Papers by Keyword: 3 Dimension

Abstract: Rapid cooling of TiAl-based alloy from α phase (disordered hexagonal, A3) generates  phase (ordered tetragonal, L1o) grains through massive transformation nucleating mostly over the α/α grain boundaries. This current work deals with the identification and the validation of different nucleation mechanisms during  massive transformation in TiAl-based alloys. Special attention has been given to the variant selection criteria for the nucleation of the massive structures along different types of α/α grain boundaries. The  massive domains formed along the grain boundaries were analysed using high resolution electron backscattered diffraction (EBSD). Statistical studies were made on different nucleation sites and different mechanisms are proposed. Two–dimensional studies of the nucleation mechanism suggest that the minimization of the interfacial energy could be the predominant criteria during the grain boundary nucleation. In order to verify this nucleation criterion in three-dimensions, serial sections were made and EBSD maps were taken and analysed in each section. The variant selection observed during the nucleation and the growth of the  massive grains is further discussed after getting a broader view under three-dimensional investigations.

Abstract: Differential geometry and toplogy-based three-dimensional (3D) analysis was conducted to understand pearlite spheroidization mechanism in an eutectoid steel. Morphological change during aging below A1 tempearture was examined in terms of Gaussian(K)/mean curvatures(H), genus and Euler characteristics based on 3D images.The holes presentnaturally grown cementite lamella caused shape instability andinduced shape evolution of the lamellar structure during spheroidization. 3D visualization demonstrated that the intrinsic holes played an important role in the initiation and development of pearlitespheroidization. The hole coalescence and expansion causedthe breakup of large cementite lamellae into several long narrow ribbons. H-K plot actually suggested that the number of thses holes decreased with increasing aging period. In addition, small cementite particles and narrow rod cementite decreased during aging. These microstractural evolutions were discussed from the view point of ferrite/cementite interfacial energy.

Abstract: In this paper biomechanical behavior of dental implant and surrounding bone system are investigated under static occlusal loads through 3D nonlinear finite element analysis (FEA), taking into account the interaction of implant-bone and implant-abutment contact interfaces. Stress-based performances of four commercially-available dental implant systems are evaluated in detail, demonstrating that implant and bone stability is strongly affected by implant-abutment connection structure as well as by a number of geometrical parameters. The results also indicate that platform-switching configuration can significantly reduce the crestal bone stress peaks, which contributes to the bone preservation for long-term success.

Abstract: The particle circulation rate and gas–solid contacting efficiency are important parameters for the project of spouted beds, applied in many industrial processes. Due to the restrictions found in the identification of flow regimes through visual observation, new techniques have been developed to obtain a better gas and particle dynamics description, necessary for the evaluation of these parameters. One of these techniques has been the CFD simulation. In this work the pattern of solids and gas flows in a spouted bed was numerically simulated using a 3D Eulerian multiphase model. Soybean particles had been used in the attainment of data of pressure drop fluctuation and power spectrum as a function of gas velocity in an experimental apparatus. The 3D simulated solids volume fraction profiles allow the identification of the flow regimes showing a good agreement with the experimental data.

Abstract: In order to measure 3D displacement components and surface strain distributions of objects, three systems for digital holographic interferometry were developed. In this study, these three systems are introduced and the applications to measurement of 3D displacement components and surface strain distributions of cantilevers are shown.

Abstract: Grain structures in polycrystalline materials are typically three dimensional (3D) structures, but by far the most characterizations of grain structures are done by microscopy and are thus limited to 2D. In the present work 3D grain structures in a well-annealed cylindrical aluminium (AA1050) sample is characterized and analyzed. The characterization is done by 2 methods i) by non-destructive 3-dimensional x-ray diffraction (3DXRD) ii) by serial sectioning and subsequent EBSP mapping of entire circular 2D sample sections; 50 sections are mapped In total 333 grains are reconstructed. It is found that the 3D grain morphologies can be quite complex in particular for the larger grains, the number of neighbours varies significantly and values above 20 are not unusual. When the results from the 2 methods are compared, it is found that the crystallographic agreement is very good and within experimental uncertainties. Slightly more significant differences are found when the reconstructed grain morphologies are compared. Reasons for this are discussed.

Abstract: The distribution of nucleation sites in 90% cold rolled aluminium (AA1050) annealed for 1h at 280°C has been determined by serial sectioning the sample and characterizing each section using the electron back scattering pattern (EBSP) method in the SEM. In total 1844 nuclei are identified. It was found that the nuclei are not randomly distributed but clustered preferentially along TD-RD planes in the sample. The results are presented and implications of clustered nucleation on recrystallization kinetics are discussed.

Abstract: In this paper, a simplified cellular automaton (CA) model was proposed for modeling the evolution of microstructure in solidification process of AZ91D magnesium alloy. Since the calculation time was significantly reduced, it might be used to predict the microstructure field of a real Mg component after solidification. The stochastic nucleation, competitive growth processes of many grains with various crystallographic orientations and the formation of eutectic structure were also taken into account. Furthermore, step castings were poured with sand and permanent molds and metallographic experiments were carried out for validating the developed models. It was shown that the simulation results are in good agreement with those obtained in the experiments.

Abstract: The periodically distributed fracture spacing phenomenon exists in the failure process of the reinforced concrete prism under uniaxial tension. In this paper, A numerical code RFPA3D (3D Realistic Failure Process Analysis) is used to simulate the three-dimensional failure process of plain concrete prism specimen and reinforced concrete prism specimen under uniaxial tension. The reinforced concrete is represented by a set of elements with same size and different mechanical properties. They are uniform cubic elements and their mechanical properties, including elastic modulus and peak strength, are distributed through the specimens according to a certain statistical distribution. The elastic modulus and other mechanical properties are weakened gradually when the stresses in the elements meet the specific failure criterion. The displacement-controlled loading scheme is used to simulate the complete failure process of reinforced concrete. The analyses focus on the failure mechanisms of the concrete and reinforcement. The complete process of the fracture for the plain concrete prism and the fracture initiation, infilling and saturation of the reinforced concrete prism is reproduced. It agrees well with the theoretical analysis. Through 3D numerical tests for the specimen, it can be investigated the interaction between the reinforcement and concrete mechanical properties in meso-level and the numerical code is proved to be an effective way to help thoroughly understand the rule of the reinforcement and concrete and also help the design of the structural concrete components and systems.

Abstract: A numerical code RFPA3D (Realistic Failure Process Analysis) is used to simulate the crack initiation and propagation in FRP-strengthened concrete beam under external loading. In our model, the FRP-strengthened concrete is assumed to be a three-phase composite composed of concrete, FRP, and interface between them. The displacement-controlled loading scheme is used to simulate the complete failure process of FRP-strengthened concrete the numerical simulation of failure process of the specimens. It is found that the main failure mode is the interfacial debonding and the interfacial debonding may propagate either within the adhesive layer or through concrete layer in the vicinity of bond interface. The simulation results agree well with the experiment observations. The width of the FRP sheet is considered an important factor not only to significantly influence the debonding propagation type and crack distribution but also to control the ultimate load-capacity and ultimate strain. This study is focused on the failure process of the FRP-strengthened concrete beam and the effects of the width of FRP sheet on the failure mode and on the structural load-carrying capacity of concrete structures.