Abstract
The problem of void growth and interaction is of importance to understanding the mechanics of failure in metals exhibiting ductility. In this work, the growth and interaction of voids in 6061-T6 aluminum were studied experimentally. Specifically, holes of varying numbers and relative placement were investigated for their normalized area growth with applied displacement. Flat dog-bone specimens were carefully drilled in their gauge area with no (zero) holes, one hole, and two holes (arranged vertically or horizontally) for experimentation after polishing. The growth of holes, captured by video recordings, exhibited exponential behavior and was influenced greatly by the number and arrangement of holes with the horizontal voids growing the fastest and the vertical ones growing the slowest. Also, the ensuring deformation of the sample was studied using load-displacement curves, pictography and videography, SEM imaging and Atomic Force Microscopy (AFM). The methods revealed that although the major part failure is due to large crack formation, it was preceded by intense dislocation slip activity and the formation of micro cavities. Also, the AFM quantified the three-dimensional nature of crystal or grain deformation and how it is greatly influenced by distance and location from the hole. Lastly, theoretical understanding of hole growth was offered.
Highlights
The problem of void growth and interaction, or deformation mechanics in general/elasto-plastic nature of voids, has captured the interest of many researchers over time
The problem of void growth and interaction is of importance to understanding the mechanics of failure in metals exhibiting ductility
The current paper focuses on void growth and interaction, plus overall mechanical behavior, of a holed structural metal, namely 6061-T6 aluminum alloy
Summary
The problem of void growth and interaction, or deformation mechanics in general/elasto-plastic nature of voids, has captured the interest of many researchers over time. The failure is the result of the growth coalescing into larger voids that eventually accelerates the breakage of components or when a void bursts onto a component’s surface Most of these works focused on theory and or modeling (see, for example, [1]-[33]). The experimental study by [43], on a eutectic tin-lead alloy, revealed an increase in ductility with the number of holes up to 10 holes and a decrease thereafter This last reference showed that for strain-rate sensitive materials, such as superplastic materials, it is possible to control the ductility of the holed specimen by appropriately choosing the applied strain rate. In the combined modeling-experimental study by [19], on eutectic Sn-Pb alloy under uniaxial tensile loading, it was found that strain localization in the form of shear bands is significant in all holed specimens. Such experiments can serve as a basis to validate numerical models for void growth and interaction with embedded theoretical constitutive equations in them
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