Structure Improvements Of Excavator Based On The Life-cycle Analysis Method

Excavator, as a kind of important engineer machinery, is widely used in road engineering and other fields. It has three parts:working device, rotary device and running gear. For the working device, being articulated by arm、boom and bucket, it can complete mining tasks directly. All various and flexible movements are achieved by the relevant hydraulic cylinders. The running gear is used to ensure the stability of the whole machine.The versatility function is the typical characterization of an excavator, the complex are reflected in the following aspects:(1) the complexity of working objects. Various mining materials, such as soil and rock in different densities, lead to complicated force and elusive actual digging force of an excavator.(2) the diversity of working positions. The working position of excavator is determined by the relative position of the inclusive working device; importantly, excavator operating belongs to a multiple-degree-of-freedom system.Fatigue failure is the principle failure of mechanical structure. On account of being used extensively and frequently, excavators with small tonnage tend to damaged easily and seriously. In order to solve the problems aforementioned, this paper investigated the following questions:(1) Stress test. By testing the strain of typical positions for the structures, the stress distribution of vehicle structure is achieved. Then the stress levels and changing regularities of critical points can be determined further. In this way structural strength is evaluated and the actual load spectrum being treated as the basis of the fatigue analysis is obtained finally.(2) Finite element analysis. The stress levels and distribution of the structures are labeled by analyzing dangerous working conditions of excavator. To determine the stress of the structures from the perspective of strength, files for fatigue life analysis with results from finite element analysis are input into MSC.Fatigue2005.(3) Life calculation for excavator structure by loading actual load spectrum and the S-N curve of materials is analyzed by MSC.Fatigue. Then the original structures will be improved according to analytical results. Meanwhile, the improvement scheme life will be analyzed again to ensure the same condition, same load spectrum and same S-N curve.(4) The novel design scheme can be drawn out by comparing the static analysis of ANSYS and the results of fatigue life. Through the available structure improvements, to pave a reliable way for further structure design of excavators.