Divide undercut into harmful and harmless undercuts by the influence of the undercut to the intensity, stiffness of gear and to the profile error.

• 针对目前对齿轮根切的定义过于笼统的问题,从根切对齿轮轮齿强度、刚度以及对齿形精度的影响角度出发,将根切分为“有害根切”和“无害根切”。