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The amplitude of a bolt load in dynamically loaded bolted flange joints depends on several factors: the resilience of the bolt and the clamping parts, the magnitude of the working load, the point of action of the working load, the way the working load is transferred from the structure to the bolt, the preload, and the geometrical imperfections of the contact surfaces of the joint. These factors are analysed in many papers, and they are covered in the VDI 2230 guideline and in standards. Fatigue curves (S-N curves) of bolts are determined by tests in which an ideal axial load is usually applied to the bolts. The effects of the bolt strength class, the thread manufacturing process, the surface protection, and the cross-section size on the fatigue strength of bolts are precisely defined. The main problem in the evaluation of bolted joints is the calculation of the actual stress, which is compared with the fatigue curves. Despite extensive research, fatigue-related bolt failures still occur in practise. This article provides a systematic overview of the influences that affect the fatigue of bolts. The conclusions are based on the research results of many authors and on our own analytical, numerical, and experimental investigations. The effects are illustrated using two practical examples of flange bolting. The assessment of fatigue according to Eurocode 3 and the VDI 2230 guideline is discussed in more detail. [ABSTRACT FROM AUTHOR]

In practical use, most gears have an involute shape of tooth flanks. However, external involute gears have some drawbacks, such as unfavourable kinematic conditions at the beginning and end of meshing, a limited minimum number of teeth, and the highly loaded convexconvex (i.e., non-conformal) contact. Researchers have developed and analysed various non-involute forms of tooth flanks, but they have not been widely accepted. The main reasons are higher manufacturing costs and sensitivity to manufacturing and assembly errors. Analyses of non-involute forms of teeth are mostly theoretical (analytical and numerical), while there is a lack of experimental confirmations of theoretical assumptions. This paper reviews external non-involute shapes, their operating characteristics and possibilities of use compared to involute gears. Established criteria, such as Hertzian pressure, oil film thickness, bending stress at the root of the tooth, contact temperature, and gear noise, were used for assessment. The results of analytical studies and experimental research on S-gears are presented in more detail. S-gears have a higher surface durability and a lower heat load when compared to involute gears. The usability of non-involute gears is increasing with the development of new technologies and materials. However, the advantages of non-involute shapes are not so significant that they could easily displace involute gears, which are cheaper to manufacture. [ABSTRACT FROM AUTHOR]

A test rig was developed for testing air springs. It uses the energy returned by the spring during unloading. The springs are loaded by means of a lever oscillating around its rotation point at a small angle. During operation, it was determined that rotation point bearings are critical elements of the test rig. This paper shows and analyses the damage that occurs on bearing ring raceways. Contact pressure and stress under individual rolling elements were calculated by using the finite element method (FEM). Mechanisms of the formation and propagation of damage were identified. Optical and electronic microscopy was used for confirming the mechanisms of damage formation. The microstructure of damaged material was analysed. It was found that depressions on bearing ring raceways form due to material fatigue and fretting. The required bearing replacement frequency was determined with respect to load. [ABSTRACT FROM AUTHOR]