従来のショットピーニングと微粒子ピーニングを組合せた二段ピーニングで付与される残留応力の分布形態とそれが浸炭焼入れ歯車の折損強度に及ぼす影響

概要

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Fine particle bombarding (denoted hereafter as FPB) has a superior effect on improving tooth surface strength (pitting resistance) of gears compared to conventional shot peening, which was reported by the author. Since it is well known that the conventional shot peening increases tooth bending strength of gears, double peening using FPB after the conventional shot peening is expected to improve both tooth surface strength and tooth bending strength of gears. The purpose of this study is to clarify the effect of the double peening on the bending strength of carburized gears. First, the author measured the residual stress distribution of the tooth root of the gears treated with the double peening under different peening conditions. The results showed that high residual compressive stress was produced near the surface by the secondary FPB. On the other hand, it was found that certain conditions of FPB released the residual compressive stress produced by the primary shot peening in a deeper region. Next, durability tests were carried out using the gears to measure the tooth bending strength. As a result of the tests, tooth bending strength was improved by using suitable conditions of FPB as the secondary peening. However, when the secondary FPB released the residual compressive stress produced by the primary shot peening in a deeper region, no improvement of tooth bending strength obtained because subsurface fatigue fracture was induced.
2009-08-25