Finite Element Analysis And Fatigue Life Prediction Of Hydraulic Excavator Working Device

Hydraulic excavator is a typical construction engineering machinery, which is widely used in industrial production, civil construction, road construction, water conservancy, oil mining, public works, airport and port construction, and other departments of the earth. The load changed violently in the mining process, and excavator working device, which is the direct implementation to complete working, bears the harsh load in the bad conditions, so excavator working device's strength, reliability and durability is directly related to the excavator performance and efficiency. Therefore, the study of excavator working device's intensity and reliability has a very essential significance.In this paper, a mini hydraulic excavator's working device is researched, which is analyzed using finite element software Ansys, based on the overall finite element analysis method. In order to make the analysis more realistic, the hinge point is treated as contact, and the hydraulic oil in the hydraulic cylinder build as solid model. The relevant parameters will be given to the oil entity, in order to simulate the influence of the solid-liquid coupling to its performance. At the same time, the load time history of each test point is measured using strain test system, and the fatigue life of each point is estimated after analyzing the test result. A specific course of the study is as follows:(1) The excavator's digging resistance and theory excavating force are analyzed systematic through analyzing the characteristics of digging objects and excavator's digging action and considering the various constraints factors under actual operating conditions. The six typical conditions are determined as a major attitude of mechanical analysis, and the theoretical digging forces are calculated under various conditions.(2) In order to make the analysis more realistic, the hinge point is treated as contact, and the hydraulic oil in the hydraulic cylinder build as solid model. The relevant parameters will be given to the oil entity, in order to simulate the influence of the solid-liquid coupling to its performance. Through the overall finite element analysis and modal analysis of the excavator's working devices, the weak parts of the stress concentration and stiffness are determined in the corresponding condition, which provide reference for the maintenance and improvement of the working device.(3) By using the strain measurement system, the load histories of the weak parts are measured in the paper. The load histories are analyzed with rain-flow counting method, and the structural S-N curve is corrected based on the fatigue test data of the material. The fatigue life of every test point is estimated by using the nominal stress method, which achieves the goal of fatigue life prediction of the working mechanism. This method can also give reference for the similar mechanism.