Experimental verification of detection and prediction of multiple cracks by vibrations, FEM and ANN

2014 ◽  
Vol 10 (3) ◽  
pp. 290-303
Author(s):  
Prasad Ramchandra Baviskar ◽  
Vinod B. Tungikar
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Crack Detection ◽  
Vertical Plane ◽  
Multiple Cracks ◽  
Transverse Cracks ◽  
Content Type ◽  
First Case ◽  
Natural Frequency Analysis ◽  
Good Agreement

Purpose – The purpose of this paper is to address the determination of crack location and depth of multiple transverse cracks by monitoring natural frequency and its prediction using Artificial Neural Networks (ANN). An alternative to the existing NDTs is suggested. Design/methodology/approach – Modal analysis is performed to extract the natural frequency. Analysis is performed for two cases of cracks. In first case, both cracks are perpendicular to axis. In second case, both cracks are inclined to vertical plane and also inclined with each other. Finite element method (FEM) is performed using ANSYSTM software which is theoretical basis. Experimentation is performed using Fast Fourier Transform (FFT) analyzer on simply supported stepped rotor shaft and cantilever circular beam with two cracks each. Findings – The results of FEM and experimentation are validated and are in good agreement. The error in crack detection by FEM is in the range of 3-15 percent while 5-20 percent by experimentation. The database obtained by modal analysis is used to train the network of ANN which predicts crack characteristics. Validity of method is investigated by comparing the predictions of ANN with FEM and experimentation. The results are in good agreement with error of 7-16 percent between ANN and FEM while 9-21 percent between ANN and experimental analysis. Originality/value – It envisages that the method is capable. It is an effective as well as an alternate method of fault detection in beam/rotating element to the existing methods.

Vibration Analysis of a Beam with Multiple Cracks

2012 ◽  
Vol 178-181 ◽  
pp. 2505-2508 ◽  
Author(s):  
Chang Li Xiao ◽  
Ling Ling Xu
Keyword(s):  
Stiffness Matrix ◽  
Strain Energy ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Multiple Cracks ◽  
Transverse Cracks ◽  
Cracked Beam ◽  
Strain Energy Density Function ◽  
Natural Frequency Analysis ◽  
Good Agreement

A new method for the natural frequency analysis of a beam with multiple transverse cracks has been carried out. The method is called reverse modal analysis in this paper. The strain energy density function is used to evaluate the additional flexibility produced due to the presence of crack. Based on the flexibility, a new stiffness matrix is deduced and subsequently that is used to calculate the natural frequencies and mode shapes of the cracked beam. It has been established that the crack depths and their positions have an important effect on its dynamic behavior. The analysis of the crack structure is done using finite element and experimental analysis. The results from numerical analysis are compared with the results from the experimental method for validation. The results are found to be in good agreement.

Natural Frequency Analysis in the Workspace of a Six-Axis Industrial Robot Using Design of Experiments

2016 ◽  
Vol 1140 ◽  
pp. 345-352 ◽  
Author(s):  
Paul Glogowski ◽  
Michael Rieger ◽  
Jia Bin Sun ◽  
Bernd Kuhlenkötter
Keyword(s):  
Mathematical Model ◽  
Design Of Experiments ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Frequency Analysis ◽  
Natural Frequencies ◽  
Industrial Robot ◽  
Joint Configuration ◽  
Chatter Vibrations ◽  
Natural Frequency Analysis

This paper deals with a natural frequency distribution of a six-axis industrial robot in order to analyze chatter vibrations in upcoming milling processes. Since the dynamic vibration behavior of the robotic system can be manipulated by changing the robot’s joint configuration, experimental modal analysis is performed to determine the natural frequencies in the entire workspace. In this study, methods of design of experiments are used to derivate a mathematical model that predicts the natural frequencies of the robotic structure for any joint configuration within the considered workspace.

Natural Frequencies of Stator in Induction Motors

1997 ◽  
Author(s):  
Isao Suzuki ◽  
Shinichi Noda ◽  
Kazunobu Itomi ◽  
Fuminori Ishibashi
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Induction Motors ◽  
Fem Analysis ◽  
Stator Core ◽  
Second Stage ◽  
Contact Surfaces ◽  
Natural Frequency Analysis ◽  
Spring Constants ◽  
Good Agreement

Abstract Totally enclosed induction motors in which the stator core is pressed in the frame are in general used in industrial machines and manufactured with similar construction around the world. These motors produce a strong electromagnetic noise, which is caused by resonance between the natural frequencies of the stator core and the harmonics of electromagnetic forces. Therefore, it is very important to estimate its natural frequencies at the stage of design. As the first stage of research to estimate the natural frequencies of the stator core pressed into the motor frame, the dual rings were chosen as the object of studies. They are similar to the motor in construction and are easy to use to solve the problems. The purpose of this study is to investigate the effects of the tight fit to the natural frequencies and to find an analytical method by FEM. The authors have found that the introduction of spring elements with radial and circumferential spring constants at the contact surfaces provides accurate calculated results of the natural frequency by FEM. This paper describes about the spring constants obtained from experiments and analysis. As a result, when the spring constants in the radial direction are infinite and those in the circumferential direction are variable, it is clear that the spring constants for natural frequency analysis by FEM were expressed as a function of contact pressure on the contact surfaces. In the second stage, the measurement and calculation of natural frequency in the actual stator core with a frame was performed, and these results showed good agreement. These spring constants will be useful in FEM analysis of stator cores pressed into cylindrical induction motor frames.

scholarly journals Natural Frequency for a Composite Structure Made with a Combination of Metal and Laminated Composites

2020 ◽  
Vol 8 (6) ◽  
pp. 2340-2344
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Composite Structure ◽  
Laminated Composite ◽  
High Strength ◽  
Element Analysis ◽  
Volume Percentage ◽  
Steam Turbine Blade ◽  
Laminated Composite Beam ◽  
Natural Frequency Analysis

The need for low weight and high strength of the component is in high demand in various aerospace and defense industries and in line with this utilization of the combination of metal and composite increases. In this work, the natural frequency analysis of the structure, is carried out which is a combination of metal and composite. The natural frequency of the system is directly proportional to the stiffness of the system i.e. high natural frequency reflects high stiffness of materials. The structure considered like a cantilever beam, initially considering Titanium alloy the finite element analysis to get natural frequency carried out and validated using an analytical method. Then modal analysis performed using FEA for laminated composite structure and validate with the experimental results and received good agreement. The laminated composite beam manufactured using a hand layup method. Lastly, the structure modeled as a combination of laminated composite material & metal and FEA modal analysis done. The various volume percentage of composite and metal is studied and the best one finds out. The structure considered related to the last stage of the steam turbine blade.

scholarly journals Adaptive finite element analysis for damage detection of non-uniform Euler–Bernoulli beams with multiple cracks based on natural frequencies

2018 ◽  
Vol 35 (3) ◽  
pp. 1203-1229 ◽  
Author(s):  
Yongliang Wang ◽  
Yang Ju ◽  
Zhuo Zhuang ◽  
Chenfeng Li
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Damage Detection ◽  
Crack Detection ◽  
Iteration Process ◽  
Adaptive Finite Element Method ◽  
Multiple Cracks ◽  
Adaptive Finite Element ◽  
Content Type ◽  
Vibration Problems

Purpose This study aims to develop an adaptive finite element method for structural eigenproblems of cracked Euler–Bernoulli beams via the superconvergent patch recovery displacement technique. This research comprises the numerical algorithm and experimental results for free vibration problems (forward eigenproblems) and damage detection problems (inverse eigenproblems). Design/methodology/approach The weakened properties analogy is used to describe cracks in this model. The adaptive strategy proposed in this paper provides accurate, efficient and reliable eigensolutions of frequency and mode (i.e. eigenpairs as eigenvalue and eigenfunction) for Euler–Bernoulli beams with multiple cracks. Based on the frequency measurement method for damage detection, using the difference between the actual and computed frequencies of cracked beams, the inverse eigenproblems are solved iteratively for identifying the residuals of locations and sizes of the cracks by the Newton–Raphson iteration technique. In the crack detection, the estimated residuals are added to obtain reliable results, which is an iteration process that will be expedited by more accurate frequency solutions based on the proposed method for free vibration problems. Findings Numerical results are presented for free vibration problems and damage detection problems of representative non-uniform and geometrically stepped Euler–Bernoulli beams with multiple cracks to demonstrate the effectiveness, efficiency, accuracy and reliability of the proposed method. Originality/value The proposed combination of methodologies described in the paper leads to a very powerful approach for free vibration and damage detection of beams with cracks, introducing the mesh refinement, that can be extended to deal with the damage detection of frame structures.

The use of intraarterial papaverine in the management of vasospasm complicating arteriovenous malformation resection

1995 ◽  
Vol 82 (2) ◽  
pp. 296-299 ◽  
Author(s):  
Michael K. Morgan ◽  
Maurice J. Day ◽  
Nicholas Little ◽  
Verity Grinnell ◽  
William Sorby
Keyword(s):  
Arteriovenous Malformation ◽  
Perfusion Pressure ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Venous Occlusion ◽  
Neurological Deterioration ◽  
Unusual Complication ◽  
Content Type ◽  
First Case ◽  
Normal Perfusion Pressure Breakthrough ◽  
Fine Print

✓ The authors report two cases of treatment by intraarterial papaverine of cerebral vasospasm complicating the resection of an arteriovenous malformation (AVM). Both cases had successful reversal of vasospasm documented on angiography. In the first case sustained neurological improvement occurred, resulting in a normal outcome by the time of discharge. In the second case, neurological deterioration occurred with the development of cerebral edema. This complication was thought to be due to normal perfusion pressure breakthrough, on the basis of angiographic arterial vasodilation and increased cerebral blood flow. These two cases illustrate an unusual complication of surgery for AVMs and demonstrate that vasospasm (along with intracranial hemorrhage, venous occlusion, and normal perfusion pressure breakthrough) should be considered in the differential diagnosis of delayed neurological deterioration following resection of these lesions. Although intraarterial papaverine may be successful in dilating spastic arteries, it may also result in pathologically high flows following AVM resection. However, this complication has not been seen in our experience of treating aneurysmal subarachnoid hemorrhage by this technique.

Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

2018 ◽  
Vol 233 (3) ◽  
pp. 835-847 ◽  
Author(s):  
Mohammad-Reza Ashory ◽  
Farhad Talebi ◽  
Heydar R Ghadikolaei ◽  
Morad Karimpour
Keyword(s):  
Natural Frequency ◽  
Measurement Errors ◽  
Mode Shapes ◽  
Model Parameters ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Tracking Method ◽  
Strong Resemblance ◽  
Test Scenarios ◽  
Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

scholarly journals First Case of Human Cerebral Taenia martis Cysticercosis

2015 ◽  
Vol 53 (8) ◽  
pp. 2756-2759 ◽  
Author(s):  
Julie Brunet ◽  
Aurélien Benoilid ◽  
Stéphane Kremer ◽  
Constanza Dalvit ◽  
Nicolas Lefebvre ◽  
...  
Keyword(s):  
Larval Stage ◽  
Immunocompetent Patient ◽  
Intermediate Hosts ◽  
Biopsy Material ◽  
Content Type ◽  
Dna Analyses ◽  
First Case

Taenia martis is a tapeworm affecting mustelids, with rodents serving as intermediate hosts. The larval stage (cysticercus) has been found before only rarely in humans or primates. We hereby describe a case of cerebral T. martis cysticercosis in a French immunocompetent patient, confirmed by DNA analyses of biopsy material.

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