| In recent years, such accidents like goods or arm support falling frequently occur due to mechanical failure in spare parts of crane. Under accident condition, mechanical system will suffer strong shock and vibration owing to short braking time and fiercely-changed condition. This may have a devastating effect on structure. At present, study on the process of braking in normal circumstances has been comparatively mature. However, researches of these under accident condition t are very scarce. So it is absolutely necessary to analysis the dynamic properties of braking process under accident condition.This thesis takes MQ4599portal crane'hoisting mechanism as research object, Combine MATLAB matrix method and ANSYS finite element method to analysis the dynamic properties of braking process under accident condition. The focal discussion point has been put on the during time, distance and dynamic load of the braking process under accident condition. Research on the elastic vibration rule in this situation. Extract representative displacement of arm support change with time, then calculate the dynamic stress and strain response of the system.The thesis consists of the following parts:(1)Take the whole hoisting mechanism transfer system of MQ4599portal crane as research object, analyze the braking process of the lifting transmission system, and calculate the time and distance and train of hoisting cable in different condition.(2) Simplify the real system under some reasonable assumptions, using less degree of freedom model method to establish dynamic model with three degrees and weights. By dividing it into two phases, the thesis makes a detailed analysis of elastic vibration rule under accident condition in braking process. Calculate the moving differential equation with MATLAB, Select appropriate control condition and deduce the response of displacement and the velocity of ledge t and the goods in every phase, analyze factors which affect the system vibration.(3)The during time and distance of the braking process differs in different accident condition, so portal crane system has different dynamic incentive stress response. Analysis stress response in ANSYS which obtains the dynamic response results including simulation of dynamics stress and displacement and curve of dynamic stress of representative nodes. Analyzes the influences of the braking process under accident condition to the structure. |
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