Browsing by Author "Hainsworth, SV"

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    Application of the work of indentation approach for the characterization of aluminium 2024-T351 and Al cladding by nanoindentation
    (Springer, 2009-02) Khan, MK; Hainsworth, SV; Fitzpatrick, ME; Edwards, L
    Nanoindentation has been used to characterize the mechanical properties of aerospace-grade Al2024-T351 with and without a clad layer of pure aluminium. The clad layer is introduced by means of a roll-bonding process which can cause significant work-hardening of the material in the clad layer. The hardness and Young’s modulus of the pure aluminium and the Al2024 have been determined by a number of methods, including the traditional Oliver and Pharr method, and a number of other methods, including direct measurement of the indentation by atomic force microscopy, and evaluation of the work of indentation. The Oliver and Pharr method was found to underestimate the area of contact as it did not include the area of piled-up material around the indentation periphery. This gave a corresponding overestimation of both hardness and modulus. The area of the indentation measured by atomic force microscopy was similarly found to underestimate the contact area owing to relaxation of material around the indent between indentation and imaging. The work of indentation approach was found to give good agreement between the hardness calculated by nanoindentation and those found in the literature. © 2009, Springer.
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    Combined experimental and finite element approach for determining mechanical properties of aluminium alloys by nanoindentation.
    (Elsevier, 2010-10) Khan, MK; Hainsworth, SV; Fitzpatrick, ME; Edwards, L
    Aluminium alloys for the aerospace industry are often clad by roll-bonded aluminium to improve corrosion resistance. The clad layer is of the order of 100 μm in thickness and it is difficult to determine the mechanical properties of this layer by conventional mechanical testing techniques. Nanoindentation is ideally suited to determining the elastic and plastic properties of such layers and here we report on a combined approach using experimental nanoindentation and finite element analysis to extract yield stress and strain hardening exponent for an Al-clad system. The approach used was calibrated against results for an Al 2024-T351 alloy, where conventional mechanical testing data was available. For the Al 2024-T351, a forward analysis was used for extraction of load–displacement curves at different indentation depths with the help of elastic–plastic properties obtained from tensile testing. For a 100 μm clad layer of pure aluminium on Al 2024-T351, reverse analysis was used for extraction of elastic–plastic properties from a single indentation test. A yield stress of 110–120 MPa and a value of 0.075–0.1 for the work hardening exponent was obtained for the Al cladding. Nanoindentation properties including maximum load of indentation, contact depth, area of contact and pile-up obtained from the forward and reverse analyses showed excellent agreement with the experimental results. © 2010, Elsevier Ltd.
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    Determination of the residual stress field around scratches using synchrotron x-rays and nanoindentation.
    (Trans Tech Publications, 2009-11-10) Khan, MK; Fitzpatrick, ME; Edwards, L; Hainsworth, SV
    The residual strain field around the scratches of 125µm depth and 5µm root radius have been measured from the Synchrotron X-ray diffraction. Scratches were produced using different tools in fine-grained aluminium alloy AA 5091. Residual stresses up to +1700 micro-strains were measured at the scratch tip for one tool but remained up to only +1000 micro-strains for the other tool scratch. The load-displacement curves obtained from nanoindentation were used to determine the residual stresses around the scratches. It was found that the load-displacement curves are sensitive to any local residual stress field present and behave according to the type of residual stresses. This combination of nanoindentation and synchrotron X-rays has been proved highly effective for the study of small-scale residual stresses around the features such as scratches. © 2020 by Trans Tech Publications Ltd.
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    Effect of tool profile and fatigue loading on the local hardness around scratches in clad and unclad aluminium alloy 2024.
    (Elsevier, 2009-12-15) Khan, MK; Fitzpatrick, ME; Hainsworth, SV; Edwards, L
    Nanoindentation has been used to study the hardness changes produced by scratching of aluminium alloy AA2024, with and without a clad layer of pure aluminium. The hardness was mapped around scratches made with diamond tools of different profiles. One tool produced significant plastic damage with associated hardening at the scratch root, whilst the other produced a ‘cleaner’ cut with no hardening. The different behaviours are attributed to whether the tool makes the scratch by a ‘cutting’ or a ‘ploughing’ mechanism. The degree of plastic damage around the scratches has been correlated with peak broadening data obtained using synchrotron X-ray diffraction. There was no change observed in the local hardness around the scratch with fatigue loading. © 2009, Elsevier Ltd.