Analysis on Fracture Behavior and Optimization of Beam-Column Connections with Expanded Flanges of Steel Frames

In this study, the parameters of concave expanded flanges of beam-column connections of steel frames are optimized based on the effects of different sizes of concave expanded flanges on the fracture performance. Firstly, two beam-column connection models with concave expanded flanges are built and analyzed under cyclic loads, which have the same conditions as the specimens during the previous test. Secondly, the validity of the numerical simulation models is verified through analyzing the hysteretic behaviors of the connections with concave expanded flanges, such as the plastic hinge position, the hysteresis curves, the skeleton curves, the stiffness degradation, the ductility coefficient, and the energy dissipation capacity. Thirdly, in order to comprehensively evaluate the fracture status of metal materials, the relevant fracture evaluation index (the stress triaxiality ratio (Rσ), plastic equivalent strain index (PI), and cracking index (RI)) are introduced. Afterwards, eighteen numerical simulation models with differences in the length la of the reinforced section, the length lb of the transition section, and the width c of the reinforced section were analyzed. Finally, the parameters of the concave expanded flanges of the beam-column connections are optimized based on the results of the three fracture evaluation index.

Analysis of Hardness Maps on Aluminium Alloy Processed by ECAP

Microhardness and hardness maps have been measured in different sections of samples processed by Equal Channel Angular Pressing (ECAP). In order to investigate the homogeneity of the hardening induced by ECAP as a function of deformation, the hardness maps have been based on samples deformed at different strains (after one and four passes). After one pass the specimen’s outer side, both on its cross and longitudinal planes, is less hard than all other zones. Moreover, after 4 passes via route Bc, the hardening induced on the sample cross section is lower at the surface than in the central area of the billet. The reduced hardness regions are compared to the distributions of plastic equivalent strain generated by finite element analysis.

HPT-Deformation of Copper and Nickel Single Crystals

Copper and nickel single crystals of high purity with a crystallographic orientation, (001) and (111) respectively, were deformed by applying high pressure torsion (HPT) at room temperature. Special interest was devoted to the structural evolution of the material, which was characterized by electron backscatter diffraction (EBSD) and X-ray texture analysis as well. In addition back scatter electron investigations were applied to characterize shape and size of the new formed structure. Furthermore the study is focused on the micro structural and micro textural evolution that lead to the increase of missorientation angle with increasing plastic deformation. We observed an increasing fragmentation of the structure with increasing plastic equivalent strain up to a level where the grain size is saturated. The saturation could be traced back to dynamical recovery and recrystallisation during the deformation process that is depending on the purity of the material.