Materials & Mechanics at the University of Cape Town
Power generating plants operate under highly demanding conditions that include high temperature, high stress, oxidation and corrosion, and complex tribological environments. In its most basic form, plant reliability is critically dependent on the integrity of a broad range of engineering materials (mostly metals) that make up structures, machines and systems within the plant.
Given the anticipated plant life-time, material integrity is expected to remain within the design performance for periods often in excess of 300 000 hours. Consequently, accurate characterisation of the material condition with regards to the damage level, and prediction of the damage that occurs during exposure to operating conditions, and concomitant loss in design properties, is necessary. The situation is further complicated by repair activities, particularly those involving welding, that alter existing materials and could disadvantage integrity. New material developments are required to handle these challenges and an industry must be developed to manage the use of new materials during design, construction and maintenance while existing plants continue to produce the most energy at the lowest cost.
The SC activities are directed towards the most urgent challenges in this field. The focus is on high temperature behaviour, fatigue and corrosion, with emphasis on materials utilised in power generation. Research will explore the influence of service operating environments on performance in order to:
- better predict life of engineering materials and components in power generating plant;
- optimise material selection for plant construction, improve manufacturing technologies including welding;
- improve the reliability of material and component integrity monitoring.
Seven focus areas have been identified by Eskom:
- physical metallurgy and metallography;
- structural integrity;
- high temperature behaviour (including creep and fatigue);
- environmental degradation (including corrosion);
- welding metallurgy and processes;
- materials modelling;
- non-destructive evaluation (NDE).
The principle research objective lies in integrity management of a range of materials within Eskom’s fleet. As such, the key aspects are monitoring and understanding, modelling and predicting of prevalent material damage mechanisms. Detailed research questions include creep life assessment of metal alloys and welded joints, fracture and fatigue measurement and modelling of boiler tubes and other high temperature components, stress corrosion cracking (SCC), creep rupture properties of advanced materials, the welding thermal cycle effect on service properties and the use of NDE to assess and monitor material integrity and remnant life. The research is categorised in three major parts: (i) sample allocation and materials testing, (ii) investigation and understanding of microstructural processes, and (iii) modelling of material behaviour.