| In recent years,China's national economy from the high-speed development stage into a high-quality development stage.This change for China's construction machinery industry to bring more development opportunities at the same time,but also on China's construction machinery industry has put forward higher requirements.The metal structure inside the bucket wheel stacker boom is welded,and when its internal minor damage keeps accumulating to a dangerous threshold value,the structure will suddenly fracture,causing serious safety accidents.Therefore,how to effectively predict and evaluate the life of bucket wheel stacker arms and avoid unnecessary economic losses due to unreasonable equipment retirement life has become a top research priority.The fatigue life assessment and reliability analysis of the metal structure of the bucket wheel stacker-reclaimer boom requires first of all the preparation of the load spectrum of the structural hazard points.In this paper,we conduct a study on the DQL1500/1500-35 integral variable width cantilever bucket wheel stacker reclaimers to determine the hazard points of the metal structure of the boom based on empirical findings,and then obtain the load-time history data for a specific operating time period through field measurements.Using the self-programmed rainflow counting program to complete the data compression process on the test data,we can obtain the two-dimensional load spectrum of any level within the test time and complete the expansion of the twodimensional load spectrum to provide the basic data for fatigue life assessment and its reliability analysis.For the characteristic that the metal structure of the boom is a welded structure,the steps and methods for fatigue life assessment of the bucket wheel stacker boom metal structure are proposed.Since there are different life assessment methods for the presence or absence of initial cracks at the hazard points of the metal structure,this paper focuses on the fatigue life estimation method for metal structures with cracks.Based on the fracture mechanics method,the accumulated damage theory is used to calculate and evaluate the finite fatigue life of the bucket wheel stacker boom metal structure,establish the mathematical model for fatigue life estimation,and obtain the values of the key parameters in the mathematical model.Since the established mathematical model for life estimation cannot be directly applied to the data obtained from the rainflow counting procedure to obtain the results,Miner theory is used to realize the processing of the acquired load spectrum and then complete the life estimation.Based on fracture mechanics and reliability-related theories,the safety margin equation for the reliability of the boom metal structure is established according to its fatigue life mathematical model,and the values of key parameters are determined.Since there are many parameters and basic variables with unknown distribution information in the fatigue life reliability analysis of the bucket wheel stacker metal structure,and the limit state function is highly nonlinear,this paper adopts the primary second-order moment method to obtain the design check points,and proposes the important sampling method based on the Monte Carlo method to complete the fatigue reliability analysis. |
PDF Full Text Request