An Analysis of Parameters for the Johnson-Cook Strength ...

Army Research Laboratory

Aberdeen Proving Ground, MD 21005-5066

GRL-TR-2528

June 2001

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An Analysis of Parametersfor the

Johnson-Cook Strength Model for

2-in-Thick Rolled HomogeneousArmor

Hubert W. Meyer, Jr. and David S. Kleponis

WeaponsandMaterialsResearchDirectorate,ARL

Approved for public release;distribution is unlimited.

Abstract

Yield strengthobtainedfrom quasi-staticstrengthdatafor rolled homogeneousarmor @HA) was combinedwith dynamic strengthdata for 2-in (5lmtn) RHA to generate Johnson-Cookparametersfor 2-in RHA. Oneparameterwas fixed basedon the quasistatic strengthdata,and a least-squarems ethodwas usedto fit the others individually. The fit was tested with CTH by simulatingthe penetrationof stacks of 2.5~in-thick (63.5-mm) RHA plates(the closestavailableexperimentaldata). Parameteranalysisand comparisonof the simulationsto experimentsubstantiatedtheapproach.

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Acknowledgments

The authorswould like to acknowledgeShuhRong Chen for providing the raw data (in digital form) that was usedin thisreport.

This work was supportedin part by a grant of high-performancecomputingtime from the Departmentof DefenseHigh PerformanceComputingCenterat AberdeenProvingGround,MD.

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Table of Contents

. . . Acknowledgments .......*......*.~...*...*.*.**....~.....,..~...,~....~.....~,........~...~.....................~.~..111

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List of Figures .................*.*.*.......**................*......*.......*.......*...............*................... vii

List of Tables .......*.~I..............~**~~~~..~~~~~....*..*..*.*..~.....*...~+~I~*.~..*~......,..~......*.......*.*v..ii

2. Dynamic Data ...............~....~~...................~........*.......~.................................*...*.*.*~.*~*. 3

3.

Quasi-Static Data .*.*.*.~....*~.*....*...****...*.....~.*.~.....**~*.~.*..*..*~**.~.*.~.....~.~~......~*~~-.--4..~..

4. Fitting the Parameters .............................................................................................

5

4.1

ParameterA .........................................................................................................

5

4.2

ParametersB andn ..............................................................................................

6

4.3

Parameterc ..........................................................................................................

8

4.4

Parameterm ......................................................................................................... 10

5. Numerical Simulations ............................................................................................ 13

5.1 5.2 5.3

Setup.................................................................................................................... 13 Results.................................................................................................................. 14 Discussion............................................................................................................ 17

Distribution List .~.~..~.............,...~...~*.....**~****..***.*.*~*.*~********.~~*.*..*..........*~....*...~*.~.~..~.23 Report Documentation Page ......***.......................~~........*.**..*.~.~....................****...*** 25

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