Strain rate dependent compression mechanical behavior of an SiC-particulate reinforced Al (2024-O) metal matrix composite (MMC) with different particle volume fractions was numerically investigated at various strain rates. Calculations were performed using axisymmetric finite element unit cell model, in which an elastic SiC particle was embedded inside a strain rate sensitive viscoplastic Al matrix. Stress-strain curves of Al matrix material were derived from Split Hopkinson Pressure Bar experiments at various strain rates and used as inputs in the FEM model. Numerically computed stress-strain curves and strain rate sensitivity were compared with those of experiments for a 15% SiC-particulate reinforced MMC. Computed strain rate sensitivity of the MMC was found to be higher than that of the matrix alloy and increased with increasing strain contrary to the strain independent matrix strain rate sensitivity. The strain rate sensitivity of the MMC was also found to increase with increasing particle volume fraction at the same particle size. Finally, several possible reasons including assumptions used in the model, adiabatic heating, microstructural variations between the composite matrix and matrix alloy, particle shape and distribution and damage accumulation for the small discrepancy found between computed and experimental stress-strain curves and strain rate sensitivity of the composite were discussed.

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Quantitative prediction of environmentally assisted cracking such as stress corrosion cracking is one of the greatest concerns in lifetime management and consequent lifetime extension of light water reactors. Continuum mechanics has been applied to quantify the effect of crack tip mechanics on crack tip film degradation and its physical interaction with the oxidation kinetics. Besides such an effect, it has been realized that crack tip stress/strain can significantly affect the oxidation kinetics by a physical-chemical mode. The present paper focuses on optimizing crack tip asymptotic fields, oxidation kinetics laws, and their interaction modes for modeling stress corrosion cracking growth rates. Meanwhile, the physical-chemical effect of stress/strain on solid state oxidation kinetics at the stress corrosion crack tip is emphasized. The criteria for formulating stress corrosion cracking and optimizing input parameters are also discussed.

Roller die drawing is required for manufacturing low-formability materials such as high-carbon steels into fine wires with a diameter of 500 μm or less because of its characteristic lower friction than conventional die drawing. However, tilting, which is the inclination of the wire under the roll bite, often occurs in fine wires, which degrades their dimensional accuracy. Excessive tilting may generate wrinkling and overfill of the wire; thus, the design of the drawing setup of roller dies for reducing tilting is important from an industrial viewpoint. With the aim of designing a new setup for roller die drawing that can eliminate tilting; we carried out systematic experimental and analytical investigations. We first experimentally focused on the distance between adjacent rollers, and then theoretically focused on the area reduction ratio and roll-to-wire diameter ratio using the finite element method (FEM), taking the twisting moment as a representative parameter to evaluate the effect of different manufacturing conditions. It was found experimentally that there is a maximum threshold distance between adjacent rollers for preventing tilting. To draw a 200-μm-diameter wire without tilting, the roller distance should be set at no more than 8 mm, which leads to a more compact setup than the conventional one. Theoretical analysis revealed that a smaller area reduction ratio and a smaller roll-to-wire diameter ratio are required to reduce the tilting of the wire in roller die drawing.