<p> Burr formation is a frequent problem in metal cutting. Burrs, which are defined as undesired projections of material resulting from plastic deformation, affect the precision of machined components and can negatively affect the assembly process. One common burr is the exit burr that forms when drilling ductile materials such as aluminum alloy. Deburring, the process of removing burrs, can account for up to 30% of the total production cost. If the burr size can be reduced, the deburring effort can also be reduced or even eliminated, resulting in an improvement in productivity and an increase in profit. </p> <p> There are different methods to reduce burr formation in drilling. One method is known as vibration assisted drilling. Vibration assisted drilling has been reported as an effective method to reduce burr height without reducing the material removal rate or permanently altering the mechanical behavior of the workpiece material. Other reported benefits of vibration assisted drilling include improvement of tool life and better machined surface quality. However, it has been reported that poor choice of vibration conditions (frequency and amplitude) can increase burr height. No accurate analytical model exists in the current literature that can predict the exit burr height for vibration assisted drilling. To predict exit burr height, a model capable of predicting thrust force accurately is important because higher thrust force produces larger exit burr. Clearly there is a need to develop these models. </p> <p> This thesis presents the development of analytical models for predicting thrust force and exit burr height for vibration assisted drilling of aluminum 6061-T6. The developed models incorporate all significant characteristics of vibration assisted drilling to achieve accurate predictions. Drilling experiments were performed over a range of cutting and vibration conditions. The experimental results demonstrate that the developed thrust force model improves the accuracy by up to 45% in comparison to the existing vibration assisted drilling models. The developed burr height model accurately predicts the exit burr height for vibration assisted drilling, with an averaged deviation of 10% from the experimental results. The developed models are also applicable to conventional drilling. Comparing with the existing drilling models, the new models improve the accuracy of thrust force and burr height predictions by 6 and 36% respectively. A fast analytical method has also been developed that predicts the favourable vibration conditions that minimize burr height. The predictions obtained using this method are consistent with the experimental results. Drilling experiments for combined frequency vibration assisted drilling were also performed over a range of vibration conditions. The experimental results demonstrate that combining two different favourable vibration conditions together produces greater mean thrust force reduction than using a single frequency vibration assistance. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19019 |
| Date | 03 1900 |
| Creators | Chang, Simon, Shuet Fung |
| Contributors | Bone, Gary M., Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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