Mechanical Performance –

Extreme Conditions

METALS

This project provides property data, metrology, and standard 

test methods for materials systems under extreme conditions 

for areas critical to US manufacturing, homeland security, 

and energy infrastructure. Machining research, soft body 

armor standards and building safety highlight our current 

materials focus areas of lead alloys, as well as steels for 

fire-resistant construction and pipelines.

Objective

Impact and Customers

• Advanced modeling and optimization tools supported by NIST research 

efforts are aimed at helping maintain the global competitiveness of the $200 

billion US machining industry.

• The NIST Office of Law Enforcement Standards currently sponsors our 

investigation of the deformation behavior of civilian ammunition threatening 

officers on the street.

• In a three year collaborative effort with steel producers and consumers under 

the sponsorship of an ASTM International task group, we have recommended 

a method for evaluating the performance of new grades of structural steel in 

conditions relevant to building fires.

Approach

Materials Science and Engineering Laboratory

Optimizing high-speed machining processes through powerful finite element modeling techniques is an important 

pathway to American manufacturing competitiveness in an increasingly competitive global marketplace. 

Quantitatively accurate simulations of machining rely on robust constitutive models of workpiece materials under real 

machining conditions. To this end, the Metallurgy Division has worked 

with the Manufacturing Engineering Laboratory to develop measurement 

methods for the deformation behavior of steels at high strain rate during 

extremely high heating rates using a unique, electrically pulse-heated 

Kolsky bar.

Next-generation soft body armor standards for law enforcement need 

to provide for performance against various classes of ballistic threats 

facing officers in the field. Crucial to this effort is better understanding 

how a bullet’s materials and design influence its ability to penetrate soft 

body armor. Our state-of-the-art high-speed Digital Image Correlation 

(DIC) measurement tool allows us to study the deformation behavior of 

whole bullets under highly controlled simulated impacts using the Kolsky 

bar.

855-12-22b
Materials Science and Engineering Laboratory

In 2008 we integrated a new, customized 

high-speed digital image correlation (DIC) 

measurement instrument into the Kolsky bar 

facility. This new instrument provides fullfield displacement data on rapidly deforming 

specimens at a rate of up to 180 kHz. Timeresolved stereoscopic image pairs are acquired 

using a pair of ultra-high speed digital cameras 

and analyzed for shape and deformation 

information using the image correlation 

technique. With this instrument, high strain 

rate mechanical testing is advanced beyond 

the traditional limitations of uniform, uni-axial 

strain experimentation. 

Using this instrument, non-cylindrical and nonhomogeneous specimens, such as copperjacketed bullets, can be rapidly strained in 

a Kolsky bar test while the deformation field 

is measured in real time. Coupled with finite 

element simulations, these new measurements 

produce an unprecedented insight into the 

constitutive behavior of materials and structures 

under extreme, yet well controlled, loading 

conditions. Constitutive models of bullet lead 

and jacket materials developed in-house are 

being evaluated, as well as those found in the 

literature, to determine their suitability for highfidelity models of bullet impact on soft body 

armor being developed elsewhere. 

We are also applying high speed DIC 

measurements to the dynamic testing of very 

soft tissue-simulant materials, where acceptable 

test conditions are difficult or impossible to 

achieve using traditional methods. By applying 

the DIC instrument, the deformation field during 

specimen “ringup” can now be measured. 

These measurements, along with finite element 

analyses, provide useful data to describe the 

dynamic constitutive response of the material 

under non-equilibrium test conditions that 

were previously impossible to evaluate. 

Further applications for the DIC instrument will 

include strain localization studies on rapidly 

deformed tensile specimens and an improved 

assessment of measurement uncertainties for 

high temperature pulse-heated tests using the 

traditional cylindrical specimens.

Also in 2008, progress continued on measuring 

the high-temperature, high-strain-rate behavior 

of engineering alloys of interest to the machining 

industry. New materials tested this year included 

AISI 4140 steel, Ti-6AI-4V alloy and brass, 

which we added to extensive data on AISI 1045 

and AISI 1075 steel, high-purity iron, and 

several tungsten, iron and aluminum alloys. 

Our particular focus is on measuring the effect 

of thermally induced phase transformations 

on plastic flow stress at high strain rates, and 

investigating the associated kinetics of these 

transformations.

We have worked through an ASTM-International 

task group to help develop standards for 

evaluating the performance of new grades 

of fire-resistive (FR) construction steels. These 

steels, intended as drop-in replacements for 

existing grades of construction steel, provide 

enhanced high-temperature deformation 

resistance. Their improved retained strength at 

high temperatures could allow extra time for 

occupants to exit buildings.

That task group recently completed its work and 

recommended a definition for fire-resistive steels 

based on retained yield strength at elevated 

temperature. The responsibility for developing a 

standard has passed from the testing committee 

(28) to the steel committee (A01).

The figure below shows that fire-resistive steels 

(SN490B-FR, FR-1, and FR-2), simultaneously 

improve temperature- and retained-strength 

performance compared to two ordinary 

structural steels (A992 and A572). The hashed 

boxes represent the commonly accepted 

performance of ordinary structural steel (1/2 of 

the room-temperature strength at 538 °C) and 

the new definition for fire-resistive steel (2/3 of 

the room-temperature strength at 600 °C).

Accomplishments

William Luecke 

J. David McColskey

 

Steven Mates

(Metallurgy Division)

(301) 975-8114

steven.mates@nist.gov

www.nist.gov/metallurgy

Learn More Publications

Mates SP and Rhorer RL High Strain Rate Tissue Simulant Measurements Using Digital 

Image Correlation SEM Annual Conference, June 1-4, 2009, Albuquerque, NM, USA

Mates SP, Rhorer RL, Whitenton E, Burns T and Basak D A Pulse-Heated Kolsky Bar 

Technique for Measuring Flow Stress of Metals Subjected to High Loading and Heating 

Rates Exp. Mech., 48: 799 (2008)

Mates SP, Rhorer RL, Banovic S, Whitenton E and Fields R Tensile Strength Measurements 

of Frangible Bullets Using the Diametral Compression Test Int. J. Impact Eng., 35 (6): 

511 (2008)

Banovic SW, Foecke T, Luecke WE, McColskey JD, McCowan CN, Siewert TA and 

Gayle FW The Role of Metallurgy in the NIST Investigation of the World Trade Center 

Towers Collapse JOM, 59 (11): 22 (2007)