基于PFC^(3D)的花岗岩剪切破裂细观裂隙与能量演化规律探究

为了探究法向应力对岩石剪切过程中细观损伤演化的影响,开展了不同法向应力作用下的花岗岩直剪试验与PFC^(3D)数值模拟试验,结合声发射信号监测及声发射信息特征值RA(上升时间与振幅的比值)与AF(声发射振铃计数与持续时间的比值)的分析,对花岗岩在不同法向应力作用下剪切变形过程中细观微裂纹及能量演化特征进行了研究,研究结果表明:基于平行黏结接触模型建立的PFC^(3D)模型,不仅在宏观力学参数与破坏模式上与岩石物理试验相近,而且在岩石细观裂纹与能量演化规律上也与岩石物理试验基本一致;花岗岩剪切破坏过程中主要产生张拉裂纹,峰值应力点前产生的微裂纹只占裂纹总数的10%~30%,且法向应力越大,峰值应力点前岩石内部产生的微裂纹数量越少;花岗岩剪切变形过程中,声发射信号可以分为平静期、稳定期和加速期,法向应力越大,平静期越明显,即法向应力对岩石内部微裂纹的生成起抑制作用;随着法向应力的增大,花岗岩剪切破坏过程中,声发射累计振铃计数与岩石内部微裂纹总数均逐渐增大;随着法向应力的增大,花岗岩剪切破坏过程中产生的剪切裂纹数量及其占微裂纹总数的比例均逐渐增加;花岗岩剪切变形过程中外力做功转化为弹性能与耗散能,随着法向应力增大,岩石剪切破坏所需总能量逐渐增大,弹性能与耗散能近似线性增大,且其中耗散能所占的比例逐渐增大。

Research on the Application of Virtual Simulation and 3D Animation Technology in the Teaching of Road and Bridge Majors in Higher Vocational Colleges

The informatization of higher vocational education is the future development trend,and it is also encouraged and promoted by the Ministry of Education.This article focuses on the road and bridge major,combined with the author’s experience in introducing virtual simulation and three-dimensional(3D)animation technology into relevant course teaching in recent years,discusses the application of virtual simulation and 3D animation technology in higher vocational education and promotes classroom revolution,to obtain better teaching effect.

Material driven workability simulation by FEM including 3D processing maps for magnesium alloy

The three-dimensional （3D） processing maps considering strain based on the two-dimensional （2D） processing maps proposed by PRASAD can describe the distribution of the efficiency of power dissipation and flow instability regions at various temperatures, strain rates and strains, which exhibit intrinsic workability related to material itself. Finite element （FE） simulation can obtain the distribution of strain, strain rate, temperature and die filling status, which indicates state-of-stress （SOS） workability decided by die shape and different processing conditions. On the basis of this, a new material driven analysis method for hot deformation was put forward by the combination of FE simulation with 3D processing maps, which can demonstrate material workability of the entire hot deformation process including SOS workability and intrinsic workability. The hot forging process for hard-to-work metal magnesium alloy was studied, and the 3D thermomechanical FE simulation including 3D processing maps of complex hot forging spur bevel gear was first conducted. The hot forging experiments were carried out. The results show that the new method is reasonable and suitable to determine the aoorooriate nrocess narameters.

3-D Simulation of FINFET

An SOI MOSFET with FINFET structure is simulated using a 3 D simulator. I V characteristics and sub threshold characteristics,as well as the short channel effect(SCE) are carefully investigated.SCE can be well controlled by reducing fin height.Good performance can be achieved with thin height,so fin height is considered as a key parameter in device design.Simulation results show that FINFETs present performance superior to conventional single gate devices.

Analysis of Tidal Current Energy Potential in the Major Channels of the Bohai Strait Based on Delft3D

The utilization and development of tidal current energy can help alleviate the current energy shortage,improve the global ecological environment,and maintain sustainable development.In this study,numerical simulation is carried out on a rectangular grid using Delft3D.The tidal current energy potential of the major channels in the Bohai Strait is further simulated and estimated by comparing the simulated and measured data.Results show that the flow module in Delft3D has good modeling ability for the assessment of tidal current energy potential.The average flow velocity,maximum flow velocity,and energy flow density are consistent.The Laotieshan Channel,located in the northern part of the Bohai Strait,shows a large tidal current energy potential.The maximum flow velocity of this channel can reach 2 m s-1,and the maximum energy flow density can exceed 500 W m-2.The tidal current energy in the Laotieshan Channel is more than 10 times that in other channels.Therefore,this study advocates for the continued exploration and exploitation of the tidal current energy resources in the Laotieshan Channel.

Using 3D TCAD Simulation to Study Charge Collection of a p-n Junction in a 0.18μm Bulk Process

Single event transient of a real p-n junction in a 0.18μm bulk process is studied by 3D TCAD simulation. The impact of voltage, temperature, substrate concentration, and LET on SET is studied. Our simulation results demonstrate that biases in the range 1.62 to 1.98V influence DSET current shape greatly and total collected charge weakly. Peak current and charge collection within 2ns decreases as temperature increases,and temperature has a stronger influence on SET currents than on total charge. Typical variation of substrate concentration in modern VDSM processes has a negligible effect on SEEs. Both peak current and total collection charge increases as LET increases.

基于SolidWorks Simulation的3D打印机机体静力学分析

近年来,3D打印机作为一种高效率的成型设备被广泛的使用,然而,其高速性、高精度与高可靠性与其机体的轻量化设计存在一定的矛盾关系。通过SolidWorks软件对3D打印机机体进行轻量化设计,并使用集成的Simulation仿真软件对设计模型进行快速静态力学分析,参照仿真结果对轻量化设计的模型进行验证与优化。通过集成化的三维建模软件和仿真软件,实现了3D打印机的模型设计和模型力学分析,验证了3D打印机设计的合理性和可靠性,为3D打印机的轻量化设计提供理论指导和修改建议,节省设备的研发周期和研发成本。

Image processing based three-dimensional model reconstruction for cross-platform numerical simulation

Numerical simulation is the most powerful computational and analysis tool for a large variety of engineering and physical problems.For a complex problem relating to multi-field,multi-process and multi-scale,different computing tools have to be developed so as to solve particular fields at different scales and for different processes.Therefore,the integration of different types of software is inevitable.However,it is difficult to perform the transfer of the meshes and simulated results among software packages because of the lack of shared data formats or encrypted data formats.An image processing based method for three-dimensional model reconstruction for numerical simulation was proposed,which presents a solution to the integration problem by a series of slice or projection images obtained by the post-processing modules of the numerical simulation software.By means of mapping image pixels to meshes of either finite difference or finite element models,the geometry contour can be extracted to export the stereolithography model.The values of results,represented by color,can be deduced and assigned to the meshes.All the models with data can be directly or indirectly integrated into other software as a continued or new numerical simulation.The three-dimensional reconstruction method has been validated in numerical simulation of castings and case studies were provided in this study.

Simulation of the Construction of a Swivel Bridge Using BIM 4D

The AEC (Architecture, Engineering, and Construction) industry is gradually shifting away from 2D CAD drawings and toward Building Information Modeling as a result of the fast development of science and technology (BIM). The BIM idea’s introduction emphasizes the need to specify a building in a single building model with adequate information to suit its different needs rather than defining it in fragmented documents. This research work aims to use the BIM 4D for the simulation of the construction sequence of a Swivel Bridge. For that, the software Revit was used to make the 3D model of the bridge, and the software Navisworks was used for the 4D construction simulation of the project. The results demonstrated that BIM technology could help reduce delays and problems with the schedule and improve communication among stakeholders, and BIM visualization and simulation features were very useful compared to traditional planning methods.

Digital Simulation Platform for Satellite Launch Mission Verification

To simulate the satellite launch mission under a general platform which could be used in a full-digital mode as well as in a semi-physical way, is an important way to certify the mission design performance as well as technical feasibilities, and it relates to complex system simulation methods such as multi-disciplinary coupling, multi-language modeling as well as interactive simulation and virtual simulation technologies. This paper introduces the design of a digital simulation platform for satellite launch mission verification.The platform has the advantages of high generality and extensibility, being easy to build up. The Functional Mockup Interface(FMI) Standard is adopted to achieve integration of multi-source models. A WebGL based 3D visual simulation tool is also adopted to implement the virtual display system which could display the rocket launch process and rocket-satellite separation with high fidelity 3D virtual scenes. A configuration tool was developed to map the 3D objects in the visual scene with simulation physical variables for complex rocket flight control mechanisms, which greatly improves the platform's generality and extensibility. Finally the real-time performance had been tested and the YL-1 launch mission was adopted to demonstrate the functions of the platform.The platform will be used to construct a digital twin system for satellite launch missions in the future.

Numerical simulation of a combined oxidation ditch flow using 3D k-ε turbulence model

The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.

Numerical Simulation of the Protective Effect of Complex Boundaries Toward Shock Waves in a 3D Explosive Field

A numerical method is presented that simulates 3D explosive field problems. A code MMIC3D using this method can be used to simulate the propagation and reflected effects of all kinds of rigid boundaries to shock waves produced by an explosive source. These numerical results indicate that the code MMIC3D has the ability in computing cases such as 3D shock waves produced by air explosion, vortex region of the shock wave, the Mach wave, and reflected waves behind rigid boundaries.

3D Finite Element Simulation of Tunnel Boring Machine Construction Processes in Deep Water Conveyance Tunnel

Applying stiffness migration method,a 3D finite element mechanical model is established to simulate the excavation and advance processes.By using 3D nonlinear finite element method,the tunnel boring machine(TBM) excavation process is dynamically simulated to analyze the stress and strain field status of surrounding rock and segment.The maximum tensile stress of segment ring caused by tunnel construction mainly lies in arch bottom and presents zonal distribution.The stress increases slightly and limitedly in the course of excavation.The maximum and minimum displacements of segment,manifesting as zonal distribution,distribute in arch bottom and vault respectively.The displacements slightly increase with the advance of TBM and gradually tend to stability.

Study of 3-D Numerical Simulation for Gas Transfer in the Goaf of the Coal Mining

In order to simulate field distribution rules,mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established,based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode,surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally,a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible.

Modeling and simulation of 3D thermal stresses of large-sized castings in solidification processes

When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large-sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings. Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique.

Numerical Simulation of 2D and 3D Sloshing Waves in a Regularly and Randomly Excited Container

In this paper,various aspects of the 2D and 3D nonlinear liquid sloshing problems in vertically excited containers have been studied numerically along with the help of a modified-transformation.Based on this new numerical algorithm,a numerical study on a regularly and randomly excited container in vertical direction was conducted utilizing four different cases： The first case was performed utilizing a 2D container with regular excitations.The next case examined a regularly excited 3D container with two different initial conditions for the liquid free surface,and finally,3D container with random excitation in the vertical direction.A grid independence study was performed along with a series of validation tests.An iteration error estimation method was used to stop the iterative solver（used for solving the discretized governing equations in the computational domain） upon reaching steady state of results at each time step.In the present case,this method was found to produce quite accurate results and to be more time efficient as compared to other conventional stopping procedures for iterative solvers.The results were validated with benchmark results.The wave elevation time history,phase plane diagram and surface plots represent the wave nonlinearity during its motion.

A Method of Obtaining Deformation Information by Tracing Deformation from Sections for 3D FE Simulation

With the development of computer technology and finite element method, the priority research area of plasticforming has focused on 3D FE simulation of forming processes for components with complicated geometrical shape.These processes have complex deforming mechanism, and different sections have different deforming characteristics.Therefore, for making a simple, convenient, and practical analysis of its deforming law, how to obtain deformationinformation of key sections from the results of 3D FE simulation has become one of problems urgently to be solved.So, a method of obtaining deformation information by tracing deformation from sections for 3D FE simulation hasbeen proposed. From the deformation information got by this method, the deformation law of key locations and thewhole deforming body can be obtained. This method can also help to compare the result from FE simulation withthat from physical modeling. Key procedures of this method have been presented in detail, and it has been testedby applying to 3D FE simulation of precision forging of the blade with a damper platform. The result shows thatthe method is practicable and reliable, and it can also be applied to 3D FE simulation of plastic forming processes ofother components.

3D simulation of near-fault strong ground motion: comparison between surface rupture fault and buried fault

In this paper, near-fault strong ground motions caused by a surface rupture fault （SRF） and a buried fault （BF） are numerically simulated and compared by using a time-space-decoupled, explicit finite element method combined with a multi-transmitting formula （MTF） of an artificial boundary. Prior to the comparison, verification of the explicit element method and the MTF is conducted. The comparison results show that the final dislocation of the SRF is larger than the BF for the same stress drop on the fault plane. The maximum final dislocation occurs on the fault upper line for the SRF; however, for the BE the maximum final dislocation is located on the fault central part. Meanwhile, the PGA, PGV and PGD of long period ground motions （≤ 1 Hz） generated by the SRF are much higher than those of the BF in the near-fault region. The peak value of the velocity pulse generated by the SRF is also higher than the BE Furthermore, it is found that in a very narrow region along the fault trace, ground motions caused by the SRF are much higher than by the BF. These results may explain why SRFs almost always cause heavy damage in near-fault regions compared to buried faults.

3D Modeling and Simulation of Fancy Fabrics in Weft Knitting

Weft knitted fancy fabrics are widely used in knitted garment design. Due to the complexity of the structures, their modeling and simulation needs to be solved in three-dimensional (3D) CAD developments. In this paper, 3D loop geometrical models of weft knitted fancy structures, including tuck stitch, jacquard stitch, transfer stitch and fleecy stitch, were developed based on an improved model of plain loop, and their central axes as some 3D space curves were achieved by using Non-Uniform Rational B-Splines (NURBS). The 3D visual simulation programme was written in C++ programming language using OpenGL, which was a function library of 3D graphics. Some examples of weft knitted fancy fabrics were generated and practical application of 3D simulation was discussed.

Analysis on nasal airway by using scale-adaptive simulation combined with standard κ-ω model and 3D printing modeling physical experiment

The physiological structure of the upper respiratory tract is complex and varies with each individual,and the circulating air has turbulent performance.In this paper,based on computed tomography(CT)medical images published online and the three-dimensional(3D)printing technology,a 3D model of the human upper respiratory tract was reconstructed and an experimental device of the upper respiratory tract was made.We implemented the respiratory experiment and measured the flow rate,and a scale-adaptive κ-ω model is applied for numerical simulation,the results are in good agreement.The flow field during respiratory was analyzed by coronal velocity cross section,vortex line and particle tracks.We found that the relatively strong shear effect happens at the areas of nasal valve and nasopharynx.In the middle and upper nasal tract,vortex line separation occurs and there is significant passage effect.The results indicate that SAS method is effective in studying upper respiratory airflow.