J. S. Suchy

Boundary element model of coupled heat and mass transfer in solidifying castings

The solidification and cooling processes taking place in the casting domain can be described by the system of partial differential equations and adequate boundary, geometrical, physical and initial conditions. From the mathematical point of view, the so-called moving boundary problem should be considered and the task can be effectively solved using numerical methods. In this paper, the alloys solidification is considered. In differential equations describing the solidification process, the parameter called a substitute thermal capacity is introduced; in other words, the one domain approach is applied. The heat transfer model is coupled with the macrosegregation model, because the temperatures limiting the mushy zone sub-domain are a function of the alloy components concentration (a binary alloy is taken into account). Two macrosegregation models are constructed on the basis of the lever-arm law and Scheils equation, respectively. In terms of numerical computation, the boundary element method (heat transfer model) and the control volume method (macrosegregation) are applied. The typical numerical solutions presented in the literature do not take into account the relationships between heat transfer and macrosegregation processes or the models proposed are very complex and not effective. The solution presented in this paper seems to be sufficiently exact and very simple for numerical realisation.

Computer simulation of heat transfer between the particles and metal matrix during the solidification of a cast composite

In this paper, the thermal interactions between a single particle of lead and a metal matrix (Al-Si alloy) are analysed. From the mathematical point of view, this task belongs in the field of moving boundary problems. The problem has been solved using the finite element method for spherical domains. The course of particle melting (pure metal) has been modelled on the basis of the procedure called the temperature recovery method, and the solidification of metal matrix (alloy) on the basis of the fixed domain approach. The results of numerical computations are presented in the final section of the paper.

Determining Thermal Properties of Insulating Sleeves

The presented work is aimed at determining thermal diffusivity, thermal conductivity and heat capacity of insulating sleeves used in Polish metallurgical/foundry practice. On basis of the theory elaborated in [1] the mean values of thermophysical properties for temperatures range of about 150-1000 oC were obtained. The results obtained during the examinations presented in the paper can be helpful when formulating boundary conditions during the computer aided simulation of the processes of heat and mass transfer in the system: casting (ingot) – mould riser (ingot head) – ambient, which uses the investigated insulating sleeves [2, 3]. The method of determining thermal properties can be also used for other foundry materials, e.g. sands or cores.

Mathematical model for corundum single crystal growth by Verneuil method

Abstract A mathematical model which is an attempt to describe the complex process of monocrystallization by the Verneuil method is presented. The problem has been solved through the method of finite differences and at the same time making use of a certain modification of the mathematical description of Stefans problem called the the alternating phase truncation method [9]. The elaborated algorithm and the examples of solutions given at the end of the present study point at the usefulness of the presented method of numerical simulation for modern designing and controlling the processes of crystal production.

Analysis of Eneolithic Copper Jewellery Artifacts from Książnice Cemetery in South Poland

This paper presents a metallographic analysis of copper artifacts from an extraordinary Polish cemetery of Lublin–Volhynian culture dated 4000–3800 BC (Wilk in Analecta Archaeologica Ressoviensia, 2014, pp. 209–243). The Książnice necropolis, Busko-Zdrój county located in South Poland, is characterized by an unprecedented collection of prestigious objects made of copper, rare in the Eneolithic period in Poland. The archaeological studies supplemented with materials analyses give knowledge of prehistoric metallurgy and the processing of copper. For the described group of artifacts, non-destructive microscopic studies were performed including chemical analysis by means of X-ray fluorescence and energy-dispersive X-ray spectroscopy using a scanning electron microscope. The mentioned studies allowed for raw material characteristics of this important discovery.

Metallographic Studies of Selected Eneolithic and Bronze Age Artifacts from Poland

This work presents the results of metallographic studies performed on four Eneolithic and Bronze Age artifacts from Poland. All of them are of none archaeological context therefore its academic value is strongly reduced. The aim of this work is to deal with such a reduced data in a way of improving and verifing current state of knowledge about the artifacts. In order to achieve this goal elemental composition (XRF), microstructure analysis (SEM-EDS), macrostructure analysis (optical microscopy) and 3D scanning were performed.

Sensitivity analysis of macrosegregation simulation with respect to partition and diffusion coefficients

Abstract Sensitivity analysis is applied to estimate the influence of changes to the diffusion coefficient and the partition coefficient on the course of macrosegregation. These parameters are fundamental to the macrosegregation process. The analysis of mutual interactions between the values of these internal parameters and the course of macrosegregation in the casting domain leads to interesting outcomes both from the theoretical and practical points of view. At the stage of numerical simulations, the boundary element method has been used. In the final part of the paper, examples of computations are shown.