Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is stron...Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.展开更多
This paper deals with the assessment of vibro-acoustic properties of a multifunctional carbon fiber reinfo rced panel manu factured by bulk infu sion,a modified resin film infusion process.The components of the epoxy ...This paper deals with the assessment of vibro-acoustic properties of a multifunctional carbon fiber reinfo rced panel manu factured by bulk infu sion,a modified resin film infusion process.The components of the epoxy resin were chosen to contrast the electrical insulating property and poor flame resistance of the epoxy resins impregnating carbon woven fabric.To confer electrical conductivity to the resin a percentage of 0.5 wt%of Multi-Wall Carbon Nanotubes(MWCNTs)was dispersed in the resin,whereas to increase flame resistance a percentage of 5 wt%of Glycidil Polyhedral Oligomeric Silsesquioxanes(GPOSS)was solubilized in the epoxy mixture.Furthermore,as hardener agents,a mixture of 4,4’-DiaminoDiphenyl Sulfone(DDS)(53.4 wt%)and Bis(3-Aminophenyl)Methyl Phosphine Oxide(BAMPO)(46.7 wt%)was used.The values of the electrical conductivity were found satisfactory enough,being4.02×10^(-2)S/m for the multifunctional resin and 1.39×10^(4)S/m for the in-plane conductivity of the panel,whereas the Limiting Oxygen Index(LOI)value of the multifunctional resin was found to increase from 27%to 36%.Considering these promising results,an experimental assessment of the vibro-acoustic properties of the manufactured multifunctional panel was also performed.The panel was tested mainly to evaluate its low-frequency vibration damping and sound insulation characteristics.The manufactured panel demonstrated an improved efficiency if compared to a baseline configuration,presenting almost the double modal damping and a gain of 10 dB on the global noise reduction.展开更多
The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the da...The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the damping material parameters,and the placement,and so on.In order to further understand the mechanism in reducing the acoustic radiation of railway wheel with layer damping treatment,in this paper,the wheel is simply modified by a full-sized circular plate.The circle plate side has stuck circumference constrained damping ridges and radial constrained damping ridges on it.Based on a hybrid finite element method-boundary element method（FEM-BEM）,the paper develops a vibro-acoustic radiation model for such a distributed constrained damping structure.The vibration and acoustic radiation of the circular plate is analyzed.In the analysis,the dynamic response of the system is obtained by using the 3D finite model superposition method.The obtained vibration response is used as the initial boundary condition in solving Helmholtz boundary integral equation for the sound radiation analysis.In the procedure,firstly,the modal analysis of the circular plate is performed to get the distribution of the system modal strain energy.Secondly,the vibro-acoustic radiation characteristics of the plate with different kinds of circumference damping ridges and radial damping ridges are compared in order to try to find the best effective damping ridge structure.Thirdly,using the distribution of the plate modal strain energy investigates the effect of the ridge distribution locations on the circular plate on its vibro-acoustic radiation.The calculation and analysis research results show that,the sticking circumference and radial damping ridges on the plate can control the vibro-acoustic radiation of the plate effectively in different frequency range.The distribution of the constrained damping ridge has an effect on reduction in vibro-acoustic radiation of the circular plate.The present research is very useful in the design of r展开更多
The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequen...The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequency mod- elling techniques in general. With the common purpose to predict mid-frequency vibro-acoustic responses of stiffened panel structures to an acceptable accuracy at a reasonable computational cost, relevant techniques are mainly based on one of the following three types of mid-frequency vibro- acoustic modelling principles： （1） enhanced deterministic methods, （2） enhanced statistical methods, and （3） hybrid deterministic/statistical methods. It is shown that, although recent developments have led to a significant step forward in industrial applicability, mature and adequate prediction tech- niques, however, are still very much required for solving sound transmission through, and radiation from, extruded aluminium panels used on high-speed trains. Due to their great potentials for predicting mid-frequency vibro-acoustics of stiffened panel structures, two of recently developed mid-frequency modelling approaches, i.e. the so-called hybrid finite element-statistical energy analysis （FE-SEA） and hybrid wave-based method- statistical energy analysis （WBM-SEA）, are then recapitulated.展开更多
The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acou...The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acoustic signal pattern and joint strength during friction stir welding(FSW)between AA6061-T6 and AA7075-T651 alloys.The eccentric tool pins were observed to provide good flowability and intermixing between dissimilar metals,increased the size of stir zone,and the grains in stir zone were sufficiently finer with eccentric tool pin than concentric pin.The magnitude of vibro-acoustic signal increased when shoulder plunging started and drop in signal was noted when the tool shoulder reached its desired depth.The signal magnitude was noted to be higher in welding stage compared to tool plunging stage as the tool took in fresh material during tool movement along the weld path.Preheating the workpiece prior to pin plunging and during welding notably influenced the flow behavior and mixing pattern,and the grains in stir zone were slightly coarser than those in specimen without preheating.Significant reduction in the magnitude of the signal was also observed after preheating.Tensile and flexural strength of joints were also improved slightly when additional heating was employed.展开更多
This paper presents a new method for measuring the cabin noise of a structure in a wind tunnel. A method for scaling the cabin sound was derived to obtain the cabin noise of a structure,and the derivation of the scali...This paper presents a new method for measuring the cabin noise of a structure in a wind tunnel. A method for scaling the cabin sound was derived to obtain the cabin noise of a structure,and the derivation of the scaling procedure was based on a theoretical hypothesis regarding the cabin noise prediction for a scaled model in a wind tunnel. A frequency offset was generated because of the error introduced by model manufacture and installation, and a proposed modal test method was used to eliminate the frequency offset. Both a full-scale structure and scaled structure were measured in the wind tunnel tests. The cabin noise of the full-scale model was compared with the results obtained using the scaling procedure based on the scaled model. The comparisons of the measurement results indicate that the scaling procedures developed in this paper are effective for vibro-acoustic predictions in wind tunnels. Moreover, background noise tended to affect the results of the cabin sound for the wind tunnel test, and thus background noise should be prevented through specific design efforts.展开更多
Owning to good mechanical properties,steel–concrete composite(SCC)and prestressed concrete(PC)box girders are the types of elevated structures used most in urban rail transit.However,their vibro-acoustic differences ...Owning to good mechanical properties,steel–concrete composite(SCC)and prestressed concrete(PC)box girders are the types of elevated structures used most in urban rail transit.However,their vibro-acoustic differences are yet to be explored in depth,while structure-radiated noise is becoming a main concern in noise-sensitive environments.In this work,numerical simulation is used to investigate the vibration and noise characteristics of both types of box girders induced by running trains,and the numerical procedure is verified with data measured from a PC box girder.The mechanism of vibration transmission and vibro-acoustic comparisons between SCC and PC box girders are investigated in detail,revealing that more vibration and noise arise from SCC box girders.The vibration differences between them are around 7.7 dB(A)at the bottom plate,19.3 dB(A)at the web,and 6.7 dB(A)at the flange,while for structure-radiated noise,the difference is around 5.9 dB(A).Then,potential vibroacoustic control strategies for SCC box girders are discussed.As the vibro-acoustic responses of two types of girders are dominated by the force transmitted to the bridge deck,track isolation is better than structural enhancement.It is shown that using a floating track slab can make the vibration and noise of an SCC box girder lower than those of a PC box girder.However,structural enhancement for the SCC box girder is extremely limited in effects.The six proposed structural enhancement measures reduce vibration by only 1.1–3.6 dB(A) and noise by up to1.5 dB(A).展开更多
Recently,cylindrical structures have been exploited in various fields due to their excellent mechanical properties.With the increase in the application of cylindrical shell structures,researchers are paying more and m...Recently,cylindrical structures have been exploited in various fields due to their excellent mechanical properties.With the increase in the application of cylindrical shell structures,researchers are paying more and more attention to its acoustic performance and sound insulation applications.By inserting the pyramidal truss lattice into the cylindrical shell structure,a cylindrical sandwich structure is obtained and the sound insulation performance of the structure is investigated.The space-harmonic expansion method and the principle of virtual work are employed to establish a theoretical model for the acoustic analysis of cylindrical sandwich structures.The vibro-acoustic coupling is taken into account by imposing the velocity continuity condition at the fluid-solid interface.The sound transmission loss(STL)performance of the structure is examined by establishing both theoretical and finite element models.Subsequently,the influence of various parameters on sound transmission loss is researched and analyzed.展开更多
Tissue elasticity and viscosity are always associated with pathological changes.As a new imaging method,ultrasound vibro-acoustic imaging is developed for quantitatively measuring tissue elasticity and viscosity which...Tissue elasticity and viscosity are always associated with pathological changes.As a new imaging method,ultrasound vibro-acoustic imaging is developed for quantitatively measuring tissue elasticity and viscosity which have important significance in early diagnosis of cancer.This paper developed an ultrasound vibro-acoustic imaging research platform mainly consisting of excitation part and detection part.The excitation transducer was focused at one location within the medium to generate harmonic vibration and shear wave propagation,and the detection transducer was applied to detect shear wave at other locations along shear wave propagation path using pulse-echo method.The received echoes were amplified,filtered,digitized and then processed by Kalman filter to estimate the vibration phase.According to the phase changes between different propagation locations,we estimated the shear wave speed,and then used it to calculate the tissue elasticity and viscosity.Preliminary phantom experiments based on this platform show results of phantom elasticity and viscosity close to literature values.Upcoming experiments are now in progress to obtain quantitative elasticity and viscosity in vitro tissue.展开更多
文摘Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.
文摘This paper deals with the assessment of vibro-acoustic properties of a multifunctional carbon fiber reinfo rced panel manu factured by bulk infu sion,a modified resin film infusion process.The components of the epoxy resin were chosen to contrast the electrical insulating property and poor flame resistance of the epoxy resins impregnating carbon woven fabric.To confer electrical conductivity to the resin a percentage of 0.5 wt%of Multi-Wall Carbon Nanotubes(MWCNTs)was dispersed in the resin,whereas to increase flame resistance a percentage of 5 wt%of Glycidil Polyhedral Oligomeric Silsesquioxanes(GPOSS)was solubilized in the epoxy mixture.Furthermore,as hardener agents,a mixture of 4,4’-DiaminoDiphenyl Sulfone(DDS)(53.4 wt%)and Bis(3-Aminophenyl)Methyl Phosphine Oxide(BAMPO)(46.7 wt%)was used.The values of the electrical conductivity were found satisfactory enough,being4.02×10^(-2)S/m for the multifunctional resin and 1.39×10^(4)S/m for the in-plane conductivity of the panel,whereas the Limiting Oxygen Index(LOI)value of the multifunctional resin was found to increase from 27%to 36%.Considering these promising results,an experimental assessment of the vibro-acoustic properties of the manufactured multifunctional panel was also performed.The panel was tested mainly to evaluate its low-frequency vibration damping and sound insulation characteristics.The manufactured panel demonstrated an improved efficiency if compared to a baseline configuration,presenting almost the double modal damping and a gain of 10 dB on the global noise reduction.
基金supported by National Natural Science Foundation of China (Grant No. 50821063)Technological Research and Development Programs of Railway Ministry of China (Grant No. 2008J001-A,Grant No. 2009J001)Natural Science Foundation of State Key Laboratory of Traction Power,China (Grant No. 2008TPL-Z07)
文摘The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the damping material parameters,and the placement,and so on.In order to further understand the mechanism in reducing the acoustic radiation of railway wheel with layer damping treatment,in this paper,the wheel is simply modified by a full-sized circular plate.The circle plate side has stuck circumference constrained damping ridges and radial constrained damping ridges on it.Based on a hybrid finite element method-boundary element method（FEM-BEM）,the paper develops a vibro-acoustic radiation model for such a distributed constrained damping structure.The vibration and acoustic radiation of the circular plate is analyzed.In the analysis,the dynamic response of the system is obtained by using the 3D finite model superposition method.The obtained vibration response is used as the initial boundary condition in solving Helmholtz boundary integral equation for the sound radiation analysis.In the procedure,firstly,the modal analysis of the circular plate is performed to get the distribution of the system modal strain energy.Secondly,the vibro-acoustic radiation characteristics of the plate with different kinds of circumference damping ridges and radial damping ridges are compared in order to try to find the best effective damping ridge structure.Thirdly,using the distribution of the plate modal strain energy investigates the effect of the ridge distribution locations on the circular plate on its vibro-acoustic radiation.The calculation and analysis research results show that,the sticking circumference and radial damping ridges on the plate can control the vibro-acoustic radiation of the plate effectively in different frequency range.The distribution of the constrained damping ridge has an effect on reduction in vibro-acoustic radiation of the circular plate.The present research is very useful in the design of r
基金sponsored by the NationalNatural foundation of China(Grant Nos.U1434201 and 51175300)
文摘The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequency mod- elling techniques in general. With the common purpose to predict mid-frequency vibro-acoustic responses of stiffened panel structures to an acceptable accuracy at a reasonable computational cost, relevant techniques are mainly based on one of the following three types of mid-frequency vibro- acoustic modelling principles： （1） enhanced deterministic methods, （2） enhanced statistical methods, and （3） hybrid deterministic/statistical methods. It is shown that, although recent developments have led to a significant step forward in industrial applicability, mature and adequate prediction tech- niques, however, are still very much required for solving sound transmission through, and radiation from, extruded aluminium panels used on high-speed trains. Due to their great potentials for predicting mid-frequency vibro-acoustics of stiffened panel structures, two of recently developed mid-frequency modelling approaches, i.e. the so-called hybrid finite element-statistical energy analysis （FE-SEA） and hybrid wave-based method- statistical energy analysis （WBM-SEA）, are then recapitulated.
基金the financial support received from Science and Engineering Research Board (SERB) of DST, New Delhi, India, for the present work (project number: YSS/2015/000085)
文摘The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acoustic signal pattern and joint strength during friction stir welding(FSW)between AA6061-T6 and AA7075-T651 alloys.The eccentric tool pins were observed to provide good flowability and intermixing between dissimilar metals,increased the size of stir zone,and the grains in stir zone were sufficiently finer with eccentric tool pin than concentric pin.The magnitude of vibro-acoustic signal increased when shoulder plunging started and drop in signal was noted when the tool shoulder reached its desired depth.The signal magnitude was noted to be higher in welding stage compared to tool plunging stage as the tool took in fresh material during tool movement along the weld path.Preheating the workpiece prior to pin plunging and during welding notably influenced the flow behavior and mixing pattern,and the grains in stir zone were slightly coarser than those in specimen without preheating.Significant reduction in the magnitude of the signal was also observed after preheating.Tensile and flexural strength of joints were also improved slightly when additional heating was employed.
文摘This paper presents a new method for measuring the cabin noise of a structure in a wind tunnel. A method for scaling the cabin sound was derived to obtain the cabin noise of a structure,and the derivation of the scaling procedure was based on a theoretical hypothesis regarding the cabin noise prediction for a scaled model in a wind tunnel. A frequency offset was generated because of the error introduced by model manufacture and installation, and a proposed modal test method was used to eliminate the frequency offset. Both a full-scale structure and scaled structure were measured in the wind tunnel tests. The cabin noise of the full-scale model was compared with the results obtained using the scaling procedure based on the scaled model. The comparisons of the measurement results indicate that the scaling procedures developed in this paper are effective for vibro-acoustic predictions in wind tunnels. Moreover, background noise tended to affect the results of the cabin sound for the wind tunnel test, and thus background noise should be prevented through specific design efforts.
基金This study was supported by the National Natural Science Foundation of China(Nos.51778534 and 51978580).
文摘Owning to good mechanical properties,steel–concrete composite(SCC)and prestressed concrete(PC)box girders are the types of elevated structures used most in urban rail transit.However,their vibro-acoustic differences are yet to be explored in depth,while structure-radiated noise is becoming a main concern in noise-sensitive environments.In this work,numerical simulation is used to investigate the vibration and noise characteristics of both types of box girders induced by running trains,and the numerical procedure is verified with data measured from a PC box girder.The mechanism of vibration transmission and vibro-acoustic comparisons between SCC and PC box girders are investigated in detail,revealing that more vibration and noise arise from SCC box girders.The vibration differences between them are around 7.7 dB(A)at the bottom plate,19.3 dB(A)at the web,and 6.7 dB(A)at the flange,while for structure-radiated noise,the difference is around 5.9 dB(A).Then,potential vibroacoustic control strategies for SCC box girders are discussed.As the vibro-acoustic responses of two types of girders are dominated by the force transmitted to the bridge deck,track isolation is better than structural enhancement.It is shown that using a floating track slab can make the vibration and noise of an SCC box girder lower than those of a PC box girder.However,structural enhancement for the SCC box girder is extremely limited in effects.The six proposed structural enhancement measures reduce vibration by only 1.1–3.6 dB(A) and noise by up to1.5 dB(A).
基金The authors gratefully acknowledge the financial support from National Nature Science Foundation of China under Grant No.12072092.
文摘Recently,cylindrical structures have been exploited in various fields due to their excellent mechanical properties.With the increase in the application of cylindrical shell structures,researchers are paying more and more attention to its acoustic performance and sound insulation applications.By inserting the pyramidal truss lattice into the cylindrical shell structure,a cylindrical sandwich structure is obtained and the sound insulation performance of the structure is investigated.The space-harmonic expansion method and the principle of virtual work are employed to establish a theoretical model for the acoustic analysis of cylindrical sandwich structures.The vibro-acoustic coupling is taken into account by imposing the velocity continuity condition at the fluid-solid interface.The sound transmission loss(STL)performance of the structure is examined by establishing both theoretical and finite element models.Subsequently,the influence of various parameters on sound transmission loss is researched and analyzed.
基金This work was supported by the National Natural Science Foundation of China(Grant No.81000637)the Key Program of National Natural Science Foundation of China(Grant No.61031003)Shenzhen-HK innovative circle project(Grant No.ZYB200907090125A).
文摘Tissue elasticity and viscosity are always associated with pathological changes.As a new imaging method,ultrasound vibro-acoustic imaging is developed for quantitatively measuring tissue elasticity and viscosity which have important significance in early diagnosis of cancer.This paper developed an ultrasound vibro-acoustic imaging research platform mainly consisting of excitation part and detection part.The excitation transducer was focused at one location within the medium to generate harmonic vibration and shear wave propagation,and the detection transducer was applied to detect shear wave at other locations along shear wave propagation path using pulse-echo method.The received echoes were amplified,filtered,digitized and then processed by Kalman filter to estimate the vibration phase.According to the phase changes between different propagation locations,we estimated the shear wave speed,and then used it to calculate the tissue elasticity and viscosity.Preliminary phantom experiments based on this platform show results of phantom elasticity and viscosity close to literature values.Upcoming experiments are now in progress to obtain quantitative elasticity and viscosity in vitro tissue.
