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Research Papers: Materials and Fabrication

# Dynamic Strength Estimates for a High-Strength Experimental Steel

[+] Author and Article Information
K. L. Torres

Department of Aerospace Engineering and Mechanics, University of Alabama, Tuscaloosa, AL 35487torre003@ua.edu

H. A. Clements

Department of Aerospace Engineering and Mechanics, University of Alabama, Tuscaloosa, AL 35487cleme014@ua.edu

S. E. Jones

Department of Aerospace Engineering and Mechanics, University of Alabama, Tuscaloosa, AL 35487sejones@eng.ua.edu

M. Dilmore, B. Martin

Munitions Directorate, Air Force Research Laboratory, Eglin AFB, FL 32542

J. Pressure Vessel Technol 131(2), 021404 (Dec 11, 2008) (6 pages) doi:10.1115/1.3027453 History: Received June 28, 2006; Revised November 07, 2007; Published December 11, 2008

## Abstract

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles to defeat hard targets, such as concrete, sand, and soil. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the travel distance in the target is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental high-strength steel, also called Eglin steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain rate can be assessed through a strain rate of roughly $105∕s$. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.

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## Figures

Figure 1

A series of post-test 164-caliber (4.17mm) specimens. The velocities ranged from 200m∕sto173m∕s, left to right.

Figure 2

Illustration of an undeformed and a deformed specimen and geometry nomenclature

Figure 3

The BETA LaserMike, which is the laser micrometer used in the laboratory to find the diameter and longitudinal position of any cross section in a Taylor specimen to an accuracy of 0.00001in. (0.00025 mm). The fixture between the laser beams in the figure was designed and fabricated by Mr. Marcus Taylor, a precision machinist. The device is unique and used specifically to reduce data from very small scale Taylor cylinders.

Figure 4

The normalized undeformed section length versus the normalized deformed length of the 164-caliber (4.17mm) specimens. This is the graph where the slope and intercept are obtained.

Figure 5

The normalized undeformed section length versus the normalized deformed length of the 215-caliber (5.46mm) specimens. This is the graph where the slope and the intercept are obtained.

Figure 6

A graphical representation of the estimated quasistatic stress versus strain for the 164-caliber (4.17mm) and 215-caliber (5.46mm) specimens. This graph displays the average quasistatic stress estimate at each compressive strain.

Figure 7

Quasistatic stress estimates for the 164-caliber (4.17mm) specimens at various impact velocities

Figure 8

Quasistatic stress estimates for the 215-caliber (5.46mm) specimens at several impact velocities

Figure 9

Dynamic stress estimates for the 164-caliber (4.17mm) and 215-caliber (5.46mm) specimens

Figure 10

Dynamic stress estimates for a 164-caliber (4.17mm) specimen at 185m∕s

Figure 11

Dynamic stress estimates for a 215-caliber (5.46mm) specimen at 177m∕s.

Figure 12

True dynamic stress versus true strain at constant strain rates of 103∕s and 104∕s for a 164-caliber (4.17mm) specimen at 185m∕s

Figure 13

True dynamic stress versus true strain at constant strain rates of 103∕s and 104∕s for a 215-caliber (5.46mm) specimen at 177m∕s

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