In the field of tooth bending strength calculation, the tooth bending strength formula including “tooth shape parameters” based on parabolic equal strength beam in laid the theoretical foundation for the calculation of straight cylindrical gear bending strength.
However, it seems too safe, so various measures are taken to improve it: adding various correction coefficients to correct the load and material strength of spur gears; Considering the influence of spur gear machining; In addition to bending stress, other stresses and stress concentration are also considered for tooth root stress; The shape of dangerous section transits from flat section to broken section; On the other hand, a method to judge the bending strength of spur gear based on the calculation formula of actual stress of tooth root is proposed. The calculation model of spur gear represented by “cantilever beam” has some limitations after later research and test:
① The determination of loading point and dangerous section position needs to be improved;
② There is a certain gap between the height thickness ratio of spur gear and the height width ratio of standard beam;
③ There are many factors affecting the strength of spur gears, such as tooth surface load distribution, movement, setting surface wear and transmission system deformation;
④ It is difficult to simulate the sharp change of tooth profile gradient and tooth root stress concentration of spur gear with equal strength theory.