U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by:

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 26 - 50 of 101

Bulk Silicon Is Susceptible to Fatigue

November 19, 2007
Author(s)
Sanjit Bhowmick, Juan J. Melendez-Martinez, Brian R. Lawn
It has long been held that bulk silicon is immune from fatigue. We present contrary evidence demonstrating severe fatigue in macroscale cracks produced in cyclic loading of single-crystal silicon with a sphere indenter. The key ingredient is a component of

Crack Propagation Across an Adhesive Interlayer in Flexural Loading

October 8, 2007
Author(s)
James J. Lee, H Chai, Isabel K. Lloyd, Brian R. Lawn
Crack propagation across interlayers separating adjoining brittle plates in flexure is studied using a model glass/epoxy/glass system. A transverse starter crack in the center glass plate is made to propagate to the nearest epoxy interface, where it

Margin Failures in Crown-Like Brittle Structures: Off-Axis Loading

June 11, 2007
Author(s)
Chris Ford, T Qasim, M T. Bush, X Z. Hu, Mahek Shah, Vibhu Saxena, Brian R. Lawn
The effect of off-axis loading of compliant indenters on the initiation of cracks at the margins of dental crown-like dome structures consisting of glass shells back-filled with an epoxy resin is examined. As in previous studies on similar structures but

Role of Indenter Material and Size in Veneer Failure of Brittle Layer Structures

October 24, 2006
Author(s)
Sanjit Bhowmick, Juan J. Melendez-Martinez, Ilja Hermann, Yu Zhang, Brian R. Lawn
The roles of indenter material and size in the failure of brittle veneer layers in all-ceramic crown-like structures are studied. Glass veneer layers 1 mm thick bonded to alumina layers 0.5 mm thick on polycarbonate bases (representative of porcelain

Role of Core Support Material in Veneer Failure of Brittle Layer Structures

September 26, 2006
Author(s)
Ilja Hermann, Sanjit Bhowmick, Brian R. Lawn
A study is made of veneer failure by cracking in all-ceramic crown-like layer structures. Model trilayers consisting of a 1 mm thick external glass layer (veneer) joined to a 0.5 mm thick inner stiff and hard ceramic support layer (core) by epoxy bonding

Failure of Glass Layers on Polymeric Substrates From Vickers Indentation

March 25, 2006
Author(s)
Herzl Chai, Brian R. Lawn
A study is made of median crack evolution in brittle coatings subjected to sharp contacts. A model bilayer system consisting of a glass plate bonded to a polycarbonate base, with a Vickers pyramid as indenter, is used to demonstrate the evolution in situ

Deep-Penetrating Conical Cracks in Brittle Layers from Hydraulic Cyclic Contact

January 1, 2005
Author(s)
Yu Zhang, Jun-Feng Song, Brian R. Lawn
A study is made of fracture from cyclic loading of WC spheres on the top surfaces of thick (1 mm) brittle layers on polymeric substrates, as representative of repetitive occlusal contact on dental crown structures. The advantage of glass layers is that

Contact Damage in Brittle Coating Layers: Influence of Surface Curvature

December 1, 2004
Author(s)
T Qasim, M T. Bush, X Z. Hu, Brian R. Lawn
Fracture from indentation by a hard sphere on bilayer systems composed of curved brittle coating layers on compliant polymeric substrates is investigated, in simulation of dental crown structures. Glass plates 1 mm thick are used are used as representative

Competing Damage Modes in All-Ceramic Crowns: Fatigue and Lifetime

November 15, 2004
Author(s)
Yu Zhang, Brian R. Lawn
A study is made of fracture from cyclic loading of WC spheres on the surfaces of brittle layers on compliant substrates, as representative of repetitive occlusal contact on dental crowns. Several damage modes radial cracks at both top surface and

Evaluation of Elastic Modulus and Hardness of Thin Films By Nanoindentation

October 1, 2004
Author(s)
Yeon-Gil G. Jung, Brian R. Lawn, M Martyniuk, H Huang, X Z. Hu
Simple equations are proposed for determining elastic modulus and hardness properties of thin films on substrates from nanoindentation experiments. The empirical formulation relates the modulus E and hardness H of the film/substrate bilayer to