The Experiment Research Of Loading Spectrum Of Excavator Boom And Its Fatigue Life Estimation

Excavator is one of the main working devices in the earthwork construction, which plays a very important part in the country’s infrastructure construction. The working load of the excavator is complicated and changeable. As the main stressed component, the working device is easy to be damaged under the long-term actions of alternating loads. Due to the lack of the load spectrum data of the working device and its components, the research on the fatigue life of the system is greatly restricted. Therefore, it is significant to study the obtaining method of the load spectrum and the fatigue life of the components. These works can guide the design of excavator and improve the life and performance of the excavator.In this thesis, the excavator XE215 G of Xu Zhou Construction Machinery Group was studied. The research contents are as follows:Based on the analysis of the structural characteristics and loads of the working device of excavator. A parameterized finite element model the working device is established by use of software ANSYS. For improving the simulation efficiency, a control program is coded by Visual Basic to adjust the finite element model with different conditions and loads. The conditions for verifying the reliability of the test, which is used to measure load spectrum, are created.According to the "corner" method and combining with the characteristics of the main arm, the measuring points are determined. Besides, the structure of the test system, test principle, sensor and its installation method are introduced in great detail. After that, the error comparison between the measured stress value and the simulation one on the section of main arm at different working conditions and different loads is carried out. The results showed that the relative error between the measured stress value and the simulated one is almost all within the allowable range, which ensures the accuracy and reliability of the load spectrum data.After analyzing a large number of measurement data, the data corresponding with the stage of excavation is extracted, the load-time histories of hinge points D and E are obtained. Then, the load-time history, the results of finite element analysis and the N-S curve of material are loaded into the fatigue analysis software nCode to estimate the fatigue life, and the analysis results is thus obtained.The methods proposed in this thesis for setting the parameterized mode, selecting the measurement point and verifying the model of working device and its components make up for the domestic research on load spectrum to some extent. And the research results have a certain reference value in the study of the load spectrum of the engineering machinery products.