rss_2.0Acta Materialia Transylvanica FeedSciendo RSS Feed for Acta Materialia Transylvanica Materialia Transylvanica 's Cover, Heat Treatment and Investigation of Foam-Filled Tubes<abstract> <title style='display:none'>Abstract</title> <p>Composite metal foams are hybrid structures with the main advantages of high specific strength and mechanical energy absorption associated with low density. In the course of our research, we successfully manufactured functional metal foams of EN AC-44200 matrix filled with lightweight expanded clay aggregate particles (LECAPs) in EN AW-6060 alloy tubes with a diameter of 50 mm and a wall thickness of 5 mm. Manufacturing was performed by low-pressure infiltration directly into the aluminium tube. Six different types of samples were examined: metal matrix syntactic foam, in-situ metal foam, ex-situ metal foam, and their heat-treated pairs. In the compression tests, the heat treatment provided a visible improvement in the results of the ex-situ metal foams.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Examination of Glass-Fibre Reinforced Composite Dental Fillings<abstract> <title style='display:none'>Abstract</title> <p>In dentistry, the use of dental fillings is a routine procedure. The use of fillings is a cheap, simple and low-harm dental operation, however, the filling of deep cavities is a difficult task. During this research, three types of fillings were tested: composite fillings bonded directly to the cavity walls, fillings bonded to the cavity walls with a semi-direct method, and composite fillings bonded to the cavity lined with polyethylene fibres. In the course of our examinations, the gaps between the wall of the dental cavity and the dental filling were observed using scanning electron microscopy. The results of these measurements can be used to determine the quality of each type of filling procedure.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Design of an Experimental Injection Moulding Tool for Testing Microstructured Cavity Surfaces<abstract> <title style='display:none'>Abstract</title> <p>This research is based on the impact assessment of the active element of injection moulding tools. The quality of the tool surface has a significant effect on the filling and cooling efficiency. Our goal is to create a uniform structure on the cavity’s surface that results in a high degree of orientation during the injection moulding process. A special experimental tool is needed for the research. Our design was based on the results of previous experimental research and preliminary criteria. The design was based on the size and position tolerances of the A side of the tool. As the previous study has shown, there are three main points to consider when designing an experimental moulding tool. These are the applied manufacturing technology, Design for Assembly, and the expansion of the measurement possibilities by using different sensors. The small beam size of the femtosecond laser also allows the machining of microscopic-sized details, a technology used to structure the cavity surface. The success of this was analyzed by microscopic examination.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Manufacture of a Home-Made Spot Welding Machine from Household Electronic Waste<abstract> <title style='display:none'>Abstract</title> <p>Nowadays, spot-welding technologies are being used on a very wide range of applications. Spot-welded joints can be found in many pieces of equipment, such as toasters, computers, telephone batteries, or even in various pre-manufactured car elements. Given the prevalence of the technology, there may be a legitimate need for a machine that can be used at home for simple spot-welding operations. Such a device could be produced more cost-effectively than those currently available on the market, while using household electronic waste. These could be produced for hobby purposes, thus creating an opportunity to recycle certain types of household electronic waste, thereby improving sustainability in an engineering approach.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Design and Implementation of a Vacuum Forming Machine<abstract> <title style='display:none'>Abstract</title> <p>The purpose of this work is to present the design of a laboratory scale vacuum forming machine, which can be used for the processing of thermoplastic sheets. The designed machine can process an A4 format plastic sheet. An important consideration in the design process was to follow a cost-effective approach. The vacuum forming instrument is made for educational purposes in the framework of a final project for the Polymer Technology Laboratory of the Department of Mechanical Engineering of the Sapientia EMTE University in Târgu Mureș. The structure and the operation of the machine is similar to that found in the industry. However, the cost of production is significantly lower. The main components of the machine include the frame, heater, vacuum pump and the clamping device.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Producing a Dissimilar Joint of Copper to Austenitic Stainless Steel by Ultrasonic Welding<abstract> <title style='display:none'>Abstract</title> <p>There are several possibilities for establishing a cohesion joint between dissimilar metals. In the case of thin sheets, the ultrasonic welding process is suitable. This process can establish a cohesion joint rapidly, with a low heat input between the thin sheets. The authors have tried to determine the optimal ultrasonic welding parameters for copper and austenite stainless steel joining by using an experimental method of joining. Suitable results were obtained by welding tests due dissimilarities in the chemical, physical and mechanical properties of the copper and stainless steel. A standard size sheet thickness and test sample was used for the welding by different parameters. The parameters were refined based on the theoretical and practical knowledge during the experiments. The experimental welding was made by a Branson L20 type welder machine. The joint made by the different parameters was inspected by shearing-tensile tests (maximal force level).</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Development of Pneumatic Deformability Test of Polylactic Acid Films<abstract> <title style='display:none'>Abstract</title> <p>The aim of the present study is to develop a test method suitable for modelling thermoforming processes and which provides an index that accurately characterises the thermoformability of a film or sheet at a given temperature and pressure. For this purpose, the elevated temperature pneumatic deformability test was considered to be the most suitable. During the test, the film is blown until it tears, which takes only a few seconds. We recorded blowing during the test, and used the images to determine the ascent (k) of the specimens and approach the estimated surface of the deformed specimens with a sphere.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Development of a Clamping Device for Tensile Testing of Intracranial Flow Diverter Stents<abstract> <title style='display:none'>Abstract</title> <p>The main danger of a brain aneurysm (a sack-like bulge on the vessel wall) is that in the event of a rupture a severe hemorrhage can occur which may cause death. However, if doctors have tools at their disposal, such as numerical models and simulations for analyzing patient-specific blood vessels, they could use them to decide if a particular treatment is necessary and if so, when. For such models, the different mechanical characteristics of the flow control devices are the input data. Several of these mechanical properties of the devices, such as modulus of elasticity and tensile strength, are determined by tensile testing. In the course of our research, we have developed a clamping device suitable for uniaxial tensile testing of flow diverter stents.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Characteristics of the Levels of Mechanisation in Arc Welding<abstract> <title style='display:none'>Abstract</title> <p>Improvement of quality, reduction of the subjective possibilities of faults may be facilitated with the help of the technically rational and economically justifiable mechanisation of productive serial production as well as the use of the wide range of hardware and software IT possibilities. Mechanisation is usually understood as the mechanisation of technological operations that may otherwise be performed by manual operations (human movements and effort). Mechanisation is therefore the substitution, in whole or in part, of manual labour with the help of specialised equipment and the mechanical operation of the various movements. The present article examines the particular features of mechanisation in the field of outstandingly high significance in industrial applications, i.e. arc welding, assisting the forms of training applied in the specialty area.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Development of Graphite- and Graphene Reinforced Styrene-Butadiene Rubber<abstract> <title style='display:none'>Abstract</title> <p>The environmental impact of rubber waste can be reduced by extending the lifetime of rubber products. It can be achieved by developing graphene/rubber nanocomposites with good abrasion resistance. In this paper, we investigated how rubber mixing technologies influence the mechanical properties of rubber. We added various amounts (0, 1, 5 and 10 phr) of graphite and graphene to rubber mixtures using a two-roll mill, an internal mixer, a single- and a twin-screw extruder. We performed tensile, tear strength and Shore A hardness tests on the vulcanisates and analysed their fracture surfaces with a scanning electron microscope. Our results show that graphene had a better reinforcing effect than graphite. Rubber mixing via extrusion may contribute to more severe polymer degradation, though their reproducibility is better than that achieved on a two-roll mill or in an internal mixer.</p> </abstract>ARTICLE2021-10-28T00:00:00.000+00:00Production of Biopolymer Foams Based on Polylactic Acid Plasticized With Lactic Acid Oligomer<abstract> <title style='display:none'>Abstract</title> <p>In our work, we modified polylactic acid biopolymer using oligomeric lactic acid. We have successfully plasticised polylactic acid compounds with 5, 10, 20 wt% oligomeric lactic acid using a liquid dosing system connected to a compounder extruder. The produced compounds were foamed with an exothermic chemical foaming agent. The density of the foams was measured and the fracture surfaces were examined by electron microscopy to assess the homogeneity of the cell structure. Based on this, we believe that the plasticising effect of oligomeric lactic acid is undeniable, but a processing temperature of 190 °C is not optimal for the foaming process. In the future, the production of biopolymer foam structures with a higher density reduction can be achieved by reducing and optimizing the foam processing temperature.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Some Formability Aspects of High Strength Steel and of Consisting Tailor Welded Blanks<abstract> <title style='display:none'>Abstract</title> <p>In recent years, the demand for a reduction in pollutant emission has become extremely important in the vehicle industry. It can be achieved through fuel consumption reduction, which is a direct function of the vehicle’s weight. nowadays weight is widely controlled by the use of advanced- and ultra-high strength steels (AHSS and UHSS) in vehicle body construction. With the application of such steel sheets as chassis elements, crashworthiness can be maintained next to reduced sheet thicknesses, too. In this paper, the deep-drawability and springback after V-die bending is monitored for three types of AHSS grades, namely DP600, DP800 and DP1000 materials. The investigations are extended to tailor welded blanks (TWBs), made by the aforementioned steels coupled with a cold rolled steel sheet (DC04). Our results show that deep-drawability reduces with both the increase in strength and the increase in strength difference between the components in the TWBs. Furthermore, the higher strength is shown to cause higher spring-back. The TWBs have unique spring-back behavior around the weld line.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00The Effect of Chemical Composition and Production Technology on the Mechanical Properties of EN AW-8006 Alloy<abstract> <title style='display:none'>Abstract</title> <p>Aluminum alloys en AW-8006 with three different Fe:Mn ratios were studied. In the experiments, the temperature of the intermediate soft-annealing between the cold rolling processes and the final soft-annealing at the end of the production technology were varied. The processed samples were subjected to tensile testing and hardness measurements. The effect of chemical composition, based on the test results, showed that for samples without intermediate softening, only the increase of iron content has a significant effect on the yield stress, and the change of iron content refined the final grain structure compared to the reference material.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Fabrication of a Laser Welded Waterproof Coating Made of Stainless Steel Foil<abstract> <title style='display:none'>Abstract</title> <p>The purpose of this engineering design was to fabricate a waterproof coat for a carbon fibre reinforced polymer component. Austenitic stainless steel foil with 50μm thickness was used as the raw material. Deep-drawn elements that fit the geometry of the given part were welded together to form the coat. The deep drawing tools and the welding machine were self-designed and manufactured. The cutting of the blank and then the welding technology of the deep-drawn tablecloths were carried out with a TruMark 5010 marking laser made by Trumpf</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00The past, the present and the future of nanotechnologies<abstract> <title style='display:none'>Abstract</title> <p>Artists from the time of Mesopotamia or Egypt and in the Middle Ages astonished us with various coloured Stained-glass windows, prepared with the help of metal nanoparticles.</p> <p>The paper will deal with zeolites, nanoparticles and carbon nanotubes. The latter will be developed more extensively, because we have founded the Nanocyl company, selling carbon nanotubes and it has become the best European company. One carbon nanotube is 100,000 times thinner than a human hair, it is very light – twice as light as aluminium –, its mechanical resistance is much higher than that of steel and it conducts electricity better than metal conductors. The use of carbon nanotubes is very important in nanotechnology. For example, with the help of coiled carbon nanotubes, the weight of a single nanoparticle can be measured, it is equal to one femtogram (10<sup>−15</sup> gram). Carbon nanotubes are used in car spray painting to cancel the build-up of static electricity. With the help of carbon nanotubes, it is possible to decrease the velocity of flame propagation, when they are included in composite materials. Carbon nanotubes are also very good as sensors for toxic gases. Their uses will take up the most part of this paper.</p> <p>The future of nanotechnology will be illustrated by nanomachines, by the lift between the Earth and the Moon, and by graphene (one single sheet of graphite). The use of carbon nanotubes will be evoked in waste water cleaning, in the production of drinking water from seawater.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Modeling the Deformation and the Failure Process of Glass Woven Fabrics Based on the Fibre-Bundle-Cells Theory<abstract> <title style='display:none'>Abstract</title> <p>In this study, we modeled the deformation and failure behavior of different glass woven fabrics under uni-axial tension using the Fibre Bundle Cells-modeling method. The difference between the analytical, phenomenological model curve and the mean curve calculated from the measurement results was classified by the relative mean squared error (RMSE), which is closely related to the coefficient of determination. This value was less than 3.6% in all the examined cases, which indicated good modeling.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Future Structural Materials of High Speed Generators Used in Supercritical CO Based Power Plant Applications<abstract> <title style='display:none'>Abstract</title> <p>The aim of this paper is to present the applicability of one of the promising achievements in the fields of materials science and mechanical engineering, which provides a solution to one of the problems of the new generation power plants. One promising area of research aimed at increasing the efficiency of electricity generation is discussed in this article on the characteristics of super-critical carbon dioxide power plant cycles and the properties of high-speed generators that can be used in such power plants. The applicability of amorphous materials in the construction of high-speed electrical machines can solve the efficiency problem of such machines, enabling its use in new generation power plants.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Development of Advanced High Strength Automotive Steels<abstract> <title style='display:none'>Abstract</title> <p>In recent decades, the automotive industry has faced ever-increasing demands. Increasing requirements can be observed in terms of both consumer expectations and legal requirements. On the consumer side, there is a demand for cars that are as economical as possible with lower fuel consumption, but providing also greater comfort and safety. These requirements are accompanied, from a legal point of view by more rigorous environmental regulations and requirements concerning the reduction of harmful emissions. Meeting these often-contradictory requirements is a growing challenge for car manufacturers and raw material suppliers, as well. Meeting the requirements in the most versatile way has resulted in tremendous progress over the last 40–50 years, both in the automotive industry and in the production and development of raw materials. The first part of this series of papers summarizes the main requirements in the automotive industry, as the main driving forces for material developments. Furthermore, the main types and properties of traditional high-strength steels, as well as the so-called first-generation Advanced High-Strength Steels will be introduced. In the second part, the main types and manufacturing processes of second generation advanced high-strength steels will be analyzed and some of the current steel developments will be presented through the results of the three generations of Advanced High-Strength Steels.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00The formation and stability of bulk amorphous and high entropy alloys<abstract> <title style='display:none'>Abstract</title> <p>Two kinds of phase stabilization mechanism are discussed and compared: the first is characteristic of the formation of bulk amorphous alloys, in which the high supercooling ability of multicomponent liquids is responsible for the glassy phase stabilization. Here the hindered nucleation of crystalline phases is the center phenomenon. The origin of this hindering is the slowing atomic mobility in the supercooling melt. In contrast the melt supercooling is negligible during the high entropy alloy formation. It is believed that stability of the crystalline single fcc phase is the consequence of the characteristic of high configurational entropy at high temperatures. However, the significance of this entropy-dominated stabilization is overestimated in several references. It has been concluded that transition metal contraction (arising from the d electron participation in the overall bonding state) does also contribute to the high temperature stability of fcc single phase in the high entropy alloys.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00Design and Manufacture of a Microfluidic Cell To Be Used With a Spectroscopic Ellipsometer<abstract> <title style='display:none'>Abstract</title> <p>In material testing and manufacturing processes, creating thin layers is a widely used method for structure development or for surface treatment purposes. Despite its widespread use, the physical background of the layer development process is currently under-researched. Its examination requires the development of procedures and tools that, in combination with the existing tools, can help to understand these processes. The development of microfluidic cells is a way to solve this problem. In this paper, a newly developed microfluidic cell is presented, which also offers a solution to several problems encountered when using previous designs.</p> </abstract>ARTICLE2021-07-08T00:00:00.000+00:00en-us-1