The usefulness of elastic compliance measurements to estimate crack closure in structural steel and the validity of the assumption of a constant compliance value for the fully open crack is examined. Based on considering different issues related to the experimental technique and compliance data processing, local compliance measurements and the compliance offset method recommended by the ASTM standard are selected to be most suitable for structural steel. The compliance data generated in fatigue tests on I 8G2A steel conducted under a variety of loading conditions enabled to choose an optimal strain gauge positioning and appropriate offset criterion values for the original compliance offset method and its modified (normalized) version. The adequacy of the closure measurements is assessed through checking the ability of the resulting effective stress intensity factors to account for the observed effects of the loading conditions on fatigue crack growth rates.

Effects of specimen thickness and stress ratio on fatigue crack growth and crack closure levels under constant amplitude loading and after a single overload have been studied experimentally for a structural steel ( I 8G2A). The corresponding crack growth data from the fatigue tests have been presented and evaluated. The experimental trends have been compared to those reported in the literature for various steels. The ability of the effective stress intensity factor range based on crack closure measurements to correlate the observed crack growth response has been investigated.

The strength of conveyor belts splices made in mines rarely reaches full belt strength. It consists of a number of factors. The primary is the method of their construction and proper selection of ingredients. The significant impact has also has splice quality covering both keeping proper geometry matched to the belt construction and belts working conditions and adherence to the best practices in the field of technologies of their construction.Difficult conditions in underground mines and pressure on reducing conveyor downtime (avoiding production losses) is reflected by a drop in static and dynamic splices strength. This is confirmed by numerous studies of belt splices strength and fatigue life conducted in the Laboratory of Belt Conveying (LTT) within the framework of research and expert opinions commissioned by belt manufacturers and their users. The consequence of too insufficiently low belt splices strength is their low durability, decreasing reliability and, consequently, higher mining transportation costs. Belt splices are in fact the weakest link in the serial structure which form closed loops of interconnected belt sections working in series of conveyors transporting excavated material in the mine. The article presents the results of simulation analyzes analyses investigating how the increase of belt splices durability may contribute to the reduction of transportation costs in the underground mines.

The paper presents the possibility of using FSW technology for joining elements of a landing gear beam of the M28 aircraft. The FSW process was performed on a 4-axis numerical machine under industrial conditions. However, before welding was carried out under industrial conditions, preliminary experimental tests were carried out under laboratory conditions. Preliminary research was carried out for AA2024-T3 aluminum sheets of 1 mm and 3 mm in thickness, joined in a lap configuration. The influence of technological and geometric parameters of the process on the quality and strength of the weld was examined. Sheet metal arrangement was analyzed. Tests were carried out for two configurations. The first of which with 1 mm sheet on the top and 3 mm sheet on the bottom and in reverse order. It has been shown that setting a thicker plate on the top gives a 40% better strength. The microhardness and microstructure of the weld were tested. During the laboratory tests, low-cycle fatigue tests of the FSW lap joint were performed. It has been shown that the FSW method can be an alternative to the riveting process in the production of aviation structure elements.

The subject of this paper is a new procedure applied for more precise determination of material fatigue characteristics. The proposed approach is based on a special definition of the strain energy density parameter used for material fatigue property descriptions and, in the consequence, on the new algorithm of the fatigue machine control in the feedback loop. On the basis of fatigue tests under uniaxial tension-compression with the strain energy density parameter control it was proved that the fatigue characteristics in energy approach (Wa - N1) determined directly from the tests and indirectly from the Manson-Coffin relation (E,, - Nj) with the strain control for material showing cyclic stability are similar. However, for material cyclic hardening these characteristics differ significantly in high cycle fatigue regime.

The paper presents the results of research work on linear FSW (Friction Stir Welding) joining aluminum alloys AA2024-T3 of 0.5 mm in thickness. The study was conducted on properly adapted numerical controlled 3 axis milling machine using a ceramic tool and special designed fastening device. The tool dimensions have been estimated according to the algorithm shown in the literature [4]. All joints were made of end-to end (butt) configuration under different welding speed. The rotational speed of the tool and tool offset was constant. The effect of selected technological parameters on the quality of the joint was analyzed. Produced butt joint have been subjected to a static tensile testing to identify mechanical features of the materials of joints compared to parent materials. Measurements of micro hardness HV in the plastically formed stir zone of joint and in the parent material have been carried out. Axial and radial welding forces in the joining region were recorded during the tests and their dependency from the welding parameters was studied. Based on the results of strength tests the efficiency of joints for sheets of 0.5 mm in thicknesses oscillated up to 96% compared to the parent material. It has been found that for given parameters the correct, free of defects joints were obtained. The paper also presents the results of low-cycle fatigue tests of obtained FSW joints. The use of a ceramic tool in the FSW process allows to obtain welds with higher strength than conventional tools. The results suggests that FSW can be potentially applied to joining aluminum alloys.