Constitutive model of metal matrix composites at high strain rates and its application

The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s−1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the “strength margin” approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1–3·103·s−1 using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s−1, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s−1; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s−1. The deformation mechanism of MMCs was evaluated.

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EFFECTS OF TANGENT OPERATORS ON PREDICTION ACCURACY OF MESO-MECHANICAL CONSTITUTIVE MODEL OF ELASTO-PLASTIC COMPOSITES

International Journal of Computational Methods ◽

10.1142/s0219876213500643 ◽

2014 ◽

Vol 11 (04) ◽

pp. 1350064

Author(s):

S. J. GUO ◽

G. Z. KANG ◽

J. ZHANG ◽

Q. H. KAN

Keyword(s):

Constitutive Model ◽

Error Analysis ◽

Metal Matrix Composites ◽

Metal Matrix ◽

Prediction Accuracy ◽

Strain Difference ◽

Accurate Prediction ◽

Matrix Composites ◽

Load Increment ◽

Plastic Composites

With a newly developed homogenization cyclic constitutive model of particle reinforced metal matrix composites [Guo et al. (2011)], the effects of tangent operators, i.e., continuum and algorithmic tangent operators [defined by Doghri and Ouaar (2003)] on the accuracy of the developed meso-mechanical constitutive model to predict the monotonic tensile and uniaxial ratchetting deformations of SiC P /6061 Al composites were investigated in this work. The predictions were obtained by the developed model with the choices of different tangent operators and various magnitudes of load increments. Comparison of prediction accuracy and necessary error analysis on the results obtained by different tangent operators were conducted. It is shown that: the stress or strain difference in each load increment and produced by using different tangent operators will accumulate step by step; accurate prediction should be obtained by employing a load increment small enough, especially when the algorithmic tangent operator is used in predicting the uniaxial ratchetting of the composites.

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