Browsing by Subject "Grain morphology"

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Open Access
Investigating the effect of CP titanium microstructure on the mechanics of microscale machining
(2019-09) Aksın, Alp
Metal cutting in microscale brings along many challenges and unanswered questions. Mechanical response of the material to the micro-cutting process is one of them, since feed values and the edge radius of the tool can be in the magnitude of order of the material's grain size. In addition, the grain morphology of the material may affect process outputs. This study investigates microstructure effects of the commercially pure titanium (CP Ti) based on analytical and mechanistic modeling approaches. A slip line field model was studied considering fracture toughness and edge radius effects. Orthogonal micro-cutting tests were performed on different morphologies at feed levels ranging from 0.25 to 6 µm per revolution and cutting force data were collected. Cut chip thickness values were measured by using SEM and used as in-process output in the model. The model outputs were fit to force data and unknown model parameters were identified. Those determined parameters were compared with measurements. The study show that the rake angle and tool edge radius parameters have a consistent disparity between measured and identified values. Evidence of possible wear and material build up at the tool have been observed. Using Bayesian inference, possible range of rake angle values have been further investigated and probability distributions of the rake value were identified for different feed levels. Micromilling of CP titanium has also been considered and a relationship between microscale orthogonal cutting and micromilling has been sought. CP titanium was tested by conducting full immersion micromilling experiments based on mechanistic modeling. In uence of the grain morphology on model coefficients, surface texture and hardness have been discussed.
Open Access
The morphological changes upon cryomilling of cellulose and concurrent generation of mechanoradicals
(Elsevier, 2019) Aksın, Alp; Karpat, Yiğit
Microstructural features such as grain size, grain morphology, and phase fractions have significant influence on process outputs of machining processes. During micro end milling where feed per tooth and depth of cut values are set comparable to grain size, process material interactions become more significant. The goal of this study is to investigate the influence of microstructural effects on process outputs during micro milling of cp-Ti work material. Micro milling experiments are performed to observe the process outputs as a function of grain size and grain morphology and a mechanistic approach has been used to explain their effects during micro milling.