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Research Papers

Dynamic Localizations in HSLA-65 and DH-36 Structural Steel at Elevated Temperatures

[+] Author and Article Information
Farid H. Abed

e-mail: fabed@aus.edu

Fadi Makarem

Department of Civil Engineering,
American University of Sharjah,
Sharjah 26666, United Arab Emirates

George Z. Voyiadjis

Department of Civil and Environmental
Engineering,
Louisiana State University,
Baton Rouge, LA 70803

Contributed by the Materials Division of ASME for publication in the Journal of Engineering Materials and Technology. Manuscript received June 1, 2012; final manuscript received October 3, 2012; published online March 25, 2013. Assoc. Editor: Xi Chen.

J. Eng. Mater. Technol 135(2), 021007 (Mar 25, 2013) (11 pages) Paper No: MATS-12-1123; doi: 10.1115/1.4023775 History: Received June 01, 2012; Revised October 03, 2012

This study addresses the problem of dynamic strain localization in two steel alloys; HSLA-65 and DH-36 at elevated temperatures. It aims at understanding the adiabatic deformation of high strength structural steel by performing a nonlinear finite element (FE) analysis. A microstructural-based viscoplasticity model is integrated and implemented into the commercial FE code ABAQUS/Explicit via the user material subroutine coded as VUMAT. Numerical implementation for a simple compression problem meshed with one element is used for testing the efficiency of the proposed model implementation. The numerical results of the isothermal and adiabatic true stress-true strain curves compare very well with the experimental data for the two steel alloys over a wide range of temperatures and strain rates. The effectiveness of the present approach enables the study of strain localizations in a cylindrical hat-shaped specimen with certain dimensions, where the location of shear localization preceding shear band formation is forced to be between the hat and the brim. The FE simulations of the material instability problems converge to meaningful results upon further refinement of the FE mesh. Material length scales are implicitly introduced into the governing equations through material rate-dependency (viscosity). A sensitivity analysis is also performed on the physically-based viscoplasticity model parameters in order to study their effect on dynamic localizations. Several conclusions related to the width and intensity of the shear localization, considering various velocities and temperatures, are discussed.

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Figures

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Fig. 1

Axisymmetric simple uniaxial compression modeled in ABAQUS, V = 30 m/s and T0 = 400 K: (a) undeformed shape, and (b) deformed shape at the end of a time step = 200 μs

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Fig. 2

Comparisons of the true stress-true strain between the experimental and FE results for HSLA-65 at different initial temperatures and two strain rates of (a) 0.001 s−1, and (b) 0.1 s−1

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Fig. 3

Comparisons of the adiabatic true stress-true strain between the experimental and FE results for HSLA-65 at several initial temperatures and a strain rate of (a) 3000 s−1, and (b) 8500 s−1

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Fig. 4

Comparisons of the true stress-true strain between the experimental and FE results for DH-36 at different initial temperatures and two strain rates of (a) 0.001 s−1, and (b) 0.1 s−1

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Fig. 5

Comparisons of the true stress-true strain between the experimental and FE results for DH-36 at different initial temperatures and two strain rates of (a) 3000 s−1, and (b) 8500 s−1

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Fig. 6

(a) Geometric description of the cylindrical hat-shaped specimen, and (b) the FE model for a quarter portion of the hat-shaped specimen using axisymmetric mesh elements

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Fig. 7

(a) Mesh refinements in the shear zone, and (b) path 1 through the shear zone of the hat-shaped specimen

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Fig. 8

(a) Shear stress versus axial displacement, and (b) distribution of the equivalent plastic strain across path 1, for HSLA-65 for three different mesh configurations

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Fig. 9

Contour plot of the equivalent plastic strain at V = 25 m/s and T0 = 296 K

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Fig. 10

Contours of the equivalent plastic strain for HSLA-65 steel at the end of the 0.2 mm axial displacement under a velocity of V = 25 m/s and different initial temperatures

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Fig. 11

Contours of the equivalent plastic strain for DH-36 steel at the end of the 0.2 mm axial displacement under a velocity of V = 25 m/s and different initial temperatures

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Fig. 12

Equivalent plastic strain along path-1 at V = 25 m/s and different temperatures for (a) HSLA-65, and (b) DH-36

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Fig. 13

Equivalent plastic strain along path-1 at initial temperature T = 77 K and different velocities for (a) HSLA-65, and (b) DH-36

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Fig. 14

Equivalent plastic strains for HSLA-65 steel at 0.2 mm axial displacement for different values of (a) c2, (b) c3, (c) c4, and (d) c5

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Fig. 15

Equivalent plastic strains for HSLA-65 steel at 0.2 mm axial displacement for different values of (a) c2, (b) c3, (c) c4, and (d) c5

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