Abstract
Cutting of soft materials is a common daily life experience (e.g., slicing of meat and cheese) and an essential operation in many industries, healthcare (e.g., surgery) and manufacturing (e.g., paint removal) among them. By measuring the cutting forces of the tool and examining the deformation mechanisms of the workpiece, the cutting process can be put on a strong scientific and technological footing. For it provides an ingenious method to measure the fracture energy, i.e., the specific resistance to cracking, of soft materials like plastics, thin films on substrates and nanocomposites at different cut-depths. The new knowledge gained improves tool design and optimizes cutting conditions to increase the cutting process efficiency with huge economic benefits. For example, cutting with sharp tools will enable the paint industry an effective solution to measure the adhesion energy and scrape paints from metal substrates. It will also provide a unique fracture energy index for food products for correlation with food quality and texture.
In this seminar, the speaker will present his recent work on the cutting behavior of polyolefins with different molecular weights and epoxies with different degree of cross-links. He investigates the effects of rake angle, cut depth, and tool sharpness as well as chip bending on the fracture energy obtained from the cutting theory. The results show that fracture has a critical role in the formation of the newly cut surface as the chip is separated from the workpiece by the cutting tool. The surface finish after cutting is dependent on the cutting depth and the ratio between fracture energy and yield strength. These new findings provide useful guidance for understanding the machining behaviour of soft materials like polymers.
About the speaker
Prof Yiu-Wing Mai received his PhD in Mechanical Engineering from the University of Hong Kong in 1972 and obtained a DEng from the University of Sydney in 1999. He was postdoctoral research assistant at the University of Michigan and Imperial College from 1974 to 1976. He joined the University of Sydney in 1976, and is currently University Chair and Personal Chair in Mechanical Engineering.
Prof Mai is a highly cited researcher in materials science and is recognized for his seminal work on fracture mechanics, characterization of advanced materials, and basic understanding of composite interfaces and crack-wake bridging which has revolutionized the microstructure design of tough fiber composites and ceramics. He has made significant, lasting impacts in these areas, and his research has contributed to the development of asbestos-free fiber cements, testing protocols for essential work of fracture of polymers, and improved composites manufacturing processes with global impact.
Prof Mai received prestigious awards including the Centenary Medal from the Australian Government, the Takeo Yokobori Gold Medal and the AFG Achievement Award from the Australian Fracture Group. He is a Fellow of the Royal Society of London, the Royal Academy of Engineering, the Australian Academy of Science and the Australian Academy of Technological Sciences and Engineering. In 2010, he was appointed a Member of the Order of Australia for his contributions to engineering, particularly in the fields of advanced composites and fracture research.
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