Issue 10 Volume 41 May 16, 2003

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METALS AND METALLIC MATERIALS
Includes physical, chemical, and mechanical properties of metals and metallic materials; and metallurgy.
20030032265 Pennsylvania State Univ., University Park, PA, USA
3D Finite Element Analysis of Particle-Reinforced Aluminum
Shen, H.; Lissenden, C. J.; February 01, 2002; 6 pp.; In English; Original contains black and white illustrations
Contract(s)/Grant(s): NCC3-848; RTOP 706-85-24
Report No.(s): E-13677; No Copyright; Avail: CASI; A02, Hardcopy
Deformation in particle-reinforced aluminum has been simulated using three distinct types of finite element model: a
three-dimensional repeating unit cell, a three-dimensional multi-particle model, and two-dimensional multi-particle models.
The repeating unit cell model represents a fictitious periodic cubic array of particles. The 3D multi-particle (3D-MP) model
represents randomly placed and oriented particles. The 2D generalized plane strain multi-particle models were obtained from
planar sections through the 3D-MP model. These models were used to study the tensile macroscopic stress-strain response and
the associated stress and strain distributions in an elastoplastic matrix. The results indicate that the 2D model having a particle
area fraction equal to the particle representative volume fraction of the 3D models predicted the same macroscopic stress-strain
response as the 3D models. However, there are fluctuations in the particle area fraction in a representative volume element.
As expected, predictions from 2D models having different particle area fractions do not agree with predictions from 3D
models. More importantly, it was found that the microscopic stress and strain distributions from the 2D models do not agree
with those from the 3D-MP model. Specifically, the plastic strain distribution predicted by the 2D model is banded along lines
inclined at 45 deg from the loading axis while the 3D model prediction is not. Additionally, the triaxial stress and maximum
principal stress distributions predicted by 2D and 3D models do not agree. Thus, it appears necessary to use a multi-particle
3D model to accurately predict material responses that depend on local effects, such as strain-to-failure, fracture toughness,
and fatigue life.
Author
Aluminum Alloys; Finite Element Method; Strain Distribution; Triaxial Stresses; Stress-Strain Relationships; Tensile Stress;
Computerized Simulation; Elastic Deformation
20030032927 NASA Glenn Research Center, Cleveland, OH, USA
Specific Hardening Function Definition and Characterization of a Multimechanism Generalized Potential-Based
Viscoelastoplasticity Model
Arnold, S. M.; Saleeb, A. F.; February 2003; 38 pp.; In English; Original contains black and white illustrations
Contract(s)/Grant(s): NCC3-808; 22-713-82-35
Report No.(s): NASA/TM-2003-212219; NAS 1.15:212219; E-13833; No Copyright; Avail: CASI; A03, Hardcopy
Given the previous complete-potential structure framework together with the notion of strain- and stress-partitioning in
terms of separate contributions of several submechanisms (viscoelastic and viscoplastic) to the thermodynamic functions
(stored energy and dissipation) a detailed viscoelastoplastic multimechanism characterization of a specific hardening
functional form of the model is presented and discussed. TIMETAL 21S is the material of choice as a comprehensive test
matrix, including creep, relaxation, constant strain-rate tension tests, etc. are available at various temperatures. Discussion of
these correlations tests, together with comparisons to several other experimental results, are given to assess the performance
and predictive capabilities of the present model particularly with regard to the notion of hardening saturation as well as the
interaction of multiplicity of dissipative (reversible/irreversible) mechanisms.
Author
Elastoplasticity; Viscoelasticity; Viscoplasticity; Hardening (Materials); Models; Thermodynamics; Titanium Alloys
20030033070 NASA Goddard Space Flight Center, Greenbelt, MD, USA
The FERRUM Project: Experimental Transition Probabilities of [Fe II] and Astrophysical Applications
Hartman, H.; Derkatch, A.; Donnelly, M. P.; Gull, T.; Hibbert, A.; Johannsson, S.; Lundberg, H.; Mannervik, S.; Norlin, L.
-O.; Rostohar, D.; November 16, 2002; 8 pp.; In English
Contract(s)/Grant(s): GR/L20276; HST-7302; Copyright; Avail: CASI; A02, Hardcopy
We report on experimental transition probabilities for thirteen forbidden [Fe II] lines originating from three different
metastable Fe II levels. Radiative lifetimes have been measured of two metastable states by applying a laser probing technique
on a stored ion beam. Branching ratios for the radiative decay channels, i.e. M1 and E2 transitions, are derived from observed
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