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。     

某发动机二级涡轮叶片断裂失效分析

在叶片断口宏微观断裂特征观察的基础上,结合叶片的金相组织、力学性能、硬度以及化学成分等,对叶片断裂失效的原因进行了研究.结果表明,发动机二级涡轮叶片失效是由于其中一片涡轮叶片低周疲劳断裂所致.该叶片的低周疲劳断裂失效与源区附近的R槽中的微裂纹、Zr含量偏高、HRC偏高以及断裂处在高应力区等因素有关,且叶片经历了短时超温,其温度约在1050～1100℃之间.     

JT9D—7R4G2型发动机八级压气机盘及叶片失效原因分析

通过对失效的第八级压气机盘和叶片观察和金相分析，探讨了该失效件断裂的原因。结果表明，微动磨损引起疲劳断裂。     

高压涡轮导向叶片裂纹分析

对某发动机高压涡轮导向叶裂纹的性质和产生原因进行了分析。结果表明，导向器叶片裂纹的性质属典型的热疲劳断裂失效，引起该发动机导向叶片热疲劳断裂失效的主要原因是试验温度偏高，温度场分布不均，排气边冷却效果不良也是影响叶片开裂的因素。     

某发动机一级涡轮叶片断裂分析

以某发动机涡轮一级事故叶片为研究对象,对断裂叶片进行了宏、微观形貌观察,硬度测试以及断口成分检查,分析了叶片裂纹的产生与发展过程,探讨了叶片断裂失效的原因。结果表明,叶片断裂模式为机械疲劳断裂。提出了预防措施。     

2Cr13汽轮机叶片断裂分析

对断裂叶片进行了化学成分、力学性能、金相组织以及断口形貌和微区能谱分析。结果表明，叶片的断裂属腐蚀疲劳失效，而运行中存在较大的负荷变动加速了叶片的损坏。提出了改进建议。     

某电厂给水泵汽轮机次末级叶片的失效分析

借助于扫描电子显微镜、硬度测试和疲劳试验等手段,分析了OCr17Ni4Cu4Nb马氏体沉淀硬化不锈钢制叶片的断裂机理和失效原因.分析表明.动叶片的断裂机理为高周疲劳,动叶片的失效原因与电火花强化直接相关.提出了改进方法.     

300MW机组锁口叶片断裂原因分析

通过化学成分分析、力学性能测试、金相检验及断口分析等方法,对某厂300MW机组锁口叶片断裂原因进行了分析。结果表明:叶片的断裂属于高周疲劳断裂,与叶片表面存在的线性缺陷有关。并针对叶片失效情况提出了预防措施。     

应变能密度比准则在块体非晶合金中的应用

由于块体非晶合金独特的原子排列结构,导致其具有独特的力学行为。多年来,国内外研究人员对块体非晶合金的断裂行为进行了一系列的研究,并取得了一定的成果。本文简单介绍了近年来国内外针对块体非晶合金断裂准则的研究状况,随后比较全面地介绍了应变能密度比失效准则,并推导了遵循该准则时断裂角θT(载荷方向与断裂面的夹角)与α(断裂面剪应力与正应力的比值)应满足的关系,最后利用Zr41.2Ti13.8Cu10.0Ni12.5Be22.5块体非晶合金的拉伸实验和已有的实验结果,证实了块体非晶合金遵循应变能密度比失效准则。     

汽车发动机风扇叶片断裂分析

汽车发动机风扇叶片在汽车运行中断裂,对断裂叶片的断口进行了宏、微观分析,并追踪了风扇的生产工艺,探明了叶片失效的主要原因是冲压工艺不当产生了微裂纹,在随后的工作应力作用下,产生疲劳断裂,改进工艺后避免了该类失效事故的发生。     

某型航空发动机压气机四级转子叶片失效分析

某型航空发动机压气机四级转子叶片是故障多发叶片.对叶片典型失效件进行了断口分析,发现叶片故障是由于叶片表面发生腐蚀导致疲劳强度降低,使得叶片在振动应力下发生疲劳失效.进一步对显微组织进行分析,发现叶片材质合乎要求,叶片腐蚀主要是由于使用环境因素造成的.研究结果对于叶片的故障分析及预防具有重要的意义.     

Dynamic and fatigue compressor blade characteristics during fluid-structure interaction: Part I—Blade modelling and vibration analysis

Fatigue failure in blades resulting from alternating loads is a primary cause of aircraft engine failure. In this study, the dynamic and fatigue performance of a compressor blade, which is prone to fatigue failure in practical use, is verified through numerical analysis and tests to identify specific failure causes and ultimately prevent blade failure. Two companion papers describe this work. Part I—blade modelling and vibration analysis establishes a compressor blade model based on reverse engineering and investigates the blade's dynamic characteristics during aerodynamic and structural behaviour interactions under various flight conditions. To accurately describe the dynamic performance of a real blade, three blade models with different fitting precisions are constructed to support dynamic response analysis. In addition, the flow field of each model is constructed to simulate the aerodynamic loads that cause blade vibration. A numerically based analysis of the fluid-structure interaction is subsequently performed. A reasonable calculation model is selected by comparing the dynamic characteristics among these models. The Campbell diagram is analysed to determine resonance probability, and blade failure cause is ultimately verified based on the vibration analysis. The results show that different accuracies in the blade calculation model produce varying degrees of error; the calculation model's ability to reflect the dynamic and fatigue behaviours of a real blade is recommended to be used as a critical evaluation index in the numerical study. The first-order harmonic resonance occurring at critical speeds may contribute to blade failure.     

A case study of BiSn-induced embrittlement

This paper represents the characteristics and causes of the fatigue failure of a turbine blade, which was made of a K405 Ni-base superalloy. The results show that the blade fatigue failure is due to embrittlement, which is induced by the contamination of a Bi---Sn low melting point alloy on the blade surface during the manufacturing process of the blades, under the effects of service temperature and stress.     

Failure analysis of components in compressor vane

The paper presents a failure analysis of components damaged in compressor vane. In order to investigate the damage mechanism and failure causes of components, macroscopic and microscopic observations, microstructural investigations, chemical analysis and hardness measurement have been performed. The results show that the damaged components are caused by fractured blades of 1st stage rotor. In all 1st stage rotor blades, 1^# blade is fractured firstly, and is troublemaker in this incident. The fracture mechanism of 1^# blade fractured from blade root is due to first order bending vibration fatigue damage. The microstructure, hardness and chemical compositions of 1^# blade fracture, all which coincide with technical requirements. The bad shot peening qualities in the surface near blade fracture have important influence on fatigue failure.     

Case study: Analysis of the response of an aircraft structure caused by a propeller blade loss

One of the most severe failures in an aircraft provided with turboprops is an airscrew blade loss. Design precautions must be taken to minimize the hazards to the airplane in the event of a propeller blade failure. One of the hazards which must be considered include structural damage, and the airplane must be designed for the imbalance loads resulting from the failure. The structure must absorb the dynamic loads while the rest of the aircraft continues flying. If the energy of the phenomenon increases until it behaves uncontrollably, the engine could be detached from the structure. There must be devices which react to decrease the risks of critical failure for the rest of the structure. This article is mainly focused on the response of the structure after the break of a propeller blade until the end of the phenomenon. The detached propeller blade is also studied in terms of the size that is lost and its influence on the system behavior. Moreover the effects of stiffness and strength changes on the engine mounting system are analyzed. The research covers different parameters which can influence the phenomenon, including flight condition, propeller rotational frequency, and angular position where the blade is lost. The engine and the engine mounting system have been modeled in a finite element method (FEM). The simulations are run in an explicit solver and the simulation methodology includes failure of elements and non-linear behavior.     

Fracture analysis of compressor blade of a helicopter engine

This paper presents the failure analysis of the blade of a helicopter engine. From the visual examination of the fractured surface, it was possible to observe beach marks, typical of fatigue failure. The crack was initiated from the corrosion pit located on the attack edge of the blade. A non-linear finite element method was utilized to determine the stress state of the blade under rotation (operational conditions). In this analysis an undamaged blade was considered. Computations for the blade, working in the vibration conditions additionally were performed for analysis of phenomena occurring during the blade resonance. In this analysis first three mode of vibration were considered. Attention of this study is devoted to the mechanisms of damage of the compressor blade which works in the condition favorable for the pitting corrosion.     

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.     

Hot corrosion failure in the first stage nozzle of a gas turbine engine

First-stage nozzles of gas turbines, which are the first elements after the combustion chamber, encounter hot gases from the combustion process and have the task of directing the fluid path and increasing the velocity of combustion products. This paper reports on the incidence and failure of the first-stage nozzles of a gas turbine in September 2013 at a seaside pump-house located in the South-West of Iran. The nozzle was made of nickel-based superalloy Nimonic105. Due to nozzle failure, the turbine was damaged severely. The cause of nozzle failure was investigated. The results of visual inspection, XRD analysis of deposits on the blade airfoil, SEM images and EDAX analysis showed the characteristics of hot corrosion. Finite-element analysis (FEM) revealed that the cause of blade trailing edge failure was thermal stress leading to thermal fatigue, which accelerated nozzle blade failure in addition to the hot corrosion.     

镍基单晶合金涡轮叶片开裂原因

某发动机高压涡轮叶片为镍基单晶合金叶片,在室温下进行振动疲劳试验后发现叶片开裂,通过宏观观察、金相检验和扫描电镜分析等方法对叶片开裂的原因进行了分析.结果表明:进气边叶根和榫头伸根的开裂形式均为疲劳开裂;进气边叶根气膜孔内壁存在多处小缺口及榫头伸根亚表面存在疏松缺陷,这些缺陷部位容易形成裂纹源,促进了裂纹的萌生,裂纹扩...     

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.