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Wang, B., Kari, L., Pang, H. & Gong, X. (2024). Modelling the dynamic magnetic actuation of isotropic soft magnetorheological elastomers. International Journal of Mechanical Sciences, 266, Article ID 108908.
Open this publication in new window or tab >>Modelling the dynamic magnetic actuation of isotropic soft magnetorheological elastomers
2024 (English)In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 266, article id 108908Article in journal (Refereed) Published
Abstract [en]

Soft magnetorheological elastomers (s-MRE) are a kind of smart material with soft magnetic particles embedded in an elastomer matrix. Under a magnetic field, there is pronounced magnetostriction and magnetically controllable mechanical properties for s-MRE, offering broad application prospects in soft robotics, surface pattern control and vibration control. While most existing literature on s-MRE focuses on the quasi-static behaviour, neglecting inertia effect, the dynamic behaviour and potential nonlinear oscillation phenomenon in certain scenarios of s-MRE-based actuators remain underexplored. In order to addressing this gap, a novel dynamic model which incorporates the magnetization, nonlinear viscoelasticity and inertia effects of isotropic s-MRE is proposed to explore the interplay among magnetic field, inertia and viscoelasticity on its dynamic behaviour. After developing the corresponding two-dimensional finite element implementation platform, this study examines the magnetic-induced dynamic behaviour of an isotropic s-MRE-based bilayer beam through numerical simulation. The influence of inertia and viscoelasticity on the magnetic-induced deformation as well as the unique nonlinear vibration characteristics of isotropic s-MRE-based system, such as superharmonic and resonance jump, are explored. Furthermore, to further enhance practical applications, novel magnetic field control algorithms aimed at mitigating harmonic distortion and tuning the vibration frequency of isotropic s-MRE-based magnetic actuation systems are introduced. These findings significantly advance the understanding the dynamic behaviour of s-MRE, paving the way for practical applications of s-MRE in magnetic field-driven loudspeakers and active noise control devices.

Place, publisher, year, edition, pages
Elsevier BV, 2024
Keywords
Constitutive modelling, Isotropic soft magnetorheological elastomers, Magnetic actuation, Magneto-mechanical coupling, Nonlinear vibration
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-341924 (URN)10.1016/j.ijmecsci.2023.108908 (DOI)001144920800001 ()2-s2.0-85180547247 (Scopus ID)
Note

QC 20240108

Available from: 2024-01-08 Created: 2024-01-08 Last updated: 2024-02-06Bibliographically approved
Vizcaíno-Vergara, M., Kari, L., Tunnicliffe, L. B. & Busfield, J. J. C. (2023). Evolution of the Viscoelastic Properties of Filler Reinforced Rubber under Physical Aging at Room Temperature. Polymers, 15(7), Article ID 1806.
Open this publication in new window or tab >>Evolution of the Viscoelastic Properties of Filler Reinforced Rubber under Physical Aging at Room Temperature
2023 (English)In: Polymers, E-ISSN 2073-4360, Vol. 15, no 7, article id 1806Article in journal (Refereed) Published
Abstract [en]

Filler reinforced rubber is widely used for engineering applications; therefore, a sound characterization of the effects of physical aging is crucial for accurately predicting its viscoelastic properties within its operational temperature range. Here, the torsion pendulum is used to monitor the evolution of the storage and loss modulus of carbon black filled samples for four days after a temperature drop to 30 degrees C. The storage modulus presents a continuous increase, while the loss modulus generally displays a steady decrease throughout the four days that each test was conducted. The relationship of the recovery rates with the carbon black properties is also studied, analysing its dependency on the particle size and aggregate structure. The evolution of the recovery rate seems to depend linearly on the surface area while the carbon black structure appears to have a much weaker influence on the physical aging behavior for the set of compounds tested. The obtained results corroborate the presence of physical aging at room temperature for filler rubber materials and the ability of the torsion pendulum to monitor the storage and loss modulus change, providing pivotal data on the influence of physical aging on the viscoelastic properties of the material.

Place, publisher, year, edition, pages
MDPI AG, 2023
Keywords
physical aging, carbon black, natural rubber, reinforced rubber, torsion pendulum, viscoelastic properties, storage modulus, loss modulus, external surface area, compressed oil adsorption number
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-326887 (URN)10.3390/polym15071806 (DOI)000968742800001 ()37050420 (PubMedID)2-s2.0-85152859646 (Scopus ID)
Note

QC 20230515

Available from: 2023-05-15 Created: 2023-05-15 Last updated: 2024-01-17Bibliographically approved
Wang, B., Bustamante, R., Kari, L., Pang, H. & Gong, X. (2023). Modelling the influence of magnetic fields to the viscoelastic behaviour of soft magnetorheological elastomers under finite strains. International journal of plasticity, 164, Article ID 103578.
Open this publication in new window or tab >>Modelling the influence of magnetic fields to the viscoelastic behaviour of soft magnetorheological elastomers under finite strains
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2023 (English)In: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 164, article id 103578Article in journal (Refereed) Published
Abstract [en]

Isotropic soft magneto-rheological elastomers (s-MRE) are polymer-based composites where magnetically soft particles are randomly distributed in the elastomer matrix. Under a magnetic field, a strong modulus magnetic stiffening effect and a magnetostriction performance is exhibited for isotropic s-MRE, offering a wide application potential in vibration control, soft robotics and haptic displays. In the last decades, substantial theoretical work has focused on modelling the magnetostriction behaviour of isotropic s-MRE. Modelling the influence of magnetic fields to the viscoelastic behaviour of isotropic s-MRE has received less attention, despite the magnetic-dependent viscoelasticity is an essential component of the observed magneto-mechanical response and of great importance for the application of isotropic s-MRE. To predict the magneto-mechanical coupling behaviour accurately and provide guidance for the design of isotropic s-MRE-based applications, a multiplicatively-typed magneto-hyperelastic free energy and a new type of process-dependent viscosity evolution law is proposed in this work. Afterwards, the ability of the model to predict the modulus magnetic stiffening effect and magnetic-dependent nonlinear viscoelastic behaviour of isotropic s-MRE is examined. Finally, three sets of finite element case studies are presented to illustrate the feasibility of the model-based simulation and guide the design of isotropic s-MRE-related applications.

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
Constitutive modelling, Finite element implementation, Isotropic soft magneto-rheological elastomers, Magnetic-dependent nonlinear viscoelasticity, Modulus magnetic stiffening effect
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-330911 (URN)10.1016/j.ijplas.2023.103578 (DOI)001026110400001 ()2-s2.0-85152594487 (Scopus ID)
Note

QC 20230705

Available from: 2023-07-05 Created: 2023-07-05 Last updated: 2023-07-31Bibliographically approved
Vizcaíno-Vergara, M. D., Kari, L. & Busfield, J. J. (2023). Physical ageing evolution of the viscoelastic properties of filler reinforced rubber measured with the torsion pendulum after a temperature change. In: Marano, C Vangosa, FB Andena, L Frassine, R (Ed.), Constitutive Models for Rubber XII, ECCMR 2022: . Paper presented at 12th EUROPEAN CONFERENCE ON CONSTITUTIVE MODELS FOR RUBBER (ECCMR), SEP 07-09, 2022, Milan, ITALY (pp. 397-401). Informa UK Limited
Open this publication in new window or tab >>Physical ageing evolution of the viscoelastic properties of filler reinforced rubber measured with the torsion pendulum after a temperature change
2023 (English)In: Constitutive Models for Rubber XII, ECCMR 2022 / [ed] Marano, C Vangosa, FB Andena, L Frassine, R, Informa UK Limited , 2023, p. 397-401Conference paper, Published paper (Refereed)
Abstract [en]

The viscoelastic properties of filler reinforced rubber are measured at small strains with the torsion pendulum after a temperature change and the evolution of the storage and loss modulus is measured against the physical ageing time. Physical ageing refers to the state in which the molecules are out of thermodynamic equilibrium after a temperature change. The time needed to achieve equilibrium is the physical ageing time, during which the material displays shifting mechanical properties. For unfilled rubber, physical ageing occurs only after temperature changes below the glass transition temperature, T-g. However, filler reinforced rubber presents physical ageing after a temperature change at temperatures significantly above T-g. Therefore, the existing models of physical ageing are unsuitable for filler reinforced rubber and further characterization of the evolution of their viscoelastic properties after a temperature change is needed. The torsion pendulum is utilised to measure the material properties since it allows measurements in the rheological simple linear viscoelastic small strains and during long periods of time. The impulse response function obtained from the torsion pendulum measurements is used to calculate the storage and loss modulus at different times after a rapid temperature decrease at room temperatures. The resulting evolution shows a progressive stiffening of the material with an increase of storage modulus and decrease of loss modulus with physical ageing time. This investigation on the evolution of the viscoelastic properties after a temperature change sets the path for a proper characterization of the physical ageing phenomena for filler reinforced rubber and this allows a more reliable constitutive model to be derived.

Place, publisher, year, edition, pages
Informa UK Limited, 2023
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-350841 (URN)10.1201/9781003310266-65 (DOI)001238778400065 ()
Conference
12th EUROPEAN CONFERENCE ON CONSTITUTIVE MODELS FOR RUBBER (ECCMR), SEP 07-09, 2022, Milan, ITALY
Note

Part of ISBN 978-1-032-31554-6, 978-1-003-31026-6, 978-1-032-31553-9

Available from: 2024-07-22 Created: 2024-07-22 Last updated: 2024-07-22Bibliographically approved
Erenchun, A., Blanco, B., Gil-Negrete, N., Wang, B. & Kari, L. (2022). Effect of lubrication on the mechanical behavior of magnetorheological elastomers in compression mode. Polymer testing, 111, Article ID 107617.
Open this publication in new window or tab >>Effect of lubrication on the mechanical behavior of magnetorheological elastomers in compression mode
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2022 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 111, article id 107617Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Magnetorheological elastomer, Compression mode, Lubrication, Magnetosensitive effect
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-313774 (URN)10.1016/j.polymertesting.2022.107617 (DOI)000800002800002 ()2-s2.0-85129755533 (Scopus ID)
Note

QC 20220610

Available from: 2022-06-10 Created: 2022-06-10 Last updated: 2022-06-25Bibliographically approved
Högfeldt, A.-K., Gumaelius, L., Berglund, P., Kari, L., Pears, A. & Kann, V. (2022). Leadership, support and organisation for academics'€™ participation in engineering education change for sustainable development. European Journal of Engineering Education
Open this publication in new window or tab >>Leadership, support and organisation for academics'€™ participation in engineering education change for sustainable development
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2022 (English)In: European Journal of Engineering Education, ISSN 0304-3797, E-ISSN 1469-5898Article in journal (Refereed) Published
Abstract [en]

This work spotlights the experiences from ten years of implementing sustainable development in all educational programs at a technical university. With a focus on the critical issue of involving more academics in the work, experiences are shared through an ethnographic account including focus group interviews. "€˜Sustainable development"€™ has been perceived as both superficial and overwhelming; unclear yet somehow predetermined; it has been perceived to demand non-existent space in the curriculum; and it has challenged the academics regardless of the subjects'€™ relatedness to sustainability. It is concluded that the evolution of a web of interconnected people, key academics, activities, norms and tools has contributed to an increased participation. The work for authenticity, reliability and feasibility, along with institution-wide and long-term academic development tools is presented.

Place, publisher, year, edition, pages
Informa UK Limited, 2022
Keywords
Academic leadership, academic development, activity theory, social practice theory, participatory practices
National Category
Learning
Research subject
Education and Communication in the Technological Sciences
Identifiers
urn:nbn:se:kth:diva-317220 (URN)10.1080/03043797.2022.2106824 (DOI)000836131500001 ()2-s2.0-85135264799 (Scopus ID)
Note

QC 20220913

Available from: 2022-09-07 Created: 2022-09-07 Last updated: 2022-09-13Bibliographically approved
Gomez, E. R., Kari, L. & Lopez Arteaga, I. (2022). Powertrain shuffle-mode resonance suppression by means of flywheel mounted torsichrone centrifugal pendulum vibration absorbers. Journal of Sound and Vibration, 534, Article ID 117014.
Open this publication in new window or tab >>Powertrain shuffle-mode resonance suppression by means of flywheel mounted torsichrone centrifugal pendulum vibration absorbers
2022 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 534, article id 117014Article in journal (Refereed) Published
Abstract [en]

A flywheel mounted centrifugal pendulum absorber (CPVA) is designed to completely suppress the low frequency shuffle-mode resonance of a heavy-duty truck powertrain by exploiting the eigenfrequency veering property of the CPVA. The shuffle-mode is excited by the half-order torque of a five-cylinder engine in a downspeeded powertrain during cruising conditions. It is shown that the design of the CPVA may be performed by linear analysis of the CPVA and powertrain system. The linear design is then validated by full nonlinear simulations of the powertrain. A complete suppression of the shuffle-mode resonance is achieved with relatively small total mass of the pendula which makes it highly possible to implement in practice. Downspeeding and downsizing of combustion engines, without sacrificing the power output, are methods to reduce emissions, although, resulting in increased noise and vibration using conventional vibration reduction technology. The CPVA is an order tuned device that can help to reduce the increased vibrations and thus help to reduce the environmental impact of heavy-duty vehicles.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Centrifugal pendulum vibration absorber, Friction, Torsional vibration, Powertrain, Eigenfrequency veering
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-316292 (URN)10.1016/j.jsv.2022.117014 (DOI)000828615100005 ()2-s2.0-85133975321 (Scopus ID)
Note

QC 20220812

Available from: 2022-08-12 Created: 2022-08-12 Last updated: 2022-08-12Bibliographically approved
Gomez, E., Sjöstrand, J., Kari, L. & Lopez Arteaga, I. (2022). Torsional vibrations in heavy-truck powertrains with flywheel attached centrifugal pendulum vibration absorbers. Mechanism and machine theory, 167, Article ID 104547.
Open this publication in new window or tab >>Torsional vibrations in heavy-truck powertrains with flywheel attached centrifugal pendulum vibration absorbers
2022 (English)In: Mechanism and machine theory, ISSN 0094-114X, E-ISSN 1873-3999, Vol. 167, article id 104547Article in journal (Refereed) Published
Abstract [en]

A nonlinear centrifugal pendulum vibration absorber (CPVA) with normal-force dependant friction loss is investigated in a torsional model of a downspeeded powertrain of a heavy-truck. The engine model includes gas-pressure excitation and the existing pendulum model is extended to include a continuous formulation of end-stops at the end of the pendulum-path. Furthermore, the friction loss of the pendulum is experimentally determined. A pendulum-path parameter-study in the complete powertrain model is conducted to consider the effects of the system dynamics on the CPVA. It is shown that the performance of the CPVA is affected by the powertrain system-dynamics and thus important to consider in the design of the CPVA. Downspeeding of the engine by appropriate gearing of the driveline is a measure to decrease the CO2 emissions. However, downspeeding increases the torsional vibration and noise of the powertrain with conventional torsional vibration reduction methods. The CPVA can be used to reduce the torsional vibration and thus facilitate to reach environmental goals.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Centrifugal pendulum vibration absorber, Friction, Torsional vibration, Heavy-duty truck, Reciprocating engine, Powertrain
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-303029 (URN)10.1016/j.mechmachtheory.2021.104547 (DOI)000696837100001 ()2-s2.0-85114810243 (Scopus ID)
Note

QC 20211026

Available from: 2021-10-26 Created: 2021-10-26 Last updated: 2022-06-25Bibliographically approved
Vizcaíno-Vergara, M. D., Tunnicliffe, L. B., Busfield, J. J. & Kari, L. (2022). Viscoelastic characterisation of carbon black reinforced rubber using the torsion pendulum: Guidelines and temperature sweep results. Polymer testing, 114, Article ID 107692.
Open this publication in new window or tab >>Viscoelastic characterisation of carbon black reinforced rubber using the torsion pendulum: Guidelines and temperature sweep results
2022 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 114, article id 107692Article in journal (Refereed) Published
Abstract [en]

A comprehensive set of guidelines on the use of the torsion pendulum for the viscoelastic characterisation of carbon black reinforced rubber is presented, including the set up selection, the post processing steps and the final evaluation of the method using temperature sweep results at small strains. The torsion pendulum is based on the free vibration principle, in which the sample is instantaneously perturbed to initiate a torsional movement and then left to freely vibrate. From the frequency and damping of this impulse response function, the properties of the material can be obtained against temperature and time. However, despite the extensive use for many years of the torsion pendulum, the difficulty of activating only the desired torsional mode hinders the acquisition of accurate results. The method presented aims to improve the torsion pendulum performance and can be divided in two stages. The pre-testing phase covers the influence of the test set up and sample geometry on the measured response. The test set up will determine the frequency at which the dynamic properties are obtained, while the sample geometry will influence the torsional strain and bending deflection. The post-testing phase includes the steps to post-process the curve and the criteria to identify and select the most reliable data sets from all of the measured data. The quality of the curve is assessed in the frequency domain by evaluating the frequency components of its Fast Fourier Transform and in the time domain by evaluating its fit to an ideal exponentially decreasing sinusoidal curve. The final selection of the response functions that can be used to measure the viscoelastic properties of the rubber samples is made based on the maximum strain level and the minimum variation of the dynamic properties within one curve. The validity of the method is then tested by comparing temperature sweep results before and after the application of the presented guidelines, where a clear decrease on the results deviation can be observed. Finally, the results obtained with this method are compared to Dynamic Mechanical Analysis results over the same temperature range, where a good fit is obtained. Thus, this investigation presents a comprehensive method, useful to all torsional pendulum users aiming to measure and characterise the mechanical behaviour of viscoelastic materials.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Carbon black filled rubber, Dynamic modulus, Temperature sweep, Torsion pendulum, Viscoelastic characterisation
National Category
Medical Laboratory Technologies
Identifiers
urn:nbn:se:kth:diva-316035 (URN)10.1016/j.polymertesting.2022.107692 (DOI)000829719700001 ()2-s2.0-85134397454 (Scopus ID)
Note

QC 20220809

Available from: 2022-08-09 Created: 2022-08-09 Last updated: 2025-02-09Bibliographically approved
Lejon, J., Wang, B. & Kari, L. (2021). A constitutive model of the dynamic shear modulus dependence on temperature, prestrain, dynamic strain amplitude and magnetic field for magneto-sensitive elastomer. International Journal of Solids and Structures, 219, 106-119
Open this publication in new window or tab >>A constitutive model of the dynamic shear modulus dependence on temperature, prestrain, dynamic strain amplitude and magnetic field for magneto-sensitive elastomer
2021 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 219, p. 106-119Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier BV, 2021
Keywords
Magneto-sensitive elastomer, Prestrain, Temperature, Non-linear, Dynamic strain amplitude
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-295364 (URN)10.1016/j.ijsolstr.2021.02.017 (DOI)000641140500009 ()2-s2.0-85102971855 (Scopus ID)
Note

QC 20210607

Available from: 2021-05-24 Created: 2021-05-24 Last updated: 2022-06-25Bibliographically approved
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