The Experts below are selected from a list of 996 Experts worldwide ranked by ideXlab platform
V. Rastogi - One of the best experts on this subject based on the ideXlab platform.
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Vibration analysis for detecting failure mode and crack location in first stage gas turbine Blade
Journal of Mechanical Science and Technology, 2019Co-Authors: S. Rani, A.k. Agrawal, V. RastogiAbstract:Structure frequency response testing “modal analysis” is an integral part of the development and testing of structures such as pistons, turbine Blades, compressor Blades, crankshafts, and connecting rods. The usefulness of this technique lies in the fact that the energy in an impulse input is distributed continuously in the frequency domain. Thus, an impulse force will excite all resonances within given frequency range. To detect a fault in the structure, one may require frequency response functions (FRFs) of structures in both conditions, before (healthy structure) and after (Failed structure) fault occurs. Now by extracting modal properties from collected FRFs and by comparing modal properties, one can detect and locate the structural faults. A case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine Blade made of nickel based super alloy IN738LC, which has Failed after rendering a useful life of 72000 h. The root causes of failure are detected by comparing the Failed Blade experimental model with the Failed Blade computational model. It is observed that the frequencies of the real Failed Blade experimental model are lesser than the computational model of the Failed turbine Blade. This is due to the metallurgical defects, which result in loosening of stiffness at the leading and trailing edges of the Blade. Further, the stress concentration areas noticed on leading and trailing edges in computational model of the Failed Blade at the sixth mode are well corroborated with the cracked zone seen on leading and trailing edges of a real case Failed turbine Blade, collected from the site. It is concluded that the Blade has Failed due to that the resonance at sixth modal frequency. Scanning electron microscope (SEM) images reveal the presence of corrosion pits on the surfaces of the turbine Blade that lead to surface degradation, which results in crack initiation and its propagation with high-cycle fatigue. It is concluded that the failure of turbine Blade occurs due to high cycle fatigue.
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Vibration analysis for detecting failure mode and crack location in first stage gas turbine Blade
Journal of Mechanical Science and Technology, 2019Co-Authors: S. Rani, A.k. Agrawal, V. RastogiAbstract:Structure frequency response testing “modal analysis” is an integral part of the development and testing of structures such as pistons, turbine Blades, compressor Blades, crankshafts, and connecting rods. The usefulness of this technique lies in the fact that the energy in an impulse input is distributed continuously in the frequency domain. Thus, an impulse force will excite all resonances within given frequency range. To detect a fault in the structure, one may require frequency response functions (FRFs) of structures in both conditions, before (healthy structure) and after (Failed structure) fault occurs. Now by extracting modal properties from collected FRFs and by comparing modal properties, one can detect and locate the structural faults. A case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine Blade made of nickel based super alloy IN738LC, which has Failed after rendering a useful life of 72000 h. The root causes of failure are detected by comparing the Failed Blade experimental model with the Failed Blade computational model. It is observed that the frequencies of the real Failed Blade experimental model are lesser than the computational model of the Failed turbine Blade. This is due to the metallurgical defects, which result in loosening of stiffness at the leading and trailing edges of the Blade. Further, the stress concentration areas noticed on leading and trailing edges in computational model of the Failed Blade at the sixth mode are well corroborated with the cracked zone seen on leading and trailing edges of a real case Failed turbine Blade, collected from the site. It is concluded that the Blade has Failed due to that the resonance at sixth modal frequency. Scanning electron microscope (SEM) images reveal the presence of corrosion pits on the surfaces of the turbine Blade that lead to surface degradation, which results in crack initiation and its propagation with high-cycle fatigue. It is concluded that the failure of turbine Blade occurs due to high cycle fatigue.
S. Rani - One of the best experts on this subject based on the ideXlab platform.
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Vibration analysis for detecting failure mode and crack location in first stage gas turbine Blade
Journal of Mechanical Science and Technology, 2019Co-Authors: S. Rani, A.k. Agrawal, V. RastogiAbstract:Structure frequency response testing “modal analysis” is an integral part of the development and testing of structures such as pistons, turbine Blades, compressor Blades, crankshafts, and connecting rods. The usefulness of this technique lies in the fact that the energy in an impulse input is distributed continuously in the frequency domain. Thus, an impulse force will excite all resonances within given frequency range. To detect a fault in the structure, one may require frequency response functions (FRFs) of structures in both conditions, before (healthy structure) and after (Failed structure) fault occurs. Now by extracting modal properties from collected FRFs and by comparing modal properties, one can detect and locate the structural faults. A case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine Blade made of nickel based super alloy IN738LC, which has Failed after rendering a useful life of 72000 h. The root causes of failure are detected by comparing the Failed Blade experimental model with the Failed Blade computational model. It is observed that the frequencies of the real Failed Blade experimental model are lesser than the computational model of the Failed turbine Blade. This is due to the metallurgical defects, which result in loosening of stiffness at the leading and trailing edges of the Blade. Further, the stress concentration areas noticed on leading and trailing edges in computational model of the Failed Blade at the sixth mode are well corroborated with the cracked zone seen on leading and trailing edges of a real case Failed turbine Blade, collected from the site. It is concluded that the Blade has Failed due to that the resonance at sixth modal frequency. Scanning electron microscope (SEM) images reveal the presence of corrosion pits on the surfaces of the turbine Blade that lead to surface degradation, which results in crack initiation and its propagation with high-cycle fatigue. It is concluded that the failure of turbine Blade occurs due to high cycle fatigue.
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Vibration analysis for detecting failure mode and crack location in first stage gas turbine Blade
Journal of Mechanical Science and Technology, 2019Co-Authors: S. Rani, A.k. Agrawal, V. RastogiAbstract:Structure frequency response testing “modal analysis” is an integral part of the development and testing of structures such as pistons, turbine Blades, compressor Blades, crankshafts, and connecting rods. The usefulness of this technique lies in the fact that the energy in an impulse input is distributed continuously in the frequency domain. Thus, an impulse force will excite all resonances within given frequency range. To detect a fault in the structure, one may require frequency response functions (FRFs) of structures in both conditions, before (healthy structure) and after (Failed structure) fault occurs. Now by extracting modal properties from collected FRFs and by comparing modal properties, one can detect and locate the structural faults. A case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine Blade made of nickel based super alloy IN738LC, which has Failed after rendering a useful life of 72000 h. The root causes of failure are detected by comparing the Failed Blade experimental model with the Failed Blade computational model. It is observed that the frequencies of the real Failed Blade experimental model are lesser than the computational model of the Failed turbine Blade. This is due to the metallurgical defects, which result in loosening of stiffness at the leading and trailing edges of the Blade. Further, the stress concentration areas noticed on leading and trailing edges in computational model of the Failed Blade at the sixth mode are well corroborated with the cracked zone seen on leading and trailing edges of a real case Failed turbine Blade, collected from the site. It is concluded that the Blade has Failed due to that the resonance at sixth modal frequency. Scanning electron microscope (SEM) images reveal the presence of corrosion pits on the surfaces of the turbine Blade that lead to surface degradation, which results in crack initiation and its propagation with high-cycle fatigue. It is concluded that the failure of turbine Blade occurs due to high cycle fatigue.
Kulvir Singh - One of the best experts on this subject based on the ideXlab platform.
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Failure Investigation of an Industrial Turbine Blade
Structural Integrity Assessment, 2020Co-Authors: A.h.v. Pavan, G. Jayaraman, M. Swamy, Kulvir SinghAbstract:A 30 MW industrial turbineIndustrial turbine set suffered failure during operation. The unit was shutdown and the turbine casing was opened to realize that a Blade Failed at the root. The root portions of the Failed Blade which were locked in the rotor were dismantled and sent to the laboratory for detailed failure analysis. Chemical analysis indicated that Blades were manufactured as per specification. Microstructural characterization confirmed the presence of uniform tempered martensite, which was in conformance with the material standards. Visual examination and stereomicroscopic examination were carried out and it was observed that one of the root portions showed crack propagation features originating from the clamping pin location while the other portions indicated overload failure kind of features. Field Emission Scanning Electron Microscopic (FESEM) investigation confirmed the location of crack origin at the interface of clamping pin. Fretting debris was not observed at the crack origin eliminating the possibility of fretting fatigue failure mechanism. Elemental analysis using Energy-Dispersive X-ray spectroscopy (EDS) at the crack origin revealed the presence of elements such as Cl, S, Ca, etc. This led to suspicion on the chemistry of water utilized for generation of steam for running the turbine. Upon detailed review of water chemistryWater chemistry, it was confirmed that the same deviated from specified values. It can, therefore, be concluded that crack origin location being a highly stressed region in conjunction with the presence of elements such as Cl, S, Ca, etc., could have caused stress corrosion crackingStress corrosion cracking leading to crack initiation. Subsequent load huntingLoad hunting of the turbine led to fast propagation of this crack to failureTurbine root failure. The comprehensive procedure followed for carrying out failure investigation and detailed results obtained are discussed in this paper.
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Failure Investigation of an Industrial Turbine Blade
Lecture Notes in Mechanical Engineering, 2019Co-Authors: A.h.v. Pavan, G. Jayaraman, M. N. S. Swamy, Kulvir SinghAbstract:A 30 MW industrial turbine set suffered failure during operation. The unit was shutdown and the turbine casing was opened to realize that a Blade Failed at the root. The root portions of the Failed Blade which were locked in the rotor were dismantled and sent to the laboratory for detailed failure analysis. Chemical analysis indicated that Blades were manufactured as per specification. Microstructural characterization confirmed the presence of uniform tempered martensite, which was in conformance with the material standards. Visual examination and stereomicroscopic examination were carried out and it was observed that one of the root portions showed crack propagation features originating from the clamping pin location while the other portions indicated overload failure kind of features. Field Emission Scanning Electron Microscopic (FESEM) investigation confirmed the location of crack origin at the interface of clamping pin. Fretting debris was not observed at the crack origin eliminating the possibility of fretting fatigue failure mechanism. Elemental analysis using Energy-Dispersive X-ray spectroscopy (EDS) at the crack origin revealed the presence of elements such as Cl, S, Ca, etc. This led to suspicion on the chemistry of water utilized for generation of steam for running the turbine. Upon detailed review of water chemistry, it was confirmed that the same deviated from specified values. It can, therefore, be concluded that crack origin location being a highly stressed region in conjunction with the presence of elements such as Cl, S, Ca, etc., could have caused stress corrosion cracking leading to crack initiation. Subsequent load hunting of the turbine led to fast propagation of this crack to failure. The comprehensive procedure followed for carrying out failure investigation and detailed results obtained are discussed in this paper.
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Failure Investigation of Frame 6FA Gas Turbine Compressor Blades
Transactions of the Indian Institute of Metals, 2016Co-Authors: M. Swamy, A.h.v. Pavan, Kulvir Singh, G. JayaramanAbstract:This investigation elucidates failure of a land based 6FA gas turbine compressor 2nd stage Blade. During discussions with site officials, it was learnt that this particular compressor operated in good condition for over 20,000 h at two other sites. In this power station, this was second such failure with less operation duration. Due to failure of Blades, it was requested for a detailed root cause analysis by the utility officials in order to avert such failures in future. Failed Blade samples were collected from the site and cut into the suitable sizes for investigation procedures. Investigation techniques like visual observation, stereomicroscopic, metallographic, scanning electron microscopic examinations (SEM), etc. are employed to ascertain the root cause for failure. During the investigation it was noticed that there is no degradation in the material. During stereomicroscopic examination, a number of beach marks were observed to be present on the fractured surface of the Blade. It was also noticed from both stereomicroscopic and SEM examinations that the Blade Failed due to fatigue. The cracks have originated from micro-cracks developed at the trailing edge during shot peening process in the Blade root. These cracks grew as the Blades have vibrated beyond their natural frequency due to air surge during operation. It was recommended to examine the air filtration mechanism of the compressor regularly.
Roberto Celi - One of the best experts on this subject based on the ideXlab platform.
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Stabilization of Helicopter Blades with Severed Pitch Links Using Trailing-Edge Flaps
2015Co-Authors: Roberto CeliAbstract:The feasibility of using trailing-edge aps to recon gure a helicopter rotor Blade following a failure of the pitch link is addressed, which makes the Blade free oating in pitch and otherwise uncontrollable. A coupled rotor– fuselagemodel is developed thatallowsfor rotor anisotropy.Anew, optimization-based,trimprocedure is developed to determine the dynamics of the Failed Blade and the ap inputs required for recon guration. The trailing-edge ap can correct the otherwise catastrophicconsequences of a pitch link failure. The residual 1 and2/rev (revolution) components of the hub loads are reasonably small with a one-harmonic ap input and essentially disappear if a second harmonic is added to the ap input. The required ap de ections are high but not unreasonable. The ap acts by generating a rigid-body pitching motion of the free- oating Blade that matches the angles that otherwise would have been generated by the swashplate. The steady-state apping motion of the recon gured Blade is very nearly identical to those of the undamaged Blades. The solutions are very sensitive to phase errors in the rst harmonic of the ap inputs. The sensitivity is lower for the constant and the second harmonic inputs. The result suggests that if a helicopter rotor is equipped with trailing-edge aps for other purposes such as vibration or noise reduction, these aps could be used as emergency control surfaces. Nomenclature Ix x, Iyy, Izz = mass moments of inertia of the helicopter about its body axes m = mass of the helicopter S = descent direction in optimization procedure for trim X, Y, Z = components of hub forces, lbs X = vector of design variables in trim procedure ¯ = Blade apping angle ±F = ap de ection = advance ratio (aircraft velocity divided by hover Blade tip speed) Á = rigid-body pitch of the Failed Blade à = azimuth angle of the reference Blade (Blade number 1) Ä = rotor spee
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Stabilization of Helicopter Blades with Severed Pitch Links Using Trailing-Edge Flaps
Journal of Guidance Control and Dynamics, 2003Co-Authors: Roberto CeliAbstract:The feasibility of using trailing-edge flaps to reconfigure a helicopter rotor Blade following a failure of the pitch link is addressed, which makes the Blade free floating in pitch and otherwise uncontrollable. A coupled rotor-fuselage model is developed that allows for rotor anisotropy. A new, optimization-based, trim procedure is developed to determine the dynamics of the Failed Blade and the flap inputs required for reconfiguration. The trailing-edge flap can correct the otherwise catastrophic consequences of a pitch link failure. The residual 1 and 2/rev (revolution) components of the hub loads are reasonably small with a one-harmonic flap input and essentially disappear if a second harmonic is added to the flap input. The required flap deflections are high but not unreasonable. The flap acts by generating a rigid-body pitching motion of the free-floating Blade that matches the angles that otherwise would have been generated by the swashplate. The steady-state flapping motion of the reconfigured Blade is very nearly identical to those of the undamaged Blades, The solutions are very sensitive to phase errors in the first harmonic of the flap inputs. The sensitivity is lower for the constant and the second harmonic inputs. The result suggests that if a helicopter rotor is equipped with trailing-edge flaps for other purposes such as vibration or noise reduction, these flaps could be used as emergency control surfaces.
A.h.v. Pavan - One of the best experts on this subject based on the ideXlab platform.
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Failure Investigation of an Industrial Turbine Blade
Structural Integrity Assessment, 2020Co-Authors: A.h.v. Pavan, G. Jayaraman, M. Swamy, Kulvir SinghAbstract:A 30 MW industrial turbineIndustrial turbine set suffered failure during operation. The unit was shutdown and the turbine casing was opened to realize that a Blade Failed at the root. The root portions of the Failed Blade which were locked in the rotor were dismantled and sent to the laboratory for detailed failure analysis. Chemical analysis indicated that Blades were manufactured as per specification. Microstructural characterization confirmed the presence of uniform tempered martensite, which was in conformance with the material standards. Visual examination and stereomicroscopic examination were carried out and it was observed that one of the root portions showed crack propagation features originating from the clamping pin location while the other portions indicated overload failure kind of features. Field Emission Scanning Electron Microscopic (FESEM) investigation confirmed the location of crack origin at the interface of clamping pin. Fretting debris was not observed at the crack origin eliminating the possibility of fretting fatigue failure mechanism. Elemental analysis using Energy-Dispersive X-ray spectroscopy (EDS) at the crack origin revealed the presence of elements such as Cl, S, Ca, etc. This led to suspicion on the chemistry of water utilized for generation of steam for running the turbine. Upon detailed review of water chemistryWater chemistry, it was confirmed that the same deviated from specified values. It can, therefore, be concluded that crack origin location being a highly stressed region in conjunction with the presence of elements such as Cl, S, Ca, etc., could have caused stress corrosion crackingStress corrosion cracking leading to crack initiation. Subsequent load huntingLoad hunting of the turbine led to fast propagation of this crack to failureTurbine root failure. The comprehensive procedure followed for carrying out failure investigation and detailed results obtained are discussed in this paper.
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Failure Investigation of an Industrial Turbine Blade
Lecture Notes in Mechanical Engineering, 2019Co-Authors: A.h.v. Pavan, G. Jayaraman, M. N. S. Swamy, Kulvir SinghAbstract:A 30 MW industrial turbine set suffered failure during operation. The unit was shutdown and the turbine casing was opened to realize that a Blade Failed at the root. The root portions of the Failed Blade which were locked in the rotor were dismantled and sent to the laboratory for detailed failure analysis. Chemical analysis indicated that Blades were manufactured as per specification. Microstructural characterization confirmed the presence of uniform tempered martensite, which was in conformance with the material standards. Visual examination and stereomicroscopic examination were carried out and it was observed that one of the root portions showed crack propagation features originating from the clamping pin location while the other portions indicated overload failure kind of features. Field Emission Scanning Electron Microscopic (FESEM) investigation confirmed the location of crack origin at the interface of clamping pin. Fretting debris was not observed at the crack origin eliminating the possibility of fretting fatigue failure mechanism. Elemental analysis using Energy-Dispersive X-ray spectroscopy (EDS) at the crack origin revealed the presence of elements such as Cl, S, Ca, etc. This led to suspicion on the chemistry of water utilized for generation of steam for running the turbine. Upon detailed review of water chemistry, it was confirmed that the same deviated from specified values. It can, therefore, be concluded that crack origin location being a highly stressed region in conjunction with the presence of elements such as Cl, S, Ca, etc., could have caused stress corrosion cracking leading to crack initiation. Subsequent load hunting of the turbine led to fast propagation of this crack to failure. The comprehensive procedure followed for carrying out failure investigation and detailed results obtained are discussed in this paper.
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Failure Investigation of Frame 6FA Gas Turbine Compressor Blades
Transactions of the Indian Institute of Metals, 2016Co-Authors: M. Swamy, A.h.v. Pavan, Kulvir Singh, G. JayaramanAbstract:This investigation elucidates failure of a land based 6FA gas turbine compressor 2nd stage Blade. During discussions with site officials, it was learnt that this particular compressor operated in good condition for over 20,000 h at two other sites. In this power station, this was second such failure with less operation duration. Due to failure of Blades, it was requested for a detailed root cause analysis by the utility officials in order to avert such failures in future. Failed Blade samples were collected from the site and cut into the suitable sizes for investigation procedures. Investigation techniques like visual observation, stereomicroscopic, metallographic, scanning electron microscopic examinations (SEM), etc. are employed to ascertain the root cause for failure. During the investigation it was noticed that there is no degradation in the material. During stereomicroscopic examination, a number of beach marks were observed to be present on the fractured surface of the Blade. It was also noticed from both stereomicroscopic and SEM examinations that the Blade Failed due to fatigue. The cracks have originated from micro-cracks developed at the trailing edge during shot peening process in the Blade root. These cracks grew as the Blades have vibrated beyond their natural frequency due to air surge during operation. It was recommended to examine the air filtration mechanism of the compressor regularly.
