Ceramic-particle-reinforced aluminum composites exhibit excellent mechanical, physical and thermal properties which makes them very attractive for various applications such as in automobile engineering components and aerospace structures. A superplastic aluminum sheet clad with ceramic-particle-reinforced aluminum composites was developed to increase the advantages of such composites. A clad sheet was fabricated by the hot rolling of an aluminum alloy sheet and a TiN-particle-reinforced aluminum composite sheet, which were fabricated by powder metallurgy and thermomechanical processing. The thickness ratio of the composite in the clad sheet was 50%. Clad sheets indicated an m value of about 0.36 and a total elongation of 257% at a strain rate of 8.3×10-3s-1 and a temperature of 793K. Aluminum alloys indicated a total elongation of 567% under the same conditions, whereas TiN/Aluminum composites indicated a total elongation of 65%. Under the pressure of a gas flow for 3 min on its surface, the clad sheet also formed a bulge like a hemisphere, regardless of whether the aluminum sheet surface or MMC sheet surface was pressurized.
A clad sheet showing superplasticity was fabricated by joining a TiN-particle-reinforced aluminum composite sheet and an aluminum alloy sheet through hot rolling. The relationships between the thickness ratio of the composite in the clad sheet and the superplastic characteristics of the clad sheet were studied, and the deformation mechanism was discussed. Total elongation and flow stress during superplastic deformation were related to the thickness ratio of a composite in the clad sheet. At a strain rate of 8.3×10-3s-1 and a temperature of 793 K, total elongation decreased as the thickness ratio of a composite in the clad sheet increased. The superplastic performance of a three layered alloy with two composites was also related to the thickness ratio of the composites. Flow stress during superplasic deformation in the clad sheet was affected by a sheet which had a higher strain rate sensitivity than the other sheet, as analyzed by FEM simulations. Thus, it can be concluded that the superplastic characteristics of composites can be enhanced by joining alloys with a high strain rate sensitivity.
In this paper, we report on the dynamic cutting resistance of coated paperboard and the impact force on a blade tip during the pushing shear process. The cutting force on a blade was measured using a strain gauge by varying the rotation velocity NC of the crankshaft that controls the vertical motion of the blade. The transient cutting force of the blade was investigated in terms of the maximum cutting resistance ƒCmax, and the dynamic peak force ƒDmax after breaking down. As a result of the experiment, the impact factor υm=ƒDmax/ƒCmax of the cutting force was shown to be a function of NC, and the velocity dependency of the cutting resistance was found at the pushing stage. Furthermore, the release of the compressive elastic energy of the paperboard during the breakdown was discussed in relation to the variance of the dynamic cutting force.
In order to improve the mechanical properties of magnesium alloys, silicon-carbide dispersion-strengthened magnesium (SiCp/ Mg), in which SiC particles (SiCp) were milled with pure Mg by an attritor ball mill and used as reinforcement, was produced by hot pressing. Silicon-carbide dispersion strengthening by the mechanical alloying (MA) method in magnesium was investigated. The experimental results are summarized as follows. By raising the milling force of the ball mill in which the pAl2O3/ Mg MA powder of the previous report was made, the density of SiCp/ Mg was made higher than that of the pAl2O3/ Mg of the previous report. The SiCp/ Mg was about 2/3 times as light as the practical aluminum alloys. The hardness of the SiCp/ Mg was about 1.5 times as high as that of the pAl2O3/ Mg and exceeded that of AZ91D, which excels at the mechanical properties in the practical Mg alloys. The highest value was 95HV. The bending strength of the SiCp/ Mg was better than that of the pAl2O3/ Mg. From the analytical results of XRD and SEM-EDAX on the SiCp/ Mg, it is thought that SiCp is almost uniformly finely dispersed in Mg and that the Mg grain becomes superfine.
Hair-cutting scissors are professional tools for barbers and hair stylists. Therefore, durability with repeated every day use is needed. It is known from past research that the cutting ability worsens when edge roughness factors Rz and Ra and the edge radius grow. In this report, we seek to find the material characteristics that have a strong relationship with these three values. For Rz, it is known that the influence of the hardness of the material is large. It is desirable to use a hard material to keep the Rz value low. For Ra, it is known that the influence of the size of the wear particles generated when the material is worn out is large. It is desirable to use a material that has a small wear particle to keep the Ra value low. For edge radius, it is known that the influence of abrasion resistance while the scissors are being used is large. It is desirable to use a material with a high abrasion resistance to keep the edge radius value low. A material that has all three of the different characteristics explained above concurrently is desirable for attaining high durability in hair-cutting scissors.
The deformation behavior of metallic hollow spheres (MHSs) at elevated temperatures is examined by numerical analysis and experiments for a unit cell model as a basis of building up a constitutive equation for the firing process of MHS compacts. Changes in terms of reductions in height, contact area and equatorial diameter in compression under a constant load are clarified for a single hollow sphere with various shell thicknesses by viscoplastic finite element (FE) analysis. Compression tests for the real unit cell, made of eight iron hollow spheres, are performed at high temperatures by using a thermomechanical analyzer (TMA) to verify the numerical calculations. The material constants are also determined, by similar compression tests, for bulk specimens made from the same iron powder as the MHS material. The compressive behavior of the iron hollow sphere structure at elevated temperatures can be described well by the FE model with a diffusional creep law.
Geometrical change in metallic hollow spheres (MHSs) during compression at elevated temperatures is formulated by using the results of the viscoplastic finite element analysis of a unit cell model. The parameters related to the viscosity, contact area and diametral area of MHSs are approximated by functions of the shell thickness, and placed into a constitutive equation for the sintering of powder particles. Pressure sintering of iron hollow sphere compacts is also performed in a tube with weights. The reduction in height of the compacts varies with the shell thickness of the MHS and the pressure and temperature during sintering. The compressive behavior of the compacts in the firing process is predicted well by the proposed constitutive equations.