Badania wpływu zastosowania stopów lekkich na własności użytkowe ratowniczej obudowy hydraulicznej

• Autorzy: Kwieciński D. , Kalukiewicz A.

Warianty tytułu

EN

Application of light alloys in hydraulic mine rescue supports and its influence on support performance

• Języki publikacji: PL

Abstrakty

PL

Autorzy przeprowadzili analizę dotychczasowych sposobów wymiarowania konstrukcji stojaków oraz możliwości konstruowania stojaków ze stopów aluminium serii EN AW-7xxx. Do dalszych prac badawczych wykorzystano krzywą Johnsona-Ostenfelda. Wzór Johnsona-Ostenfelda na podstawie własności mechanicznych materiału stojaka oraz cech geometrycznych elementów konstrukcji pozwala wyznaczyć naprężenie krytyczne. Badania i analizy teoretyczne przeprowadzono najpierw na próbkach modelowych, a następnie potwierdzono na obiekcie rzeczywistym, wykorzystując do weryfikacji obliczenia MES. Określono naprężenia i obciążenie krytyczne w warunkach badań laboratoryjnych i obliczeń analitycznych. Porównanie uzyskanych wyników daje wynik zbieżny i zadowalającą dokładność wyników.

EN

During the accidents in underground mines the excavations might be blocked by rock debris. When miner teams are present in the area, the rescue operation is undertaken to force an access to the miners, provide an escape route and lead them out safely (or carry them if necessary). In the conditions when there is no risk to human life it might still be necessary to force the way through the rock debris. In order to safely reach the miners in the hazard zone and, particularly, to force the way through the blocked heading section it is required that specialised equipment will be used to secure the newly-executed heading. On account of its type and destination, the inside diameters of the new heading are rather small: its height ranging from 0.5-1.6 m, width: 0.8-1.2 m. The rescue men, carrying heavy apparatus, have to move within such confined space; hence it is necessary that the weight of the equipment should be as little as possible. Apparently the major problem to be tackled is the design of the prop in a hydraulic support. On account of the materials used, the prop is a slightly unusual cylinder. Prop dimensioning is based on calculations of its static strength. Several authors propose various computation procedures, though in each case they use the lateral deflection formula. Methods and techniques employed to date are reviewed in the study, starting from computational algorithms based on the Euler's formula whereby a cylinder is treated as a rod with fixed ends and joints at both ends, the rod length being equal to that of the cylinder with the piston protruding and its rigidity equal to that of the piston rod; to solutions widely used in engineering practice and provided in the Polish standard PN-B-03200 and solutions based on differential equations of the deflection line and the energy of internal forces being the sum of potential energy of bending stresses and of an elastic joint in the cylinder, right through to the calculation procedures recommended by relevant European standards. All these formulas, however, proved to be of little use while dimensioning a prop made of aluminium. Stress values obtained analytically were not consistent with the results of laboratory tests. Approximately correct results were obtained only when stresses were determined with the use of FEM software. That is why another procedure is suggested which would yield nearly identical results. Johnson-Ostenfeld curve best approximates the real-life pattern as it takes into account elastic--plastic strains. In the case of props, the limit of proportionality is always exceeded, so Euler's formula is no longer applicable as elastic-plastic strains are generated in the prop material. Exceeding the critical stress level in the range beyond the proportionality limit leads to the changes in the microstructure of the material, in the form of minute slips that tend to disappear once the loading is removed, at the same time producing plastic strains. When the proportionality limit is exceeded very little, the slips are few and far between but their number rapidly increases as the stresses approach the yield point. Tests were first run on model specimens, then on real-life members. The models of piston rod in the prop of the rescue support were developed, the piston rod slenderness being taken as the similarity criterion. The equation of Johnson-Ostenfeld curve was obtained for the assumed boundary conditions and the set of data obtained from engineering specifications and critical parameters for the given slenderness were found. Using the relationships expressing reduced stresses in accordance with Huber-Mises-Hencky's hypothesis, the stress components in the three main directions were substituted. The critical force was obtained with the use of DesignSpace software (ANSYS) and Autodesk Mechanical Desktop intended for simulation of behaviours of structures under loading. The FEM technique provided by ANSYS was employed. The results were then verified by way of experiments. Results obtained on the basis of parameters of characteristic equations and of the critical force obtained experimentally were fully consistent with theoretical predictions. The difference between the critical load values was 2.27% and between critical stress values: 6.01%. The procedure of full-size model testing was similar and the main aim was to investigate the behaviour of the two components subjected to biggest loads: a cylinder and piston rods. The Johnson-Ostenfeld curve was obtained on the basis of boundary conditions and the data from engineering specifications. This system of equations being solved, the critical loads P were obtained: for the cylinder for the piston rod tloczyska = 796.05 kN. That means the cylinder is going to be damaged first. In the course of laboratory tests, the stresses and corresponding loads were recorded, the results were the compared with the predicted values and verified in the laboratory conditions. The results appear to be fully consistent with theoretical analyses. The difference between the critical load values was 3.05% for the critical stress values: 2.9%. Mechanical properties of the prop material and geometry of its structural elements being known, the employed Johnson-Ostenfeld formula allows the critical stress to be determined and further utilised to find the critical force that can be applied. Critical stresses and loads are established and the results agree well with theoretical predictions. Model tests were further utilised in theoretical analysis of stability. Critical stresses and loads acting on the cylinder pipe and the piston rod pipe modelled previously were obtained. The results reveal that the cylinder pipe is less stable on account of the smaller critical load to be carried. Accordingly, the cylinder pipe was used in further analyses. Comparing the results of these analyses and of previous strength tests shows a good correspondence, as in model testing. At the same time, the algorithm for engineering calculations of the prop was proposed. Further research will establish the adequacy of the considered method in the design of other types of cylinders and will help to find the method to minimise the mass of the element at the same time maximally utilising the mechanical properties of the material. In all this financial considerations and manufacturing capabilities ought to be given proper consideration.

Słowa kluczowe

PL

obudowa ratownicza; stopy aluminium

EN

rescue mining support; aluminium alloys

• Wydawca: Instytut Mechaniki Górotworu PAN
• Czasopismo: Archives of Mining Sciences
• Rocznik: 2004
• Tom: Vol. 49, nr 1
• Strony: 101--119
• Opis fizyczny: Bibliogr. 21 poz., rys., wykr.

Twórcy

autor

Kwieciński D.

• Centrum Mechanizacji Górnictwa KOMAG, 44-100 Gliwice, ul. Pszczyńska 37

autor

Kalukiewicz A.

• Wydział Inżynierii Mechanicznej i Robotyki, Akademia Górniczo-Hutnicza, Kraków

Bibliografia

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