Crack Detection in Shafts of Rotating Machinery Using Active Sensing With an External Excitation on a Bearing

2008 ◽  
Author(s):  
Jose´ M. Machorro-Lo´pez ◽  
Douglas E. Adams ◽  
Julio C. Go´mez-Mancilla
Keyword(s):  
Power Plants ◽  
Crack Detection ◽  
Experimental Tests ◽  
Element Model ◽  
Rotating Machinery ◽  
Mode Shapes ◽  
External Excitation ◽  
Transverse Cracks ◽  
Cracked Shafts ◽  
Cracked Shaft

Because several power plants have undergone burst shafts with catastrophic consequences, methods for detecting cracks in the shafts of rotating machinery are of great interest to the research community. Cracked shafts represent a very small percentage of the vibration issues in machinery (less than 2%) compared with other faults such as misalignment and mass imbalance, which are responsible for 85% of these issues. However, if a cracked shaft is not detected early enough, it can jeopardize the safety of operators and result in high costs for replacement. A method sensitive enough to detect cracks in the shafts of rotating machinery is investigated in this paper. It is shown that changes in the natural frequencies and/or mode shapes are not sensitive enough indicators to detect transverse cracks at the mid-span of shafts in rotating machinery. An exhaustive numerical analysis using a finite element model of a simple machine is conducted to consider many different measurements of the machinery vibratory responses that most clearly detect cracking. It is shown that external excitations applied on a bearing enhance the sensitivity of vibration measurements to cracking. Experimental tests are also used to validate several of the numerical simulation findings.

Cracked Shaft Detection Using the Unbalance Excitation Technique

1995 ◽  
Author(s):  
Farokh H. Kavarana ◽  
R. Gordon Kirk
Keyword(s):  
Crack Detection ◽  
Direct Result ◽  
Response Characteristics ◽  
The Past ◽  
Promising Tool ◽  
Complete Test ◽  
Vibration Signature ◽  
Complete Failure ◽  
Cracked Shafts ◽  
Cracked Shaft

Abstract The ever-growing interest of the modern rotordynamicist in the early detection of rotor cracks in turbomachinery has been the direct result of multiple catastrophic experiences that industry has faced in recent times due to cracked rotors. The complete failure of the rotor due to crack propagation is easily recognized as one of the most serious modes of plant failure. Even though the past decade has witnessed some laudable attempts that have been moderately successful in detecting cracked rotors, this aspect has not received the attention it warrants. A complete test rig has been designed and constructed for experimental research on the response characteristics of cracked rotors, the results of which will permit increased confidence in detecting the presence of rotor cracks in turbomachinery. The rig is capable of testing cracked shafts under the effect of lateral and coupled lateral/torsional vibrations. Conventional vibration signature analysis has been employed for the purpose of crack detection. This paper presents the details of the rig capabilities and results from the unbalance excitation technique applied for crack detection. The response of a cracked shaft differs markedly from that of an uncracked shaft when subjected to a known unbalance. This paper shows that unbalance excitation is a promising tool for cracked shaft detection.

scholarly journals The Experimental Analysis of Vibration Monitoring in System Rotor Dynamic with Validate Results Using Simulation Data

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Hisham A. H. Al-Khazali ◽  
Mohamad R. Askari
Keyword(s):  
Finite Element ◽  
Experimental Analysis ◽  
System Analysis ◽  
Theoretical Data ◽  
Element Model ◽  
Rotating Machinery ◽  
Modal Testing ◽  
Vibration Monitoring ◽  
Mode Shapes ◽  
Computational Techniques

There is a growing tendency today to extract information about the prognostic parameters based on system analysis through various diagnostic techniques to assess the health of the plant or equipment. Vibration monitoring helps in reducing the machine down time. A vibration signature measured at the external surface of machine or at any other suitable place contains a good amount of information to reveal the running condition of the machine. Considering the importance of vibration monitoring in the rotating machinery fault diagnostics, it has been applied in this paper. Effects of modal parameters like natural frequency, mode shapes, and damping, misalignments have been studied. Balancing is usually an expensive and laborious procedure and a balancing system would be beneficial for motor engine and power generation application. In this research, there have been identified unbalance parameters that exist in rotating machinery and develop a finite-element model of rotating dynamics system to create a mathematical model of the system from the test data and subsequently obtaining the unbalanced parameters. During this study, the raw data obtained from the experimental results (Smart Office software) are curve fitted by theoretical data regenerated from simulating it using finite element (ANSYS 12) model for comparisons. The experimental analysis used thus far is called Modal Testing, a well-known and widely used technique in research and industry to obtain the Modal and Dynamic response properties of structures. The technique has recently been applied to rotating structures and some research papers been published, however, the full implementation of Modal Testing in active structures and the implications are not fully understood and are therefore in need of much further and more in-depth investigations. The aim is to find a system identification methodology using the analytical/computational techniques and update the model using experimental techniques already established for passive structures but to active rotating structures, which subsequently help to carry out health monitoring as well as further design and development in rotating machinery.

ANN-Based Crack Identification in Rotor System with Multi-Crack in Shaft

2007 ◽  
Vol 353-358 ◽  
pp. 2463-2466 ◽  
Author(s):  
Tao Yu ◽  
Ying Yang ◽  
Qing Kai Han ◽  
Hong Liang Yao ◽  
Bang Chun Wen
Keyword(s):  
Element Model ◽  
Rotating Machinery ◽  
Rotor System ◽  
Mode Shapes ◽  
Crack Identification ◽  
Fe Model ◽  
Ann Model ◽  
Energy Principle ◽  
Turbo Compressor ◽  
Artificial Neural Network Ann

Rotating machinery, such as steam turbo, compressor, and aeroengine etc., are widely used in many industrial fields. Among the important rotor faults, the fatigue crack fault, which can lead to catastrophic failure and cause injuries and severe damage to machinery if undetected in its early stages, is most difficult to detect efficiently with traditional methods. In the paper, based on the truth of the change of the mode shapes of the cracked structure, a new method by combining accurate finite element model of rotor with multi-crack in shaft and artificial neural network (ANN) is proposed to identify the location and depth of cracks in rotating machinery. First, based on fracture mechanics and the energy principle of Paris, the accurate FE model of the rotor system considering several localized on-edge non-propagating open cracks with different depth, is built to produce the specific mode shapes. Then a set of different mode shapes of a rotor system with localized cracks in several different positions and depths, which will be treated as the input of the designed ANN model, can be obtained by repeating the above step. At last, with several selected crack cases, the errors between the results obtained by using the trained ANN model and FEM ones are compared and illustrated. Meanwhile, the influences of crack in the different position on the identification success are analyzed. The method is validated on the test-rig and proved to have good effectiveness in identification process.

Fault Diagnosis of Wind Turbine Gearboxes

2012 ◽  
Vol 512-515 ◽  
pp. 715-718
Author(s):  
Yu Bai Zhang ◽  
Hui Qun Yuan ◽  
Yin Xin Yu ◽  
Hai Jiang Kou ◽  
Ming Xuan Liang
Keyword(s):  
Wind Turbine ◽  
High Speed ◽  
Fault Location ◽  
Natural Frequencies ◽  
Experimental Tests ◽  
Element Model ◽  
Frequency Domain Analysis ◽  
Mode Shapes ◽  
Frequency Components ◽  
The Finite Element Model

Abnormal vibration appeared when experimental tests was carried out on gearboxes of a 1.5MW wind turbine. In this paper, Time-domain and frequency- domain analysis of test data was implemented based on the method of wavelet denoising, the fault location was determined, and the vibration fault indicators and frequency components were obtained. The finite element model of the gearboxes were established, and the natural frequencies and mode shapes were achieved by calculating. The results showed that the fault occurred in the high speed shaft parts, fault vibration frequency was caused by high-speed shaft eccentric resonance frequency and the frequency generated by the natural frequency and the edge frequency that caused by turning. The research layed the foundation for the study of noise reduction and optimization of the wind turbine gearboxes.

Estimation of Axial Load in Tie-Rods Using Experimental and Operational Modal Analysis

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
S. Campagnari ◽  
F. di Matteo ◽  
S. Manzoni ◽  
M. Scaccabarozzi ◽  
M. Vanali
Keyword(s):  
Axial Load ◽  
Experimental Tests ◽  
Element Model ◽  
Mode Shapes ◽  
Dynamic Measurements ◽  
Indirect Measurements ◽  
New Approach ◽  
Entire Structure ◽  
Model Update ◽  
Tie Rods

This paper addresses a new method for estimating axial load in tie-rods using indirect measurements. This information is of great importance for assessing the health of the tie-rod itself and the health of the entire structure that the beam is inserted into. The method is based on dynamic measurements and requires the experimental estimation of the tie-rod eigenfrequencies and mode shapes at a limited number of points. Furthermore, the approach requires the development of a simple finite element model (FEM), which is then cross-correlated with the experimental data using a model update procedure. Extensive numerical simulations and experimental tests have demonstrated the ability of the new approach to yield accurate estimates of the tie-rod axial load and overcome various limitations of the methods currently available in the literature.

Dynamic Analysis of Composite Plates

2005 ◽  
Author(s):  
Stefan Sorohan ◽  
Ioan Parausanu ◽  
Adrian Motomancea ◽  
Dumitru I. Caruntu
Keyword(s):  
Material Properties ◽  
Orthotropic Plate ◽  
Natural Frequencies ◽  
Composite Plates ◽  
Experimental Tests ◽  
Element Model ◽  
Mode Shapes ◽  
Rigid Rod ◽  
Sand Particles ◽  
Research Stage

The paper presents comparatively the measured and estimated natural frequencies and mode shapes of a rectangular orthotropic panel. The experimental tests were performed using a shaker. The plate was fixed in horizontal position directly on the shaker armature using a rigid rod. The experimental modes shapes were visualized using sand particles. The measured natural frequencies and also the modes shapes correspond to the whole system in motion. So, the analytic model of the plate must include the effect of the vibrator connected to the plates. The purpose of this experimental measurements and analytic modeling of such plates is to further developing a methodology to estimate the material properties of the composite panels. At this research stage, an orthotropic plate with unknown material properties was investigated. Using an adequate finite element model, the mechanical properties of the material were estimated. Using these properties it is possible to numerically estimate the dynamic behavior of the plate for additional sets of boundary conditions.

scholarly journals Interlocking birch plywood structures

2021 ◽  
pp. 095605992110222
Author(s):  
Chrysl A Aranha ◽  
Markus Hudert ◽  
Gerhard Fink
Keyword(s):  
High Surface ◽  
Surface Hardness ◽  
Experimental Tests ◽  
Digital Fabrication ◽  
Element Model ◽  
Component Level ◽  
Geometrical Properties ◽  
Stiffness Properties ◽  
The Face ◽  
Strength And Stiffness

Interlocking Particle Structures (IPS) are geometrically stable assemblies, usually fabricated from plate type elements that are interconnected by slotted joints. IPS are demountable and their components have the potential to be used and reused in different structures and configurations. This paper explores the applicability of birch plywood panels, which are characterized by a high surface hardness, for this type of structural system. Experimental tests were conducted to determine the mechanical properties of birch plywood plates. Moreover, IPS connections with different geometrical properties were investigated for two different load exposures: bending and rotation. The characteristics under bending exposure are influenced by the orientation of the face-veneers. For the rotational load exposure, very small strength and stiffness properties have been identified. A linear elastic finite element model is presented that shows a wide agreement with the test results. The study serves as an initial probe into the performance of IPS structures at the component level. Various aspects that are relevant for the design of IPS, such as the assembly, the accuracy and challenges regarding digital fabrication, the durability, and the structural performance are discussed.

scholarly journals Experimental and Numerical Investigation on the Perforation Resistance of Double-Layered Metal Shield under High-Velocity Impact of Armor-Piercing Projectiles

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 626
Author(s):  
Riccardo Scazzosi ◽  
Marco Giglio ◽  
Andrea Manes
Keyword(s):  
High Strength Steel ◽  
Steel Plate ◽  
Experimental Studies ◽  
Practical Interest ◽  
High Strength ◽  
Experimental Tests ◽  
Element Model ◽  
Transportation Systems ◽  
Metal Shield ◽  
Softening Parameter

In the case of protection of transportation systems, the optimization of the shield is of practical interest to reduce the weight of such components and thus increase the payload or reduce the fuel consumption. As far as metal shields are concerned, some investigations based on numerical simulations showed that a multi-layered configuration made of layers of different metals could be a promising solution to reduce the weight of the shield. However, only a few experimental studies on this subject are available. The aim of this study is therefore to discuss whether or not a monolithic shield can be substituted by a double-layered configuration manufactured from two different metals and if such a configuration can guarantee the same perforation resistance at a lower weight. In order to answer this question, the performance of a ballistic shield constituted of a layer of high-strength steel and a layer of an aluminum alloy impacted by an armor piercing projectile was investigated in experimental tests. Furthermore, an axisymmetric finite element model was developed. The effect of the strain rate hardening parameter C and the thermal softening parameter m of the Johnson–Cook constitutive model was investigated. The numerical model was used to understand the perforation process and the energy dissipation mechanism inside the target. It was found that if the high-strength steel plate is used as a front layer, the specific ballistic energy increases by 54% with respect to the monolithic high-strength steel plate. On the other hand, the specific ballistic energy decreases if the aluminum plate is used as the front layer.

Fluid Added Mass Effect in the Modal Response of a Pump-Turbine Impeller

2009 ◽  
Author(s):  
Eduard Egusquiza ◽  
Carme Valero ◽  
Quanwei Liang ◽  
Miguel Coussirat ◽  
Ulrich Seidel
Keyword(s):  
Natural Frequencies ◽  
Experimental Tests ◽  
Mass Effect ◽  
Added Mass ◽  
Mode Shapes ◽  
Pump Turbine ◽  
Modal Response ◽  
Surrounding Fluid ◽  
Turbine Impeller ◽  
Good Agreement

In this paper, the reduction in the natural frequencies of a pump-turbine impeller prototype when submerged in water has been investigated. The impeller, with a diameter of 2.870m belongs to a pump-turbine unit with a power of around 100MW. To analyze the influence of the added mass, both experimental tests and numerical simulations have been carried out. The experiment has been performed in air and in water. From the frequency response functions the modal characteristics such as natural frequencies and mode shapes have been obtained. A numerical simulation using FEM (Finite Elements Model) was done using the same boundary conditions as in the experiment (impeller in air and surrounded by a mass of water). The modal behaviour has also been calculated. The numerical results were compared with the available experimental results. The comparison shows a good agreement in the natural frequency values both in air and in water. The reduction in frequency due to the added mass effect of surrounding fluid has been calculated. The physics of this phenomenon due to the fluid structure interaction has been investigated from the analysis of the mode-shapes.

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