Research
We have the following facilities and equipment:
- 24 CPU multiprocessor for FEA Computational studies
- Testing machines with 1 kN to 600 kN load cells
- Capability for static, cyclic and creep testing of materials
- Facilities for metallography, optical microscopes, AFM and SEM
Our research is sponsored by EPSRC, British Energy, EU, ALSTOM Power, Hitachi, Rolls Royce, FIAT, Siemens, 3M Volvo Aerospace. Health and Safety Executive and Teer Coatings
Examples of our research:
Analysis of Cracked Geometries
Fracture invariably occurs due to the initiation and growth of microcracks within a material. The application of fracture mechanics can provide insight into the conditions under which microcracks can extend. This figure illustrates contours of equivalent (von Mises) stress indicating the concentration of stress at the sharp crack tip in a compact tension (CT) specimen. Fracture mechanics provides a means to interpret the complex stress and strain states in the vicinity of defects.
Micromechanics studies of material microstructures
Through unit cell finite element studies, using a representative volume element, the deformation characteristics of an alloy or composite are examined. The influence of the material microstructure on the macroscale response can thus be determined. The figure illustrates contours of inelastic strain in a single crystal nickel-base superalloy (CM186) subjected to tensile loading at 950 C.
Computational studies of structural components using mechanistic constitutive material models
The constitutive models developed by the group have been used in the study of the failure of single crystal gas turbine blades.
Contour plots of the steady state temperature distribution in a gas turbine blade and the corresponding accumulated inelastic strain after 50,000 hours, a typical design life are illustrated. The model predicts a localised deformation region near the blade root.
Computational modelling of crack growth using cohesive elements
In this work crack growth is explicitly taken into account through the use of cohesive elements between “material” elements. The cohesive ligaments exhibit damage until fracture according to a given cohesive law (see figure). This approach allows the simulation of crack initiation and propagation and accounting for interaction with the surrounding material to predict the rate of growth of a crack within a material.
The figure illustrates crack growth in a single crystal nickel alloy (PWA1483) specimen loaded in mode I at 950 C. Cohesive elements are inserted along a straight crack path, the stress normal to the crack path is relaxing behind the crack front as the crack grows.
