The failure factors of mechanical parts are many and complex, involving the structural design of parts, material selection, material processing and manufacturing, product assembly, use and maintenance and other aspects.

(1) Unreasonable design: it mainly refers to the incorrect or unreasonable structure and shape of parts, such as parts with gaps, small arc corners, transition areas of different shapes, etc. On the other hand, it refers to the insufficient estimation of the working conditions and overload of parts, resulting in the lack of actual working ability of parts, resulting in early failure of parts.

(2) Unreasonable material selection: the form of parts failure in the design is wrong, the properties of the selected materials can not meet the requirements of the working conditions; Material selection based on the performance index can not reflect the material resistance to the actual failure form, the selection of wrong materials; The selection of materials is too poor quality, composition or performance is not qualified to meet the design requirements and so on are not reasonable material selection.

(3) Unreasonable processing technology: improper processing technology of parts may produce various defects, leading to early failure of parts in the use process. Such as overheating, overburning and banded organization in the process of hot processing; Decarbonization, deformation and cracking occurred during heat treatment. Deep tool marks and grinding cracks appear in cold working process.

(4) Improper installation and use: the assembly and installation process does not meet the technical requirements, such as too tight, too loose, inaccurate in the installation, fixing instability, etc., may lead to the parts can not work normally or premature failure; In addition, illegal operation, overload, speeding, not on time repair and maintenance in the process of use will also cause premature failure of parts.