Analysis Of The Structure Of The Telescopic Boom Of Aerial Work Platform Trucks

The telescopic boom of aerial work platform trucks is designed for manned use, which is an important part. The slider of the telescopic boom is an important part of the design process, which takes positive pressure and friction loading. Reasonable simplified model directly affects its bearing capacity and safety.Contact problem belongs to nonlinear boundary conditions. Contact problem takes more time than liner analysis when apply finite element analysis to solution. Convergence of numerical methods depends on contact stiffness and the complexity of the model and so on. In finite element analysis, DOF (Degrees Of Freedom) coupling for adjacent nodes belongs to liner analysis without convergence problems. In order to study the difference between these two methods and the alternate criteria in the calculation of the telescopic boom of hydraulic aerial cage, a contact model and a DOF coupling model for the telescopic boom are established in the finite element software ANSYS. The result shows DOF coupling analysis method is similar to the contact analysis in the simulation of the slider contact. But there is a great difference in the simulation of the hinged support because of the model difference. The contact stress with the change of load is nonlinear, but the equivalent stress of the structure with the change of load is linear. This is the necessary conditions of the substitution of these two models.Fatigue failure is the common failure form of structure. When the structure is starting and breaking or when the second boom stretch out or the telescopic boom lift which can cause structure vibration, the vibration can induce the strain amplitude and stress amplitude which can cause fatigue failure under the oversize strain amplitude or stress amplitude. Rayleigh damping coefficient need to be defined when apply transient dynamics analysis on the structure. By means of choosing the interesting frequency range, Rayleigh damping coefficient is obtained and discuss the effect of the selection of frequency range used to calculate the Rayleigh damping on structural vibration. The vibration states of impact load is obtained by means of dynamics analysis. The result of this transient dynamics analysis is the loading spectrum of the fatigue analysis with the fatigue analysis software FE-SAFE. The result shows there is huge difference with different methods of the fatigue calculation and the difference correction method of the mean stress. It should be very cautious when choose the fatigue algorithm. The liner relation between the fatigue life and the damping ratio is obtained by study the effect of the damping ratio on the fatigue life.For general materials there is more or less the initial defect and crack during the process of the manufacturing. So it is inappropriate to use the nominal stress method and the local stress-strain method to calculate the fatigue life. It is appropriate to use tolerable limit damage analysis to calculate the structural remaining life with initial defect or crack of the structure. By means of consulting the manual and related papers, obtain the stress intensity factor expression and the fracture toughness values, use Paris formula to calculate the remaining life of the upper cover plate of the telescopic boom with initial crack under the cyclic loading and discuss the effect of temperature on the remaining life.