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Posted 11/14/2016

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By Gwyn G. Neill
U.S. Army Engineer Research and Development Center, Public Affairs


Researchers in the Geotechnical and Structures Laboratory have developed a new state-of-the-art Split-Hopkinson pressure bar testing laboratory at the U.S. Army Engineer Research and Development Center in Vicksburg, Mississippi.

The effort to establish the lab was led by Dr. Robert Moser, Dr. Bill Heard and Brett Williams with the bars manufactured by Dynamic Systems and Research Corp. of Albuquerque, New Mexico. The development came about as a result of multiple researchers across the ERDC studying the behavior of materials at high strain rates including computational simulations, experimental studies of materials and development of advanced materials. The application of these studies range from blast effects to ballistic resistant materials. Previously, Split-Hopkinson pressure bar systems typically performed experiments in simple stress or one- dimensional states. For many of the materials that ERDC studies, there was a greater need so these researchers went to work.

Moser said, “We are excited about having this new in-house capability to perform fundamental measurements of material which will be useful both for experimental work as well as modeling simulation.”

This GSL project began more than two years ago, but only after working for several years on other bars located at Mississippi State University, Purdue University, University of Florida, Sandia National Laboratory and the Air Force Research Laboratory. Building the new compression and tension bar took approximately one year to complete. Currently, final instrumentation and calibration experiments to understand operational parameters are underway.

“We’ve made significant improvements with this design that makes our facility unique and one-of-a-kind. There’s no other bar capable of characterizing such large specimens under high rate triaxial compress. This stress state is critical as it more closely represents the stress state in a material when subjected to a penetration event,” Heard added.

With this new capability, GSL’s Split-Hopkinson bar benefits multiple projects and programs. The new system provides fundamental data necessary for computational simulation as well as experimentally understanding material behavior, how damage occurs and insight into developing better material.

An additional upside of the new facility is that it is more cost effective as opposed to more expensive and complex field or lab experiments. The outputs of the experiments in the ERDC facility can be used as parameters for material models in structural scale simulations which results in a tremendous cost savings.

The GSL team’s work does not stop there. By the end of 2017, another capability will be added to the system to perform high strain rate triaxial experiments. The data generated from those experiments has never been available before and is essential to understanding material behavior in complex stress states.

“We are excited about adding to the two inch diameter compression system to perform triaxial experiments,” said Moser. “GSL’s Split-Hopkinson pressure bar testing facility has already generated interest from other research and development organizations and potential customers, and we look forward to working with them,” he added.

ERDC geotechnical and structures laboratory GSL Heard Split-Hopkinson USACE