Study On Load Spectrum Compilation And Fatigue Life Prediction Of Machining Center Spindle

Reliability of NC machine tool is determined by the reliability of key functional components of NC machine tools. It is particularly important to improve the reliability of machining center spindle for it’s the key functional components of NC machine tools. In order to improve the reliability of machining center spindle, the compilation method of the load spectrum of machining center spindle is studied in this paper, and the load spectrum of machining center spindle is compiled. On the basis of the load spectrum of machining center spindle, the fatigue life of machining center spindle is predicted,which provides reference for reliability design of the machining center spindle.The research status of the load spectrum is analyzed. The general compiling procedure of load spectrum of mechanical products is summarized. And the method of compiling the load spectrum of machining center is compared with that of other mechanical products.The determination method of process parameters for typical working conditions is studied. In order to ensure that the typical conditions of the machining center can be on behalf of all conditions, the cutting loads calculated by the empirical formula are analysed by the method of mathematical statistics.And the cutting force probability distribution model is established. The process parameters of typical working conditions are determined by use of the probability distribution model of cutting force.Cutting test is done with the process parameters of typical working conditions. Build a cutting force test platform. The load of typical conditions is collected by Kistler dynamometer in the process of processing, and the load signal is processed.The compilation method of the load spectrum of machining center spindle is studied. Rain-flow counting method is selected to count the number of cycles in cutting force signal. The statistical analysis of the mean amplitude of the cutting force is done. The joint probability distribution function of cutting loads mean amplitude is established. The parameters extrapolating processing for load spectrum is done by using the distribution function. And the load spectrum used for spindle fatigue life prediction is compiled.Fatigue life prediction of spindle is done by using the load spectrum. Firstly, the force conditions in the course of processing of the machining center spindle is analyzed. The static characteristics analysis of spindle is done by using finite element analysis software Patran combined with the maximum load in the load spectrum, which is used to determine which kind of load is the cause of fatigue failure of spindle. Goodman criteria is used to established fatigue life prediction eight level program loading spectrum of spindle. Fatigue life of spindle is predicted by using fatigue analysis software MSC.Fatigue, and the potential failure locations are found.