In the paper an important issue of vibrations of the transmission line in real conditions was analyzed.Such research was carried out by the authors of this paper taking into account the cross-section of the cable bein...In the paper an important issue of vibrations of the transmission line in real conditions was analyzed.Such research was carried out by the authors of this paper taking into account the cross-section of the cable being in use on the transmission line.Analysis was performed for the modern ACSR high voltage transmission line with span of 213.0 m.The purpose of the investigation was to analyze the vibrations of the power transmission line in the natural environment and compare with the results obtained in the numerical simulations.Analysis was performed for natural and wind excited vibrations.The numerical model was made using the Spectral Element Method.In the spectral model,for various parameters of stiffness,damping and tension force,the system response was checked and compared with the results of the accelerations obtained in the situ measurements.A frequency response functions(FRF)were calculated.The credibility of the model was assessed through a validation process carried out by comparing graphical plots of FRF functions and numerical values expressing differences in acceleration amplitude(MSG),phase angle differences(PSG)and differences in acceleration and phase angle total(CSG)values.Particular attention was paid to the hysteretic damping analysis.Sensitivity of the wave number was performed for changing of the tension force and section area of the cable.The next aspect constituting the purpose of this paper was to present the wide possibilities of modelling and simulation of slender conductors using the Spectral Element Method.The obtained results show very good accuracy in the range of both experimental measurements as well as simulation analysis.The paper emphasizes the ease with which the sensitivity of the conductor and its response to changes in density of spectral mesh division,cable cross-section,tensile strength or material damping can be studied.展开更多
Random vibration control is aimed at reproducing the power spectral density （PSD） at specified control points. The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple fre...Random vibration control is aimed at reproducing the power spectral density （PSD） at specified control points. The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple frequency response functions （FRFs）, which lengthens the control loop time in the equalization process. Likewise, the feedback control algorithm has a very slow convergence rate due to the small value of the feedback gain parameter to ensure stability of the system. To overcome these limitations, an adaptive inverse control of random vibrations based on the filtered-X least mean-square （LMS） algorithm is proposed. Furthermore, according to the description and iteration characteristics of random vibration tests in the frequency domain, the frequency domain LMS algorithm is adopted to refine the inverse characteristics of the FRF instead of the traditional time domain LMS algorithm. This inverse characteristic, which is called the impedance function of the system under control, is used to update the drive PSD directly. The test results indicated that in addition to successfully avoiding the instability problem that occurs during the iteration process, the adaptive control strategy minimizes the amount of time needed to obtain a short control loop and achieve equalization.展开更多
This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design meth...This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.展开更多
文摘In the paper an important issue of vibrations of the transmission line in real conditions was analyzed.Such research was carried out by the authors of this paper taking into account the cross-section of the cable being in use on the transmission line.Analysis was performed for the modern ACSR high voltage transmission line with span of 213.0 m.The purpose of the investigation was to analyze the vibrations of the power transmission line in the natural environment and compare with the results obtained in the numerical simulations.Analysis was performed for natural and wind excited vibrations.The numerical model was made using the Spectral Element Method.In the spectral model,for various parameters of stiffness,damping and tension force,the system response was checked and compared with the results of the accelerations obtained in the situ measurements.A frequency response functions(FRF)were calculated.The credibility of the model was assessed through a validation process carried out by comparing graphical plots of FRF functions and numerical values expressing differences in acceleration amplitude(MSG),phase angle differences(PSG)and differences in acceleration and phase angle total(CSG)values.Particular attention was paid to the hysteretic damping analysis.Sensitivity of the wave number was performed for changing of the tension force and section area of the cable.The next aspect constituting the purpose of this paper was to present the wide possibilities of modelling and simulation of slender conductors using the Spectral Element Method.The obtained results show very good accuracy in the range of both experimental measurements as well as simulation analysis.The paper emphasizes the ease with which the sensitivity of the conductor and its response to changes in density of spectral mesh division,cable cross-section,tensile strength or material damping can be studied.
基金Program for New Century Excellent Talents in Universities Under Grant No.NCET-04-0325
文摘Random vibration control is aimed at reproducing the power spectral density （PSD） at specified control points. The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple frequency response functions （FRFs）, which lengthens the control loop time in the equalization process. Likewise, the feedback control algorithm has a very slow convergence rate due to the small value of the feedback gain parameter to ensure stability of the system. To overcome these limitations, an adaptive inverse control of random vibrations based on the filtered-X least mean-square （LMS） algorithm is proposed. Furthermore, according to the description and iteration characteristics of random vibration tests in the frequency domain, the frequency domain LMS algorithm is adopted to refine the inverse characteristics of the FRF instead of the traditional time domain LMS algorithm. This inverse characteristic, which is called the impedance function of the system under control, is used to update the drive PSD directly. The test results indicated that in addition to successfully avoiding the instability problem that occurs during the iteration process, the adaptive control strategy minimizes the amount of time needed to obtain a short control loop and achieve equalization.
基金Project (No. 03-02-02-0056 PR0025/04-03) supported by the Inten-sification of Research in Priority Areas (IRPA), Ministry of Science,Technology and Innovation, Malaysia
文摘This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.
