Pub Date : 2019-12-31DOI: 10.20855/ijav.2019.24.41365
A. Oveisi, T. Nestorović
In the controllers that are synthesized on a nominal model of a nonlinear plant, the parametric matched uncertainties and nonlinear/unmodelled dynamics of the high order nature can significantly affect the performance of the closedloop system. On this note, owing to the robust characteristic of the sliding mode observer against modelling perturbations, measurement noise, and unknown disturbances and due to the non-fragile behaviour of the Kalman filter against process noise, a mixed Kalman sliding mode state-observer is proposed and later enhanced by the addition of an intelligent fuzzy agent. In light of the proposed technique, the chattering phenomena and the conservative boundary neighboring layer of the high gain sliding mode observer are addressed. Then, a robust active disturbance rejection controller is developed by using the static feedback of the estimated states using a direct Lyapunov quadratic stability theorem. The reduced order plant for control design purposes is subjected to some simulated square-integrable disturbances and is assumed to have mismatched uncertainties in the system matrices. Finally, the robust performance of the closed-loop scheme with respect to the mentioned perturbation signals and modelling imperfections is tested by implementing the control system on a mechanical vibrating smart cantilever beam.
{"title":"Mixed Kalman-Fuzzy Sliding Mode State Observer in Disturbance Rejection Control of a Vibrating Smart Structure","authors":"A. Oveisi, T. Nestorović","doi":"10.20855/ijav.2019.24.41365","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41365","url":null,"abstract":"In the controllers that are synthesized on a nominal model of a nonlinear plant, the parametric matched uncertainties and nonlinear/unmodelled dynamics of the high order nature can significantly affect the performance of the closedloop system. On this note, owing to the robust characteristic of the sliding mode observer against modelling perturbations, measurement noise, and unknown disturbances and due to the non-fragile behaviour of the Kalman filter against process noise, a mixed Kalman sliding mode state-observer is proposed and later enhanced by the addition of an intelligent fuzzy agent. In light of the proposed technique, the chattering phenomena and the conservative boundary neighboring layer of the high gain sliding mode observer are addressed. Then, a robust active disturbance rejection controller is developed by using the static feedback of the estimated states using a direct Lyapunov quadratic stability theorem. The reduced order plant for control design purposes is subjected to some simulated square-integrable disturbances and is assumed to have mismatched uncertainties in the system matrices. Finally, the robust performance of the closed-loop scheme with respect to the mentioned perturbation signals and modelling imperfections is tested by implementing the control system on a mechanical vibrating smart cantilever beam.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"24 1","pages":"677-686"},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49362648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-31DOI: 10.20855/ijav.2019.24.41393
Y. Mirzaei
An exact size-dependent elasticity solution based on surface energy theory is used to investigate the free radial vibration behavior of a nanoscale sphere. The Gurtin-Murdoch surface elasticity model is employed to incorporate surface stress terms into pertinent boundary conditions. This leads to frequency equations involving spherical Bessel functions. Extensive numerical calculations have been carried out to illustrate the size effect of the nanosphere on the first and second dimensionless breathing natural frequencies. The numerical results describe the imperative influence of surface energy and radii ratio on the vibrational characteristic frequency of the nano-sphere. In particular, the surface energy is much more important when the inner radius is smaller than 50 nm.
{"title":"Exact Size-Dependent Elasticity Solution for Free Radial Vibration of Nano-Sphere","authors":"Y. Mirzaei","doi":"10.20855/ijav.2019.24.41393","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41393","url":null,"abstract":"An exact size-dependent elasticity solution based on surface energy theory is used to investigate the free radial vibration behavior of a nanoscale sphere. The Gurtin-Murdoch surface elasticity model is employed to incorporate surface stress terms into pertinent boundary conditions. This leads to frequency equations involving spherical Bessel functions. Extensive numerical calculations have been carried out to illustrate the size effect of the nanosphere on the first and second dimensionless breathing natural frequencies. The numerical results describe the imperative influence of surface energy and radii ratio on the vibrational characteristic frequency of the nano-sphere. In particular, the surface energy is much more important when the inner radius is smaller than 50 nm.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"24 1","pages":"687-692"},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49512423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-31DOI: 10.20855/ijav.2019.24.41455
M. Talbi, M. Bouhlel
In this paper, a new speech compression technique is proposed. This technique applies a Psychoacoustic Model and a general approach for Filter Bank Design using optimization. It is evaluated and compared with a compression technique using a MDCT (Modified Discrete Cosine Transform) Filter Bank of 32 Filters and a Psychoacoustic Model. This evaluation and comparison is performed by calculating bits before and after compression, PSNR (Peak Signal to Noise Ratio), NRMSE (Normalized Root Mean Square Error), SNR (Signal to Noise Ratio) and PESQ (Perceptual evaluation of speech quality) computations. The two techniques are tested and applied to a number of speech signals that are sampled at 8 kHz. The results obtained from this evaluation show that the proposed technique outperforms the second compression technique (based on a Psychoacoustic Model and MDCT filter Bank) in terms of Bits after compression and compression ratio. In fact, the proposed technique yields higher values for the compression ratio than the second compression technique. Moreover, the proposed compression technique presents reconstructed speech signals with acceptable perceptual qualities. This is justified by the values of SNR, PSNR and NRMSE and PESQ.
{"title":"New Speech Compression Technique based on Filter Bank Design and Psychoacoustic Model","authors":"M. Talbi, M. Bouhlel","doi":"10.20855/ijav.2019.24.41455","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41455","url":null,"abstract":"In this paper, a new speech compression technique is proposed. This technique applies a Psychoacoustic Model and a general approach for Filter Bank Design using optimization. It is evaluated and compared with a compression technique using a MDCT (Modified Discrete Cosine Transform) Filter Bank of 32 Filters and a Psychoacoustic Model. This evaluation and comparison is performed by calculating bits before and after compression, PSNR (Peak Signal to Noise Ratio), NRMSE (Normalized Root Mean Square Error), SNR (Signal to Noise Ratio) and PESQ (Perceptual evaluation of speech quality) computations. The two techniques are tested and applied to a number of speech signals that are sampled at 8 kHz. The results obtained from this evaluation show that the proposed technique outperforms the second compression technique (based on a Psychoacoustic Model and MDCT filter Bank) in terms of Bits after compression and compression ratio. In fact, the proposed technique yields higher values for the compression ratio than the second compression technique. Moreover, the proposed compression technique presents reconstructed speech signals with acceptable perceptual qualities. This is justified by the values of SNR, PSNR and NRMSE and PESQ.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"24 1","pages":"728-735"},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45732317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-31DOI: 10.20855/ijav.2019.24.41335
Vikas Kumar, V. Saran
The seat-to-head transmissibility and apparent mass characteristics are measured for the seated human subjects exposed to vertical whole-body vibration in the 0.5–20 Hz frequency range at a vibration magnitude of 1.0 m/s2 rms. The experiments are conducted on test subjects seated in an upright posture. A biodynamic model has been developed for bio-mechanical parameters that are estimated on the basis of identified biodynamic responses. The parameters identification technique employs a genetic algorithm for the solution of the function comprising sum of squared magnitude and phase errors related with target values of seat-to-head transmissibility and apparent mass. The developed model presents the target values of magnitude associated with apparent mass and seat-tohead transmissibility. The natural frequencies of the model have been found at up to 5.0896 Hz. The model also presents the resonant frequencies calculated on the basis of both biodynamic response functions very close to that found for seated human body experimentally.
{"title":"Biodynamic Model of the Seated Human Body under the Vertical Whole Body Vibration Exposure","authors":"Vikas Kumar, V. Saran","doi":"10.20855/ijav.2019.24.41335","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41335","url":null,"abstract":"The seat-to-head transmissibility and apparent mass characteristics are measured for the seated human subjects exposed to vertical whole-body vibration in the 0.5–20 Hz frequency range at a vibration magnitude of 1.0 m/s2 rms. The experiments are conducted on test subjects seated in an upright posture. A biodynamic model has been developed for bio-mechanical parameters that are estimated on the basis of identified biodynamic responses. The parameters identification technique employs a genetic algorithm for the solution of the function comprising sum of squared magnitude and phase errors related with target values of seat-to-head transmissibility and apparent mass. The developed model presents the target values of magnitude associated with apparent mass and seat-tohead transmissibility. The natural frequencies of the model have been found at up to 5.0896 Hz. The model also presents the resonant frequencies calculated on the basis of both biodynamic response functions very close to that found for seated human body experimentally.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"24 1","pages":"657-664"},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46177229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.20855/IJAV.2018.23.1E87
J. Arenas
{"title":"Towards an International Year of Sound","authors":"J. Arenas","doi":"10.20855/IJAV.2018.23.1E87","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.1E87","url":null,"abstract":"","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44416410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.20855/IJAV.2018.23.11069
A. Mishra, Althaf Mohammed, S. Chakraborty
Fiber reinforced plastics (FRP) is increasingly being used in infrastructural applications like bridges, chemical plants etc., where the environment can limit the expected service life of structures made of conventional materials such as reinforced concrete, steel or timber. Advantages of FRP over conventional constructional materials are its high specific strength and specific stiffness, ease with which it can be moulded to various shapes, corrosion resistance, lower lifecycle cost, durability etc. Estimation of accurate dynamic responses of FRP structures is very important from their operation point of view. Such dynamic responses are functions of material properties, boundary conditions, geometry and applied loading. FRP being an anisotropic and layered composite material, a large number of elastic material property parameters are to be determined. Moreover, its structural fabrication and material fabrication at constituent level being one unified process, the actual existing material property parameters may vary considerably from those specified in established standards or determined from characterisation tests. The present approach attempts at establishing a nondestructive technique based on experimental modal testing and finite element model updating to estimate the elastic material parameters of an ‘I’ beam made of FRP, thereby making the prediction of dynamic responses more accurate. Static load test on the beam and characterisation tests on samples cut from actual structure are conducted to assess the performance of this updating exercise. The current approach can also be used to nondestructively monitor degradations of elastic material properties over time and thus can be used for health monitoring of existing FRP structures.
{"title":"Improved Numerical Modelling of Fiber Reinforced Plastics I-Beam from Experimental Modal Testing and Finite Element Model Updating","authors":"A. Mishra, Althaf Mohammed, S. Chakraborty","doi":"10.20855/IJAV.2018.23.11069","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.11069","url":null,"abstract":"Fiber reinforced plastics (FRP) is increasingly being used in infrastructural applications like bridges, chemical plants etc., where the environment can limit the expected service life of structures made of conventional materials such as reinforced concrete, steel or timber. Advantages of FRP over conventional constructional materials are its high specific strength and specific stiffness, ease with which it can be moulded to various shapes, corrosion resistance, lower lifecycle cost, durability etc. Estimation of accurate dynamic responses of FRP structures is very important from their operation point of view. Such dynamic responses are functions of material properties, boundary conditions, geometry and applied loading. FRP being an anisotropic and layered composite material, a large number of elastic material property parameters are to be determined. Moreover, its structural fabrication and material fabrication at constituent level being one unified process, the actual existing material property parameters may vary considerably from those specified in established standards or determined from characterisation tests. The present approach attempts at establishing a nondestructive technique based on experimental modal testing and finite element model updating to estimate the elastic material parameters of an ‘I’ beam made of FRP, thereby making the prediction of dynamic responses more accurate. Static load test on the beam and characterisation tests on samples cut from actual structure are conducted to assess the performance of this updating exercise. The current approach can also be used to nondestructively monitor degradations of elastic material properties over time and thus can be used for health monitoring of existing FRP structures.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.20855/IJAV.2018.23.11078
S. Kaewunruen
This paper presents the utilisation of dynamic wheel/rail interaction to monitor rail corrugation growth already detected on sharp curved tracks, in order to prioritise track maintenance. In general, a railway network generally spans over a large distance, so the structural health monitoring of such a rail infrastructure system is one of the grand challenges in rail industry practice. Especially in an underground or subway system, the facilities, resources, and time period permitted for critical infrastructure inspection and maintenance is considerably limited. As a result, the utilisation and application of any inspection train vehicle has been more demanding than ever. A rail corrugation defect is the periodic, undulated or wave-like vertical alignment of rail surface. Corrugations are typically caused by uneven wears due to the variations of wheel-rail contact stresses. The wavelength and severity of rail corrugations is dependent on track structure, track geometry, traction system, rail vehicle behaviours, and wheel-rail interaction. The rail corrugations are the source of rapid track degradation, poor ride comfort, and nuisance noise. Often, such rail irregularities are initially observed and detected by train drivers and engine ride inspectors. To enable predictive maintenance, a set of rail surface data of a very sharp curve was chosen for demonstration of rail corrugation monitoring by integrating numerical train/track simulations, axle box acceleration data obtained from the calibrated track inspection vehicle ”AK Car”, and spectral data analytics.
{"title":"Monitoring of Rail Corrugation Growth on Sharp Curves For Track Maintenance Prioritisation","authors":"S. Kaewunruen","doi":"10.20855/IJAV.2018.23.11078","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.11078","url":null,"abstract":"This paper presents the utilisation of dynamic wheel/rail interaction to monitor rail corrugation growth already detected on sharp curved tracks, in order to prioritise track maintenance. In general, a railway network generally spans over a large distance, so the structural health monitoring of such a rail infrastructure system is one of the grand challenges in rail industry practice. Especially in an underground or subway system, the facilities, resources, and time period permitted for critical infrastructure inspection and maintenance is considerably limited. As a result, the utilisation and application of any inspection train vehicle has been more demanding than ever. A rail corrugation defect is the periodic, undulated or wave-like vertical alignment of rail surface. Corrugations are typically caused by uneven wears due to the variations of wheel-rail contact stresses. The wavelength and severity of rail corrugations is dependent on track structure, track geometry, traction system, rail vehicle behaviours, and wheel-rail interaction. The rail corrugations are the source of rapid track degradation, poor ride comfort, and nuisance noise. Often, such rail irregularities are initially observed and detected by train drivers and engine ride inspectors. To enable predictive maintenance, a set of rail surface data of a very sharp curve was chosen for demonstration of rail corrugation monitoring by integrating numerical train/track simulations, axle box acceleration data obtained from the calibrated track inspection vehicle ”AK Car”, and spectral data analytics.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.20855/IJAV.2018.23.11104
Aditya Sharma, A. Amarnath, P. K. Kankar
Bearings are the most common components used in rotating machines. Their malfunction may result in costly shutdowns and human causalities which can be avoided by effective condition monitoring practices. In present study, attempt has been made to estimate the severity of defect in bearing components by a two-step process. Initially, defects of various severities in all bearing components are classified. In the next step, if defect exist in any of the bearing components, i.e. inner race, outer race, and rolling elements, level of severity of defect is estimated. Various statistical features are extracted from the raw vibration signals. Two machine learning techniques; support vector machine and artificial neural network, along with four feature ranking techniques; Chi-square, gain ratio, ReliefF and principal component analysis are used and employed for the analysis. Results show the potential of the proposed methodology in defect severity estimation and classification of rolling element bearings.
{"title":"Use of Feature Ranking Techniques for Defect Severity Estimation of Rolling Element Bearings","authors":"Aditya Sharma, A. Amarnath, P. K. Kankar","doi":"10.20855/IJAV.2018.23.11104","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.11104","url":null,"abstract":"Bearings are the most common components used in rotating machines. Their malfunction may result in costly shutdowns and human causalities which can be avoided by effective condition monitoring practices. In present study, attempt has been made to estimate the severity of defect in bearing components by a two-step process. Initially, defects of various severities in all bearing components are classified. In the next step, if defect exist in any of the bearing components, i.e. inner race, outer race, and rolling elements, level of severity of defect is estimated. Various statistical features are extracted from the raw vibration signals. Two machine learning techniques; support vector machine and artificial neural network, along with four feature ranking techniques; Chi-square, gain ratio, ReliefF and principal component analysis are used and employed for the analysis. Results show the potential of the proposed methodology in defect severity estimation and classification of rolling element bearings.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.20855/IJAV.2018.23.11109
H. Ucar, I. Basdogan
Accurate prediction of the vibration response at a point on a complex structure, where the operational behavior cannot be measured directly, is an important engineering problem for design optimization, component selection and condition monitoring. Identifying the exciting forces acting on the structure is a major step in the vibration response prediction (VRP). At the point where direct measurement is impossible or impractical due to physical constraints, a common approach is to identify the exciting forces based on multiplication of an inverted frequency response function (FRF) matrix and a vector of vibration responses measured at the points where the exciting forces are transmitted through. However, in some cases measuring FRFs are almost impossible. In other cases, where measuring is possible, they may be prone to significant errors. Furthermore, the inverted FRF matrix may be ill-conditioned due to the one or few modes that dominate the dynamics of the structure. In order to improve the force identification step and reduce the experimental challenges, previous studies focused on either conditioning methods or numerical models. However, conditioning methods result in additional measurements, and using only numerical models causes reduced accuracy due to incongruities between the simulation model and the real system. Considering these problems, a hybrid VRP methodology that incorporates the numerical modeling and experimental measurement results is proposed in this study. Creating an accurate numerical model and properly selecting the force identification points are the main requirements of the proposed methodology. A structure coupled with rubber mounts is used to demonstrate the proposed methodology. The numerical model includes hyperelastic and viscoelastic modeling of the rubber to represent the system behavior accurately. The selection of force identification points is based on a metric that is composed of the average condition number of the FRF matrix across the whole frequency of interest. The results show that the proposed hybrid methodology is superior to other alternative methods where predictions are solely based on numerical results or experimental measurements.
{"title":"Vibration Response Prediction on Rubber Mounts with a Hybrid Approach","authors":"H. Ucar, I. Basdogan","doi":"10.20855/IJAV.2018.23.11109","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.11109","url":null,"abstract":"Accurate prediction of the vibration response at a point on a complex structure, where the operational behavior cannot be measured directly, is an important engineering problem for design optimization, component selection and condition monitoring. Identifying the exciting forces acting on the structure is a major step in the vibration response prediction (VRP). At the point where direct measurement is impossible or impractical due to physical constraints, a common approach is to identify the exciting forces based on multiplication of an inverted frequency response function (FRF) matrix and a vector of vibration responses measured at the points where the exciting forces are transmitted through. However, in some cases measuring FRFs are almost impossible. In other cases, where measuring is possible, they may be prone to significant errors. Furthermore, the inverted FRF matrix may be ill-conditioned due to the one or few modes that dominate the dynamics of the structure. In order to improve the force identification step and reduce the experimental challenges, previous studies focused on either conditioning methods or numerical models. However, conditioning methods result in additional measurements, and using only numerical models causes reduced accuracy due to incongruities between the simulation model and the real system. Considering these problems, a hybrid VRP methodology that incorporates the numerical modeling and experimental measurement results is proposed in this study. Creating an accurate numerical model and properly selecting the force identification points are the main requirements of the proposed methodology. A structure coupled with rubber mounts is used to demonstrate the proposed methodology. The numerical model includes hyperelastic and viscoelastic modeling of the rubber to represent the system behavior accurately. The selection of force identification points is based on a metric that is composed of the average condition number of the FRF matrix across the whole frequency of interest. The results show that the proposed hybrid methodology is superior to other alternative methods where predictions are solely based on numerical results or experimental measurements.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.20855/IJAV.2018.23.11253
Hui Li, Haitao Luo, Wei Sun, B. Wen
This research combines theory with experiment to investigate the influence of an elastic boundary on modal parameters of a thin cylindrical shell (TCS). First, artificial stiffness method and finite element method (FEM) are employed to calculate natural frequencies and modal shapes of TCS under condition such that vibration characteristics of elastically supported shell can be roughly mastered. Then, the following measurements and identification techniques are used to get precise frequency, damping, and shape results: non-contact laser Doppler vibrometer and vibration shaker with excitation level being precisely controlled are used in the test system; “pre-experiment” is adopted to determine the required tightening torque as well as to verify whether or not the tested shell is under constraint boundary; and small-segment FFT processing technique is employed to accurately measure nature frequency, and laser rotating scanning technique is used to get shape results with high efficiency. Finally, based on the accurate measured data, the influences on natural frequencies, modal shapes, and damping ratios of TCS under elastic boundary are analysed and discussed. It can be found that an elastic boundary can significantly affect frequency and damping results, clearly reducing high order damping and decreasing natural frequencies of most modes. However, high order natural frequencies and mode shapes are still the same as the ones under the constraint condition, and the changing trend of natural frequencies with mode shapes is constant when the order of axial mode is m = 1, which agrees well with the results calculated by artificial stiffness method and FEM.
{"title":"The Influence of Elastic Boundary on Modal Parameters of Thin Cylindrical Shell","authors":"Hui Li, Haitao Luo, Wei Sun, B. Wen","doi":"10.20855/IJAV.2018.23.11253","DOIUrl":"https://doi.org/10.20855/IJAV.2018.23.11253","url":null,"abstract":"This research combines theory with experiment to investigate the influence of an elastic boundary on modal parameters of a thin cylindrical shell (TCS). First, artificial stiffness method and finite element method (FEM) are employed to calculate natural frequencies and modal shapes of TCS under condition such that vibration characteristics of elastically supported shell can be roughly mastered. Then, the following measurements and identification techniques are used to get precise frequency, damping, and shape results: non-contact laser Doppler vibrometer and vibration shaker with excitation level being precisely controlled are used in the test system; “pre-experiment” is adopted to determine the required tightening torque as well as to verify whether or not the tested shell is under constraint boundary; and small-segment FFT processing technique is employed to accurately measure nature frequency, and laser rotating scanning technique is used to get shape results with high efficiency. Finally, based on the accurate measured data, the influences on natural frequencies, modal shapes, and damping ratios of TCS under elastic boundary are analysed and discussed. It can be found that an elastic boundary can significantly affect frequency and damping results, clearly reducing high order damping and decreasing natural frequencies of most modes. However, high order natural frequencies and mode shapes are still the same as the ones under the constraint condition, and the changing trend of natural frequencies with mode shapes is constant when the order of axial mode is m = 1, which agrees well with the results calculated by artificial stiffness method and FEM.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":"23 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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