Development of methodology for calculation of permissible stresses for evaluation of contact strength of cylindrical gears in case of overload

The article focuses on the development of methods for determining the allowable stresses to check the contact strength of the spur and helical gears under overload. Short-term overloads in gears occur under the action of maximum moments during the start-up of the device or due to the other reasons. The calculation of these loads is performed to check the static strength of the transmission teeth. The analysis of the limiting state of the material in the working area of the gear teeth was performed using the Pisarenko-Lebedev strength criterion, which is one of the most common strength conditions. The method of calculation of allowable stresses was developed. The calculation of limit stresses for normalized, improved or hardened wheels, as well as for the wheels after hardening by chemical-thermal treatment. The calculation results were compared with the values recommended by the standard. It was shown that the permissible contact stress for helical gears is slightly higher than for straight gears. Practically for all heat-treated steels used in the manufacture of gears, the norm of permissible limit stresses recommended by the standard is higher (in some cases significantly) compared to the stresses required from the conditions of contact strength. © Published under licence by IOP Publishing Ltd.