| As one of important construction machinery and equipments, hydraulic excavator is widely used in earthwork construction and mine exploitation, such as in architecture, road engineering, water conservancy, port building, national defense project, etc. The excavator with a backhoe is one of the most important digging machines and is mainly used to excavate the earth under ground.Backhoe attachment is the main performance equipment of hydraulic excavator. The rationality of the structure directly impacts on working performance and reliability of the machine. Because of complicated and variational load, the reliability is concerned particularly. In traditional design method, designers assumed several dangerous poses according to experience, and then analyzed strength of the structure manually. But this approach is not satisfied with the requirement of product development and design. In order to find the severe work condition of steel structure of the backhoe attachment of hydraulic excavator, a calculation model for theoretical digging force under combined work condition is established. With rapid development of computer technology, computer aided engineering (CAE) technology becomes more and more perfect and efficient. It gradually replaces status of traditional method and becomes an important approach in the filed of product development and design. The paper simulates the load on backhoe attachment in dangerous poses and conducts structural static analysis of all parts by ANSYS. In this way, the stress and displacement on all parts of the attachment can be calculated accurately and quickly, and contributes to make improvements of the integral or local structure.The content of dissertation can be summarized as follows.â‘ Basic theory and process of the finite element analysis and its software ANSYS simply are presented.â‘¡A calculation model for theoretical digging force under combined work condition is established. With this model, program to solve the occurrence of work condition with the maximum digging force on the bucket tooth, experimental work condition and their relatively structure stress is made with the software MATLAB. Thus more load data is provided for using FEA software to quickly analyze the stress of work attachment.â‘¢Taking the Backhoe attachment a miniature excavator as an example, the structure analysis of boom and arm are conducted. Their 3D structure models are built with software Pro/Engineer and imported into ANSYS. After defining the element type and material attribute based on practical situation, finite element models are established.â‘£In the process of FEA, firstly, the basic data of the excavator is inputted into the program, and the loads on pin-holes of the backhoe attachment under various work condition are obtained; secondly, the boundary condition of boom and arm and the processing mode of loads on the hole can be determined, and displacement and load are applied to finite element models; finally, the stress distribution on boom and arm under various work condition are achieved. The results show that, for the excavator studied in this paper, the maximum stress of steel structure of the boom and arm is higher under combined digging condition than that under experimental work condition.Though the analysis of various excavators may not be same, when analyzing their stress and reliability of structure, both experimental work condition and combined digging condition must be considered. The calculation mathematic model for theoretical digging force of backhoe attachment under combined work condition is not only used to conduct finite element analysis of work attachment but also can be applied to base plate design, excavation performance analysis, calculation of equivalent load of swing bearing and stability analysis. Consequently, theoretical basis of evaluating excavator for all aspects of performance more completely is provided.
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