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Cold forging of pinion gear with shape of outer spur gear and inner helical gear have been investigated in this study. A numerical analysis for preform design substituting cutting process in gear forging was developed by means of upsetting process. By using the finite element program DEFORM-3D, the analysis is carried out. Using this simulation, the preform of pinion and helical gear forging process were designed. The suggested process is verified by experiment. Compared to the traditional CNC processing, the upsetting process can form a preform without cutting, which leads to shorter forming time and reduce material usage.

Effects of various heat treatment processes, including "Q/T (quenching and tempering)", "Q/CT/T (Quenching, cryogenic treatment and tempering)", "Q/T (quenching and tempering) + Ti-nitriding" and "Q/CT/T (Cryogenic treatment and tempering) + Ti-nitriding", on S-N fatigue behavior of AISI D2 tool steel were investigated. The optical micrographs and Vicker's hardness values at near surface and core area were examined for each specimen. Uniaxial fatigue tests were performed by using an electro-magnetic resonance fatigue testing machine at a frequency of 80 Hz and an R ratio of -1. The overall resistance to fatigue tends to decrease significantly with Ti-nitriding treatment compared to those for the general Q/T and Q/CT/T specimens. The reduced resistance to fatigue with Ti-nitriding is discussed based on the microstructural and fractographic analyses.

Effects of various heat treatment processes, including "Q/T (quenching and tempering)", "Q/CT/T (Quenching, cryogenic treatment and tempering)", "Q/T (quenching and tempering) + Ti-nitriding" and "Q/CT/T (Cryogenic treatment and tempering) + Ti-nitriding", on S-N fatigue behavior of AISI D2 tool steel were investigated. The optical micrographs and Vicker's hardness values at near surface and core area were examined for each specimen. Uniaxial fatigue tests were performed by using an electro-magnetic resonance fatigue testing machine at a frequency of 80 Hz and an R ratio of -1. The overall resistance to fatigue tends to decrease significantly with Ti-nitriding treatment compared to those for the general Q/T and Q/CT/T specimens. The reduced resistance to fatigue with Ti-nitriding is discussed based on the microstructural and fractographic analyses.

Backward extrusion is the most common method of forming bosses within product cases. However, backward extrusion requires a very large forming load, and has the disadvantage of producing dimple defects when forming thin sheets. To overcome this disadvantage, we investigated a method of bottom compression drawing to replace backward extrusion. Bottom compression drawing is a technique in which, during normal drawing, back pressure from the counter punch that opposes the drawing punch applies a load on the blank, so that compressive force acts on the bottom face of the blank. Bosses are formed at the same time as the case is formed as a result of this drawing. Backward extrusion and bottom compression drawing were compared using both FEM analysis and experiment in the formation of solid bosses. The results showed that bottom compression drawing could form a piece with about 60% of the forming load used with backward extrusion; and that dimple defects were less likely to occur with bottom compression drawing than with backward extrusion.

Backward extrusion is the most common forming method of the solid boss integrated with product cases. However, backward extrusion requires a very large forming load and has the disadvantage of producing dimple defects when forming thin sheets. To overcome this disadvantage, the bottom compression drawing process has been developed to replace backward extrusion. The bottom compression drawing can form a solid boss with about 50% of the forming load required for backward extrusion and dimple defects are less likely to occur than with backward extrusion. In the present paper, the formability of boss influenced by lubrication and tool roughness will be described. It was recognized that the dimple defect occurs at very early stage when the counter punch is lubricated by lubricant. With increasing surface roughness of counter punch, the formable zone of solid boss expands. Adhesion on counter punch surface can be recognized with forming cycles repeating under dry condition but the irregularity in the product configuration converges to a befitting configuration after a few forming cycles.

In the automobile manufacturing industry, it is demanded lighting the parts for protecting the environment from CO₂ and the decrease of the manufacturing cost and energy. This research aims at developing plastic deformation processes for the triple cup that has two bosses on upper and lower sides in the cup shape. A new sheet forging process is discussed in which a sheet metal is firstly worked to a drawn cup by deep drawing process and then deformed to the target shape by compressing the cup edge. The process feature has been investigated by using FEM simulation and verified by a series of press forming test.

A measurement system for predicting the stress state at the dangerous points of the die insert in the cold forging process has been proposed. In this measurement system, the hoop stress at the die approach can be conducted by measuring the strain at the die case. A FEM simulation showed that the relationship between the hoop stress at the dangerous point of the die insert and the strain measured at the die case is monotonous and sensitive. In this system, the hoop stress which is the major factor to control the fatigue behavior and die life is controlled by changing the press-fit interference. The die dimensions have been optimized by using FEM simulation. A series of forging experiments using the optimized die structure shows that the measured strain is the same as predicted by FEM simulation and the measurement system is useful.