Papers by Keyword: Inhomogeneous Deformation

Abstract: Depending on the composition and structure of metallic glasses cells with the dimensions in the range from tenths nanometers to tenths micrometers were observed on the ductile fracture surface. The variation in dimple size was compared with the serrations presented on the loading curve at the nanoindentation of the metallic glasses with different compositions. Higher instantaneous deformation can be connected with simultaneous shearing at more suitable shear band configurations. The cell morphology with the various cell sizes is observed at the failure of the metallic glasses. At the failure of high strength metallic glasses, the cells are formed in short time due to the release of high amount of stored elastic energy. In this case the uniform cell morphology with the cell size of about 20 nm is observed.

Abstract: At room temperature, the low carbon steel were cold rolled from 0.5 mm to 1 μm without intermediate annealing by asymmetrical rolling (ASR) process. the microstructure were investigate by Electron Backscatter Diffraction (EBSD) and transmission electron microscopy (TEM). Lath structure (~300 nm) and local nanograins (~60nm) were obtained through ASR with extensibility up to 50,000%. The high angle boundaries were predominant. The results indicated that inhomogeneous deformation and combination deformation mechanism of dislocation slip and grain boundary slip in the foil ASR process.

Abstract: Inhomogeneous deformation in polycrystalline material is interesting matter, because the concentration point of deformation relates with the origins of yield, fracture and recrystallization. Plastic strains in three-dimension during tensile deformation have been investigated by using the marker tracking method in synchrotron X-ray microtomography. Three-dimensional position of grains was detected by grain-boundaries visualizing method. The variation of deformation were measured for each grain. We summarized how much degree grains was deformed inhomogeneously comparable to the plastic deformation in whole specimen.

Abstract: The Qinghai-Tibet highway subgrade inhomogeneous deformation is very serious because of the bad climate environment and the special engineering condition of permafrost. To reveal the mechanism of subgrade diseases, based on the theory of elastic-plastic deformation, the control equation of the stress and deformation field of the subgrade is established. We analyze subgrade stress and deformation field by finite element software. Considering effect of the southern and northern slopes, the model of the inhomogeneous deformation of the subgrade was established. Then we calculated the variation characteristic of the lateral inhomogeneous deformation under different melting depth. The results showed that the melting interlayer, melting depth and the effect of southern and northern slopes were the key factors influencing the permafrost subgrade lateral inhomogeneous deformation.

Abstract: The triaxial equipment of GDS with digital image processing technique is used in drained test of sand. The result shows that the end restraint and initial defect have significant effect on mechanical properties of sand sample. End restraint and initial defect of sample both can cause inhomogeneous deformation, then form macroscopic shear band in soil testing and numerical simulation. Shape multiformity and formation mechanism of shear band in normal consolidated soil is analyzed based on Modified Cam-Clay Model under plane strain condition. The result shows that end restraint and initial defect can induce and control the formation and shape of shear band. The impaction of different boundaries and initial defect setting are analyzed.

Abstract: Local orientation distributions of two neighbouring grains initially orientated near (01l)[100] and (210)[001], in a pure Al poly-crystal aggregate rolled by a reduction of 65% at room temperature have been investigated using electron backscatter diffraction (EBSD) technique. It was found that the rotation angles of zones adjacent to both sides of initial boundary (BP) are less than that of zones remote from the boundary (IP), which reveals that rotation incompatibility and heterogeneity of local orientations within individual grains during rolling. A type of improved Taylor type crystal plasticity models, in which an added prescribed shear (APS) depending on distances from grain boundary proposed, was established to illustrate development of micro-textures in each grain. The results simulated by the APS-Taylor models well agree with the micro-textures examined by EBSD.

Abstract: Plastic deformation behavior during equal channel multi-angular pressing (ECMAP) was analyzed using the three dimensional finite volume method of the commercial code MSC.Superforge. In order to understand local and global deformation characteristics, effective strain and pressing load histories were investigated. The predicted plastic deformation behavior of the workpiece material during ECMAP of route A, route B and route C with a theoretical total strain of ~2.2 upon a single pass at three different friction factors (m=0, 0.1 and 0.2) was compared. The predicted strain results show different values in outside and similar values in central regions of the processed workpieces with different friction and forming routes. The pressing loads are higher under higher friction condition, showing almost no difference with three different pressing routes.