University of Wisconsin Madison College of Engineering
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Tim Kamp and Wendy Crone.

Tim Kamp and Wendy Crone. Photo: David Nevala.

 

The Mechanics of Materials group at UW-Madison combines the study of mechanics (the study of forces, stresses, deformation and motion as applied to engineering structures) and materials science (the study of material development, fabrication, chemical composition, microstructure and properties) to study a wide variety of engineering problems. We merge these disciplines to dramatically enhance our capability both to understand and characterize existing materials and to invent exceptional new materials. The Mechanics of Materials group comprises six faculty members in the Department of Materials Science and Engineering and the Department of Engineering Physics. They have active programs in the following areas:

 

Materials with extreme and unique properties

 

In Professor Lakes' laboratory, he and his students synthesize and characterize novel materials for engineering applications. Materials that undergo phase transformation are of interest in the context of viscoelastic damping and of negative stiffness. They have developed new materials with reversed properties, including negative Poisson's ratio, negative stiffness, and negative thermal expansion. Designed materials can have thermal expansion or piezoelectric sensitivity of arbitrarily large magnitude. Professor Lakes and his students have demonstrated, in the lab, composite materials stiffer than diamond over a temperature range.

 

Professor Drugan and his students collaborate with Professor Lakes on these projects as well, enhancing the understanding of the mechanics of these materials with illuminating theoretical models. In particular, they have developed models regarding the stability of materials with negative stiffness.

 

Biomaterials

 

Professor Crone studies the response of stem cells to a surrounding three-dimensional hydrogel matrix. The objective of this research is to test the influence of hydrogel material properties and mechanical stimulation on the differentiation of stem cells. Hydrogels have been shown to have promise for a range of biomaterials and biomedical device applications, including cell scaffolding, artificial tissues, wound repair, drug delivery, and microfluidic devices. This work ultimately will impact the development of tissue-engineered constructs for cardiac repair.

 

Professor Crone also has projects related to biocompatibility of engineering materials. Biomedical devices such as stents and vascular grafts are often coated with various materials to prevent problems such as clotting around the instrument. Typically, the base material provides the desired mechanical properties while the coating provides biocompatibility. An alternative approach is to make the base material biocompatible. Our reach has focused on modifying the surfaces of nickel-titanium (NiTi) shape-memory alloys and developing polyurethane-based polymers that possess mechanical properties similar to the surrounding biological materials. Matching the mechanical properties (especially the stiffness) of the device to the surrounding structures results in better performance.

 

Geologic materials and soils

 

Professor Plesha and his students study discrete element methods (DEM), in which materials are modeled in a particle-by-particle manner. The technique is especially effective for applications to particulate materials, such as soil and powder, but is also applicable to modeling solids and the degradation of solids into particulates. At UW-Madison, we are involved with developing new enhancements to DEM, such as clustering to model particles of arbitrary rough shape, megaclustering to model solids and damage of solids, and development of new time integration methods to allow for more rapid computing.

 

Fracture mechanics

 

Professor Drugan is an international expert in theoretical fracture mechanics. He has carried out numerous studies of fracture in ductile materials, dynamics fragmentation of bodies absorbing energy over very short time scales, and nanoscale fracture (often governed by the mechanics of individual defects).