This paper presents an experimentai and numerical study of the bird strike on a 2024-T3 aluminum double plate.The experiments are carried out at a desired impact velocity of 150 m/s.The explicit finite element software PAM-CRASH is used to Simulate the birdstrike experiments,and a coupled SPH-FE method is adopted,where the bird is modeled using the SPH method with the Mur naghan EOS and the struc ture is meshed with finite elemen ts.The mat erial parame ters are identified by an optimization process,and the Simula ted dynamic responses of bird strike are compared with experimentai measurements to verify the numerical model.The displacement and strain of the plate as well as the final deformation and damage show good agreemen t bet ween the simulation and the experimental resul ts.It suggests that the coupled SPH-FE met hod can provide an effec tive tool in designing bird-strike-resista nt aircraft component.
In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with that of coarse grained material. The results indicate that the flow stress of ultrafine grained aluminum displays enhanced sensitivity to temperature. The reduction in activation volume is suggested to be the major reason for the enhanced temperature sensitivity as grain size is refined into the sub-micrometer regime. Finally, a phenomenological constitutive model is proposed to describe the post-yield response of ultrafine grained aluminum.
To increase the detectability of split Hopkinson pressure bar(SHPB)of low-impedance materials,modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal,and weak signals were further amplified by semiconductor strain gauges.Experiments on soft rubbers and cushioning foam materials were carried out.In order to analyze the accuracy of the experimental results,the stress equilibrium issues involved in the assumptions of SHPB were investigated.First,by way of re-constructing loading process of incident wave,the stress-strain curve was obtained,along with the stress equilibrium ratio of specimen.Secondly,the influences on the accuracy of stressstrain curves were investigated through the elastic modulus comparisons.And the results illustrate that the bilinear incident wave from experiments can ensure the stress equilibrium deformation of specimen after 2normalized times,much sooner than ramp incident waves.Moreover,it even facilitates specimen deformation with a constant strain rate.The results confirm that the detectability of the modified SHPB can be down to tens kPa with enough accuracy level.
