Steve Bull - Current research
The group is active in research on the following projects:
- Mechanics of indentation. Interpretation of depth-sensing
indentation experiments. Modelling of loading and unloading segments. Ultra-low
load experiments and AFM analysis. Indentation cracking. Creep and time-dependent
- Residual stress and strain in ultra-thin
films. Solar control coatings on glass. Strained Si on SiGe for high speed
- Reliability of back-end metallisation. The relationship
between residual stress generation and relaxation and the reliability of metallisation
for microelectronic devices is being investigated using a combination of process
modelling and stress sensor design.
- Mechanical modelling of coating/substrate systems. Plane, membrane
and empirical models. Predictive hardness modelling using energy-based methods.
- Mechanical and Tribological Properties of CNx. In
attempting to make crystalline carbon nitride many workers have made amorphous
CNx films. These have very interesting mechanical properties - they are apparently
very hard but have a lower elastic modulus than might be expected. The group
is looking at ways of analysing the mechanical properties of these materials
- Micropitting failure of Gears. Micropitting is
becoming an increasingly important gear failure mode though it was originally
only assumed to be a minor blemish. Macropitting or flank-initiated bending
failure can both arise from micropits and this is becoming an increasing problem
as more highly formulated lubricant additive packages are used. The group
is working on the causes and control of micropitting
- Properties and processing of soft magnetic composite materials
Soft magnetic composites have been developed with low eddy current losses
and are showing promise for use in a range of electrical machines. However,
the damage introduced into the material during processing can seriously reduce
the magnetic properties of these materials. The group is working on methods
to improve the processing to improve the performance of these materials.
- Scratch testing of polymers and polymer coatings.
The scratch test is traditionally used to assess the adhesion of hard coatings
but can also be applied in other systems. The group is currently working on
its use to assess marine protection coatings.
- Tribology of composites. Structural composites
for use on slip-lauched boats need to maintain low friction and wear during
sliding. However, the heat generated during sliding leads to matrix degradation
and high friction coefficients. A current test programme is looking for composite
materials or coatings for composites which avoid this problem.
page was last modified on 28th July 2007.
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