The investigation results of the mechanical reclamation of spent moulding sands from the Cordis technology are presented in the paper.
The quality assessment of the obtained reclaim and the influence of the reclaim fraction in a matrix on the core sand strength is given. The
reclaim quality assessment was performed on the basis of the determination of losses on ignition, Na2O content on reclaim grains and pH
values. The reclaim constituted 100%, 75% and 50% of the core sand matrix, for which the bending strength was determined. The matrix
reclamation treatment was performed in the experimental rotor reclaimer RD-6. Spent sands were applied in as-delivered condition and
after the heating to a temperature of 140 o
C. Shaped samples for strength tests were made by shooting and hardening of sands in the warmbox
technology.
W pracy szczegółowo omówiono sposób tworzenia macierzowego modelu ewolucji składu ziarnowego materiału w dowolnym układzie mieląco-klasyfikującym. Proponowany model oparty na równaniu bilansu masowego populacji ziaren składa się z trzech macierzy blokowych: macierzy całego układu M, macierzy wejść (nadawy bądź produktu) stopni układu F i macierzy nadawy całego układu F0. Poszczególne elementy macierzy blokowej M opisują ewolucję składu ziarnowego w całym układzie. W macierzy tej zawsze występuje macierz jednostkowa I i macierz zerowa 0, a w zależności od złożoności schematu układu pojawiają się w niej także macierz przejścia P i macierz klasyfikacji C, której elementy można wyznaczyć eksperymentalnie. Występujące w modelu elementy macierzy blokowej F opisują wszystkie gęstości składu ziarnowego wchodzące do danego stopnia układu mieląco-klasyfikującego, zaś elementy macierzy blokowej F0 ujmują gęstość składu ziarnowego nadawy ze źródeł zewnętrznych podawanej do wszystkich stopni układu. W pracy przedstawiono algorytm i trzy przykłady tworzenia macierzy blokowych dla wybranych schematów układu. Zaproponowany model może być wykorzystany w prognozowaniu uziarnienia produktu opuszczającego wybrany stopień układu oraz w modelowaniu procesów przeróbczych.
This paper is devoted to measuring the continuous diagnosis capability of a system. A key metric and its calculation models are proposed enabling us to measure the continuous diagnosis capability of a system directly without establishing and searching the sequential fault tree (SFT) of the system. At first a description of a D matrix is given and its metric is defined to determine the weakness of a continuous diagnosis. Then based on the definition of a sequential fault combination, a sequential fault tree (SFT) is defined with its establishment process summarized. A key SFT metric is established to measure the continuous diagnosis capability of a system. Two basic types of dependency graphical models (DGMs) and one combination type of DGM are selected for characteristics analysis and establishment of metric calculation models. Finally, both the SFT searching method and direct calculation method are applied to two designs of one type of an auxiliary navigation equipment, which shows the high efficiency of the direct calculation method.
This paper gives the simple algorithm for calculation of the degree and coefficients of the minimal polynomial for the complex matrix A = [aij]n x n .
The main objective of the present work was to determine the effect of powder composition on microstructure and properties of iron-base materials used as matrices in diamond impregnated tools. The Fe-Cu-Ni powders premixed and ball-milled for 30 hours, were used for the experiments. The influence of manufacturing process parameters on microstructure and mechanical properties of produced sinters was investigated. Sintering was done by hot-pressing technique in graphite mould. The powders were consolidated to a virtually pore-free condition during 3 minutes hold at 35MPa and 900°C. Investigations of the sintered materials included: density, hardness, static tensile test and X-ray diffraction (XRD) analysis. Microstructural and fractographic observations were also made with a scanning electron microscope (SEM). The obtained results indicate that the sintered parts have a high density, close to the theoretical value, good plasticity, relatively high hardness and yield strength, and are characterized by a coarse-grained microstructure.
In the paper the parametric optimization problem for a linear system with two delays and a PD-controller is presented. In the parametric optimization problem the quadratic performance index is considered. The value of the quadratic index of quality is calculated due to the Lyapunov functional and is equal to the value of that functional for the initial function of the neutral system with two delays. The Lyapunov functional is determined by means of the Lyapunov matrix.
In the paper a Lyapunov matrices approach to the parametric optimization problem of a time-delay system with two commensurate delays and a PI-controller is presented. The value of integral quadratic performance index is equal to the value of the Lyapunov functional for the initial function of the time-delay system. The Lyapunov functional is determined by means of the Lyapunov matrix. In the paper is presented the example of a scalar system with two delays and a PI controller.
This paper deals with a three-phase power system with hybrid transformer (HT) installed between two AC sources. The main aim of this paper is analyze the basic properties of HT with active load and ability to bidirectional energy flow. The HT contains two main units – a conventional transformer with electromagnetic coupling and PWM AC line chopper connected with secondary windings with electric coupling. The HT is located between the distribution system and a Local Balancing Area (LBA) with low power local energy sources. After describing the HT circuit and three-phase, twosources power system, the mathematical and circuit models of the AC source with HT are presented. These models are verified by means of the simulation and experimental test results obtained for a three-phase HT of about 3 kVA rated power.
This paper discusses the mechanical properties of a material fabricated from commercially available metal powder mixtures designed for
use as a metal matrix of diamond impregnated composites. The mixtures with the catalogue numbers CSA and CSA800 provided by a
Chinese producer are suitable for experimental laboratory testing. The specimens were fabricated in a graphite mould using hot pressing.
The material was tested for density, porosity, hardness, and tensile strength under static loading. A scanning electron microscope (SEM)
was used to analyze the microstructure and cleavage fracture of broken specimens. It was essential to determine how the chemical
composition and the fabrication process affected the microstructure and properties of the material. The properties of the sinters were
compared with those of hot pressed specimens fabricated from sub-micron size cobalt powder (Cobalt SMS). Although the as-consolidated
material is inferior to cobalt, it displays a favourable combination of hardness, yield strength and ductility, and seems to have a great
potential for moderate and general purpose applications.
Austenitization is the first step of heat treatment preceding the isothermal quenching of ductile iron in austempered ductile iron (ADI)
manufacturing. Usually, the starting material for the ADI production is ductile iron with more convenient pearlitic matrix. In this paper we
present the results of research concerning the austenitizing of ductile iron with ferritic matrix, where all carbon dissolved in austenite must
come from graphite nodules. The scope of research includedcarrying out the process of austenitization at 900o
Cusing a variable times
ranging from 5 to 240minutes,and then observations of the microstructure of the samples after different austenitizing times. These were
supplemented with micro-hardness testing. The research showed that the process of saturating austenite with carbon is limited by the rate
of dissolution of carbon from nodular graphite precipitates.
The stability of positive linear continuous-time and discrete-time systems is analyzed by the use of the decomposition of the state matrices into symmetrical and antisymmetrical parts. It is shown that: 1) The state Metzler matrix of positive continuous-time linear system is Hurwitz if and only if its symmetrical part is Hurwitz; 2) The state matrix of positive linear discrete-time system is Schur if and only if its symmetrical part is Hurwitz. These results are extended to inverse matrices of the state matrices of the positive linear systems.
The Copper-SiC composite was investigated with the help of FEM. The authors modeled and analyzed the effect of relaxation of thermal stresses due to seasoning at room temperature after the manufacturing process together with the effect of thermal stresses induced by reheating the material to a service temperature. Especially, hypothetical fracture at interface was of interest. It was shown that, for a fixed temperature, a single crack emanating at 0° or 45° azimuth would develop only along a portion of fiber perimeter, and a further growth would require stress increase in the fiber surrounding.