Dan-andrei Serban | Politehnica University of Timisoara (original) (raw)
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Papers by Dan-andrei Serban
Computational Materials Science, 2012
The use of numerical simulations based on finite element analysis has become essential in designi... more The use of numerical simulations based on finite element analysis has become essential in designing new products, bridging basic material properties (obtained in various tests performed on material's specimens) and a product behaviour. Such simulations can account for a real geometry of designed components that can cause stress concentration as well as for in-service loading and/or environmental conditions. A challenging aspect for numerical simulations is anticipating the behaviour of advanced materials such as polymers and composites, demonstrating, i. a., anisotropy, heterogeneity and timedependent properties as well as non-trivial damage and fracture scenarios. The first step in achieving a valid product simulation is to perform simulations that can accurately reproduce the experimental results. The present work analyzes a possibility to simulate a response of a hyperelastic material (a semi-crystalline thermoplastic polymer) to monotonous uniaxial tensile loadings considering different strain-energy density functions as well as uniaxial cyclic loading using the commercial software ABAQUS/ CAE. The former case focuses on a stress-strain curve while the latter one deals with energy hysteresis, strain softening and strain hardening. The performed simulations produce good results for monotonous loading, but simulations of cyclic loading can only partially reproduce the material's behaviour.
![Research paper thumbnail of Corrigendum to ‘Tensile properties of semi-crystalline thermoplastic polymers: Effects of temperature and strain rates’ [Polymer Testing 32/2 (2013) 413–425]](https://attachments.academia-assets.com/43702079/thumbnails/1.jpg)
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Polymer Testing, 2013
This work deals with the study of temperature and time dependency of tensile properties of a PA 1... more This work deals with the study of temperature and time dependency of tensile properties of a PA 12-based polymer. The range of variation of parameters in experiments was linked to inservice conditions of components manufactured with this material (temperature interval from À25 C to 50 C and average strain-rate magnitudes from 0.00028 s À1 to 9.4 s À1 ). For tests with different temperatures and low speed, an electro-mechanical machine, Zwick Z250, equipped with an incremental extensometer was used. To study the effect of strain rate at medium speeds, a servo-hydraulic system, Schenk PC63M, equipped with a straingauge extensometer was used, while at high speeds a servo-hydraulic machine, Instron VHS 160/20, equipped with a high-speed camera for strain evaluation by digital image correlation was employed. The changes of the rate of deformation with strain as well as elastic modulus variation with strain were studied. An increase in the elastic modulus and yield strength was observed with a drop in temperature and an increase in the strain-rate, temperature having a stronger influence on the variation of mechanical properties. The collected data was assembled in an elasto-plastic material model for finite-element simulations capable of rendering temperature-and strain-rate-dependency. The model was implemented in the commercial software Abaqus, yielding accurate results for all tests.
Iranian Polymer Journal, 2015
cell geometries provide good accordance with experimental data for higher relative density materi... more cell geometries provide good accordance with experimental data for higher relative density materials.
Procedia Engineering, 2015
Computational Materials Science, 2012
The use of numerical simulations based on finite element analysis has become essential in designi... more The use of numerical simulations based on finite element analysis has become essential in designing new products, bridging basic material properties (obtained in various tests performed on material's specimens) and a product behaviour. Such simulations can account for a real geometry of designed components that can cause stress concentration as well as for in-service loading and/or environmental conditions. A challenging aspect for numerical simulations is anticipating the behaviour of advanced materials such as polymers and composites, demonstrating, i. a., anisotropy, heterogeneity and timedependent properties as well as non-trivial damage and fracture scenarios. The first step in achieving a valid product simulation is to perform simulations that can accurately reproduce the experimental results. The present work analyzes a possibility to simulate a response of a hyperelastic material (a semi-crystalline thermoplastic polymer) to monotonous uniaxial tensile loadings considering different strain-energy density functions as well as uniaxial cyclic loading using the commercial software ABAQUS/ CAE. The former case focuses on a stress-strain curve while the latter one deals with energy hysteresis, strain softening and strain hardening. The performed simulations produce good results for monotonous loading, but simulations of cyclic loading can only partially reproduce the material's behaviour.
Computational Materials Science, 2012
Mechanical behaviours and properties of polymers under dynamic loading conditions differ signific... more Mechanical behaviours and properties of polymers under dynamic loading conditions differ significantly from those under quasi-static loads. Consequently, for dynamic numerical analysis, a linear elastic/hyperelastic material model has its limitations and can produce inaccurate results. In order to obtain an adequate response to high-speed loading in simulations, a viscoelastic material model has been developed.
Key Engineering Materials, 2014
ABSTRACT In recent years, advances in material testing equipment caused the determination of mech... more ABSTRACT In recent years, advances in material testing equipment caused the determination of mechanical properties by means of three-point bending tests to lose ground in detriment to more accurate tensile tests. However, if components undergo bending deformation in service, the identification of the materials flexural behaviour is essential. The investigated material is a thermoplastic polymer, test specimens being cut in prismatic shapes from injected sheets, which present a variation in properties due to cooling conditions. This paper presents results of three-point bending tests with emphasis on the influence of strain rate and anisotropy on flexural strength and chord modulus. Results show an increase in flexural properties with strain rate and a considerable influence of anisotropy on mechanical properties.
Solid State Phenomena, 2012
When subjected to external loading, polymeric materials behave in a manner intermediate between e... more When subjected to external loading, polymeric materials behave in a manner intermediate between elastic solids and viscous fluids. Their mechanical properties depend on a material's viscous flow, which, in turn, is influenced by (i) temperature, with its different magnitudes determining a ductile or brittle behaviour and (ii) time, through the effect of a deformation rate and long-term relaxation. Short-term viscoelastic properties (loss and storage moduli) of a studied semi-crystalline thermoplastic polymer were obtained using Dynamic Mechanical Analysis, while its long-term viscoelastic properties (compliances) were determined using creep tests.
Key Engineering Materials, 2014
Polyurethane (PUR) foam materials represent a class of materials widely used for impact protectio... more Polyurethane (PUR) foam materials represent a class of materials widely used for impact protection and energy absorption. This paper presents a characterization of different rigid PUR foams under compressive impact loading by means of energy absorption and efficiency diagrams. Compressive properties were investigated on cubic specimens on the foams’ rise direction at room temperature with a loading rate of 3.09 m/s for three different closed-cell foams with densities of 100 kg/m3, 160 kg/m3 and 300 kg/m3 respectively. Experimental results show that the compression modulus, yield stress and plateau stress increase with density. Most of the energy is absorbed in the plateau region because of the cell deformation associated with this phenomenon, allowing greater absorption of impact energy at nearly constant load. Authors have found that both the energy absorption and efficiency diagrams are consistent and present similar results for studied foams.
ISI Journals by Dan-andrei Serban
This paper deals with evaluating the elastic response of several micromechanical structures used ... more This paper deals with evaluating the elastic
response of several micromechanical structures used for simulating cellular materials under compression. For this
study polyurethane rigid foams were investigated, having
three relative densities: 0.085, 0.124 and 0.256. Their
microstructure was analysed using SEM images, determining
four types of cells that were consequently designed
using specialized CAD software: square cells with circular,
quadratic and/or hexagonal orifices and hexagonal
cells. An interdependent variation of the cells’ geometrical
parameters of the proposed structures was determined to
obtain geometrical variations at a required relative density.
Finite element analysis simulations were performed on
the designed microstructural models using a linear elastic
material model for the cell struts, resulting in the variation
of the elastic modulus of the structure with the variation in
cell geometry parameters. The final objective of this work
was to determine anisotropic bi-dimensional micromechanical
models for the studied cellular material that provides
accurate results in compression on both loading directions.
The anisotropic models for the proposed cell structures
were obtained by generating irregular geometries which
provided extra variables for the cell geometry parameters.
It was determined that some cell geometries are suitable
for simulating lower relative density materials while other cell geometries provide good accordance with experimental
data for higher relative density materials.
Computational Materials Science, 2012
The use of numerical simulations based on finite element analysis has become essential in designi... more The use of numerical simulations based on finite element analysis has become essential in designing new products, bridging basic material properties (obtained in various tests performed on material's specimens) and a product behaviour. Such simulations can account for a real geometry of designed components that can cause stress concentration as well as for in-service loading and/or environmental conditions. A challenging aspect for numerical simulations is anticipating the behaviour of advanced materials such as polymers and composites, demonstrating, i. a., anisotropy, heterogeneity and timedependent properties as well as non-trivial damage and fracture scenarios. The first step in achieving a valid product simulation is to perform simulations that can accurately reproduce the experimental results. The present work analyzes a possibility to simulate a response of a hyperelastic material (a semi-crystalline thermoplastic polymer) to monotonous uniaxial tensile loadings considering different strain-energy density functions as well as uniaxial cyclic loading using the commercial software ABAQUS/ CAE. The former case focuses on a stress-strain curve while the latter one deals with energy hysteresis, strain softening and strain hardening. The performed simulations produce good results for monotonous loading, but simulations of cyclic loading can only partially reproduce the material's behaviour.
Polymer Testing, 2013
This work deals with the study of temperature and time dependency of tensile properties of a PA 1... more This work deals with the study of temperature and time dependency of tensile properties of a PA 12-based polymer. The range of variation of parameters in experiments was linked to inservice conditions of components manufactured with this material (temperature interval from À25 C to 50 C and average strain-rate magnitudes from 0.00028 s À1 to 9.4 s À1 ). For tests with different temperatures and low speed, an electro-mechanical machine, Zwick Z250, equipped with an incremental extensometer was used. To study the effect of strain rate at medium speeds, a servo-hydraulic system, Schenk PC63M, equipped with a straingauge extensometer was used, while at high speeds a servo-hydraulic machine, Instron VHS 160/20, equipped with a high-speed camera for strain evaluation by digital image correlation was employed. The changes of the rate of deformation with strain as well as elastic modulus variation with strain were studied. An increase in the elastic modulus and yield strength was observed with a drop in temperature and an increase in the strain-rate, temperature having a stronger influence on the variation of mechanical properties. The collected data was assembled in an elasto-plastic material model for finite-element simulations capable of rendering temperature-and strain-rate-dependency. The model was implemented in the commercial software Abaqus, yielding accurate results for all tests.
Iranian Polymer Journal, 2015
cell geometries provide good accordance with experimental data for higher relative density materi... more cell geometries provide good accordance with experimental data for higher relative density materials.
Procedia Engineering, 2015
Computational Materials Science, 2012
The use of numerical simulations based on finite element analysis has become essential in designi... more The use of numerical simulations based on finite element analysis has become essential in designing new products, bridging basic material properties (obtained in various tests performed on material's specimens) and a product behaviour. Such simulations can account for a real geometry of designed components that can cause stress concentration as well as for in-service loading and/or environmental conditions. A challenging aspect for numerical simulations is anticipating the behaviour of advanced materials such as polymers and composites, demonstrating, i. a., anisotropy, heterogeneity and timedependent properties as well as non-trivial damage and fracture scenarios. The first step in achieving a valid product simulation is to perform simulations that can accurately reproduce the experimental results. The present work analyzes a possibility to simulate a response of a hyperelastic material (a semi-crystalline thermoplastic polymer) to monotonous uniaxial tensile loadings considering different strain-energy density functions as well as uniaxial cyclic loading using the commercial software ABAQUS/ CAE. The former case focuses on a stress-strain curve while the latter one deals with energy hysteresis, strain softening and strain hardening. The performed simulations produce good results for monotonous loading, but simulations of cyclic loading can only partially reproduce the material's behaviour.
Computational Materials Science, 2012
Mechanical behaviours and properties of polymers under dynamic loading conditions differ signific... more Mechanical behaviours and properties of polymers under dynamic loading conditions differ significantly from those under quasi-static loads. Consequently, for dynamic numerical analysis, a linear elastic/hyperelastic material model has its limitations and can produce inaccurate results. In order to obtain an adequate response to high-speed loading in simulations, a viscoelastic material model has been developed.
Key Engineering Materials, 2014
ABSTRACT In recent years, advances in material testing equipment caused the determination of mech... more ABSTRACT In recent years, advances in material testing equipment caused the determination of mechanical properties by means of three-point bending tests to lose ground in detriment to more accurate tensile tests. However, if components undergo bending deformation in service, the identification of the materials flexural behaviour is essential. The investigated material is a thermoplastic polymer, test specimens being cut in prismatic shapes from injected sheets, which present a variation in properties due to cooling conditions. This paper presents results of three-point bending tests with emphasis on the influence of strain rate and anisotropy on flexural strength and chord modulus. Results show an increase in flexural properties with strain rate and a considerable influence of anisotropy on mechanical properties.
Solid State Phenomena, 2012
When subjected to external loading, polymeric materials behave in a manner intermediate between e... more When subjected to external loading, polymeric materials behave in a manner intermediate between elastic solids and viscous fluids. Their mechanical properties depend on a material's viscous flow, which, in turn, is influenced by (i) temperature, with its different magnitudes determining a ductile or brittle behaviour and (ii) time, through the effect of a deformation rate and long-term relaxation. Short-term viscoelastic properties (loss and storage moduli) of a studied semi-crystalline thermoplastic polymer were obtained using Dynamic Mechanical Analysis, while its long-term viscoelastic properties (compliances) were determined using creep tests.
Key Engineering Materials, 2014
Polyurethane (PUR) foam materials represent a class of materials widely used for impact protectio... more Polyurethane (PUR) foam materials represent a class of materials widely used for impact protection and energy absorption. This paper presents a characterization of different rigid PUR foams under compressive impact loading by means of energy absorption and efficiency diagrams. Compressive properties were investigated on cubic specimens on the foams’ rise direction at room temperature with a loading rate of 3.09 m/s for three different closed-cell foams with densities of 100 kg/m3, 160 kg/m3 and 300 kg/m3 respectively. Experimental results show that the compression modulus, yield stress and plateau stress increase with density. Most of the energy is absorbed in the plateau region because of the cell deformation associated with this phenomenon, allowing greater absorption of impact energy at nearly constant load. Authors have found that both the energy absorption and efficiency diagrams are consistent and present similar results for studied foams.
This paper deals with evaluating the elastic response of several micromechanical structures used ... more This paper deals with evaluating the elastic
response of several micromechanical structures used for simulating cellular materials under compression. For this
study polyurethane rigid foams were investigated, having
three relative densities: 0.085, 0.124 and 0.256. Their
microstructure was analysed using SEM images, determining
four types of cells that were consequently designed
using specialized CAD software: square cells with circular,
quadratic and/or hexagonal orifices and hexagonal
cells. An interdependent variation of the cells’ geometrical
parameters of the proposed structures was determined to
obtain geometrical variations at a required relative density.
Finite element analysis simulations were performed on
the designed microstructural models using a linear elastic
material model for the cell struts, resulting in the variation
of the elastic modulus of the structure with the variation in
cell geometry parameters. The final objective of this work
was to determine anisotropic bi-dimensional micromechanical
models for the studied cellular material that provides
accurate results in compression on both loading directions.
The anisotropic models for the proposed cell structures
were obtained by generating irregular geometries which
provided extra variables for the cell geometry parameters.
It was determined that some cell geometries are suitable
for simulating lower relative density materials while other cell geometries provide good accordance with experimental
data for higher relative density materials.