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Effects of accelerometer mass on natural frequency of a magnesium alloy cantilever beam
Get PDFThe aim of the paper is to study the effects of an accelerometer mass on natural frequency of a cantilever beam of AZ61 magnesium alloy. The fundamental natural frequency of the beam is determined experimentally using vibration analyzer OROS-34 for different location of accelerometer mass on the beam. Vibration in the beam is generated by a lightweight hand hammer. Analytical formulation is done to calculate modal properties of a mass loaded beam. Further, the problem is simulated using ANSYS and the simulated results are compared with the experimental and analytical results
Dynamic load computational modelling of containers placed on a flat wagon at railroad ferry transportation
Get PDFThe article presents result of computational modelling of container dynamic load during transportation as a part of trains of intermodal transport on a railway ferry. The computational models were developed which account the movement of the container with regard to the frame of the flat wagon while moving of the railway ferry. It was assumed that there is no movement of the flat wagon with regard to the deck, since these movements were limited by fastening means. The obtained acceleration rates, as components of the dynamic loads acting on the container, were accounted while determining the containers stability coefficient with regard to the flat wagons. The railway ferry heeling angles which ensure the stability of the containers were determined. The researches will ensure safety of transportation of containers as a part of trains of intermodal transport on a railway ferry, as well as increase the efficiency of operation of intermodal transport in the international transport
A breeze energy harvesting of vibration caused with a cantilevered piezoelectric beam
Get PDFThe researches of wind energy harvesting have been more and more popular in recent years. In the paper, a vibration energy caused by a breeze is harvested with a cantilevered beam using a piezoelectric patch. When a swaging fan applies a breeze environment, the alternating voltage generates from the piezoelectric patch. Moreover, by designing a full wave rectifier, the alternating voltage from the piezoelectric patch is transformed as a DC voltage. Through some experiments, the amplitude of the alternating voltage is about 2.70 V and its frequency is 2.60 Hz (the first natural frequency of the cantilevered beam). And the gained DC voltage is about 2.45 V and can be made a luminous diode be on. These experimental results indicate that vibration energy caused by the breeze can be harvested with a full wave rectifier
Damage identification of bridge structure based on frequency domain decomposition and strain mode
Get PDFBecause it is difficult to determine the degree and location of damage to bridge structures under environmental excitation, a new method combining frequency domain decomposition and strain mode identification for bridge structure damage assessment is proposed and the related identification principle is derived. General variations in the strain mode parameters of different reinforced concrete beam damage states are accordingly studied under ambient excitation. The results show that the proposed strain mode identification method based on frequency domain decomposition has good anti-noise performance and can identify the strain mode parameters of a structure relying solely on the strain response information of the structure, even under strong background noise. The mutation of the strain mode was effectively used to determine the damage condition of reinforced concrete beams, and the adaptability, feasibility, and reliability of the proposed method for modal parameter and damage identification of reinforced concrete beams under environmental excitation were verified
Comparative study for material effect on stress behaviourial characteristics of rectangular plate
Get PDFThe circular cutout is considered as a typical source of stress concentrations in rectangular plate type structures. The proper position of a cutout in a rectangular plate can be significantly affected by the choice of material, cutout size, and various end conditions which are relative to the externally applied force. The research work entitled in this paper deals with the finite element formulation applied to a plate made with isotropic and laminated plates subjected to uniform pressure with various end conditions. The vicinity of stress distribution for the rectangular plate made of these two materials with and without the effect of circular cutouts is discussed. The accuracy of the solution verified with the available literature, and from the comparison, a fairly good agreement seen between the Finite element formulations in this paper with previously available results
Dynamics similarity design and verification of rotor system
Get PDFIn order to study the dynamics similarity of original model similar to normal model, the similarity criteria and the similarity ratio of the normal and original models for the rotor system were derived by the dimension analysis method. ANSYS was used to numerically calculate the critical speeds, modal shapes and harmonic response of the original and normal models of rotor system. The analysis results show that, for the rotor system, the dynamic characteristics of the normal and original models satisfy the requirement of the similarity criteria perfectly. The dynamic characteristics of the original model can be predicted accurately by the corresponding normal model
Effects of the wide-body suspension bridge auxiliary structure on flutter characteristics by CFD
Get PDFThis paper is focused on the CFD numerical simulation of flutter characteristics of the wide-body flat steel box girder of Chongqing Cuntan Yangtze Bridge. The specific influence on the aerodynamic performance and flutter critical wind velocity have been studied by setting different railing ventilation rates. The results show that: the subsidiary structures of the main beam have an adverse effect on the stability of bridge flutter. The ventilation rate of the railings affects the flutter derivatives and the critical wind speed of the flutter
Nonlinear crack assessment method in beams based on bispectrum-normal cloud model
Get PDFFatigue damage in engineering structures is universal. The occurrence of fatigue cracks brings unpredictable hidden dangers to a structure in terms of safety and service performance. Traditional damage identification methods, such as power spectrum analysis, are mostly based on linear elasticity theory that cannot reflect the typical nonlinear characteristics of fatigue cracks and cannot meet the higher requirements of the signal analysis method put forward by current mass detection data. To solve this problem, a numerical model of a cantilever beam with a breathing crack is established in this study. A method for diagnosing fatigue damage is studied by combining bispectral analysis and a statistical normal cloud model, which characterize the nonlinear characteristics of the structure. This method can effectively describe the nonlinear characteristics of the structure and reasonably evaluate the degree of fatigue damage in the structure. The bispectrum-normal cloud model method proposed in this study overcomes the limitations of existing linear damage detection methods in nonlinear damage detection, and can improve the efficiency of signal analysis from a statistical point of view. It has good prospects for structural nonlinear damage assessment
A multi-fault diagnosis method for piston pump in construction machinery based on information fusion and PSO-SVM
Get PDFPiston pumps are key components in construction machinery, the failure of which may cause long delay of the construction work and even lead to serious accident. Because construction machines are exposed to poor working conditions, multiple faults of piston pumps are most likely to occur simultaneously. When multiple faults occur together, it is difficult to detect. A multi-fault diagnosis method for piston pump based on information fusion and PSO-SVM is proposed in this thesis. Information fusion is used as fault feature extraction and PSO-SVM is applied as the fault mode classifier. According to the method, vibration signal and pressure signal of piston pump in normal state, single fault state and multi-fault state are collected at first. Then the empirical mode decomposition (EMD) is used to decompose vibration signals into different frequency band and energy features are extracted. These energy features extracted from vibration signals and time-domain features extracted from pressure signal are information fused at the feature layer and constitute the eigenvectors. Finally, these eigenvectors are put into support vector machine (SVM) and the working conditions of piston pump were classified. Particle swarm optimization (PSO) is applied to optimize two parameters of SVM. The experimental results show that the recognition accuracy of the normal state, three single failure modes and multi-fault modes are 98.3 %, 97.6 % and 94 % respectively. These recognition accuracies are higher than which using vibration signal or pressure signal alone. So, the proposed method can not only identify the single fault, but also effectively identify the multi-fault of piston pump
Dynamic pressure on lock gate structure coupled with fluid
Get PDFThe effect of fluid on the dynamic pressure distribution of a rectangular lock gate structure subjected to external harmonic ground acceleration is studied. The fluid is assumed to be inviscid and incompressible, having an irrotational flow. Pressure for fluid domain and displacement for lock gate are considered as nodal variables in the finite element formulation. The interaction of coupled problem is maintained by transferring acceleration of the lock gate to fluid and pressure of the fluid to lock gate. Mindlin’s plate theory is used to formulate the lock gate. The Laplace equation is solved using Fourier half range cosine series expansion to truncate the far boundary nearer to the lock gate. The time dependent forced vibration equations are solved by using Newmark-beta time integration method