Shinji Tanimura

Superplastic behavior in a mechanically alloyed aluminum composite reinforced with SiC particulates

The discovery of very-high-strain-rate superplasticity in a mechanically alloyed 15 vol pct SiCp/IN9021 aluminum composite is reported. Tensile elongations of more than 500 pct were obtained at strain rates between 5 to 100/s at 823 K. The maximum elongation of 610 pct was recorded at 6/s and 823 K. The potential for high-strain-rate superplasticity in this mechanically alloyed composite is found to be superior to a number of other reinforced aluminum composites. In particular, the superplastic strain rates were many orders of magnitude higher than those for typical superplastic alloys. It is demonstrated that mechanically alloyed composites can exhibit superplasticity in the very high strain rate over 1/s. 13 refs.

Superplasticity in as-extruded Si3N4w6061 aluminum composites processed at a ratio of 100: 1

Abstract 6061 aluminum matrix composites reinforced with 20 vol% Si 3 N 4 whiskers have been extruded at 773 K with a reduction ratio of 100: 1, and their properties have been investigated at an elevated temperature of 818 K. A large elongation of 600% was obtained at an initial strain rate of 2 × 10 −1 s −1 .

Superplastic behavior in as-extruded Al-Cu-Mg alloy matrix composite reinforced with 20 vol% Si3N4 particulates

High strain rate superplasticity has been found in a new 20 vol pct Si3N4p/Al-Cu-Mg composite. The composite developed to be a finite-grained structure 3 micron in size with a very uniform distribution of Si3N4 particulates of less than 1 micron in size, fabricated by hot extrusion at 733 K with a reduction ratio of 100:1. The maximum elongation of 830 percent, which has not been previously recorded for any finite-grained superplastic composites, was recorded at 788 K at a relatively high strain rate of 0.04/s at which a relatively high m value of about 0.3 was obtained. 12 refs.

Superplastic-like behavior in as-extruded AlZnMg alloy matrix composites reinforced with Si3N4 whiskers

Abstract For as-extruded Alue5f8Znue5f8Mg alloy without reinforcement of Si 3 N 4ω , a maximum elongation is 140%, which was measured near a relatively high strain rate 2 × 10 −2 s −1 at 818 K. On the other hand, a maximum elongation of 160% for α-Si 3 N 4ω /Alue5f8Znue5f8Mg composites, whose grain size was less than 4 μm, was obtained at 798 K and at the highest end in strain rate range of 8 × 10 −1 s −1 evaluated in this work, and for β-Si 3 N 4ω /Alue5f8Znue5f8Mg composites with grain size of about 4 μm, a maximum elongation of 230% was obtained at 818 K and a high strain rate of 2 × 10 −1 s −1 . In these Alue5f8Znue5f8Mg system alloys the composites reinforced with α-Si 3 N 4ω exhibited a high superplastic elongation at higher strain rates than the composites reinforced with β-Si 3 N 4ω .

Superplastic-like behavior in AlMgSi composites reinforced with α-Si3N4 or β-Si3N4 whiskers

Abstract Superplastic-like behavior has been investigated for Alue5f8Mgue5f8Si alloy matrix composites reinforced with either α-Si3N4 or β-Si3N4 whiskers. Both composites exhibited large elongations in the high strain rate range near 10−1 s−1. The superplastic potential of the composite reinforced with β-Si3N4 whiskers was superior to that of the composite reinforced with α-Si3N4 whiskers.

Superplastic properties in a Si3N4w/Al-Zn-Mg composite extruded at a reduction ratio of 100:1

Abstract Al-Zn-Mg system alloy matrix composite reinforced with 20 vol% Si3N4 whiskers has been extruded at 773 K with a reduction ratio of 100:1, and its superplastic properties have been investigated at an elevated temperature by a constant velocity tension test. A maximum elongation of 240% was obtained at 5 × 10−1 s−1.

A Constitutive Equation Describing Strain Hardening, Strain Rate Sensitivity, Temperature Dependence and Strain Rate History Effect

A constitutive equation with which strain hardening, strain rate sensitivity, temperature dependence and strain rate history effect can be described covering a wide range of strain rates is proposed. To describe the strain hardening and the strain rate history effect, a new idea which takes into account the plastic work in a manner of fading memory is introduced. It is illustrated that material behaviors observed not only in constant strain rate tests but also in jump tests can be represented fairly well by the proposed equation.

Generated Force and Deformation at a Conical End of Soft Magnetic Iron Bars due to Impact.

In designing machine parts or structures which should withstand an impact load, it is fundamentally important to know the dynamic deformation of the materials at its contact part and the impulsive force generated at that part. The deformed shape at the contact part and the generated impulsive force have been measured when a Soft Magnetic Iron bar collides axially, perpendicularly against a devised sensing plate. It was found that a new truncated cone was formed at the contact end and that the conical angle of the cone depended only on the conical angle of the former cone before the collision. It was also confirmed that the generated mean stress on the boundary plane between the deformed part and the undeformed part at the impact end was constant. By comparing experimental results with calculated results using the theoretical relation proposed in previous paper, the effectiveness of the theoretical relation for estimating the impulsive force for Soft Magnetic Iron Bars is confirmed.

Thermal stress analysis of a semi-infinite solid cylinder under consideration of phase transformation. Approximation by means of stephan problem.

As one of analytical problems of thermal stresses with a moving boundary, we analyzed thermal deformations and thermal stresses caused by a phase transformation. We assumed that a cooled end surface of a semi-infinite solid cylinder, which is kept at a constant temperature, yields the phase transformation with respect to the axial direction; then as a result, the solid cylinder could be seprated into two dissimilar solid phases with thermally and thermoelastically different material properties by a moving interface. In the analytical developments, we adopted Neumanns solution for one-dimensional temperature distribution, and then we analyzed the axisymmetric thermoelastic field with aid of the thermoelastic displacement potential function and Loves displacement function. As an illustration, numerical calculations are carried out for Martensite Transformation, and the influence of the latent heat on the temperature and thermoelastic fields were examined precisely.

Stress wave propagation in the ground containing a spherical cavity.

The governing equations of the dynamic problems in elastic-viscoplastic three-dimensional soil containing spherical cavities are formulated by means of bipolar coordinates adapting constitutive equations of normally consolidated clay. The stress wave propagation in the ground containing a spherical cavity of 0.5 m diameter at 5 m depth from the ground surface is analyzed by the method of direct integration of the basic equations of the problem, when an axisymmetric dynamic load is applied to the boundary of the cavity. In the calculation, the change of pressure with the depth from the ground surface is also taken into account for the initial state of the soil.