Papers by Author: Lin Jing

Abstract: The dynamic compressive mechanical behavior of railway wheel steel at room temperature was investigated experimentally for strain rates up to ~2300/s, by using a split Hopkinson pressure bar (SHPB) apparatus. Experimental results indicate that the wheel steel exhibits an obvious strain rate-dependence; both yield strength and flow stress enhance with the increase of strain rate. Based on experimental data, an empirical dynamic constitutive model was used to describe the strain rate effect of wheel steel. These research results could provide reliable and accurate material constitutive parameters for wheel-rail impact simulations, to guide the design and assessment of the safety of the wheel-rail system.

Abstract: In this paper the structure response of quasi-statically loaded sandwich beams made of aluminum skins with open-cell aluminum foam cores is investigated experimentally. The experimental programme was designed to investigate the deformation and failure modes of sandwich beams, so a large number of experiments have been conducted, and the experimental results are reported and discussed systematically. It is found that sandwich beams under quasi-static punching loads can fail in several modes: face yield, face wrinkling, core shear, the bottom face fracture and interfacial failure between the core and the faces. Moreover, the effects of face thickness, cell size of foam material on the failure and deformation modes were discussed. The experimental results are of worth to optimum design of cellular metallic sandwich structures.

Abstract: The local effect of “softening” at the crack location can be simulated by an equivalent spring connecting the two segments of the beam. As modelling the crack, the non-perfectly rigid clamp is also simulated as a torsional spring of unknown stiffness. Combined with the Bernoulli-Euler theories of beam, the present model is applied to derive the characteristic equation of the cantilever beam under uncertain end conditions related to the crack parameters, namely, the location and the depth of the crack. Based on this characteristic equation, an accurate crack identification method is developed to identify the location and the depth of the crack by minimizing the difference between the analytical and experimental frequency values. The proposed approach is verified by two cantilever beam experiments under ideal boundary conditions and uncertain end conditions. It is found that the location and the depth of the crack can be worked out when at least three natural frequencies are known. For crack identification of the cantilever beam under uncertain end conditions, the identified crack location of the proposed approach is more accurate than the Narkis’ method. Furthermore, the crack depth can also be obtained by the present method.