The objective of this work was to develop a new method for establishing the coefficient of friction for the machining conditions found on the rake face of a cutting tool. Critical aspects include the high pressures and high temperatures in the cutting zone. Using the base of an existing High-load High Temperature tribometer an adaptation referred to as a double-sided pin was implemented. The objectives were two-fold to improve the repeatability of the measurements and reduce the setup time by simplifying the alignment problems experienced on the previously used system.
The concept of the new setup is to press a double-end spherical pin made of the tool material between two flat surfaces made of workpiece material and rotating it using a string connected to a slider module. The normal load applied, the friction force needed to rotate the pin together with the temperature provided by a welder are then gathered and with the measurements of the imprints the coefficient of friction under specific loads can be established.
This work also studied the impact on the tests of pin radius and roughness of the pin surface in order to stablish the measurement limitations and conditions for a successful test.
Roughness of the pin had a significant impact on coefficient of friction results. Pins with roughness values around Ra = 0.5 demonstrated half the values of coefficient of friction than pins with Ra = 0.05. This was due the wear and the penetration of the pin into the workpiece sample material. The increase in pin dimensions facilitated testing on softer materials like AISI 1045. It was found to avoid seizure conditions but could not achieve pressures typical of machining difficult to cut materials like Ti-6Al-4V. The increase in pin size also helped in developing an understanding of how to measure the temperature at the contact zone between the pin and disk. Final testing showed a system repeatability of 8% was achieved with setup time reduced by approximately five times. / Thesis / Master of Science in Mechanical Engineering (MSME)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26181 |
| Date | January 2020 |
| Creators | Mella-Miranda, Maximiliano Hernan |
| Contributors | Veldhuis, Stephen C., Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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