M.Ing. (Mechanical Engineering) / High strength alloys such as titanium are widely used within applications that require specific material properties. These include high strength, high temperature as well as low weight applications. Thus a need arises to investigate the fundamental to understand the mechanics of how these materials are machined. Titanium alloys are known for the difficulties that arise during the machining thereof. Complexities arise due to its inherent material properties, the most important property being the retention of strength at high temperatures. In addition to maintaining its strength, it becomes highly chemically reactive with other materials at increased temperatures. All these factors contribute to extreme temperatures at the tool chip interface contributing to increased tool wear and shortened tool life. The aim of the research is to investigate the effect of machining on various cutting process parameters including cutting force, temperature, tool wear and surface finish for grade 2 and grade 5 titanium alloys during high speed turning. Grade 2 titanium is a commercially grade with lower mechanical properties, while Grade 5 is titanium alloy with substantially higher mechanical properties and is the most widely used titanium alloy. In addition an experimental setup was developed and verified to conduct fundamental research on the high speed machining of titanium alloys. A literature review was concluded with focus on the machining of titanium alloys. This was followed by the development of the experimental setup, measurement and compilation of data. The data was compiled into graphs and compared with the current research available. The research found that for the cuts performed, that cutting forces are independent of cooling applied and that no substantial variation was noted between the two grades. When temperatures were evaluated, dramatic drops in temperature were noted when coolant was applied. As temperatures increased, specifically during un-cooled cutting, the inserts deteriorated having an effect on the quality of the surfaces obtained. When coolant was applied, substantial temperature drops were achieved, improving tool life and directly improving surface finishes. The best surface finish was achieved for higher cutting speeds as and lower feed rates. This phenomenon was found for both grades of titanium evaluated. The largest amount of tool wear was noted for the highest cutting speeds, with increased values noted for Grade 5 in comparison with Grade 2. This phenomenon is noted for crater as well as flank wear.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:7784 |
| Date | 21 November 2013 |
| Creators | Kruger, Pieter |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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