Blade Failure Research Articles

Study on nickel-based single crystal superalloy DD6 subsurface damage of belt grinding with a large cutting depth of one pass

Single crystal superalloy has been widely utilized as a crucial manufacturing material for aeroengine turbine blades due to its excellent properties. However, machining this alloy is easy to cause subsurface damage, resulting in the engineering failure of blades. To explore a large cutting depth and low damage processing method, this paper established a grinding depth analytical model for the abrasive belt. The model provides insights into the material removal behavior mechanism during belt grinding and predicts the impact of process parameters on the grinding depth. Subsequently, the grinding experiments of this alloy with different abrasive belts were conducted. The experimental results showed that grinding depth increased as normal force amplified and exhibited a nonlinear growth pattern with the reduction of feed velocity. This preliminary verified the prediction model of grinding depth. The material removal properties of the pyramid, diamond, and hollow-sphere belts were analyzed, and the ratio of material removal capacity for the three was found to be 12:8:5. Based on the analysis of the topography and roughness of the grinding surface, the study examined the influence mechanism of grinding force, feed velocity and abrasive grain morphology on grinding depth and surface quality. The subsurface damage behavior mechanism and recrystallization depth change law of belt grinding were revealed. The grinding depth of the pyramid and diamond belts could exceed 160 μm and the recrystallization depth was less than 5 μm. To achieve efficient and low-damage machining, it is recommended to reduce the feed velocity rather than increase the grinding normal force. It is important to note that the feed velocity should not exceed 10 mm/s. This study is to furnish a theoretical groundwork and offer engineering technical recommendations for achieving large grinding depth and low damage machining of single crystal superalloy.

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Design theory for vibration characterisation experiments on real turbine blades with underplatform damper

One of the main causes of turbine rotor blade failures is high-frequency fatigue caused by blade resonance, and the vibration of turbine blades can be effectively suppressed through the reasonable design of dry friction damping structure. In order to understand the vibration characteristics of the blade-disc system and to check whether the damping effect meets the technical specifications, it is necessary to design and carry out dry friction damping blade vibration characteristics experiment. This paper takes a certain type of underplatform damped turbine blade in production as an example, and briefly describes the design idea and design process of such blade vibration characteristic experiments under the premise of the experiment blade structure, material and other physical parameters.

Effects of uncontrolled combustion in a power plant gas turbine on fracture surface features and microstructural evolutions of a nickel-based superalloy blades

The present work investigates the fracture surface features and microstructural evolutions of nickel-based superalloy (Udimet 500) blades after uncontrolled combustion and overheating in a power plant gas turbine. In normal operation of the turbine, flameout occurred, but fuel continued to flow to hot section of turbine. The injected fuel failed to ignite as intended, but combusted upon contact with hot surfaces, including blades and the exhaust duct. This led to an explosion and the turbine failed after 753 equivalent operating hours (EOH) in normal operation. The majority of the damage was in the second-stage blades, primarily due to their proximity to the exhaust duct. The explosion in the exhaust duct led to the dynamic fracture of the second-stage blades and an increase in temperature, which caused the microstructural degradation of the airfoil part of the blades. The microstructure of the blades was investigated by an optical microscope (OM), a field-emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). The results revealed that the most of microstructure deterioration of the blades occurred in the airfoil of the blades and the microstructure of the root of the blades did not deteriorated since the airfoil experienced a higher temperature in comparison with the root. The degeneration of MC carbide to M23C6 carbide was observed at the airfoil grain boundaries, where M represents Cr and Mo. Furthermore, the morphology of γ' precipitates in the airfoil changed to cauliflower-morphology by growing and splitting mechanisms. The spalling nature of the fracture surface suggested that the dynamic fracture, which is produced by interaction between shock waves, as well as occurred. The failure of gas turbine blades was a consequence of uncontrolled combustion in the turbine section, leading to dynamic fracture and deterioration of the microstructure in the airfoil parts of the blades.

Performance analysis of wind turbine blades using E-Glass fiber and SiO2- Al2O3-TiO2 MMT nanocomposite with AW 106 epoxy

ABSTRACT In a wind turbine, blades are an essential component. In recognition of their remarkable qualities, nanoparticle-reinforced composites (also known as nanocomposites) are becoming increasingly popular among academics and companies. In preceding investigations of wind turbine blades, it was discovered that manufacturing issues, such as cracks in the supporting airfoil transition area, fiberglass, and hardener, were brought on by insufficient resin availability. For the effective investigation of wind turbine blades, a unique e-glass fiber and nanocomposite using AW 106 epoxy have been presented. The primary purpose of this research is on the viability of nanocomposites based on montmorillonite, specifically for use in wind turbine blades. The production and in-depth investigation of nano SiO2-Al2O3-TiO2 montmorillonite dispersed E-glass fiber/AW 106 epoxy composites are the subjects of the investigation of proposed method. The experimental findings were confirmed by GRA and SEM analysis in ANSYS to predict wind turbine blade failures, evaluate the blades’ hardness, and test the edge and flap loading conditions. As the result, demonstrated that nanocomposite has a tensile strength of Al2O3with 1% high with a value of 106 MPa, Al2O3with 1% withstands the highest number of failure cycles with 273, Rockwell number is 43, and the maximum value of Al2O3is 0.992 in GRA with various materials.

Strategic Quality Control Measures to Reduce Defects in Composite Wind Turbine Blades

Wind turbine blades are made from polymer composites to provide high specific stiffness, strength, and good fatigue performance. However, large composite structures are prone to manufacturing defects such as delamination and adhesive failure, which can lead to crack initiation and propagation under cyclic stresses. National renewable energy laboratory, USA statistics shows 26% fatigue failure modes are created by laminate and adhesive joint manufacturing errors. A range of manufacturing processes are used to construct wind turbine blades. Resin transfer infusion is one of the most frequently used methods in wind turbine blade manufacturing industry. This paper provides assessment on regular defects occurring in resin transfer infusion processes which lead to poor quality in wind turbine blade manufacture. The assessment is based on the existing literature and the know-how generated from manufacturing wind turbine blades. The effect of these defects for the structural failure of composite wind turbine blades is analysed. The final phase of the study provides manufacturing quality control measures which can be implemented to improve the composite wind turbine blade manufacturing process.

The Effect of Ply Waviness for the Fatigue Life of Composite Wind Turbine Blades

Wind turbine blade failure is one of the most prominent types of damage occurring in operating wind turbine systems. Glass fibre materials are mainly used for producing wind turbine blades and they consist of large tows, stitched fibres, which are prone to generate imperfections such as ply waviness. The primary objective of this research was to evaluate the effect of ply waviness on fatigue life of typical composites used in wind turbine blades. This study involves two main areas: Finite elements analysis (FEA) and experimental testing. The Finite element analysis was carried out using the commercial code from ESI group. The experimental work was carried out by manufacturing specimens from glass fibre with regular waviness and testing for static and fatigue failure. The tensile static test data was used to identify the effect of ply waviness for failure strength. Cycles to failure (S-N) curves were developed for two different wave profiles based on fatigue testing data. The long term aim of this ongoing research is to improve current fatigue life estimation methods applicable to composite wind turbine blades.

Investigation on the vibration localization of mistuned bladed disk with frictional contact

The mistuning phenomenon is commonly seen in the bladed assemblies of turbomachinery, leading to an unreasonably localized energy distribution that may increase the risk of high cycle fatigue and potentially cause blade failure. The friction coupling interaction is often introduced to attenuate the effect of excessive amplification on the structural vibration. To investigate the vibration localization of damped and mistuned bladed-disk system, a typical mistuning characterization is applied to an improved four-degree-of-freedom lumped parameter model to explicit the vibratory properties with coupled frictional contact. The statistical findings of natural frequency and modal localization factor are obtained by employing the Monte Carlo simulation to explore the influence of mistuned variance and coupled stiffness on the modal localization of free and damped bladed-disk system, respectively. The forced response sensitivity featured in the mistuned variance is quantitatively analyzed from the perspective of vibration localization and energy distribution by the nonlinear solution method. The influence of excitation order and normal load are further, respectively, discussed on the response localization level of the mistuned system. The results can provide fundamental knowledge of the impact of the mistuning pattern on vibration localization for the early design of the aeroengine.

Failure analysis of large and complex engine blades based on experimental research

On a certain day in December 2022, a GE90 engine equipped by an airline experienced a surge during flight. Ground inspection revealed broken blades of the 9-stage high-pressure compressor. To identify the cause of its fracture failure, the macroscopic fracture surface was first analyzed. Obvious fatigue crack propagation characteristics were found at the blade cross-section. Small pits formed by the impact were observed at the crack source location, indicating that the blade was first formed into a circular arc-shaped impact wound after being impacted by an external object. In the subsequent service process, under continuous vibration, fatigue cracks are formed at the impact point as the crack source and gradually propagate, ultimately leading to blade fracture and failure. To further explore the source of foreign objects causing impact damage, the surface scanning method using energy spectrum analysis was used. An enriched region of C element was found near the impact point. However, due to the lack of conditions for the formation of C combustion products at the compressor location, it can be considered that the foreign object may have come from external sources.

Evaluating Mechanical Strength in Vertical-Axis Tidal Turbines: A Comparative Study of Internal Blade Structure and Material Selection through CFD Simulation

Due to the density of water, tidal turbine blades are subject to significantly greater stresses than wind turbine blades. Multiple blade failures occurred during prototype testing as a result of loading conditions and protracted exposure to seawater, which created a severe work environment. The structural integrity of tidal turbine blades is essential for long-term reliability and performance. Numerous investigations into structural performance have been conducted. However, previous research has centred on horizontal-axis tidal turbines, while research on small-scale vertical-axis tidal turbines is limited. This paper aims to compare the Vertical-Axis Tidal Turbine (VATT) structural performance of hollow and solid blade structures in an identical NACA profile using three distinct materials. Finite element analysis (FEA) is employed to construct a model and simulate the mechanical characteristics of VATT blades. The use of static analysis simulation is employed in order to evaluate many parameters, including stress distribution and deflection. Parametric studies are conducted to explore the impact of internal blade structure and materials on mechanical strength. The use of computational fluid dynamics (CFD) simulations is employed for the purpose of analyzing the interaction between blades of vertical axis tidal turbines (VATT) and tidal currents, thereby enabling the assessment of structural loading. According to the simulation results, the hollow profile is subject to significant deflections and stresses. Other data indicates that the utilization of stiffeners in porous structures improves material efficiency and results in lighter blades, although further analysis is needed to investigate fatigue life prediction in optimizing structural design.

Empirijski model koji integriše dimenzionu analizu i Bok-Behnken dizajn za detekciju pukotina u lopaticama ventilatora rotora

Due to continuous operations and manufacturing errors, fatigue cracks can emerge after hours of service; this causes a fan blade failure and potentially ruins an entire engine, turbo machinery, or rotating machinery of a similar kind. This paper focuses on the condition monitoring of the fan blade for detecting cracks occurring in these blades by analyzing the vibration responses. The mathematical formulation is carried out using the matrix method of dimensional analysis, which is dependent on the fundamental quantities of force, Length, Time, and Temperature (FLTƟ) systems of units. Numerical analysis in ANSYS software is done to comprehend the blade harmonic response for the cracked blade condition. Experimentation is also carried out on Tiera fault simulation machinery equipment, where vibration responses are measured and analyzed for crack detection in the blades. The tests were performed for three different cracks of different lengths and analyzed by varying parameters such as load speed, for which experiments are planned using a Box-Behnken design method. The test results were confirmed with the model equations developed, and notable similarities were seen between the analytical, numerical, and experimental analyses. Thus, the proposed study will help detect the cracks in the blades, thus reducing the serious accidents or failure of the machinery.

Improving the oxidation resistance of NiCrAlY-coated superalloy by Zr/ZrN diffusion barrier

The elemental interdiffusion between the bond-coat in thermal barrier coatings and the superalloy substrate has emerged as a critical factor in the failure of turbine blades. In order to mitigate this elemental interdiffusion, a Zr/ZrN diffusion barrier was strategically designed and deposited between the NiCrAlY bond-coat and the superalloy substrate using multi-arc ion plating. The performance of the as-deposited coatings was evaluated through annealing, quenching, thermal cycle oxidation, and isothermal oxidation tests. The microstructural evolutions of the Zr/ZrN diffusion barrier and the NiCrAlY bond-coat were investigated. The Zr/ZrN diffusion barrier exhibited remarkable bonding strength and diffusion barrier effect. Importantly, the structural integrity of the diffusion barrier remained unaffected by thermal stresses during quenching and thermal oxidation tests. Additionally, twins were observed within the ZrN layer after thermal cycle oxidation tests. The application of the Zr/ZrN diffusion barrier layer substantially enhanced the oxidation resistance of NiCrAlY by preventing the depletion of Al. These results suggest that ZrN holds promise as a favorable candidate material for diffusion barriers.

Tip Rubbing as a Rare Metallurgical Root Cause of Gas Turbine Compressor Blade Failure

Tip Rubbing as a Rare Metallurgical Root Cause of Gas Turbine Compressor Blade Failure

Fatigue crack propagation simulation of airfoil section blade under aerodynamic and centrifugal loads

Cracks in aero-engine blades occur frequently due to high-cycle fatigue, which may cause accidents. Most of the existing studies simulating blade crack propagation are performed based on simplified blade shapes (rectangular, etc) or single loads (tension, bending, torsion, etc). These simplified treatments lead to a large deviation between the simulated crack propagation law and the actual blade propagation process. To fill the gap, the surface crack propagations of airfoil section blades under aerodynamic load, centrifugal load and the combined action of two loads are simulated based on the combined simulation of FRANC3D and ANSYS. The proposed method is verified by comparing the results with those obtained from the literature and experiment, respectively. In addition, the surface crack propagation path and the change of stress distribution during crack propagation under different loads are simulated. The results show that the crack propagates to the trailing edge (TE) and leading edge (LE) under aerodynamic load and centrifugal load, respectively. In addition, the cracks show three-dimensional shape characteristics under a single load. However, the crack propagates approximately along the plane under the combined action of two loads. The study can provide a theoretical basis for cracked blade failure analysis.

Analysis of fatigue fracture incident of centrifugal compressor blades in a small turbojet engine

In this study, performance verification tests were conducted on a small turbojet engine, during which a failure occurred at the root of the centrifugal compressor blades, which are made of aluminum alloy. A detailed disassembly and inspection was carried out to reveal the reason of the failure. It was found that the failure of one blade at the root led to jamming of other blades. Then the jammed blades experience sever rubbing and contact with the intake duct. Experimental measurements of material properties and a retrospective examination of the manufacturing process revealed that the yield strength of the material was lower than the design value, and the fillet radius at the blade root was smaller than specifications. The root cause of the fatigue failure of the compressor blades in this incident was attributed to substandard machining quality and material properties, which leads to crack initiation and fatigue propagation until failure occurred. The experience of identifying the root cause would provide engineering guidance for other small turbojet engines.

Investigation on high-dimensional uncertainty quantification and reliability analysis of aero-engine

Accurate quantification of uncertainties is paramount in the contemporary design of aero-engines, demanding substantial computational resources. This investigation introduces an efficient parallel framework for uncertainty quantification, significantly curtailing sample requirements while upholding computational precision. Furthermore, this research tackles the constraints intrinsic to traditional reliability analyses, which often disregard uncertainty, by conceiving an algorithm tailored to aero-engine reliability analysis and lifespan prediction that deliberately accounts for uncertainties. The findings from the uncertainty quantification disclose that the most pivotal factor contributing to the variability in leakage flow rate is unequivocally the variance index of the tip clearance deviation, demonstrating a substantial variance index of 81.52 %. Concerning cooling performance, a remarkable shift is evident, with inlet total temperature fluctuation eclipsing the tip clearance deviation in terms of significance. This transformation is accentuated by a variance index of 54.52 %. Furthermore, the film cooling effectiveness displays notable variability within the uncertainty framework, underscoring that the blades may be subjected to more severe thermal corrosion and thermal fatigue during operational conditions than initially envisioned. Reliability calculations elucidate that the probability of blade failure experiences the steepest ascent after approximately 15,500 h of operation, necessitating mandatory overhaul at this juncture.

Thermomechanical fatigue behavior and failure mechanism of a nickel-based directional solidification column crystal superalloy

Thermomechanical fatigue (TMF) is a primary cause of turbine blade failure. TMF tests of a nickel-based directional solidification superalloy, which is a typically used material for turbine blades, are performed out in the surface temperature range of 400 °C–700 °C, two phases (in-phase and out-of-phase, i.e. IP and OP, respectively), three stresses, and two stress ratios. The test results idicate that the TMF life of the OP exceeds that of the IP. An increase in the stress ratio prolongs the TMF life. Scanning electron microscopy and transmission electron microscopy are performed to investigate the failure mechanism. The TMF failure behavior is complex and mainly includes fatigue, creep, and oxidation damage, with a quasi-cleavage fracture mode. Based on the theory of crystal plasticity as well as comprehensively considering the failure mechanism and focusing on the statistical characteristics of the thermal–stress interaction, a TMF constitutive model is established, which explains the differences in TMF behavior between the IP and OP conditions from a theoretical perspective.

Treatment of Failures in Turbine Blades by Cermet Coatings

Treatment of Failures in Turbine Blades by Cermet Coatings

Model-based systems engineering examination of failures ontology in aircraft turbine blades

The concept of Systems Engineering (SE) is widely used in modern times, with approaches based on analyzing the levels and processes of a system. SE approaches are elaborate based on the interpretation of the system's levels and analyzing the whole process. Although such methods are usually used in the analysis of organizations or enormous systems, this effort attempts to show that the same SE analytical tools can be useable in the deepest level of a system. The study focuses on investigating the failure process of a turbine blade, which is considered a system component. The first essential issue in analyzing a system is its interactions with the environment and its effects on the system's internal cybernetics. The study identifies failure processes that cause structural damage as well-defined and tangible processes of microsystem interactions. The research provides a comprehensive architecture of possible failures in an aircraft's jet engine's hot section turbine blades, utilizing a systemic approach and SE tools such as SysML-based models and Domain Mapping Matrices (DMM) to allocate causes of these failures. This research aims to propose an allocated SE-oriented architecture of Failure-Causes in jet engine turbine blades that is more suitable for use in programming.

Fatigue life prediction of mistuned steam turbine blades subjected to deviations in blade geometry

The blades of the steam turbine are subjected to bending of the steam flow, centrifugal loading, vibration response, and structural mistuning. These factors mentioned contribute significantly to the fatigue failure of steam turbine blades. Low pressure (LP) steam turbines experience premature blade and disk failures due to the stress concentrations in the root location of the blade of its bladed disk. This study of mistuned steam turbine blades subjected to variation in blade geometry will be of great significance to the electricity generation industry. A simplified, mistuned, scaled-down steam turbine bladed disk model was developed using ABAQUS finite element analysis (FEA) software. The acquisition of the vibration characteristics and steady-state stress response of the disk models was carried out through FEA. Such studies are very limited. Subsequently, numerical stress distributions were acquired and the model was subsequently exported to Fe-Safe software for fatigue life calculations based on centrifugal and harmonic sinusoidal pressure loading. Vibration characteristics and response of the variation of the geometric blade of the steam turbine were investigated. Natural FEA frequencies compared well with the published literature of real steam turbines, indicating the reliability of the developed FEA model. The study found that fatigue life is most sensitive to changes in blade length, followed by width and then thickness, in this order. Analytical life cycles and Fe-Safe software show a percentage difference of less than 4.86%. This concludes that the numerical methodology developed can be used for real-life mistuned steam turbine blades subjected to variations in blade geometry.