scholarly journals Restoration of Natural Frequency of Cracked Cantilever Beam Using CNT Composite Patch: A Finite Element Study

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Mahmoud Nadim Nahas ◽  
Mahmoud Ali Alzahrani
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Fe Simulation ◽  
Crack Depth ◽  
High Strength ◽  
Crack Location ◽  
Weight Concentration ◽  
Beam Depth ◽  
Initiation And Propagation ◽  
Low Stiffness

Cyclic loadings cause fatigue to the elements of machines leading to crack initiation and propagation. This phenomenon decreases the age of the elements. In particular, cracks decrease the stiffness of the parts and lower the parts natural frequency, leading to failure under normal working conditions. This paper introduces a new application to carbon nanotube (CNT) composites in the repairing process of a cracked specimen to restore the natural frequency of the specimen. Commonly, patches are made of high strength and high stiffness materials. This paper shows that even low stiffness materials, such as epoxy reinforced with CNT, can contribute to the repair of a cracked specimen. A 2D finite element (FE) simulation is used to study the effects of bonding CNT composite patches over the crack location to repair cracked metal specimens. The effects of the patch thickness, length, and CNTs weight concentration ratio are investigated. Results showed an increase in the natural frequency of 31% compared to the cracked specimen at a crack depth of 70% of the beam depth and at a distance of 20% of the total beam length from the support.

scholarly journals Influence of Crack on Modal Parameters of Cantilever Beam Using Experimental Modal Analysis

2018 ◽  
Vol 1 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Siva Sankara Babu Chinka ◽  
Balakrishna Adavi ◽  
Srinivasa Rao Putti
Keyword(s):  
Numerical Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Cantilever Beam ◽  
Damping Ratio ◽  
Crack Depth ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Crack Location

In this paper, the dynamic behavior of a cantilever beam without and with crack is observed. An elastic Aluminum cantilever beams having surface crack at various crack positions are considered to analyze dynamically. Crack depth, crack length and crack location are the foremost parameters for describing the health condition of beam in terms of modal parameters such as natural frequency, mode shape and damping ratio. It is crucial to study the influence of crack depth and crack location on modal parameters of the beam for the decent performance and its safety. Crack or damage of structure causes a reduction in stiffness, an intrinsic reduction in resonant frequencies, variation of damping ratios and mode shapes. The broad examination of cantilever beam without crack and with crack has been done using Numerical analysis (Ansys18.0) and experimental modal analysis. To observe the exact higher modes of beam, discretize the beam into small elements. An experimental set up was established for cantilever beam having crack and it was excited by an impact hammer and finally the response was obtained using PCB accelerometer with the help sound and vibration toolkit of NI Lab-view. After obtaining the Frequency response functions (FRFs), the natural frequencies of beam are estimated using peak search method. The effectiveness of experimental modal analysis in terms of natural frequency is validated with numerical analysis results. This paper contains the study of free vibration analysis under the influence of crack at different points along the length of the beam.

The effect of crack geometry on non-destructive fault detection of EN 8 and EN 47 cracked cantilever beam

2019 ◽  
Vol 50 (3) ◽  
pp. 92-100 ◽  
Author(s):  
V Khalkar ◽  
S Ramachandran
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Cantilever Beam ◽  
Crack Detection ◽  
Crack Depth ◽  
Free Vibration Analysis ◽  
Crack Location ◽  
Crack Geometry ◽  
Shaped Crack ◽  
Non Destructive

Since long it has been observed that the size of the crack in structures increases with time, and finally, it may lead to its catastrophic failure. Hence, it is crucial to do the vibration study of cracked structures with regard to vibration-based crack detection and the classification of cracks. So far, vibration-based non-destructive testing method is applied to many spring steel cracked cantilever beams for its possible crack detection. However, the effect of various kinds of practical cracks, that is, V-shaped and U-shaped, on the applicability of these methods has been overlooked. To investigate this issue, artificially cracks are made on the cantilever beam. By free vibration analysis, the effect of crack geometry, crack depth, and crack location on natural frequency is investigated. The natural frequency results obtained from V-shaped and U-shaped models for the same crack configurations are compared with each other and it is revealed that the results are not much sensitive for the change of crack geometry. Hence, it is clear that free vibration-based crack detection method approximately predicts the crack parameters, that is, crack location and crack depth, in structures irrespective of the crack geometry. It is also found that for the same configuration, results of natural frequency are comparatively on the lower side for U-shaped crack models than V-shaped crack models. In this study, the natural frequency of each cracked case is computed by a theoretical method and numerical method and shows good agreement. Finally, it is also observed that structural integrity of a cracked cantilever beam is a function of crack location.

Dynamic Response of Tubular T-Joints Under the Influence of Propagating Cracks

1996 ◽  
Vol 118 (1) ◽  
pp. 71-78 ◽  
Author(s):  
D. I. Nwosu ◽  
A. S. J. Swamidas ◽  
J. Y. Guigne´
Keyword(s):  
Natural Frequency ◽  
Crack Detection ◽  
Crack Depth ◽  
Bending Moment ◽  
Frequency Change ◽  
T Joints ◽  
Finite Element Program ◽  
Crack Location ◽  
Percent Change ◽  
Frequency Changes

This paper presents an analytical study on the vibration response of tubular T-joints for detecting the existence of cracks along their intersections. The ABAQUS finite element program was utilized for carrying out the analysis. Frequency response functions were obtained for a joint with and without cracks. The joint was modeled with 8-node degenerate shell elements having 5 degrees of freedom per node. Line spring elements were used to model the crack. The exact crack configuration (semielliptical shape, Fig. 5(b)), as observed from numerous experimental fatigue crack investigations at the critical location, has been achieved through a mapping function, that allows a crack in a planar element to be mapped on to the tube surface. The natural frequency changes with respect to crack depth show little changes, being 4.82 percent for a 83-percent crack depth for the first mode. On the other hand, significant changes have been observed for bending moment and curvature as a function of crack depth. For an 83-percent chord thickness crack, a 97-percent change in bending moment at points around the crack vicinity, and 34.15 to 78 percent change in bending moments, for those locations far away from the crack location, have been observed. Natural frequency change should be combined with other modal parameters such as “bending moment (or bending strain)” and “curvature” changes for crack detection. The presence of the crack can be detected at locations far away from the crack location using such sensors as strain gages.

scholarly journals Fault Diagnosis of Beam-Like Structure Using Modified Fuzzy Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Dhirendranath Thatoi ◽  
Sasanka Choudhury ◽  
Prabir Kumar Jena Jena
Keyword(s):  
Finite Element ◽  
Fuzzy Logic ◽  
Fuzzy Controller ◽  
Crack Depth ◽  
Research Work ◽  
Mode Shapes ◽  
Engineering Structures ◽  
Element Analysis ◽  
Crack Location ◽  
Vibration Signatures

This paper presents a novel hybrid fuzzy logic based artificial intelligence (AI) technique applicable to diagnosis of the crack parameters in a fixed-fixed beam by using the vibration signatures as input. The presence of damage in engineering structures leads to changes in vibration signatures like natural frequency and mode shapes. In the first part of this work, a structure with a failure crack has been analyzed using finite element method (FEM) and retrospective changes in the vibration signatures have been recorded. In the second part of the research work, these deviations in the vibration signatures for the first three mode shapes have been taken as input parameters for a fuzzy logic based controller for calculation of crack location and its severity as output parameters. In the proposed fuzzy controller, hybrid membership functions have been taken. Several fuzzy rules have been identified for prediction of crack depth and location and the results have been compared with finite element analysis. A database of experimental results has also been considered to check the robustness of the fuzzy controller. The results show that predictions for the nondimensional crack location, α, deviate ~2.4% from experimental values and for the nondimensional crack depth, δ, are less than ~−2%.

Study on Natural Vibration Characteristics of Large Scale Composite Wind Turbine Blades

2011 ◽  
Author(s):  
Yi Yang ◽  
Chengcheng Tan ◽  
Danmei Xie ◽  
Yangheng Xiong ◽  
Yang Shi ◽  
...  
Keyword(s):  
Finite Element ◽  
Wind Turbine ◽  
Modal Analysis ◽  
Turbine Blade ◽  
Torsional Vibration ◽  
Crack Depth ◽  
Wind Turbine Blade ◽  
Variable Cross ◽  
Crack Location ◽  
The Impact

As the single unit capacity has been increased, the length of wind turbine blade is becoming longer, and the blade vibration fatigue damage caused by impact of wind turbines has become an important issue of wind turbine security. Therefore, modal analysis and study on the impact of crack on the natural frequency of the wind turbine blade are of great significance. The finite element software ANSYS was used to establish a finite element model of a 1.5MW composite wind turbine blade, with a structure of twisted variable cross-section and hollow core in the first place of this paper. Modal analysis of the model established in this paper showed that the blade vibrates in 3 different forms, they are flap within the rotating plane, flutter vibration perpendicularity to the rotating plane and torsional vibration around the blade shaft. Among all the orders, flap and flutter vibration are predominent in low modes, while torsional vibration appears only in high modes (above the fifth order). Then blade models with cracks in the root were established to analyze the regularity of the blade natural frequencies with the crack location, depth and the variation of the angle. The results showed that: as the location of the crack changed in wingspan direction, the change of frequencies showed two basic trends: one was declining gradually; the other was decreasing and then increasing before decreasing again, and the minimum the maximum value appeared at location around 32.5% and 87.5% of the blade root respectively. As crack depth increased gradually, the frequencies reduced continuously, and compared to crack location, influence of crack depth was more prominent. For slant crack, when the crack angle, that is the angle between the crack section chord line and the foliosine plane, increased, all orders of frequencies gradually increased, indicating that the influence of the crack on the blade stiffness decreases as the angle increases.

Effect of Cracks on the Natural Frequency of Cylindrical Shell Structures

2020 ◽  
Vol 38 (12A) ◽  
pp. 1808-1817
Author(s):  
Marwah A. Husain ◽  
Mohsin A. Al-shammari
Keyword(s):  
Cylindrical Shell ◽  
Natural Frequency ◽  
Close Agreement ◽  
Crack Depth ◽  
Free Vibration Analysis ◽  
Shell Structures ◽  
Structural Safety ◽  
Crack Orientation ◽  
Simply Supported ◽  
Crack Location

Shell structures are liable to different kinds of defects and damage like cracking and corrosion which may destroy their structural safety and affect the service life. The cracks' effects are significant considerations in the design of cylindrical shell structures as they influence the vibration characteristics and safety. This present work is an experimental study on the free vibration analysis of a cylindrical shell involving circumferential surface crack. The influence of the ratio of shell’s radius to a shell’s thickness (R/h)of the shell structure, crack length in the shell, crack depth in the shell, crack location of the shell, and crack orientation in the shell are investigated under a clamped - clamped and simply supported boundary conditions at each end in the shell. Results showed that the minimum impact of the crack is at the angle of crack 75, and the circumferential fissure has more effect than a longitudinal fissure, In addition to this, under SS-SS, C-C the natural frequency will decrease if the fissure is located in the middle of the shell is greater than other locations. but when crack animated across in the ends of the limits the decrease in the natural frequency under C-C only. Results were compared with the literature there was a close agreement.

Influence of Centrifugal Force on Characteristics of Turbine Shaft for Micro-Spindle for Micro-Cutting

2012 ◽  
Vol 565 ◽  
pp. 582-587
Author(s):  
Wei Li ◽  
Zhi Xiong Zhou ◽  
Xiang Ming Huang ◽  
Chen Chen ◽  
Ling Yun Meng
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Centrifugal Force ◽  
Torsional Vibration ◽  
Rotational Speed ◽  
Fe Simulation ◽  
Great Influence ◽  
Vibrational Modes ◽  
Micro Cutting ◽  
Turbine Shaft

The centrifugal force has great influence on characteristics of the turbine shaft. The changes of stress, diameter and natural frequency of the turbine shaft for self-developed micro-spindle for micro-cutting following with the rotational speed were studied by finite element (FE) simulation, which showed that stress, diameter of the turbine shaft and frequency of torsional vibration in elastic shaft coupling integrated with the turbine shaft caused by the centrifugal force increases almost linearly with increase of rotational speed and the higher the speed, the larger the increase. The frequencies of other vibrational modes were influenced by centrifugal force. Materials with good properties can improve characteristics of turbine shaft caused by the centrifugal force well.

scholarly journals Finite Element Simulation of Forming Process for Automotive Components from Advanced High Strength Steel

2019 ◽  
Vol 257 ◽  
pp. 02010
Author(s):  
Yachita Peraprutchaya ◽  
Surasak Suranantchai
Keyword(s):  
Finite Element ◽  
Fe Simulation ◽  
Elastic Recovery ◽  
Kinematic Hardening ◽  
High Strength ◽  
Tensile Tests ◽  
Forming Process ◽  
Fe Method ◽  
Automotive Components ◽  
The One

Advance high strength (AHS) steel has been widely used in the automotive industry and order to reduce the weight of automotive components that effect to reduce fuel consumption, but vehicles maintain safety. However, forming process with AHS steel has many problems which the main defect was spring-back. Therefore, the usage of finite element (FE) method simulation with kinematic hardening materials model sustains and improve production processes. Yoshida-Uemori (Y-U) model is the one of kinematic hardening materials model that show the great capability for prediction of elastic recovery behavior. Consequencely, this work has been research on AHS steel as the NSC980D grade for automotive components in the drawing process and applied FE simulation with Y-U model to improve the production process. Moreover, NSC980D steel was inspected in tension-compression and tensile tests were proceeded. As a result, material parameters from testing simulate with designed die and improvement were shown. Finally, comparing FE simulation forming with experiment forming, showed FE simulation with Y-U model is suitable for prediction and process improvement.

Response of Cracked Cantilever Beam Subjected to Traversing Mass

2015 ◽  
Author(s):  
Shakti P. Jena ◽  
Dayal R. Parhi ◽  
Devasis Mishra
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Response ◽  
Numerical Method ◽  
Cantilever Beam ◽  
Crack Depth ◽  
Numerical Procedure ◽  
Element Analysis ◽  
Crack Location

The present work emphasizes the dynamic response of double cracked cantilever beam subjected to a traversing mass. The cracks are located at different positions of the beam with random crack depths. The response of the damaged structure has been evaluated employing a numerical procedure of Runge-Kuuta method. The effects of crack depth, traversing mass, traversing speed and crack location on the response of the structure are studied. Finite element analysis (FEA) using the commercial ANSYS 15 has been presented to validate the adopted numerical method.

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