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Abstract

The paper discusses the possibility of using alternative fuels from bio-mass and plastics in Poland. Their physiochemical properties and possible application in the chemical, cement and energy industries were determined. The heat of combustion of the tested samples was 26.169 MJ·kg−1. On the other hand, the moisture content in the tested material was 1.6%, i.e. within the requirements for this raw material. Since the chlorine content in relation to the sulfur content in the waste is an indicator of the corrosive potential of the fuel, the content of chlorine and sulfur was determined in laboratory tests. The analyzed waste samples were within the specified requirements. The tested material, in which the chlorine content was determined (0.577%), indicates that the tested fuels can be included in the power industry, in accordance with PN-EN 15359:2012.

Abstract

A revalorised Burzyński’s hypothesis was suggested for determination of effort of construction elements in thermally variable load conditions. Using the suggested hypothesis, surfaces of the beginning of plasticity for the heat resistant St12T steel were determined. Two numerical simulations of thermo-mechanical loads of the turbine vane made of St12T steel were performed. The result of analyses was determination of the effort states of a vane acc. to Huber-Mises- Hencky’s hypotheis and according to the suggested revalorised Burzyński’s hypothesis.

Abstract

This work is about the effect of fine aggregate properties on the physicomechanical characteristics of hardened mortars. The results indicated that the increase in grain-size of fine aggregate increases the bulk density of hardened mortars. The strength of mortars including limestone fine aggregate is higher than that of the silica-sand. Regardless of the aggregate origin, the strength of the mortars with well-graded fine aggregate for all grain-size is greater than of with uniform fine aggregate. This indicates that grading of fine aggregate increases the strength, while uniformity decreases it.

The strength of mortars with well-graded fine aggregate increases as the grain-size increases. Regardless of the aggregate origin, the strength of mortars with uniform fine aggregate increases with increasing grain-size until the grain-size range of 425-1000 µm, but after this range it decreases with increasing grain-size. The thermal conductivity increases with the increase in the grain-size. Notedly, the relationship between thermal conductivity and maximum grain-size of well-graded fine aggregate has a very strong positive correlation. Further, the thermal conductivity value for mortars formed with uniform fine limestone aggregate is minimum at the grain-size range of 425-1000 µm, while it has greatest values close together from this grain-size range

Abstract

In the paper, the method of calculating the welding energy needed to regenerate parts of agricultural machines by welding (joining) or surfacing (rebuilding, hardfacing) is presented. Problems with the lack of adequacy of the commonly used formula for linear welding energy to the actual amount of heat introduced into the welded joint are discussed. A volumetric approach based on the effective amount of heat generated by the electric arc introduced per unit volume of the weld was proposed. The simplified formulas for volumetric energy are presented. The considerations are illustrated with examples of calculations. The analyzed examples include the use of a computerized stand for geometric measurements of metallographic specimens. The proposed volumetric method of calculating the amount of heat introduced into the welded joint is a more realistic indicator of heat demand than linear energy. On the other hand, based on the volume of the weld (padding weld), it allows to determine the amount of energy needed to regenerate machine parts, including agricultural ones.

Abstract

The multitude of concepts and methods of management and control related to the word “visual” in the area of production and quality management may cause difficulties with their perception, proper understanding and use of these terms by researchers from various backgrounds (not necessarily related to production) and countries, including Poland. In particular, the noticed inaccuracies in the use of terms with the word “visual” concern such terms as visual: management, control, inspection, and testing, where, for example, in the Polish language the first three different terms in English are named with the same phrase, which sometimes causes some confusion. The aim of the article was an attempt to distinguish, sometimes “troublesome” definitions, to indicate the area of their application, to define possible relations between them, which is a peculiar novelty. The article is an analysis of the literature related to these concepts, systematizes the types of visual concepts and methods in the area of production and quality. It defines in what context the indicated terms should be used by researchers and what is the relationship between them, and under what conditions they can be used separately or jointly. The article is an attempt to indicating and analysis of the interrelation between concepts in which the word “visual” appears concerning production practice. Concepts visual: management, control, inspection, and testing, as the author proves in the article, they should be translated into English with due diligence, due to the differences between them. It has been shown that there is a strong relationship between type definition pairs as visual management & visual control and visual inspection & visual testing, where it is not a mistake to use them interchangeably, and cases, where all these concepts can intertwine, are also given.

Abstract

The parameters of high-grade steel are influenced by a combination of factors, including chemical composition and production technology. The impurity content is also a key determinant of the quality of high-grade steel. Inclusions may also play an important role, subject to their type and shape. Inclusions may increase the strength of steel by inhibiting the development of micro-cracks. The analyzed material was one grade of medium-carbon structural steel. The study was performed on 6 heats produced in an industrial plant in 140 ton electric furnaces. The experimental variants were compared in view of the five heat treatment options. The results were presented to account for the correlations between the fatigue strength coefficient during rotary bending, the diameter of and spacing between impurities. The relationship between the fatigue strength and hardness of high-grade steel vs. the quotient of the diameter of impurities and the spacing between impurities was determined. The proposed equations contribute to the existing knowledge base of practices impact of impurities with various diameters and spacing between non-metallic inclusion on fatigue strength.

Abstract

In the recent years, additive manufacturing became an interesting topic in many fields due to the ease of manufacturing complex objects. However, it is impossible to determine the mechanical properties of any additive manufacturing parts without testing them. In this work, the mechanical properties with focus on ultimate tensile strength and modulus of elasticity of 3D printed acrylonitrile butadi-ene styrene (ABS) specimens were investigated. The tensile tests were carried using Zwick Z005 loading machine with a capacity of 5KN according to the American Society for Testing and Materials (ASTM) D638 standard test methods for tensile properties of plastics. The aim of this study is to investigate the influence of printing direction on the mechanical properties of the printed specimens. Thus, for each printing direction ( and ), five specimens were printed. Tensile testing of the 3D printed ABS specimens showed that the printing direction made the strongest specimen at an ultimate tensile strength of 22 MPa while at printing direction it showed 12 MPa. No influence on the modulus of elasticity was noticed. The experimental results are presented in the manuscript.

Abstract

The article presents the results of tensile strength tests taking into account the influence of the printing nozzle diameter. The 3D printing method in FDM technology is described. The aim of the research was to investigate the effect of the printing nozzle diameter installed in the head. Samples printed with two types of filling were tested. The obtained results were summarized and compared. The printing time of the samples was compared with a diameter of each nozzle. Based on the strength tests, it can be concluded that the tensile strength of the samples made with the FDM printing technology is proportional to the used printing nozzle diameter.

Abstract

The article presents the methodology of testing sliding bearings with a flexible shell, focusing on the issue of temperature increase during experiments for a specific time interval of the START-STOP test cycle. Selected material pairs, used in previous studies, were used in the experiment. The stand used for tests in the start-stop cycle was developed under the project POIG.01.03.01-00-027 / 08-00 at the Faculty of Technical Sciences UWM in Olsztyn.