Abstract: In this paper a new electrical method has been developed for measuring the width of instantaneous contact locus for the helical gears with double-circular-arc tooth profile.The formula of width of contact locus may be derived through regression analysis of different width of contact locus obtained from different helical angles and loads of the gears. Afterwards we have derived the for-mula of contact stress based on the formula of width of contact locus. The endurance limit for contact stress was obtained from the fatigue test of a set of gears. Both contact stress formula and endurance limit stress together may be used for calculation of surface durability of this kind of gears in basic profile JB2940-81.

Key words: 极限应力, 接触迹, 接触应力, 疲劳试验, 双圆弧齿轮