scholarly journals A Novel Method for Crack Detection in Steel Cantilever Beam Using Wavelet Analysis by Combination Mode Shapes

2018 ◽  
Vol 10 (4) ◽  
pp. 1-12 ◽  
Author(s):  
H. Rouhollah Pour ◽  
◽  
J. Asgari Marnani ◽  
A. A. Tabatabei
Keyword(s):  
Wavelet Analysis ◽  
Cantilever Beam ◽  
Crack Detection ◽  
Mode Shapes ◽  
Novel Method ◽  
Combination Mode

Analysis of the Dynamic Response of a Cracked Beam Structure

2012 ◽  
Vol 187 ◽  
pp. 58-62 ◽  
Author(s):  
D. N. Thatoi ◽  
J. Nanda ◽  
H.C. Das ◽  
D.R. Parhi
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Cantilever Beam ◽  
Crack Detection ◽  
Dynamic Behaviour ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Cracked Beam ◽  
Local Flexibility ◽  
Good Agreement

In this research, dynamic behaviour of a cracked cantilever beam has been analysed using finite element and experimental analysis. Deviations in mode shapes and natural frequencies have been noticed due to the presence of crack in the beam. The variation in the dynamic response is due to change in local flexibility because of the presence of crack in the beam. Finite element and experimental analyses have been carried out to find out the vibration indices of the cracked cantilever beam for validating the robustness of the theoretical model used for crack detection. The numerical results obtained through FEA are in good agreement with experimental results.

Free vibration analysis of a cantilever beam with a slant edge crack

2016 ◽  
Vol 231 (5) ◽  
pp. 823-843 ◽  
Author(s):  
J Liu ◽  
YM Shao ◽  
WD Zhu
Keyword(s):  
Cantilever Beam ◽  
Edge Crack ◽  
Crack Detection ◽  
Failure Modes ◽  
Free Vibration Analysis ◽  
Mode Shapes ◽  
Beam Model ◽  
Equivalent Stiffness ◽  
Proposed Model ◽  
Detection And Diagnosis

As one of major failure modes of mechanical structures subjected to periodic loads, edge cracks due to fatigue can cause catastrophic failures in such structures. Understanding vibration characteristics of a structure with an edge crack is useful for early crack detection and diagnosis. In this work, a new cracked cantilever beam model is presented to study the vibration of a cantilever beam with a slant edge crack, which cannot be modeled by previous methods considering a uniform edge crack along the width of the beam in the literature. An equivalent stiffness model is proposed by dividing the beam into numerous uniform independent thin pieces along its width. The beam is assumed to be an Euler–Bernoulli beam. The crack is assumed to be distributed along the width of the beam as a straight line and a parabola. The methodology proposed in this work can also be extended to model a crack with an arbitrary curve. Effects of crack depths on the nondimensional equivalent stiffness at the crack section of the cracked cantilever beam are studied. The first three nature frequencies and mode shapes of the cracked cantilever beam are obtained using compatibility conditions at crack tips and the transfer matrix method. Effects of depths and the location of the crack on the first three natural frequencies and mode shapes of the cracked cantilever beam are studied using the proposed cracked cantilever beam model. Numerical results from the proposed model are compared with those from the finite element method and an experimental investigation in the literature, which can validate the proposed model.

Deep Learning based Thermal Crack Detection on Structural Concrete Exposed to Elevated Temperature

2021 ◽  
pp. 136943322098663
Author(s):  
Diana Andrushia A ◽  
Anand N ◽  
Eva Lubloy ◽  
Prince Arulraj G
Keyword(s):  
Deep Learning ◽  
Crack Detection ◽  
Detection Method ◽  
Concrete Structures ◽  
Vital Role ◽  
Subjective Knowledge ◽  
Thermal Cracks ◽  
Reinforced Cement ◽  
Novel Method ◽  
Human Inspection

Health monitoring of concrete including, detecting defects such as cracking, spalling on fire affected concrete structures plays a vital role in the maintenance of reinforced cement concrete structures. However, this process mostly uses human inspection and relies on subjective knowledge of the inspectors. To overcome this limitation, a deep learning based automatic crack detection method is proposed. Deep learning is a vibrant strategy under computer vision field. The proposed method consists of U-Net architecture with an encoder and decoder framework. It performs pixel wise classification to detect the thermal cracks accurately. Binary Cross Entropy (BCA) based loss function is selected as the evaluation function. Trained U-Net is capable of detecting major thermal cracks and minor thermal cracks under various heating durations. The proposed, U-Net crack detection is a novel method which can be used to detect the thermal cracks developed on fire exposed concrete structures. The proposed method is compared with the other state-of-the-art methods and found to be accurate with 78.12% Intersection over Union (IoU).

An Approach to Approximate the Full Strain Field of Turbofan Blades During Operation

2018 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu ◽  
Walter O’Brien
Keyword(s):  
Numerical Model ◽  
Cantilever Beam ◽  
Strain Field ◽  
Measured Data ◽  
Mode Shapes ◽  
Beam Model ◽  
Reference Solution ◽  
Full Field ◽  
Field Response ◽  
Critical Locations

The measurement of the aeromechanical response of the fan blades is important to quantifying their integrity. The accurate knowledge of the response at critical locations of the structure is crucial when assessing the structural condition. A reliable and low cost measuring technique is necessary. Currently, sensors can only provide the measured data at several discrete points. A significant number of sensors may be required to fully characterize the aeromechanical response of the blades. However, the amount of instrumentation that can be placed on the structure is limited due to data acquisition system limitations, instrumentation accessibility, and the effect of the instrumentation on the measured response. From a practical stand point, it is not possible to place sensors at all the critical locations for different excitations. Therefore, development of an approach that derives the full strain field response based on a limited set of measured data is required. In this study, the traditional model reduction method is used to expand the full strain field response of the structure by using a set of discrete measured data. Two computational models are developed and used to verify the expansion approach. The solution of the numerical model is chosen as the reference solution. In addition, the numerical model also provides the mode shapes of the structure. In the expansion approach, this information is used to develop the algorithm. First, a cantilever beam model is created. The influences of the sensor location, number of sensors and the number of modes included are analyzed using this cantilever beam model. The expanded full field response data is compared with the reference solution to evaluate the expansion procedure. The rotor 67 blade model is then used to test the expansion method. The results show that the expanded full field data is in good agreement with the calculated data. The expansion algorithm can be used for the full field strain by using the limited sets of strain data.

Reliable Mode Shape Expansion Method for Error Localisation and Model Updating

1997 ◽  
Author(s):  
Philippe Collignon ◽  
Jean-Claude Golinval
Keyword(s):  
Cantilever Beam ◽  
Mode Shape ◽  
Constitutive Equations ◽  
Structural Model ◽  
Model Updating ◽  
Failure Detection ◽  
Expansion Method ◽  
Relative Performance ◽  
Mode Shapes ◽  
Error Localization

Abstract Failure detection and model updating using structural model are based on the comparison of an appropriate indicator of the discrepancy between experimental and analytical results. The reliability of the expansion of measured mode shapes is very important for the process of error localization and model updating. Two mode shape expansion techniques are examined in this paper : the well known dynamic expansion (DE) method and a method based on the minimisation of errors on constitutive equations (MECE). A new expansion method based on some improvements of the previous techniques is proposed to obtain results that are more reliable for error localisation and for model updating. The relative performance of the different expansion methods is demonstrated on the example of a cantilever beam.

Derivatives and Parameter Designs of Arbitrary Cross-Section Inhomogenous Beams’ Modes

2013 ◽  
Author(s):  
J. W. Xing ◽  
G. T. Zheng
Keyword(s):  
Cantilever Beam ◽  
Cross Section ◽  
Analytical Solutions ◽  
Structural Parameters ◽  
Arbitrary Cross Section ◽  
Mode Shapes ◽  
Design Parameters ◽  
Structural Parameter ◽  
Highly Sensitive ◽  
Sensitivity Analysis Method

As highly sensitive to structural parameter variations, it is necessary to study relations between derivatives of displacement modes and structural design parameters. This paper proposes an integral technique for obtaining the analytical solutions of slope and curvature modes of arbitrary cross-section inhomogeneous cantilever beam. The method is validated by comparing the computation results of modal frequencies and shapes with both numerical and analytical solutions. Furthermore, based on the presented method, we have established explicit expressions for the structural parameters sensitivity of the slope/curvature mode shapes. An example of parameter design is also presented for a cantilever beam with the proposed sensitivity analysis method.

Two degree of freedom vibration based electromagnetic energy harvester for bridge health monitoring system

2020 ◽  
pp. 1045389X2095945
Author(s):  
Muhammad Masood Ahmad ◽  
Farid Ullah Khan
Keyword(s):  
Cantilever Beam ◽  
Energy Harvester ◽  
Low Frequency ◽  
Open Circuit ◽  
Electromagnetic Energy ◽  
Degree Of Freedom ◽  
Mode Shapes ◽  
Fixed End ◽  
Two Degree Of Freedom ◽  
Maximum Voltage

This paper presents an electromagnetic energy harvester to extract low frequency and low acceleration vibration energy available in a bridge environment. The developed harvester is a multi-mode oscillator with dual electromagnetic transduction mechanisms. The harvester consists of two cantilever beams. The first cantilever beam is split into two equal pieces along its length and the second beam placed in between them coming back to the fixed end and attached at outer end to the first beam. This way instead of a long conventional cantilever beam a compact harvester is fabricated. Two magnets as proof masses are attached to each free end of the beam making it a two degree of freedom system (2-DOF). The magnets are positioned to oscillate inside hand wound coils during operation. An analytical model was developed and COMSOL multiphysics was used to simulate the mode shapes of the harvester. The mathematical model was simulated for open circuit voltage in MATLAB and showed closely matching results with the experimental values. The harvester is characterized in lab for its performance under sinusoidal vibrations at low frequency (3 Hz–15 Hz) and low acceleration (0.01–0.09 g) levels. The 2-DOF harvester has two resonant frequencies of 4.4 Hz and 5.5 Hz and a volume of 333 cm3. It produces maximum voltage of 0.6 V at first resonance on coil-1 and maximum voltage of 1.2 V on coil-2 at second resonance at 0.09 g. At acceleration of 0.09 g the harvester produced 2.51 mW at first resonant frequency and 10.7 mW at second resonance. Moreover, the AC output voltage of the harvester is rectified to DC voltage by a three-stage Cockcroft-Walton multiplier type circuit. The DC power output at 0.05 g was 0.939 mW at first resonance and 0.956 mW at second resonance while maximum voltages of 5.4 V on coil-1 and 4 V on coil-2 were produced.

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