L. Kari - Academia.edu (original) (raw)

Papers by L. Kari

A time domain non-linear model is presented to predict the dynamic stiffness of rubber isolators ... more A time domain non-linear model is presented to predict the dynamic stiffness of rubber isolators using a FE code. The problem of simultaneously modelling elastic, viscoelastic and friction contributions is removed by additively splitting them. Viscoelastic response is modelled via a fractional derivative model, while amplitude dependency is considered through Coulomb friction elements. Nevertheless, determination of the dynamic stiffness takes long time and requires large amount of memory, as well as the estimation of the transfer function between applied excitation and resulting forces at different frequency and amplitude values. This is why a frequency domain simplified procedure is also proposed to obtain the dynamic stiffness. The technique is based on providing a generalized Maxwell model with the adequate material data set, once the dynamic strain amplitude, to which the mount is subjected, is estimated from quasi-static strain values. The methodology has proved to be efficien...

This paper provides a creative approach on how to implement CDIO-techniques into a Engineering Ph... more This paper provides a creative approach on how to implement CDIO-techniques into a Engineering Physics program. A comparison is made between the Vehicle Engineering program and the Engineering Physics program at the Royal Institute of Technology (KTH), in order to establish what the grounds and potentials for implementing CDIO into a new program environment are. The Engineering Physics program is examined not only though the comparison but also through an indicatory survey performed with students, instructors and representatives from the industry. This is done in order to map the perceived nature of the program. Furthermore, these potentials are explored from the view of the Engineering Physics program at KTH, and implementation strategies are suggested and elaborated in accordance with derived results and indicators, using modelling and simulation as a ground for an abstract product orientation.

A shape factor based non-linear model of a rubber cylinder's tem-perature and preload depend... more A shape factor based non-linear model of a rubber cylinder's tem-perature and preload dependent static stiffness is presented. The in-fluence of temperature, precom-pression, material parameters, cy-linder length and diameter, are in-vestigated; with the motion split into a homogeneous thermal expansion including a globally equivalent pre-load deformation. Stiffness depends strongly on preload, particularly in larger shape factors, and on tem-perature. The model proves superior to traditional work in typical shape factors, with results close to those of finite element models. Zur nichtlinearen temperatur-abhaÈngigen Steifigkeit von

Constitutive Models for Rubber IV, 2017

Effective engineering formula for torsion stiffness of a long rubber bush in the frequency domain... more Effective engineering formula for torsion stiffness of a long rubber bush in the frequency domain including amplitude dependence is presented. The classical theory of elasticity is the tool used to ...

Measurement, 2017

A novel test rig design is presented which enables detailed studies of the three force components... more A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for the tread block-substrate contact and enables force measurements at high rolling speeds with a high signal-to-noise ratio. Measurements of the rolling contact forces are presented for different values of rolling velocity, static pre-load and acceleration. It is demonstrated that this test rig provides results which contribute to the understanding of tyre-road interaction and can be used as input to modelling-based development of both tyres and roads aiming for improved handling, safety, energy efficiency and comfort.

Constitutive Models for Rubber VI, 2009

The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation... more The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated, where influences of excitation position, amplitude, frequenc ...

Journal of Applied Mechanics, 2008

A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitu... more A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitude are taken into account through fractional order viscoelasticity and plasticity, respectively. The problem of simultaneously modeling elastic, viscoelastic, and friction contributions is removed by additively splitting them. Due to the fractional order representation mainly, the number of parameters of the model remains low, rendering an easy fitting of the values from tests on material samples. The proposed model is implemented in a general-purpose finite element (FE) code. Since commercial FE codes do not contain any suitable constitutive model that represents the full dynamic behavior of rubber compounds (including frequency and amplitude dependent effects), a simple approach is used based on the idea of adding stress contributions from simple constitutive models: a mesh overlay technique, whose basic idea is to create a different FE model for each material definition (fractional de...

Polymers

A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temper... more 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 ...

Materials

Traditional vibration isolation systems, using natural rubber vibration isolators, display large ... more Traditional vibration isolation systems, using natural rubber vibration isolators, display large peaks for the energy flow from the machine source and into the receiving foundation, at the unavoidable rigid body resonance frequencies. However, tough, doubly cross-linked, single polymer network hydrogels, with both chemical and physical cross-links, show a high loss factor over a specific frequency range, due to the intensive adhesion–deadhesion activities of the physical cross-links. In this study, vibration isolators, made of this tough hydrogel, are theoretically applied in a realistic vibration isolation system, displaying several rigid body resonances and various energy flow transmission paths. A simulation model is developed, that includes a suitable stress–strain model, and shows a significant reduction of the energy flow peaks. In particular, the reduction is more than 30 times, as compared to the corresponding results using the natural rubber. Finally, it is shown that a sig...

Materials

Tough, doubly cross-linked, single polymer network hydrogels with both chemical and physical cros... more Tough, doubly cross-linked, single polymer network hydrogels with both chemical and physical cross-links display a high loss factor of the shear modulus over a broad frequency range. Physically, the high loss factor is resulting from the intensive adhesion–deadhesion activities of the physical cross-links. A high loss factor is frequently required by the optimization processes for optimal performance of a primary vibration system while adopting a dynamic vibration absorber, in particular while selecting a larger dynamic vibration absorber mass in order to avoid an excess displacement amplitude of the dynamic vibration absorber springs. The novel idea in this paper is to apply this tough polymer hydrogel as a dynamic vibration absorber spring material. To this end, a simulation model is developed while including a suitable constitutive viscoelastic material model for doubly cross-linked, single polymer network polyvinyl alcohol hydrogels with both chemical and physical cross-links. I...

Continuum Mechanics and Thermodynamics

An effective fractional derivative-based visco-elastic model of tough, doubly cross-linked, singl... more An effective fractional derivative-based visco-elastic model of tough, doubly cross-linked, single-network polyvinyl alcohol (PVA) hydrogels, embodying both chemical and physical cross-links, is developed using a Mittag–Leffler relaxation function of order 1/2 while applying only three material parameters that are physically quantifiable, namely frequency for maximum loss modulus, equilibrium elastic modulus and relaxation intensity. The resulting 3-parameter shear modulus model is possible to additively split into chemical and physical parts; the split being the study focus. Physical explanations of the visco-elastic low-, mid- and high-frequency range properties, and their transitions between the frequency ranges, are given mainly in terms of the permanent chemical cross-links and the distinct adhesion–deadhesion processes of the transient physical cross-links. The latter are running from an associated Rouse mode low-frequency behaviour through a maximum adhesion–deadhesion dissip...

Computers & Structures

An analytical expression is formulated to compute the Jacobian matrix for 3D friction contact mod... more An analytical expression is formulated to compute the Jacobian matrix for 3D friction contact modelling that efficiently evaluates the matrix while computing the friction contact forces in the time domain by means of the alternate frequency time domain approach. The developed expression is successfully used for the calculation of the friction damping on a turbine blade with shroud contact interface having an arbitrary 3D relative displacement. The analytical expression drastically reduces the computation time of the Jacobian matrix with respect to the classical finite difference method, with many points at the contact interface. Therefore, it also significantly reduces the overall computation time for the solution of the equations of motion, since the formulation of the Jacobian matrix is the most time consuming step in solving the large set of nonlinear algebraic equations when a finite difference approach is employed. The equations of motion are formulated in the frequency domain using the multiharmonic balance method to accurately capture the nonlinear contact forces and displacements. Moreover, the equations of motion of the full turbine blade model are reduced to a single sector model by exploiting the concept of cyclic symmetry boundary condition for a periodic structure. Implementation of the developed scheme in solving the equations of motion is proved to be effective and significant reduction in time is achieved without loss of accuracy.

Continuum Mechanics and Thermodynamics

The dynamic stiffness of a chemically and physically ageing rubber vibration isolator in the audi... more The dynamic stiffness of a chemically and physically ageing rubber vibration isolator in the audible frequency range is modelled as a function of ageing temperature, ageing time, actual temperature, time, frequency and isolator dimension. In particular, the dynamic stiffness for an axially symmetric, homogeneously aged rubber vibration isolator is derived by waveguides where the eigenmodes given by the dispersion relation for an infinite cylinder satisfying traction free radial surface boundary condition are matched to satisfy the displacement boundary conditions at the lateral surface ends of the finite rubber cylinder. The constitutive equations are derived in a companion paper (Part 1). The dynamic stiffness is calculated over the whole audible frequency range 20-20,000 Hz at several physical ageing times for a temperature history starting at thermodynamic equilibrium at +25 • C and exposed by a sudden temperature step down to −60 • C and at several chemical ageing times at temperature +25 • C with simultaneous molecular network scission and reformation. The dynamic stiffness results are displaying a strong frequency dependence at a short physical ageing time, showing stiffness magnitude peaks and troughs, and a strong physical ageing time dependence, showing a large stiffness magnitude increase with the increased physical ageing time, while the peaks and troughs are smoothed out. Likewise, stiffness magnitude peaks and troughs are frequency-shifted with increased chemical ageing time. The developed model is possible to apply for dynamic stiffness prediction of rubber vibration isolator over a broad audible frequency range under realistic environmental condition of chemical ageing, mainly attributed to oxygen exposure from outside and of physical ageing, primarily perceived at low-temperature steps.

Polymer Testing, 2005

The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on ... more The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on the compactibility characteristics and surface morphology of the compacted materials, with and without relaxation assists, by increasing compacting quantity and direction. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomena during the decompacting stage. Polyamide-11

Plastics, Rubber and Composites, 2012

Journal of Sound and Vibration, 2013

DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

The Journal of the Acoustical Society of America, 2003

The nonlinear, preload-dependent dynamic stiffness of a cylindrical vibration isolator is examine... more The nonlinear, preload-dependent dynamic stiffness of a cylindrical vibration isolator is examined via measurements and modeling within an audible frequency range covering 50 to 1000 Hz at various preloads. The stiffness is found to depend strongly on frequency-resulting in peaks and troughs, and on preload-particularly above 500 Hz. The problems of simultaneously modeling the rubber prestrain dependence and its audible short-term response are removed by adopting a nearly incompressible material model, being elastic in dilatation while displaying viscoelasticity in deviation. The latter exhibits a time strain separable relaxation tensor with a single function embodying its time dependence. This function is based on a continuous fractional order derivative model, the main advantage being the minimum number of parameters required to successfully model the rubber properties over a broad structure-borne sound frequency domain, while embodying a continuous distribution of relaxation time. The weak formulations corresponding to the stiffness problem are solved by an updated Lagrangian nonlinear finite-element procedure. The model and measurement results agree strikingly well with static and dynamic measurements throughout the whole frequency domain for the examined preloads.

Polymer testing, 2002

The frequency and temperature dependent noise radiation properties of constrained polymer layered... more The frequency and temperature dependent noise radiation properties of constrained polymer layered oil pans are examined through mobility and intensity measurements. Four metal/polymer/metal sandwich composites of varied thermoplastic elastomer systems of polystyrene-polybutadiene-polystyrene triblock copolymers are investigated within a wide frequency range covering 1000-5000 Hz, and over a wide temperature range covering 20-100°C, with results compared to those of an ordinary steel oil pan. The mobility and intensity are found to be strongly frequency and temperature dependent, displaying a substantial mobility reduction as compared to that of the ordinary pan, while using the constrained layer damping configurations at their maximum loss factor temperatures. However, the reduction of noise radiation is smaller than that of the mobility at those temperatures, mainly due to the increased radiation efficiency while adding damping materials.

Journal of Sound and Vibration, 2010

A novel constitutive model of magneto-sensitive rubber in the audible frequency range is presente... more A novel constitutive model of magneto-sensitive rubber in the audible frequency range is presented. Characteristics inherent to magneto-sensitive rubber within this dynamic regime are defined: magnetic sensitivity, amplitude dependence, elasticity and viscoelasticity. Prior to ...

Smart Materials and Structures, 2008

... Smart audio frequency energy flow control by magneto-sensitive rubber isolators Peter Blom an... more ... Smart audio frequency energy flow control by magneto-sensitive rubber isolators Peter Blom and Leif Kari The Marcus Wallenberg Laboratory for Sound and Vibration Research (MWL), Royal Institute of Technology, 100 44 Stockholm, Sweden E-mail: pblom@kth.se ...

A time domain non-linear model is presented to predict the dynamic stiffness of rubber isolators ... more A time domain non-linear model is presented to predict the dynamic stiffness of rubber isolators using a FE code. The problem of simultaneously modelling elastic, viscoelastic and friction contributions is removed by additively splitting them. Viscoelastic response is modelled via a fractional derivative model, while amplitude dependency is considered through Coulomb friction elements. Nevertheless, determination of the dynamic stiffness takes long time and requires large amount of memory, as well as the estimation of the transfer function between applied excitation and resulting forces at different frequency and amplitude values. This is why a frequency domain simplified procedure is also proposed to obtain the dynamic stiffness. The technique is based on providing a generalized Maxwell model with the adequate material data set, once the dynamic strain amplitude, to which the mount is subjected, is estimated from quasi-static strain values. The methodology has proved to be efficien...

This paper provides a creative approach on how to implement CDIO-techniques into a Engineering Ph... more This paper provides a creative approach on how to implement CDIO-techniques into a Engineering Physics program. A comparison is made between the Vehicle Engineering program and the Engineering Physics program at the Royal Institute of Technology (KTH), in order to establish what the grounds and potentials for implementing CDIO into a new program environment are. The Engineering Physics program is examined not only though the comparison but also through an indicatory survey performed with students, instructors and representatives from the industry. This is done in order to map the perceived nature of the program. Furthermore, these potentials are explored from the view of the Engineering Physics program at KTH, and implementation strategies are suggested and elaborated in accordance with derived results and indicators, using modelling and simulation as a ground for an abstract product orientation.

A shape factor based non-linear model of a rubber cylinder's tem-perature and preload depend... more A shape factor based non-linear model of a rubber cylinder's tem-perature and preload dependent static stiffness is presented. The in-fluence of temperature, precom-pression, material parameters, cy-linder length and diameter, are in-vestigated; with the motion split into a homogeneous thermal expansion including a globally equivalent pre-load deformation. Stiffness depends strongly on preload, particularly in larger shape factors, and on tem-perature. The model proves superior to traditional work in typical shape factors, with results close to those of finite element models. Zur nichtlinearen temperatur-abhaÈngigen Steifigkeit von

Constitutive Models for Rubber IV, 2017

Effective engineering formula for torsion stiffness of a long rubber bush in the frequency domain... more Effective engineering formula for torsion stiffness of a long rubber bush in the frequency domain including amplitude dependence is presented. The classical theory of elasticity is the tool used to ...

Measurement, 2017

A novel test rig design is presented which enables detailed studies of the three force components... more A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for the tread block-substrate contact and enables force measurements at high rolling speeds with a high signal-to-noise ratio. Measurements of the rolling contact forces are presented for different values of rolling velocity, static pre-load and acceleration. It is demonstrated that this test rig provides results which contribute to the understanding of tyre-road interaction and can be used as input to modelling-based development of both tyres and roads aiming for improved handling, safety, energy efficiency and comfort.

Constitutive Models for Rubber VI, 2009

The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation... more The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated, where influences of excitation position, amplitude, frequenc ...

Journal of Applied Mechanics, 2008

A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitu... more A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitude are taken into account through fractional order viscoelasticity and plasticity, respectively. The problem of simultaneously modeling elastic, viscoelastic, and friction contributions is removed by additively splitting them. Due to the fractional order representation mainly, the number of parameters of the model remains low, rendering an easy fitting of the values from tests on material samples. The proposed model is implemented in a general-purpose finite element (FE) code. Since commercial FE codes do not contain any suitable constitutive model that represents the full dynamic behavior of rubber compounds (including frequency and amplitude dependent effects), a simple approach is used based on the idea of adding stress contributions from simple constitutive models: a mesh overlay technique, whose basic idea is to create a different FE model for each material definition (fractional de...

Polymers

A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temper... more 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 ...

Materials

Traditional vibration isolation systems, using natural rubber vibration isolators, display large ... more Traditional vibration isolation systems, using natural rubber vibration isolators, display large peaks for the energy flow from the machine source and into the receiving foundation, at the unavoidable rigid body resonance frequencies. However, tough, doubly cross-linked, single polymer network hydrogels, with both chemical and physical cross-links, show a high loss factor over a specific frequency range, due to the intensive adhesion–deadhesion activities of the physical cross-links. In this study, vibration isolators, made of this tough hydrogel, are theoretically applied in a realistic vibration isolation system, displaying several rigid body resonances and various energy flow transmission paths. A simulation model is developed, that includes a suitable stress–strain model, and shows a significant reduction of the energy flow peaks. In particular, the reduction is more than 30 times, as compared to the corresponding results using the natural rubber. Finally, it is shown that a sig...

Materials

Tough, doubly cross-linked, single polymer network hydrogels with both chemical and physical cros... more Tough, doubly cross-linked, single polymer network hydrogels with both chemical and physical cross-links display a high loss factor of the shear modulus over a broad frequency range. Physically, the high loss factor is resulting from the intensive adhesion–deadhesion activities of the physical cross-links. A high loss factor is frequently required by the optimization processes for optimal performance of a primary vibration system while adopting a dynamic vibration absorber, in particular while selecting a larger dynamic vibration absorber mass in order to avoid an excess displacement amplitude of the dynamic vibration absorber springs. The novel idea in this paper is to apply this tough polymer hydrogel as a dynamic vibration absorber spring material. To this end, a simulation model is developed while including a suitable constitutive viscoelastic material model for doubly cross-linked, single polymer network polyvinyl alcohol hydrogels with both chemical and physical cross-links. I...

Continuum Mechanics and Thermodynamics

An effective fractional derivative-based visco-elastic model of tough, doubly cross-linked, singl... more An effective fractional derivative-based visco-elastic model of tough, doubly cross-linked, single-network polyvinyl alcohol (PVA) hydrogels, embodying both chemical and physical cross-links, is developed using a Mittag–Leffler relaxation function of order 1/2 while applying only three material parameters that are physically quantifiable, namely frequency for maximum loss modulus, equilibrium elastic modulus and relaxation intensity. The resulting 3-parameter shear modulus model is possible to additively split into chemical and physical parts; the split being the study focus. Physical explanations of the visco-elastic low-, mid- and high-frequency range properties, and their transitions between the frequency ranges, are given mainly in terms of the permanent chemical cross-links and the distinct adhesion–deadhesion processes of the transient physical cross-links. The latter are running from an associated Rouse mode low-frequency behaviour through a maximum adhesion–deadhesion dissip...

Computers & Structures

An analytical expression is formulated to compute the Jacobian matrix for 3D friction contact mod... more An analytical expression is formulated to compute the Jacobian matrix for 3D friction contact modelling that efficiently evaluates the matrix while computing the friction contact forces in the time domain by means of the alternate frequency time domain approach. The developed expression is successfully used for the calculation of the friction damping on a turbine blade with shroud contact interface having an arbitrary 3D relative displacement. The analytical expression drastically reduces the computation time of the Jacobian matrix with respect to the classical finite difference method, with many points at the contact interface. Therefore, it also significantly reduces the overall computation time for the solution of the equations of motion, since the formulation of the Jacobian matrix is the most time consuming step in solving the large set of nonlinear algebraic equations when a finite difference approach is employed. The equations of motion are formulated in the frequency domain using the multiharmonic balance method to accurately capture the nonlinear contact forces and displacements. Moreover, the equations of motion of the full turbine blade model are reduced to a single sector model by exploiting the concept of cyclic symmetry boundary condition for a periodic structure. Implementation of the developed scheme in solving the equations of motion is proved to be effective and significant reduction in time is achieved without loss of accuracy.

Continuum Mechanics and Thermodynamics

The dynamic stiffness of a chemically and physically ageing rubber vibration isolator in the audi... more The dynamic stiffness of a chemically and physically ageing rubber vibration isolator in the audible frequency range is modelled as a function of ageing temperature, ageing time, actual temperature, time, frequency and isolator dimension. In particular, the dynamic stiffness for an axially symmetric, homogeneously aged rubber vibration isolator is derived by waveguides where the eigenmodes given by the dispersion relation for an infinite cylinder satisfying traction free radial surface boundary condition are matched to satisfy the displacement boundary conditions at the lateral surface ends of the finite rubber cylinder. The constitutive equations are derived in a companion paper (Part 1). The dynamic stiffness is calculated over the whole audible frequency range 20-20,000 Hz at several physical ageing times for a temperature history starting at thermodynamic equilibrium at +25 • C and exposed by a sudden temperature step down to −60 • C and at several chemical ageing times at temperature +25 • C with simultaneous molecular network scission and reformation. The dynamic stiffness results are displaying a strong frequency dependence at a short physical ageing time, showing stiffness magnitude peaks and troughs, and a strong physical ageing time dependence, showing a large stiffness magnitude increase with the increased physical ageing time, while the peaks and troughs are smoothed out. Likewise, stiffness magnitude peaks and troughs are frequency-shifted with increased chemical ageing time. The developed model is possible to apply for dynamic stiffness prediction of rubber vibration isolator over a broad audible frequency range under realistic environmental condition of chemical ageing, mainly attributed to oxygen exposure from outside and of physical ageing, primarily perceived at low-temperature steps.

Polymer Testing, 2005

The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on ... more The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on the compactibility characteristics and surface morphology of the compacted materials, with and without relaxation assists, by increasing compacting quantity and direction. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomena during the decompacting stage. Polyamide-11

Plastics, Rubber and Composites, 2012

Journal of Sound and Vibration, 2013

DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

The Journal of the Acoustical Society of America, 2003

The nonlinear, preload-dependent dynamic stiffness of a cylindrical vibration isolator is examine... more The nonlinear, preload-dependent dynamic stiffness of a cylindrical vibration isolator is examined via measurements and modeling within an audible frequency range covering 50 to 1000 Hz at various preloads. The stiffness is found to depend strongly on frequency-resulting in peaks and troughs, and on preload-particularly above 500 Hz. The problems of simultaneously modeling the rubber prestrain dependence and its audible short-term response are removed by adopting a nearly incompressible material model, being elastic in dilatation while displaying viscoelasticity in deviation. The latter exhibits a time strain separable relaxation tensor with a single function embodying its time dependence. This function is based on a continuous fractional order derivative model, the main advantage being the minimum number of parameters required to successfully model the rubber properties over a broad structure-borne sound frequency domain, while embodying a continuous distribution of relaxation time. The weak formulations corresponding to the stiffness problem are solved by an updated Lagrangian nonlinear finite-element procedure. The model and measurement results agree strikingly well with static and dynamic measurements throughout the whole frequency domain for the examined preloads.

Polymer testing, 2002

The frequency and temperature dependent noise radiation properties of constrained polymer layered... more The frequency and temperature dependent noise radiation properties of constrained polymer layered oil pans are examined through mobility and intensity measurements. Four metal/polymer/metal sandwich composites of varied thermoplastic elastomer systems of polystyrene-polybutadiene-polystyrene triblock copolymers are investigated within a wide frequency range covering 1000-5000 Hz, and over a wide temperature range covering 20-100°C, with results compared to those of an ordinary steel oil pan. The mobility and intensity are found to be strongly frequency and temperature dependent, displaying a substantial mobility reduction as compared to that of the ordinary pan, while using the constrained layer damping configurations at their maximum loss factor temperatures. However, the reduction of noise radiation is smaller than that of the mobility at those temperatures, mainly due to the increased radiation efficiency while adding damping materials.

Journal of Sound and Vibration, 2010

A novel constitutive model of magneto-sensitive rubber in the audible frequency range is presente... more A novel constitutive model of magneto-sensitive rubber in the audible frequency range is presented. Characteristics inherent to magneto-sensitive rubber within this dynamic regime are defined: magnetic sensitivity, amplitude dependence, elasticity and viscoelasticity. Prior to ...

Smart Materials and Structures, 2008

... Smart audio frequency energy flow control by magneto-sensitive rubber isolators Peter Blom an... more ... Smart audio frequency energy flow control by magneto-sensitive rubber isolators Peter Blom and Leif Kari The Marcus Wallenberg Laboratory for Sound and Vibration Research (MWL), Royal Institute of Technology, 100 44 Stockholm, Sweden E-mail: pblom@kth.se ...