Now showing 1 - 3 of 3
  • Publication
    Optimisation of cutting performance in drilling of aluminium alloy 7075 involving chilled air cooling under Taguchi method
    (Semarak Ilmu Publishing, 2025)
    Muhammad Hisyamuddin Rosli
    ;
    ; ;
    Muhammad Zikry Zainuddin
    ;
    Adel Ali Azawqari
    The use of lightweight Aluminium Alloy 7075 (AA7075) in aerospace and automotive industries is increasing due to its exceptional properties, such as high strength, good fatigue resistance, and excellent strength-to-weight ratio. However, this alloy is difficult to machine due to high ductility and heat generation during cutting. Cutting fluids are commonly used to deal with these problems, although they raise environmental concerns. The research aims to enhance drilling efficiency for AA7075, considering environmental impacts, through a greener method, a chilled air system. Their impact on tool wear and cutting force was evaluated through spindle speed, feed rate, and nozzle types by adopting the Taguchi method. Chisel edge wear was discovered to be a major contributor to tool wear. Lower feed rate and slower spindle speed using dual nozzle yielded better tool wear and cutting force performance. These findings provide feasible recommendations for industry practitioners seeking to employ eco-friendly chilled air systems to achieve optimal drilling efficiency for this type of material.
  • Publication
    Chilled Air System and Size Effect in Micro-milling of Nickel−Titanium Shape Memory Alloys
    ( 2020-03-01) ;
    Tarisai Mativenga P.
    ;
    Harrison G.
    Although Nickel-Titanium Shape Memory Alloys (NiTi SMAs) are used in a variety of applications due to their shape memory and superelasticity properties, their features of high ductility, temperature sensitivity, and strong work hardening render these materials difficult to machine. The viability of a new approach in improving the machinability through temperature control using chilled air system application was investigated. Differential scanning calorimetry was used to characterise material response to thermal loads. Microstructure phase identification was evaluated with X-ray diffraction. Micro-milling tests were performed using chilled air system and benchmarked to dry cutting and the use of minimum quantity lubricant (MQL). To augment lubrication, chilled air was also applied concurrently with MQL. Results indicated that the application of chilled air reduced cutting temperature and minimised burr height, while their simultaneous application with MQL further improved the machinability. Further investigation was conducted to explore the influence of the ploughing mechanism on machining performance and product quality. The results pointed to higher feed per tooth producing better outcomes. This paper puts forward a new hypothesis that the machinability could be improved by inhibiting or locking in phase transformation through temperature control, and optimising chip thickness, one of the principal parameters of size effect.
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  • Publication
    Machinability of nickel-titanium shape memory alloys under dry and chilled air cutting conditions
    ( 2023) ;
    Paul Tarisai Mativenga
    Nickel-titanium (NiTi) shape memory alloys (SMAs) undergo phase transformation between austenitic and martensitic phases in response to applied thermal or mechanical stress, resulting in unique properties and applications. However, machinability often becomes challenging due to property and temperature sensitivity attributes. The use of chilled air to influence machinability in macro-milling was investigated in this study. Other than that, differential scanning calorimetry (DSC) was used to determine the temperature of phase transformation. The results showed that milling with chilled air and minimal lubrication significantly improved machining performance by reducing tool wear and burr formation. Moreover, surface quality has also improved significantly. A notable discovery is that the machining process can change the critical conditions for phase transition, enabling new performance capability of tuning material hysteresis.