Analysis And Formula Fitting On Contact Stress Of Bottom Slide Block Of The U-shaped Telescopic Boom

With the development of economy and science and the pursuit of operation efficiency, large cranes get rapid development. U-shaped telescopic boom has been widely used in large cranes because of its compact structure, good performance against tortuosity and large space rigidity. Each section of the telescopic boom has the ability of load transmitting and stretching through the supporting and guiding of the slide block. It is complicated and important of the stress condition in the contact area of telescopic boom where the dangerous section of telescopic boom also lies.It is difficult to calculate the contact stress of bottom slider block by using analytic algorithm because of its nonlinearity. Numerical method is also resource-intensive and time-consuming. Therefore, it is necessary to research the stress variation trend of the contact area of the U-shaped telescopic boom and do multivariate fitting of its data in order to get the stress distributing rule and fitting formula of the contact area, which can provide reference for project practical problems. The contents are as follows:(1) This paper introduces the finite element contact theory and the application in ANSYS. It also analyses the influence the different sets of ANSYS contact parameters have on the results, especially the influence of the set of normal penalty stiffness and penetration tolerance. The reasonable contact parameters are also selected.(2) The paper analyzes the structure and the commonly used section shape of telescopic boom. Appropriate elements, boundary conditions and contact relationship is defined, the reasonable simplified finite element model of U-shaped telescopic boom is set up.(3) The paper analyzes and simplifies the parameters which influence the stress of bottom slide block contact area of the U-shaped telescopic boom. Contact stress data is computed under the change of load and slide block parameters by making use of the simulation of MATLAB and ANSYS. The change rule of contact stress is also got.(4) Multivariate non-linear regression is proceeded according to the contact stress of the bottom slide block under the load change of a crane. The fitting formula is got under different working conditions by using Least Square Method. The paper selects Fy, Fz,and M under a variety of working conditions and compare them through the finite element calculation results and fitting formula calculation results. It verifies the accuracy of the formula, which shows small errors and significant fitting effect. The calculation results of boom intensity theory and finite element are compared.