Pub Date : 2023-09-11DOI: 10.1177/14613484231200856
Hua Zheng, Guanyu Fang, Shiqiang Duan, Hang Li
Blade Tip Timing Technology (BTT) is a new type of blade vibration measurement method with non-contact measurement capabilities, which is associated with high efficiency and convenience. However, due to under-sampling feature of the BTT signal, the method can only measure part of the vibration information. Therefore, various BTT spectral reconstruction algorithms have been developed based on the under-sampling feature and sparsity of the blade vibration spectrum. Because of the harsh working environment of the blades, BTT signal typically contains high-level Gaussian noise in actual measurement, which significantly reduces frequency-domain sparsity and even aliases the vibration modals, resulting in a decrease in the performance of sparse reconstruction algorithms. In this paper, a multi-sequences BTT signal noise reduction method is proposed, which is based on sparse representation to suppress Gaussian noise. Through appropriately modifying the constraint in the ℓ0 optimization problem, the method filters out the noise elements in the sparse vector of the BTT signal. Then, denoising is completed by sparse inverse transformation. Finally, a global average-based singular value decomposition dictionary learning algorithm (GA-K-SVD) is proposed to generate an over-complete sparse dictionary which is adaptable to the original signal, to increase the effectiveness of GA-K-SVD. At last, simulation and experience are carried out to verify the performance optimization effect for sparse reconstruction algorithm and the effectiveness of proposed noise reduction method.
{"title":"A novel method for noise reduction of blade tip timing signals based on sparse representation and dictionary learning","authors":"Hua Zheng, Guanyu Fang, Shiqiang Duan, Hang Li","doi":"10.1177/14613484231200856","DOIUrl":"https://doi.org/10.1177/14613484231200856","url":null,"abstract":"Blade Tip Timing Technology (BTT) is a new type of blade vibration measurement method with non-contact measurement capabilities, which is associated with high efficiency and convenience. However, due to under-sampling feature of the BTT signal, the method can only measure part of the vibration information. Therefore, various BTT spectral reconstruction algorithms have been developed based on the under-sampling feature and sparsity of the blade vibration spectrum. Because of the harsh working environment of the blades, BTT signal typically contains high-level Gaussian noise in actual measurement, which significantly reduces frequency-domain sparsity and even aliases the vibration modals, resulting in a decrease in the performance of sparse reconstruction algorithms. In this paper, a multi-sequences BTT signal noise reduction method is proposed, which is based on sparse representation to suppress Gaussian noise. Through appropriately modifying the constraint in the ℓ0 optimization problem, the method filters out the noise elements in the sparse vector of the BTT signal. Then, denoising is completed by sparse inverse transformation. Finally, a global average-based singular value decomposition dictionary learning algorithm (GA-K-SVD) is proposed to generate an over-complete sparse dictionary which is adaptable to the original signal, to increase the effectiveness of GA-K-SVD. At last, simulation and experience are carried out to verify the performance optimization effect for sparse reconstruction algorithm and the effectiveness of proposed noise reduction method.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135981402","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 : 2023-09-07DOI: 10.1177/14613484231200854
Kai Pang, Yuanhao Wang, Xinyan Li, Hongquan Sun, C. Ji
Due to the incurred damages to the combustors, large-amplitude self-sustained thermoacoustic oscillations are unwanted in many propulsion systems, such as liquid/solid rocket motors and aero-engines. To suppress these thermoacoustic oscillations efficiently, the mechanism of thermoacoustic instability needs to be clarified. Following the previous experimental work, the transitions to instability in a Rijke-type thermoacoustic system with an axially distributed heat source are studied numerically in this paper. The URANS numerical method is utilized and verified by means of a mesh sensitivity analysis. The influences of the axially distributed heater length, the heater location, and the mean flow velocity on the nonlinear dynamic behaviors of thermoacoustic oscillations are evaluated. To explore the corresponding mechanism behind these influences, the principle of acoustic energy conservation has been applied. The acoustic energy gains from the thermal-acoustic coupling are quantified via Rayleigh’s integral, and their phase differences are calculated by the cross-correlation function. The acoustic damping induced by the vortex dissipation is qualitatively analyzed by the characteristics of the flow fields in the Rijke tube. Finally, as the heater length, the heater location, or the mean flow velocity is varied, three mechanisms of the transitions to instability in a Rijke-type thermoacoustic system are identified.
{"title":"Investigation on the stability of the Rijke-type thermoacoustic system with an axially distributed heat source","authors":"Kai Pang, Yuanhao Wang, Xinyan Li, Hongquan Sun, C. Ji","doi":"10.1177/14613484231200854","DOIUrl":"https://doi.org/10.1177/14613484231200854","url":null,"abstract":"Due to the incurred damages to the combustors, large-amplitude self-sustained thermoacoustic oscillations are unwanted in many propulsion systems, such as liquid/solid rocket motors and aero-engines. To suppress these thermoacoustic oscillations efficiently, the mechanism of thermoacoustic instability needs to be clarified. Following the previous experimental work, the transitions to instability in a Rijke-type thermoacoustic system with an axially distributed heat source are studied numerically in this paper. The URANS numerical method is utilized and verified by means of a mesh sensitivity analysis. The influences of the axially distributed heater length, the heater location, and the mean flow velocity on the nonlinear dynamic behaviors of thermoacoustic oscillations are evaluated. To explore the corresponding mechanism behind these influences, the principle of acoustic energy conservation has been applied. The acoustic energy gains from the thermal-acoustic coupling are quantified via Rayleigh’s integral, and their phase differences are calculated by the cross-correlation function. The acoustic damping induced by the vortex dissipation is qualitatively analyzed by the characteristics of the flow fields in the Rijke tube. Finally, as the heater length, the heater location, or the mean flow velocity is varied, three mechanisms of the transitions to instability in a Rijke-type thermoacoustic system are identified.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88575144","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 : 2023-09-07DOI: 10.1177/14613484231198958
Nazmul Sharif, Helal Uddin Molla, Abdul Alim
In this article, a very simple modified form of the harmonic balance method is used to solve a strongly nonlinear oscillator with cubic nonlinearity and harmonic restoring force. Taylor series expansion up to third term is considered for the harmonic restoring force. The first approximate solutions of the present method pleasantly agree with the numerical solution obtained by Runge–Kutta fourth order method. Accuracy and simplicity of the present method solution is established when compared with the other method solutions. The present method can be utilized to other nonlinear oscillators.
{"title":"A simple modified harmonic balance method for strongly nonlinear oscillator with cubic non-linearity and harmonic restoring force","authors":"Nazmul Sharif, Helal Uddin Molla, Abdul Alim","doi":"10.1177/14613484231198958","DOIUrl":"https://doi.org/10.1177/14613484231198958","url":null,"abstract":"In this article, a very simple modified form of the harmonic balance method is used to solve a strongly nonlinear oscillator with cubic nonlinearity and harmonic restoring force. Taylor series expansion up to third term is considered for the harmonic restoring force. The first approximate solutions of the present method pleasantly agree with the numerical solution obtained by Runge–Kutta fourth order method. Accuracy and simplicity of the present method solution is established when compared with the other method solutions. The present method can be utilized to other nonlinear oscillators.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135047692","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 : 2023-09-01DOI: 10.1177/14613484231198969
A. Wahrhaftig, Cibele Mota Menezes, Rodrigo Oliveira da Silva Conceiçao, Iago Goncalves de Oliveira, Ozge Ozdemir
The aim of this work was to assess the capability of a hydraulic bottle jack to control vibrations and the effects of earthquakes. The first stage of the present investigation focused on determining the axial stiffness of the apparatus, in order to relate its behavior to that of a linear elastic element. To do this, uniaxial compression tests were carried out using a manually controlled servo system. In the second stage, a conceptual application based on the field of mechanical vibrations was considered. The experimental results confirmed the hypothesis of linear behavior and showed that the stiffness coefficient had distinct values of magnitude that depended on the cylinder height. Simulations were conducted in which the frequencies and the peak displacements of an idealized SDOF system subjected to earthquake excitation were adjusted based on the experimental stiffness. It was possible to conclude that the equipment analyzed here is an effective tool for controlling vibration and reducing displacement during a seismic event, and can be calibrated according to the specific conditions of operation. This is an important aspect of safety and functionality for mechanical and structural systems.
{"title":"Assessment of a hydraulic bottle jack as an effective device for controlling vibration and mitigating the effects of earthquakes","authors":"A. Wahrhaftig, Cibele Mota Menezes, Rodrigo Oliveira da Silva Conceiçao, Iago Goncalves de Oliveira, Ozge Ozdemir","doi":"10.1177/14613484231198969","DOIUrl":"https://doi.org/10.1177/14613484231198969","url":null,"abstract":"The aim of this work was to assess the capability of a hydraulic bottle jack to control vibrations and the effects of earthquakes. The first stage of the present investigation focused on determining the axial stiffness of the apparatus, in order to relate its behavior to that of a linear elastic element. To do this, uniaxial compression tests were carried out using a manually controlled servo system. In the second stage, a conceptual application based on the field of mechanical vibrations was considered. The experimental results confirmed the hypothesis of linear behavior and showed that the stiffness coefficient had distinct values of magnitude that depended on the cylinder height. Simulations were conducted in which the frequencies and the peak displacements of an idealized SDOF system subjected to earthquake excitation were adjusted based on the experimental stiffness. It was possible to conclude that the equipment analyzed here is an effective tool for controlling vibration and reducing displacement during a seismic event, and can be calibrated according to the specific conditions of operation. This is an important aspect of safety and functionality for mechanical and structural systems.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"18 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79369813","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 : 2023-08-31DOI: 10.1177/14613484231198962
Zhen Li, Qingshan Wang, Ruihua Wang, B. Qin, Weng Shao
This paper proposes a synthetical multi-degree-of-freedom mathematical modelling for analyzing the dynamic characteristics of angular contact ball bearing with waviness subjected to the external load working conditions. The above multi-degree-of-freedom mathematical modelling is established based on nonlinear elastic Hertz contact theory and inner raceway control theory by employing improved Newton–Raphson iteration method; the validation of the established mathematical modelling is verified by comparing the presented results with the existing literature results. The above mathematical modelling has considered raceway waviness, ball waviness, bearing clearance, centrifugal force, gyroscopic moment, external loads, and rotating speed comprehensively. Firstly, the effects of waviness order and waviness amplitude on time-varying contact and stiffness characteristics of angular contact ball bearing are investigated systematically. Then, the influences of bearing clearance, rotating speed, axial force, radial force, and torque on the dynamic contact and stiffness characteristics of angular contact ball bearing with waviness are analyzed thoroughly. The main results show that the solution results of mathematical modelling have converged, respectively, when raceway waviness order increases to 25 and ball waviness order increases to 5; The variation tendencies of time-varying contact angle, contact force, and stiffness of angular contact ball bearing with waviness are aperiodic; The amplitudes of time-varying contact angle, contact force, and stiffness of angular contact ball bearing increase evidently with waviness amplitude increased; The bearing clearance has important influence on the contact angle and contact force of outer raceway and inner raceway, respectively; The effects of radial force and torque on contact and stiffness characteristics are consistent basically in the corresponding direction; The influences of axial force and rotating speed on the contact and stiffness characteristics are more remarkable compared with other factors. The investigations of contact and stiffness characteristics of angular contact ball bearing with waviness are helpful for the designation and manufacture of high precision angular contact ball bearing.
{"title":"Nonlinear dynamic behaviors of angular contact ball bearing with waviness based on a synthetical multi-degree-of-freedom mathematical modelling","authors":"Zhen Li, Qingshan Wang, Ruihua Wang, B. Qin, Weng Shao","doi":"10.1177/14613484231198962","DOIUrl":"https://doi.org/10.1177/14613484231198962","url":null,"abstract":"This paper proposes a synthetical multi-degree-of-freedom mathematical modelling for analyzing the dynamic characteristics of angular contact ball bearing with waviness subjected to the external load working conditions. The above multi-degree-of-freedom mathematical modelling is established based on nonlinear elastic Hertz contact theory and inner raceway control theory by employing improved Newton–Raphson iteration method; the validation of the established mathematical modelling is verified by comparing the presented results with the existing literature results. The above mathematical modelling has considered raceway waviness, ball waviness, bearing clearance, centrifugal force, gyroscopic moment, external loads, and rotating speed comprehensively. Firstly, the effects of waviness order and waviness amplitude on time-varying contact and stiffness characteristics of angular contact ball bearing are investigated systematically. Then, the influences of bearing clearance, rotating speed, axial force, radial force, and torque on the dynamic contact and stiffness characteristics of angular contact ball bearing with waviness are analyzed thoroughly. The main results show that the solution results of mathematical modelling have converged, respectively, when raceway waviness order increases to 25 and ball waviness order increases to 5; The variation tendencies of time-varying contact angle, contact force, and stiffness of angular contact ball bearing with waviness are aperiodic; The amplitudes of time-varying contact angle, contact force, and stiffness of angular contact ball bearing increase evidently with waviness amplitude increased; The bearing clearance has important influence on the contact angle and contact force of outer raceway and inner raceway, respectively; The effects of radial force and torque on contact and stiffness characteristics are consistent basically in the corresponding direction; The influences of axial force and rotating speed on the contact and stiffness characteristics are more remarkable compared with other factors. The investigations of contact and stiffness characteristics of angular contact ball bearing with waviness are helpful for the designation and manufacture of high precision angular contact ball bearing.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"6 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89775040","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 : 2023-08-29DOI: 10.1177/14613484231190986
Jin-You Lu, Tarcisio Silva, F. Alzaabi, Rashid K. Abu Al-Rub, Dong-Wook Lee
Poly(methyl methacrylate)-based triply periodic minimal surfaces (TPMS) structures promise great potential in phononic applications, but the complicated TPMS structure induces a design challenge for controlling their properties. Numerical acoustic simulations of seven major PMMA-based TPMS lattice structures are presented for low-frequency sound attenuation applications while varying their relative density. Except for the local resonances in primitive and Neovius-based lattice structures, the acoustic properties of other TPMS structures show a common Bragg bandgap with a central frequency of around 435 Hz and a bandwidth of around 286 Hz, which results from multiple scattering of periodic unit cells. In contrast, the acoustic bandgaps of primitive and Neovius-based lattices have much smaller and larger complete bandgaps, respectively, which are mainly attributed to the local resonances in their geometric cavities with different sizes. Thus, by taking the mechanism of generated bandgaps in the TPMS-based lattice structures into consideration, we can design suitable bandgaps for acoustic applications in the specific frequency range.
{"title":"Insights into acoustic properties of seven selected triply periodic minimal surfaces-based structures: A numerical study","authors":"Jin-You Lu, Tarcisio Silva, F. Alzaabi, Rashid K. Abu Al-Rub, Dong-Wook Lee","doi":"10.1177/14613484231190986","DOIUrl":"https://doi.org/10.1177/14613484231190986","url":null,"abstract":"Poly(methyl methacrylate)-based triply periodic minimal surfaces (TPMS) structures promise great potential in phononic applications, but the complicated TPMS structure induces a design challenge for controlling their properties. Numerical acoustic simulations of seven major PMMA-based TPMS lattice structures are presented for low-frequency sound attenuation applications while varying their relative density. Except for the local resonances in primitive and Neovius-based lattice structures, the acoustic properties of other TPMS structures show a common Bragg bandgap with a central frequency of around 435 Hz and a bandwidth of around 286 Hz, which results from multiple scattering of periodic unit cells. In contrast, the acoustic bandgaps of primitive and Neovius-based lattices have much smaller and larger complete bandgaps, respectively, which are mainly attributed to the local resonances in their geometric cavities with different sizes. Thus, by taking the mechanism of generated bandgaps in the TPMS-based lattice structures into consideration, we can design suitable bandgaps for acoustic applications in the specific frequency range.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"31 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76546670","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 : 2023-08-28DOI: 10.1177/14613484231197981
Yongbin Ma, Qingfeng Cheng, Boping Wang
The classical laminate and lattice sandwich plate structure can be simplified into a multilayer plate system, wherein the plate components of the system are continuously joined along the transverse direction by elastic layers and can have different combinations of boundary conditions. A symplectic analytical wave propagation approach is developed for the forced vibration of a system of multiple elastically connected thin plates considering the Kirchhoff thin plate theory. The proposed method overcomes the limitation of the traditional analytical method, wherein the exact vibration field function only exists for a system with all edges of the plate components simply supported. First, the coupled partial differential equations governing the vibration of the multi-plate system are decoupled using a technique based on matrix theory; for decoupled equations, a general “vibration” state is innovatively introduced into the symplectic dual system. Next, the general “vibration” state can be analytically described in symplectic space by solving the symplectic eigenproblem and utilizing wave propagation theory. Finally, by using these analytical wave shapes and satisfying the physical boundary conditions of the system, the forced responses can be analytically calculated. In the numerical examples, the forced transverse vibrations of the double- and three-plate systems are investigated, and the cases with various combinations of boundary conditions are considered. The effectiveness of the present method is validated by comparing the present results with the results from the literature and those calculated using the finite element method. The influence of the elastic layer stiffness and number of plate components on the vibration is also investigated.
{"title":"Symplectic analytical solution for forced vibration of a multilayer plate system","authors":"Yongbin Ma, Qingfeng Cheng, Boping Wang","doi":"10.1177/14613484231197981","DOIUrl":"https://doi.org/10.1177/14613484231197981","url":null,"abstract":"The classical laminate and lattice sandwich plate structure can be simplified into a multilayer plate system, wherein the plate components of the system are continuously joined along the transverse direction by elastic layers and can have different combinations of boundary conditions. A symplectic analytical wave propagation approach is developed for the forced vibration of a system of multiple elastically connected thin plates considering the Kirchhoff thin plate theory. The proposed method overcomes the limitation of the traditional analytical method, wherein the exact vibration field function only exists for a system with all edges of the plate components simply supported. First, the coupled partial differential equations governing the vibration of the multi-plate system are decoupled using a technique based on matrix theory; for decoupled equations, a general “vibration” state is innovatively introduced into the symplectic dual system. Next, the general “vibration” state can be analytically described in symplectic space by solving the symplectic eigenproblem and utilizing wave propagation theory. Finally, by using these analytical wave shapes and satisfying the physical boundary conditions of the system, the forced responses can be analytically calculated. In the numerical examples, the forced transverse vibrations of the double- and three-plate systems are investigated, and the cases with various combinations of boundary conditions are considered. The effectiveness of the present method is validated by comparing the present results with the results from the literature and those calculated using the finite element method. The influence of the elastic layer stiffness and number of plate components on the vibration is also investigated.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89594750","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 : 2023-08-23DOI: 10.1177/14613484231197985
Qiao Luo, Yansong He, Zhifei Zhang, Kaizhan Gao
The vibration characteristics of car seats directly influence the ride comfort. Polyurethane foam is the key part of a seat, and its physical parameters have an important impact on the seat. In this study, the influence of the foam thickness and foam hardness on the vibration characteristics of seat cushion with different excitation magnitudes was investigated by using transmissibility and seat effective amplitude transmissibility (SEAT) value. First, vibration tests were carried out at a vertical vibration simulator with width-limited white noise vibration frequencies from 0.5 to 20 Hz with root-mean-square (r.m.s.) values of 0.4, 0.8, and 1.2 m/s2, the acceleration at the platform and the body-foam interfaces were measured to calculate the transmissibility, and the influence of the foam physical properties on the transmissibility was analyzed. Then, the SEAT value was introduced to assess the vibration isolation efficiency of the foam cushion, and the influence of the foam physical properties of the foam cushion on the vibration isolation efficiency was analyzed. With increasing thickness of the foam and decreasing hardness of the foam at the seat pan, the peak transmissibility increased and the resonance frequency decreased. The SEAT values show that increasing the foam thickness is beneficial to the improvement of the vibration isolation efficiency of the seat, but there is a diminishing return; the combination of physical parameters of low hardness and high thickness could make the vibration isolation performance of the seat better. In addition, the nonlinearity of human-seat system during different vibration magnitude was found.
{"title":"Transmission of vertical vibration through a seat cushion at the seat pan: Effect of foam physical properties during different excitation magnitudes","authors":"Qiao Luo, Yansong He, Zhifei Zhang, Kaizhan Gao","doi":"10.1177/14613484231197985","DOIUrl":"https://doi.org/10.1177/14613484231197985","url":null,"abstract":"The vibration characteristics of car seats directly influence the ride comfort. Polyurethane foam is the key part of a seat, and its physical parameters have an important impact on the seat. In this study, the influence of the foam thickness and foam hardness on the vibration characteristics of seat cushion with different excitation magnitudes was investigated by using transmissibility and seat effective amplitude transmissibility (SEAT) value. First, vibration tests were carried out at a vertical vibration simulator with width-limited white noise vibration frequencies from 0.5 to 20 Hz with root-mean-square (r.m.s.) values of 0.4, 0.8, and 1.2 m/s2, the acceleration at the platform and the body-foam interfaces were measured to calculate the transmissibility, and the influence of the foam physical properties on the transmissibility was analyzed. Then, the SEAT value was introduced to assess the vibration isolation efficiency of the foam cushion, and the influence of the foam physical properties of the foam cushion on the vibration isolation efficiency was analyzed. With increasing thickness of the foam and decreasing hardness of the foam at the seat pan, the peak transmissibility increased and the resonance frequency decreased. The SEAT values show that increasing the foam thickness is beneficial to the improvement of the vibration isolation efficiency of the seat, but there is a diminishing return; the combination of physical parameters of low hardness and high thickness could make the vibration isolation performance of the seat better. In addition, the nonlinearity of human-seat system during different vibration magnitude was found.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"45 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84629458","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}
Structural modal estimation has consistently remained one of the most crucial areas of research in mechanical vibration analysis and signal processing. It is imperative to accurately monitor the vibration signals of rotor blades and their corresponding structural modal parameters. Blade tip timing (BTT) is a promising approach used to measure vibration and monitor the health of blades. However, most existing BTT methods focus on frequency accuracy, neglecting damping, a key physical quantity that represents the strength of the structure. This research focuses on damping modal estimation of blade vibration and proposes a sparse reconstruction algorithm based on a two-dimensional Laplace wavelet family, which addresses the inherent under-sampled problem of BTT technology while enabling estimations of both the structural modal frequency and modal damping of the blades. Firstly, the proposed algorithm is achieved by designing a Laplace wavelet dictionary based on prior information and using a convex optimization objective function with a regularization term. Secondly, Laplace wavelet dictionary matches the signal better than the traditional Fourier dictionary based on the similarity between the damped vibration signal and the Laplace wavelet, then a sparser representation vector can be obtained. Moreover, the research object is not limited to a single blade, but can be easily expanded to multiple stages and multiple rotating blades monitored simultaneously. Finally, the simulation and physical test results indicate that the proposed method exhibits high reconstruction accuracy, reliability, and anti-noise abilities.
{"title":"A modal estimation method of rotating blade based on compressed sensing and blade tip timing","authors":"Hua Zheng, Guanyu Fang, Zhenglong Wu, Shiqiang Duan, Jiangtao Zhou","doi":"10.1177/14613484231196069","DOIUrl":"https://doi.org/10.1177/14613484231196069","url":null,"abstract":"Structural modal estimation has consistently remained one of the most crucial areas of research in mechanical vibration analysis and signal processing. It is imperative to accurately monitor the vibration signals of rotor blades and their corresponding structural modal parameters. Blade tip timing (BTT) is a promising approach used to measure vibration and monitor the health of blades. However, most existing BTT methods focus on frequency accuracy, neglecting damping, a key physical quantity that represents the strength of the structure. This research focuses on damping modal estimation of blade vibration and proposes a sparse reconstruction algorithm based on a two-dimensional Laplace wavelet family, which addresses the inherent under-sampled problem of BTT technology while enabling estimations of both the structural modal frequency and modal damping of the blades. Firstly, the proposed algorithm is achieved by designing a Laplace wavelet dictionary based on prior information and using a convex optimization objective function with a regularization term. Secondly, Laplace wavelet dictionary matches the signal better than the traditional Fourier dictionary based on the similarity between the damped vibration signal and the Laplace wavelet, then a sparser representation vector can be obtained. Moreover, the research object is not limited to a single blade, but can be easily expanded to multiple stages and multiple rotating blades monitored simultaneously. Finally, the simulation and physical test results indicate that the proposed method exhibits high reconstruction accuracy, reliability, and anti-noise abilities.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"75 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87286270","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 : 2023-08-20DOI: 10.1177/14613484231195267
Md Ashraful Huq, M Zahid Hasan, M. Alam
Recently, an approximation technique was presented for solving strong nonlinear oscillators modeled by second-order differential equations. Due to the arising of an algebraic complicity, the method fails to determine suitable solution of some important nonlinear problems such as quadratic oscillator, cubical Duffing oscillator of softening springs, and pendulum equation. However, suitable solutions of these oscillators are found by rearranging only an algebraic equation related to amplitude and frequency. The determination of solutions is simpler than the original version.
{"title":"An approximation technique for solving nonlinear oscillators","authors":"Md Ashraful Huq, M Zahid Hasan, M. Alam","doi":"10.1177/14613484231195267","DOIUrl":"https://doi.org/10.1177/14613484231195267","url":null,"abstract":"Recently, an approximation technique was presented for solving strong nonlinear oscillators modeled by second-order differential equations. Due to the arising of an algebraic complicity, the method fails to determine suitable solution of some important nonlinear problems such as quadratic oscillator, cubical Duffing oscillator of softening springs, and pendulum equation. However, suitable solutions of these oscillators are found by rearranging only an algebraic equation related to amplitude and frequency. The determination of solutions is simpler than the original version.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"82 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72545511","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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