Browsing by Author "Lewis, A."

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    Effect of electromagnetic treatment on fatigue resistance of 2011 aluminum alloy
    (World Scientific Publishing, 2016-08-08) Mohin, M. A.; Toofanny, H.; Babutskyi, A.; Lewis, A.; Xu, Yigeng
    Beneficial effects of the electromagnetic treatment on fatigue resistance were reported on several engineering alloys. These could be linked to the dislocation activity and the rearrangement of the crystal structure of the material under the electromagnetic field (EMF), resulting in delayed crack initiation. This paper presents an experimental study on the effect of pulsed electromagnetic treatment on the fatigue resistance of 2011 aluminum alloy. Circular cantilever specimens with loads at their ends were tested on rotating fatigue machine SM1090. Fatigue lives of treated and untreated specimens were analyzed and compared systematically. It has been found that the effect of the pulsed electromagnetic treatment on the fatigue resistance is dependent on the intensity of the pulsed EMF and the number of the treatment applied. Clear beneficial effect of the pulsed electromagnetic treatment on the fatigue resistance of the aluminum alloys has been observed, demonstrating a potential new technique to industries for fatigue life extension.
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    Effect of electropulsing on the fatigue resistance of aluminium alloy 2014-T6
    (Elsevier, 2019-11-12) Babutskyi, A.; Mohin, M.; Chrysanthou, A.; Xu, Yigeng; Lewis, A.
    The effects of electropulsing on the fatigue resistance of aluminium alloy 2014-T6 were studied in relation to electric current amplitude, pulse duration, and number of repetitions. Utilising the Taguchi method, the present study identified the current amplitude and the duration of the electropulsing as the two critical treatment parameters for improved fatigue resistance. A 97% fatigue life improvement was achieved under the electropulsing conditions that were applied. An increase in microhardness and a decrease in electrical conductivity due to electropulsing were correlated with enhanced fatigue resistance in the alloy. Mechanisms related to the effects of the electropulsing treatment were elucidated based on observations from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as numerical simulation results. The mechanisms identified by observation included dislocation movement and the secondary precipitation of GP-zones. Further explication of these mechanisms was provided by the application of a “magnetic field’’ model.
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    Effect of plastic deformation on compliance curve based crack closure measurement
    (Trans Tech Publications, 2016-09-30) Mohin, M.; Xu, Yigeng; Lewis, A.; Chrysanthou, A.
    Fatigue crack growth depends heavily on near tip stress-strain behavior controlled by many micromechanical and microstructural factors. Crack closure is widely used to rationalize crack growth behaviour under complex loading conditions. Reliable crack closure measurement is essential for enhanced damage tolerance design and remains a challenge to the industry. This paper focuses on the effect of plastic deformation ahead of a notch/crack on the non-linearity of compliance curves of 6082-T651 aluminium alloy specimens to highlight a potential issue in the conventional compliance curve based crack closure measurement technique. Experimental and numerical simulation results demonstrate that plastic deformation ahead of the notch will introduce non-linear stress-strain behavior in the absence of crack closure. It is proposed that the effect of crack tip plasticity on the non-linearity of the compliance curve be separated to obtain reliable crack closure measurement.