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Title: An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials

Abstract

A model utilizing a simple force-equilibrium approach was developed to establish the effect of the cavity nucleation rate and cavity coalescence on the uniaxial tensile behavior of superplastic metals. All cavities were assumed to be spherical and uniformly distributed within the material, irrespective of the degree of deformation. Material input parameters for the model comprised the cavity nucleation rate (N), the strain-rate sensitivity of the flow stress (m), and the growth parameter for individual cavities ({eta}), which was taken to be a function of m. The effect of cavity coalescence on average void size and volume fraction was treated using an empirical relation, which correlates an average void growth rate to the growth rate of individual, noninteracting cavities. Model predictions indicated that the macroscopic quantities often used to describe cavitation behavior, i.e., initial cavity volume fraction (C{sub v0}) and apparent cavity growth rate ({eta}{sub APP}) describe the combined influence of cavity nucleation, growth, and coalescence. With regard to the overall tensile behavior, simulation results revealed that increasing cavity nucleation rates reduce ductility in a manner analogous to the effect of decreases in the strain-rate sensitivity. In addition, the failure mode was established with regard to the relative magnitudes of themore » cavity nucleation rate and the strain-rate sensitivity. Model predictions of tensile elongation and cavity-size distributions were validated by comparison to measurements found in the literature for cavitating superplastic materials.« less

Authors:
; ;
Publication Date:
Research Org.:
UES Inc., Dayton, OH (US)
OSTI Identifier:
20075684
Alternate Identifier(s):
OSTI ID: 20075684
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 31; Journal Issue: 5; Other Information: PBD: May 2000; Journal ID: ISSN 1073-5623
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MICROSTRUCTURE; TENSILE PROPERTIES; METALS; PLASTICITY; MATHEMATICAL MODELS; POROSITY; NUCLEATION; STRAIN RATE; FLOW STRESS; VALIDATION

Citation Formats

Nicolaou, P.D., Semiatin, S.L., and Ghosh, A.K. An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials. United States: N. p., 2000. Web. doi:10.1007/s11661-000-0260-6.
Nicolaou, P.D., Semiatin, S.L., & Ghosh, A.K. An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials. United States. doi:10.1007/s11661-000-0260-6.
Nicolaou, P.D., Semiatin, S.L., and Ghosh, A.K. Mon . "An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials". United States. doi:10.1007/s11661-000-0260-6.
@article{osti_20075684,
title = {An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials},
author = {Nicolaou, P.D. and Semiatin, S.L. and Ghosh, A.K.},
abstractNote = {A model utilizing a simple force-equilibrium approach was developed to establish the effect of the cavity nucleation rate and cavity coalescence on the uniaxial tensile behavior of superplastic metals. All cavities were assumed to be spherical and uniformly distributed within the material, irrespective of the degree of deformation. Material input parameters for the model comprised the cavity nucleation rate (N), the strain-rate sensitivity of the flow stress (m), and the growth parameter for individual cavities ({eta}), which was taken to be a function of m. The effect of cavity coalescence on average void size and volume fraction was treated using an empirical relation, which correlates an average void growth rate to the growth rate of individual, noninteracting cavities. Model predictions indicated that the macroscopic quantities often used to describe cavitation behavior, i.e., initial cavity volume fraction (C{sub v0}) and apparent cavity growth rate ({eta}{sub APP}) describe the combined influence of cavity nucleation, growth, and coalescence. With regard to the overall tensile behavior, simulation results revealed that increasing cavity nucleation rates reduce ductility in a manner analogous to the effect of decreases in the strain-rate sensitivity. In addition, the failure mode was established with regard to the relative magnitudes of the cavity nucleation rate and the strain-rate sensitivity. Model predictions of tensile elongation and cavity-size distributions were validated by comparison to measurements found in the literature for cavitating superplastic materials.},
doi = {10.1007/s11661-000-0260-6},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
issn = {1073-5623},
number = 5,
volume = 31,
place = {United States},
year = {2000},
month = {5}
}