The article presents the current topic of the possibility of mechanical extraction of hard and abrasive rocks using mechanized wall systems. The problem of extracting ores from thin strata precludes the possibility of further use of current technologies involving a human at the face. Currently, the operation is carried out using explosives in column-pillar systems. In systems with a chamber column, all major processes are mechanized and carried out by self-propelled drilling and bolting machines, loaders as well as hauling and auxiliary trucks. These machines are operated in the workplace by operators. For many years, effective mechanical excavation methods were sought that would allow the development of a mining machine and a mechanised longwall complex. Such a complex is to allow excavation without the presence of humans at the face. The article presents the current technical capabilities, assumptions and requirements for such a solution. Then, an innovative longwall complex equipped with a disc shearer is introduced. The technology of work and achievable productivity are briefly presented. A worn shearer, a face conveyor and a powered support are the subject of AGH inventions.
This article represents a multidisciplinary approach to biomechanics (engineering + medicine) in the field of distal tibia fractures. The objective of the present study was to carry out a strength and reliability assessment of a medial plate for the treatment of distal tibia fractures. This was performed via numerical modelling (FEM) and experimental methods (compression test and Electronic Speckle Pattern Interferometry – ESPI method). The plate is used for internal fixation in orthopaedics and traumatology. Analyses were performed for non-fused bone with comminuted fracture in the distal metaphysis (i.e. unsuccessful treatment, where all loads in the metaphysis are carried by the plate). An anatomical tibia model (based on CT images in Mimics software) was used for FE analysis. In the experiments, the bone was replaced with a shaped piece of spruce wood (based on Mimics software) and the plate was loaded until its failure (major plastic deformation). Numerical and experimental results were evaluated and compared.
Difficult operating conditions at mining put high demands on technical responsibility of mechanical machines and influence the operator of mechanical machines in a negative way as well. The external influence of the operator has a negative impact on health and also on the general working output. The basic negative factors influencing the operator include vibrations, noise, temperature etc. Vibrations cause additional cyclic stress on construction parts of mechanical machines and lower their working life. Therefore it is necessary to mineralized vibrations. AbstraktNáročné provozní podmínky při těžební činnosti kladou vysoké nároky na technickou spolehlivost strojních zařízení a také negativně působí na obsluhu strojních zařízení. Působení vnějších vlivů na obsluhu má negativní vliv na zdraví, ale I na celkový pracovní výkon. Mezi základní negativní faktory působící na obsluhu patří vliv vibrací, hluku, teploty atd. Vibrace způsobují dodatečné cyklické namáhání konstrukčních dílů strojních zařízení a neúměrně snižují jejich životnost, proto je třeba vibrace minimalizovat.
In this paper, a technique of axial centering of cast-iron moulds, e.g. the so-called "rail system" as suggested by KonCAD CZ s.r.o. for the application of horizontal centrifugal metal casting process, was described, evaluated, and finally not recommended for practical use. The proposed principle of the axial centering technique is based on the fact that two rings with the external shape similar to the shape of the Vignole (flat-bottomed) rail are welded on the cast-iron mould external perimeter, perpendicularly to the cast-iron longitudinal centreline. The cast-iron moulds are supported by two pairs of opposite conic rollers. The cast-iron mould is driven by a contact power transmission, i.e. by the friction method employing a pair of conical rollers and acting over the welded rings to the cast-iron mould. The circumferential force transfer is carried out by the friction between the cast-iron mould rings and the two driving rollers. Both driving and driven rollers have similar shapes, analogous to a tyred wheel profile. The two driving rollers are tightly fit on the common drive shaft, the centreline of which runs in parallel with the cast-iron mould longitudinal centreline. The necessity of creating of a sufficient thrust force of the cast-iron mould against the rollers causes wear conditions at the rounding of external shapes of rings, bearings, as well as roller contact conic surfaces.
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