Design Of Large Tonnage Railway Crane’s Pear-shaped Telescopic Boom And Research Of Its Nonlinear Problem

The telescopic boom is a critical part of the railway crane, when it works, external loads directly apply on it, so reasonable calculation or not is very important.Pear-shaped section telescopic boom represents the most advanced manufacturing and process level of the crane. At the same time,it fits the large tonnage and lifting moment development trend of boom.Exploring of its design and calculation method,simulation of the stress distribution on boom and sliders under real contact condition both have certain practical significance.This paper,from the enterprise user view.combines the C#.NET’s friendly interface and MATLAB’s calculation ability for large and complex data.Then design and calculation software of boom is successfully programmed.This software can efficiently calculate boom’s length,screen the dangerous conditions,calculate external load under the dangerous condition,select and calculate the material. Thus,this software has the advantages of simple operation and high efficiency.According to the calculation result that the above interface gives,entity model of the pear-shaped section boom is established in software ABAQUS.Then contact interaction between boom and sliders is set reasonably.In order to improve the convergence of the contact analysis.small grid is applied to the contact area.Besides,hinge interaction between boom and oil cylinder is considered in the finite model.Specificially, Reference point and the surrounding area is connected with moving coupling method,then hinge interaction is used to connect the reference points.To improve the contact nonlinear convergence furtherly,external load is applied step by step.After several times of iterative compution,ABAQUS gives the contact finite result of the pear-shaped section boom.The result shows that,for the pear-shaped section boom:(1) area in the bottom of lower groove plate that contacts with the lip sliders is easy to has the stress concentration; (2) Upper groove plate’s inclined plate that contacts with sliders is easy to has the stress concentration. As for the sliders:(1) stress distribution on sliders next to the basic jib lip is different in two different conditions.In dangerous condition 1, stress distribution on the sliders next to the second jib lip presents a "large in front(+Z),small in behind(-Z)" situation. In dangerous condition 2, the above sliders’stress distribution has the opposite "small in front(+Z),large in behind(-Z)"situation. (2) The lip corner of the slider next to the basic jib, circular transition zone of the slider tail next to the seconde jib are easy to have the stress concentration. Stress here tends to break the material yield limit,then casuses plastic deformation.Thus,study on sliders’stress distribution in elastoplastic range is more reasonable.Plastic problem is one of the three nonlinear problems in structure mechanics.The key of analyzing this problem is to set the elastoplastic constitutive model reasonably.In this paper,sliders’ local plastic deformation belongs to the small strain preoblems. Based on the above sliders’ elastic contact analysis,this paper uses simplified bilinear stress-strain curve to describe material’s tensile stress-strain data,uses isotropic hardening model to describe the material’s further reaction to the change of load after plastic deformation. After several times of iteractive computations,ABAQUS gives the sliders’ stress distribution in elastoplastic range.Sliders’ elastoplastic finite element result shows that,plastic material’s strengthening effect has reduced the sliders’stress greatly.When plastic deformation occurs,stress increases slowly.However,compared with the elastic finite element result, plastic deformation does not influent stress distribution on boom too much.The effect even can be ignored.Besides,the plastic deformation area is very small,this shows that the sliders can still work.as a result,this can also improve the material’s utilization rate.In order to make the finite element simulation more practical, this paper optimizes the boom palte thickness with considering contact nonlinear and material nonlinear.Samples elected by orthogonal test have the characteristics of uniform dispersion and neat comparability.As a result,this method can not only minimizes the computation cost but also ensure the accuracy of computation result. Then,LM-BP network is used to train the above orthogonal test samples assisted with ABAQUS. After 39 times of study, LM-BP neural network achieves the training accuracy. GA is used to find the best combination of palte thickness in the nonlinear relationship. For the convenience of manufacturing, the design variables (telescopic boom thickness combination) of the optimized design are rounded.The rounded results are verified in ABAQUS:Optimization of pear-shaped section boom based on LM-BP network and GA is effective and feasible.