Pub Date : 2019-12-31DOI: 10.20855/ijav.2019.24.41460
Chol-Hak Kim, Myong-jin Kim, Chol-Su Ri
In this paper, we described a method of designing ultrasonic transducer which simultaneously radiates two finiteamplitude ultrasonic waves to produce the secondary waves with high directivity. For nonlinear effects, it is necessary that the frequencies of two primary waves are coincident with natural frequencies of the ultrasonic transducer. The main problem here is to predict the resonance frequencies of the first mode as well as higher modes. While the first resonance frequency of the transducer can be estimated easily, it is not trivial to do higher ones. When the length of transducer is much greater than its diameter, this problem is reduced to one-dimensional and higher mode frequencies are nothing but multiples of the first mode frequency. However, such a case is seldom encountered. Using the transfer matrix method, we obtained the resonance frequencies of the transducer analytically and compared these with numerical results from the simulation. The theoretical and simulation results are in good agreement with the difference of 3–6kHz.
{"title":"Design of Ultrasonic Transducer for Secondary Wave Generations with High Directivity","authors":"Chol-Hak Kim, Myong-jin Kim, Chol-Su Ri","doi":"10.20855/ijav.2019.24.41460","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41460","url":null,"abstract":"In this paper, we described a method of designing ultrasonic transducer which simultaneously radiates two finiteamplitude ultrasonic waves to produce the secondary waves with high directivity. For nonlinear effects, it is necessary that the frequencies of two primary waves are coincident with natural frequencies of the ultrasonic transducer. The main problem here is to predict the resonance frequencies of the first mode as well as higher modes. While the first resonance frequency of the transducer can be estimated easily, it is not trivial to do higher ones. When the length of transducer is much greater than its diameter, this problem is reduced to one-dimensional and higher mode frequencies are nothing but multiples of the first mode frequency. However, such a case is seldom encountered. Using the transfer matrix method, we obtained the resonance frequencies of the transducer analytically and compared these with numerical results from the simulation. The theoretical and simulation results are in good agreement with the difference of 3–6kHz.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46017146","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.2019.24.41363
M. Pradhan, P. Dash
The static and dynamic stability of an asymmetric rotating tapered sandwich beam subjected to pulsating axial load in temperature environment is studied under two different boundary conditions. The non-dimensional equations of motion and the boundary conditions are derived by applying Hamilton’s energy principle. A coupled Hill’s equations with complex coefficients are derived from the non-dimensional equations of motion by the application of the generalized Galerkin method. By the application of the Saito-Otomi conditions, zones of instabilities are obtained and presented graphically. For the calculation of the Young’s module for the elastic layers, the effect of temperature has been taken in to consideration by means of a uniform thermal gradient along the longitudinal axes for both the upper and lower elastic layers. The effects of the taper parameter, core loss factor, thermal gradient, rotational speed, hub radius, and core density parameter on the static buckling loads and the regions of instability are investigated.
{"title":"Static and Dynamic Stability Analysis of an Asymmetric Rotating Tapered Sandwich Beam Subjected to Pulsating Axial Load with Thermal Gradient","authors":"M. Pradhan, P. Dash","doi":"10.20855/ijav.2019.24.41363","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41363","url":null,"abstract":"The static and dynamic stability of an asymmetric rotating tapered sandwich beam subjected to pulsating axial load in temperature environment is studied under two different boundary conditions. The non-dimensional equations of motion and the boundary conditions are derived by applying Hamilton’s energy principle. A coupled Hill’s equations with complex coefficients are derived from the non-dimensional equations of motion by the application of the generalized Galerkin method. By the application of the Saito-Otomi conditions, zones of instabilities are obtained and presented graphically. For the calculation of the Young’s module for the elastic layers, the effect of temperature has been taken in to consideration by means of a uniform thermal gradient along the longitudinal axes for both the upper and lower elastic layers. The effects of the taper parameter, core loss factor, thermal gradient, rotational speed, hub radius, and core density parameter on the static buckling loads and the regions of instability are investigated.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46257613","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.2019.24.41327
Fan Yang, B. Deng
The acoustic properties of three improved hydraulic mufflers with extended necks are investigated theoretically and experimentally. The effect of length and slope of the conical tube, and the perforations on the extended tube is studied on the resonance frequency and the insertion loss. The plane wave approach is used for the constant and the variable area tubes, while Sullivan and Peat’s method is applied for the perforation tube unit. Theoretical predictions are compared with experiments for these three different hydraulic noise suppressors, which are fabricated. It is shown that the resonance frequency and the insertion loss characteristics may be controlled by the length and the slope of the conical tube and perforation porosity of the extended tube without changing the expansion chamber volume. Finally, the effect of the cross-sectional shape of the expansion chamber is investigated.
{"title":"Fluid Acoustic Properties of Improved Hydraulic Mufflers with Extended Necks","authors":"Fan Yang, B. Deng","doi":"10.20855/ijav.2019.24.41327","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41327","url":null,"abstract":"The acoustic properties of three improved hydraulic mufflers with extended necks are investigated theoretically and experimentally. The effect of length and slope of the conical tube, and the perforations on the extended tube is studied on the resonance frequency and the insertion loss. The plane wave approach is used for the constant and the variable area tubes, while Sullivan and Peat’s method is applied for the perforation tube unit. Theoretical predictions are compared with experiments for these three different hydraulic noise suppressors, which are fabricated. It is shown that the resonance frequency and the insertion loss characteristics may be controlled by the length and the slope of the conical tube and perforation porosity of the extended tube without changing the expansion chamber volume. Finally, the effect of the cross-sectional shape of the expansion chamber is investigated.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45196449","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.2019.24.41464
Guoqing An, Hong-ru Li, Baiyan Chen
Piezoelectric ceramics cracking is one of the main faults of the ultrasonic motor. According to the morphological mathematics and information entropy, a method based on multi-scale morphological gradient was proposed for ceramics fault feature extraction and degradation state identification. To solve the problem that traditional multi-scale morphology spectral (MMS) entropy cannot exactly describe the performance degradation of the piezoelectric ceramics, multi-scale morphology gradient difference (MMGD) entropy was proposed to improve the sensitivity to the fault. Furthermore, multi-scale morphology gradient singular (MMGS) entropy was presented to reduce the system noise interference to the useful fault information. The disturbance analysis of temperature, load, and noise for MMGD entropy and MMGS entropy was also given in this paper. Combining the advantages of the above two entropies, a standard degradation mode matrix was built to distinguish the degradation state via the grey correlation analysis. The analysis of actual test samples demonstrated that this method is feasible and effective to extract the fault feature and indicate the degradation of piezoelectric cracking in ultrasonic motor.
{"title":"Fault Feature Extraction and Degradation State Identification for Piezoelectric Ceramics Cracking in Ultrasonic Motor Based on Multi-Scale Morphological Gradient","authors":"Guoqing An, Hong-ru Li, Baiyan Chen","doi":"10.20855/ijav.2019.24.41464","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41464","url":null,"abstract":"Piezoelectric ceramics cracking is one of the main faults of the ultrasonic motor. According to the morphological mathematics and information entropy, a method based on multi-scale morphological gradient was proposed for ceramics fault feature extraction and degradation state identification. To solve the problem that traditional multi-scale morphology spectral (MMS) entropy cannot exactly describe the performance degradation of the piezoelectric ceramics, multi-scale morphology gradient difference (MMGD) entropy was proposed to improve the sensitivity to the fault. Furthermore, multi-scale morphology gradient singular (MMGS) entropy was presented to reduce the system noise interference to the useful fault information. The disturbance analysis of temperature, load, and noise for MMGD entropy and MMGS entropy was also given in this paper. Combining the advantages of the above two entropies, a standard degradation mode matrix was built to distinguish the degradation state via the grey correlation analysis. The analysis of actual test samples demonstrated that this method is feasible and effective to extract the fault feature and indicate the degradation of piezoelectric cracking in ultrasonic motor.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48697773","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.2019.24.41468
J. Zhao, Ning Zhi, Lü Ming
With the rapid development of the high-speed railway in China, the problems of the noise pollution induced by passing trains emerge. Theoretically, the V-shaped noise barrier is of pretty good performance of noise-reduction and load-shedding. To assess the practical aerodynamic deloading characteristics of the V-shaped noise barrier, a full-scale field test was carried out at three measuring-sections equipped with noise barriers of different heights. In order to quantify the research work, the impact strength and deloading rate were selected as indicators. The effects of train speeds, train types and barrier heights are studied. This study includes the variations of impact strength and deloading rate in vertical directions. Meanwhile, 2D numerical simulation research is conducted to analyze the experimental results from the angle of mechanism. It is observed that the aerodynamic load acting on the surface of the V-shaped noise barrier was weaker and more uniform compared with conventional barrier. The flow field distribution influenced the deloading characteristics of the V-shaped noise barrier significantly. Moreover, the load-shedding effect of V-shaped noise barrier, when CRH380AM passed by, was slightly better than CRH380A. The deloading rate improved with the increasing of the noise barrier height in general.
{"title":"Field Test Research and Numerical Simulation on Aerodynamic Deloading Characteristics of V-Shaped Noise Barrier","authors":"J. Zhao, Ning Zhi, Lü Ming","doi":"10.20855/ijav.2019.24.41468","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41468","url":null,"abstract":"With the rapid development of the high-speed railway in China, the problems of the noise pollution induced by passing trains emerge. Theoretically, the V-shaped noise barrier is of pretty good performance of noise-reduction and load-shedding. To assess the practical aerodynamic deloading characteristics of the V-shaped noise barrier, a full-scale field test was carried out at three measuring-sections equipped with noise barriers of different heights. In order to quantify the research work, the impact strength and deloading rate were selected as indicators. The effects of train speeds, train types and barrier heights are studied. This study includes the variations of impact strength and deloading rate in vertical directions. Meanwhile, 2D numerical simulation research is conducted to analyze the experimental results from the angle of mechanism. It is observed that the aerodynamic load acting on the surface of the V-shaped noise barrier was weaker and more uniform compared with conventional barrier. The flow field distribution influenced the deloading characteristics of the V-shaped noise barrier significantly. Moreover, the load-shedding effect of V-shaped noise barrier, when CRH380AM passed by, was slightly better than CRH380A. The deloading rate improved with the increasing of the noise barrier height in general.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46595045","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.2019.24.4e94
D. Borelli
The topic of ships as noise sources has been studied for decades, mainly as regards underwater sound emission and onboard noise. There are several reasons: (1) underwater noise is investigated for military purposes in terms of “acoustic signatures” — a combination of elements (mainly cavitation noise, machinery noise and hydrodynamic noise) that help identify and track a vessel or weapon, (2) short and longterm negative effects on marine fauna, in particular marine mammals and cephalopods and (3) continuous onboard noise that can have an adverse impact on human health for both passengers and crew. Considering this last reason, from a regulatory point of view, the International Convention for the Safety of Life at Sea (SOLAS) in its regulation II-1/3-12 requires ships to be compliant with the International Maritime Organization (IMO) resolution MSC.337(91) “Code on noise levels on-board ships”. This IMO resolution is nowadays mandatory for ships of 1,600 gross tonnage or more, which have to be constructed to protect workers from noise and to reduce shipboard noise.
{"title":"Maritime Airborne Noise: Ships and Harbours","authors":"D. Borelli","doi":"10.20855/ijav.2019.24.4e94","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.4e94","url":null,"abstract":"The topic of ships as noise sources has been studied for decades, mainly as regards underwater sound emission and onboard noise. There are several reasons: (1) underwater noise is investigated for military purposes in terms of “acoustic signatures” — a combination of elements (mainly cavitation noise, machinery noise and hydrodynamic noise) that help identify and track a vessel or weapon, (2) short and longterm negative effects on marine fauna, in particular marine mammals and cephalopods and (3) continuous onboard noise that can have an adverse impact on human health for both passengers and crew. Considering this last reason, from a regulatory point of view, the International Convention for the Safety of Life at Sea (SOLAS) in its regulation II-1/3-12 requires ships to be compliant with the International Maritime Organization (IMO) resolution MSC.337(91) “Code on noise levels on-board ships”. This IMO resolution is nowadays mandatory for ships of 1,600 gross tonnage or more, which have to be constructed to protect workers from noise and to reduce shipboard noise.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45700413","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.2019.24.41312
Imran Shah, E. Uddin, A. Mubashar, M. Younis, Hudair Samad, K. Choi
A three-dimensional numerical simulation of the interaction of a surface acoustic wave (SAW) with a droplet of water is carried out. The mixing produced inside the droplet due to the incident with the SAW and the droplet is investigated by undertaking a parametric study, with parameters such as frequency, drop size, and the lateral position of the droplet on the surface of the substrate. The linear relationship between the input voltage and the mixing velocity inside the droplet is obtained with variation of the input voltage of the inter-digital transducer (IDT) of the SAW device within a 10–40 V range. With the variation in frequency, the maximum mixing velocity is observed at 20 MHz and it appears to be independent of the size of the droplet. Varying the substrate material with lead zirconate titanate and lithium niobate produces better mixing. Lithium niobate is preferred due to its availability and cost-effectiveness. A drop of 600 μm diameter produces better mixing. The different velocities inside the drop and the SAW device are obtained by changing the droplet position in the lateral direction (asymmetrical position) from the centre of the substrate. Cut planes parallel and perpendicular to the SAW at the core of a half-spherical droplet are observed to visualise the mixing effects inside the droplet during the interaction. To achieve the best mixing criteria, the droplet is moved in a lateral direction. An efficient parametric design for the mixing phenomena in micro-fluidic devices is presented for point-of-care devices.
{"title":"Numerical Investigation of Surface Acoustic Wave (SAW) Interacting with a Droplet for Point-of-Care Devices","authors":"Imran Shah, E. Uddin, A. Mubashar, M. Younis, Hudair Samad, K. Choi","doi":"10.20855/ijav.2019.24.41312","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41312","url":null,"abstract":"A three-dimensional numerical simulation of the interaction of a surface acoustic wave (SAW) with a droplet of water is carried out. The mixing produced inside the droplet due to the incident with the SAW and the droplet is investigated by undertaking a parametric study, with parameters such as frequency, drop size, and the lateral position of the droplet on the surface of the substrate. The linear relationship between the input voltage and the mixing velocity inside the droplet is obtained with variation of the input voltage of the inter-digital transducer (IDT) of the SAW device within a 10–40 V range. With the variation in frequency, the maximum mixing velocity is observed at 20 MHz and it appears to be independent of the size of the droplet. Varying the substrate material with lead zirconate titanate and lithium niobate produces better mixing. Lithium niobate is preferred due to its availability and cost-effectiveness. A drop of 600 μm diameter produces better mixing. The different velocities inside the drop and the SAW device are obtained by changing the droplet position in the lateral direction (asymmetrical position) from the centre of the substrate. Cut planes parallel and perpendicular to the SAW at the core of a half-spherical droplet are observed to visualise the mixing effects inside the droplet during the interaction. To achieve the best mixing criteria, the droplet is moved in a lateral direction. An efficient parametric design for the mixing phenomena in micro-fluidic devices is presented for point-of-care devices.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46267136","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.2019.24.41446
Z. Ying, R. Hu, R. Huan
A stochastic minimax control strategy for uncertain nonlinear quasi-Hamiltonian systems with noisy observations under random excitations is proposed based on the extended Kalman filter and minimax stochastic dynamical programming principle. A structure system with smart sensors and actuators is modeled as a controlled, excited and dissipative Hamiltonian system with noisy observations. The differential equations for the uncertain nonlinear quasi-Hamiltonian system with control and observation under random excitation are given first. The estimated nonlinear stochastic control system with uncertain parameters is obtained from the uncertain quasi-Hamiltonian system with noisy observation. In this case, the optimally estimated state is determined by the observation based on the extended Kalman filter. The dual dynamical programming equation for the estimated uncertain system is then obtained based on the minimax stochastic dynamical programming principle. The worst-case disturbances are determined for bounded uncertain parameters and the optimal control law is determined for the worst case by the programming equation. The proposed minimax control strategy is applied to two uncertain nonlinear stochastic systems with controls and noisy observations. The control effectiveness for the stochastic vibration response reductions of the systems is illustrated with numerical results. The proposed minimax control strategy is applicable to general uncertain nonlinear multi-degree-of-freedom structure systems with noisy observations under random excitations.
{"title":"Stochastic Minimax Vibration Control for Uncertain Nonlinear Quasi-Hamiltonian Systems with Noisy Observations","authors":"Z. Ying, R. Hu, R. Huan","doi":"10.20855/ijav.2019.24.41446","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41446","url":null,"abstract":"A stochastic minimax control strategy for uncertain nonlinear quasi-Hamiltonian systems with noisy observations under random excitations is proposed based on the extended Kalman filter and minimax stochastic dynamical programming principle. A structure system with smart sensors and actuators is modeled as a controlled, excited and dissipative Hamiltonian system with noisy observations. The differential equations for the uncertain nonlinear quasi-Hamiltonian system with control and observation under random excitation are given first. The estimated nonlinear stochastic control system with uncertain parameters is obtained from the uncertain quasi-Hamiltonian system with noisy observation. In this case, the optimally estimated state is determined by the observation based on the extended Kalman filter. The dual dynamical programming equation for the estimated uncertain system is then obtained based on the minimax stochastic dynamical programming principle. The worst-case disturbances are determined for bounded uncertain parameters and the optimal control law is determined for the worst case by the programming equation. The proposed minimax control strategy is applied to two uncertain nonlinear stochastic systems with controls and noisy observations. The control effectiveness for the stochastic vibration response reductions of the systems is illustrated with numerical results. The proposed minimax control strategy is applicable to general uncertain nonlinear multi-degree-of-freedom structure systems with noisy observations under random excitations.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46712900","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.2019.24.41433
E. Ross, J. Panda, J. Ross, L. K. Kushner
Measurements of balloon loudness and pressure signatures are presented for a variety of balloon shapes. The loudness and recordings were made 3.2 meters from the popped balloons. The balloons were of 3 types: round, long, and extremely long (the same type that is used to make balloon animals), filled with 3 gases, and inflated to multiple sizes. The data indicates that all 3 types of latex balloons share similar peak frequencies and acoustic signatures in spite of differences in shape and diameter or length when inflated. The data also shows a correlation of loudness to the ratio of specific heats of the gas and inflated diameter of the balloons. The data does not support some of the common hypotheses of balloon popping noise generation. It appears that the sound is generated by the vibration of the balloon surface and the ruptured edge of the latex. This explanation is consistent with the current acoustic measurements and shadowgraph videos, and the hypothesis of Pätynen, et al.4
{"title":"Why Balloons Make a Loud Noise When They Pop","authors":"E. Ross, J. Panda, J. Ross, L. K. Kushner","doi":"10.20855/ijav.2019.24.41433","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41433","url":null,"abstract":"Measurements of balloon loudness and pressure signatures are presented for a variety of balloon shapes. The loudness and recordings were made 3.2 meters from the popped balloons. The balloons were of 3 types: round, long, and extremely long (the same type that is used to make balloon animals), filled with 3 gases, and inflated to multiple sizes. The data indicates that all 3 types of latex balloons share similar peak frequencies and acoustic signatures in spite of differences in shape and diameter or length when inflated. The data also shows a correlation of loudness to the ratio of specific heats of the gas and inflated diameter of the balloons. The data does not support some of the common hypotheses of balloon popping noise generation. It appears that the sound is generated by the vibration of the balloon surface and the ruptured edge of the latex. This explanation is consistent with the current acoustic measurements and shadowgraph videos, and the hypothesis of Pätynen, et al.4","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43768193","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.2019.24.41484
L. A. Montoya, E. E. Rodriguez, H. J. Zúñiga, I. Mejía
The elements of rotors have inherent characteristics as geometry and material composition, which causes natural vibrations at frequencies that, due to the rotor unbalance, may coincide with the harmonics of the shaft speed, increasing stress and the probability of fractures even in transient conditions. Therefore, in this work, a theoreticalexperimental hybrid method for calculating the natural frequencies and the mode shapes, at rest and non-supported conditions, of a turbocharger rotor is proposed. Firstly, a discrete model of low number of degrees of freedom is considered, and from an oversampled modal approach (OSMA) based on the axial oversampling, sectioning and coupling of the rotor, it is possible to use the oversampled mode shapes to increase the degrees of freedom of the system without major complications in the model. This spatial oversampling criterion is based on the NyquistShannon theorem, and it is used to reduce the error in the estimates of the natural frequencies and to get a first approximation of the mode shapes. The natural frequencies were estimated by the transfer matrix method (TMM) and finite element method (FEM) in order to compare the proposed model results with well-founded numerical methods.
{"title":"Oversampled Modal Approach of a Turbocharger Rotor from the Experimental Lateral Vibrations","authors":"L. A. Montoya, E. E. Rodriguez, H. J. Zúñiga, I. Mejía","doi":"10.20855/ijav.2019.24.41484","DOIUrl":"https://doi.org/10.20855/ijav.2019.24.41484","url":null,"abstract":"The elements of rotors have inherent characteristics as geometry and material composition, which causes natural vibrations at frequencies that, due to the rotor unbalance, may coincide with the harmonics of the shaft speed, increasing stress and the probability of fractures even in transient conditions. Therefore, in this work, a theoreticalexperimental hybrid method for calculating the natural frequencies and the mode shapes, at rest and non-supported conditions, of a turbocharger rotor is proposed. Firstly, a discrete model of low number of degrees of freedom is considered, and from an oversampled modal approach (OSMA) based on the axial oversampling, sectioning and coupling of the rotor, it is possible to use the oversampled mode shapes to increase the degrees of freedom of the system without major complications in the model. This spatial oversampling criterion is based on the NyquistShannon theorem, and it is used to reduce the error in the estimates of the natural frequencies and to get a first approximation of the mode shapes. The natural frequencies were estimated by the transfer matrix method (TMM) and finite element method (FEM) in order to compare the proposed model results with well-founded numerical methods.","PeriodicalId":49185,"journal":{"name":"International Journal of Acoustics and Vibration","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2019-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67722283","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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