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.

Investigation on Material's Fatigue Property Variation Among Different Regions of Directional Solidification Turbine Blades—Part I: Fatigue Tests on Full Scale Blades

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Xiaojun Yan ◽  
Xia Chen ◽  
Ruijie Sun ◽  
Ying Deng ◽  
Lianshan Lin ◽  
...  
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Directional Solidification ◽  
Turbine Blades ◽  
Fatigue Property ◽  
Full Scale ◽  
Fatigue Properties ◽  
Casting Method ◽  
Property Variation ◽  
Conventional Casting

At present, directional solidification (DS) made blades are commonly used in high performance turbine for their better high temperature mechanical, especially in creep properties compared with the equiaxed grain (EG) blades made by conventional casting method. To predict DS blades' fatigue life accurately, one of the practical ways is to conduct tests on full-scale blades in a laboratory/bench environment. In this investigation, two types of full scale turbine blades, which are made from DZ22B by DS method and K403 by conventional casting method, respectively, were selected to conduct high temperature combined low and high cycle fatigue (CCF) tests on a special design test rig, to evaluate the increase of fatigue life benefitted from material change. Experimental results show that different from EG blades, DS blades' fracture section is not located on the position where the maximum stress point lies. By comparing fatigue test results of the two types of blade, it can be found that the fatigue properties among different regions of the DS blade are different, and its fatigue damage is not only related to the stress field, but also affected by different parts material's fatigue properties.

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.

Experimental Study of Full-Scale Buckling Restrained Brace With Inspection Windows

2017 ◽  
Author(s):  
C. S. Tsai ◽  
Hui-Chen Su ◽  
T. C. Chiang
Keyword(s):  
Experimental Study ◽  
Energy Dissipation ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Full Scale ◽  
Test Results ◽  
Cycle Fatigue ◽  
Buckling Restrained Brace ◽  
Steel Core ◽  
Testing Protocols

The buckling restrained brace (BRB) has been worldwide accepted as a powerful tool to protect structures from earthquake damage. However, the steel core of the traditional BRB is enclosed by the buckling-restraining unit, it is therefore impossible to observe the condition of the steel core during manufacturing and after earthquakes. Presented in this paper is experimental study on a full-scale buckling restrained brace with inspection windows that allow directly observing the condition of the internal components of the BRB, especially for the steel core. Experimental study in deciding the sizes and locations of the inspection windows to inspect the condition of the steel core during testing without influencing the functionality of the full-scale BRB has been conducted to search for a feasible BRB that is economical and convenient for manufacturing and installation as well as meets testing protocols. Test results of the full-scale BRBs under cyclic loadings showed that the mechanical behavior of the full-scale BRB with inspection windows opened on the buckling-restraining unit was stable and that fracture always occurred at the energy dissipation segments after low cycle fatigue tests. The condition of the steel core can be clearly observed through the inspection windows without dismantling the device during the tests. The test results also indicate that the selected inspection windows on the full-scale BRB have little influence on the strength of the device and that an appropriately designed BRB device with inspection windows can be considered as a stable energy dissipation device. A good indicator to decide the necessity of replacement of the BRB device to prepare for next earthquakes has also been proposed in this study.

Experimental Investigation on the Creep and Low Cycle Fatigue Behaviors of a Serviced Turbine Blade

2019 ◽  
Author(s):  
Zhenlei Li ◽  
Duoqi Shi ◽  
Xiaoguang Yang ◽  
Nina Li
Keyword(s):  
Turbine Blade ◽  
Low Cycle Fatigue ◽  
Test System ◽  
Fatigue Tests ◽  
Test Results ◽  
Cycle Fatigue ◽  
Hold Period ◽  
Low Pressure Turbine ◽  
Creep Fatigue ◽  
Crack Initiation Life

Abstract This paper experimentally investigated the creep and fatigue behaviors of a low-pressure turbine (LPT) blade with 600 hours of service using a novel test system. Pure low cycle fatigue (LCF), pure creep and creep-fatigue interaction (CFI) experiments on the full-scale serviced blades were conducted respectively. Test results showed that the increasing of deformation amplitude was divided into three stages under both pure LCF and creep-fatigue loadings. The deformation of each blade increased rapidly until failure when the test cycle exceeded the 80% of their overall life under the pure LCF and CFI condition. The hold period in creep-fatigue tests shortens the first stage of whole life and has no influence on the proportion of crack initiation life to overall life. The fractures in pure LCF, pure creep and creep-fatigue tests emerged transgranular, intergranular and both transgranular and intergranular behaviors respectively. The crack initiated and propagated in a specific zone of the blade under all the experimental loadings, which limited its creep-fatigue resistance. At last, the remaining life of turbine blade was estimated conservatively by introducing the safety limit into a statistical method.

Modification of Plasma Spurt Spraying on Improving Fatigue Property of Welded Joint

2014 ◽  
Vol 556-562 ◽  
pp. 494-497
Author(s):  
Xiao Hui Zhao ◽  
Yu Liu
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Welded Joint ◽  
Base Alloy ◽  
Fatigue Property ◽  
Fatigue Tests ◽  
Test Results ◽  
Residual Stress Field ◽  
Modification Method ◽  
Nickel Base

The present paper introduces a modification method of welded joint, plasma spurt spraying (MPSS), for improving the fatigue life of welding structure. Nickel-base alloy powder was used to spray the welded joint of Q235B steel. The high cycle fatigue tests of specimens treated by MPSS were carried out to obtain the S-N curves. Meanwhile, numerical simulation was performed to obtain the residual stress field after spraying. Test results show that the fatigue strength of welded joint by MPSS is higher than that of as-welded joint. Based on the test results and simulation results, it can be concluded that MPSS improves fatigue strength mainly through the decrease of stress concentration and residual stress.

scholarly journals Full-scale fatigue tests of CX-100 wind turbine blades. Part II: analysis

2012 ◽  
Author(s):  
Stuart G. Taylor ◽  
Hyomi Jeong ◽  
Jae Kyeong Jang ◽  
Gyuhae Park ◽  
Kevin M. Farinholt ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Full Scale ◽  
Wind Turbine Blades

Buckling Restrained Brace With Inspection Windows

2015 ◽  
Author(s):  
C. S. Tsai ◽  
Yi Liu ◽  
B. Q. Liu
Keyword(s):  
Experimental Study ◽  
Energy Dissipation ◽  
Mechanical Behavior ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Test Results ◽  
Cycle Fatigue ◽  
Buckling Restrained Brace ◽  
Steel Core ◽  
Testing Protocols

The buckling restrained brace (BRB) has been worldwide recognized as an energy absorber to protect structures from earthquake damage. However, the traditional BRB is a fully close design, it is therefore impossible to detect the condition of the steel core during manufacturing and after earthquakes. This paper proposed a buckling restrained brace with inspection windows that allow inspecting the condition of the internal components of the BRB. Experimental study in selecting the sizes and locations of the inspection windows without affecting the functionality of the BRB has been carried out to search for an economically feasible BRB that is convenient for manufacturing and installation and meets testing protocols. Test results of the proposed BRBs under cyclic loadings showed that the mechanical behavior of the BRB with inspection windows on the buckling-restraining unit consisting of the constraining and lateral support elements was stable and that damage always occurred at the energy dissipation segments after low cycle fatigue tests. These test results indicate that the inspection windows opened on the proposed BRB have little influence on the strength of the device and that the proposed device can be considered as a stable energy dissipation device.

Influences of Cyclic Pre-Overload on Low Cycle Fatigue Behaviours of Elbow Pipe

2011 ◽  
Author(s):  
Kazuya Matsuo ◽  
Koji Takahashi ◽  
Kyohei Sato
Keyword(s):  
Low Cycle Fatigue ◽  
Three Dimensional ◽  
Preliminary Test ◽  
Growth Direction ◽  
Fatigue Tests ◽  
Test Results ◽  
Cycle Fatigue ◽  
Crack Penetration ◽  
Crack Growth Direction ◽  
Cumulative Fatigue Damage

Low cycle fatigue tests were conducted using sound elbows made of carbon steel (STPT410). The elbows were subjected to cyclic in-plane bending under displacement control with internal pressure of 9 MPa. The preliminary fatigue tests were conducted under constant cyclic displacements. Then, two test conditions were adopted to investigate the influence of cyclic pre-overload on low cycle behavior of elbow on the basis of the preliminary test results. The fatigue test results were evaluated by using the total usage factor UFTotal (= UFpre+UFpost), where the UFpre and UFpost correspond to usage factor for δpre and δpost, respectively. The fatigue lives of overloaded elbow pipes were estimated based on the cumulative fatigue damage rule basically from UFpre = 0.2 to UFpre = 0.6. In addition, three-dimensional elastic-plastic analyses were carried out using the finite element method. The crack penetration area and the crack growth direction were successfully predicted by the analyses.

Experimental Study of All-Steel Buckling Restrained Brace With Windowed Lateral Support Elements

2014 ◽  
Author(s):  
Chong-Shien Tsai ◽  
Yan-Ming Wang
Keyword(s):  
Energy Dissipation ◽  
Structural Control ◽  
Low Cycle Fatigue ◽  
Control Device ◽  
Fatigue Tests ◽  
Test Machine ◽  
Test Results ◽  
Buckling Restrained Brace ◽  
Steel Core ◽  
The Difference

The buckling restrained brace (BRB) that has been worldwide adopted as a structural control device possesses excellent energy dissipation mechanism and can overcome the disadvantages of the traditional brace. However, the traditional BRB is a fully close design, it is therefore impossible to inspect the condition of the internal components during manufacturing and after earthquakes. This study proposed an all-steel buckling restrained brace with windowed lateral support elements that allow inspecting the internal condition of the BRB. We also studied the optimization in selecting the sizes and positions of the windows in the internal components without affecting its strength to provide an economically feasible all-steel BRB that is convenient for manufacturing and installation and meets the rigorous testing protocols. The all-steel BRB consists of the steel core, lateral support and constraining elements. In this study, scaled all-steel BRBs were tested under cyclic loadings by using an MTS 250 kN test machine. Test results showed that the mechanical behavior of the BRB with windows on the sides of lateral support elements is stable and that damage always occurred at the energy dissipation sections after low cycle fatigue tests. The difference between tensile and compressive forces was small under identical strain, and the accumulated inelastic deformation exceeded the requirement of test protocols. These test results confirm that the windows opened on the proposed BRB have insignificant effects on the strength of the device and that the proposed device meets the design requirement and is thus considered as a stable energy dissipative apparatus.

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