| Bucket-wheel stacker-reclaimer is a track-type loading and unloading equipment that integrates stacking and taking.It is often used in bulk material stacking and conveying operations in ports,mines,cement and other industries.The pitch mechanism is not only the important movement mechanism of the bucket wheel stacker and reclaimer,but also the main support.However,the traditional design method is often to separate the mechanism and structure.While optimizing the design of the organization,choosing a reasonable structure has important economic value.This paper takes Hunan Long Heavy Machinery’s bucket wheel stacker and reclaimer DQL500/800 32.5 as the research object.It not only comprehensively considers the lightweight problem of mechanism-structure integration,but also considers the economic benefits in the production process of construction machinery..The specific research content is as follows:(1)Analysis of load and working condition combination of the pitch mechanism.The main components of the pitching mechanism are introduced,and the weight of the pitching mechanism of the bucket wheel stacker-reclaimer,the force of the bucket wheel on the boom,the bucket wheel digging force and cutting force,the conveying system and the material action on the conveyor belt are analyzed and calculated.The force on the forearm,the rest of the transmission system are all carried on the forearm,and the force of the counterweight boom.The working conditions and load combinations are explained.(2)The motion analysis and statics analysis of the pitch mechanism are carried out.Use the analytical method to establish a closed vector equation for the simplified model of the pitch mechanism,derive the mathematical expressions of the remaining rod length and the angle between the rods based on the known quantities,and perform motion analysis calculations on the position,motion speed and acceleration of each rod’s hinge point,and Analyze and calculate the driving force of the hydraulic cylinder and the force of each rod.(3)Carry out mechanism-structure integrated optimization design for the pitch mechanism.Parameterize the mechanism part and structure part,and also parameterize other important parameters such as connecting rods,loads and kinematic pairs.The constraint function is established based on the connecting rod boundary conditions,stability conditions and strength conditions,and the objective function is established with the minimum total mass of the pitch mechanism as the objective function.At the same time,considering that profiles are often used as the main support in construction machinery,a continuous step function of the mapping relationship between discrete profile variables and continuous variables is constructed.By comparing the design variables before and after optimization,the horizontal center of gravity displacement of the pitch mechanism,the angular acceleration of the bucket wheel,the driving force of the hydraulic cylinder,the force and the maximum stress of each rod,the analysis shows that the pitch mechanism is not only lightweight,but also various performances are obtained.Various degrees of optimization have been implemented.(4)Perform finite element verification on the optimized pitch mechanism.By analyzing the equivalent stress cloud diagram and the total deformation cloud diagram of the different working conditions of the pitch mechanism,it is verified that the strength and stiffness conditions of the pitch mechanism meet the design requirements.Through the comparative analysis of the first 20-order vibration natural frequency of the pitch mechanism and the main working excitation frequency,it is found that the working frequency of the bucket wheel and the small reversing drum is close to the natural frequency of the structure,and improved measures to avoid resonance are proposed. |
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