| Obtaining the stress time history data of horizontal boom tower crane is the basis for fatigue life evaluation.However,due to the influence of many factors,the change of stress with time is random and complex,so it is difficult to obtain.To solve this problem,this paper uses the combination of theoretical calculation and numerical simulation to obtain the stress time history data of horizontal arm tower crane,and applies it to the fatigue life evaluation.(1)Based on the spatial structure characteristics of horizontal boom tower crane,the lattice structure of tower boom is equivalent to solid web beam structure.The analytical expression of the internal force of the pull rod of the statically indeterminate double lifting point jib is derived by using the force method and Moore’s theorem.Based on the principle of d’Alembert,the expressions of cross-sectional internal force and operating parameters of boom tower body are derived.Based on the relationship between cross-sectional internal force and stress of boom tower given in relevant literature,the analytical expression of boom tower stress and operating parameters is derived.(2)Based on the characteristics of the stress analytical expression,the acquisition method of stress time history is determined.According to this method,the stress response output program is compiled by MATLAB.Select qtz630 prototype,set a variety of static conditions,and output the corresponding static stress through ANSYS simulation to verify the correctness of the stress response program under static conditions.Adams rigid flexible coupling model of qtz630 tower crane is established,and the variation law of operating parameters with time is simulated.A variety of dynamic working conditions are set,and the stress response results under corresponding working conditions are output through ANSYS simulation,which preliminarily verifies the rationality of the application of stress response program in fatigue life evaluation.(3)Based on the rain flow counting rules,the rain flow counting program in MATLAB is compiled to convert the random stress time history data into asymmetric simple harmonic alternating cycle.Based on the curve of Q235 B material specimen and considering the influence of stress concentration factor,the correction coefficient is introduced to determine the curve of the key structure of tower crane.Using Goodman diagram method,the relationship between the total number of stress cycles of key structures and the mean and amplitude of alternating stress is obtained.Based on the linear fatigue cumulative damage theory,the fatigue life estimation program is compiled.Through ANSYS simulation and MSC.Fatigue fatigue analysis software,the equivalent stress cycle times under the set loading conditions are output,and compared with the solution results in this paper,the correctness of the program method in this paper and the superiority compared with the simulation method are verified.(4)Experimental design and analysis based on qtz630 tower crane.The root of the tower is selected as the measuring point,a variety of dynamic conditions are set,and the stress response curve of the measuring point is output through the experimental test.Compared with the results of this paper,the correctness of the stress response program is verified.Five time periods are randomly selected,and the rain flow count results and fatigue damage values of each time period are output through experimental test.Compared with the results of this paper,the rationality of the application of stress response program in fatigue life evaluation is verified. |
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