| Accurate prediction of fatigue life of notched structures is the research focus of anti-fatigue design of engineering structures.Due to the heterogeneity of microstructure,the complex influence of defects and the errors in the process of processing / measurement,and under the intervention and drive of certain subjective experience,the fatigue life of the same group of specimens under the same service state shows great scatter.Based on this,in order to ensure the structural integrity and service safety performance of aviation key parts,and realize the reliability design from certainty to uncertainty,this study takes 2026-T3511 aluminum alloy as the research object,uses the notched plate tensile sample,and studies the probabilistic life prediction model establishment and reliability analysis method of aluminum alloy materials.The main research contents are as follows :(1)By studying the overall stress of the plate tensile specimen with notch,the analytical expression of nominal stress considering notch effect is constructed.Based on the normal distribution theory and the least square method,a fatigue life prediction probability model of notched plate tensile specimens with a certain degree of reliability coupling notch effect,average stress effect and fatigue scatter is established.The validity of the model is verified and analyzed by comparing the life data predicted by the model with the fatigue life test data of2026-T3511 aluminum alloy notched plate tensile specimen.(2)The mechanical properties of 2026-T3511 aluminum alloy plate notch tensile specimens were tested by means of tensile machine,and the stress-strain curves of different notch shapes were obtained.The Abaqus finite element numerical simulation test of material fracture was carried out,and the stress concentration of the dangerous part of the structure and the stress field distribution after the notch tip entered the plasticity and the fatigue failure mechanism of the notch specimen were analyzed.The virtual crack length at the notch tip under Mises equivalent stress distribution is solved,and then substituted into the established fatigue life prediction probability model of notched structure,and the applicability of the model is verified.(3)The Bootstrap method is used to expand the fatigue data of small samples at the highest stress level,and the equivalent life conversion principle is used to convert the data obtained at the highest stress level into a lower stress level.The original small sample data at the low stress level is fused with the converted data to obtain the equivalent large sample data.Then,the extended data are used to probabilistically process the model parameters according to the genetic inversion algorithm.Finally,the life reliability curve is obtained based on the stressstrength interference model and the small sample P-S-N curve is fitted.The reliability of the probabilistic fatigue life of the aluminum alloy 2024-T351 notched small sample is analyzed,and the reliability of the model is verified. |
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