Theoretical Analysis And Dynamic Simulation Of Nonlinear Stability For Combined Lattice Boom With Variable Cross Section

Due to the demand in the fields of port,marine equipment,the third generation of nuclear power,etc.and for large-scale lifting operation,the load capacity of a crane tends to be heavier,but itself tends to be lighter,also it will have the features of larger space,intelligent control technology and higher efficiency,however,lean production cannot be separated from high quality,high efficiency,high safety performance of the handling system,the application of high-strength steel not only makes crane boom structure more lightweight but also makes the flexibility of structure increased and geometry deformation under heavy load nonlinear.As a result,if the linear theory based on the assumption of small displacement is still used to analyze the stability of boom structure,the results will deviates from actual stress state which will cause an unsafe or incorrect statistic,and the practical design theory is helpful to maintain the balance between structural strength and stability.Secondly,in the heavy lifting process,if the effective load is unexpectedly lost,the structure will produce violent shock and vibration because the potential energy has been released by the moment which is caused for the flexibility of boom,gravity of weight and tension of hoist rope in the extreme large angle condition,that is to bring new challenges to the anti-backward-tilting device and system security of the boom.Moreover,it is of practical significance to explore how to accurately simulate the reverse impact load for the real condition and to avoid exaggerating or reducing the dynamic response of the structure.In this paper,a large slenderness ratio combined lattice boom of a certain type of crane is selected as the research object.The strength,stiffness and stability(global stability and local stability)of the boom system are checked based on different methods and doctrines,and the key is the nonlinear stability,by introducing the concept of generalized margin,merits and demerits of theoretical system of different methods are evaluated and the optimal theory and method are also obtained which are verified through ANSYS,in the end,the simulation points are discussed in detail.Then,with virtual prototyping technology as a means,combined ANSYS with ADAMS to build the rigid-flexible coupled model of boom system,and applied the multi-body dynamics analysis method to conduct theoretical modeling and numerical simulation of the unexpectedly loss of the effective load,the dynamic response of the structure and force characteristics of the anti-backward-tilting device under the action of transient excitations are studied,in addition,according to the principle of single control variable,tapping the influence law of the dynamic characteristics of the boom deeply of various design factors(different unloading time,lifting ratio and lifting acceleration time)which can have important reference value for structural design improvements,type selection and reasonable arrangement of anti-backward-tilting device.