基于COMSOL Multiphysics的光子晶体线缺陷波导设计

文章利用COMSOL Multiphysics有限元物理仿真软件构建二维光子晶体,并计算其光子能带,简要介绍了超胞法计算线缺陷带结构,以及计算了线缺陷光子晶体的透射率和线缺线光波导传输效果。

Sheet Metal Forming Simulation and Its Application in Stamping Process of Automobile Panels

The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.

Upper-bound and finite element analyses of multi-row sprocket during cold semi-precision forging process

The cold semi-precision forging of a multi-row sprocket was investigated using upper-bound （UB） and finite element methods combined with experiments. Based on the design of a new tooth profile for the sprocket, a cold semi-precision forging process and a kinematically admissible velocity field for filling the die cavity were proposed. Using the UB method, the velocity fields of the sprocket billet in the forming process were divided theoretically and calculated. The process of forging a multi-row sprocket was simulated using the FEM package Deform-3D V6.1 to obtain the distributions of the velocity field and the effective stress field in filling the die cavity. Similar to the simulated results, the experiment on cold forging a 5052 aluminum alloy sprocket was successfully performed. By comparing the calculated （UB method）, experimental and simulated load-stroke curves, the calculated and simulated results were basically in accordance with the experimental results. The study provides a theoretical foundation for the development of the precision forging of multi-row sprockets.

The simulation of electrostatic coupling intra-body communication based on the finite-element method

In this paper, investigation has been done in the computer simulation of the electrostatic coupling IBC by using the developed finite-element models, in which a.the incidence and reflection of electronic signal in the upper arm model were analyzed by using the theory of electromagnetic wave;b.the finite-element models of electrostatic coupling IBC were developed by using the electromagnetic analysis package of ANSYS software;c.the signal attenuation of electrostatic coupling IBC were simulated under the conditions of different signal frequencies, electrodes directions, electrodes sizes and transmission distances. Finally, some important conclusions are deduced on the basis of simulation results.

Simulation of hydrogen diffusion in welded joint of X80 pipeline steel

Hydrogen diffusion coefficients of different regions in the welded joint of X80 pipeline steel were measured using the electro-chemical permeation technique. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the welding zone, and temperature-dependent thermo-physical and mechanical properties of the metals. A three dimensional finite element model was developed and a coupled thermo-mechanical-diffusion analysis was performed. Hydrogen concentration distribution across the welded joint was obtained. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the weld zone and the base metal.Simulation results are well consistent with theoretical analysis.

Simulation of 3D Needle-Tissue Interaction with Application to Image Guided Prostate Brachytherapy

To improve global control of disease and reduce global toxicity, a complex seed distribution pattern should be achieved with great accuracy during brachytherapy.However, the interaction between the needle and prostate will cause large deformation of soft tissue.As a result, seeds will be misplaced, sharp demarcation between irradiated volume and healthy structures is unavailable and this will cause side effects such as impotence and urinary incontinence.In this paper, a 3D nonlinear dynamic finite element s...

Changes in Coupled Vibration Frequencies and Modes of Wall-Cavity Systems Induced by Stiffness Variation in the Structure

Problems of fluid structure interactions are governed by a set of fundamental parameters. This work aims at showing through simple examples the changes in natural vibration frequencies and mode shapes for wall-cavity systems when the structural rigidity is modified. Numerical results are constructed using ANSYS software with triangular finite elements for both the fluid （2D acoustic elements） and the solid （plane stress） domains. These former results are compared to proposed analytical expressions, showing an alternative benchmark tool for the analyst. Very rigid wall structures imply in frequencies and mode shapes almost identical to those achieved for an acoustic cavity with Neumann boundary condition at the interface. In this case, the wall behaves as rigid and fluid-structure system mode shapes are similar to those achieved for the uncoupled reservoir case.

Modelling of Non-coaxial Viscoplastic Deformation in Geodynamics

The formation of shear bands for time and length scales appropriate for deformation processes in the upper Lithosphere is investigated in plane strain finite element simulations under predominantly uniaxial extension and compression, respectively. The direction of gravity is assumed orthogonal to the extension/compression axis. Mathematically, the formation of shear zones may be explained as a consequence of changes in the type of the governing model equations. Such changes or bifurcations depend strongly on the details of the constitutive relationships such as strain softening, thermal or chemical effects, associated or non-associated--coaxial or non-coaxial flow rules. Here we focus on strain softening and coaxial and non-coaxial flow rules. In the simulations, we consider an initially rectangular domain with the dimensions Lo, Ho in the horizontal, vertical directions, respectively. The domain is extended or compressed by prescribing a uniform, horizontal velocity field along one of the vertical boundaries while keeping the opposite boundary fixed. An important global descriptor of the deformation process is the relationship between the horizontal stress resultant （average horizontal stress） and the strain ln（L/Lo）, where L is the deformed length of the domain. The main goal of this paper is to investigate key factors influencing the phenomenology of the localization process such as flow rule, coaxial, non-coaxial and strain softening. Different origins of the mesh sensitivity of deformations involving localization are also investigated.

Research on residual stress inside Fe-Mn-Si shape memory alloy coating by laser cladding processing

The stainless Fe-Mn-Si shape memory alloy(SMA) coating was prepared on the surface of AISI 304 stainless steel. The principal residual stress measured by the mechanical hole-drilling method indicates that the Fe-Mn-Si SMA cladding specimen possesses a lower residual stress compared with the 304 stainless steel cladding specimen. The mean stress values of the former and the latter on 10-mm-thick substrate are 4.751 MPa and 7.399 MPa, respectively. What's more, their deformation values on 2-mm-thick substrate are about 0° and 15°, respectively. Meanwhile, the variation trend and the value of the residual stress simulated by the ANSYS finite element software consist with experimental results. The X-ray diffraction(XRD) pattern shows ε-martensite exists in Fe-Mn-Si SMA coating, which verifies the mechanism of low residual stress. That's the γ→ε martensite phase transformation, which relaxes the residual stress of the specimen and reduces its deformation in the laser cladding processing.