John W. Hutchinson
Talk Title: Shell Buckling—the old and the new
Hutchinson and his students work on problems in solid mechanics concerned with engineering materials and structures. Buckling and structural stability, elasticity, plasticity, fracture and micromechanics are all relevant in their research. Two examples of on going research activities are efforts to extend plasticity theory to small scales and the development of a mechanics framework for assessing thermal barrier coatings.
Strong size effects come into play at the micron scale in the plastic deformation of metals. The effect is tantamount to increased strength at smaller scales: smaller is stronger. The phenomenon derives from the generation of higher densities of dislocations when strain gradients occur at small scales. It has great importance for micron scale metal structures such as thin films and small MEMS devices. Conventional plasticity theory does not contain any size effect, and the effort of Professor Hutchinson and his collaborators is directed at the formulation of a physically correct continuum theory that encompasses a size effect. Efforts are underway to analyze new experimental data, to make contact with dislocation modeling, and to apply the theory to problems of technological significance.
Ceramic thermal barrier coatings (TBCs) are now widely used in aircraft and power generation turbines to shield engine blades and other metal components from high temperatures. A new generation of engines will exploit these coatings to enable higher operating temperatures. The technological challenge is to enhance the lifetime of the coatings under these more severe operating conditions. The durability of the coatings is limited by their tendency to delaminate and spall. There is a host of mechanics problems and issues waiting to be understood related to the performance of the coatings. Professor Hutchinson, his students and collaborators are involved with a larger community of engineers and material scientists who are actively exploring all aspects of TBCs.