Thermal Fatigue Failure of Low-Pressure Turbine Blade in a Low-Bypass Turbofan Engine

Journal of Failure Analysis and Prevention - Failure of low-pressure (LP) turbine rotor blade in a low-bypass turbofan engine is analyzed to determine its root cause. Forensic and metallurgical...     

Investigation of LP Turbine Blade Failure in a Low Bypass Turbofan Engine

Failure of low pressure turbine rotor blade in a low bypass turbofan engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade failed. The failure has originated from the leading edge and has propagated towards the trailing edge. Intergranular features and high oxidation on the fractured surface are the cause of failure which is probably due to creep-stress rupture. This failure has caused extensive damages in low pressure turbine module and also in downstream modules as a secondary effect. Remedial measures are also suggested to prevent such failures.     

Fatigue Failure of LP Compressor Blade in an Aero Gas Turbine Engine

Failure of low-pressure compressor rotor blade in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade failed. The failure of the first stage rotor blade is found to be the first in the chain of events that led to the engine failure. The mode of failure in the blade is found to be fatigue and has originated from the mounting lug fillet region due to high stress concentrations. The failure has caused extensive damages in low-pressure compressor module and also in downstream modules as a secondary effect. Remedial measures are also suggested to prevent such failures.     

Failure of Low-Pressure Turbine Blades in Military Turbofan Engines: Causes and Remedies

Failure of low-pressure (LP) turbine rotor blades in low bypass military turbofan engines is a great concern for designers, manufactures, repair and overhaul agencies, operators, and airworthiness authorities. The present paper analyzes the LP turbine blade failure cases to determine its root cause. Forensic and metallurgical investigations are carried out on the failed blades. In most cases, the failure was originated from the leading edge and had propagated toward the trailing edge. Intergranular features and high oxidation on the fractured surface have been found as the cause of fatigue failure. Operation at elevated temperatures for considerable time was found responsible for these fatigue failures. Malfunction of fuel system, failure in control sensors, and nonuniformity in atomizer characteristics were the root cause of high temperature in turbine leading to the failure of blades. The paper also presents various remedial measures to address the blade failures from manufacturing and operational points of view.     

Creep Life Degradation and Microstructure Degeneration in a Low-Pressure Turbine Blade of a Military Aircraft Engine

Journal of Failure Analysis and Prevention - Military aircraft engines operate under arduous environmental conditions with rapid throttle excursions as a part of its mission requirements. Life of...     

Failure Analysis of High-Pressure Compressor Blade in an Aero Gas Turbine Engine

Failure of high-pressure compressor rotor blade in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade and failed parts. The failure of the platform ladder is found to the first in the chain of events that led to the compressor blade failure. The mode of failure in the blade is found to be fatigue and has originated from the damaged region on the leading edge caused by dislodgement of platform ladder. The failure has caused extensive damages in high-pressure compressor module and also in downstream turbine blades as a secondary effect.     

Analysis of Low-Pressure Turbine Nozzle Guide Vane Failure in an Aero Gas Turbine Engine: A Computational Approach

Journal of Failure Analysis and Prevention - Failure of low-pressure turbine nozzle guide vane (NGV) in an aero gas turbine engine is analyzed using computational approach. Breakage in the cooling...     

Fatigue Behaviour of Composite T-Joints in Wind Turbine Blade Applications

This paper presents a study of fatigue performance of composite T-joints used in wind-turbine blades. A T-joint with various fibre reinforcement architectures were selected to investigate its fatigue behaviour. The 3D angle interlock T-joint was found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue performance while the increasing rate in life performance is changed with the number of fatigue cycles. A finite element (FE) model was developed that can determine the stress distribution and the initiation and propagation of a delamination crack. The location for through-thickness reinforcement is very important to improve fatigue performance of composite T-joints. Fatigue performance is significantly improved for the web with through-thickness reinforcement while fatigue performance is decreased if the through-thickness reinforcement is applied to the flange-skin regions. The interlaminar veil significantly increases the ultimate strength under static load but fatigue performance at high stress cycles is increased but not significantly.     

Finite Element Approach for Failure Analysis of a Gas Turbine Blade

Journal of Failure Analysis and Prevention - In the present work, a case study on the gas turbine blade is undertaken for failure analysis through finite element approach. The analysis is carried...     

发动机涡轮盘的应变疲劳行为

研究了发动机涡轮盘材料在３０００ｈ应力时效后和未经长时时效状态下的低周疲劳行为，测定了循环稳定和单调拉伸应力－应变曲线，给出了应变－寿命关系。讨论了该材料的循环硬化（软化）特征。     

Finite Element Simulation on Thermal Fatigue of a Turbine Blade with Thermal Barrier Coatings

In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained from finite element simulations, dangerous regions in ceramic coating were determined in terms of the maximum principal stress criterion. The results show that damage preferentially occurs in the chamfer and rabbet of a turbine blade with thermal barrier coatings and its thermal fatigue life decreases with the increase of thermal stress induced by high service temperature.     

汽轮机低压叶片断裂原因分析

针对国产300MW汽轮机低压缸扭叶片发生断裂失效事故进行研究分析;通过对扭叶片有限元计算、叶片振型模态实测,分析该叶片各阶自振频率,其计算结果和模态实测值基本吻合,为事故分析提供理论依据;对叶片材质元素成分测试,并着重对叶片实际运行工况及承受的各种可能的激振力分析,探求导致该级扭叶片疲劳断裂的真实原因,为同类型机组的安全、可靠运行提供一种借鉴作用和分析方法.     

涡轮叶片Bi─Sn致脆研究

研究了Ｋ４０５高温合金精铸涡轮叶片断裂失效的性质与原因。结果表明，叶片制造过程中表面遭受Ｂｉ－Ｓｎ低熔点合金污染，在使用温度与拉应力作用下出现脆性开裂，从而导致早期疲劳断裂失效。     

Failure Analysis of Nozzle Guide Vane of a Low Pressure Turbine in an Aero Gas Turbine Engine

Failure of low pressure turbine nozzle guide vane (NGV) in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the NGV failed as well as the failed components of the downstream modules. Failure in the cooling system in the NGV due to crack in the sealing plate was found to be the cause of NGV getting burnt. This failure has caused extensive damages in low pressure turbine modules. Remedial measures are also suggested to prevent such failures.     

发动机曲轴早期疲劳开裂失效分析

针对某型号发动机曲轴疲劳试验未达到规定载荷累计循环次数,早期疲劳开裂的问题,采用化学成分分析、力学性能测试、断口分析、金相检验和表面氮化层检验等方法对其进行了失效分析。结果表明:该曲轴为疲劳开裂,曲轴过渡圆角处的高应力区存在大尺寸硬质非金属夹杂物是导致曲轴过早疲劳开裂的主要原因;另曲轴过渡圆角处加工质量差,使得该处应力集中加剧,也是致使该曲轴过早疲劳开裂的重要因素。     

Failure of the J79 Engine Compressor Blade Due to Stall

The fractured and damaged compressor rotor blades of a J79 engine have been examined. Optical, stereoscopic, microhardness testing, and SEM examinations were carried out to find out the causes of the fracture. The material of the blades was STS403 and blades were used without coating. From the 15th through the 17th compressor stages the rotor blades, stator vanes, combustion, and turbine sections were damaged. The fractured surface of the 17th blade show multiple origins, secondary cracking in the blade’s convex surface, and extensive propagation before separation and rougher surfaces. The metallographic analysis of the microstructure suggested work hardening. Based on the results, the cause of the fractured blade was high-amplitude fatigue, due to severe stall. After normal engine usage of 5 months, the blade fractured and blade fragments hit the other compressor blades, stators, and casing, and caused damage in both combustion and turbine sections.     

Investigation on Failure in Thermal Barrier Coatings on Gas Turbine First-Stage Rotor Blade

Failure in turbine blades can affect the safety and performance of the gas turbine engine. Results of coating decohesion, erosion and cracking at the first-stage high-pressure (HPT) blade working in gas turbine engine are being reported in this paper. This investigation was carried out for the possibility of various failure mechanisms in the thermal barrier coating exposed to high operating temperature. The blade was made of nickel-based superalloy, having directionally solidified grain structure coated with thermal barrier coatings of yttria-stabilized zirconia with EB-PVD process and platinum-modified aluminum (Pt–Al) bond coat with electro-deposition. The starting point of analysis was apparent coating decohesion close to the leading edge on the suction side of blade. The coating decohesion was found to be widening of interdiffusion zone toward the bond coat at higher operating temperature which could change the composition and induce thermal stresses in the bond coat. The erosion, cracking and decohesion of the coating on the pressure side was also observed during failure investigation. The erosion of the coating was coupled by two factors: one by increase in temperature as demonstrated by change in microstructure of the substrate and second by increase in coating inclination toward the trailing side. As a result of high operating temperature, swelling and thickening of TGO was observed due to outward diffusion of aluminum from the bond coat to form alumina (non-protective oxide) which causes internal stresses that leads to top coat decohesion and cracking. The possibility of hot corrosion was also investigated, and it was found that top coat decohesion did not involve this failure mechanism. Visual inspection, optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy have been used as characterization tools.     

燃气轮机透平喷嘴叶片断裂失效分析

对钴基高温合金断裂叶片进行了宏观检查、化学分析、断口分析、金相检验、扫描电镜和能谱分析.结果表明,叶片断裂的主要原因是高温热腐蚀及硫和矾腐蚀引起叶片壁厚严重减薄且材料老化,导致其强度不足所臻.