This paper aims to offer a novel viewpoint for improving performance and reliability by developing and optimizing suspension components in a Y25 bogie through material optimization based on wheel–rail interactions under variable load and track conditions.

The suspension system, a critical component ensuring adaptation to road and load conditions in all vehicle types, is especially vital in heavy freight and passenger trains. In this context, the suspension set of the Y25 bogie – commonly used in Türkiye and Europe – was modelled using CATIAV5, and stress analyses have been performed by way of ANSYS using the finite element analysis (FEA) method. E300-520-M cast steel was selected for the bogie frame, while two different spring steels, 61SiCr7 and 51CrV4, were considered for the suspension springs. The modeled system was subjected to numerical analysis under loading conditions. The resulting stresses and displacements were compared with the mechanical properties of the selected materials to validate the design.

The results demonstrate that the mechanical strength and deformation characteristics of the suspension components vary according to the applied external loads. The stress and displacement responses of the system were found to be within the allowable limits of the selected materials, confirming the structural integrity and reliability of the design. The suspension set is deemed suitable for the prescribed material and environmental conditions, suggesting potential for practical application in real-world rail systems.

This research contributes to the design and optimization of bogie suspension systems using advanced CAD/CAE tools. It thinks that the material selection and numerical validation approach presented here can guide future designs in heavy load rail applications and potentially improve both safety and performance.

– This study examines the effect of increased surface energy on adhesion strength. Surface modifications were made using chemical coating methods such as primer paint (primer) and cataphoresis (KTL, Kathodische Tauchlackierung). The wetting behaviour of adhesive on these surfaces and the resulting contact angles were analysed to evaluate bonding effectiveness.

– Primer paint was applied to glass fibre reinforced plastic (GFRP) materials and cataphoresis coating was applied to steel. Contact angles of the coated surfaces were measured and compared to those of the uncoated (natural) surfaces.

– Results showed that applying primer to GFRP and KTL to steel increased their surface energy compared to untreated surfaces. A decrease in contact angle correlated with improved wetting, suggesting enhanced adhesion potential.

– While the effects of surface coatings on adhesion have been studied, there is limited research specifically on the adhesion-enhancing potential of KTL coatings. Typically used for corrosion resistance, KTL is shown here to also improve adhesion. The novelty lies in experimentally demonstrating KTL’s dual role as both a protective and adhesion-enhancing layer.

This research aims to investigate how the adhesion performance of GFRP composite components, commonly used in railway vehicles, is affected when bonded to cataphoresis coated steel substrate surfaces.

In this context, the aim was to determine the optimal adhesion parameters for bonding GFRP samples with natural and primed surfaces to steel samples with cataphoresis coatings. Then, single-lap joint samples with different bond thicknesses of 1 mm, 2 mm and 3 mm were prepared. Finally, tensile tests were performed on the samples.

The results showed that GFRP specimens with natural surfaces, characterised by the highest surface roughness, exhibited the lowest bond strength. But, the highest bonding performance was achieved in specimens where primed GFRP was bonded to cataphoresis coated steel, especially with a bond thickness of 1 mm, and achieving a yield strength of 20 MPa. This situation explains the characteristic difference between surface roughness and chemical coating, which are two essential pre-treatments in adhesive bonding. While surface roughness provides mechanical interlocking, excessive roughness can hinder the adhesive’s wetting ability, causing it to remain suspended on the surface as described in the Cassie–Baxter theorem. In contrast, it has been observed that, despite low surface roughness, chemical coatings enhance the bonding between primer paint and adhesive molecules, and – as stated in the Wenzel theorem – improve the surface wettability.

As a preliminary preparation in the adhesive method, primer paint is applied to steel surfaces and GFRP material surfaces in classical industrial applications. In this research, the application of the catapheresis process to the steel substrate instead of primer paint and the bonding of primer-painted GFRP materials to this surface make a unique contribution to the research.