Papers by Keyword: Surface Slip

Abstract: Steel-concrete composite box beams have been widely used in high rise buildings and long-span bridge structures. But so far, almost all researches have been aimed at the static behavior of the composite beams and dynamic behavior of steel and concrete composite beams have been rarely studied. In this paper, by using general finite element program ANSYS to analyze the dynamic performance of the composite box beam under different geometric parameters. Research is focused on the slip stiffness、width-to-thickness ratio、depth-span ratio and the height ratio of cross section to the vibration characteristics of composite box beam. The results indicate that these factors affect the seismic dynamic response of steel-concrete composite box beams most and they should be controlled according to different situations in seismic design stage.

Abstract: Slip localization is often observed in metallic polycrystals after cyclic deformation (persistent slip bands) or pre-irradiation followed by tensile deformation (channels). To evaluate its influence on surface relief formation and grain boundary microcrack nucleation, crystalline finite element (FE) computations are carried out using microstructure inputs (slip band aspect ratio/spacing). Slip bands (low critical resolved shear stress (CRSS)) are embedded in small elastic aggregates. Slip band aspect ratio and neighboring grain orientations influence strongly the surface slips. But only a weak effect of slip band CRSS, spacing and grain boundary orientation is observed. Analytical formulae are deduced which allow an easy prediction of the surface and bulk slips. The computed slips are in agreement with experimental measures (AFM/TEM measures on pre-irradiated austenitic stainless steels and nickel, copper and precipitate-strengthened alloy subjected to cyclic loading). Grain boundary normal stresses are computed for various materials and loading conditions. A square root dependence with respect to the distance to the slip band corner is found similarly to the pile-up stress field. But the equivalent stress intensity factor is considerably lower. Analytical formulae are proposed for predicting the grain boundary normal stress field depending on the microstructure lengths. Finally, an energy balance criterion is applied using the equivalent elastic energy release rate and the surface/grain boundary energies. The predicted macroscopic stresses for microcrack nucleation are compared to the experimental ones.