Research On Maintenance Decision Of Casting Crane Metal Structure Based On Safety Evaluation

During the service of the metal structure of the casting crane,the i MPact of the loading,running,starting,braking,nibbling and other working conditions of the cart on the fatigue performance of the metal structure will become more obvious.Moreover,the harsh working environment of high temperature and high dust of the casting crane also brings great uncertainty to its operation.Faced with the problem of the degradation of the metal structure of the casting crane,most of the factories currently use daily inspection and regular maintenance methods.However,these methods do not well grasp the degraded performance characteristics of metal structures.Frequent inspections and regular replacement maintenance will not only cause a waste of maintenance resources,but also cause frequent shutdowns.Therefore,it is of great engineering significance to determine the degradation characteristics of metal structure performance and formulate a reasonable maintenance plan in combination with the degradation characteristics.In this paper,the goal is to build a casting crane metal structure maintenance decision-making framework,and take the fatigue crack maintenance decision as an example to study the casting crane metal structure group maintenance decision-making method,the fatigue crack propagation life prediction method,the single-component fatigue crack maintenance decision method and Multi-component fatigue crack maintenance decision-making method.The main research contents and conclusions of this article are as follows:(1)A framework for the decision-making method of the metal structure maintenance of the casting crane is constructed.Through the analysis of the failure mode of the metal structure of the casting crane and its i MPact,the important and non-important components of the metal structure are determined,and the maintenance method of the non-essential components is defined as daily inspection.The evaluation indexes of important components are analyzed,and the evaluation indexes of metal structures are determined as corrosion,strength,stiffness,cracks and wear.Integrating wear and corrosion,according to the performance degradation characteristics of corrosion,strength,stiffness,and cracks,a corresponding physical degradation physical model and corresponding failure probability density function were constructed,and a single-component maintenance decision model was constructed using the minimum cost rate theory.(2)Fatigue life analysis of cast crane metal structure.Simplify the metal structure into a two-degree-of-freedom two-mass system to construct the dynamic equation of the lifting process.Use Matlab programming to solve the tension of the steel rope under different lifting speeds and different parts.The three-dimensional shell element finite element modeling of the cast iron crane metal structure main beam.The transient dynamic analysis of the main beam of the metal structure of the casting crane at different lifting positions and different lifting speeds is carried out to obtain the stress time history curve of the dangerous points at the end and midspan.The rain flow counting method is used to obtain the stress amplitude of the time history stress of the dangerous point,and the equivalent stress amplitude is obtained according to the root mean square equivalent method,which provides the initial equivalent stress amplitude for the prediction of fatigue crack growth life.The modified fatigue damage accumulation model was used to analyze the fatigue crack initiation life of the dangerous point at the end of the main beam of the casting crane.The fatigue crack initiation life degradation model of the component was established,and a patrol inspection plan based on the remaining life was developed.A single main beam solid shell coupling model is established,and the fatigue crack growth life at the welding toe of the connecting end of the diaphragm and the lower cover plate is obtained based on XFEM(Expanded Finite Element).The research shows that when hoisting at the same location,the tension and dynamic load coefficient of the wire rope increase with the increase of the lifting speed,and the tension of the wire rope at 10.2m/min in the mid-span is the largest.At the same hoisting speed,the closer the hoisting part is to the dangerous point of the metal structure,the greater the stress.(3)Prediction of fatigue crack growth life of metal structure of casting crane based on fusion model.Discrete the Paris formula and the improved two-parameter exponential formula,and based on the Bayes principle,the discretized Paris and the improved two-parameter exponential recursive formula are respectively combined with the particle filter,extended Kalman filter,and unscented Kalman filter algorithm.Fusion forms a fusion model.According to the fatigue crack growth life curve,the fusion regression model was used to estimate the state parameters of the Paris recursive formula and the improved two-parameter exponential formula.After obtaining the estimated parameters,the crack life was predicted according to the discretized recursive formula.Finally,the algorithm is verified using the simulation results of the crack propagation of the metal structure of the casting crane.Studies have shown that the fusion model can be used to predict fatigue crack growth life.When the crack growth rate is relatively slow and the crack length is short(that is,the first stage of crack growth),the result obtained by using the fusion model of the unscented Kalman filter algorithm and the Paris formula is superior to the fusion model of the particle filter algorithm and the extended Kalman filter algorithm.;When the crack growth rate is faster and the crack length is longer(that is,the second stage crack growth),the result obtained by using the particle filter algorithm and the Paris formula fusion model is better than the fusion of the unscented Kalman filter algorithm and the extended Kalman filter algorithm model.(4)Casting crane metal structure single component and group maintenance decision.Based on the Gamma degradation process,the probability density function of the crack propagation process is constructed.The Weibull CDF function is used to replace the reliability function and failure rate function of the Gamma degradation process,which simplifies the calculation process of the reliability function and failure rate function.A single-component maintenance decision-making model and a multi-component group maintenance model based on the minimum cost rate are constructed;a punishment model for maintenance time changes is established,and the punishment model is minimized to obtain the optimal time for group maintenance and a group maintenance decision method is formed.Finally,ten randomly generated examples are used to verify the applicability of the group maintenance decisionmaking method in casting crane metal structure maintenance decision-making.