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EN
This paper presents the experimental results of a study investigating the effect of holes and notches made on the overlap ends on the strength of adhesive joints. Single-lap joints made of S235JR steel sheets bonded with Araldite 2024-2 epoxy adhesive were tested. For comparative reasons, static shear strength tests and high-cycle fatigue strength tests were performed. Adhesive-filled joints having three holes, each with a diameter of 3 mm, and notches, each 3 mm wide and 4 mm long, were tested and compared with reference joints, i.e. without modification. The assumption was to determine whether the structural modifications would reduce the peak peel and shear stresses that are typical of this type of joints. Results of the static strength tests showed no significant effect of the applied modifications on the strength of the joints. However, in terms of fatigue strength, the results demonstrated a significant improvement in fatigue life, the value of which increased in the low-cycle fatigue region by 328.6% for the joint with notches and by 640.8% for the joint with holes. A smaller yet still positive effect of the applied modifications was shown for high-cycle fatigue. For a variable load with the maximum value of 9 MPa, the fatigue life increased by 215.9% for the variant with notches and by 183.3% for the variant with holes. Surface topography of fatigue fractures was examined by determining roughness parameters on the overlap ends in the samples. Significant differences were shown, with the selected roughness parameters being significantly lower for the reference variant than for the variants with notches and holes. It was shown that the applied structural modifications led to increasing the fatigue strength to 8.5 MPa for the limit number of cycles equal to 2×106, when compared to the reference variant for which the fatigue strength was 8 MPa.
PL
W artykule zaprezentowano wyniki badań struktury geometrycznej powierzchni wewnętrznej aluminiowych tłoczysk pneumatycznych wybieraków stosowanych w automatycznych skrzyniach biegów AS TRONIC MID. Badania powierzchni przeprowadzono przy użyciu mikroskopii konfokalnej, dla różnej wielkości pól pomiarowych, a następnie skonfrontowano je ze sobą. Uzasadniono konieczność definiowania sposobu wykonywania pomiaru podczas podawania wyników, a także stosowania odpowiednich oznaczeń w dokumentacji konstrukcyjnej podczas podawania wymagań dotyczących przestrzennego stanu struktury geometrycznej powierzchni. Przyjęcie odmiennej metodyki badań może spowodować różnice w pomiarach sięgające nawet 100%.
EN
In this paper was presented the results of research on the geometrical structure of the internal surfaces of aluminum pistons of pneumatic selectors used in AS TRONIC MID automatic gearboxes. The studies were carried out using confocal microscopy for different sizes of measuring fields. It was justified to define the way in which the measurement was performed and apply suitable designation in the construction documentation. The results of measurement can be difference of up to 100% by adopting a different research methodology.
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