several thermocouples are employed to measure and validate the temperature gradient at the key/critical section, among them three are embed inside the wall of cooling hole by cutting the hollow turbine blade along cooling hole into three parts, and two are glued on the blade’s surface. Tests results show that, when the eddy current induction heating furnace is working stably with an output power of 6.4 Kw and meanwhile the flux of cooling air which goes through the hollow turbine blade’s cooling hole reaches 10 liter per minute, the temperature gradient of the hollow turbine blade at the key/critical section can be well simulated in a bench environment. Eight full scale hollow turbine blades have been tested at four different stress levels in this investigation. The test data are processed to obtain the field life based on equivalent damage principle. The field life data of the hollow turbine blades fits well with that of their flight experience.

The Analysis on the Low Cycle Fatigue Behavior of a Directionally Solidified Superalloy with Recrystallized Surface Layers

2008 ◽  
Vol 44-46 ◽  
pp. 43-50 ◽  
Author(s):  
Hui Ji Shi ◽  
Xian Feng Ma ◽  
Da Wei Jia ◽  
Hai Feng Zhang ◽  
Li Sha Niu
Keyword(s):  
Fatigue Life ◽  
Shot Peening ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Surface Layers ◽  
Time Observation

Specimens of a directionally solidified superalloy with different shot peening pressure were annealed at 1220oC in vacuum condition to get recrystallized surface layers with different micro-structures. Low cycle fatigue tests of these specimens were performed at room temperature and 400oC by using an electrohydraulic load frame in the SEM system for real-time observation. The initiation and propagation of cracks were inspected and the influence of the micro-structure of the recrystallized layer on the material fatigue behavior was analyzed. The low cycle fatigue life of the specimens depends mainly on the characteristics of the recrystallized layer. When the shot peening pressure is lower, the recrystallized layer is thin and not integrated, and the fatigue life decreases obviously in comparison with that of the specimen without recrystallized surface layer. When the shot peening pressure increases, the recrystal grains are more integrated, and the fatigue life rises. A comparison of the recrystallized layers between the blade surface and the specimen surface has been done and it points that the incompact surface recrystal layer is very dangerous to gas turbine blades.

Verification of the Prediction Methods of Strain Range in Notched Specimens Made of Mod.9Cr-1Mo

2010 ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Shingo Date ◽  
Sota Watanabe ◽  
Yasuhiro Enuma ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Fatigue Tests ◽  
Estimation Methods ◽  
Prediction Methods ◽  
Test Machine ◽  
Notched Specimens ◽  
Creep Fatigue

Several innovative prediction methods of strain range have been developed in order to apply to the Generation IV plants. In a component design at elevated temperature, ‘strain range’ is used to calculate the fatigue and creep-fatigue damage. Therefore, prediction of ‘strain range’ is one of the most important issues to evaluate the components’ integrity during these lifetimes. To verify the strain prediction method of discontinues structures at evaluated temperature, low cycle fatigue tests were carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo, because it is a candidate material for a primary and secondary heat transports system components of JSFR (Japanese Sodium Fast Reactor). Deformation control fatigue tests and thermal fatigue tests were performed by ordinary uni-axial push-pull test machine and equipment generating the thermal gradient in the notched plate by induction heating. Stress concentration level was changed by varying the notch radius in the both kind of tests. Crack initiation and propagation process during the fatigue test were observed by the digital micro-scope and replica method. Elastic and inelastic FEAs were also carried out to estimate the ‘strain range’ for the prediction of fatigue life. Then the ranges of several strain predictions and estimations were compared with the test results. These predictions were based on the sophisticated technique to estimate the ‘strain range’ from elastic FEA. Stress reduction locus (SRL) method, simple elastic follow-up method, Neuber’s rule method and the methods supplied by elevated temperature design standards were applied. Through these results, the applicability and conservativeness of these strain prediction and estimation methods, which is the basis of the creep-fatigue life prediction, is discussed.

Verification of the Estimation Methods of Strain Range in Notched Specimens Made of Mod.9Cr-1Mo Steel

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Shingo Date ◽  
Sota Watanabe ◽  
Yasuhiro Enuma ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Fatigue Tests ◽  
Estimation Methods ◽  
Test Machine ◽  
Component Reliability ◽  
Notched Specimens ◽  
Creep Fatigue

Several methods of estimating strain range at a structural discontinuity have been developed in order to assess component reliability. In a component design at elevated temperature, estimation of strain range is required to evaluate the fatigue and creep-fatigue damage. Therefore, estimation of strain range is one of the most important issues when evaluating the integrity of a component during its lifetimes. To verify the methods of estimating strain range for discontinuous structures, low cycle fatigue tests were carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo steel, because it is a candidate material for a primary and secondary heat transport system components of Japan Sodium-cooled Fast Reactor (JSFR). Displacement control fatigue tests and thermal fatigue tests were performed by ordinary uniaxial push–pull test machine and equipment generating the thermal gradient in the notched plate by induction heating. Several notch radii were employed to vary the stress concentration level in both kinds of tests. Crack initiation and propagation process during the tests were observed by a digital microscope and the replica method to define the failure cycles. Elastic and inelastic finite element analyses were also performed to estimate strain range for predicting fatigue life. Then, these predictions were compared with the test results. Several methods such as stress redistribution locus (SRL) method, simple elastic follow-up (SEF) method, Neuber's law, and the procedures employed by elevated temperature design codes were applied. Through these comparisons, the applicability and conservativeness of these strain range estimation methods, which is the basis of the fatigue and creep-fatigue life prediction, are discussed.

Creep and Creep-Fatigue Deformation and Life Assessment of Ni-Based Alloy 740H and Alloy 617

2018 ◽  
Author(s):  
Shengde Zhang ◽  
Yukio Takahashi
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Hold Time ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Life Assessment ◽  
Prediction Methods ◽  
Creep Tests ◽  
Alloy 617 ◽  
Creep Fatigue

This paper presents creep and creep-fatigue deformations and lives of both Ni-based alloys, Alloy 740H and Alloy 617. Creep tests were performed using solid bar specimens at 650°C-800°C, and effect of cyclic loading on creep deformation and rupture was discussed. Strain controlled creep-fatigue tests were also performed under triangular and trapezoidal waveforms at 700°C. Alloy 740H showed stronger creep-fatigue resistance compared to Alloy 617. Creep-fatigue lives in trapezoidal waveform were smaller than those in the pure fatigue test and the creep-fatigue lives decreased as the hold time increased. Applicability of four representative creep-fatigue life prediction methods was discussed.

scholarly journals Unified Principal S–N Equation for Friction Stir Welding of 5083 and 6061 Aluminum Alloys

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangwei Li ◽  
Ji Fang ◽  
Xiaoli Guan
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Friction Stir Welding ◽  
Test Data ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Test Results ◽  
Friction Stir ◽  
Fatigue Life Assessment ◽  
Curve Equation

AbstractWith the popularization of friction stir welding (FSW), 5083-H321 and 6061-T6 aluminum alloy materials are widely used during the FSW process. In this study, the fatigue life of friction stir welding with two materials, i.e., 5083-H321 and 6061-T6 aluminum alloy, are studied. Fatigue tests were carried out on the base metal of these two materials as well as on the butt joints and overlapping FSW samples. The principle of the equivalent structural stress method is used to analyze the FSW test data of these two materials. The fatigue resistances of these two materials were compared and a unified principal S–N curve equation was fitted. Two key parameters of the unified principal S–N curve obtained by fitting, Cd is 4222.5, and h is 0.2693. A new method for an FSW fatigue life assessment was developed in this study and can be used to calculate the fatigue life of different welding forms with a single S–N curve. Two main fatigue tests of bending and tension were used to verify the unified principal S–N curve equation. The results show that the fatigue life calculated by the unified mean 50% master S–N curve parameters are the closest to the fatigue test results. The reliability, practicability, and generality of the master S–N curve fitting parameters were verified using the test data. The unified principal S–N curve acquired in this study can not only be used in aluminum alloy materials but can also be applied to other materials.

Investigation on Material's Fatigue Property Variation Among Different Regions of Directional Solidification Turbine Blades—Part II: Fatigue Tests on Bladelike Specimens

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Xiaojun Yan ◽  
Mingjing Qi ◽  
Ying Deng ◽  
Xia Chen ◽  
Ruijie Sun ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Maximum Stress ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Fatigue Property ◽  
Fatigue Tests ◽  
Full Scale ◽  
Test Results ◽  
Property Variation ◽  
Stress Region

Part I of this investigation is mainly focused on fatigue tests of full scale turbine blades, based on the observation of the phenomena that some directional solidification (DS) blades do not fracture at their maximum stress region, and it has been revealed that there exists material's fatigue property variation among different regions of DS blades. For more in-depth and quantitative study on the fatigue property variation, Part II of this investigation designs and fabricates four types of DS bladelike specimens (including platform-, shroud-, body-, and rootlike specimens), which imitate the geometry, microstructure, and stress features of a full scale turbine blade on its four typical regions, to conduct the low cycle fatigue (LCF) tests. Test results show that the bodylike specimen has the best fatigue performance, and under the same stress state, the fatigue life of root-, shroud-, and platformlike specimens are 29.1%, 28.5%, and 13.7% of the bodylike specimen, respectively. The large material's fatigue property variation among different regions of DS blades should be considered in future blade life design.

scholarly journals Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4070
Author(s):  
Andrea Karen Persons ◽  
John E. Ball ◽  
Charles Freeman ◽  
David M. Macias ◽  
Chartrisa LaShan Simpson ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Prediction Models ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Wearable Sensors ◽  
Fatigue Tests ◽  
Proof Of Concept ◽  
Cycle Fatigue ◽  
Wearable Sensing ◽  
Failure Data

Standards for the fatigue testing of wearable sensing technologies are lacking. The majority of published fatigue tests for wearable sensors are performed on proof-of-concept stretch sensors fabricated from a variety of materials. Due to their flexibility and stretchability, polymers are often used in the fabrication of wearable sensors. Other materials, including textiles, carbon nanotubes, graphene, and conductive metals or inks, may be used in conjunction with polymers to fabricate wearable sensors. Depending on the combination of the materials used, the fatigue behaviors of wearable sensors can vary. Additionally, fatigue testing methodologies for the sensors also vary, with most tests focusing only on the low-cycle fatigue (LCF) regime, and few sensors are cycled until failure or runout are achieved. Fatigue life predictions of wearable sensors are also lacking. These issues make direct comparisons of wearable sensors difficult. To facilitate direct comparisons of wearable sensors and to move proof-of-concept sensors from “bench to bedside,” fatigue testing standards should be established. Further, both high-cycle fatigue (HCF) and failure data are needed to determine the appropriateness in the use, modification, development, and validation of fatigue life prediction models and to further the understanding of how cracks initiate and propagate in wearable sensing technologies.

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