scholarly journals ANALYSIS AND PREDICTION OF MULTIPLE-CRACKED PLASTIC BEAM

2009 ◽  
Vol 12 (18) ◽  
pp. 37-45
Author(s):  
Hang Xuan Le ◽  
Luong Thi Hien Nguyen
Keyword(s):  
Genetic Algorithm ◽  
Cantilever Beam ◽  
Stiffness Matrix ◽  
Natural Frequencies ◽  
Fitness Function ◽  
High Accuracy ◽  
Crack Identification ◽  
Element Stiffness Matrix ◽  
Crack Location ◽  
Local Flexibility

This paper presents a method for identification of location and depth of a crack in a cantilever beam by means of a genetic algorithm based on the signs of crack identification are beams natural frequencies. The cracked element stiffness matrix is based on the theory that local flexibility goes up because of the appearance of cracks. Crack location and depth is identified by minimizing fitness function, which performs difference between natural frequencies calculated and measured. Results show that this method helps to make prediction with high accuracy and converging speed.

scholarly journals Influence of edge crack on frequencies of thin plate in bending

2005 ◽  
Vol 27 (2) ◽  
pp. 107-117
Author(s):  
Nguyen Thi Hien Luong ◽  
Vuong Quang Giang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thin Plate ◽  
Edge Crack ◽  
Natural Frequencies ◽  
High Accuracy ◽  
Crack Identification ◽  
The Finite Element Method ◽  
Isoparametric Element ◽  
Crack Location

This paper investigates the influence of crack location and crack length on changes in natural frequencies of bending thin plate. To perform this analysis, a computing program called CRACK-PLATE, using the finite element method based on the Ressner-Mindlin' theory of plate is developed. In order to achieve a high accuracy, an isoparametric element of Barsoum is combined with an 8-node quadrilateral isoparametric element. The numerical results show that the natural frequencies are very sensitive to the crack presence in the bending thin plate. This study is a basis for crack identification based on natural frequencies of plates.

Nondestructive Detection of a Crack in a Triangular Cantilever Beam Based on Frequency Measurement

2007 ◽  
Vol 353-358 ◽  
pp. 2285-2288
Author(s):  
Fei Wang ◽  
Xue Zeng Zhao
Keyword(s):  
Cantilever Beam ◽  
Natural Frequencies ◽  
Frequency Measurement ◽  
Crack Size ◽  
Force Sensors ◽  
Rotational Spring ◽  
Cantilever Deflection ◽  
Crack Location ◽  
Small Force ◽  
Point Of Intersection

Triangular cantilevers are usually used as small force sensors in the transverse direction. Analyzing the effect of a crack on transverse vibration of a triangular cantilever will be of value to users and designers of cantilever deflection force sensors. We present a method for prediction of location and size of a crack in a triangular cantilever beam based on measurement of the natural frequencies in this paper. The crack is modeled as a rotational spring. The beam is treated as two triangular beams connected by a rotational spring at the crack location. Formulae for representing the relation between natural frequencies and the crack details are presented. To detect crack details from experiment results, the plots of the crack stiffness versus its location for any three natural modes can be obtained through the relation equation, and the point of intersection of the three curves gives the crack location. The crack size is then calculated using the relation between its stiffness and size. An example to demonstrate the validity and accuracy of the method is presented.

Natural Vibrations of a Clamped-Clamped Arch With an Open Transverse Crack

1997 ◽  
Vol 119 (2) ◽  
pp. 145-151 ◽  
Author(s):  
M. Krawczuk ◽  
W. Ostachowicz
Keyword(s):  
Finite Element ◽  
Stiffness Matrix ◽  
Edge Crack ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Curved Beam ◽  
Natural Vibrations ◽  
Crack Location ◽  
Cracked Arch

The paper presents a finite element model of the arch with a transverse, one-edge crack. A part of the cracked arch is modelled by a curved beam finite element with the crack. Parts of the arch without the crack are modelled by noncracked curved beam finite elements. The crack occurring in the arch is nonpropagating and open. It is assumed that the crack changes only the stiffness of the arch, whereas the mass is unchanged. The method of the formation of the stiffness matrix of a curved beam finite element with the crack is presented. The effects of the crack location and its length on the changes of the in-plane natural frequencies and mode shapes of the clamped-clamped arch are studied.

Crack Identification in a Cantilever Beam Using Coupled Response Measurements

1998 ◽  
Vol 120 (4) ◽  
pp. 775-777 ◽  
Author(s):  
A. S. Sekhar ◽  
P. Balaji Prasad
Keyword(s):  
Cantilever Beam ◽  
Crack Detection ◽  
Rate Of Change ◽  
Crack Identification ◽  
Direct Response ◽  
Crack Location ◽  
Small Cracks ◽  
Axial Response ◽  
Coupled Response ◽  
System Characteristics

Identification of crack location and magnitude through measurement in changes in system characteristics, such as modal measurements, has been studied by various researchers. In the present work based on the new method proposed by Gounaris et al. (1996) for crack detection through coupled response measurements, experiments were carried out on a cracked cantilever beam for eigenfrequencies, bending, and axial response measurements. It has been observed that the rate of change of direct response (bending) is much less at small cracks, while that of the coupled response (axial) changes substantially, which allows for diagnoses of smaller cracks.

Frequency-based damage detection in cantilever beam using vision-based monitoring system with motion magnification technique

2018 ◽  
Vol 29 (20) ◽  
pp. 3923-3936 ◽  
Author(s):  
Andrew Jaeyong Choi ◽  
Jae-Hung Han
Keyword(s):  
Genetic Algorithm ◽  
Damage Detection ◽  
Monitoring System ◽  
Cantilever Beam ◽  
Structural Damage ◽  
Natural Frequencies ◽  
Solution Space ◽  
Mode Shapes ◽  
High Resolution Data ◽  
Motion Magnification

This article proposes a method for damage detection using vision-based monitoring with motion magnification technique. The methods based on the vibration characteristics of structures such as natural frequency, mode shapes, and modal damping have been applied to structural damage detection. However, the conventional methods have limitations for practical applications. Vision-based monitoring system can be employed as a new structural monitoring system because of its simplicity, potentially low cost, and unique capability of collecting high-resolution data. A methodology called video motion magnification has been developed to amplify non-visible small motions in a video to reveal the dynamic response. The video motion magnification method can be applied to measure small displacements to calculate the natural frequencies and the operational deflection shapes of the structures. Unlike conventional optimization methods, a genetic algorithm explores the entire solution space and can obtain the global optimum. In this article, identification of the location and magnitude of damage in a cantilever beam is formulated as an optimization problem using a real-value genetic algorithm by minimizing the objective function, which directly compares the first three natural frequencies changes from the phase-based motion magnification measurement and from the analytical model of a damaged cantilever beam.

scholarly journals Crack Identification in a Cantilever Beam Using Coupled Response Measurements

1997 ◽  
Author(s):  
A. S. Sekhar ◽  
P. Balaji Prasad
Keyword(s):  
Cantilever Beam ◽  
Crack Detection ◽  
Rate Of Change ◽  
Crack Identification ◽  
Direct Response ◽  
Crack Location ◽  
Small Cracks ◽  
Axial Response ◽  
Coupled Response ◽  
System Characteristics

Identification of crack location and magnitude through measurement in changes in system characteristics, such as modal measurements has been studied by various researchers. In the present work based on the new method proposed by Gounaris et al (1996) for crack detection through coupled response measurements, experiments were carried out on a cracked cantilever beam for eigenfrequencies, bending and axial response measurements. It has been observed that the rate of change of direct response (bending) is much less at small cracks while that of the coupled response (axial) changes, substantially allowing diagnoses of smaller cracks.

Detection of Cracks in Stationary Rotors via the Modal Frequency Changes Induced by a Roving Disc

2014 ◽  
Author(s):  
Z. N. Haji ◽  
S. O. Oyadiji
Keyword(s):  
Natural Frequencies ◽  
Crack Depth ◽  
Mode Shapes ◽  
Crack Identification ◽  
Open Crack ◽  
Suggested Approach ◽  
Rotor Systems ◽  
Crack Location ◽  
High Crack ◽  
Frequency Changes

In this study, a crack identification approach based on a finite element cracked model is presented to identify the location and depth ratios of a crack in rotor systems. A Bernoulli-Euler rotor carrying an auxiliary roving disc has been used to model the cracked rotor, in which the effect of a transverse open crack is modelled as a time-varying stiffness matrix. In order to predict the crack location in the rotor-disc-bearing system, the suggested approach utilises the variation of the normalized natural frequency curves versus the non-dimensional location of a roving disc which traverses along the rotor span. The merit of the suggested approach is to identify the location and sizes of a crack in a rotor by determining only the natural frequencies of the stationary rotor system. The first four natural frequencies are employed for the identification and localisation of a crack in the stationary rotor. Furthermore, this approach is not only efficient and practicable for high crack depth ratios but also for small crack depth ratios and for a crack close to or at the node of mode shapes, where natural frequencies are unaffected.

Natural Frequency Analysis of a Fixed-Fixed Cracked Plate in Bending

2005 ◽  
Author(s):  
Hien Luong Thi Nguyen ◽  
Quang Giang Vuong
Keyword(s):  
Inverse Problem ◽  
Dynamic Response ◽  
Frequency Analysis ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
High Accuracy ◽  
Crack Identification ◽  
Isoparametric Element ◽  
Central Crack ◽  
Natural Frequency Analysis

The paper aims to study the dynamic behavior of a bending thin plate with fixed-fixed ends after crack occurrence. Using the FEM with an 8-node quadrilateral isoparametric element based on the Ressner-Mindlin’ theory of plate, the program CRACK-PLATE is developed to investigate the effect of crack length and position on the dynamic response of plate. The natural frequencies and modes are calculated and analyzed numerically for the non-faulty case and additionally with the edge and the central crack. In order to achieve a high accuracy, a singularity element of Barsoum is combined. The numerical results show that the natural frequencies are very sensitive to the crack presence in bending plate. It provides a basis to carry out the inverse problem for crack identification based on the dynamic characteristics of plates.

Coupled Transverse and Axial Vibrations of Cracked Cantilever Beams With Roving Mass and Rotary Inertia

2010 ◽  
Author(s):  
Hurang Hu ◽  
Akindeji Ojetola ◽  
Hamid Hamidzadeh
Keyword(s):  
Cantilever Beam ◽  
Natural Frequencies ◽  
Coupling Effect ◽  
Rectangular Cross Section ◽  
Crack Depth ◽  
Rotary Inertia ◽  
Mode Shapes ◽  
Axial Deformation ◽  
Crack Location ◽  
Axial Vibrations

The vibration behavior of a cracked cantilever beam with a stationary roving mass and rotary inertia is investigated. The beam is modeled as an Euler-Bernoulli beam with rectangular cross section. The transverse deformation and axial deformation of the cracked beam are coupled through a stiffness matrix which is determined based on fracture mechanics principles. The analytical solutions are obtained for the natural frequencies and mode shapes of a cracked cantilever beam with a roving mass and rotary inertia. The effects of the location and depth of the crack, the location and the weight of the roving mass and rotary inertia on the natural frequencies and mode shapes of the beam are investigated. The numerical results show that the coupling between the transverse and axial vibrations for moderate values of crack depth and/or roving mass and rotary inertia is weak. Increasing the crack depth and the mass and rotary inertia will increase the coupling effect. Detection of the crack location using natural frequencies and mode shapes as parameters is also discussed.

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