Reliability Modeling Of Motorized Spindle Based On Step-stress Accelerated Degradation Test With Two Accelerating Stresses

The lack of reliability of middle and high grade CNC machine tools has become the key problem that restricts the development of high-end manufacturing industry in China,and the lack of reliability of domestic electric spindle is an important factor that restricts the reliability of CNC machine tools,so it is very important to study the reliability technology of the spindle.At present,one of the biggest technical difficulties of motorized spindle reliability research is how to evaluate the reliability of electric spindle scientifically and objectively.As a problem about complex mechatronic hydraulic system,the reliability evaluation of the spindle involves both the complex degradation failure and the functional failure mechanism analysis.It also includes the engineering problems such as state monitoring and fault warning.And because of the long life,the spindle has little functional failure in the normal condition.Also the reliability of the traditional motorized spindle is so reliable that the test and the corresponding assessment methods are too expensive,and the cost is too large,so it is difficult to get the life characteristics of spindle in time.For this reason,a binary reliability evaluation method for motorized spindle is established based on step-stress accelerated degradation test with two accelerating stresses.The effectiveness of the method is verified in the experiment.The main work of this article is as follows:First,we outline the background of this research,analyze the purpose of this research,and summarize the research progress in this field.Secondly,the working principle of the motorized spindle is explained,the degradation mechanism is analyzed,the life characteristic quantity and the type of stress are screened,and the accelerated degradation test scheme is formulated in accordance with the test room conditions,and the detailed rules of the test scheme are explained,and the test system is briefly introduced.Thirdly,the common distribution model,the degenerate model and the acceleration model are summarized,the corresponding expressions are given,and the applicable conditions of various models are analyzed.The complete operating flow of modelingbased on the radial runout and vibration and model evaluation basis are summarized respectively,which provides the theoretical basis for the acceleration degradation modeling of the motorized spindle.Fourthly,combining the actual situation of the engineering and the actual electric spindle,the degradation and acceleration model suitable for the electric spindle is selected for each distribution model of two degenerate variate,and the method proposed in this paper is used to establish unitary reliability models of the spindle for radial runout and vibration respectively.The paper evaluates the reliability and compares the advantages and disadvantages of different models,which will lay the foundation for the coming binary reliability modeling.Finally,the copula function is introduced as the connection structure of the unitary model to the binary reliability modeling of the motorized spindle.The independent and related cases of the degradation are considered respectively,and the results are compared with those of the unitary reliability model.