Research On Elastic Fatigue Failure Of Disposable Machine Based On Stochastic Finite Elemant Analysis

The disposable machine that is widely used in the area of aerospace and military refers to the mechanical products which have a relat ively short lifespan between enabled and scrapped. Compared with the common machine, the disposable machine undertakes nearly yielding and low cycled fatigue load which is different from the high cycled fat igue of commo n machine, besides the shorter lifespan. In this paper, the theory of elast ic fatigue failure i s used to express the deformat ion progress. The theory of elast ic fatigue failure life is adopted to evaluate the lifespan of this kind of machine. The standard of 0.2% residual strain is used to raise the design guidelines of elast ic fatigue failure. In t he meant ime the stochast ic finite element simulat ion based on the Monte Carlo theory is founded to perform the simulat ion research on the process of elast ic fat igue failure, which teaches us a different method to design and check the disposable machine.First ly, theory of elast ic fat igue failure is researched thoroughly and the conclusion that the nearly yielding and low cycled process is a coupling process between mixed hardening and damage accumulat ion is made. Incremental strain-stress const itut ive model is founded based on elastic-plast ic mechanics and damage mechanics, which provides a theory foundat ion for the analysis model.Secondly, the Gauss distribution of metallic mechanical properties in micro-level is made from the data fitt ing by MATLAB where the data is obtained fro m the electron backscattered diffract ion experiments and Nano-indentat ion experiments. On the basis of the distribut ion, the mixed programming between MATLAB and PYTHON is used to found the stochast ic finite element analysis model to perform some simulat ion research on the process of elast ic fat igue failure, so that the factors which influence the elast ic fat igue failure life is found. At last a series of low cycled fat igue experiment is designed and performed according to the feature of load on the disposable machine. Data of these experiments is consistent with the simulat ion so that the accuracy of stochast ic finite element model is checked.Finally, pract ical design and manufacture of disposable machine is conducted according to the elastic fat igue failure design theory and disposable machine thought. In terms of the index raised by some factory, disposable planetary roller screw is designed and manufactured. Compared with the parameters from the common planetary roller screw desig ned as common machine, the parameter of disposable machine such as size, load and life is consistent with the index better, which proves the advantages of disposable machine in some spot where the disposable feature of machine is needed.