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Analysis of vibrations in a modeled ballasted track using measured rail defects
Get PDFVibrations generated by trains and transmitted to the ground and nearby structures are a known source of problems associated with railway transport. Therefore this phenomenon should be studied in detail to avoid a negative impact on the environment. Within this framework, the article develops an improved version of a previously published analytical model capable of predicting ground vibrations caused by the passing railway vehicles. The new features include a new formulation of the models with five layers of material and an enhanced load input process that takes into account actual rail defects data as well as the Hertz theory for the rail-wheel contact. The model is adapted to a conventional ballasted track in Solares (Spain) as well as calibrated and validated with data collected on site. Hence the model is proved to be able to properly reproduce vibrations for the case of varying track typologies, constituting a useful research and design tool
Oscillations of cylinder piston rod – comparison of amplitudes and frequencies for the transient phenomena in tap water- and oil-based PCHS
Get PDFPower-control hydraulic system (PCHS), as a part of a machine or production line, provides it with all or most of the necessary movements. Most of the movements in PCHS are carried out by means of hydraulic cylinders. In this case movements are mostly generated by cylinder piston rods. More or less obvious transient phenomena occur during these movements under conditions of acceleration and deceleration. As a consequence, oscillations are induced in the system. In our work we investigate the phenomena and parameters of such PCHS for two hydraulic fluids. Most of the PCHSs still use mineral oil as hydraulic fluid but it is environmentally very harmful. Ecological awareness during natural disasters and man-made pollution is the subject of much discussion. It is everybody’s responsibility to take care of the natural environment and reduce the threats to our future existence. The preservation of drinking water and the prevention of its contamination by pollution are particularly important. Powercontrol hydraulics is one important area in which a positive step could be made to protect the resources of drinking water. The use of tap water instead of the conventional hydraulic fluids in power-control hydraulics is one of the most environmentally friendly changes that could be implemented. Therefore in this paper we show, based on dynamic-transient parameters, both the functionality and the usability of water hydraulics in comparison to the more familiar oil hydraulics. A comparison of the dynamic behavior between the conventional oil and the relatively new water hydraulics under the same conditions is described. Mineral hydraulic oil was used in the oil hydraulic test rig and distilled water was used in the water hydraulic test rig. The tests were conducted at different flow rates (11, 22 and 33 lpm) and system pressures (70, 110 and 160 bar) as well as applying different loading conditions (first, with a mass of 163 kg in the horizontal and vertical positions and, second, without the mass). The registered amplitudes of the cylinder piston rod oscillations were 20-30 % smaller in the water hydraulics with respect to the case of oil hydraulics, while the frequencies of the piston rod oscillations were 7-20 % higher
Approach to modeling of thermal airflow dynamics
Get PDFThis work considers the modeling of thermal airflow. The dynamic airflow is spit on flat circular elements. The extrapolation method, which is referred to as adaptive extrapolation, is proposed. The extrapolation which is influenced by stochastically changing settings is the key for adaptive extrapolation. The change of these parameters is determined experimentally during real flight or using prediction techniques. This paper presents modeling with preset parameters. The thermal airflow is modeled by taking into account its inclination towards wind and the change of diameter in accordance with linear and nonlinear laws
Impact of anti-intrusion beam effectiveness on reducing fatalities and injuries of vehicle occupants
Get PDFSide impact of vehicles is the second leading cause of fatalities and serious injuries in the traffic accidents after frontal collisions. The paper deals with the evaluation of effectiveness of anti-intrusion beam in vehicle side door. The presented analysis aims to determine the influence of the considered passive safety device on reduction of occupant fatalities and injuries. Results of dynamic numerical investigation are presented. The analysis of estimated deflection indicates the potential for reduction of the depth and velocity of door intrusion
Investigation of eigenvalue problem of water tower construction interacting with fluid
Get PDFThe paper concerns problems, in which both the structural and fluid responses of a complex construction to mechanical actions are strongly coupled. Particularly, there are treated problems, in which the structural dynamic response to actions is significantly affected by the presence of the fluid in the structure. The work presents the evolution of the way of solving that problem of the complex solution of the generalized problem of the structure using multiphysical ANSYS program package. The formulation of fluid finite elements is discussed, considering both pressure (Euler) with/without sloshing and displacement (Lagrange) approaches. The solution is demonstrated on thin-walled steel water tower structure
Incipient defect identification in rolling bearings using adaptive lifting scheme packet
Get PDFDefects on the surface of rolling bearing elements are some of the most frequent causes of malfunctions and breakages of rotating machines. Defect detection in rolling bearings via techniques that examine changes in measured signal is a very important topic of research due to increasing demands for quality and reliability. In this paper, incipient defect identification method based on adaptive lifting scheme packet is proposed. Adaptive lifting scheme packet operators which adapt to the signal characteristic are constructed. The shock pulse value in defect sensitive frequency band is used as the defect indicator to identify the defect location and severity of rolling bearing. The proposed defect identification method is applied to analyze the experimental signal from rolling bearing with incipient inner raceway defect. The result confirms that the proposed method is accurate and robust in rolling bearing incipient defect identification
Propagation of weak waves in the inhomogeneous elastoviscoplastic medium with a cell structure
Get PDFNon-stationary acceleration waves in the fluid-saturated inhomogeneous elastoviscoplastic porous medium are studied using the mathematical theory of discontinuities. The equations for determining the intensity and the geometry of wave fronts of the fluidsaturated elastoviscoplastic medium were first derived. It is shown that in the medium under consideration there are two types of irrotational waves and one equivoluminal wave, that are equal to the velocities in the homogeneous elastic porous media at every point
Coherence analysis and transfer function model for ceramic plate vibrations
Get PDFCorrelations on the state of ceramic plates, that are either intact or cracked, are performed through the data obtained. In the analysis the frequency range of coherence has been identified in the form of the two regions. Low-frequency region is spectral amplitude that is below the threshold defined by the level of coherence about 0.2, which is on the level of little correlation. This region is in the frequency range of approximately 0-28 kHz. In this frequency range a weak correlation between the spectra of solid ceramic plates and cracked ones is observed
FRF-based model updating using SMURF technique
Get PDFFinite element (FE) method is a well-known technique in structural dynamic analysis. However, FE models may be inaccurate or even incorrect due to erroneous modeling, geometrical over-simplification or uncertainties in the element and joint properties. In contrast, modal models are generally considered to be correct or at least closely matching the actual dynamic behavior of a structure. Therefore, a model updating procedure should be introduced for adjusting the analytical model in order to reconcile theoretical and experimental results. In this paper, a new FRF-based model updating method is proposed based on the Structural modification using experimental frequency response functions (SMURF) method. It is demonstrated that the proposed method updates the parameters accurately using just a few frequency response functions from the mis-modeled regions. A 12-DOF mass-spring system is considered as a test case in a simulated experiment. The convergence of the method and its capacity to improve the accuracy of the FE model are evaluated. Moreover, the paper considers the effect of the number of modes, the frequency range of interest used in the calculations as well as the coordinate incompleteness and noise on the quality of the updated model. The updated models are compared in terms of the predicted natural frequencies, mode shapes and frequency response functions
A hybrid frequency response function formulation for MDOF nonlinear systems
Get PDFThis paper introduces a hybrid technique for formulation of frequency response functions (FRFs) for nonlinear MDOF systems, based on the Structural modification using frequency response function (SMURF) technique. The technique can produce FRFs at the desired coordinates on the structure. The term “hybrid” indicates that the underlying linear system is reduced by expressing it in FRF form, while the nonlinearities are treated in the form of describing functions based on spatial elements. The method uses several FRFs instead of the spatial model therefore it is characterized by lower computational costs. Moreover, the experimentally measured FRFs of the underlying linear structure can be applied in this technique. A system with cubic stiffness and friction damping nonlinearities is used as a numerical case study to verify the proposed technique