The study of wave propagation in biomimetic porous scaffold requires the inclusion of some complex physics such as the interaction of the ultrasonic wave with pore fluid, solid phase, and porous material. Also, due to viscous interactions between the pore fluid and skeletal frame, the dynamic tortuosity as a fractional function of frequency in the clinically relevant ultrasound frequency range is considered. The bone scaffold here is simulated using a porous slab whose two dimensions are infinite. The Biot-JKD theory used for wave propagation in porous media is conditioned with many physical parameters. Solving such governing equations for complex multi-physics problems is computationally expensive. Therefore, developing efficient tools and numerical methods to address multi-physics problems is appealing. Artificial Neural Network (ANN) can efficiently solve convoluted-parametric problems. The purpose of this research is to propose a physics-aware ANN to simulate wave propagation in bone scaffold filled with a viscous fluid. A set of data including porosity, viscosity, tortuosity, viscous characteristics length, Poisson’s ratio, and elastic modulus which are sensitive to the transmission and reflection signals are applied to the ANN as inputs and the reflection and transmission signals are obtained as outputs. The reflected and transmitted waves for different porosities are considered and the results show an excellent agreement with the proposed analytical theory and experimental data found in the literature.
{"title":"Simulation of Wave Propagation in Biomimetic Porous Scaffold Using Artificial Neural Network","authors":"M. Hodaei, P. Maghoul","doi":"10.1115/imece2021-74492","DOIUrl":"https://doi.org/10.1115/imece2021-74492","url":null,"abstract":"\u0000 The study of wave propagation in biomimetic porous scaffold requires the inclusion of some complex physics such as the interaction of the ultrasonic wave with pore fluid, solid phase, and porous material. Also, due to viscous interactions between the pore fluid and skeletal frame, the dynamic tortuosity as a fractional function of frequency in the clinically relevant ultrasound frequency range is considered. The bone scaffold here is simulated using a porous slab whose two dimensions are infinite. The Biot-JKD theory used for wave propagation in porous media is conditioned with many physical parameters. Solving such governing equations for complex multi-physics problems is computationally expensive. Therefore, developing efficient tools and numerical methods to address multi-physics problems is appealing. Artificial Neural Network (ANN) can efficiently solve convoluted-parametric problems. The purpose of this research is to propose a physics-aware ANN to simulate wave propagation in bone scaffold filled with a viscous fluid. A set of data including porosity, viscosity, tortuosity, viscous characteristics length, Poisson’s ratio, and elastic modulus which are sensitive to the transmission and reflection signals are applied to the ANN as inputs and the reflection and transmission signals are obtained as outputs. The reflected and transmitted waves for different porosities are considered and the results show an excellent agreement with the proposed analytical theory and experimental data found in the literature.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81704058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adaptive mode decomposition (AMD) methods have received significant interest in recent years as an effective means for analyzing signals of multi-components and high complexity. This paper investigates the feasibility of integrating AMD methods and modal response extraction, and performs a comparative study of few representative AMD methods including the empirical mode decomposition (EMD), local mean decomposition (LMD), empirical wavelet transform (EWT), variational mode decomposition (VMD), nonlinear mode decomposition (NMD), and adaptive local iterative filtering (ALIF) methods. The fusion of AMD and modal analysis adds adaptivity and flexibility into data processing and helps automate the modal analysis process. The comparative study will provide insights on the advantages and disadvantages of the AMD methods as to the application of modal analysis. In this comparative study, the six representative AMD methods are first applied to the free response of a simulated three-degree-of-freedom (3-DOF) system, to extract the modal responses associated with the three modes. After that, the methods are applied to a measured free-response signal of a polymethyl methacrylate (PMMA) beam to assess their capability of analyzing real signals. Finally, the findings are summarized and conclusions are drawn.
{"title":"A Comparative Study of Adaptive Mode Decomposition Methods for Modal Response Extraction","authors":"Yabin Liao, M. Sensmeier","doi":"10.1115/imece2021-68378","DOIUrl":"https://doi.org/10.1115/imece2021-68378","url":null,"abstract":"\u0000 Adaptive mode decomposition (AMD) methods have received significant interest in recent years as an effective means for analyzing signals of multi-components and high complexity. This paper investigates the feasibility of integrating AMD methods and modal response extraction, and performs a comparative study of few representative AMD methods including the empirical mode decomposition (EMD), local mean decomposition (LMD), empirical wavelet transform (EWT), variational mode decomposition (VMD), nonlinear mode decomposition (NMD), and adaptive local iterative filtering (ALIF) methods. The fusion of AMD and modal analysis adds adaptivity and flexibility into data processing and helps automate the modal analysis process. The comparative study will provide insights on the advantages and disadvantages of the AMD methods as to the application of modal analysis. In this comparative study, the six representative AMD methods are first applied to the free response of a simulated three-degree-of-freedom (3-DOF) system, to extract the modal responses associated with the three modes. After that, the methods are applied to a measured free-response signal of a polymethyl methacrylate (PMMA) beam to assess their capability of analyzing real signals. Finally, the findings are summarized and conclusions are drawn.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83102970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, a nonlinear ultrasonic modulation method is developed to detect early fatigue damage in aluminum alloy structures. Seven aluminum alloy specimens with different fatigue damage degrees are prepared by fatigue test. An experimental system is designed for performing nonlinear ultrasound modulation detection of fatigue damage in aluminum alloy specimens. A single piezoceramic transducer is used to emit two superposed sinusoidal waves with different ultrasonic frequencies. The higher frequency is chosen as a non-integer multiple of the lower frequency so as to be distinguished from super-harmonic responses. The dependencies of the nonlinear modulation response on the frequency and amplitude of excitation signals are explored to select appropriate signal excitation parameters. A nonlinear modulation index (NMI) is defined as the amplitude ratio of modulation responses and linear responses, which is used to evaluate fatigue damage of specimens. Experimental results indicate that the NMI increases monotonically with the degree of fatigue damage, and it can be used to quantify the accumulation of fatigue damage in specimens. The proposed nonlinear ultrasound modulation method facilitates the detection of fatigue damage and further assessment of the severity of the damage in aluminum alloy structures.
{"title":"Detection of Fatigue Damage in Aluminum Alloy Structures Using Nonlinear Ultrasonic Modulation","authors":"Ling Yan, Lijia Luo, Fengping Zhong, Zuming Zhao, Jingjing Fan, Liuyi Huang, Shiyi Bao, Jianfeng Mao","doi":"10.1115/imece2021-73423","DOIUrl":"https://doi.org/10.1115/imece2021-73423","url":null,"abstract":"\u0000 In this paper, a nonlinear ultrasonic modulation method is developed to detect early fatigue damage in aluminum alloy structures. Seven aluminum alloy specimens with different fatigue damage degrees are prepared by fatigue test. An experimental system is designed for performing nonlinear ultrasound modulation detection of fatigue damage in aluminum alloy specimens. A single piezoceramic transducer is used to emit two superposed sinusoidal waves with different ultrasonic frequencies. The higher frequency is chosen as a non-integer multiple of the lower frequency so as to be distinguished from super-harmonic responses. The dependencies of the nonlinear modulation response on the frequency and amplitude of excitation signals are explored to select appropriate signal excitation parameters. A nonlinear modulation index (NMI) is defined as the amplitude ratio of modulation responses and linear responses, which is used to evaluate fatigue damage of specimens. Experimental results indicate that the NMI increases monotonically with the degree of fatigue damage, and it can be used to quantify the accumulation of fatigue damage in specimens. The proposed nonlinear ultrasound modulation method facilitates the detection of fatigue damage and further assessment of the severity of the damage in aluminum alloy structures.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90196426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The free-fall absolute gravimeter is commonly used for precise gravitational acceleration measurement. The g value is obtained through quadratic fitting of the position-time data pairs of the freely falling test mass. However, recoil vibrations are generated during the release of the test mass resulting from the movement of the center of mass of the chamber, and errors may arise from these vibrations in the measurement process. To solve the recoil vibration problem, previous researchers have developed the recoil compensation structure to achieve a basically stationary center of mass during the drop. In this paper, counterweights of a variety of masses are tested on our recoil compensated gravimeter, while recoil vibrations are recorded and analyzed accordingly. The multibody simulation indicates that compensated counterweights can significantly reduce the recoil vibration amplitude, making a more precise measurement attainable. In the experiments, accelerometers and seismometers are employed respectively in the simultaneous measurement of recoil vibrations of dropping chamber and reflector. Then all the vibration signals are analyzed and compared, and the outcome confirms the effectiveness of the gravimeter in performing high precision measurement as what is observed in the previous simulations. With a proper design of the counterweight mass, the recoil effect can be significantly reduced during the test procedure, which indicates a potential for high precision measurement.
{"title":"Analysis and Optimization of the Recoil-Compensated Absolute Gravimeter","authors":"Yicong Chen, K. Wu, Yi Wen, Lijun Wang","doi":"10.1115/imece2021-68659","DOIUrl":"https://doi.org/10.1115/imece2021-68659","url":null,"abstract":"\u0000 The free-fall absolute gravimeter is commonly used for precise gravitational acceleration measurement. The g value is obtained through quadratic fitting of the position-time data pairs of the freely falling test mass. However, recoil vibrations are generated during the release of the test mass resulting from the movement of the center of mass of the chamber, and errors may arise from these vibrations in the measurement process. To solve the recoil vibration problem, previous researchers have developed the recoil compensation structure to achieve a basically stationary center of mass during the drop. In this paper, counterweights of a variety of masses are tested on our recoil compensated gravimeter, while recoil vibrations are recorded and analyzed accordingly. The multibody simulation indicates that compensated counterweights can significantly reduce the recoil vibration amplitude, making a more precise measurement attainable. In the experiments, accelerometers and seismometers are employed respectively in the simultaneous measurement of recoil vibrations of dropping chamber and reflector. Then all the vibration signals are analyzed and compared, and the outcome confirms the effectiveness of the gravimeter in performing high precision measurement as what is observed in the previous simulations. With a proper design of the counterweight mass, the recoil effect can be significantly reduced during the test procedure, which indicates a potential for high precision measurement.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73777154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Power flow between source and passive receiver structures is a common metric for characterizing the dynamics of coupled structures. The objective is generally to reduce the amount of power flow between the structures by means of structural modifications, insofar as to reduce the overall levels of vibration of the coupled system. As such, the sensitivity of power flow to changes in inertial, elastic, and dissipative properties of the structure is quantified. It is shown that power flow into a receiver is not always directly proportional to the amount of damping in the receiver, but is also dependent on the amount of damping present in the source at a given frequency. The sign of the sensitivity can provide information as to when a change in damping will increase or decrease power flow; positive indicates an increase in power flow, negative indicates a decrease. A similar analysis is performed on modifications made to a structure’s mass and stiffness properties. Relationships between power flow and power flow sensitivity are shown for a simple single degree of freedom source-receiver coupling, and is extended to a multi-degree of freedom coupling between two beam structures.
{"title":"Structure-Borne Power Flow Sensitivity Analysis for General Structural Modifications","authors":"J. Young, Kyle R. Myers","doi":"10.1115/imece2021-73731","DOIUrl":"https://doi.org/10.1115/imece2021-73731","url":null,"abstract":"\u0000 Power flow between source and passive receiver structures is a common metric for characterizing the dynamics of coupled structures. The objective is generally to reduce the amount of power flow between the structures by means of structural modifications, insofar as to reduce the overall levels of vibration of the coupled system. As such, the sensitivity of power flow to changes in inertial, elastic, and dissipative properties of the structure is quantified. It is shown that power flow into a receiver is not always directly proportional to the amount of damping in the receiver, but is also dependent on the amount of damping present in the source at a given frequency. The sign of the sensitivity can provide information as to when a change in damping will increase or decrease power flow; positive indicates an increase in power flow, negative indicates a decrease. A similar analysis is performed on modifications made to a structure’s mass and stiffness properties. Relationships between power flow and power flow sensitivity are shown for a simple single degree of freedom source-receiver coupling, and is extended to a multi-degree of freedom coupling between two beam structures.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"257 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76184986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A dual-purpose metamaterial structure that can concurrently suppress vibrations and scavenge energy is presented. The metamaterial assembly presented in this work uses a permanent magnet-coil system in addition to an elastic cantilever beam to perform its dual functions. A prototype is manufactured and a COMSOL model is developed. Two bandgaps are observed at 205–257 Hz and 587–639 Hz. COMSOL simulations show excellent agreement with measured data. Within these bandgaps the structure blocks vibrations from traveling through and, simultaneously, converts vibrations into electric power. The first bandgap has a vibration attenuation level larger than the attenuation level observed in the second bandgap. Mode shapes reveal that the local resonators experience larger deformations in the first bandgap than in the second bandgap and the vibrational energy is mostly contained within the first bandgap where the resonant frequency occurs, i.e., 224 Hz. The ability of the metamaterial assembly to scavenge these vibrations while simultaneously suppressing them is demonstrated. At an optimum load resistance of 15 Ω, within the first bandgap, approximately 2.5 μW was generated, while 0.6 nW was measured within the second bandgap. At optimum load resistance, measurements show maximum electric power reaching 5.2 μW within the first bandgap.
{"title":"Concurrent Passive Broadband Vibration Suppression and Energy Harvesting Using a Dual-Purpose Magnetoelastic Metamaterial Structure: Experimental Validation and Modeling","authors":"Winner Anigbogu, H. Bardaweel","doi":"10.1115/imece2021-67652","DOIUrl":"https://doi.org/10.1115/imece2021-67652","url":null,"abstract":"\u0000 A dual-purpose metamaterial structure that can concurrently suppress vibrations and scavenge energy is presented. The metamaterial assembly presented in this work uses a permanent magnet-coil system in addition to an elastic cantilever beam to perform its dual functions. A prototype is manufactured and a COMSOL model is developed. Two bandgaps are observed at 205–257 Hz and 587–639 Hz. COMSOL simulations show excellent agreement with measured data. Within these bandgaps the structure blocks vibrations from traveling through and, simultaneously, converts vibrations into electric power. The first bandgap has a vibration attenuation level larger than the attenuation level observed in the second bandgap. Mode shapes reveal that the local resonators experience larger deformations in the first bandgap than in the second bandgap and the vibrational energy is mostly contained within the first bandgap where the resonant frequency occurs, i.e., 224 Hz. The ability of the metamaterial assembly to scavenge these vibrations while simultaneously suppressing them is demonstrated. At an optimum load resistance of 15 Ω, within the first bandgap, approximately 2.5 μW was generated, while 0.6 nW was measured within the second bandgap. At optimum load resistance, measurements show maximum electric power reaching 5.2 μW within the first bandgap.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83654574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Viscoelastic (VE) tuned mass dampers (TMDs) using commercially available, small thickness, VE material have been used extensively in adding targeted damping to light structures. The most common approach for realizing stiffness and damping in these tuned devices has been applying VE material to strips of elastic material (mainly metal, e.g. steel) in an unconstrained or constrained layer fashion and using such assemblies, which can be viewed as a damped leaf-springs, for the suspension element of the tuned mass damper. In this work, the suitability of tuned mass dampers with visco-elastically damped leaf-spring suspension for treating large, massive civil engineering structures, more specifically floor systems, was studied numerically and experimentally. The effectiveness of this tuned mass damper configuration turned out to be disappointing. In parallel to the above-mentioned study, an alternative VE suspension was devised by stacking a number of 25 mm (1 inch) thick VE rings interlaced with the same number of metal constraining ring layers. By changing the number of these rings, different stiffness’s are realized and thus different tuning frequencies are achieved. The material properties of the VE polymer used in both studies are defined in terms of Prony series parameters. Viewing the Prony series parameters as optimization variables, they are recovered by minimizing the mean squared error between the dynamic material properties predicted by the Prony series parameters and the frequency-dependent dynamic material properties provided by the manufacturer. Using the material properties of the VE material, the dynamic finite element model of a 100 lb TMD was constructed and its tuned damping effectiveness demonstrated, numerically. The 100 lb TMD was also built and used to a) verify the numerical model and b) experimentally demonstrate the performance of the TMD.
{"title":"A Viscoelastic Tuned Mass Damper for Vibration Treatment of Large Structures","authors":"W. S. Al-Rumaih, A. Kashani","doi":"10.1115/imece2021-69485","DOIUrl":"https://doi.org/10.1115/imece2021-69485","url":null,"abstract":"\u0000 Viscoelastic (VE) tuned mass dampers (TMDs) using commercially available, small thickness, VE material have been used extensively in adding targeted damping to light structures. The most common approach for realizing stiffness and damping in these tuned devices has been applying VE material to strips of elastic material (mainly metal, e.g. steel) in an unconstrained or constrained layer fashion and using such assemblies, which can be viewed as a damped leaf-springs, for the suspension element of the tuned mass damper. In this work, the suitability of tuned mass dampers with visco-elastically damped leaf-spring suspension for treating large, massive civil engineering structures, more specifically floor systems, was studied numerically and experimentally. The effectiveness of this tuned mass damper configuration turned out to be disappointing.\u0000 In parallel to the above-mentioned study, an alternative VE suspension was devised by stacking a number of 25 mm (1 inch) thick VE rings interlaced with the same number of metal constraining ring layers. By changing the number of these rings, different stiffness’s are realized and thus different tuning frequencies are achieved.\u0000 The material properties of the VE polymer used in both studies are defined in terms of Prony series parameters. Viewing the Prony series parameters as optimization variables, they are recovered by minimizing the mean squared error between the dynamic material properties predicted by the Prony series parameters and the frequency-dependent dynamic material properties provided by the manufacturer. Using the material properties of the VE material, the dynamic finite element model of a 100 lb TMD was constructed and its tuned damping effectiveness demonstrated, numerically. The 100 lb TMD was also built and used to a) verify the numerical model and b) experimentally demonstrate the performance of the TMD.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"94 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75640313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Active control schemes provide emergent wave properties and flexible tunability in mechanical systems. Here, we propose both analytically and numerically a non-Hermitian metamaterial system enabled by piezoelectric patches and electronic non-local feedback control. The metamaterial system is physically realized by a non-local microploar beam with non-local feedback control. Since the non-local feedback control breaks spatial reciprocity, the proposed metabeam supports not only non-reciprocal flexural wave amplification and attenuation, but also non-Hermitian skin effect featuring bulk localized eigenmodes in the finite structure. The non-reciprocal amplification and attenuation phenomena are quantitatively predicted by band structure analyses under both the continuum and discrete spring-mass representation, which can be attributed to the work exchange between mechanical and electric works. The non-Hermitian skin effect and the associated bulk localized eigenmodes are characterized by a topological invariant. In addition, direction-dependent bending stiffness is also demonstrated in the non-local micropolar piezoelectric metabeam with proper transfer functions. The electronically controllable non-Hermitian metabeam could pave the ways for designing future systems such as synthetic biofilaments and membranes with feed-back control schemes.
{"title":"A Micropolar Metabeam With Nonlocal Feedback Control Circuits","authors":"Qian Wu, Guoliang Huang","doi":"10.1115/imece2021-70609","DOIUrl":"https://doi.org/10.1115/imece2021-70609","url":null,"abstract":"\u0000 Active control schemes provide emergent wave properties and flexible tunability in mechanical systems. Here, we propose both analytically and numerically a non-Hermitian metamaterial system enabled by piezoelectric patches and electronic non-local feedback control. The metamaterial system is physically realized by a non-local microploar beam with non-local feedback control. Since the non-local feedback control breaks spatial reciprocity, the proposed metabeam supports not only non-reciprocal flexural wave amplification and attenuation, but also non-Hermitian skin effect featuring bulk localized eigenmodes in the finite structure. The non-reciprocal amplification and attenuation phenomena are quantitatively predicted by band structure analyses under both the continuum and discrete spring-mass representation, which can be attributed to the work exchange between mechanical and electric works. The non-Hermitian skin effect and the associated bulk localized eigenmodes are characterized by a topological invariant. In addition, direction-dependent bending stiffness is also demonstrated in the non-local micropolar piezoelectric metabeam with proper transfer functions. The electronically controllable non-Hermitian metabeam could pave the ways for designing future systems such as synthetic biofilaments and membranes with feed-back control schemes.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78568579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a novel metamaterial unit-cell configuration that may exhibit local resonance (LR) band gaps with exceptional properties — e.g., extreme width. The proposed configuration is comprised of a base wave-propagating medium to which a discrete periodic resonating branch — e.g., a branch made of a finite number of repeating diatomic unit cells — is connected. Such periodicity causes waves propagating in the branch to experience attenuation within the branch unit-cell Bragg band gap. The branch may also vibrate in resonance within its Bragg band gap due to the effect of the boundaries introduced upon truncating the nominal periodic medium. Such Bragg band-gap resonances exhibited by the branch are key to the proposed configuration as the metamaterial LR band gaps that form around them may possess exceptional properties. This paper shows that these exceptional LR band gaps are highly tunable and can be systematically designed using a semi-analytical design approach. The design approach is in part based on a recently derived analytical method that predicts, in advance, whether the branch would exhibit resonance and anti-resonance frequencies in its Bragg band-gap. Finally, a numerical case is discussed to showcase the proposed metamaterial configuration and design approach; it presents a metamaterial unit cell that demonstrates an extremely wide LR band gap. These findings open a route towards exploiting discrete, e.g., granular, periodic resonators to realize highly tunable LR band gaps.
{"title":"Bloch Wave Dynamics of a Branched Locally Resonant Metamaterial With a Discrete Periodic Resonating Branch","authors":"Mary V. Bastawrous, M. Hussein","doi":"10.1115/imece2021-70727","DOIUrl":"https://doi.org/10.1115/imece2021-70727","url":null,"abstract":"\u0000 This paper presents a novel metamaterial unit-cell configuration that may exhibit local resonance (LR) band gaps with exceptional properties — e.g., extreme width. The proposed configuration is comprised of a base wave-propagating medium to which a discrete periodic resonating branch — e.g., a branch made of a finite number of repeating diatomic unit cells — is connected. Such periodicity causes waves propagating in the branch to experience attenuation within the branch unit-cell Bragg band gap. The branch may also vibrate in resonance within its Bragg band gap due to the effect of the boundaries introduced upon truncating the nominal periodic medium. Such Bragg band-gap resonances exhibited by the branch are key to the proposed configuration as the metamaterial LR band gaps that form around them may possess exceptional properties. This paper shows that these exceptional LR band gaps are highly tunable and can be systematically designed using a semi-analytical design approach. The design approach is in part based on a recently derived analytical method that predicts, in advance, whether the branch would exhibit resonance and anti-resonance frequencies in its Bragg band-gap. Finally, a numerical case is discussed to showcase the proposed metamaterial configuration and design approach; it presents a metamaterial unit cell that demonstrates an extremely wide LR band gap. These findings open a route towards exploiting discrete, e.g., granular, periodic resonators to realize highly tunable LR band gaps.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78368177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junhong Zhang, Feiqi Long, Hongjie Jia, Jiewei Lin
Leaf springs play an important role in the handling stability and ride comfort of vehicle. End rubber gaskets are widely used to reduce the friction between leaves, but they also have considerable effect on the stiffness of the suspension assembly. The ride comfort may deteriorate with the stiffness of leaf spring changes. In this paper the influence of the end rubber gasket on the static stiffness performance of a parabolic leaf spring is studied. A finite element model of the leaf spring is developed and verified against the static stiffness test. Effects of the end rubber gasket parameters on the static stiffness of the leaf spring are analyzed based on an orthogonal experiment. The sensitivities of the five parameters are identified including the width, the length, the end thickness, the tail thickness and the distance to the end of the middle leaf. It is found that the contributions can be ranked in descending order as the tail thickness, the end thickness, the distance from end rubber gasket to the end of Leaf 2, and the width and length. The first two factors are considered of significant effects on the leaf spring stiffness. According to single-factor analysis, it is found that under the same load, as the tail thickness and the end thickness increase, the maximum deformation of the rubber gasket decreases, the stiffness of the rubber gasket increases, and the stiffness of the leaf spring increases, which provides a reference for the forward design of the end rubber gasket and the stiffness matching of leaf springs.
{"title":"Effect of End Rubber Gasket on the Performance of Parabolic Leaf Spring","authors":"Junhong Zhang, Feiqi Long, Hongjie Jia, Jiewei Lin","doi":"10.1115/IMECE2020-23546","DOIUrl":"https://doi.org/10.1115/IMECE2020-23546","url":null,"abstract":"\u0000 Leaf springs play an important role in the handling stability and ride comfort of vehicle. End rubber gaskets are widely used to reduce the friction between leaves, but they also have considerable effect on the stiffness of the suspension assembly. The ride comfort may deteriorate with the stiffness of leaf spring changes. In this paper the influence of the end rubber gasket on the static stiffness performance of a parabolic leaf spring is studied. A finite element model of the leaf spring is developed and verified against the static stiffness test. Effects of the end rubber gasket parameters on the static stiffness of the leaf spring are analyzed based on an orthogonal experiment. The sensitivities of the five parameters are identified including the width, the length, the end thickness, the tail thickness and the distance to the end of the middle leaf. It is found that the contributions can be ranked in descending order as the tail thickness, the end thickness, the distance from end rubber gasket to the end of Leaf 2, and the width and length. The first two factors are considered of significant effects on the leaf spring stiffness. According to single-factor analysis, it is found that under the same load, as the tail thickness and the end thickness increase, the maximum deformation of the rubber gasket decreases, the stiffness of the rubber gasket increases, and the stiffness of the leaf spring increases, which provides a reference for the forward design of the end rubber gasket and the stiffness matching of leaf springs.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":"137 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72702299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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