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The article concerns the issues of tool wear effect on the quality of a friction stir welding joint quality. The experiment used aluminum alloy 7075 T6 sheet metal, which is used primarily in the aerospace industry. 1.0mm and 0.8mm thick lap joints were tested. Tool wear was determined based on multiple readings on a multisensory machine. The tool wear evaluation was done on the basis of a static tensile strength test and metallographic sections of the joints. The pin of the tool works in more demanding conditions and is more exposed to friction. This results from tooling operations performed at full depth dive in the jointed material. When also considering the small dimensions of the pin such as the diameter and the great forces occurring in this process, it is easy to see why this element is most susceptible to tool wear. The welding process causes the tool to undergo friction wear, which is the cause of reduced tool dive depth in the jointed material. As a result, it is paramount to constantly control the tool extension to achieve the desired quality parameters of the joint. After creating 200m of joints, a decrease in the strength of joints was observed as well as the repeatability of the results connected to a change in the stirring conditions in the material. The change in joint strength and tool wear is also confirmed in the metallographic analysis, which states that the continued degradation of the tool makes it subject to a decrease in size of the characteristic sizes of the thermoplastic zone that is the main determining factor of the joint strength.

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The article presents an analysis of the macrostructure and mechanical properties of spot welds of joints made by Refill Friction Spot Stir Welding (RFSSW) method. RFSSW is a relatively new technology that is gaining wider use, not only in the automotive and aviation industries because it is a less energy intensive method than resistance spot welding. The primary focus of the article is the effect of welding time on the quality of the welded joints of sheet metal using the aforementioned method. The research was conducted on a joint between two pieces of sheet metal of various thicknesses (1.6 mm and 0.8 mm) made of a common aviation grade aluminium alloy 7075-T6 Alclad. Metallographic sections of select variants were made in order to analyze the structure of the joint. Strength tests with a static load were conducted in different loading configurations. A traditional tensile strength test was conducted on the lap joint, which revealed a complex stress state within the joint and an analogous test was conducted with the use of a stiffening holder that ensured a pure shear state in the joint. Peel tests were also performed on the lap joints with using a special holder.

This paper presents a design, a numerical analysis, a build-up and dynamic testing of an engineered and fabricated wheel with a passive vibration damping system designed for a roller coaster system. Taking into account the limited amount of space for fixing a wheel to a roller-coaster, this study shows an approach in which a special wheel design and viscoelastic inserts are used to reduce vibrations. A wheel comprises a rim and hub separated by a viscoelastic material and simultaneously connected by using spring steel fasteners with contractions ensuring elasticity. The dynamic tests of the wheel with a passive vibration damping system were completed with an assessment of the vibration reduction ratio in comparison to conventional roller coaster wheel types currently operated at the amusement park Energylandia located in Zator, Poland. Laboratory test results show reduction of vibrations by 36 % in the low frequency range, by 63 % in the medium frequency range and by 45 % in the high frequency range.