Analysis of the scratch test for cohesive-frictional materials

In this thesis we develop analytical solutions for the relations between scratch hardness and strength properties of cohesive-frictional materials of the Mohr-Coulomb and Drucker-Prager type. Based on the lower-bound yield design approach, closed form solutions are derived for frictionless scratch devices, and validated against computational upper bound and elastoplastic Finite Element solutions. The influence of friction at the blade{material interface is also investigated, for which a simple computational optimization is proposed. The model is extended to porous cohesive-frictional materials through the use of a homogenized strength criterion based on the Linear Comparison Composite theory. Relations between scratch hardness, porosity and strength properties are proposed in the form of fitted functions. Illustrated for scratch tests on cement paste, we show that the proposed solutions provide a convenient way to determine estimates of cohesion and friction parameters from scratch data, and may serve as a benchmark to identify the relevance of strength models for scratch test analysis.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Bard, Romain (Romain M.)

Advisor dc:contributor.advisor

• Franz-Josef Ulm.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/61521

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/61521