Nonlinear Features in the Dynamic Response of a Cracked Beam Under Harmonic Forcing

2005 ◽  
Author(s):  
Ugo Andreaus ◽  
Paolo Casini ◽  
Fabrizio Vestroni
Keyword(s):  
Nonlinear Response ◽  
Damage Identification ◽  
Period Doubling ◽  
Element Model ◽  
Breathing Crack ◽  
Cracked Beam ◽  
Response Characteristics ◽  
Harmonic Forcing ◽  
Dimensional Finite Element ◽  
Nonlinear Features

Detection of damage in beam structures is usually pursued by means of methods based on the measured variations of modal quantities, like frequencies and eigenmodes. The drawback of these methods is the small sensitivity of modal quantities to concentrated damage. Since a crack introduces nonlinearities in the system, the use of nonlinear techniques of damage detection merits to be investigated. With this aim the present paper is devoted to analyze the peculiar features of the nonlinear response of a cracked beam. The problem of a cantilever beam with an asymmetric edge crack subjected to a harmonic forcing at the tip is considered as a plane problem and is solved by using two-dimensional finite element model; the behaviour of the breathing crack is simulated as a frictionless contact problem. The modification of the response with respect to the linear one is outlined: in particular, excitation of sub- and super-harmonics, period doubling, quasi-impulsive behaviour at crack interfaces are the main achievements. These response characteristics can be used in nonlinear techniques of damage identification.

Finite element analysis and experimental investigation of nonlinear features of rail fastening systems

2017 ◽  
Vol 232 (3) ◽  
pp. 873-894
Author(s):  
Y Liu ◽  
HP Yin ◽  
Y Luo ◽  
J Zhang
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Element Analysis ◽  
Rubber Material ◽  
Nonlinear Properties ◽  
Dimensional Finite Element ◽  
Nonlinear Features ◽  
Displacement Force ◽  
Three Dimensional Finite Element

The more demanding requirements for the reduction of vibration in passenger railways and urban railway lines have led to a trend towards lower-stiffness rail fastening systems accompanied by greater deformation of their rubber components. Nonlinearities under large deformation due to the boundary conditions, geometric properties, intrinsic hyperelasticity and viscidity of the rubber material, and dynamic nonlinear features such as the Payne effect have become prominent and cannot be ignored. In this research, a shear-type fastening system and a bonded compression-type rail fastening system have been designed and produced using the same rubber material. A set of mechanical experiments of the used rubber material was first performed to obtain the rubber properties; this information was later used as an input to a three-dimensional finite element model constructed using Abaqus. Laboratory tests of the two fastening specimens were then performed to obtain the quasi-static and dynamic displacement–force curves. Later, the three-dimensional finite element models were presented, and the calculated curves were compared to the measured values. Finally, the two fastening systems were comparatively analyzed, and the influences of their various nonlinear properties were discussed. The combined experimental and numerical analyses of the nonlinear properties of the two typical types of rail fastening systems are believed to enhance the understanding of their mechanical behavior and to improve the product design, structural optimization, and testing in practice.

Closed Crack Detection with Nonlinear Instantaneous Baseline

2013 ◽  
Vol 577-578 ◽  
pp. 633-636
Author(s):  
Wei Liang Wu ◽  
Wen Zhong Qu ◽  
Li Xiao
Keyword(s):  
Nonlinear Response ◽  
Crack Detection ◽  
Three Dimensional ◽  
Element Model ◽  
Closed Crack ◽  
Nonlinear Part ◽  
Nonlinear Springs ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Low Amplitude

Closed cracks, which stay in contact unless the excitation exceeds a certain threshold, exist as great menace to structures. Since nonlinear response is more sensitive to micro damage than conventional linear approaches, analyzing the nonlinear part of the collected response of structures to an input ultrasonic excitation is more promising in damage detection. In this paper, in order to image the location of a closed crack, an instantaneous baseline measurement is adopted and the nonlinear response is extracted by using scaling subtraction method. A three-dimensional finite element model of a plate with a closed crack is developed and the behavior of the closed crack is simulated with nonlinear springs at the crack interfaces. A network of actuators and sensors which constitutes of two arrays of surface-bonded piezoelectric transducers is built. The instantaneous baselines of each path are collected when the model is excited with low amplitude excitation. To diagnose the closed crack, a higher amplitude excitation over the threshold is applied to the model and the response signals of each path are recorded. The result shows that the differences caused by the crack can be observed from the scaling subtraction of these two recorded responses and the location of closed crack can be accurately imaged.

scholarly journals Nonlinear Vibration Analysis of a Beam with a Breathing Crack

2019 ◽  
Vol 9 (18) ◽  
pp. 3874 ◽  
Author(s):  
Hui Long ◽  
Yilun Liu ◽  
Kefu Liu
Keyword(s):  
Nonlinear Vibration ◽  
Structural Parameters ◽  
Multiple Scale ◽  
Element Model ◽  
Harmonic Excitation ◽  
Breathing Crack ◽  
Cracked Beam ◽  
Nonlinear Responses ◽  
Stiffness Model ◽  
Stiffness Variation

The phenomena of sub- and super-harmonic responses make up one of the prominent nonlinear characteristics of a beam with a breathing crack. In order to fully understand the behaviors of sub- and super-harmonic resonances, it is necessary to analyze the nonlinear vibration of a beam-like structure with a breathing crack. In this study, a new stiffness model that considers the influence of the partial crack closure is proposed to model the stiffness variation of the cracked beam. Based on the finite element model of a beam with a breathing crack, the multiple-scale method is proposed to analyze the nonlinear vibration of a cracked beam subjected to harmonic excitation, and the relation between the nonlinear vibration of the cracked beam and the system parameters is obtained. An experiment is conducted to validate the analytical results. The study shows that the nonlinear responses of a beam with a breathing crack are affected by both the structural parameters and the crack parameters.

Simply Supported Slab Bridge Damage Identification Based on Curvature Mode Method

2013 ◽  
Vol 351-352 ◽  
pp. 1657-1661
Author(s):  
Long Zhang
Keyword(s):  
Finite Element ◽  
Damage Identification ◽  
Three Dimensional ◽  
Element Model ◽  
Simply Supported ◽  
Mode Method ◽  
Dimensional Finite Element ◽  
Bridge Damage ◽  
Damage Condition ◽  
Three Dimensional Finite Element

This paper discusses the feasibility of damage identification on simply supported slab bridge by the curvature mode. Firstly, the theoretical basis of curvature modal method for damage identification is introduced. Then, it simulated the structural damages by the use of three-dimensional finite element model, and used curvature mode to identification them validly. Based on the finite element simulation results, the following conclusions can be drawn: the decline of the structural natural frequency can be used to judge if the simply supported slab bridge is damaged. But the declined value is small, it is almost impossible to achieve in the scene, and it also can not be accurately positioning and quantitative; curvature model is very sensitive to the partly change of structure. It cannot be affected by the interference of the other plates, when the damage condition was identified on one plate of the simply-supported slab bridge even if that plate is adjacent plate would not affect it.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

scholarly journals Internal Force on and Deformation of Steel Assembled Supporting Structure of Foundation Pit under Thermal Stress

2021 ◽  
Vol 11 (5) ◽  
pp. 2225
Author(s):  
Fu Wang ◽  
Guijun Shi ◽  
Wenbo Zhai ◽  
Bin Li ◽  
Chao Zhang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Bending Moment ◽  
High Strength ◽  
Element Model ◽  
Internal Force ◽  
Foundation Pit ◽  
Dimensional Finite Element ◽  
Influence Of Temperature On ◽  
Scale Experiment ◽  
Three Dimensional Finite Element

The steel assembled support structure of a foundation pit can be assembled easily with high strength and recycling value. Steel’s performance is significantly affected by the surrounding temperature due to its temperature sensitivity. Here, a full-scale experiment was conducted to study the influence of temperature on the internal force and deformation of supporting structures, and a three-dimensional finite element model was established for comparative analysis. The test results showed that under the temperature effect, the deformation of the central retaining pile was composed of rigid rotation and flexural deformation, while the adjacent pile of central retaining pile only experienced flexural deformation. The stress on the retaining pile crown changed little, while more stress accumulated at the bottom. Compared with the crown beam and waist beam 2, the stress on waist beam 1 was significantly affected by the temperature and increased by about 0.70 MPa/°C. Meanwhile, the stress of the rigid panel was greatly affected by the temperature, increasing 78% and 82% when the temperature increased by 15 °C on rigid panel 1 and rigid panel 2, respectively. The comparative simulation results indicated that the bending moment and shear strength of pile 1 were markedly affected by the temperature, but pile 2 and pile 3 were basically stable. Lastly, as the temperature varied, waist beam 2 had the largest change in the deflection, followed by waist beam 1; the crown beam experienced the smallest change in the deflection.

Numerical Analysis of Metro Station Construction by Large-Diameter Shield and Pile-Beam-Arch Method

2011 ◽  
Vol 368-373 ◽  
pp. 2711-2715 ◽  
Author(s):  
De Yun Ding ◽  
Xiu Ren Yang ◽  
Wei Dong Lu ◽  
Wei Ning Liu ◽  
Mei Yan ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Large Diameter ◽  
Element Model ◽  
Construction Method ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Shield Tunneling ◽  
Metro Station ◽  
Dimensional Finite Element ◽  
New Construction

In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

scholarly journals Development of a Novel Damage Detection Framework for Truss Railway Bridges Using Operational Acceleration and Strain Response

Vibration ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 422-445
Author(s):  
Md Riasat Azim ◽  
Mustafa Gül
Keyword(s):  
Damage Detection ◽  
Damage Identification ◽  
Numerical Study ◽  
Damage Index ◽  
Strain Analysis ◽  
Time History ◽  
Principal Component ◽  
Element Model ◽  
Railway Bridges ◽  
Truss Bridge

Railway bridges are an integral part of any railway communication network. As more and more railway bridges are showing signs of deterioration due to various natural and artificial causes, it is becoming increasingly imperative to develop effective health monitoring strategies specifically tailored to railway bridges. This paper presents a new damage detection framework for element level damage identification, for railway truss bridges, that combines the analysis of acceleration and strain responses. For this research, operational acceleration and strain time-history responses are obtained in response to the passage of trains. The acceleration response is analyzed through a sensor-clustering-based time-series analysis method and damage features are investigated in terms of structural nodes from the truss bridge. The strain data is analyzed through principal component analysis and provides information on damage from instrumented truss elements. A new damage index is developed by formulating a strategy to combine the damage features obtained individually from both acceleration and strain analysis. The proposed method is validated through a numerical study by utilizing a finite element model of a railway truss bridge. It is shown that while both methods individually can provide information on damage location, and severity, the new framework helps to provide substantially improved damage localization and can overcome the limitations of individual analysis.

Process Modeling in Laser Deposition of Multilayer SS410 Steel

2007 ◽  
Vol 129 (6) ◽  
pp. 1028-1034 ◽  
Author(s):  
Liang Wang ◽  
Sergio Felicelli
Keyword(s):  
Phase Transformation ◽  
Temperature Distribution ◽  
Three Dimensional ◽  
Element Model ◽  
Traverse Speed ◽  
Processing Parameters ◽  
Dimensional Finite Element ◽  
Net Shaping ◽  
Three Dimensional Finite Element ◽  
Continuous Cooling Transformation Diagram

A three-dimensional finite element model was developed to predict the temperature distribution and phase transformation in deposited stainless steel 410 (SS410) during the Laser Engineered Net Shaping (LENS™) rapid fabrication process. The development of the model was carried out using the SYSWELD software package. The model calculates the evolution of temperature in the part during the fabrication of a SS410 plate. The metallurgical transformations are taken into account using the temperature-dependent material properties and the continuous cooling transformation diagram. The ferritic and martensitic transformation as well as austenitization and tempering of martensite are considered. The influence of processing parameters such as laser power and traverse speed on the phase transformation and the consequent hardness are analyzed. The potential presence of porosity due to lack of fusion is also discussed. The results show that the temperature distribution, the microstructure, and hardness in the final part depend significantly on the processing parameters.

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