Dissertação (mestrado) - Universidade Federal de Santa Catarina, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2014. / Made available in DSpace on 2014-08-06T18:04:10Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Abstract : The use of advanced ceramics has been limited by the high machining costs, with grinding and polishing accounting for 50-80% of the final product's total cost; and the inability of achieving satisfactory dimensional control and surface quality. Laser ablative processes are an alternative, considering the absence of wear-subjected tools and the possibility of very fine material removal. Although the research on laser ablation is a current topic of interest, with growing number of publications year after year, it's been focusing mainly on ultra-short pulses (in the order of pico- and femtoseconds), while the research on the low-cost and low-energy-consuming nanosecond regime (> 100 ns) is relatively scarce, specially for ceramics. This process outcomes are still difficult to predict, due to the many simultaneous and self-interacting physical processes that take place in a relatively short time. In this study, an experimental analysis has been carried out for a three-dimensional machining process with a 120 ns pulsed ytterbium fibre-laser on dense Al2O3 samples, initially through design of experiments, and later trough a step-by-step optimization procedure, evaluating ablation rate and resulting roughness. Then, surface morphology and fracture strength were evaluated for two of the "optimized" parameters sets. A very well-defined difference in removal rate and resulting surface topographies was observed, suggesting a threshold point between distinct ablation mechanisms. One of the combinations gave rise to interesting features of straight, angled shock-waves around melt pits. The fracture strength for both regimes also differed significantly, with a clear increase (121,6% e 163,5%) of the Weibull modulus combined with a decrease of the characteristic stress, compared to the non-ablated samples.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufsc.br:123456789/123313 |
| Date | January 2014 |
| Creators | Gomes, Diego Ribas |
| Contributors | Universidade Federal de Santa Catarina, Fredel, Márcio Celso, Janssen, Rolf |
| Source Sets | IBICT Brazilian ETDs |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | 75 p.| il., grafs., tabs. |
| Source | reponame:Repositório Institucional da UFSC, instname:Universidade Federal de Santa Catarina, instacron:UFSC |
| Rights | info:eu-repo/semantics/openAccess |
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