Numerical Solution Of Critical Force And Stability Factor Of Telescopic Boom Of All-Terrain Crane

With the rapid development of society,industries such as wind power,chemical industry,construction,bridges,and nuclear power have more stringent requirements for aerial work.It poses greater challenges to the crane industry,especially the lifting weight and lifting height of all--terrain cranes.The telescopic booms of all-terrain cranes are getting longer and longer and the slenderness ratio is getting bigger and bigger.This causes the overall instability of the telescopic boom to occur before the strength breaks.In order to improve the force condition of the telescopic boom,related engineers and researchers have proposed to install a super-lifting device on the telescopic boom,thereby improving the lifting capacity of the crane telescopic boom.However,there is a lack of effective and accurate theoretical solution methods for the critical force of the telescopic boom belt overtaking device,and there is still a lack of research on the stability coefficient φ of the telescopic boom.In the thesis,we will study the stability of telescopic booms,the solution of critical forces and the stability coefficient φ.From shallow to deep,the telescopic boom belt super-lifting device is simplified to the n-step stepped columns plus single cable model and the n-step stepped columns plus double cables model for stability research.Finally,the stability coefficient φ in the overall stability is studied and discussed.The main research contents of the thesis is as follows:(1)The research object is the telescopic boom belt super-lifting single cable device of all--terrain cranes,the structure is simplified to the stepped columns plus a single cable model outside the luffing plane.Considering the nonguaranteed force of a single cable,the buckling characteristic equation and its recursive formula of the n-step stepped columns plus single cable model are deduced.The Levenberg-Marquardt optimization algorithm is used for the theoretical numerical solution of the critical force and length coefficients.ANSYS software is used for numerical solution of finite element simulation,and finally the error results are analyzed.The buckling characteristic equation and its recurrence formula of the stepped column plus single cable model derived in the thesis is proved to be correct,the theoretical numerical solution is also accurate.(2)On the basis of the previous research content,the research object is the telescopic boom belt super-lifting double cables device.Considering the nonguaranteed force of double cables,the buckling characteristic equation and its recursive formula of the n-step stepped columns plus double cables model are deduced.The Levenberg-Marquardt optimization algorithm is used to theoretically solve the critical force and length coefficients,error results are compared and analyzed.The buckling characteristic equation and its recursive formula of the stepped columns and double cables model are also proved to be correct,the theoretical numerical solution accuracy is still very high.By comparing the critical force and length coefficient of the telescopic boom plus super-lifting single cable and the telescopic boom plus super-lifting double cables.It is found that the critical force of the telescopic boom plus the super-lifting single cable is not as fast as the critical force of the telescopic boom plus the super-lifting double cables.The influence of the number of cables on the critical force of the higher-step telescopic boom will become weaker and weaker.(3)The telescopic boom is simplified as the stepped columns model,and the difference between its stability coefficient φ and the stability coefficient in GB/T3811-2008 is studied.The stability coefficient φ of the stepped column model is studied under the large slenderness ratio.It is found that the stability coefficient φ of the stepped columns model is always greater than that of the GB equal section straight column model.It is proved that the critical force that the stepped columns model can withstand is greater than that of the equal section straight column model under the same cross-sectional area and the same stress.The existing GB stability coefficient table is applicable to the equal section straight column model.When axial members such as the stepped column model are used for the global stability analysis,the method in the thesis is used to solve the new stability coefficient φ,and then conduct the overall stability analysis.