Enhancing the student role in the feedback process by applying a semantics approach

It is a well-known statement in pedagogy that the way we teach students should also assess them. An effective and more realistic method of teaching and assessing students in professional qualifications is by applying it to real world applications, such as career perspectives and job responsibility requiring critical and logical thinking and working in a team. An LCT approach can enable students to see the future application of real-world applications and abstract knowledge including the theoretical and technical knowledge of engineering disciplines. All these important tools are part of learning and assessing processes in engineering education.National Research Foundatio

Numerical and experimental investigation of directional solidification in vacuum investment casting of superalloys

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Mechanical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2013High temperatures encountered in combustion chambers of jet engines has demanded the creation of new technologies and new materials for the construction of one of the most critical elements of these systems - the stator and rotor turbine blades. They have to withstand extreme temperatures for extended periods without the loss of mechanical strength, conditions under which many steels and alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. The high temperature creep mechanism of grain boundary sliding has limited the operation capability of fine-grained equiaxed castings. Higher operating temperatures were achieved with higher alloy contents and coarse-grained equiaxed castings. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. However, notwithstanding these improvements, high temperature resistant alloys formed as single crystal structures offer the necessary material properties for safe performance under these extreme conditions. Damage to turbine blade surfaces is often caused by oxidation and hot corrosion. For this reason, turbine blades are coated with a thermal barrier coating (TBC), which consists of ceramic materials that reduce the heat flux through the airfoil. In this research work, modelling and simulation techniques were initially used to study the directional solidification (DS) of crystal structures during vacuum investment casting. The modelling of the solidification process was implemented using a Finite Element casting simulation software, ProCAST, to predict thermal and flow profiles. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this research was therefore to investigate the effect of the solidification rate (or withdrawal velocity) on the quality of SC castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting. The SC castings were heat treated to improve the grain structure for enhanced creep resistance. The heat treated SC castings were inspected by X-ray diffraction to analyse crystallographic orientation and chemical composition; and by SEM, OP (optical microscopy) and microprobe analysis to analyse the microstructure; in addition to macrostructural investigations. In the experimental analysis, the formation of new grains ahead of the solidi/liquid interface and the effect of dendrite packing patterns on the primary dendrite spacing were investigated. Creep tests were conducted to compare the creep properties of the SC castings for different withdrawal rates, and to draw conclusions regarding the effect of withdrawal rate on the microstructure (and hence the creep properties) of SC castings

EDITORIAL: WHAT SHELFIES CAN TELL US ABOUT PANDEMIC LIFE

There are two stories to tell in this multimodal special issue of Digital Culture and Education. One story involves a group of female academics in need of inspiration during pandemic days who decided to produce a multimodal special issue. The other story is a colourful whistle-stop tour of public and private shelves. The through-line connecting both stories is Covid lives lived over a multitude days and ways framed by objects, rites, restrictions interspersed with nature walks, YouTube yoga, and cats on keyboards. Shimmering, fragile, and captive, pandemic life remains in our minds and hearts forever. This issue visualises these extraordinary moments through shelves of all sorts, shapes, and size

Investigation of the effect of solidification velocity on the quality of single crystal turbine blades

The occurrence of high temperatures in combustion chambers of jet engines and gas turbines has led to the demand for new technologies and new materials for the manufacture of one of the most critical elements of these systems - the turbine blades. These elements have to withstand extreme temperatures for extended periods without loss of mechanical strength, conditions under which many alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. High temperature resistant alloys formed as single crystal (SX) structures offer the necessary material properties for safe performance under such extreme conditions. Modelling and simulation techniques were first used to study the directional solidification (DS) of crystal structures during vacuum investment casting. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this study was therefore to investigate the effect of the solidification rate on the quality of SX castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting

Framing Identities Using Shelfies: Bridging Private and Professional Spaces

This visual essay investigated how material objects frame and represent our self and identity, specifically focusing on curating different parts of identity through objects on bookshelves in online spaces. For the purpose of this study, a mixed method methodology was adopted where data was collected through semi-structured interviews and visual analysis (audio/video). There were six participants in this study who are academics from different higher education institutions with a wide range of research interests. The interviews were administered by the participants in pairs via an online platform and the video calls were recorded for data analysis purposes. The data analysis showed that shelfies reveal a specific place of our working environment in very concrete materiality, yet they also contain references to the invisible non-representational side of the social spaces that we interact with. It was clear from the findings that both parts of our identities (personal and professional) were portrayed in shelfies through the use of different materials and objects which were arranged in different styles