Brožek M., Nováková A., Kolářová M., 2012. Quality evaluation of briquettes made from wood waste. Res. Agr. Eng., At logging and at the subsequent wood and wood semi-products treatment the fine grained loose waste arises, e.g. wood dust, saw dust, shavings, chips, bark etc. One of possibilities of its meaningful utilization is the briquetting technology, products of which are briquettes determined for energetic utilization (combustion). In the paper the experimental results are published. The briquettes quality evaluation was their aim. For the briquetting tests bark (pine), shavings (about 90% spruce + 10% pine), sawdust (spruce), birch chips and poplar chips were used. The basic physical-mechanical properties were the evaluation criteria. Following properties were determined: gross calorific value, total moisture content, density, rupture force, length, diameter, density and mechanical durability.Keywords: briquetting; density; rupture force; mechanical durabilityThe more comfortable human life is paid by excessive energy increase in all its forms. The reserves of not renewable energy sources (coal, crude oil, natural gas) are not limitless, they gradually get exhausted and their price continually increases. Nevertheless they cover about four fifth of the energy consumption.In last decades the renewable energy sources are preferred, e.g. wind energy, water energy, solar energy and biomass energy. The effort results of more extensive utilization of the wind energy and solar energy are not conclusive in the conditions of the Czech Republic. But the utilization of the biomass energy appears as the perspective. Compared with other countries we are still lagging behind. According to various published information in the Czech Republic only a few per cent of consumed energy is produced from biomass. At the some time in some countries even tens per cent are produced. There are several causes of this fact -from the potential user's small knowledge of the biomass utilization advantages to the not quite sufficient subsidy policy in this field
Production of briquette bio-fuel is related to several aspects of densification process. The present paper deals with the relation between briquette volume density ρ (kg·m−3) and required deformation energy Ed (J). Wood, energy crop and cardboard feedstocks were compressed by a laboratory briquetting press of two diameters (40 and 65 mm); in this way six kinds of briquette samples (W40, W65, E40, E65, C40, C65) were produced. The values of compressing force F (N) and briquette volume density ρ were measured directly during feedstock densification; the deformation energy Ed was calculated subsequently. The amount of deformation energy Ed consumed within the achievement of specific briquette volume density ρ levels differed in case of all samples, the same as the maximum achieved briquette volume density ρ levels. Best results, i.e. efficiency of briquette production (the highest ρ, the lowest Ed), were achieved by cardboard samples, followed by wood and finally by energy crop samples. An overall evaluation indicated a higher production efficiency of briquette samples 40 mm in diameter and the disadvantage of the production of briquette samples with briquette volume density ρ > 1000 kg·m−3; above such level, the amount of consumed deformation energy Ed increased disproportionately sharply.
Abstract. The course teaches students, among other methods, also shearing technology. A laboratory exercise was prepared, in which cylindrical shaped cuts of two different metallic materials and of three various thicknesses were made using a cutting tool (blanking punch and blanking die) and a universal testing machine. The blanking punch was 10.0 mm in diameter, the blanking dies 10.3 mm or 10.8 mm diameter. The blanking was made of Cu 99.9 sheet metal of 5 mm thickness and Al 99.5 sheet metal with thickness of 3 mm, 5 mm and 10 mm. The course of the instant shear force in response to the displacement of the push plates was recorded during the experiment. The objective of the performed experiments was to determine the real and theoretical maximum shear force and work required to cut. The quality of the shearing area was assessed by the ratio to the size of the area burnish and fracture from the point of view of the effect of clearance between the blanking punch and the blanking die (Al 99.5, thickness 10 mm, punch Ø 10.0 mm and die Ø 10.3 mm or punch Ø 10.0 mm and die Ø 10.8 mm), from the point of view of the type of the cut material (Cu 99.9 and Al 99.5, thickness 5 mm, punch Ø 10.0 mm and die Ø 10.3 mm) and from the point of view of the thickness of the cut material (Al 99.5, thickness 3 mm, 5 mm and 10 mm, punch Ø 10.0 mm and die Ø 10.3 mm).Keywords: aluminum, copper, sheet metal, cutting, laboratory tests. IntroductionThe division of metallic and non-metallic materials is one of the important processes in the engineering and manufacturing industries. We can use several methods to perform this task in practice. Selection of the optimal method mainly depends on the type of divided material, shape and the dimensions of the starting semi-finished product and the required shape and dimension of the final product. In practice the commonly used method, for example, is cutting by saws, pinning to lathe, sheet metal cutting [1], heat cutting using an oxygen-acetylene flame[2], cutting using energy of a water jet [3][4], laser [5] or plasma [6]. Each of these methods has its own benefits, but also shortcomings, and therefore also an area of optimal use.Among the most widely used methods of processing sheet metal is by cutting (shearing). Cuts produce workpiece for direct use (e.g. washers under nuts of screw connections), but also semifinished cut-outs for further processing by other cold metal shaping methods (e.g. bending, drawing, extruding or stamping) and also hot (e.g. forging in dies) [7]. A great boom of this technology can be dated to the end of 19 th and start of the 20 th century [8][9][10][11][12][13][14].
Abstract. Knowledge of the steel forming resistance is very important at all methods of the steel forming. During teaching the subjects "Manufacturing Technology I" and "Basic of Manufacturing Technology" our students get acquainted theoretically (in lectures) and practically (in laboratory practice) with cold forming and with hot working. At practices they can get practically acquainted with chosen technologies of cold forming, namely with shearing, bending, drawing and stamping. In the field of hot working the practice "Experimental determination of forming resistance using the forging test" was prepared. From theory it is known that properties of metals and their alloys vary with their forming. The change of resistance against the irreversible deformation is extremely expressive. At high temperatures the majority of metals and alloys are of better plasticity -the forming resistance is lower than at normal temperature. Laboratory tests were carried out at very different forming temperatures (20 °C, 400 °C, 700 ºC and 1000 ºC). Forming was made using the fall hammer own design, made in workshops at our department. In this paper the results of three selected steel forming resistance evaluation are published. Steel 1 is unalloyed constructional fine-grained low carbon steel, steel 2 is chromemolybdenum steel and steel 3 is high speed steel. Using the obtained results the new laboratory practice was prepared and successfully tested for our students.Keywords: steel, hot working, forming resistance, forging, laboratory tests. IntroductionThe [7; 8]. Lectures are completed by the themes carried out in practice, namely the technological process of casting products, non-destructive testing, technological tests, metal hot working, metal cold working, spot welding, bonding of metallic and nonmetallic materials, length and angle measuring, control of gearings and threads, measuring of cutting edge temperature at turning etc. For study the students have at disposal beside the own notes from lectures the mimeographed texts. Next sources for study are at disposal in electronic form in the university web [9].Forming technology pertains to the basic processes of manufacturing technology. The mankind has used forming for a relatively long time. From history not only the arm production (e.g., knives, swords, sabers, rapiers, axes, coats-of-arms, armour sheets and other parts of armour), but also other products (e.g., bars, railings) are universally known. But at that time the producers knew neither the theory nor basis of working. They managed only with the own and their ancestors' experiences. The bases of the metal working theory were formed in the 2 nd half of the 19 th century. Since that time a lot of pieces of knowledge have been obtained and forming becomes an integral part of the manufacturing technology. By forming not only semi-products for further processing (e.g., sheets, bars, rolled sections) but factory-finished products (e.g., screws, nuts, washers, gear wheels, crankshafts, rails) are made, too. From the theore...
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