Chiaki Namba

Contact Fatigue Strength and Wear Characteristics of Plasma-Carburized Rollers

In the plasma-carburizing method, the detrimental grain boundary oxides in the surface of the materials and sooting problems are eliminated and the high carbon content near the surface is easily achieved. This paper describes a study on the contact fatigue strength and wear characteristics of plasma-carburized rollers. Test rollers made of super-carburizing steel MAC14 and conventional carburizing steel SCM415 were plasma-super-carburized under different carburizing conditions. The contact fatigue tests were carried out for these plasma-super-carburized rollers. The effects of case depths on the contact fatigue strength of these rollers were determined. The effect of shot-peening on the contact fatigue strength was also examined by carrying out contact fatigue tests for shot-peened rollers. The wear tests were also carried out and then the wear characteristics of test rollers were determined. These test results for plasma-super-carburized rollers were compared with the results for gas-super- or gas-eutectoid-carburized rollers.

Simulation of Induction Hardening Process of Sintered Metal Shafts

A FEM simulation program for induction hardening of sintered metal shafts was made up. Physical properties of the sintered metal were measured. An electromagnetic field analysis, a heat conduction analysis and an elastic-plastic stress analysis during the induction hardening process of sintered metal shafts were carried out for various hardening conditions by using the measured material data and the simulation program. The effects of the electric power and the frequency on the temperature and the stress during the induction hardening process of the sintered metal shaft and the residual stress were examined. The map for selecting the optimum heating condition (P, f) for the residual stress of the sintered metal shaft due to the induction hardening was indicated.

Load Bearing Capacity of Super-Carburized Gears

This paper describes a study on the load bearing capacity of super-carburized gears. Test gears and rollers of MAC14 and SCM415 steels were super or eutectoid-carburized under different carburizing conditions. The impact and bending fatigue tests for test gears and the contact fatigue test for test rollers were carried out. The effects of case depths on the impact and bending fatigue strengths of gears and the surface durability of rollers were determined. The impact breaking limit energy of super-carburized gears was found to be larger by about 15% than that of eutectoid-carburized gears irrespective of case depth. The bending fatigue strength of the super-carburized gear was found to be almost equal to that of the eutectoid-carburized gear. The surface durability of the super-carburized roller becomes larger with an increase of case depth and is larger than that of eutectoid-carburized rollers in the case of larger case depth. The surface failure modes for super and eutectoid-carburized rollers were spalling. The load bearing capacity of super and eutectoid-carburized gears was found to become larger by shot-peening.Copyright

Effects of Gear-Side Case-Hardening on Residual Stress of Case-Hardened Gears.

This paper presents a study on effects of gear-side case-hardening on residual stresses of case-hardened gears. The carbon content of each element of the FEM models due to carburizing was computed on the basis of the relation between carburizing condition and carbon content distribution. A heat conduction analysis and an elastic-plastic stress analysis during the case-hardening process of spur gears were carried out for various case-hardening conditions by the three-dimensional finite-element method (3D-FEM), considering changes of the thermal expansion coefficient and the yield stress with the temperature and the carbon content distribution, and then residual stresses were obtained. The effects of the case depth, the case-hardened part (tooth surface, gear-side and bore), the face width, the rim thickness and the standard pressure angle on the residual stress were determined.