TY - GEN A1 - Schob, Daniela A1 - Roszak, Robert A1 - Sagradov, Ilja A1 - Sparr, Holger A1 - Kupsch, Andreas A1 - Leonard, Fabien A1 - Müller, Bernd R. A1 - Bruno, Giovanni T1 - Experimental and numerical simulation of material and damage behaviour of 3d printed polyamide 12 under quasi-static-loading T2 - Archives of Mechanics N2 - In order to characterise the material and damage behaviour of additively manufactured polyamide 12 (PA12) under quasi-static load and to implement it in a numerical model, experiments under quasi-static load as well as microstructural investigations were carried out. Selective laser sintering (SLS) was used as the manufacturing process. For the classification of the material behaviour, quasi-static cyclic tests with holding times as well as tensile tests were performed. X-ray refraction and computed tomography (CT) were used to investigate the damage behaviour. The Chaboche model, which has already been applied for metallic materials under thermomechanical loading, served as the basis for the selection of the numerical material model. The same procedure was used for the selection of the damage model, where the Gurson–Tvergaard–Needleman (GTN) model was chosen, which was already used for porous metallic materials. The Chaboche model shows very good agreement with experimental results. Furthermore, the coupling with the GTN model allows a very good modelling of the damage behaviour. Finally, it could be shown that the selected models are suitable to simulate the material and damage behaviour of 3D printed PA12. KW - Polyamide 12 KW - 3D printing KW - Viscoplastic KW - Chaboche model KW - Damage KW - GTN model KW - X-ray refraction KW - Computed tomography Y1 - 2019 UR - https://am.ippt.pan.pl/am/article/viewFile/v71p507/pdf U6 - https://doi.org/10.24423/aom.3162 SN - 0373-2029 VL - 71 IS - 4-5 SP - 507 EP - 526 ER - TY - GEN A1 - Sparr, Holger A1 - Roszak, Robert A1 - Sagradov, Ilja A1 - Schob, Daniela A1 - Ziegenhorn, Matthias T1 - Thermo-viscoplastic material modelling for self-heating loads and its experimental verification T2 - Technische Mechanik N2 - The paper examines a modelling approach for thermomechanically coupled problems and an experimental concept for a material law validation and verification for self-heating with small to moderate temperature ranges. The study compares two different model formulations and is generally applicable to a variety of material classes. One model is based on a rheological network with an extension for dissipative deformation below the elastic limit. The other model operates without a yield condition. Both models are applied to published experimental data in terms of rate-independent behaviour and the evaluation is carried out on stress-strain-level, temperature evolution and the energy transformation ratio. Furthermore the two models are applied to a strain rate-dependent load case conducted at our institute discussing the same entities. It is pointed out, that the approach of a thermomechanical analysis is valuable and informative to assess the observed deformation processes and to describe the material behaviour with a thermodynamically valid parameter set. KW - Thermomechanics KW - self–heating KW - viscoplasticity KW - energy transformation ratio KW - thermography Y1 - 2020 U6 - https://doi.org/10.24352/UB.OVGU-2020-015 SN - 2199-9244 SN - 0232-3869 VL - 40 IS - 1 SP - 66 EP - 76 ER - TY - GEN A1 - Schob, Daniela A1 - Sagradov, Ilja A1 - Roszak, Robert A1 - Sparr, Holger A1 - Franke, Rainer A1 - Ziegenhorn, Matthias A1 - Kupsch, Andreas A1 - Leonard, Fabien A1 - Müller, Bernd R. A1 - Bruno, Giovanni T1 - Experimental determination and numerical simulation of material and damage behaviour of 3d printed polyamide 12 under cyclic loading T2 - Engineering Fracture Mechanics N2 - The material and damage behaviour of additively manufactured polyamide 12 under cyclic loading was characterized by cyclic tests and microstructure analysis by using microscopy, X-ray refraction, and computed tomography. The results were used to determine parameters for the viscoplastic material model by Chaboche and a damage model by Gurson-Tvergaard-Needleman. The temperature was monitored during the experiments and the self-heating effect was observed. By including this effect, a higher accuracy could be achieved with the results of mechanical experiments. KW - 3D printing Polyamide 12 KW - Chaboche model KW - GTN model KW - Material and damage behaviour KW - X-ray refraction KW - computed tomography Y1 - 2020 U6 - https://doi.org/10.1016/j.engfracmech.2019.106841 SN - 0013-7944 VL - 229 ER - TY - GEN A1 - Sagradov, Ilja A1 - Schob, Daniela A1 - Roszak, Robert A1 - Maasch, Philipp A1 - Sparr, Holger A1 - Ziegenhorn, Matthias T1 - Experimental investigation and numerical modelling of 3D printed polyamide 12 with viscoplasticity and a crack model at different strain rates T2 - Materials Today Communications N2 - This contribution presents an investigation of strain rate dependent behaviour for selective laser sintered polyamide 12. Two different cases are considered: a strain rate change within tensile loading and a relaxation test incorporating a strain rate change after each holding time section. For the simulation of material behaviour the material model of Bodner-Partom and Chaboche were used. The damage behaviour was considered by the Lemaitre crack model. Thereby it was determined which numerical model is more suitable to reproduce the strain rate-dependent behaviour. Tensile and relaxation tests at constant speeds served as the basis for these investigations. KW - SLS-PA12 KW - Rate-dependent Chaboche model KW - Bodner-Partom model KW - Lemaitre Y1 - 2020 UR - https://www.sciencedirect.com/science/article/abs/pii/S2352492820325538 U6 - https://doi.org/10.1016/j.mtcomm.2020.101542 SN - 2352-4928 VL - 25 ER -