The author of this article carries out an analysis of the evolution of the term ‘commemorative names’ in the aspect of municipal onomastics. She primarily researches how the scope of this term has changed and which name groups have been included with that term. Moreover, she researches how the commemorative names themselves have changed. She concludes that the names of symbolic motivation that refer to cultural competencies of their users do not form a homogenous group, but they differ in genetic and motivational terms. Thus, four such groups may be identified: 1. commemorative names bearing real meaning, 2. conventional discretionary names (honorifying), 3. commemorative-discretionary names referring to local heroes, places and events, 4. names resulting from the broadly understood ‘cultural memory’, commemorating ideas, values, literary and movie characters, titles, Slavonic mythology and Polish legends, faith in its various dimensions, literary trends, artistic styles, art, etc. All four groups have their dual functions in common: deictic and cultural.
The paper presents recent developments concerning the formation of surface layer in austempered ductile iron castings. It was found that the traditional methods used to change the properties of the surface layer, i.e. the effect of protective atmosphere during austenitising or shot peening, are not fully satisfactory to meet the demands of commercial applications. Therefore, new ways to shape the surface layer and the surface properties of austempered ductile iron castings are searched for, to mention only detonation spraying, carbonitriding, CVD methods, etc.
In this study a group of selected transformation kinetics equations is applied to describe the isothermal ferritic transformation in austempered ductile iron (ADI). A series of dilatometric tests has been carried out on ADI at different temperatures. The obtained experimental data are utilized to determine the parameter values of the considered kinetic equations. It is found that the transformation kinetics models by Starink, Austin and Rickett are substantially more effective at describing the ferritic transformation in ADI than the much celebrated Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Furthermore, it is demonstrated that evaluating the kinetic parameters using the least squares method instead of calculating them from vastly used formulas can significantly improve the accuracy of the JMAK model’s predictions.
In this study, a preliminary evaluation was made of the applicability ofthe signalsof the cutting forces, vibration and acoustic emission in
diagnosis of the hardness and microstructure of ausferritic ductile iron and tool edge wear rate during its machining. Tests were performed
on pearlitic-ferritic ductile iron and on three types of ausferritic ductile iron obtained by austempering at 400, 370 and 320⁰C for 180
minutes. Signals of the cutting forces (F), vibration (V) and acoustic emission (AE) were registered while milling each type of the cast iron
with a milling cutter at different degrees of wear. Based on individual signals from all the sensors, numerous measures were determined
such as e.g. the average or maximum signal value. It was found that different measures from all the sensors tested depended on the
microstructure and hardness of the examined material, and on the tool condition. Knowing hardness of the material and the cutting tool
edge condition, it is possible to determine the structure of the material .Simultaneous diagnosis of microstructure, hardness, and the tool
condition is probably feasible, but it would require the application of a diagnostic strategy based on the integration of numerous measures,
e.g. using neural networks.
The article presents the results of a comparative analysis of the metal substructure for dental prosthesis made from a Co-Cr-Mo-W alloy by
two techniques, i.e. precision investment casting and selective laser melting (SLM). It was found that the roughness of the raw surface of
the SLM sinter is higher than the roughness of the cast surface, which is compensated by the process of blast cleaning during metal
preparation for the application of a layer of porcelain. Castings have a dendritic structure, while SLM sinters are characterized by a
compact, fine-grain microstructure of the hardness higher by about 100 HV units. High performance and high costs of implementation the
SLM technology are the cause to use it for the purpose of many dental manufacturers under outsourcing rules. The result is a reduction in
manufacturing costs of the product associated with dental work time necessary to scan, designing and treatment of sinter compared with
the time needed to develop a substructure in wax, absorption in the refractory mass, casting, sand blasting and finishing. As a result of
market competition and low cost of materials, sinter costs decrease which brings the total costs related to the construction unit making
using the traditional method of casting, at far less commitment of time and greater predictability and consistent sinter quality.
The paper discusses possible applications of the percolation theory in analysis of the microstructure images of polycrystalline materials.
Until now, practical use of this theory in metallographic studies has been an almost unprecedented practice. Observation of structures so
intricate with the help of this tool is far from the current field of its application. Due to the complexity of the problem itself, modern
computer programmes related with the image processing and analysis have been used. To enable practical implementation of the task
previously established, an original software has been created. Based on cluster analysis, it is used for the determination of percolation
phenomena in the examined materials. For comparative testing, two two-phase materials composed of phases of the same type (ADI
matrix and duplex stainless steel) were chosen. Both materials have an austenitic - ferritic structure. The result of metallographic image
analysis using a proprietary PERKOLACJA.EXE computer programme was the determination of the content of individual phases within
the examined area and of the number of clusters formed by these phases. The outcome of the study is statistical information, which
explains and helps in better understanding of the planar images and real spatial arrangement of the examined material structure. The results
obtained are expected to assist future determination of the effect that the internal structure of two-phase materials may have on a
relationship between the spatial structure and mechanical properties.
The graphite form in cast iron is the structure parameter deciding on its all physical and mechanical properties. Three basic forms of graphite: flake, vermicular (compact) and nodular (spheroidal) are singled out in standard cast iron grades, without a heat treatment. Standards of individual grades of cast iron the most often allow only the homogeneous graphite form, sometimes with addition of 5÷10% of the other form. The interesting and - in the authors opinion - future-oriented material can constitute cast iron in which various forms of graphite are present, e.g. in comparative amounts: spherical and vermicular cast irons. Cast iron within which graphite occurs in two or three forms was named „Vari-Morph” (VM) cast iron, i.e. the one in which spherical and vermicular or vermicular and flake graphite occur in a wide range of proportions. The results of investigations of these new cast iron grades and their properties are presented in the hereby paper.
In the paper, the authors present the approach to modelling of austenitic steel hardening basing on the Frederick-Armstrong’s rule and Chaboche elastic-plastic material model with mixed hardening. Non-linear uniaxial constitutive equations are derived from more general relations with the assumption of an appropriate evolution of back stress. The aim of the paper is to propose a robust and efficient identification method of a well known material model.
A typical LCF strain-controlled test was conducted for selected amplitudes of total strain. Continuous measurements of instant stress and total strain values were performed. Life time of a specimen, signals amplitudes and load frequency were also recorded.
Based on the measurement, identification of constitutive equation parameters was performed. The goal was to obtain a model that describes, including hardening phenomenon, a material behaviour during the experiment until the material failure. As a criterion of optimisation of the model least square projection accuracy of the material response was selected.
Several optimisation methods were examined. Finally, the differential evolution method was selected as the most efficient one. The method was compared to standard optimisation methods available in the MATLAB environment. Significant decrease of computation time was achieved as all the optimisation procedures were run parallel on a computer cluster.
The paper attempts to analyze distortions of cast iron and cast steel rings, after heat treatment cycles. The factors influencing distortion are: chemical composition of material, sample geometry, manufacturing process, hardenability, temperature and heat treatment method. Standard distortion tests are performed on C-ring samples. We selected a ring-model, which approximate the actual part, so that findings apply to gear rings. Because distortion depends on so many variables, this study followed strictly defined procedures. The research was started by specifying the appropriate geometry of the samples. Then, the heat treatment was conducted and samples were measured again. The obtained results allow to determine the value of the resulting distortion and their admissibility. The research will be used to evaluate the possibility of using the material to produce parts of equipment operated under extreme load conditions.
The paper presents the effect of pre-heat treatment on the mechanical properties of ductile cast iron with elevated content of Cu and Mo elements. Austempered Ductile Iron is a material with non-standard properties, combining high tensile strength and abrasion resistance with very good plasticity. In addition, it is prone to strain hardening and have good machining abilities. The study was conducted for five designed heat treatment cycles. The variables were the time and temperature of the pre-heat treatment, followed by one of two standard heat treatments for ADI cast iron. The aim of the authors was fragmentation of the grains of perlite during the initial heat treatment. It is presumed, that subsequent heat treatment will cause further refinement of the microstructure than would be the case without initial heat treatment. Diffusion is much faster than in case of ferritic matrix of cast iron. The results will be used to evaluate material for the production of parts of equipment that must operate under extreme load conditions.