Recent ultrahigh-tensile-strength steel sheets have become indispensable for improving fuel economy through their incorporation into skeletal parts of automobiles to reduce the weight. To enable the forming of ultrahigh-tensile-strength steel sheets, a high-performance upper cushion is indispensable. The developed high-performance frictional gas cushion device applies as cushion force by frictional force generated by sliding between metal parts of the shaft parts and the hole parts having interference. Frictional cushion force mechanism was added to the upper piston shaft portion of the gas cushion device. In this apparatus, in addition to the repulsive force (gas cushion force) generated by the gas when the piston is pushed into the cylinder, frictional force (frictional cushioning force) due to interference between the inner surface of the cylinder and the outer surface of the piston shaft can be obtained. Therefore, it is possible to obtain a higher cushioning force than that with the conventional gas cushioning apparatus, which generates cushioning force only by the repulsive force of the gas.
A new technique of the three-dimensionl photolithography is introduced for fabricating the texturing reliefs on the cylindrical roll surface. The advantage of the photolithography realizing the high throughput against the fine arbitrary pattern shape is effectively applied on the roll surface by introducing a sheet with a polyvinyl alcohol layer. After the wet etching of the roll steel and the electro-polishing, the convex ring arrays are obtained. All designed patterns of the 4-different ring arrays having the corresponding pitches of 300-900 dpi are obtained. The ring outer diameters are 26-76 µm and their array pitches are 28-84 µm in design. The pattern smaller than 50 µm is said to be undetectable for the naked eye. The minimum ring width is 7 µm in design. Its average in real is 2.75 µm due to the under-etching of the roll metal. Such fine texture pattern on the roll has the smooth profile without the spike, which is occurred when the conventional shot peening is applied. The ring pattern is properly transferred to the aluminum plate without the tear. The pattern sizes on the roll and on the transferred aluminum plate agree reasonably each other with the standard deviation less than 3 µm in size. Since the finer ring pattern array can generate the larger light diffraction effect, the incident illumination light shows the wider reflected and diffracted optical angles. The overall surface shows the frosted white color tone. Overall, the combination of the techniques of the photolithography and the mechanical rolling are demonstrated.
As a new strength evaluation method for hard coatings such as diamond-like carbon (DLC), the cyclic indentation test was proposed. Then, a test rig was fabricated and used for the evaluation of DLC. DLC and a Cr/C inclined interlayer for the improvement of the adhesion strength of DLC were prepared by the unbalanced magnetron (UBM) sputtering method on heat-treated and polished JIS SCM415 substrates. Si3N4 spheres having diameters of 10 mm were used for the cyclic indentation test. 10000 cycle indentations brought about DLC fracture and detachment in the indentation impression. Also ring cracks were observed around the impression. I(D)/I(G), which is the ratio of the D to G peak intensities, decreases towards the center of the impression. It was considered to indicate decreasing sp2 cluster size in DLC. On the other hand, compressive stress increased near the surface of DLC in the contact area, as indicated by the change in its G peak position. It seemed to be the cause of the fracture and detachment of DLC in the impression.
A traditional DLC coating has been designed to control its contents of sp2, sp3, and hydrogen atoms as well as the additive elements. In addition to this concentration control, both the density and cluster of carbon substructures were important in the advanced DLC coating design. Two types of nanostructuring were proposed to control the mechanical properties and tribological performance of DLC coatings; e.g., nanolamination and nanocolumn formation. In the former, a DLC-film consisted of multi-stacked sublayers with different densities to prolong the die life. In the latter, the nonlinear elasticity of low density carbon columns with high density carbon inter-columns, prevents the glass mold stamping die from adhesion to oxide glass.