This paper presents a study on effects of the pre-treatment and the heating time on the hardened layer and the bending fatigue strength of induction hardened gears. The measurement of hardened layer and the bending fatigue test of induction hardened gears made of thermally refined and as-rolled S35C and S45C steels were carried out, and then profiles of hardened layer and S-N curves were obtained. Effects of the pre-treatment and the heating time on profiles and micro structures of hardened layers of induction hardened gears were examined. The relationship between the bending fatigue strength and the profile of hardened layer was determined. An optimum heating condition for the bending fatigue strength of induction hardened S35C and S45C steel gears were indicated.

The measurement of hardened layer and the bending fatigue test of S35C and S45C steel gears induction-hardened under various heating conditions were carried out, and then profiles of hardened layer and S-N curves (bending fatigue strength) were obtained. Effects of the heating time, the electric power and the frequency on profiles and micro-structures of hardened layers of gears were examined. Relationship between the bending fatigue strength and the profile of hardened layer was determined. Optimum heating conditions for the bending fatigue strength of induction-hardened S35C and S45C steel gears were indicated.

This paper discusses design methods for the internal structure of molds used in production utilizing metal laser sintering combined with high speedmilling which selectively sinters metal powder to form a three dimensional mold. This milling technique is characterized by the fact that the selective laser sintering process and milling process are carried out in alternating sequence, achieving the level of processing accuracy demanded of mold production. In addition, in the selective laser sintering process, because the mechanical strength of the sintered body (Young’s Modulus) is variable, suitable interior structures that consider dynamic conditions are expected. However, in the current state of design, this structure is determined experimentally, and there is a high possibility of incurring unnecessary production time and high costs. In this paper, we investigate a method that incorporates an optimization method using stress that occurs within the structure interior, obtains the interior topological structure as a Young’s Modulus distribution, and designs a suitable interior structure using this distribution. As a result of investigation using numerical analysis, we obtained a structure that reduces the volume of the sintered body, having high mechanical strength in comparison with a conventional structure while improving structural rigidity.

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