V. A. Nazarenko

Fatigue failure of rolled high-porosity materials made of copper fiber at resonance bending oscillations

ConclusionsFatigue failure of rolled high-porosity materials based on copper, tested in the conditions of resonance oscillations,is accompanied by a considerably slower drift of the resonance frequency (lower rate of fatigue damage) then failure of dense copper.The relative variation of the resonance frequency can be used to evaluate the residual endurance of the porous materials and also as a fatigue strength criterion.In bending, the dense and low-porosity materials fail under the effect of normal stresses, whereas high-porosity materials fail under the effect of shear stresses.

Mechanical and Fatigue Properties of Powder Titanium Strips, Obtained by Asymmetric Rolling

The mechanical properties of titanium powder strips obtained by asymmetric rolling technique are investigated. It is found out that the use of asymmetric rolling during the consolidating and repeated compacting rolling allows obtaining a strip with better mechanical properties than that obtained by conventional technique. The fracture surface of a titanium strip obtained by symmetric rolling has a significant ratio of the interparticle fracture. After asymmetric rolling, the fracture surface is totally dimpled. It is shown that the asymmetric rolling improves the quality of interparticle contact and, consequently, the ductility and fatigue resistance increase significantly.

Mechanical Properties and Fracture Mechanisms of Commercially Pure Multilayer Iron Produced by Strip Joint Rolling

Multilayer materials (1.2–0.25 mm thick) are produced by sintering in a container at 850°C and cold rolling of ten-layer briquettes of commercially pure iron. It is shown that the tensile strength of the materials studied is proportional to the total true strain value by rolling and reaches 1400 MPa at percentage extension 1%. Endurance limit increases up to 670 MPa. With increasing strain degree by rolling, the structural elements inside layers reduce in size, when high interlayer strength between macro layers. The best correlation of endurance limit of materials with micro yield strength is observed, when 0.01% of residual strain.