| Mining excavator is the key mechanical equipment in large scale open pit. Its fatigue durability and reliability have a direct influence in the production efficiency and economic benefit of large surface mine; At the same time, along with the "Made in China 2025" strategy proposed, the development of engineering machinery with energy saving, environmental protection, reliable quality, cost saving and good performance has become the research direction in the field of construction machinery in the new era. With the foundation of the national high technology research and development plan(863 program) —“ Development of 75m~3 Large Scale Open Pit Mining Excavator(N0.2012AA062001)”,the fatigue life of the components of bucket and bucket rod of WK-75 mining excavator was studied in this paper, specific work including: static strength analysis, discrete element simulation analysis of mining process and multi-rigid-body dynamics simulation analysis, and on the basis of the above results the fatigue life is calculated in considering the difference of the physical properties of different materials.Based on reviewing the relevant domestic and foreign literature,this dissertation summarizes the development course of the mechanical excavator, the main research direction and its application technology at present. Combining the multiaxial fatigue failure criteria, aiming at the problem that the fatigue analysis of the excavator working device load spectrum is difficult to obtain, a new solution to calculate the bucket rod component fatigue life is proposed, then the following work was carried out:Firstly, a finite element analysis model was established in ANSYS Workbench software, then the step by step simulation calculation were calculated in the bucket dangerous condition and the bucket rod dangerous condition respectively, to check the static strength of the components. The results showed that the components meets the requirements of the static strength, and the bucket and bucket rod components has higher stress level in the bucket rod dangerous working condition, therefore its analysis results can be used as the basis for the calculation of fatigue life.Secondly, the simulation of material mining process which is based on the theory of discrete element method was carried out in EDEM software, the changing law of the gravity of the material in the bucket and the digging resistance were analyzed, then the load-time history results were processed to weaken the fluctuation caused by the randomness of particle formation. On the foundation of the kinetic theory, taking the processed load-time history results as the input parameter, the typical operation process simulation analysis was carried out in the ADAMS software, and the load-time history of lifting force and pushing force were obtained.Finally, based on the multiaxial high cycle fatigue life criterion, taking the result of finite element calculation in bucket rod dangerous working conditions as basic documents, combined with the fatigue performance parameters of the components, which is estimated by using Seeger algorithm, associating the load-time histories obtained by simulation with each load step in static analysis respectively,the fatigue life of the components was calculated by selecting the von Mises-Goodman algorithm in FE-SAFE software. In addition, change the load scale factor on the basis of the previous work, according to the corresponding relationship between the load scale factor and material level, the fatigue life was obtained in considering the difference of the physical properties of different materials.The research of this paper provides a method for the analysis of the fatigue life of the working device of large-scale mining mechanical excavator and a basis for the maintenance decision and structure improvement of the WK-75 mining excavator. It also has certain reference value on the finite life design and structure optimization design of the same series of large mining excavator. |
PDF Full Text Request