Abstract: The focus of this work is to investigate pre-cracked plate element fracture under mixed mode I/II loading. In order to look into element with inclined initial crack, the test procedure was also performed due to pure opening fracture (I mode) and in-plane shear mode (II mode). For this purpose, static and dynamic tests were performed with original testing device, in which the specimen was fixed in so called “Arcan disc”. The results showed fracture characteristics dependence under initial crack orientation angle, i.e. due opening mode, in-plane shear mode and mixed mode I/II fracture.
Abstract: The publication analyzes the possibility of applying laser ablation for texturing bearing steel 100CrMn6 considering a tribological aspect. The use of different variants of laser micromachining, including pulsed radiation (λ = 1.064 μm) and the geometric texture of the surface, facilitated with obtaining the characteristic stereometry of the surface with regularly arranged micro-channels of lubrication on the surface of roller bearing steel.
Abstract: The corrosion of exploited motor vehicles and important or potentially dangerous structures is not a new problem of engineering . However, nowadays, it still remains one of the most burning questions of manufacturing welding structures. There are a number of established methods and technological solutions allowing improvements to the premature corrosion resistance of exploited welded joints and structural elements. In the majority of cases, different protective coatings are used. However, protective coatings are not applicable for some structures in food and medical industry as well as for some other big dissimilar-material structures of a complicated shape. In such cases, the corrosion resistance of welded structures may be provided by other technological means. The present research is aimed at investigating the efficiency of such methods. Several different welding technological solutions and post-weld surface treatments have been applied. The corrosion resistance of the obtained welded joints has been evaluated conducting tests on corrosion under laboratory conditions. The obtained results and conclusions of the present research may be useful for manufacturers solving the problems of the corrosion resistance of welded dissimilar-steel structures.
Abstract: On covering aluminum and its alloys with coatings resistant to high-temperature corrosion and attrition, abundant technological problems arise. The key problem is a removal of the film of aluminum oxide Аl2O3 from the aluminum substrate. This permanent, chemically continuous film of oxide reduces adhesion between the substrate and the coating. For improving cohesion of the coating with the substrate, an appropriate pre-treatment of aluminum is required. In the paper, cleaning of aluminum alloy AW 5754 by electric discharge is investigated. This method is considered one of most environmentally friendly methods of surface cleaning. The impact of the parameters of aluminum alloy cathodic cleaning on the surface cleaning width, its roughness and free energy of the surface were examined. In addition, the topography, microstructure and chemical composition of the surface of cleaned aluminum alloy were estimated.
Abstract: This paper present the result obtained from new experimental STEIN-MESYFIL 953 V; STEIN-MESYFIL 954 V coatings. The surfacing material was wires of 1.6 mm diameter. The tests aimed at determining wear resistance of coatings sprayed on steel substrate. The investigation shows that the tribological behaviour of new experimental thermal arc sprayed coatings is greatly affected by its microstructural constituents such as porosity, oxide inclusions, and microhardness of coatings. Results show that increasing porosity of coatings twice, it doubles the mass loss. Results for thermal sprayed coatings of all experiments showed their high wear resistance and are discussed.
Abstract: In the Paper, an analysis of laser modification of the surface of specimens produced of powder steel 1.2083 by SLS (selective laser sintering) method is carried out. Three main structures being formed on laser modification of the sintered steels are presented: periodical, interim and degrading. The dependence of the changes of the technological parameters of the laser equipment on the geometrical parameters of the specimen under processing is provided.
Abstract: In the paper, the problems of reliability and safe exploitation of the piston compressor in a residue conversion set are discussed upon. After a long exploitation, an emergency shutdown of the above-mentioned compressor occurred. On the primary examination, a fracture of the cylinder and the hub of the compressor were found. The goal of the investigation: to identify the cause of destruction of the compressor of the naphtha residue conversion set.
Abstract: This paper presents the methodology and results of laser texturing of the surface layer steel 41Cr4, applied to the manufacture of crankshafts and selected aluminum alloy used for the production of slide bearings (bearings) for internal combustion engines. Laser treatment of the surface layer of this material was carried out using Nd: YAG laser with a wavelength of pulsed laser radiation λ-1064 nm. Application of laser ablation micromachining in sensitive zones of the crankshaft and slide bearing, mainly the surface layer of the friction pair, was aimed to formation of a suitable surface texture containing oil microchannels. Applying different parameters ablative laser micromachining (power density, repetition rate, number of pulses in the same area, the overlap area microchannels), a very interesting stereometry of the surface layer steel 41Cr4 and bearing alloy was obtained. The lubricant had characteristic microchannels, very important in the tribological process of the friction pair crankshaft – slide bearing. Laboratory metallographic tests showed the high dispersion microstructure of martensitic steel 41Cr4 in the superficial zone, melted and hardened. The transition zone was found to be of martensitic-bainitic microstructure and bainite. The microstructures are formed by ultrafast phase transformations over time crystallization of alloy Fe-Cr-C from the liquid phase (microhardness in the range of 550-680 HV0.05). The microstructures appear in the adjacent area to the lubricant microchannels produced during laser texturing. The studies of laser texturing the sliding layer of slide bearing made of aluminum alloy, destined to cooperate with tribological function pin engine crankshaft are preliminary results. The positive results: high repeatability of the process texturing regular geometric shape microchannels and ease process control. In the best version, technological preliminary tests showed the following oil microchannels dimensions: depth of about 3.2 microns, width 47 microns; it is a promising result.
Abstract: The use of documents with RFID labels, particularly passports, is often equivalent to mechanical damage, the loss of printed data and many negative consequences stemming from them. The article presents a system for testing the mechanical durability of load damage considering such types of documents. Based on the results of the analyzed requirements, a set of testing devices has been developed in order to enable a complex assessment of the mechanical durability of electronically protected documents. The use of common solutions regarding individual testers enables the execution of both normative and programmable tests and facilitates an easy extension of the system for the modification of its individual devices.
Abstract: The article studies the effect of PTL modes on structural and mechanical regularities in material deformation at the crack tip using the parameters of fracture mechanics. The obtained results are the basis for a more precise definition of the guaranteed strength of structural elements with crack-like defects.