Papers by Keyword: Grain Orientation

Abstract: At the present time the problem of import substitution of grinding tools is particularly of current interest. The current situation makes many foreign producers gradually leave the Russian market while domestic enterprises cannot offer competitive grinding tools that possess the characteristics and quality comparable to foreign analogs.

Abstract: The grain orientation plays a great important role during single grain grinding. Single grain grinding simulation could offer an insight into the material removal behavior. However, grinding simulation with FE methods has problems arising from large deformations at the chip root and negative rake angles of the grain. In this work, a coupled Eulerian-Lagrangian method (CEL) is used to model the grinding behavior of single diamond grain in different orientations. The influence of the grain orientations on the grinding forces, grinding process (sliding, ploughing and cutting) and critical undeformed chip thickness are analyzed. The force ratio shows great accordance with the analytical calculation data. The simulation results show that the chip generates quickly and the special grinding force is relatively small when the diamond particle is in octahedral orientation (111)-(100). The workpiece material flows to the side and front owing to the pressing of cutting crystal face. The swelling of the material is generated beside the abrasive grain. The range and height of swelling are increased gradually and kept invariant after chip formation. The deformation of workpiece material contacting with grain edge is very severe. Therefore the biggest residual stress appears at the grain edge of the groove.

Abstract: In the Li2O-Nb2O5-TiO2 system, Li1+x-yNb1-x-3yTix+4yO3 (0.06  x  0.33, 0  y  0.09) (LNT) forms with a superstructure, which is the so-called M-phase. In this work, as a first step toward application of the unique qualities of an electro-ceramic with an anisotropic structure, we prepared an oriented LNT balk ceramic by slip casting in a strong magnetic field of 12 T. The direction of the magnetic field was parallel to the casting direction. The compact was densified by cold isostatic pressing and then heated at 1373 K. The obtained specimen was analyzed by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Consequently, the c-axis of the LNT powders was aligned parallel to the magnetic field and a high orientation degree was achieved in a strong magnetic field of 12 T

Abstract: Grain-oriented Bi₄Ti_2.92Nb_0.08O₁₂ (BITN) ceramics were prepared by hot-forging (HF) method. The grain orientation factor, F, of BITN ceramic determined by the Lotgering method were approximately 0.96. The resistivity, ρ, along the c-axis of HF-BITN ceramic is higher than that of the a,b-axis of HF-BITN and OF-BITN ceramics for the temperature range from 100 to 400°C. The ρ along the direction parallel to the c-axis is found to be about 10⁹ Ω·cm at 400°C, which is about ten times larger than that of OF-BITN ceramics. From resonance and anti-resonance characteristics, electromechanical coupling factor, k₂₄, was 0.026 at room temperature.

Abstract: Understanding major mechanisms affecting material strength such as grain size, grain orientation and dislocation mechanism from atomistic viewpoint can empower scientists and engineers with the capability to produce vastly strengthened materials. Computational studies can offer the possibility of carrying out simulations of material properties at both larger length scales and longer times than direct atomistic calculations. The study has conducted theoretical modeling and experimental testing to investigate nanoscale mechanisms related to material strength and interfacial performance. Various computational algorithms in nanomechanics including energy minimization, molecular dynamics and hybrid approaches that mix atomistic and continuum methods to bridge the length and time scales have been used to thoroughly study the deformation and strengthening mechanisms. Our study has also performed experiments including depth-sensing indentation technique and in-situ pico-indentation to characterize the nanomechanisms related to material strength and tribological performance. In this project, we have developed the innovative mutil-scale algorithms in the area of nanomechanics. These approaches were used to studies the defect effect on the mechanical properties of thin film, mechanical properties of nanotubes, and tribological phenomena at nanoscale interfaces.

Abstract: Zinc whiskers threaten the safety of electronic components due to their electrical conductivity. Factors that control zinc whisker growth are still unknown. The aim of this study was to investigate the effect of current density (1.5, 2.25 and 3.0 A/dm2) on the formation of zinc whiskers, and to relate this to the microstructure of the deposit. Scanning Electron Microscopy (SEM) analyses show that the surface morphologies of deposits became rougher when current density increased; however, nodule density increased from 25/mm2 to 53/mm2 when current density increased from 1.5 to 2.25 A/dm2, and it decreased to 24/mm2 when current density increased to 3.0 A/dm2. X-ray diffraction analyses (XRD) show that the preferred orientation of deposits remain when current densities increased from 1.5 to 2.25 A/dm2, while it changed to when current density increased to 3.0 A/dm2. Results show that zinc coatings electroplated at 2.25 A/dm2 may have greater risk of whisker growth then that electroplated at 1.5 or 3.0 A/dm2.

Abstract: As a numerical tool for examining the microstructural fracture behavior in the smart and intelligent materials, a finite element method with the interface element was developed and the applicability of this method was studied through the serial computations using virtual polycrystalline models. As the results assuming the influence of grain orientation on the grain boundary, it was found that the anisotropic mechanical property of grain boundary (interaction between opening and slipping deformations) would be a dominant factor of the fracture process. Also, by employing the theory of crystal plasticity for the mechanical property of grain, it was revealed that the stress concentrations caused by both the mismatch between neighbor grains and the slipping at grain boundary could be demonstrated by using this method.

Abstract: We postulated a softening model involving grain rotation that results in diffusion-accommodated grain-boundary sliding. This numerical model was used to compute the proportion evolution of grains within shear bands and was also employed to predict the softening of nanocrystalline materials considering non-homogeneous plastic deformation due to shear bands. The effect of softening mechanism for total stress-strain relation and the grain size and mean maximum Schmid factor effect was also considered in our model.

Abstract: A nanostructured layer can be introduced on the surface of metallic materials by surface severe plastic deformation. A surface severe plastic deformation method-Supersonic Particles Bombarding (SSPB) was used to treat the anealled 40Cr steel. The surface and cross sectional microstructure of 40Cr steel after SSPB treatment were characterized by means of X-ray diffraction, optical microscopy and transmission electron microscopy equipped with a Kikuchi line program to determine the grain orientations. Equiaxed nanocrystallites with random crystallographic orientation were obtained on the top surface of 40Cr steel after SSPB treatment. The surface microstructure was composed of nanostructure area, deformed area and matrix. Geometrically necessary boundaries and incidental dislocation boundaries were formed in the deformed ferrite at the distance to the surface of about 50-60μm, and the original coarse ferrite grain was divided into lamaller structure.

Abstract: This study developed new algorithms to simulate the grain pattern and orientation of radiata pine boards based on the geometrical and growth features of radiata pine trees. Scenario simulation is presented in the article. The established methodology offers insights for sawmills to establish feasible log breakdown strategies and maximize radiata pine timber value.