Papers by Keyword: Anisotropic

Abstract: Representative volume element methord is used to simplify HGB (hollow glass bead) periodically-reinforced composite model into representative volume element. Orthotropic properties and change rules of effective elastic constants (modulus and Poisson's ratio) and HGB wall-thickness of representative volume element are studied by using the finite element methord. The study finds that there is no obvious difference of each direction of the three kinds of composites with different filling types; the effect of filling type is not very obvious also.

Abstract: Anisotropic BaBi₄Ti₄O15 powder was synthesized by a molten salt synthesis (MSS) method in K₂SO₄-Na₂SO₄ flux and the effects of different process parameters such as calcining temperature, and ratio of salt to reactant (R) on the phase formation and morphology of anisotropic BaBi₄Ti₄O₁₅ particles were also investigated. The as-synthesized powder calcined at 850-950°C exhibits a single tetragonal BaBi₄Ti₄O₁₅ phase. The morphology of BaBi₄Ti₄O₁₅ powder could be adjusted by changing the synthesis conditions. The average particle size (APS) of BaBi₄Ti₄O₁₅ powder increased with R changing from 0.8 to 1.0, while it decreased with further increasing of R to 1.2. In addition, the APS increased with increasing calcining temperature and it showed an Arrhenius dependence on the temperature. The corresponding apparent activation energy for particle growth is 31.9kJ/mol for calcining temperature of 850-1000°C.

Abstract: This paper presents a boundary element-free computational method for the fracture analysis of 2-D anisotropic bodies. The study starts from a derived traction boundary integral equation (BIE) in which the boundary conditions of both upper and lower crack surfaces are incorporated into and only the Cauchy singular kernal is involved. The boundary element-free method is achieved by combining this new BIE and the moving least-squares (MLS) approximation. The new BIE introduces two new variables: the displace density and The dislocation density. For each crack, the dislocation density is first expressed as the product of the characteristic term and unknown weight function, and the unknown weight function is approximated with the MLS approximation. The stress intensity factors (SIFs) can be calculated from the the weight function. The examples of the straight and circular-arc cracks are computed, and the convergence and efficiency are discussed.

Abstract: In order to solve the existing problems such as the less-plump corners and wrinkle during the forming process of a double curvature thin-wall part. Material parameter formulas are calculated based on Hill 1948 anisotropic yield criterion and flow rule. The material mechanical property parameters of 2A12 are obtained using uniaxial tensile experiment. Single factor test method is used and LS-DYNA is applied to conduct finite element analysis. So the influence law of holding force, blank shape and blank size imposed on the finite element model are calculated in sequence. On the basis of these laws, that the blanking force, blank dimension and blank shape are decided. Stamping die for the experiment model is designed and made, deformation measurement technology of coordinate grid circle is used to carry out strain analysis. From the comparison result between experiment and simulated data, it can be seen that Hill 1948 yield criterion and flow law can better solve the formability of 2A12 sheet.

Abstract: Direction transform; image fusion; infrared images; fusion rule; anisotropic Abstract Based on analysing the feature of infrared and the visible, this paper proposed an improved algorithm using Directionlet transform.The feature is like this: firstly, separate the color visible images to get the component images, and then make anisotropic decomposition for component images and inrared images, after analysing these images, process them according to regional energy rules ,finally incorporate the intense color to get the fused image. The simulation results shows that,this algorithm can effectively fuse infrared and the visible image, moreover, not only the fused images can maintain the environment details, but also underline the edge features, which applies to fusion with strong edges, therefore,this algorithm is of robust and convenient.

Abstract: A model for anisotropic Ostwald ripening was developed using a chemical potential (weighted mean curvature) difference as a driving force for mass-transport. Based on this model, grain growth simulations of silicon nitride during the phase transformation and Ostwald ripening were performed. Comparison with experimental results during the phase transformation suggests that grain growth be controlled by interfacial reaction. Simulations of Ostwald ripening predict that the growth exponent be 3 for the reaction-controlled case, and increases up to 5 as the growth kinetics shifts from reaction-controlled to diffusion-controlled. It was reported that the mean aspect ratio of silicon nitride crystals increased during the phase transformation, and decreased during Ostwald ripening. These behaviors were successfully simulated by this model. The concave depression at the tip of silicon nitride crystal that was experimentally observed. Simulations by the Ostwald ripening model demonstrated that it could be developed when the liquid phase was super-saturated, and further that the tip shape was a function of the liquid concentration.

Abstract: The increasing use of fibre-reinforced composites in high performance structures has brought a renewed interest in the analysis of cracks, wedges, and multi-material wedges in anisotropic materials. This paper will address three crucial stages of the general stress concentrator analysis: i) numerical procedures for the determination of eigenvalues and eigenvectors in Williams-like asymptotic expansion for multi-material wedge; ii) approaches to an accurate calculation of the near crack tip fields – the application of so-called two-state (or mutual) conservation integrals; iii) application of fracture criteria for the assessment of fracture inception at the general stress concentrators - concept of the so called finite fracture mechanics.

Abstract: The parameters such as aniotropic property, blank holder force and friction coefficient between tool and blank are not only effect on the forming force, stress and strain distribution of the worpiece, but also on the earing in products. In this paper, the finite element method is used to investigate the earing of the deep drawing process. In order to verify the prediction of FEM simulation of the earing in the cylindrical cup drawing process, the experimental data are compared with the results of the current simulation. A finite element analysis is also utilized to reduce the earing profile of the drawn products, a reverse forming method for obtaining the initial blank’s shape according to the forward cup deep drawing simulation is proposed.

Abstract: This research was carried out to grasp the factors influencing to the ultrasonic velocity to improve the efficiency of the ultrasonic wave test using as the method of NDE of wood. However, it was difficult to detect the defect of wood accurately, because ultrasonic velocity is influenced by various factors. So, some effect factors, which were not concerned with decay, were confirmed at first. Therefore, in this research, we tried to find the factors which affect on the natural characters and the ultrasonic velocity at decayed wood, additionally, we tried an anatomic experiment and analyze. As a result of research, the velocity at radial direction was faster than that at tangential direction and the ultrasonic velocity at immature wood and reaction wood was slower than that at normal wood. And the ultrasonic velocity was more the slower at bigger the length of decay and reduction of weight.

Abstract: The compactly supported radial basis functions (RBFs) is modified and used to the wave propagation in the anisotropic materials. An example to simulate the wave propagation in composite material is used in the paper to verify this method. In this example, stress wave propagation histories are obtained. The comparison between results by this method and by finite element method is also made. And the agreement with two results shows that this method can be used to simulate the wave propagation history in anisotropic material efficiently.