Browsing by Author "Walton, I."

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    Abrasive machining with MQSL.
    (Cranfield University, 2011-07) Morris, Tom; Stephenson, David J.; Walton, I.; Nicholls, J. R.
    Grinding and polishing of engineered components are critical aspects of the precision manufacturing of high performance, quality assured products. Elevated process temperatures, however, are a common and for the most part undesirable feature of the grinding process. High process temperatures increase the likelihood of microstructural change within the immediate subsurface layer and are detrimental to the strength and performance of the manufactured products. Increasing processing costs and tighter environmental legislation are encouraging industry to seek innovative fluid application techniques as significant savings in production can be achieved. In this context, and with sponsorship from three industrial partners, namely; Fives Cinetic, Fuchs Lubricants plc and Southside Thermal Sciences Ltd, and also from the Engineering and Physical Science Research Council (EPSRC), this research aimed to develop an understanding of Minimum Quantity Solid Lubrication (MQSL) as a method for abrasive machining, with particular reference to the control of surface temperatures. Improving the lubricity of Minimum Quantity Lubrication (MQL) fluids reduces the frictional source of process heat and controls the finish surface temperature. The application of effective solid lubricants is known as Minimum Quantity Solid Lubrication (MQSL). Molybdenum Disulphide (MoS2), Calcium Fluoride (CaF2), and hexagonal Boron Nitride (hBN) were compared against a semi-synthetic water soluble machining fluid (Fuchs EcoCool). A series of Taguchi factorial experimental trials assessed their performances through ANOVA (ANalysis Of VAriance) statistical method. The hBN produced the lowest grinding temperatures of the solid lubricants tested, although they still remained higher than those achieved using the EcoCool control. The reduction of the machining fluid enabled a Charged Coupled Device (CCD) sensor to be fitted into the grinding machine. The recorded movement in the emitted spectrum from the grinding chips was compared to experimental and modelled process temperatures. This showed that the wavelengths of the chip light correlated to the temperature of the finish grinding surface. This greatly contributed to determining the feasibility of constructing a non-destructive, non-invasive, thermally-adaptive control system for controlling grinding surface temperatures.
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    Creating movable interfaces by micro-powder injection moulding
    (Elsevier, 2013-09-09) Attia, Usama M.; Hauata, M.; Walton, I.; Annicchiarico, Daniele; Alcock, Jeffrey R.
    This paper presents a novel in situ technique to produce articulated components with high-precision, micro-scale movable interfaces by micro-powder injection moulding (μPIM). The presented process route is based on the use of micro-scale sacrificial layer between the movable subcomponents which is eliminated during the debinding step, creating a dimensionally-controlled, micro-scale mobile interface. The fabrication technique combines the advantages of micro-powder overmoulding, catalytic debinding and sintering. The demonstrated example was a finger bone prosthesis joint consisting of two sub-components with an interface between components of 200 μm in size. The geometries of the sub-components were designed such that they are inseparable throughout the process whilst allowing them to move relative to each other after the debinding stage. The components produced showed the feasibility of the process route to produce readily-assembled meso-, and potentially micro-, scale articulated systems
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    Determining the onset of grinding burn using Magnetic Barkhausen Noise
    (Cranfield University, 2005) Opoku, Kevin S; Stephenson, David J.; Walton, I.
    A study of the quick non-destructive technique of Magnetic Barkhausen Noise (MBN) in detecting the onset of grinding burn in the absence of any microstructural changes during grinding has been undertaken. 51CrV4 Steel is a used in industry for manufacturing automotive parts (Nissan). Uniaxial tensile tests using a coarse surface whilst taking in situ MBN measurements were used to calibrate MBN to residual stress for hard and soft samples of 51CrV4. X-ray diffraction tests of some ground samples of hard and soft 51CrV4 samples were used to correlate the obtained calibration curves. A depth profile analysis was also carried out from results of MBN and XRD measurements of 51CrV4 soft and hard samples ground at different specific material removal rates. The MBN Vrms and Vpeak parameters in the elastic deformation region were shown to behave linearly with total stress. A predictive model to calculate residual stress values showed good correlation in terms of the direction but the magnitude of the error was poor within its working limits. The Vrms and Vpeak and FWHM also showed a sharp change in the trend during the change from compressive to tensile stress. The application of the MBN technique in detecting grinding burn before it happened meant that waste could be limited and grinding processes optimised without compromising the surface integrity of components.