Massachusetts Institute of Technology

Other

Antonios E Giannakopoulos

Subra Suresh

Jorge Alcala

Nitin P Padture

Rajendran Thampuran

Ole Jorgensen

Juthamas Jitcharoen

Marten Olsson

An article is provided that is highly resistant to localized normal indentation, or indentation tensile stresses, against its surface. The article is a stacked array of at least five layer units each having local anisotropy in at least one direction. Each unit has an adjacent unit that differs in a mechanical property, or offset in principle axis of anisotropy by less than 45&deg;. The article forms part of a construction constructed and positioned to withstand indentation, or contact damage, detrimental to its use having a component normal to any tangent of the surface. The article can be a stacked array of fiber-reinforced polymeric material, i.e., prepreg, with the fiber direction offset from each layer to the next by less than 45&deg;. Methods of making the article and methods of use of the article to resist impact are provided. Also provided are articles having surfaces, the surfaces being constructed and arranged to withstand sliding contact stress. The surfaces of these articles are functionally-graded.

Functionally-graded materials and the engineering of tribological resistance at surfaces

Depth sensing indentation and methodology for mechanical property measurements

An indentation measurement apparatus is retrofittable onto any of a variety of load-applying frames and includes a mount for mounting an indenter of any geometry (for example blunt or sharp). The arrangement is very stiff and mechanical values including Young's modulus, strain hardening exponent, yield strength, and hardness can be obtained from a single load/unload versus displacement test. A wide variety of materials can be tested using the apparatus. An optical probe can measure displacement of the indenter head relative to a sample. A new method of calculating strain hardening directly from load/displacement measurement is presented as is a new method of calculating strain hardening exponent.

Depth sensing indentation and methodology for mechanical property

Techniques for the determination of mechanical properties of homogenous or functionally-graded materials from indentation testing are presented. The technique is applicable to indentation on the nano-scale through the macro-scale including the geological scale. The technique involves creating a predictive load/depth relationship for a sample, providing an experimental load/depth relationship, comparing the experimental data to the predictive data, and determining a physical characteristic from the comparison.

Method and apparatus for determination of mechanical properties of

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Somerville, MA, United States of America

Antonios E Giannakopoulos