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Open access

T. Dębiński, M. Głowacki, M. Hojny, A. Gumuła and D. Woźniak

Abstract

The paper presents web base system for an application of parallel object-oriented programming technique in modelling of rolling process of steel plates with semi-solid zone. It also throws light on the problem of semi-solid steels yield stress relationship, one of the main input data of the simulation, and on application of inverse solution, the only possible method of development of the stress-strain curves at extremely high temperatures. Due to limitations of available computer resources a very accurate computation can sometimes be impossible or the time performance can be a barrier for practical application of complex sequential models. Taking advantage of parallel computing the authors have developed an algorithm allowing for fast computation using multiple processors, which is the main subject of the presented paper.

Open access

J. Piekło and M. Maj

Abstract

The article presents the concept of division of a carbon block into single cathode sections to reduce stresses that occur during thermal shock accompanying the operation of pouring cast iron into a shaped groove in which the current-carrying steel pin is mounted. The temperature field and the state of stress were determined by FEM. Experimental measurements were used to determine the core displacement during pouring operation. The calculations were verified by thermovision and photoelastic method. Based on the temperature field and stress field analysis, a method for the block division into sections has been proposed, resulting in a significant reduction of the stress level.

Open access

Lukáš Likavčan, Martin Frnčík, Rudolf Zaujec, Lukáš Satin and Maroš Martinkovič

Abstract

This paper is focused on the process of designing the desired plastic component and injection mould by using the 3D CAD systems. The subsequent FEM analysis of the injection mould process was carried out in order to define shrinkage and deformation of the plastic material by CAE system. The dimensions of the mould were then modified to compensate the shrinkage effect. Machining process (milling and the laser texturing) of the mould was performed by using CAM systems. Finally, after the production of the plastic components by the injection mould technology, the inspection of the plastic component dimensions was carried out by CAQ in order to define the accuracy of the whole CAx chain. It was also demonstrated that CAx systems are an integral part of pre-production and production process.

Open access

T. Niezgoda, D. Miedzińska, E. Małek, P. Kędzierski and G. Sławiński

Abstract

The possibility of using CO2 to fracturing a shale rock has been presented in the paper. The described innovative method which allows for the efficient extraction of shale gas and carbon dioxide storage in a shale rock was developed in Department of Mechanics and Applied Computer Science at the Military University of Technology, Warsaw, Poland. Firstly, the method was verified on the base of analytical and experimental research. In the next stage of the method verification carbon dioxide thermodynamic behavior was studied. The growth in pressure of drop of CO2 heated in a closed volume was numerically tested. The research confirmed the efficiency of the use of carbon dioxide as a medium for fracturing of rocks. The usage of liquid CO2 can be alternative for hydraulic fracturing and is safe for the environment.

Open access

Krzysztof Ostrowski and Aleksander Kozłowski

Abstract

One of the flexibility parameters of semi-rigid joints is rotation capacity. Plastic rotation capacity is especially important in plastic design of framed structures. Current design codes, including Eurocode 3, do not posses procedures enabling designers to obtain value of rotation capacity. In the paper the calculation procedure of the rotation capacity for stiffened bolted flush end-plate beam-to-column connections has been proposed. Theory of experiment design was applied with the use of Hartley’s PS/DS-P:Ha3 plan. The analysis was performed with the use of finite element method (ANSYS), based on the numerical experiment plan. The determination of maximal rotation angle was carried out with the use of regression analysis. The main variables analyzed in parametric study were: pitch of the bolt “w” (120-180 mm), the distance between the bolt axis and the beam upper edge cg1 (50-90 mm) and the thickness of the end-plate tp (10-20 mm). Power function was proposed to describe available rotation capacity of the joint. Influence of the particular components on the rotation capacity was also investigated. In the paper a general procedure for determination of rotation capacity was proposed.

Open access

Wiesław Barnat and Dariusz Sokołowski

Abstract

The paper presents the issue of a knife proof ballistic package. This issue was emphasized since most of modern vests are designed to match the threat posed to them only by firearms. There was observed negligence of protection against melee attacks. There is, thus, a need to develop a research methodology in this matter, because it is a valid and necessary problem in a modern developed society. The aim of this study was to perform a numerical model which simulated the phenomenon of penetration of a ballistic package by an engineering blade. Specification of an engineering blade was taken from standard NIJ Standard-0115.00. Commercial software LSDYNA was used to carry out the analysis.

Open access

Mateusz Celmer and Krzysztof J. Opieliński

Abstract

Linear arrays of ultrasonic transducers are commonly used as ultrasonic probes in medical diagnostics for imaging the interior of a human body in vivo. The crosstalk phenomenon occurs during the operation of transducers in which electrical voltages and mechanical vibrations are transmitted to adjacent components. As a result of such additional excitation of the transducers in the array, the directivity characteristics of the aperture used changes, and consequently there is interference with properoperation of a given array and the emergence of distortions in the obtained ultra sound image that reduce its quality. This paper studies the manner of propagation of mechanical crosstalk in the designed model of a linear array of ultrasonic transducers on the basis of unwanted signals, which appeared on elementary piezo-electric transducers when power is supplied to the selected transducer in the array. The universal model of linear array of ultrasonic transducers, which has been developed, allowed the simulation of mechanical crosstalk, taking in to account the cross-coupling phenomenon in all of its structure with the use of finite elements method (FEM) implemented in COMSOL Multiphysics software. The analysis of crosstalk signals showed that they consist of aggregated pulses propagating with different speeds and frequencies. This signifies the formation of different vibration modes transmitted simultaneously via different paths. The paper is an original approach which enables to identify different vibration modes and estimate their participation in the crosstalk signal and their ways of propagation. Conclusions from the research allow predicting specific design changes which are significant due to the minimization of mechanical crosstalk in linear arrays of ultrasonic transducers.

Open access

Wanyi Tian, Lingyun Yao and Li Li

Abstract

Nowadays, the finite element method (FEM) - boundary element method (BEM) is used to predict the performance of structural-acoustic problem, i.e. the frequency response analysis, modal analysis. The accuracy of conventional FEM/BEM for structural-acoustic problems strongly depends on the size of the mesh, element quality, etc. As element size gets greater and distortion gets severer, the deviation of high frequency problem is also clear. In order to improve the accuracy of structural-acoustic problem, a smoothed finite-element/boundary-element coupling procedure (SFEM/BEM) is extended to analyze the structural-acoustic problem consisting of a shell structure interacting with the cavity in this paper, in which the SFEM and boundary element method (BEM) models are used to simulate the structure and the fluid, respectively. The governing equations of the structural-acoustic problems are established by coupling the SFEM for the structure and the BEM for the fluid. The solutions of SFEM are often found to be much more accurate than those of the FEM model. Based on its attractive features, it was decided in the present work to extend SFEM further for use in structural-acoustic analysis by coupling it with BEM, the present SFEM/BEM is implemented to predict the vehicle structure-acoustic frequency response analysis, and two numerical experiments results show that the present method can provide more accurate results compared with the standard FEM/BEM using the same mesh. It indicates that the present SFEM/BEM can be widely applied to solving many engineering noise, vibration and harshness (NVH) problems with more accurate solutions.

Open access

Andrzej Gołaś and Roman Filipek

Abstract

The aim of this paper is to present methods of digitally synthesising the sound generated by vibroacoustic systems with distributed parameters. A general algorithm was developed to synthesise the sounds of selected musical instruments with an axisymmetrical shape and impact excitation, i.e., Tibetan bowls and bells. A coupled mechanical-acoustic field described by partial differential equations was discretized by using the Finite Element Method (FEM) implemented in the ANSYS package. The presented synthesis method is original due to the fact that the determination of the system response in the time domain to the pulse (impact) excitation is based on the numerical calculation of the convolution of the forcing function and impulse response of the system. This was calculated as an inverse Fourier transform of the system’s spectral transfer function. The synthesiser allows for obtaining a sound signal with the assumed, expected parameters by tuning the resonance frequencies which exist in the spectrum of the generated sound. This is accomplished, basing on the Design of Experiment (DOE) theory, by creating a meta-model which contains information on its response surfaces regarding the influence of the design parameters. The synthesis resulted in a sound pressure signal in selected points in space surrounding the instrument which is consistent with the signal generated by the actual instruments, and the results obtained can improve them.

Open access

Paweł Błażejewski and Jakub Marcinowski

Abstract

Assessment of buckling resistance of pressurised spherical cap is not an easy task. There exist two different approaches which allow to achieve this goal. The first approach involves performing advanced numerical analyses in which material and geometrical nonlinearities would be taken into account as well as considering the worst imperfections of the defined amplitude. This kind of analysis is customarily called GMNIA and is carried out by means of the computer software based on FEM. The other, comparatively easier approach, relies on the utilisation of earlier prepared procedures which enable determination of the critical resistance pRcr, the plastic resistance pRpl and buckling parameters a, b, h, l 0 needed to the definition of the standard buckling resistance curve. The determination of the buckling capacity curve for the particular class of spherical caps is the principal goal of this work. The method of determination of the critical pressure and the plastic resistance were described by the authors in [1] whereas the worst imperfection mode for the considered class of spherical shells was found in [2]. The determination of buckling parameters defining the buckling capacity curve for the whole class of shells is more complicated task. For this reason the authors focused their attention on spherical steel caps with the radius to thickness ratio of R/t = 500, the semi angle j = 30o and the boundary condition BC2 (the clamped supporting edge). Taking into account all imperfection forms considered in [2] and different amplitudes expressed by the multiple of the shell thickness, sets of buckling parameters defining the capacity curve were determined. These parameters were determined by the methods proposed by Rotter in [3] and [4] where the method of determination of the exponent h by means of additional parameter k was presented. As a result of the performed analyses the standard capacity curves for all considered imperfection modes and amplitudes 0.5t, 1.0t, 1.5t were obtained. Obtained capacity curves were compared with the recommendations for different fabrication quality classes formulated in [5].