Research On The Stability Of Telescopic Boom Of All-terrain Crane

With the rapid development of the national economy,China's construction machinery has also made considerable progress.All-terrain cranes have short-distance,high-efficiency transition capability and are capable of performing in all major engineering fields.As the customer's requirements for height and weight are increased,the full extension of the telescopic boom becomes longer.At the same time,the stability becomes more and more important in the design of telescopic boom.The section of the telescopic boom determines the moment of inertia of the section directly.The moment of inertia of the section affects the critical load of telescopic boom.Therefore,it is necessary to study the influence of the cross-section dimension of telescopic boom on the moment of inertia,and then to study the influence and sensitivity of the critical load.Taking U-section as an example,the analysis results show that when the material,support method and length of the telescopic boom are constant,the buckling critical force of telescopic boom decreases with the increase of bending radius?R₀?,but increases with the increase of other cross-sectional dimensions.Sensitivity analysis indicates that the most sensitive dimemsion is the width of the basic boom section?d₀?,followed by height of the basic boom section?H₀?,and the lowest sensitive dimemsion is thickness(w₅₂)of the lower cover plate of the distal boom?telescopic head?.In order to improve the stability of the telescopic boom,it has become a common trend to install super-lift system on the telescopic boom of a large or super large all-terrain crane.However,in the China Crane Design Specification GB/T3811-2008,there are no design specifications for the boom sections is more than 5 and super-lift system.Therefore,it is of great significance to study the influence of super-lift system on the buckling critical load of the telescopic boom.By studying the influence of super-lift system on the buckling critical load of the telescopic boom,it is found that the critical lifting weight increases first and then decreases with the increase of the angle???of the super-lifting brace.The critical lifting weight first decreases slightly with the increase of the length of the super-lifting strut?H?,and then increases rapidly.The critical lifting weight is no longer increases continuously and obviously when the length?H?of the super-lifting strut reaches a certain length.The critical lifting weight increases with the distance?L?where from the hinged point of the super-lifting pole with the telescopic boom to the hinged point of the basic boom,which means that the most advantageous location to install the super-lifting pole is at the end of the basic boom.On this basis,the shortcomings of existing super-lifting system are analyzed,and a new proposal is proposed to make up for the shortcomings of existing super-lifting system.The validity of the proposal is verified by the finite element method.As the telescopic boom becomes longer,it will produce initial deflection due to its own weight.And it is inevitable to produces initial defects during production,manufacture,transportation,etc.Therefore,based on ANSYS Workbench co-simulation platform,the initial defects are introduced to the telescopic boom.Nonlinear buckling analysis results show that the critical load of telescopic boom will decrease further with the increase of the defect factor,which fully explains that it is necessary to consider the initial structural defect.