Experimental and Numerical Investigation of Vibration Damping Using a Thin Layer Coating

2017 ◽  
Author(s):  
Imran Aziz ◽  
Sajjad Hussain ◽  
Wasim Tarar ◽  
Imran Akhtar
Keyword(s):  
Nickel Alloy ◽  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Rotating Machinery ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Damping Characteristics ◽  
At Resonance ◽  
Vibration Shaker

High cycle fatigue (HCF) is the main cause of failure in rotating machinery especially in aircraft engines which results in the loss of human life as well as billions of dollars. More than 60 percent of aircraft accidents are related to High cycle fatigue. Major reason for HCF is vibratory stresses induced in the blades at resonance. Damping is needed to avoid vibratory stresses to reach the failure level. High speed rotating machinery has to pass through the resonance in order to reach the operational speed and chances of failure are high at resonance level. It is therefore required to suppress the vibrations at resonance level to avoid any damage to the structure. Application of coating to suppress vibrations is a current area of research. Various types of coatings have been studied recently. This includes plasma graded coatings, viscoelastic dampers, piezoelectric material damping, and magnetomechanical damping. In this research, the phenomenon of damping using a coating of nickel alloy on a steel beam is studied experimentally and numerically to reduce vibratory stresses by enhancing damping characteristics to avoid aircraft engine and rotating machinery failure. For this purpose, uncoated and nickel alloy coated steel beams are fabricated. The coating procedure was performed using plasma arc method. The beams were then mounted in a cantilevered position and bump and vibration shaker tests were conducted to determine the natural frequencies and mode shapes. One of the most important parameter to measure the damping of a system is the damping ratio. In order to determine the damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. The vibration analyzer showed the vibration decay as a function of time. Using that decay, damping ratio was calculated by using logarithmic decrement method. In order to investigate and compare the damping characteristics of un-coated and coated beams, forced response method was employed. In this method, beams were excited at 1st and 2nd bending mode natural frequencies using vibration shaker. Results were very encouraging and showed a significant improvement in damping characteristics. The experimental results were then endorsed by numerical results which were achieved by performing modal and forced response analysis using finite element analysis techniques.

Experimental Investigation of Vibration Damping Behavior of Magneto-Mechanical Coated AISI321 Stainless-Steel

2019 ◽  
Author(s):  
Hafiz Muhammad Ashraf ◽  
Farhan Ali
Keyword(s):  
Stainless Steel ◽  
Dynamic Response ◽  
High Speed ◽  
High Cycle Fatigue ◽  
Damping Ratio ◽  
Base Material ◽  
Rotating Machinery ◽  
Cycle Fatigue ◽  
Damping Characteristics ◽  
Aisi 321

Abstract High speed rotating machineries usually operate under severe conditions and enormous loadings and thus, are susceptible to several problems. One such problem that has caught the attention in recent decades is known as High Cycle Fatigue. More than 60 percent of rotating machinery failures has been attributed to this High cycle Fatigue. Along with High Cycle Fatigue, Vibration, an inherent phenomenon in machineries, also share its part in failure of rotating machineries. Rotating machinery components suffer from high amplitude vibrations when they pass through resonance. Stresses are developed as a result of these vibrations and fatigue in mechanical structures, providing a conducive environment for the development of cracks at Surface. When these surface cracks reach critical size, crack nucleation starts, which ultimately leads to catastrophic failures. So, in order to avoid the disastrous consequences, damping is needed. Damping keeps material’s integrity in case of impact forces, stresses due to thermal shocks in turbo machinery and earth quakes in huge structures. Thin layer of magneto elastic coating can be applied on substrate surface that acts as first line of defense. Large number of coating Processes are available around the globe. The optimized combination of coating material, substrate material and coating technique according to specific application is necessary. These coatings have the capability to combat the phenomenon of oxidation, wear and fatigue acting as a barrier between substrate and hostile environments. Further, they enhance the damping characteristics, and thus allows the high-speed rotating machinery to reach its operational speed without any failure at resonance. In this way, they not only enhance the performance of components in aggressive environments, but also improve the life cycle, saving assets of millions of dollars’ worth. This research is an endeavor to experimentally investigate effect of magneto mechanical coating on damping of AISI 321 Stainless steel. AISI 321 was selected as base material because of its wide applications in engine components of gas turbines, heat exchangers and in different chemical industries. Two types of Air plasma sprayed magneto-mechanical powder (NiAl & CoNiCrAlY) were coated on base material and thickness was maintained up to 250μm in both the cases. Experiments were designed and performed on cantilever beam specimens for dynamic response measurement. Dynamic response of the system was measured to investigate the modal parameters of natural frequencies, damping ratio and time of vibration decay. For damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. Vibration analyzer showed the vibration decay as a function of time. Logarithmic decrement method was used to calculate the damping ratio in both cases. Dynamic response of all the three cases (NiAl coating, CoNiCrAlY and uncoated AISI321) were compared. Results were very reassuring and showed a significant improvement in damping characteristics.

Experimental Investigation of Vibration Damping Behavior of Magneto-Mechanical Coated AISI321 Stainless-Steel

2020 ◽  
Author(s):  
Hafiz Muhammad Ashraf ◽  
Farhan Ali ◽  
Muhammad Imran Sadiq
Keyword(s):  
Stainless Steel ◽  
Dynamic Response ◽  
High Cycle Fatigue ◽  
Damping Ratio ◽  
Base Material ◽  
Rotating Machinery ◽  
Cycle Fatigue ◽  
Damping Characteristics ◽  
Aisi 321 ◽  
Rotating Machineries

Abstract High speed rotating machineries usually operate under severe conditions and enormous loadings and thus, are susceptible to several problems. One such problem that has caught the attention in recent decades is known as High Cycle Fatigue. More than 60 percent of rotating machinery failures has been attributed to this High cycle Fatigue. Along with High Cycle Fatigue, Vibration, an inherent phenomenon in machineries, also share its part in failure of rotating machineries. Rotating machinery components suffer from high amplitude vibrations when they pass through resonance. Stresses are developed as a result of these vibrations and fatigue in mechanical structures, providing a conducive environment for the development of cracks at Surface. When these surface cracks reach critical size, crack nucleation starts, which ultimately leads to catastrophic failures. So, in order to avoid the disastrous consequences, damping is needed. Damping keeps material’s integrity in case of impact forces, stresses due to thermal shocks in turbo machinery and earth quakes in huge structures. Thin layer of magneto elastic coating can be applied on substrate surface that acts as first line of defense. Large number of coating Processes are available around the globe. The optimized combination of coating material, substrate material and coating technique according to specific application is necessary. These coatings have the capability to combat the phenomenon of oxidation, wear and fatigue acting as a barrier between substrate and hostile environments. Further, they enhance the damping characteristics, and thus allows the highspeed rotating machinery to reach its operational speed without any failure at resonance. In this way, they not only enhance the performance of components in aggressive environments, but also improve the life cycle, saving assets of millions of dollars’ worth. This research is an endeavor to experimentally investigate effect of magneto mechanical coating on damping of AISI 321 Stainless steel. AISI 321 was selected as base material because of its wide applications in engine components of gas turbines, heat exchangers and in different chemical industries. Two types of Air plasma sprayed magneto-mechanical powder (NiAl & CoNiCrAlY) were coated on base material and thickness was maintained up to 250μm in both the cases. Experiments were designed and performed on cantilever beam specimens for dynamic response measurement. Dynamic response of the system was measured to investigate the modal parameters of natural frequencies, damping ratio and time of vibration decay. For damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. Vibration analyzer showed the vibration decay as a function of time. Logarithmic decrement method was used to calculate the damping ratio in both cases. Dynamic response of all the three cases (NiAl coating, CoNiCrAlY and uncoated AISI321) were compared. Results were very reassuring and showed a significant improvement in damping characteristics.

Aeroelastic Analysis of NREL Wind Turbine

2017 ◽  
Author(s):  
Yaozhi Lu ◽  
Fanzhou Zhao ◽  
Loic Salles ◽  
Mehdi Vahdati
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Measured Data ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Aeroelastic Analysis

The current development of wind turbines is moving toward larger and more flexible units, which can make them prone to fatigue damage induced by aeroelastic vibrations. The estimation of the total life of the composite components in a wind turbine requires the knowledge of both low and high cycle fatigue (LCF and HCF) data. The first aim of this study is to produce a validated numerical model, which can be used for aeroelastic analysis of wind turbines and is capable of estimating the LCF and HCF loads on the blade. The second aim of this work is to use the validated numerical model to assess the effects of extreme environmental conditions (such as high wind speeds) and rotor over-speed on low and high cycle fatigue. Numerical modelling of this project is carried out using the Computational Fluid Dynamics (CFD) & aeroelasticity code AU3D, which is written at Imperial College and developed over many years with the support from Rolls-Royce. This code has been validated extensively for unsteady aerodynamic and aeroelastic analysis of high-speed flows in gas turbines, yet, has not been used for low-speed flows around wind turbine blades. Therefore, in the first place the capability of this code for predicting steady and unsteady flows over wind turbines is studied. The test case used for this purpose is the Phase VI wind turbine from the National Renewable Energy Laboratory (NREL), which has extensive steady, unsteady and mechanical measured data. From the aerodynamic viewpoint of this study, AU3D results correlated well with the measured data for both steady and unsteady flow variables, which indicated that the code is capable of calculating the correct flow at low speeds for wind turbines. The aeroelastic results showed that increase in crosswind and shaft speed would result in an increase of unsteady loading on the blade which could decrease the lifespan of a wind turbine due to HCF. Shaft overspeed leads to significant increase in steady loading which affects the LCF behaviour. Moreover, the introduction of crosswind could result in significant dynamic vibration due to forced response at resonance.

A Methodology for High Cycle Fatigue Characterization of Lead-Free Interconnects Under Simultaneous Harsh Environments of High Temperature and Vibration

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye
Keyword(s):  
High Temperature ◽  
High Speed ◽  
High Cycle Fatigue ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Natural Frequencies ◽  
Image Correlation ◽  
Lead Free ◽  
Cycle Fatigue ◽  
Increase With Increase

Current trends in the automotive industry warrant a variety of electronics for improved control, safety, efficiency and entertainment. Many of these electronic systems like engine control units, variable valve sensor, crankshaft-camshaft sensors are located under-hood. Electronics installed in under-hood applications are subjected simultaneously to mechanical vibrations and thermal loads. Typical failure modes caused by vibration induced high cycle fatigue include solder fatigue, copper trace or lead fracture. The solder interconnects accrue damage much faster when vibrated at elevated temperatures. Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. Presently, the literature on mechanical behavior of lead-free alloys under simultaneous harsh environment of high-temperature vibration is sparse. In this paper, the reduction in stiffness of the PCB with temperature has been demonstrated by measuring the shift in natural frequencies. The test vehicle consisting of a variety of lead-free SAC305 daisy chain components including BGA, QFP, SOP and TSOPs has been tested to failure by subjecting it to two elevated temperatures and harmonic vibrations at the corresponding first natural frequency. The test matrix includes three test temperatures of 25C, 75C and 125C and simple harmonic vibration amplitude of 10G which are values typical in automotive testing. PCB deflection has been shown to increase with increase in temperature. The full field strain has been extracted using high speed cameras operating at 100,000 fps in conjunction with digital image correlation. Material properties of the PCB at test temperatures have been measured using tensile tests and dynamic mechanical analysis. FE simulation using global-local finite element models is thus correlated with the system characteristics such as modal shapes, natural frequencies and displacement amplitudes for every temperature. The solder level stresses have been extracted from the sub-models. Stress amplitude versus cycles to failure curves are obtained at all the three test temperatures. A comparison of failure modes for different surface mount packages at elevated test temperatures and vibration has been presented in this study.

Smart Structures: Gas Turbine Engine Applications

2001 ◽  
Author(s):  
Sanford Fleeter ◽  
Patrick B. Lawless
Keyword(s):  
Gas Turbine ◽  
Smart Materials ◽  
High Cycle Fatigue ◽  
Smart Structures ◽  
Forced Response ◽  
Smart Structure ◽  
Turbine Engines ◽  
Cost Ratio ◽  
Gas Turbine Engines ◽  
Cycle Fatigue

Abstract This paper is directed at providing the smart structure technology community an introduction to aircraft gas turbine engines issues that might be addressed, i.e. smart/active propulsion systems. Specifically, in gas turbine engines, smart structures can (1) influence performance, stability, noise and high cycle fatigue by providing airfoil aerodynamic control, (2) alleviate or avoid high cycle fatigue due to flutter and forced response by introducing damping intra structures, and (3) provide health monitoring. However, the benefits-to-cost ratio of the added complexity of incorporating smart materials into gas turbine engines must be large as smart materials and actuator/control systems are not a simple solution to complex problems. The prime selling point of smart structure technology to current state-of-the-art gas turbine engines may be adaptability to age, mission, and the environment.

A Diagnosis of Failure of a Compressor Blade

1987 ◽  
Author(s):  
J. A. Kubiak ◽  
J. M. Franco ◽  
A. Carnero ◽  
A. Rothhirsch L ◽  
J. Aguirre R.
Keyword(s):  
Finite Element ◽  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Welded Joint ◽  
Compressor Blade ◽  
Finite Element Code ◽  
Cycle Fatigue ◽  
Start Up ◽  
Load Conditions

The methodology and the procedure of diagnosis of a cracked stationary blade of a compressor due to high cycle fatigue is presented. The natural frequencies of the blades and a stator row were measured and an analysis of the casing vibrations during start-up and under load conditions of the compressor was conducted in a search for the cause of the failure. Using finite element code the natural frequencies and the vibratory stresses of the stator row blades (vanes) were computed. The computed maximum vibratory stresses in the vane were concentrated in the location of the crack which originated from the welded joint. It was concluded that the welded joint requires modification.

Cracking Mechanism and Retrofit Design of Governing Stage Blades for a Steam Turbine

2008 ◽  
Vol 392-394 ◽  
pp. 967-974
Author(s):  
Z.L. Xu ◽  
S.N. He ◽  
Bo Shangguan
Keyword(s):  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Cycle Fatigue ◽  
Steam Turbines ◽  
Mode Shift ◽  
Assembly Tolerance ◽  
Right Reason ◽  
The Right ◽  
Retrofit Design ◽  
Electronic Microscope

Cracking of blade dovetails occurred in a governing stage of a 50MW steam turbines twice within 5 months. To find out the failure mechanism and measures to avoid the failure accident, one of the cracked blades has been inspected by the metallography and a scanning electronic microscope. The inspection results show that the cracking of the blade is caused by the high cycle fatigue. When governing stage blades are in operation, the vibration of blades can extend to platform or even to dovetail parts over radial supporting surfaces depending on temperature, centrifugal force and assembly tolerance. The calculated results by FEM show that not only natural frequencies of blades in operating are smaller than that in stationary but also the modal order shifts when the blade runs from stationary to operation states. The effect of mode shift on the failure was investigated. According to the conclusion, the blades have been retrofitted by increasing neck of dovetail to avoid dangerous resonance, and the blades have been operating in healthy condition for two years after the modification. Contrarily, if the phenomenon of mode shift were ignored, it would be difficult to find out the right reason of resonance and ways to retrofit the damaged blades.

High Cycle Fatigue Life-Prediction for Lead-Free Interconnects Under Simultaneous High Temperature and Vibration

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye
Keyword(s):  
High Temperature ◽  
High Speed ◽  
High Cycle Fatigue ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Natural Frequencies ◽  
Image Correlation ◽  
Lead Free ◽  
Cycle Fatigue ◽  
Increase With Increase

Current trends in the automotive industry warrant a variety of electronics for improved control, safety, efficiency and entertainment. Many of these electronic systems like engine control units, variable valve sensor, crankshaft-camshaft sensors are located under-hood. Electronics installed in under-hood applications are subjected simultaneously to mechanical vibrations and thermal loads. Typical failure modes caused by vibration induced high cycle fatigue include solder fatigue, copper trace or lead fracture. The solder interconnects accrue damage much faster when vibrated at elevated temperatures. Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. Presently, the literature on mechanical behavior of lead-free alloys under simultaneous harsh environment of high-temperature vibration is sparse. In this paper, the reduction in stiffness of the PCB with temperature has been demonstrated by measuring the shift in natural frequencies. The test vehicle consisting of a variety of lead-free SAC305 daisy chain components including BGA, QFP, SOP and TSOPs has been tested to failure by subjecting it to two elevated temperatures and harmonic vibrations at the corresponding first natural frequency. The test matrix includes three test temperatures of 25C, 75C and 125C and simple harmonic vibration amplitude of 10G which are values typical in automotive testing. PCB deflection has been shown to increase with increase in temperature. The full field strain has been extracted using high speed cameras operating at 100,000 fps in conjunction with digital image correlation. Material properties of the PCB at test temperatures have been measured using tensile tests and dynamic mechanical analysis. FE simulation using global-local finite element models is thus correlated with the system characteristics such as modal shapes, natural frequencies and displacement amplitudes for every temperature. The solder level stresses have been extracted from the sub-models. Stress amplitude versus cycles to failure curves are obtained at all the three test temperatures. A comparison of failure modes for different surface mount packages at elevated test temperatures and vibration has been presented in this study.

scholarly journals Investigation of the suspension design and ride comfort of an electric mini off-road vehicle

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882335 ◽  
Author(s):  
Bin Yu ◽  
Zhice Wang ◽  
Guoye Wang ◽  
Jianzhu Zhao ◽  
Liyang Zhou ◽  
...  
Keyword(s):  
Shock Absorber ◽  
Natural Frequencies ◽  
Ride Comfort ◽  
Piecewise Linear ◽  
Damping Ratio ◽  
Road Vehicle ◽  
Pulse Input ◽  
Response Characteristics ◽  
Quarter Car Model ◽  
Damping Characteristics

In view of the little research that has been conducted on the ride comfort of mini vehicles, an electric mini off-road vehicle was designed in this study and a 2 degree-of-freedom quarter car model was established to investigate the ride comfortability. The amplitude-frequency and vibration response characteristics of the suspension were analyzed with the natural frequencies of the front and rear suspensions selected in accordance with the required driving performance. A comprehensive objective function with respect to the safety and comfortability was established, and the damping ratio of the suspension was determined. The damping characteristics of the shock absorber were analyzed to derive an adjustment rule of the suspension damping ratio. The piecewise linear speed characteristics of the shock absorber were subsequently obtained, and suspension-parameter identification and ride comfort tests were conducted. The test results showed that the natural frequencies and damping ratios of the front and rear suspensions were 1.676 and 1.922 Hz, and 0.225 and 0.242, respectively. The results of a pulse input test and D-level road random running test also demonstrated the safety and good ride comfortability of the vehicle.

Experimental Study of Aerodynamic and Structural Damping in a Full-Scale Rotating Turbine

2001 ◽  
Author(s):  
Jason J. Kielb ◽  
Reza S. Abhari
Keyword(s):  
High Cycle Fatigue ◽  
Physical Nature ◽  
Forced Response ◽  
Vibration Modes ◽  
Cycle Fatigue ◽  
Structural Damping ◽  
Large Component ◽  
Blade Vibration ◽  
Aerodynamic Damping ◽  
Turbomachinery Blades

Damping in turbomachinery blades has been an important parameter in the study of forced response and high cycle fatigue, but because of its complexity the sources and physical nature of damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and structural damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic damping was a large component of the total damping for all modes. A study of structural damping as a function of rotational speed was also included to show the effect of friction damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous structural and aerodynamic damping measurement under engine-level rotational speeds.

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