Damage Evaluation Of Overhead Traveling Crane's Girder And Fault Diagnosis Of Gearbox Based On Dynamic Test

At present, most of overhead travlling cranes, used in our country, are produced beforethe1980s. They are servicing with the exception of that a few are scraped. Aging has becomean increasingly important issue for the serviced and the risk is becoming greater and greater.However, with the development of chinese construction industry and the deepening of thereform, higher request in practice is proposed for the bearing capacity and reliability ofoverhead travlling cranes. So, how to scientific evaluate the real state on girder of overheadtravlling crane is the key to avoid and control catastrophe failure in enterprise production.Meanwhile, gear reducer has a big transmission torque and poor working conditions, etc, itcauses reducer become the part of the most prone to go wrong. So reducer's running statedirectly affects crane's normal work. In order to assess the reliability of overhead travllingcrane so as to make scientific decision about normal use, downgraded or scraped and so on,dynamic evaluation is played in the thesis.The main research work is conducted as follows:(1) Research on the girder finite element model updating techniques.Targeting the difference between the finite element model and real girder structure, thetraditional theory of finite element model updating is analysed and a few kinds of methods,commonly used, are compared.Then the method, based on sensitivity analysis, is proposed toupdate the girder finite element model of overhead travlling crane. In the process of modeling,modification of the objective function is on the basis of the measured frequency. Aftermodifying the structural model, optimized calculating parameters are obtained, then themodel is updated. The updated finite element model reflected actual dynamic characteristicsin an even better fashion. It lays solid foundation for further analysis.(2) Damage analysis on modal dynamic fingerprint of the girder.The dynamic fingerprints, based on frequency variation, mode variation, curvature modevariation, flexibility variation curvature and stiffness variation index, are introduced and thecomputational method of dynamic fingerprints are expounded. These indexes are used on anoverhead travlling crane to compare damage identification capability. It is found that theperformance of curvature mode variation fingerprint and stiffness variation index fingerprintis the best when those dynamic fingerprints are used to locate damage. Then curvature modevariation fingerprint and stiffness variation index fingerprint are used to calculate damagelevels and the results show stiffness variation index fingerprint has a more accurateidentification capability. So, stiffness variation index is an excellent fingerprint. (3) Damage evaluation of crane's girder based on support vector machine.The algorithm of support vector machine(SVM) and the principle of the kernel functionare analysed in theory. Then SVIs are input into SVM and appropriate kernel function isselected. With test, the best parameters are calculated to identify gieder damage of crane.Tofurther improve the identification accuracy and convergence rate, particle swam optimization(PSO) algorithm is introduced and improved. The improved PSO is used to optimize theparameters of least square support vector machine(LSSVM). After that, the method is used toidentify girder damage of overhead travlling crane.The result demonstrates IPSO-LSSVM hasbetter identifition ability than traditional classification algorithm.(4) Research on the application of EMD and ARMA bi-cepstrum fault diagnosismethod in gearbox of overhead traveling crane.Basic principle of fault diagnosis about crane gear reducer is concisely expounded andpossible characteristic frequency when gear and rolling bearing occurs fault is summarized.Targeting the time varying of signals measured on the surface of gear reducer, empirical modedecomposition(EMD) is occupied to modulate the signals; auto-regressive movingaverage(ARMA) method,which has higher accuracy and better applicable condition, is usedto establish model for the signal principal components of intrinsic mode functions from theEMD; then parametric bi-cepstrum estimation is implemented and accurate fault informationsare extracted. The method is applied in fault diagnosis of crane gear reducer, the resultsdemonstrate that: the presented method, combining EMD with parametric bi-cepstrum ofARMA model, can obtain the fault quefrency accurately to determine the actual conditions ofcrane gear reducer, and it is an effective health assessment method.(5) Dynamics test for girder and gearbox of overhead traveling craneThrough the modal test for the girder metal frame, fading signals of exciter test on girdermetal frame are collected. Frequency response analysis is conducted for the collected signalsand the informations of the first three modes are obtained with structural modal parameter id-entification method.This provides foundation and support for updating simulation model ofgirder metal frame.Otherwise, with fault diagnosis test on gear reducer of gieder lifting mech-anism, vibration signals are collected from reducer. This provides condition for deteminingthe failure causes or the fault nature.