Past projects

PAST PROJECTS

Sub-surface fatigue crack detection in ultra-high molecular weight polyethylene.

Polyethylene wear resulting from fatigue cracks in the polyethylene tibial insert is one of the leading causes for a prosthetic knee joint to fail. Fatigue cracks originate just below the articulating surface - where stress due to in-vivo cyclic loading is maximum - and propagate through the material, creating wear particles. We have developed an experimental technique, based on translucency measurements, to determine the size and location of sub-surface fatigue cracks in a polyethylene tibial insert. In addition, we have used finite element modeling to simulate contact stress resulting from in-vivo loading, and compared experimental measurements with predictions from FEM simulations.

 
   

Elastic contact of rough surfaces.

We have studied how different statistical and deterministic methods to calculate the topography parameters of contacting rough surfaces yield different results for the same physical surface, and we have derived guidelines on how to mitigate this problem. In addition, we have investigated how different surface topography results affect the outcome of several multi-asperity contact models, in terms of real area of contact, mean separation, and normal load.

Ultrasound directed self-assembly of nanostructures using surface acoustic wave (SAW) devices.

We have fabricate surface acoustic wave (SAW) devices on a Lithium Niobate piezoelectric substrate. Using these SAW devices, we have manipulate nanostructures into user-specified patterns and templates.

Design of an acoustic camera for use in optically opaque liquids.

We have developed an acoustic camera that is capable of "seeing" through optically opaque liquids, even with high viscosity. This camera is based on nonlinear acoustic sensors and transducers that generate a low-frequency collimated ultrasound beam that is capable of propagating through a highly attenuating medium without loss of imaging resolution. This acoustic camera finds application in e.g. the oil exploration industry. During drilling operations it is oftentimes necessary to lower a camera down the borehole to inspect the casing wall or to identify parts or tools that may have broken off or need to be removed from the borehole to prevent damage. The optically opaque mixture of oil, water, and drilling fluid makes it difficult to use optical cameras.