Other

California Institute of Technology

Inventium LLC

Antonios Giannakopoulos

Subra Suresh

Ares J Rosakis

Ilan Blech

Techniques for determining large deformation of layered or graded structures to include effects of body forces such as gravity, electrostatic or electromagnetic forces, and other forces that uniformly distribute over the structures, support forces, and concentrated forces. A real-time stress monitoring system is also disclosed to provide in-situ monitoring of a device based on the large deformation analytical approach. A coherent gradient sensing module, for example, may be included in such a system.

Determining large deformations and stresses of layered and graded structures to include effects of body forces

Provided are methods and apparatus for determining from indentation testing the preexisting stress and/or effective strain in a section of a material. The invention also provides methods and apparatus for determining the variation of the stress with depth in the material (e.g. the gradient). According to the invention, first data are provided from an indentation test of the stressed (or strained) section. The stress (or effective strain) can then be determined from the first data and from second data characteristic of the material, such as a stress-strain curve. Second data can also be obtained from an additional indentation test of a section having a known stress. The methods provided herein are suitable for programming on a general purpose computer or calculator.

Method and apparatus for determining preexisting stresses based on indentation or other mechanical probing of the material

Method and apparatus for determining preexisting stresses based on

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Antonios Giannakopoulos