Robust Numerical Resolution of Nakamura Crystallization Kinetics

Lévy, Arthur

doi:10.11648/j.ijtam.20170304.13

Cited by 17 publications

(21 citation statements)

References 20 publications

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“…As has been shown in [17], min = 1e − 6 and below are suitable nucleation values. If min increases, the prediction of the time of full crystallization decreases since it acts as a nucleation value.…”

Section: Crystallization Modelmentioning

confidence: 89%

Modeling crystallization kinetics for selective laser sintering of polyamide 12

2021

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Selective laser sintering (SLS) of polymers represents a widely used additive manufacturing process, where the part quality depends highly on the present thermal conditions. One distinct feature of SLS is the existence of separate temperature regions for melting and crystallization (solidification) and that the process optimally operates within said regions. Typically a crystallization model, such as the Nakamura model, is used to predict the degree of crystallization as a function of temperature and time. One limitation of this model is the inability to compute negative rates of the crystallization degree during remelting. As we will show in this work, such an extension is necessary, considering the varying temperature fields appearing in SLS. To this end, an extension is proposed and analyzed in detail. Furthermore, a dependency of the temperature and crystallization fields on the size of geometrical features is presented.

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Section: Crystallization Modelmentioning

confidence: 89%

Modeling crystallization kinetics for selective laser sintering of polyamide 12

2021

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“…Enthalpy method: The enthalpy method solves the heat equation in terms of enthalpy variation where the enthalpy of the phase change material has been calculated from the values of Cp. Crystallization kinetics method: The crystallization kinetics model has been developed in our LTeN [6] laboratory. This numerical model is used to simulate the crystallization of phase change material with a crystallization kinetic.…”

Section: Numerical Modeling By Finite Element Methodsmentioning

confidence: 99%

Hybrid Analytical and Finite Element Simulation of a Latent Heat Storage Exchanger: Comparison of Heat Transfer Models for Enhanced Thermal Conductivity Phase Change Material

Jadal

Delaunay

Soto

et al. 2018

International Heat Transfer Conference 16

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In order to cut down the computing time, a simplified method for heat transfer analysis within a multi-tube and multi-plate latent heat storage exchanger is proposed. This method associates a 2D Finite Element method to solve energy equation within each plate and an analytical model to link the plates between them. Different formulations of the energy equation have been tested and compared with experimental results on a simple configuration. Enthalpy formulation, temperature dependent specific heat method, and source term of crystallization associated to kinetic equation method are the different options studied. The limitations of each methods is then exhibited.

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“…Therefore, along with the thermal history of the printed model, the semi-crystalline polymer model (PP) considered in this study was also driven by the polymer crystallization kinetics. This was achieved by modifying and incorporating the crystallization physics that was developed by Levy [ 26 , 27 ]. The thermo-mechanical properties of PP were expressed as a function of temperature (T), as was reported in the past that thermo-mechanical properties (

) are highly influenced by the temperature gradient of the system and the degree of crystallization [ 25 , 36 ].…”

Section: Modelingmentioning

confidence: 99%

“…Here, t is time, n is the Avrami index, and K ( T ) represents the Nakamura crystallization kinetics’ function derived from Avrami’s isothermal kinetics. Koscher et al performed DSC experiments for iso-thermal and non-iso thermal conditions and proposed K ( T ) as [ 26 , 36 , 37 ]:

…”

Section: Modelingmentioning

confidence: 99%

“…The polymers of the study were printed using FDM, simulated via COMSOL Multiphysics software, and validated experimentally. Since crystallinity is a significant factor in semi-crystalline polymers, crystallization kinetics that was developed by Levy A. was modified and incorporated into this study for semi-crystalline polymer analysis [ 26 , 27 ]. Along with the crystalline kinetics, the thermo-mechanical properties were also taken into consideration.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Ambient Temperature on Part Distortion: A Simulation Study on Amorphous and Semi-Crystalline Polymer

et al. 2022

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Semi-crystalline polymers develop higher amounts of residual stress and part distortion (warpage) compared to amorphous polymers due to their crystalline nature. Additionally, the FDM processing parameters such as ambient temperature play an important role in the resulting residual stresses and part distortion of the printed part. Hence, in this study, the effect of ambient temperature on the in-built residual stresses and warpage of amorphous acrylonitrile-butadiene-styrene (ABS) and semi-crystalline polypropylene (PP) polymers was investigated. From the results, it was observed that increasing the ambient temperature from 50 °C to 75 °C and further to 120 °C resulted in 0.22-KPa and 0.37-KPa decreases in residual stress of ABS, but no significant change in the amount of warpage. For PP, increasing ambient temperature from 50 °C to 75 °C led to a more considerable decrease in residual stress (0.5 MPa) and about 3% increase in warpage. Further increasing to 120 °C resulted in a noticeable 2 MPa decrease in residual stress and a 3.4% increase in warpage. Reduction in residual stress in both ABS and PP as a result of increasing ambient temperature was due to the reduced thermal gradients. The enhanced warpage in PP with increase in ambient temperature, despite the reduction in residual stress, was ascribed to crystallization and shrinkage.

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Robust Numerical Resolution of Nakamura Crystallization Kinetics

Cited by 17 publications

References 20 publications

Modeling crystallization kinetics for selective laser sintering of polyamide 12

Modeling crystallization kinetics for selective laser sintering of polyamide 12

Hybrid Analytical and Finite Element Simulation of a Latent Heat Storage Exchanger: Comparison of Heat Transfer Models for Enhanced Thermal Conductivity Phase Change Material

Influence of Ambient Temperature on Part Distortion: A Simulation Study on Amorphous and Semi-Crystalline Polymer

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