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  • Author: Sebastian Bąk x
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Abstract

The problem of numerical simulation of the material interface response under monotonic and cyclic loading is of fundamental scientific and engineering importance. In fact, such interfaces occur in most engineering and geotechnical structures. The present work is devoted to the deformational response analysis of contact interfaces under monotonic and cyclic loads. The class of materials includes rock and structural joints, soil structure interfaces, masonry and cementitious joints, localized shear bands and so on.

The aim of the proposed model is to simulate the cyclic shear test under constant normal load. The associated dilatancy effect is associated with the configurational effects of asperity interaction or dilatancy of wear debris layer. The large primary asperities are assumed as responsible for interfacial dilation and small size asperities as governing frictional sliding and hysteresis response. The elliptic loading yield function is assumed to translate and rotate during progressive or reverse loading events. The model formulation is discussed and confronted with experimental data.

Abstract

There has been a broad discussion about the viability of the European Monetary Union (EMU) in its present and prospective confines. Generally, the EMU, consisting of 19 countries, is not considered an optimal currency area due to low labor market flexibility, autonomous fiscal policies, and structural differences among its members. Considerations about the endogeneity effect of currency unions lead to the question whether the EMU will become more viable over time. According to the endogenity hypothesis formulated by Frankel and Rose [1996, 2000], a common currency area may gradually become an optimal currency area at some future point (ex post unification), despite not having been an optimal currency area (OCA) prior to (ex ante) currency unification. Currency unification should bring about increased intra-industry trade and greater business cycle synchronization among member states. The most recent literature and analyses presented in this paper suggest that the endogenity effect in the EMU has been frail since its onset. While real convergence between EMU member states has not advanced, divergence in i.a. economic structures, national income and productivity levels is observed. The most important economic mechanisms reinforcing convergence and divergence among monetary union members are presented in this paper. Using recent data and related research results, we show a significant divergence in economic structures, business cycle synchronization and productivity levels among Eurozone members in the last decade. The Krugman sectorial dissimilarity index is applied to measure changes in industrial similarity among member countries and the Hodrick-Prescott filter to estimate business cycle synchronization in the EMU. These divergence tendencies have been strengthened by the global financial crisis of 2008 and persist, calling for reforms and new policies within the EMU.

Abstract

The results of studies of the crushing process in a double toggle jaw crusher are presented. This process was carried out on six sets of crushing plates. The first three of them are used in industrial crushers – plates with a flat working surface and a triangular profile (in this work, under consideration were profiles with teeth angle γ = 90°). The fourth and fifth type refer to plates with a variable pitch t and teeth height with a triangular shape of the teeth. In the sixth solution, plates with variable pitch and width of the wedged teeth are proposed.

The results of the basic process parameters are shown, that is, average degree of fineness n, technical performance Wt, crushing energy L and crushing force F, sieve analysis of crushing product. The obtained results are the basis for the assessment of the suitability of various types of plates, especially plates with a new profile, which have an altered shape in comparison with the plates used in crushers so far.

The crushing tests were carried out with the same dimension of outlet slot er = 24 mm, close to the pitch size for plates with triangular profile. Tests were performed on the “Mucharz” sandstone. Samples from a series of blocks of different size and geometric shape were prepared. This work also presents feed mass influence on crushing process efficiency.

The plates with variable pitch and width of teeth are beneficial because of lower crushing force and energy.

Abstract

This paper presents experimental comparison of two machine crushing technologies: one-stage and two-stage. The study was carried on a model double-toggle jaw crusher which allows crushing forces, energy and toggle displacement to be measured. The main aim of the work was to determine the energy consumption of crushing process assuming a given level of fragmentation. Studies were performed on three rocks: granite “Strzegom”, limestone “Morawica” and sandstone “Mucharz”. The material tested had a cubic shape and average dimension of 90 mm. One-stage crushing was carried out for outlet slot er = 11 mm, and two-stage crushing for er = 24 mm and 11 mm. In the tests special design of variable profile moving jaw was used and fixed jaw was flat. The analysis of the results shows that taking into account energy consumption, it is better to use two-stage crushing process. For given materials energy consumption in the two-stage crushing process was reduced by 30%.