Fatigue Life Analysis Of Multiaxial Low-cycle Based On Plastic Strain Energy

In engineering practice, most components are working under multiaxial fatigue load. And so far, the method of life prediction for components which suffer multiaxial loading is not so mature. So the prediction of fatigue life under multiaxial low cycle loading has certain practical value and theoretical significance. Finite element software ANSYS is used to do simulate calculation and the theoretical research is combined to analyze the nature of the material fatigue damage. Refering to the latest research results of the energy method, a fatigue life prediction analysis of multiaxial low cycle based on plastic strain energy is proposed. The main research content is as follows:1. The main method of fatigue life prediction under multiaxial low cycle loading are introduced so far, and the advantages and disadvantages of various methods are represented in some detail.2. The physical basis of plastic deformation is introduced and a micro crack initiation condition is proposed in the form of cutting based on it. The maximum shear stress and the normal stress in the plane of maximum shear stress are introduced to the fatigue life prediction model under multiaxial low cycle based on a new plastic strain energy, which embodies the the influence of the enforcement and gives the fatigue life prediction formula with clear physical meaning. And then the theoretical derivation is done for the model so that can make combination with finite element numerical method.3. The test condition and experimental results of the smooth thin wall pipe specimen SM45 C steel, 304 steel, steel and Al5083 S460 N aluminum alloy are listed. And every loading condition of the smooth specimen is simulated by the finite element software ANSYS, then the relevant data can be extracted from its post program. Finally, the life of every smooth specimen can be predicted.4. The test conditions of the notched specimen nickel-based superalloy GH4169, the 16 MnR steel and the welding component Al5083 aluminum alloy are listed. The loading conditions of each notched specimen and the weldment can be simulated by the finite element software ANSYS. And the relevant data can be extracted from its post program. Finally, the life of each notched specimen and the weldment can be predicted.