Extracting Stress-Strain and Compressive Yield Stress Information from Spherical Indentation

In recent years, instrumented indentation has become increasingly used to measure mechanical properties such as elastic modulus and fracture toughness at the micrometer scale. In this work, an experimental method is developed to estimate stressstrain behavior using indentation load-displacement and...

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Bibliographic Details
Main Authors: Juliano, Thomas F, VanLandingham, Mark R, Weerasooriya, Tusit, Moy, Paul
Format: Report
Language:English
Subjects:
Armor
CERAMIC MATERIALS
COMPRESSIVE PROPERTIES
EXPERIMENTAL DATA
EXTRACTION
FRACTURE(MECHANICS)
GRAPHS
MEASUREMENT
MECHANICAL PROPERTIES
Mechanics
MICROMETERS
MODULUS OF ELASTICITY
POLYCARBONATES
ROLLED HOMOGENEOUS ARMOR
SCALE
STIFFNESS
STRESS STRAIN RELATIONS
TEST AND EVALUATION
TITANIUM ALLOYS
TOUGHNESS
TUNGSTEN CARBIDES
YIELD
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Summary:In recent years, instrumented indentation has become increasingly used to measure mechanical properties such as elastic modulus and fracture toughness at the micrometer scale. In this work, an experimental method is developed to estimate stressstrain behavior using indentation load-displacement and continuous stiffness measurement data. An attempt is made to subtract plastic behavior out of the loading curve to generate stress-strain data from which elastic modulus and yield stress can be determined. Indentation data generated using three indentation tips with spherical caps (20-, 50-, and 500- m radii) are compared to bulk mechanical test data for a number of materials important for U.S. Army applications, including polycarbonate, polymethymethacrylate, a tungsten carbide ceramic composite (WC with 11.6% Cobalt), rolled-homogeneousarmor steel, and a titanium alloy (Ti Al6% V4%). The goal of this effort is to be able to predict a macroscopic stress-strain curve from a microscale test using spherical indentation while allowing the indenter to deviate from a perfect spherical shape. The original document contains color images.