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Virtual additive manufacturing based on semicrystalline polymer polyetheretherketone (PEEK)

Bajerski Paweł, Pęcherski Ryszard B., Chudy Damian

Engineering Transactions

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2019

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Vol. 67, iss. 2

157--165

EN

Virtual additive manufacturing (AM) is one of the new directions of research that is necessary to improve AM technology. Abaqus/SIMULIA software allows to simulate the whole process using user subroutines to expand solver capabilities. Two of the most important subroutines are UepActivationVol and UMATHT. The UepActivationVol is related to an activation of elements in accordance with the defined path of the process. The second one the UMATHT is used to implement and combine thermal and crystallization process [2]. The presented investigations describe the dual crystallization kinetics model for considered high temperature thermoplastic material Polyetheretherketone (PEEK). Furthermore, it is shown how to analyse the overall process with use of Abaqus/SIMULIA software. The innovation of the presented approach lies in the proper interpreting of the G-Code from Computeraided manufacturing software (CAM), which is an input for the real machines dedicated to AM. The path (coordinates of discrete points) and time of particular steps of the manufacturing process are extracted from the G-Code and are included as input parameters in the simulation code. The discretized part is simplification of the Computer-aided design (CAD) geometry. The final results show the effect implemented in user subroutines. Additionally, Differential Scanning Calorimetry (DSC) test results are presented in order to calculate crystallization and melting parameters. The presented work is the basis of the following investigations covering prediction of residual stresses, volumetric shrinkage and deformations.

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Crystallization kinetics of polyamide 2200 in the modelling of additive manufacturing processes by FE analyses

Bajerski Paweł, Pęcherski Ryszard Bolesław, Chudy Damian, Jarecki Leszek

Engineering Transactions

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2019

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Vol. 67, iss. 3

301--309

EN

The thermoplastic polymers present amorphous or semi-crystalline structures which are very important factors in describing volumetric shrinkage. The thermoplastic materials are commonly used for production of daily life products, industrial or as the prototypes. Different techniques of manufacturing polymer structures are considered like: injection molding, extrusion, milling, additive manufacturing (AM). AM is a very fast developing field in the manufacturing and research. Unfortunately, components or prototypes made using the thermoplastic semi-crystalline materials in 3D techniques have quite low mechanical strength compared to the parts made by injection molding processes. It is caused by porosity obtained during the processing, as well as by fraction of crystallinity in the volume of the components. Additionally, the volumetric shrinkage is hard to predict without knowledge of its origin. Therefore, it is necessary to consider crystallization kinetics and the melting of the analysed materials. The investigations presented in this work concern the crystallization and melting model to be implemented in the finite element (FE) analyses. With use of the model, one can predict development of the structure during the real processes and, in the future, to control the warpage of the manufactured components.

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Thermal Degradation Behaviour and Kinetics of aged TNT-based Melt Cast Composition B

Singh Arjun, Sharma Tirupati Chander, Singh Vasundhara, Mukherjee Niladri

Central European Journal of Energetic Materials

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2019

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Vol. 16, no. 3

360--379

EN

In the present paper, three kinds of aged and freshly prepared 2,4,6-trinitrotoluene (TNT) based Composition B stockpiled, for a period of 20 and 32 years, were investigated for the effect of natural ageing on their thermal degradation behaviour and kinetic parameters. The properties investigated indicated that there was no significant change in the thermal stability of the samples aged under natural environmental conditions. The kinetic parameters were studied by means of the Kissinger method using the peak temperature at maximum reaction rate from DSC data, and the isoconversional Kissinger-Akahira-Sunnose (KAS) and ASTM E689 methods from TGA data. The apparent activation energies calculated by the Kissinger method were 173.8 kJ·mol–1 for fresh, 170.4 kJ·mol–1 for 20 y old and 187.1 kJ·mol–1 for 32 y old Composition B, respectively. The values calculated by the KAS method were found to be in the range 77.2-235.8 kJ·mol–1 for fresh Composition B, 75.7-224.0 kJ·mol–1 for 20 y old and 70.4-196.0 kJ·mol–1 for 30 y old Composition B, respectively. The activation energies obtained from the KAS methods are in good agreement and consistent with the isoconversional ASTM E689 kinetic method. The thermodynamic parameters, such the Gibbs free energy of activation (ΔG#), activation enthalpy (ΔH#) and activation entropy (ΔS#) for the formation of activated complexes were also studied and are discussed.