1. Shaft failure forms: mainly include fatigue fracture due to insufficient fatigue strength, plastic deformation or brittle fracture due to insufficient strength, wear, deformation and vibration exceeding the allowable range, etc.

2. The design of the shaft shall meet the following criteria:

(1) Select suitable materials, blank forms and heat treatment methods according to the working conditions, production batch and economic principles of the shaft.

(2) Determine the reasonable structure shape and size of the shaft according to the specific requirements of the force of the shaft, the installation position of the parts on the shaft, the matching size and positioning mode, the processing method of the shaft and so on, that is, the structural design of the shaft.

(3) Strength calculation or check of the shaft. For the large force of the slender shaft (such as worm shaft) and the high stiffness requirements of the shaft, but also stiffness calculation. The vibration stability calculation should be carried out for the shaft working at high speed because of the risk of resonance.