| Because of the small turning radius, the small working space, flexible and convenient operation, mini excavator replaced of manual labor, plays a huge role in landscape construction and the cleaning at the scene of the engineering maintenance. Fatigue damage is the main failure form of mini excavator working device. Currently, mini excavator working device structure has been designed generally by static strength design method, but the working device fatigue design research is very few in domestic and international. Taking the mini excavator working device as the research object, this paper contains the fatigue life analysis and the finite life design of working device.Through systematically analysis of the composition and function of mini excavator working device, the main technical parameters of the working device is determined, and three-dimensional model of working device is established. By using the D-H method, it analyzes the motion of working device, and gets the components’position posture of the working device. Through systematical analysis of the each hinge point force of working device, the equations of each hinge point of force is obtained. Through static analysis of the key components of working device, the stress distributions and fatigue risk points of bucket, the arm and the boom are obtained.The excavator continuous working condition is discrete to seven conditions. The excavator’s each position of working condition has been simulated. Using the CAD graphical method find out the need dimensions and calculates the loads. Through static analysis in the seven working conditions, Stress and strain of each working condition of location are obtained. Then the approximate simulating load spectrum and response spectrum of fatigue risk points are established. The fatigue life is estimated by the local strain gauge on the bucket, arm and boom.Consider the economic and maintainability, the design life of working device is calculated. The finite life optimization model is established, and the finite life design is carry out by using response surface method. Through finite life design, the boom can meet the requirements of the fatigue life and weight16.6%lighter than before. The mechanical properties of materials are used efficiently.Through research of this topic, it provides method guidance of the fatigue life estimation and finite life optimizing design of mini excavator working device, helps the development of the design theory of excavator working device. At the same time, it is a reference for finite life optimization design of other complicated mechanical devices. |
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