| Hydraulic excavator is a earthmoving construction machinery that widely used in engineering construction, road construction, irritation and water conservancy construction. It’s formed by three major modules, the upper slewing platform, undercarriage and working device. The working device is the major functioning module, controlled by three sets of hydraulic cylinders’fore and aft motion. Due to the adverse working condition and complex objects, the working device functioning as the part of excavating suffers complex loads. Whether or not it could guarantee the structure’s fatigue strength is an important indicator in the process of evaluating the machine’s performance.The method of static structural strength verification when the machine operates at risky posture is commonly in the process of designing working device. However, the structural failure of engineering machinery is largely due to the fatigue failure. To solve this problem, a mini excavator has been studied to calculate the fatigue life of danger spot on working device, using the method of computer simulation and dynamic stress tests.The rigid model of working device has been formed using ADAMS, then the kinematic characteristics been analyzed and trajectory envelop diagram been drawn, thus various performance parameters been obtained. Rigid-flex coupling model has been formed to simulate the excavating process, thus the dynamic stress-time course been obtained to offer reference for dynamic stress tests.Refer to the results of rigid-flex coupling simulation, tests has been conduct on fatigue danger spots of excavator’s working device. After data processing, the dynamic stress-time course of danger spots has been obtained. Rain-flow counting method has been used in nCode DesignLife to obtain the fatigue load spectrum for subsequent life calculation. Goodman method has been used to correct the affection of mean stress. The Miner rule of linear fatigue cumulative damage theory has been used to calculate the fatigue life of danger spots.An instructional method of dynamic simulation on hydraulic excavator’s working device and calculation of structure’s fatigue life has been provided by this research. The approach and implementation method of this research is transplantable to any other mechanical structure that suffers random loads.This research has been supported by State Key Laboratory of Construction Machinery. |
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