Support has been provided by the U.S. National Institute of Standards and Technology (NIST). The author is grateful to Dr. Carol Handwerker of NIST for support and review of this work as well as to Mr. Kil-Won Moon of NIST who digitized most of the raw data. The author also thanks Dr. Alek Zubelewicz of Motorola for insightful discussions on the data and on the topic of constitutive modeling.