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In the face of the reality that unexpectedly mobilized the governments of most central European countries (including Poland), the development of renewable energy sources (RES) seems to be an important direction. Therefore, both wind parks and solar farms will be constructed at double speed for energetic independence. This urgency makes the market of producers of structures for mounting solar panels also need to adapt quickly to the new situation. New constructions adapted to quick assembly with the use of nutless screw connections seem to be one of the best solutions. These structures must not only be easy and quick to install but also durable, which makes the connections resistant to cyclical loads. The speed of assembly of the substructure can be achieved precisely with the help of nutless connections, but their durability should be carefully analyzed. This article presents parametric analyses of the numerical model of this type of connection. The selection of appropriate numerical models for simulation is of key importance in the fatigue strength analysis of bolted connections. This article investigates two different models used in numerical fatigue analyses performed in the Abaqus FEA and FE-Safe program, namely, traditional bolt with nut and innovative self-tapping nutless bolt. Extended parametric analyses of both numerical models were carried out, which ultimately allowed optimization of the fatigue capacity of the connection. [ABSTRACT FROM AUTHOR]

Whilst verifying the quality of welded joints in railway bridges in Poland, it was found that many of them contained cracks of technological, fracture and fatigue origin. This problem is associated with early welded bridge structures, in which many technological imperfections were discovered. General data for x‐ray testing on approximately 200 bridges in service are given. The tests were carried out over the period 1967–1990. The number of joints tested was 15 875 and the number of cracks discovered in the joints was 437 in the 34 bridges tested. Repeated tests on the joints containing cracks in time intervals of 5–8 years neither demonstrated further growth in the cracks nor the formation of new cracks. All the cracks discovered were formed during welding operations where there was no service loading. An analysis of the stress levels necessary for the development of crack growth was carried out via fatigue laboratory tests on three butt splice models which were similar to the joints in the bridges tested. Concurrently, the probable stress level near to the cracks was determined analytically. The calculated and measured stresses under service loadings did not exceed empirically assessed weld endurance limits for these joints and confirmed no crack growth. Hot cracks and other welding imperfections in welded joints in structures are permissible if there is neither growth in service nor resistance or rigidity loss of the structure. [ABSTRACT FROM AUTHOR]

The paper presents the results of tension-compression fatigue tests of a new steel-aluminum welding transition joint with a titanium Grade 1 interlayer. The new explosive welded transition joint prototype used as a connector in the shipbuilding industry has been developed by the Explomet company situated in Opole-Poland. The paper discusses the advantages of the use of these types of connectors in comparison to the classical approach of using the bolted joints as connectors between non-weldable materials in ships. We are emphasizing its eco-friendly effect on fuel consumption by lowering the weight of the whole structure. The thickness of the new prototype of the transition joint is lower than the standard thicknesses used by other manufacturers. The multilayer metallic composite was subjected to microstructural analysis. Factors influencing fatigue durability were analyzed and the basic analysis of fatigue cracks observed during tests was presented in form of crack propagation curves. The obtained fatigue results show that in most of the analyzed cases, the crack initiation is spotted in the heat-affected zone. According to the standard procedure of fatigue testing none of the prototype test specimens would fulfill the requirements set in the ABS standard used for the testing. This is crucial information in terms of the modification of the welding technology of the transition joint which has to be adapted. Nevertheless, the presented results show that there is a place for improvement in the used welding technology. • Tension-compression fatigue test results for new explosive bonded transition joints. • The approach to fatigue tests of transition joints is discussed. • Hardness measurements of transition joints were made and discussed. • Crack propagation curves for transition joints are shown. • MARSpline regression analysis was performed to obtain the relationship between the model parameters and the maximum stress in the joint). [ABSTRACT FROM AUTHOR]