Experimental And Theoretic Studies On Dynamic Buckling Of Perfect Elastic Columns Under Axial Impact

Investigations on dynamic buckling of columns have important applications in many fields, such as aviation, spacecraft, traffic and structural engineering. Recently, elastic-plastic buckling of columns under pulse loads is an active subject in solid mechanics. The experimental and theoretic studies on the bifurcation of perfect elastic columns under axial impact are reported in this paper. The main results are summarized in the following several aspects:1 , Experiments on the bifurcation of perfect elastic columns with 460mm length under axial impact by KDQ-2 air driver were completed. During the propagation of stress wave, the time-history curves of strain on two symmetric surfaces of special positions were recorded. The buckling load and buckling length of specimens canbe abstained from the strain amplitude and bifurcation time on the two curves. The results of the experiments indicate that: the propagation of stress wave play an important role in the dynamic buckling of elastic column under axial impact, the buckling length is shorter with the increase of impact velocity and the buckling load P = 8.78P￡, in that PE = x2El/x2cr, xcr = ctcr.2^ The qualitative analysis for elastic column under axial impact was completed from the theory of Bernoulli-Euler beam. According to the dynamic parameter /, there are three cases: stability (/>0), neutral stability (/ = 0) and instability (/<0).4When b<0, - — < ￡ < 0, the solution of the Bernoulli-Euler beamequation is dynamic buckling solution.3> A double parameter (y,a) equation was derived according to qualification of the equations have nontrivial solution satisfying the boundary conditions from the theory of Bernoulli-Euler beam. From that, the systematic theoretic analyses on three different boundary conditions were completed. The results of theoretic analysis show the dynamic buckling critical load P of hinged-hinged > clamped-clamped and hinged-clamped beams compare to PE are K 1(K 5 .4> Two theoretic analysis models were given to analyze elastic column buckling under axial impact considering the propagation of axial stress wave. When the front of stress wave is granted as fixed, the dynamic buckling loads P = IOPE.5> The results of experiments and theoretic analyses show that the front of stress wave can be granted as fixed. When impact load is known, the buckling critical length is /