Nadia Kourra

Study of Cutting Speed Variation in the Ultrasonic Assisted Drilling of Carbon Fibre Composites

Ultrasonic assisted drilling (UAD) has been proven effective for the thrust force reduction as compared to conventional drilling (CD) for same machining parameters. The following research was focused on the examination of exit delamination, machined surface and cutting temperature measurement in UAD and a comparison to that in CD at the cutting speeds of 0.942 m/min, 9.42 m/min, 94.2 m/min and 282.6 m/min at a constant feed rate of 0.05 mm/rev in the through-hole drilling of CFRP material. X-Ray computed tomography (CT) was used to identify the exit delamination, internal damage, circularity and center deviation in CD and UAD. A maximum of 82.8% reduction in the center deviation and 33.2% reduction in circularity of the holes were found when drilled in UAD as compared to those in CD. Furthermore, the cutting temperature in the drilling of CFRP has been measured and compared for both the cases of CD and UAD. Ultrasonic assistance produced 10°C higher cutting temperature than that in CD at the cutting speed of 282.6 m/min while at lower cutting speeds (0.942 m/min and 9.42 m/min), the cutting temperatures with and without ultrasonic assistance did not have a significant difference (2°C and 4°C respectively).

Non-destructive examination of additive manufactured acetabular hip prosthesis cups

The application of Additive Manufacturing (AM) in medicine is extensive with the production of anatomical models, endoprosthetics, surgical guides, implants and scaffold implants. This is due to its design flexibility and cost effectiveness when geometrical complexity is required. Total hip arthroplasty is a common surgical procedure with a prevalence increase of 0.72% in 20 years that it is expected to grow faster in the next decades. The work presented demonstrates a novel non-destructive, non-contact examination method utilising X-ray Computed Tomography (XCT) and image processing. This method examines an AM bone-mimetic structure that enhances bone ingrowth and implant fixation of acetabular hip prosthesis cups. The results of the image processing analysis include information on the interconnectivity of the bone-mimetic structure, local thickness and spatial distribution.

Metrological investigation of radiation filtration in x-ray computed tomography

X-ray Computed Tomography (CT) is a nondestructive evaluation method that gains recognition in dimensional metrology applications. During a CT scan, 2D radiographs are collected that are then reconstructed to a 3D model which allows non-destructive evaluation of the specimen and assists with the characterisations of defects. This technology has the potential to provide information unobtainable by other non-destructive, non-contact techniques. There are numerous factors that can affect the CT measurement results with varying measurement uncertainty such as shifts and changes of x-ray focal spot, geometrical alignment issues and environmental issues. This study investigates the effect of physical pre and post filtration on the resultant dimensional measurements. Here, a calibrated specimen is used based on one of the considered designs for the proposed ISO 10360-11 CT for dimensional measurements. The resultant in local variations of grey values in the volume is measured for different thicknesses of copper filtering placed before and after the scanned specimen, and the resultant threshold dependent and independent measurements are evaluated. The results provide information that assists the selection of filtration in order to reduce measurement error and improve dimensional measurements, and also demonstrate that post filtration should be considered when scanning specimens that generate large amounts of scatter.