Brittle materials such as silicon and ceramics are used extensively in the semiconductor industry to make component parts. Materials cut to have a mirror-like surface yield the best performance, but the precision required is difficult to achieve at such a tiny scale.
Xinquan Zhang at A*STAR’s Singapore Institute of Manufacturing Technology, along with co-workers at the same institute and the National University of Singapore, has developed a computer model that allows engineers to predict the best way of cutting different materials using vibration-assisted machining (VAM)1. This technique periodically interrupts the cutting process via the application of small-amplitude and high-frequency displacement to the cutting tool.
“Many researchers have observed that using VAM instead of conventional cutting techniques allows them to make cleaner, fracture-free cuts to most brittle materials,” explains Zhang. “Because no theory or model exists to explain or predict this phenomenon, we decided to investigate.”
At the nanoscale, brittle materials exhibit a certain degree of plasticity. Each material has a particular depth of cut that allows clean shearing to occur without chipping or fracturing on, or beneath, its surface. This point, known as the critical undeformed chip thickness, is directly correlated with material properties and machining conditions.
Zhang and his team studied the behavior of different brittle materials cut with VAM, during which two modes of cutting occur. In the ductile mode, plastic deformation caused by cutting is followed by elastic rebound and recovery of the material structure between vibrations. The brittle mode, on the other hand, removes material by uncontrolled crack propagation. Making a clean cut during ductile mode — before the brittle mode dominates — is therefore desirable.
The researchers modeled the energy consumption of each mode in terms of material removal as the vibrating tool moved, taking into account tool geometry, material properties and the cutting speed.
“By examining energy consumption and material deformation we were able to describe the mechanics when VAM moved from the ductile to the brittle mode,” explains Zhang. “We then established a model to predict [the] critical undeformed chip thicknesses by finding the transition point between the two modes.”
By examining energy consumption and material deformation we were able to describe the mechanics when VAM moved from the ductile to the brittle mode,” explains Zhang. “We then established a model to predict [the] critical undeformed chip thicknesses by finding the transition point between the two modes.”
Through a series of experiments, the team verified that the model accurately predicts the critical undeformed chip thicknesses of single-crystal silicon when cut at various VAM speeds.
“Our model will help engineers to select optimized machining parameters depending on their desired material,” says Zhang. “Advantages could include higher productivity, lower costs, and improved product quality for semiconductor parts and other nanoscale technologies.”
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing Technology
Zhang, X., Arif, M., Liu, K., Kumar, A. S. & Rahman, M. A model to predict the critical undeformed chip thickness in vibration-assisted machining of brittle materials. International Journal of Machine Tools and Manufacture 69, 57–66 (2013).
More articles from Materials Sciences:
Accelerated corrosion testing of silver provides clues about performance in atmospheric conditions
04.12.2013 | NACE International
New Effect Couples Electricity and Magnetism in Materials
28.11.2013 | Vienna University of Technology
Quantum entanglement, a perplexing phenomenon of quantum mechanics that Albert Einstein once referred to as “spooky action at a distance,” could be even spookier than Einstein perceived.
Physicists at the University of Washington and Stony Brook University in New York believe the phenomenon might be intrinsically linked with wormholes, hypothetical features of space-time that in popular science fiction can provide a much-faster-than-light shortcut from one part of the universe to another.
But here’s the catch: One couldn’t actually ...
A star is formed when a large cloud of gas and dust condenses and eventually becomes so dense that it collapses into a ball of gas, where the pressure heats the matter, creating a glowing gas ball – a star is born.
New research from the Niels Bohr Institute, among others, shows that a young, newly formed star in the Milky Way had such an explosive growth, that it was initially about 100 times brighter than it is now. The results are published in the scientific journal, Astrophysical Journal Letters.
The young ...
EPFL scientists have shown how to achieve a dramatic increase in the capacity of optical fibers; Their simple, innovative solution reduces the amount of space required between the pulses of light that transport data
Optical fibers carry data in the form of pulses of light over distances of thousands of miles at amazing speeds. They are one of the glories of modern telecommunications technology.
However, their capacity is limited, because the pulses of light need to be lined up one after the other in ...
NASA's Hurricane and Severe Storms Sentinel airborne mission known as HS3 wrapped up for the 2013 Atlantic Ocean hurricane season at the end of September, and had several highlights. HS3 will return to NASA’s Wallops Flight Facility in Wallops Island, Va., for the 2014 Atlantic hurricane season.
During the 2013 mission, two unmanned Global Hawks flew from Wallops for the first time. The mission highlights included studying the Saharan Air Layer, following the genesis of a tropical storm, finding a unique hybrid core or center circulation in a redeveloped storm, obtaining measurements on the strongest side of ...
Nanosponges that soak up a dangerous pore-forming toxin produced by MRSA (methicillin-resistant Staphylococcus aureus) could serve as a safe and effective vaccine against this toxin.
This "nanosponge vaccine" enabled the immune systems of mice to block the adverse effects of the alpha-haemolysin toxin from MRSA—both within the bloodstream and on the skin. Nanoengineers from the University of California, San Diego described the safety and efficacy of this nanosponge vaccine in the December 1 issue of ...
04.12.2013 | Health and Medicine
04.12.2013 | Materials Sciences
04.12.2013 | Ecology, The Environment and Conservation
04.12.2013 | Event News
12.11.2013 | Event News
29.10.2013 | Event News