Numerical Research On Dynamic Buckling Of Structures Under Axial Impacted Load

The stability of structure is a basic research task in solid mechanics all the time and is also one of the difficult problems which need to urgently solved in aerospace industry equipment now. The beam and cylindrical shell are the most common structural form, Compared with general structures, since for beams and cylindrical shells the geometrical equations are mostly simplified in forms, so the their buckling is playing an important role in structural stability, which has increased great development in the theories of structural stability. In this thesis, a theoretical analysis of the stability of slender beams and cylindrical shells under axial compression is presented in detail. At the same time, some attempts about the numerical arithmetic are carried out.In this paper, some major research directions in the stability theory of structure were introduced, as well as the progress of research in stability field. The advances in the research of dynamic elastic buckling of cylindrical shells under axial impact loading are reviewed comprehensively at first. The main comments are systematically remark on the dynamic buckling modes, dynamic buckling criterion and stress wave for the dynamic axial elastic buckling cylindrical shells, the achievements and advances in studies on dynamic buckling of structure subjected to impact loading.In this paper, it is considered that step loading propagates and progresses based on stress wave theory.lt is for the propagation and reflection of stress waves that the buckling of the structures takes place locally and grows entirely.Based on the nonlinear geometric equations, equilibrium relations, and the two plastic constitutive relations obtained respectively, the equations of the elastic cylindrical shell and beam motion are derived from Hamilton variational principle, we have tried to simulate the impact buckling processes of structures about beams and shells by using the programs of the LS-DYNA. The effects of initial geometric imperfections, boundary conditions, geometric dimensions and stress wave to the dynamic bucking behavior of cylindrical shell subjected to axial impact loading are discussed. Some typical time-history curves of impact loading and inertia forces are obtained in impact process. Analyse the process that the buckling modes are transformed from axisymmetic form to asymmetric form.Aspects of inertia effects in the buckling developing process are discussed.Numerical research show that the imperfection is not the necessary reason for the non-axisymmetric buckling mode. That is, the non-axisymmetric buckling mode is related to the impact load, the geometrical and material parameters of shells. The strain rate reverse andsome interesting results of stress wave propagation are also obtained by computer simulation. The simulation results are agreed with the experiments well.The dynamic buckling of elastic structures, such as beams and shells, when subjected to an axial impact at one end, is studied in the present paper based on the theory of stress wave propagation. Stress waves are bound to follow when structures are impacted along the axial direction.It is for the propagation of longitudinal waves that the buckling of the structures takes place and grows. In the course of the stress waves propagating, the buckling of structures appears locally. The method, in this paper, provides a solving way for similar problems.