THE MODEL OF ALUMINIUM ALLOY CLAD LAYER DESTRUCTION DURING FA-TIGUE
Journal Title: Проблеми тертя та зношування - Year 2018, Vol 81, Issue
Abstract
The use of aircraft aluminum alloys cladding as a corrosion protection technology leads to fatigue resistance decrease. This effect is due to the cyclic elasto-plastic deformation of the clad layer, in which damages in the form of continuity defects are formed and intensively de-veloped. The destruction of the clad layer initiates the fatigue damage of the alloy base mate-rial, which leads to a fatigue resistance decrease. Intensive elasto-plastic deformation of the cladding layer leads to the deformation relief (DR) of the surface appearance, which occurs through the local areas of plastic deformation with increased roughness values. With an in-crease in the number of loading cycles, the DR develops in three dimensions: on the plane and in the directions normal to the material surface. Indicator of two-dimensional development is the relative area of the DR, and indicator of its development in the direction normal to the surface is the roughness parameter. An integral indicator of the DR development is the surface plastic deformation quantity. For the clad layer damage numerical assessment, it is proposed to use the criterion of destruction - the relative magnitude of the volume increase due to the formation and accumulation of integrity defects in the layer. Based on the phenomenological model of destruction proposed in the work, the expression for this criterion estimation, which includes known indicators of the DR development in the three-dimensional direction, is sub-stantiated. It is shown that to destruction assessment, it is necessary to use an additional DR indicator - DR surface area to its perimeter ratio. The numerical implementation of the pro-posed model was carried out on the basis of test data of DR development on the clad layer surface of the flat specimens under cyclic loading. It is shown that the phenomenological as-sumptions for the model specification do not contradict the test data of DR indicators devel-opment, and the criterion of destruction satisfactorily describes the damage of the clad layer. It has been substantiated that the ultimate destruction is obtained at critical values of DR area to its perimeter ratio, which gives grounds to suggest this indicator as a criterion for describing the development of DR on the surface and predicting the fatigue crack initiation in the alloy material.
Authors and Affiliations
S. IGNATOVICH, M. KARUSKEVICH, S. S. YUTSKEVYCH
Keywords
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