| 1. |
- Wang, Bochao, et al.
(author)
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The influence of particle chain-magnetic field spatial location, frequency, dynamic strain amplitude and the prestrain on the mechanical performance of anisotropic magneto-rheological elastomer
- 2021
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In: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 104, s. 107411-
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Journal article (peer-reviewed)abstract
- Although there are literatures to characterize the properties of anisotropic magneto-rheological elastomer (MRE), more attention is paid when the particle chain is parallel to the applied magnetic field. However, in prospective of modeling and application design, mechanical characterization of anisotropic MRE under other particle chain-magnetic field spatial locations is needed. Herein, mechanical properties of anisotropic MRE with four kinds of particle chain-magnetic field spatial locations under varies frequencies, strain amplitudes and prestrains are tested. It shows that even the particle chain is perpendicular to the magnetic field, there exists an obvious MR effect. Besides the attraction of adjacent magnetized particles, the Maxwell stress tensor also contribute to the MR effect. Furthermore, an obvious strain amplitude dependent viscoelastic behavior is exhibited for anisotropic MRE. Moreover, the MR effect and the loss factor decrease as the increase of prestrain. The investigation contributes to the designing, modeling and applications of anisotropic MRE.
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| 2. |
- Boudreau, Mathieu, et al.
(author)
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Repeat it without me: Crowdsourcing the T1 mapping common ground via the ISMRM reproducibility challenge
- 2024
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In: MAGNETIC RESONANCE IN MEDICINE. - 0740-3194 .- 1522-2594. ; 92:3, s. 1115-1127
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Journal article (peer-reviewed)abstract
- Purpose T-1 mapping is a widely used quantitative MRI technique, but its tissue-specific values remain inconsistent across protocols, sites, and vendors. The ISMRM Reproducible Research and Quantitative MR study groups jointly launched a challenge to assess the reproducibility of a well-established inversion-recovery T-1 mapping technique, using acquisition details from a seminal T-1 mapping paper on a standardized phantom and in human brains. Methods The challenge used the acquisition protocol from Barral et al. (2010). Researchers collected T-1 mapping data on the ISMRM/NIST phantom and/or in human brains. Data submission, pipeline development, and analysis were conducted using open-source platforms. Intersubmission and intrasubmission comparisons were performed. Results Eighteen submissions (39 phantom and 56 human datasets) on scanners by three MRI vendors were collected at 3 T (except one, at 0.35 T). The mean coefficient of variation was 6.1% for intersubmission phantom measurements, and 2.9% for intrasubmission measurements. For humans, the intersubmission/intrasubmission coefficient of variation was 5.9/3.2% in the genu and 16/6.9% in the cortex. An interactive dashboard for data visualization was also eveloped: https://rrsg2020.dashboards.neurolibre.org. Conclusion The T-1 intersubmission variability was twice as high as the intrasubmission variability in both phantoms and human brains, indicating that the acquisition details in the original paper were insufficient to reproduce a quantitative MRI protocol. This study reports the inherent uncertainty in T-1 measures across independent research groups, bringing us one step closer to a practical clinical baseline of T-1 variations in vivo.
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| 3. |
- Erenchun, Aitor, et al.
(author)
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Effect of lubrication on the mechanical behavior of magnetorheological elastomers in compression mode
- 2022
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In: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 111
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Journal article (peer-reviewed)abstract
- The effect of the lubrication on the mechanical behavior of magnetorheological elastomers (MREs) in compression mode is experimentally studied. According to ISO 7743, there are two procedures to characterize specimens in compression mode. Differences in the properties of these materials between lubricated and nonlubricated conditions must be considered if devices such as vibration absorbers and isolators are to be developed. With lubrication, compression is said to be uniaxial and homogeneous, thus material properties can be obtained. Without lubrication, tests are easier to perform but results are strongly dependent on the piece shape. In this study isotropic and anisotropic MREs with iron particle volume concentrations of 10, 20, 30 and 40% are tested under different strain amplitudes, prestrain and magnetic fields for a frequency range up to 300 Hz, with and without lubrication. Important design parameters like amplitude, frequency and magnetic field dependency are showed to be dependent on lubrication.
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| 4. |
- Erenchun, A., et al.
(author)
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Model of an elevator system to characterize the influence of the isolator on the vibration transmission
- 2020
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In: Proceedings International Conference on Noise and Vibration Engineering (ISMA2020) / International Conference on Uncertainty in Structural Dynamics (USD). - : KU Leuven. ; , s. 2715-2729
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Conference paper (peer-reviewed)abstract
- Vibrations are a common issue in elevator installations, where a drive machine that holds and pulls the cabin and the counterweight composes the electromechanical system. In order to reduce the space needed by the installation, nowadays the drive machine is usually mounted upon a frame that is fixed to the guide rails. Therefore, vibration transmission can occur through the machine to the cabin or even to the building. With the purpose of reducing this vibration transmission, the use of isolators under the machine is a widely employed solution. These isolators are often selected just taking into account the static loads, due to the lack of information about the dynamic behavior of the system. The present research develops a theoretical model of an elevator system to study the influence of the isolators on vibration transmission.
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| 5. |
- Lejon, Jonas, et al.
(author)
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A constitutive model of the dynamic shear modulus dependence on temperature, prestrain, dynamic strain amplitude and magnetic field for magneto-sensitive elastomer
- 2021
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In: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 219, s. 106-119
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Journal article (peer-reviewed)abstract
- A constitutive model for the temperature, prestrain, dynamic strain amplitude and the magnetic field dependence of the dynamic shear modulus for a magneto-sensitive (MS) elastomer is developed. It is an augmentation of a model consisting of an elastic, fractional order derivative viscoelastic and a nonlinear amplitude-dependent smooth Coulomb friction model. The magnetic field dependence is reflected by a parabolic function with an upper limit. A Yeoh formulation of the strain energy function is applied to represent the prestrain dependence. To cover the temperature dependence, a Williams-Landel-Ferry function and an Arrhenius function are used. After parameter identification, a good agreement between the simulation and measurement results is shown, which demonstrates the ability of the model to cover the prestrain and temperature dependency of MS elastomer. Therefore, the expansion of the model to cover the prestrain and temperature enables the prediction of the mechanical performance of MS elastomer under various conditions and improves the possibilities for MS dampers and mounts to meet design criteria.
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| 6. |
- Wang, Bochao, et al.
(author)
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A nonlinear constitutive model by spring, fractional derivative and modified bounding surface model to represent the amplitude, frequency and the magnetic dependency for Magneto-sensitive rubber
- 2019
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In: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 438, s. 344-352
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Journal article (peer-reviewed)abstract
- Magneto-sensitive (MS) rubber is a kind of smart material mainly consisting of magnetizable particles and rubber. Inspired by experimental observation that the shear modulus for MS rubber is strongly dependent on amplitude, frequency and magnetic field; while the impact for the magnetic field and strain to the loss factor is relatively small, a new nonlinear constitutive model for MS rubber is presented. It consists of a fractional viscoelastic model, an elastic model and a bounding surface model with parameters sensitive to the magnetic field. To our knowledge, it is the first time that the bounding surface model is incorporated with the magnetic sensitivity and used to predict the mechanical properties for MS rubber. After comparison with the measurement results, it is found that the shear modulus and the loss factor derived from the simulation fit well with the experimental data. This new constitutive model with only eight parameters can be utilized to describe the amplitude, frequency and the magnetic field dependence for MS rubber. It provides a possible new way to understand the mechanical behavior for MS rubber. More importantly, the constitutive model with an accurate prediction property for the dynamic performance of MS rubber is of interest for MS rubber applications in noise and vibration reduction area.
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| 7. |
- Wang, Bochao, et al.
(author)
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A visco-elastic-plastic constitutive model of isotropic magneto-sensitive rubber with amplitude, frequency and magnetic dependency
- 2020
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In: International journal of plasticity. - : Elsevier. - 0749-6419 .- 1879-2154. ; 132
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Journal article (peer-reviewed)abstract
- A three-dimensional visco-elastic-plastic constitutive model of isotropic magneto-sensitive (MS) rubber with amplitude, frequency and magnetic dependency under a continuum constitutive framework is developed. MS rubber is akind of smart material mainly composed of a rubber matrix and magnetizable particles. Under a magnetic field, there is an increase of its dynamic modulus due to the interaction between the magnetic field and MS rubber, which is often referred to as the magnetic dependency of MS rubber. Experimental results reveal that besides the magnetic dependency, there is a frequency and amplitude dependency of its dynamic modulus. In specific, the modulus of MS rubber increases with increasing frequency and dereases with increasing strain amplitude. To depict the above properties and to consider the balance of energy in continuum mechanics framework, a new constitutive model consisting of a viscoelastic fractional derivative element, a bounding surface model in series with a neo-Hookean elastic model with magnetic sensitivity and a magnetic stress tensor term for MS rubber is proposed. The contribution of this constitutive model is that by using a free energy based method, with only eight material parameters, the amplitude, frequency and magnetic dependency of MS rubber can be reflected. After parameter identification, the simulationresults show a good agreement with those of measurements. Therefore, by utilizing the model proposed, the ability of approaching the dynamic behavior of MS rubber-based vibration reduction devices in the design phase is possible which contributes to the application of MS rubber in noise and vibration reduction area.
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| 8. |
- Wang, Bochao, et al.
(author)
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Constitutive model of isotropic magneto-sensitive rubber with amplitude, frequency, magnetic and temperature dependence under a continuum mechanics basis
- 2020
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In: International Journal of Engineering Science. - 0020-7225 .- 1879-2197.
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Journal article (other academic/artistic)abstract
- A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temperature-dependent mechanical properties of isotropic magneto-sensitive (MS) rubber is developed. The main components of MS rubberis an elastomer matrix and magnetizable particles. When a magnetic field is applied, the modulus of MS rubber increases, which is known as the magnetic dependence of MS rubber. In addition to the magnetic dependence, there arefrequency, amplitude and temperature dependencies of MS rubber. Specifically, a higher frequency, a smaller strain amplitude and a lower temperature lead to an increased magnitude of the dynamic modulus. To represent the above properties and to stimulate the possible application of MS rubber in the anti-vibration area, a continuum mechanic framework based constitutive model consisting of a fractional standard linear solid (SLS) element, an elastoplastic element and a magnetic stress term of MS rubber is developed. The frequency and amplitude dependencies are depicted by a fractional SLS element and an elastoplastic element, respectively. A hyperbolic tangent function with a scalar product of magnetic flux density as an independent variable is introduced to consider the magnetic dependence. Furthermore, the temperature dependence is taken into account by including the William-Landel-Ferry function and the Arrhenius function to the fractional SLS element and the elastoplastic element, respectively. The technical innovation of this constitutive model is that the amplitude, frequency, magnetic and temperature dependent mechanical properties of MS rubber are incorporated into a whole constitutive model under the continuum mechanics frame and based on the free energy assumption. Comparison between the simulation and measurement results in a wide frequency range with different levels of magnetic field, strain amplitude and temperature shows that the fitting effect of the developed model is very good. Therefore, the constitutive model proposed in this paper enables the prediction ofthe mechanical properties of MS rubber under various operating conditions with high accuracy, which will drive MS rubber’s application in engineering applications, especially in the area of MS rubber-based anti-vibration devices.
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| 9. |
- Wang, Bochao, et al.
(author)
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Constitutive Model of Isotropic Magneto-Sensitive Rubber with Amplitude, Frequency, Magnetic and Temperature Dependence under a Continuum Mechanics Basis
- 2021
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In: Polymers. - : MDPI AG. - 2073-4360. ; 13:3
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Journal article (peer-reviewed)abstract
- A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temperature dependent mechanical property of isotropic magneto-sensitive (MS) rubber is developed. The main components of MS rubber are an elastomer matrix and magnetizable particles. When a magnetic field is applied, the modulus of MS rubber increases, which is known as the magnetic dependence of MS rubber. In addition to the magnetic dependence, there are frequency, amplitude and temperature dependencies of the dynamic modulus of MS rubber. A continuum mechanical framework-based constitutive model consisting of a fractional standard linear solid (SLS) element, an elastoplastic element and a magnetic stress term of MS rubber is developed to depict the mechanical behavior of MS rubber. The novelty is that the amplitude, frequency, magnetic and temperature dependent mechancial properties of MS rubber are integrated into a whole constitutive model under the continuum mechanics frame. Comparison between the simulation and measurement results shows that the fitting effect of the developed model is very good. Therefore, the constitutive model proposed enables the prediction of the mechanical properties of MS rubber under various operating conditions with a high accuracy, which will drive MS rubber's application in engineering problems, especially in the area of MS rubber-based anti-vibration devices.
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| 10. |
- Wang, Bochao
(author)
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Constitutive models of magneto-sensitive rubber under a continuum mechanics basis and the application in vibration isolation
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Due to its durability, stretchability, relatively low stiffness and high damping, rubber is widely used in engineering anti-vibration fields. However, a major deficiency is that once installed, the mechanical properties of traditional rubber-based devices are fixed where its adaptability to various loading conditions is poor. An alternative to traditional rubber materials is magneto-sensitive (MS) rubber. The main componentsof MS rubber are a rubber matrix and ferromagnetic particles. Under a magnetic field, the modulus of MS rubber can be altered rapidly and reversibly. Therefore, compared with conventional rubber-based devices, the stiffness of MS rubber-based devices can be adapted to various loading conditions and an enhanced vibration reduction effect can be achieved. Measurement results revealed that the mechanical behavior of MS rubber is not simple. To be specific, the dynamic modulus of MS rubber has a magnetic, frequency,amplitude and temperature dependency. In order to promote the applications of MS rubber in the anti-vibration area, models to depict the above properties are needed. The main goal of this thesis is to model the magnetic, frequency, amplitude and temperature dependence of MS rubber under a continuum mechanics basis. The research results regarding the constitutive modeling consist of three papers (Paper A, C and D). The simulation results show a good agreement with the measurement data, which proves the accuracy and feasibility of the developed model. In addition to the constitutive models of MS rubber, an investigation of MS rubber application in the vibration isolation system under harmonic and random loading cases is numerically conducted (Paper B). In order to achieve an enhanced vibration isolation effect, two control algorithms corresponding to the harmonic and random loading are developed. Numerical results verify that the vibration isolation effect ofMS rubber vibration isolator is better than the traditional rubber-based isolator. In this thesis, the model developed for MS rubber deepens the understanding of how magnetic, frequency, amplitude and temperature affect the mechanical performance of MS rubber. Moreover, the research of MS rubber application in vibration isolators and the corresponding control strategies are helpful for the design of MS rubber-based anti-vibration devices.
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