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Distribution of crack-tip stresses during fatigue loading with an overload event: role of initial crack-tip shape, plastic compressibility and material softening

Pandey Satyabrat, Khan Debashis, Alam Intaf

Journal of Theoretical and Applied Mechanics

2021

Vol. 59 nr 2

239--250

This paper deals with the influence of initial crack-tip shape, plastic compressibility and material or strain softening on near-tip stress-strain fields for mode I crack when subjected to fatigue loading with an overload event under plane strain and small scale yielding conditions. A finite strain elastic-viscoplastic constitutive equation with a hardening-softening- -hardening hardness function is taken up for simulation. For comparison, a bilinear hardening hardness function is also considered. It has been observed that the near-tip crack opening stress yy, crack growth stress xx, and hydrostatic stresses are noticeably controlled by the initial crack tip shape, plastic compressibility, material softening as well as the overload event. The distribution pattern of different stresses for a plastically compressible hardening- -softening-hardening solid appears to be very unusual and advantageous as compared to those of traditional materials. Therefore, the present numerical results may guide material scientists/engineers to understand the near-tip stress-strain fields and growth of a crack in a better way for plastically compressible solids, and thus may help to develop new materials with improved properties.

The Influence of Tool Geometry for Refill Friction Stir Spot Welding (RFSSW) on Weld Properties During Joining Thin Sheets of Aluminum Alloys

Łogin W., Śliwa R. E., Ostrowski R., Andres J.

Archives of Metallurgy and Materials

2019

Vol. 64, iss. 3

975--981

The paper presents the results of research on the modification of the face geometry of the refill friction stir spot welding tool sleeve for welding thin aluminum sheets with an Alclad and an oxide anode coating. The analysis of the impact of such modification on the process perform (tool motion parameters, temperature) and microstructure as well as mechanical strength of the lap joints were analyzed. The tests were carried out using aluminum alloy 2024-T3 sheets with thickness 1.27 mm. For comparative purposes,joints were also made using plates without an Alclad and without anodized coating with using unmodified tool and modified toolswith developed 3 variants of face geometry. The samples with the joint were subjected to metallographic and strength tests. It has been shown that the use of modified geometry has a decisive influence on the performance of the process and the effect of softening and mixing of materials in the zone of point connection.