Stress concentration on artificial pitting holes and fatigue life for aluminum alloy 6061-T6, undergoing rotating bendin
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Stress concentration on artificial pitting holes and fatigue life for aluminum alloy 6061-T6, undergoing rotating bending fatigue tests Víctor H. M. Lemus, Gonzalo M. D. Almaraz and J. Jesús V. Lopez Universidad Michoacana (UMSNH), Santiago Tapia No. 403, Morelia Michoacán, 58000, México. ABSTRACT This work deals with rotating bending fatigue tests on aluminum alloy 6061-T6, under loading condition close to the elastic limit of the material. Results have been obtained for three types of specimens: without artificial pitting, specimens with one artificial pitting hole and specimens with two neighboring artificial pitting holes. Results show that fatigue endurance is reduced in the case of one pitting hole and considerably for two neighboring pitting holes. In order to explain this behavior, numerical analysis by FE are carried out to determine the stress concentrations for the three types of specimens. It is found that the stress concentration for two neighboring pitting holes is an exponential function of the separation between the two holes, under uniaxial loading. The probability to find two or more neighboring pitting holes in real industrial materials, such as cast iron, corroded or pitting metallic alloys is high; then, the stress concentration for two or more neighboring pitting holes needs to be considered for the fatigue prediction life under fatigue loading and corrosion attack applications. INTRODUCTION The aluminum alloy 6061-T6 is a precipitation hardening alloy with high content of magnesium and silicon, presenting good mechanical properties and weldability. It is one of the most common aluminum alloys for general purpose use: aircraft fittings, brake pistons, hydraulic pistons, appliance fittings, valves and valve parts, bike frames, camera lens mounts, couplings, marines fittings and hardware, electrical fittings and connectors, decorative or misc. hardware, hinge pins, magneto parts and others. Modern industrial applications of aluminum alloys imply frequently environmental corrosion attack; this is the reason of some recent works dealing with the problem: development of the “Corrosion Pit Growth Law” and corrosion fatigue lives [1], surface corrosion protection of aluminum structures on marine environments, non destructive quantification of pittings, pitting corrosion behavior of aluminum alloy on welded joint, the effect of temper conditions and corrosion on the fatigue endurance of an aluminum alloy, improving pitting corrosion resistance of aluminum alloy by laser surface melting, or proposing a probability model for the growth of corrosion pits in aluminum alloys. This work is devoted to the study of fatigue endurance of aluminum alloy 6061-T6 under rotating bending fatigue tests, when one or two artificial pitting holes are machined at the narrow section of the hourglass shape specimen. Special attention is focused on the stress concentration factors caused by the artificial pitting holes and the relationship to experimental fatigue endurance.
EXPERIMENTAL PROCEDURE Tests are carried out at r
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