1,721,043 research outputs found
Advances in machinability of gamma titanium aluminides
No full textGamma titanium aluminides (γ-TiAl) have received an increasing industrial and academic attention in recent years. Due to their attractive combination of properties, they have been evaluated as important contenders for structural applications in the automotive and aerospace sectors, especially for the components simultaneously subjected to mechanical and thermal stresses. These heat-resistant intermetallic alloys show significantly lower density in comparison to nickel-based superalloys, high strength/weight ratio, high temperature strength, and good oxidation and fatigue resistance. At the same time, gamma titanium aluminides are regarded as difficult-to-cut materials, because of their high hardness and brittleness, low thermal conductivity, high chemical reactivity, and strong tendency to hardening. Poor machinability and, furthermore, the high manufacturing costs, limit the widespread use of those materials in the market. Moreover, while studies on their machinability with conventional and unconventional processes still require an in-depth analysis, a limited number of publications which have focused on conventional machining processes such as milling, turning, and drilling can be found in the scientific literature. In addition, the obtained results are strongly dependent on the specific alloys and on the production technology used. A deeper knowledge of γ-TiAl machinability is therefore necessary to match completely the manufacturing process (cutting conditions, process parameters, etc.) with the material, especially with varying alloying elements content. In this context, the research activities presented and discussed in the thesis are addressed to deepen the knowledge on machinability of different γ-TiAl alloys in cutting operations with defined cutting edges. The results obtained in milling, turning and drilling experimental investigations are analyzed in terms of tool wear mechanisms, tool lifetime, cutting forces, chip morphology, surface quality and integrity. Overall, with respect to the state of the art, the main key points of the research activities presented in the thesis include the machinability investigations of alloys produced by an innovative process as electron beam melting, the development of adapted nanostructured tool coatings obtained through a step-by-step tool optimization procedure, and the use of cryogenic cooling in comparison with other sustainable systems (as MQL) and with more traditional lubrication condition
Quality-conscious optimization of energy consumption in a grinding process applying sustainability indicators
No full textThe rising awareness of energy consumption and the environmental impact of manufacturing underline the need to implement structured approaches, such as a
life cycle assessment, or metrics for process evaluation. Energy savings on their own are not sufficient to increase the process efficiency of industrial finishing operations,
since the results, in terms of machined part quality, have to be accounted for. The research work presented in this paper applies sustainable development concepts to an industrial case study. A shaping grinding process (a flute grinding operation for tap manufacturing) has been assessed experimentally. The effects of variations in the
process parameters have been discussed, with respect to processing time, energy consumption, and product quality/integrity. Whenever the optimization goals are in contrast, a trade-off between product requirements and process sustainability has to be introduced. In order to achieve energy savings, without altering the performance
of the product, a specific efficiency sustainability indicator has been implemented and coupled to the life cycle inventory phase. The results provide a tool that can assist
the decision-making stage and can be incorporated into a business strategy development framework
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