Fatigue Resistance of Welded Titanium Joints

The paper presents the results of studies of the structural state, changes in mechanical characteristics during static and cyclic loading of welded joints from technically pure titanium during thermal cycling. Based on the change in the relative deflection of the sample, a quantitative assessment of the fatigue damage accumulation at the stage of cyclic deformation up to the moment of opening and propagation of the main crack depending on the number of cycles of thermal cycling treatment is provided.

Change of Microstructure and Analysis of Fracture of the Ti-50.8 at.% Ni Alloy in the Ultrafine-Grained State after Multiple Martensitic Transformations with a Large Number of Cycles

The microstructure and mechanical properties of the ultrafine-grained Ti–50.8 at.% Ni alloy after thermal cycling treatment with the number of cycles up to 250 was investigated. A fractographic analysis of the samples after tensile tests was carried out. The fracture pattern of the alloy in the UFG state has a viscous character with microdepths on the fracture surface. The average size of microdepths decreases as the number of thermal cycles increases up to n= 250.

Effect of Non-Thermal Atmospheric Pressure Plasma (NTP) and Zirconia Primer Treatment on Shear Bond Strength between Y-TZP and Resin Cement

The purpose of this study was to investigate the effect of non-thermal atmospheric pressure plasma (NTP) treatment on the sandblasting of mechanical method and zirconia primer of chemical method used to increase the bond strength between zirconia and resin cement. In this study, Y-TZP was divided into 4 groups according to the surface treatment methods as follows: Zirconia primer (Pr), NTP + Zirconia primer (NTP + Pr), Sandblasting + Zirconia primer (Sb + Pr), Sandblasting + NTP + Zirconia primer (Sb + NTP + Pr). Then, two types of resin cement (G-CEM LinkAce and Rely X-U200) were used to measure the shear bond strength (SBS) and they were divided into non-thermal cycling group and thermal cycling group for aging effect. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test. The result of the surface energy (SE), there was no significant difference among the groups (p > 0.05). As a result of the SBS test, the Sb + Pr group had a significantly higher SBS value than the other groups regardless of the resin cement type (p < 0.05), and the decrease rate after thermal cycling treatment was the lowest. On the other hand, the NTP + Pr group showed significantly lower SBS values than the other groups except for the case of using Rely X-U200 (p < 0.05), and the reduction rate after thermal cycling was the highest. The Sb + NTP + Pr group did not differ significantly from the Pr group (p > 0.05). Within the limitations of two successive studies, treatment with NTP after sandblasting used for mechanical bond strength showed a positive effect on initial SBS. However, when NTP was treated before the zirconia primer used for the chemical bond strength, it showed a negative effect on SBS compared to other treatment methods, which was noticeable after the thermal cycling treatment.

Effect of different types of thermal cycling treatment on mechanical properties of 44NKhTYu elinvar alloy

The results of the effect of experimental regimes of thermocyclic treatment of elinvar 44NKhTYu alloy on its mechanical properties are presented.