NOPR Collection: Special Issue on Evolution of Engineering, Technologies and Materials (Guest Editors: Dumitru Nedelcu, Jerzy Swider, María Eugenia Rabanal Jiménez & Fiqiri Hodaj)

Study of microindentation and differential scanning calorimetry of reinforced polyamide

Sun, 01 Jun 2014 00:00:00 GMT

Title: Study of microindentation and differential scanning calorimetry of reinforced polyamide Authors: Mindru, Teodor Daniel; Nedelcu, Dumitru Abstract: Polyamides comprise the largest family of plastics engineering with a very wide range of applications in many fields of activities. Characteristically polyamides are resistant to wear and abrasion, have good mechanical properties even at elevated temperatures, low permeability to gases and good chemical resistance. Samples are obtained by monocomponent injection using Taguchi experimental plan with six input factors and two levels of variation for each of them. The considered parameters inside the experiment are mold temperature, melt temperature, injection pressure, injection speed, cooling time (in mold) and injection time. This study presents some aspects of microindentation and differential scanning calorimetry for polyamide with 30% fiberglass and microsphere reinforcement. For microindentation experimental study, UMT-2 universal equipment (CETR-Center of Trybology, INC. USA) is used. It was also used a sensor by 2 kg, a maximum force of 15 N and indenter radius Rockwell type with diamond peak is 200 μm. The software package used indicates microhardness values and indentation reduced modulus and Young's modulus and it generates experiment graphs. Concerning the differential scanning calorimetry the experiments were performed on differential scanning calorimeter (DSC) type F3 Maia (supplied by Netzsch) in argon protective atmosphere. The temperature difference between sample and reference is measured and recorded as heat flow. Temperature is measured using three thermocouples, one indicating the sample temperature, the temperature set point second and final furnace temperature. DSC thermograms evaluation will be done with PROTEUS software. To determine the critical points of transformation, transformation starting temperature (onset), temperature when 50% of the change occurred (peak) and finally the transformation temperature (end) and will use the tangent method. The amount of heat dissipated (in the case of endothermic transformation)/absorbed (in the case of exothermic transformation) will be determined using a sigmoidal baseline (ΔH area). Page(s): 333-340

Precision forming of micro-sized piezoceramics with a high aspect ratio

Sun, 01 Jun 2014 00:00:00 GMT

Title: Precision forming of micro-sized piezoceramics with a high aspect ratio Authors: Jeon, Jae-Ho; Choi, Si-Young; Kim, Jong Hyun; Chang, Suk Sang Abstract: In order to fabricate micro-sized PMN-PT piezoceramics with an aspect ratio of 5 for 1-3 composites by injection molding process, two novel methods are developed depending on the size of samples. In the case of a sample with 700 μm in side length of the post, a cassette or monolithic mold is designed and made by machining. The injected samples in the cassette or monolithic mold are effectively separated from the mold by pushing ejecting pins. On the other hand, in the case of sample with 60 μm in side length of the post, PMMA polymer based sacrificial mold inserts are fabricated by using synchrotron radiation. After the injection of PMN-PT powder mixture into the mold inserts, instead of mechanical demolding, PMMA mold inserts are chemically dissolved into acetone. Heat-treating at 800°C in an oxygen atmosphere is more effective for removing organic binders than a conventional de-binding at 500°C in air. Finally, micrometer-scale PMN-PT piezoceramics with the aspect ratio of 5 are successfully fabricated by sintering at 1100°C for 10 h in air. Page(s): 329-332

Numerical modelling and experimental validation of the pneumatic powder injection into liquid alloys

Sun, 01 Jun 2014 00:00:00 GMT

Title: Numerical modelling and experimental validation of the pneumatic powder injection into liquid alloys Authors: Jezierski, Jan; Buliński, Zbigniew; Janerka, Krzysztof; Stawarz, Marcin; Kaczmarek, Konrad Abstract: The pneumatic powder injection is well-known and widely used with injection lances submerged into metal bath. However, sometimes better is to not introduce the lance below the liquid metal surface because of the metal splashing and introducing of gases into metal volume. In such a case non-submerged lance is used but the problem with particles jet penetration into the metal volume appears. This paper presents the results of the studies on the pneumatic powder injection with non-submerged lance. The high-speed camera recording of the model diphase jet leaving the lance is carried out. Then image analysis is performed to estimate real particles motion parameters. Furthermore, the jet cone is analysed to check its character of development and compared with the reported results in the literature. The results are obtained that the particles real velocity is smaller than calculated from typically used formulas. The same with cone angles – it seems to be different than quoted in the literature. Next stage is numerical modelling using AnSys software. The results were compared with the experiments and the model is adjusted. The next stage is ferroalloy “cold” injection and again the computer modelling. The last stage is FeSi injection into grey iron experiments. The analysis of the results is combined both with the laboratory results and modelling then compared with previous data. As a consequence the validated numerical model is obtained which can be helpful for the injection process planning in industrial conditions. Page(s): 322-328

Properties of Al₂O₃ and NiAlSi coatings obtained by atmospheric plasma spraying on 34CrNiMo₆ substrate

Sun, 01 Jun 2014 00:00:00 GMT

Title: Properties of Al₂O₃ and NiAlSi coatings obtained by atmospheric plasma spraying on 34CrNiMo₆ substrate Authors: Avram, Petru; Imbrea, Marius Stelian; Istrate, Bogdan; Strugaru, Sorin Iacob; Benchea, Marcelin; Munteanu, Corneliu Abstract: In military and mining industry are many machine elements which are subjected to thermal and structural analyses. Idlers must have a high wear resistance, because the functionality of the entire transmissions systems depends on them. Since the maintenance costs of the machines are very high, here we propose to improve the performances of the machine elements and also improve the physical, mechanical and chemical proprieties of those elements¹. We have chosen the steel type 34CrNiMo₆, MoCN class, STAS 691-880 as basic material and coated it with NiAlSi and Al₂O₃ powders. The prepared samples are analyzed by XRD, EDS and SEM. The NiAlSi and Al₂O₃ coating deposited on steel substrate, is dense, but on SEM analysis we discovered that it has some fine cracks on NiAlSi deposition, and good elasticity of the layer, but also we could consider that the layer has no cracks because of the good deposition process has resulted for Al₂O₃. The deposition process should have been made by heating the substrate, to expand, in order to return to original shape simultaneously to the NiAlSi and Al₂O₃ molten particles solidification. Page(s): 315-321

NOPR Collection: Special Issue on Evolution of Engineering, Technologies and Materials (Guest Editors: Dumitru Nedelcu, Jerzy Swider, María Eugenia Rabanal Jiménez & Fiqiri Hodaj)

Study of microindentation and differential scanning calorimetry of reinforced polyamide

Precision forming of micro-sized piezoceramics with a high aspect ratio

Numerical modelling and experimental validation of the pneumatic powder injection into liquid alloys

Properties of Al2O3 and NiAlSi coatings obtained by atmospheric plasma spraying on 34CrNiMo6 substrate

Properties of Al₂O₃ and NiAlSi coatings obtained by atmospheric plasma spraying on 34CrNiMo₆ substrate