The Effect Of Tooth Root Grinding Form Of Carburized And Quenched Gear On Bending Strength

Grinding gears of carburized and quenched has become the main form of modern gear transmission for the advantages of high load carrying capacity, high transmitting efficiency, low vibration, low noise, widespread power and speed suitability, etc. In the production process, grinding notch or machined edge were usually produced in the vicinity of effective tooth flank and transition curve due to the effect of technics, tool and heat treatment, etc. As the position of them are special, their impact on tooth bending strength must be considered.In this paper, the effect of grinding notch and machining edge on tooth bending strength of carburized, quenched, and grounded cylindrical helical gear was studied. The main research works were:1. Based on principles of gear conjunction theory, numerical solution of tooth curve of pre-grinding cylindrical helical gear was deduced.2. Mathematical model of FEA on tooth bending strength with complex boundary was established by means of compound modeling with Macro file of SolidWorks and MATLAB, based on full-text data file. Reasonable boundary conditions and the worst loading positions were analyzed.3. Tooth root maximum tension stress with FEA for two cylindrical helical grounded gears of carburized and quenched was calculated, with all kinds of grinding notchs and machined edge. Comparison the calculated results with ISO 6336 results shows that the model were correct, boundary scope and loading positions determination were suitable.4. The effect of grinding notch form of geometry size especially position on maximum tooth root bending stress were:with sufficient involute length, the smaller the notch radius is, the greater of the maximum tooth root bending stress, vice versa; with the same notch radius, the heigher of grinding notch than Hofer 30°tangent critical section, the smaller of maximum tooth root bending stress; machined edges have no effect on concerning stress.Therefore, with sufficient involute length of prehobbed, carburized, quenched, and grounded cylindrical helical gear, the less of removed metal, the better of its tooth bending strength.In order to gain higher tooth rooth bending strength, the grinding surplus should be smaller, the fillet radius of notch should be bigger, the position of notch should be higher.The results can be used as reference for tool improving and process optimization, also for analysis of tooth root bending strength and failure analysis.