Vibration Characteristics Analysis And Crack Identification Of Pyramidal Truss Core Sandwich Beam

Lattice truss core sandwich structures have been widely used in areas such as aerospace,transportation,offshore drilling.Considering the work condition in these areas is very complex,and the workplace in these areas have a high requirement on mechanical properties of structures,so it is of great significance to investigate mechanics of sandwich structures.This paper for no injury and containing cast skin crack of pyramid type lattice truss core sandwich beam,vibration characteristics are researched from two aspects of theory and numerical simulation,the effect of truss core structure and crack parameters on natural frequency is researched.Nonlinear dynamics behaviors under the steady state vibration are analyzed.Regulations of nonlinear dynamic behaviors of pyramid type lattice truss core sandwich beam in different truss core structure and crack parameters are obtained.Basic contents are as follows:The free vibration and nonlinear forced vibration of the sandwich beam with pyramidal truss core are investigated.The zig-zag theory is used to derive the nonlinear equation of motion for the truss core sandwich beam.The natural frequencies of the sandwich beam are calculated and compared with the third-order shear deformation theory and simulation results.The effects of strut radius,inclination angle and core height on the natural frequencies of the sandwich beam are analyzed.Nonlinear frequency responses of the sandwich beam under different excitation amplitudes and different truss core structural parameters are analyzed.The results show that the natural frequencies of the sandwich beam increase and then decrease with increasing the strut radius or inclination angle.In addition,the structural parameters of the truss core have complicated effects on nonlinear responses of the sandwich beam.The vibration characteristics of the pyramidal truss core sandwich beam with a skin breathing crack are investigated.Based on the governing equation of intact sandwich beam,and assume the beam is uniform,the governing equation of cracked beam is derived by introducing the additional flexibility.The first order natural frequency of the sandwich beam is calculated and the theoretical result is compared to the result simulated by finite element method.The effects of the depth and location of the crack on the natural frequency are analyzed.The influences of the crack parameters on the nonlinear response of the sandwich beam are investigated by analyzing the frequency response curves,waveforms and phase diagrams under the steady state vibration.The results indicate that,under the super-harmonic excitation,the responses of the sandwich beam is sensitive to the crack parameters and the geometry characteristic of the phase diagrams can be used to identify the crack parameters.