Axisymmetric buckling of cylindrical tubes has been expected to be used for the resistance to impact forces. We have found AZ31 magnesium alloy tubes could show axisymmetric buckling at temperatures higher than 473K, which corresponds to the sharp rise in the tensile ductility of the alloy with increasing temperature. Elastic deformation of a compressed tube before the onset of the elastic instability is examined by finite element analysis.

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Axisymmetric buckling of axially compressed cylindrical tubes was observed in experiments using aluminum tubes, and the result was compared with the predictions of the elastic-plastic large deformation FEM analysis with ANSYS. It is shown that the calculated length of the buckling wave is too long if small displacement in the radius is not applied to the end of tube. The supporting condition of tube's edges was experimentally examined, and it was found that the condition did not significantly alter the buckling behaviour.

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Shape recovery of indentations by steel spheres was observed in a nickel-titanium shape memory alloy. The diameter, depth and curvature of indentations before and after shape memory recovery were measured with a laser microscope. A parameter representing the fraction of recovery due to shape memory effect was defined, and the variation of the parameter with the change of indentation force and the diameter of spheres were measured. It was found that the strain beneath the surface of an indentation can be estimated through the empirical relation, 0.2R/R_I, where R is the radius of the indentation and R_I that of the sphere.

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In this study, material parameters of inelastic constitutive model are identified by using the steepest decent method (SDM) and random search (RS). For parameter identification the difference between the experimental results and the simulated data is minimized. Both of the two methods show good adaptability for cyclic plasticity experiment of pure titanium. A random number generator including multi-pseudo-random number generators is used in RS and the dependency of number of pseudo-random number generators is confirmed.

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Relations of aerodynamic sound and vortex motions in a flow separated from a fence with vortex generators were discussed by velocity measurements and simultaneous measurements of aerodynamic sound and fluctuating static-pressure. The vortex generators were attached to the fence to introduce three-dimensional perturbations into the separated shear flow. Sound source terms of Ribner's Dilatation theory were calculated with measured fluctuating static-pressure, and integral of coherent output power of the sound source term was discussed to determine flow regions contributing to aerodynamic sound generation. The results suggest that the three-dimensional perturbations reduce aerodynamic sound in relatively low frequency band and the effect of the aerodynamic sound reduction was detected in the separated shear flow near the fence by the integral of coherent output power of the sound source term.

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