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Title: The elastic precursor behavior of tantalum under dynamic loading, its implications and modeling.

Abstract

When elastic-plastic materials, such as metals, are subjected to moderately high strain rates or dynamic loadings, the plastic stress wave trails behind the elastic wave because of its slower wave speed. Due to the inherent time-dependent nature of the plastic deformation, the elastic precursor generally loads the material to a metastable elastic state at a stres level that is higher than the static strength of the material. This metastable state gradually relaxes to the equilibrium state and the relaxation results in the so-called precursor decay. In a recent work by Asay et al. (J. Appl. Phys., 2009), the inelastic response of annealed and cold-rolled pure polycrystalline tantalum at intermediate strain rates ({approx} 106/sec) was experimentally characterized with ramp wave loading. It was found that the precursor of the annealed tantalum showed little decay over a propagation distance of 6 mm even though the peak precursor stress was well above the static strength of the mateiral. The precursor for the cold-rolled sample was more dispersive and did not exhibit the characteristics depicted by the annealed samples. In this study, a constitutive model based on the concept of dislocation motion and generation was developed to gain insights into this somewhat unusual precursormore » behavior, particularly for the annealed samples, and the possible underlying deformation mechanisms for tantalum. Despite its simplicity, the model worked quite well for both the annealed and cold-rolled materials. The tantalum studied here essentially exhibits strong rate sensitivity and this behavior is modeled through the low dislocation density and the strong stress dependence of the dislocation velocity. Both of these contributions may be related to the low mobility of the screw dislocations in bcc metals. This low mobility may result from its extended, three-dimensional core structure.« less

Authors:
 [1]
  1. Washington State University
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
989996
Report Number(s):
SAND2010-1769C
TRN: US201020%%82
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the Wash. State Univ. MME symposium series, Spring 2010 held April 8, 2010 in Pullman, WA.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DECAY; DEFORMATION; DISLOCATIONS; METASTABLE STATES; PLASTICS; PRECURSOR; RELAXATION; SCREW DISLOCATIONS; SENSITIVITY; SIMULATION; STRAIN RATE; TANTALUM; VELOCITY

Citation Formats

Ding, Jow-Lian. The elastic precursor behavior of tantalum under dynamic loading, its implications and modeling.. United States: N. p., 2010. Web.
Ding, Jow-Lian. The elastic precursor behavior of tantalum under dynamic loading, its implications and modeling.. United States.
Ding, Jow-Lian. Mon . "The elastic precursor behavior of tantalum under dynamic loading, its implications and modeling.". United States.
@article{osti_989996,
title = {The elastic precursor behavior of tantalum under dynamic loading, its implications and modeling.},
author = {Ding, Jow-Lian},
abstractNote = {When elastic-plastic materials, such as metals, are subjected to moderately high strain rates or dynamic loadings, the plastic stress wave trails behind the elastic wave because of its slower wave speed. Due to the inherent time-dependent nature of the plastic deformation, the elastic precursor generally loads the material to a metastable elastic state at a stres level that is higher than the static strength of the material. This metastable state gradually relaxes to the equilibrium state and the relaxation results in the so-called precursor decay. In a recent work by Asay et al. (J. Appl. Phys., 2009), the inelastic response of annealed and cold-rolled pure polycrystalline tantalum at intermediate strain rates ({approx} 106/sec) was experimentally characterized with ramp wave loading. It was found that the precursor of the annealed tantalum showed little decay over a propagation distance of 6 mm even though the peak precursor stress was well above the static strength of the mateiral. The precursor for the cold-rolled sample was more dispersive and did not exhibit the characteristics depicted by the annealed samples. In this study, a constitutive model based on the concept of dislocation motion and generation was developed to gain insights into this somewhat unusual precursor behavior, particularly for the annealed samples, and the possible underlying deformation mechanisms for tantalum. Despite its simplicity, the model worked quite well for both the annealed and cold-rolled materials. The tantalum studied here essentially exhibits strong rate sensitivity and this behavior is modeled through the low dislocation density and the strong stress dependence of the dislocation velocity. Both of these contributions may be related to the low mobility of the screw dislocations in bcc metals. This low mobility may result from its extended, three-dimensional core structure.},
doi = {},
url = {https://www.osti.gov/biblio/989996}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {3}
}

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