A novel box-counting method for quantitative fractal analysis of threedimensional pore characteristics in sandstone

Fractal theory offers a powerful tool for the precise description and quantification of the complex pore structures in reservoir rocks,crucial for understanding the storage and migration characteristics of media within these rocks.Faced with the challenge of calculating the three-dimensional fractal dimensions of rock porosity,this study proposes an innovative computational process that directly calculates the three-dimensional fractal dimensions from a geometric perspective.By employing a composite denoising approach that integrates Fourier transform(FT)and wavelet transform(WT),coupled with multimodal pore extraction techniques such as threshold segmentation,top-hat transformation,and membrane enhancement,we successfully crafted accurate digital rock models.The improved box-counting method was then applied to analyze the voxel data of these digital rocks,accurately calculating the fractal dimensions of the rock pore distribution.Further numerical simulations of permeability experiments were conducted to explore the physical correlations between the rock pore fractal dimensions,porosity,and absolute permeability.The results reveal that rocks with higher fractal dimensions exhibit more complex pore connectivity pathways and a wider,more uneven pore distribution,suggesting that the ideal rock samples should possess lower fractal dimensions and higher effective porosity rates to achieve optimal fluid transmission properties.The methodology and conclusions of this study provide new tools and insights for the quantitative analysis of complex pores in rocks and contribute to the exploration of the fractal transport properties of media within rocks.

3D Simulation of Storm Surge Disaster Based on Scenario Analysis

The occurrence of storm surge disaster is often accompanied with floodplain, overflow, dike breach and other complex phenomena, while current studies on storm surge flooding are more concentrated on the 1D/2D numerical simulation of single disaster scenario(floodplain, overflow or dike breach), ignoring the composite effects of various phenomena. Therefore, considering the uncertainty in the disaster process of storm surge, scenario analysis was firstly proposed to identify the composite disaster scenario including multiple phenomena by analyzing key driving forces, building scenario matrix and deducing situation logic. Secondly, by combining the advantages of k-ω and k-ε models in the wall treatment, a shear stress transmission k-ω model coupled with VOF was proposed to simulate the 3D flood routing for storm surge disaster. Thirdly, risk degree was introduced to make the risk analysis of storm surge disaster. Finally, based on the scenario analysis, four scenarios with different storm surge intensity(100-year and 200-year frequency) were identified in Tianjin Binhai New Area. Then, 3D numerical simulation and risk map were made for the case.

HEXAHEDRAL ELEMENT REFINEMENT FOR THE PREDICTION- CORRECTION ALE FEM SIMULATION OF 3D BULKINGFORMING PROCESS

Based on the characteristics of 3D bulk forming process, the arbitrary Lagrangian-Eulerian (ALE) formulation-based FEM is studied, and a prediction-correction ALE-based FEM is proposed which integrates the advantages of precisely predicting the boundary configuration of the deformed material, and of efficiently avoiding hexahedron remeshing processes. The key idea of the prediction-correction ALE FEM is elaborated in detail. Accordingly, the strategy of mesh quality control, one of the key enabling techniques for the 3D bulk forming process numerical simulation by the prediction-correction ALE FEM is carefully investigated, and the algorithm for hexahedral element refinement is formulated based on the mesh distortion energy.

Research on Clothing Simulation Design Based on Three-Dimensional Image Analysis

Traditional clothing design models based on adaptive meshes cannot reflect.To solve this problem,a clothing simulation design model based on 3D image analysis technology is established.The model uses feature extraction and description of image evaluation parameters,and establishes the mapping relationship between image features and simulation results by using the optimal parameter values,thereby obtaining a three-dimensional image simulation analysis environment.On the basis of this model,by obtaining the response results of clothing collision detection and the results of local adaptive processing of clothing meshes,the cutting form and actual cutting effect of clothing are determined to construct a design model.The simulation results show that compared with traditional clothing design models,clothing simulation design based on 3D image analysis technology has a better effect,with the definition of fabric folds increasing by 40%.More striking contrast between light and dark,the resolution increasing by 30%,and clothing details getting a more real manifestation.

Dynamic response analysis of liquefiable ground due to sinusoidal waves of different frequencies of shield construction

Vibration induced by shield construction can lead to liquefaction of saturated sand.Based on FLAC3D software,a numerical model of tunnel excavation is established and sinusoidal velocity loads with different frequencies are applied to the excavation face.The pattern of the excess pore pressure ratio with frequency,as well as the dynamic response of soil mass under different frequency loads before excavation,is analyzed.When the velocity sinusoidal wave acts on the excavation surface of the shield tunnel with a single sand layer,soil liquefaction occurs.However,the ranges and locations of soil liquefaction are different at different frequencies,which proves that the vibration frequency influences the liquefaction location of the stratum.For sand-clay composite strata with liquefiable layers,the influence of frequency on the liquefaction range is different from that of a single stratum.In the frequency range of 5-30 Hz,the liquefaction area and surface subsidence decrease with an increase in vibration frequency.The research results in this study can be used as a reference in engineering practice for tunneling liquefiable strata with a shield tunneling machine.

Stochastic analysis of excavation-induced wall deflection and box culvert settlement considering spatial variability of soil stiffness

In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.

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.

2D-3D registration for 3D analysis of lower limb alignment in a weight-bearing condition

X-ray imaging is the conventional method for diagnosing the orthopedic condition of a patient. Computerized Tomography(CT) scanning is another diagnostic method that provides patient’s 3D anatomical information. However, both methods have limitations when diagnosing the whole leg; X-ray imaging does not provide 3D information, and normal CT scanning cannot be performed with a standing posture. Obtaining 3D data regarding the whole leg in a standing posture is clinically important because it enables 3D analysis in the weight bearing condition.Based on these clinical needs, a hardware-based bi-plane X-ray imaging system has been developed; it uses two orthogonal X-ray images. However, such methods have not been made available in general clinics because of the hight cost. Therefore, we proposed a widely adaptive method for 2 D X-ray image and 3D CT scan data. By this method, it is possible to threedimensionally analyze the whole leg in standing posture. The optimal position that generates the most similar image is the captured X-ray image. The algorithm verifies the similarity using the performance of the proposed method by simulation-based experiments. Then, we analyzed the internal-external rotation angle of the femur using real patient data. Approximately 10.55 degrees of internal rotations were found relative to the defined anterior-posterior direction. In this paper, we present a useful registration method using the conventional X-ray image and 3D CT scan data to analyze the whole leg in the weight-bearing condition.

Structural Mechanics Analysis Using an FE-Mesh Adaption to Real, 3D Surface Detected Geometry Data

Within today＇s product development process, various FE-simulations （finite element） for the functional validation of the desired characteristics are made to avoid expensive testing with real components. Those simulations are performed with great effort for discretization, use of simulations conditions, like taking different non-linearities （i.e., material behavior, etc.） into account, to create meaningful results. Despite knowing the effects of deformations occurring during the production processes, always the non-deformed design model of a CAD-system （computer aided design） is used for the FE-simulations. It seems rather doubtful that further refinement of simulation methods makes sense, if the real manufactured geometry of the component is not considered for in the simulation. For an efficient exploit of the potential of simulation methods, an approach has been developed which offers a geometry model for simulation based on the existing CAD-model but with integrated production deviations as soon as a first prototype is at hand by adapting the FE-mesh to the real, 3D surface detected geometry.

大型高架桥无支架盖梁施工过程模板受力特性的3D-FEM模拟分析

以上海S32高速公路闵浦大桥西侧引桥段的盖梁施工为例,通过合理的边界条件处理,基于ABAQUS有限元分析软件建立了复杂结构的3D-FEM模型,并以混凝土弹性模量和泊松比的变化模拟实际施工,进而分析无支架盖梁的受力状态.计算结果与现场实测的结果基本吻合,为无支架盖梁施工技术的研究分析提供了参考方法.研究表明:混凝土浇注完成约10 h左右,即具有90%的设计强度,基本能承受自身重力荷载,盖梁的竖向及横向荷载逐渐向混凝土转移;同时,该时间的确定为现场确定拆模时间、提高施工进度提供了依据.

Three-Dimensional Visual Analysis for Construction Layout of Reservoir Project

It is difficult to analyze the inter-relationship for the construction layout of a reservoir project scientifically and intuitively.According to the characteristics of broad field and huge information,the modeling methods of digital terrain and solid model as well as the techniques of texture mapping and scene navigation are adopted.The simulation system is developed by C program language,which includes the functions of the interactive navigation of 3D scene,the visual inquiry of project digital model information,the storage and management of project information.A certain reservoir is taken as a case.The 3D visual analysis for the construction layout and engineering information are obtained.The proposed system is of great advantages in dealing with large amount of information and the method provides a theoretical basis and technical support for the construction layout of a reservoir project.

DEFORM-3D软件在叶片锻坯结构形式选取中的应用

在叶片锻造过程中,由于变形量大,锻出的叶片会出现如褶皱、裂纹这样的缺陷。为了提高生产效率,一般要求在螺旋压力机上一次锻造成形。因此,采用合理的毛坯结构形式在最小成形载荷下来获得最低程度的缺陷就显得十分重要。常规用来选择叶片锻坯合理结构形式的方法有诸多缺点,采用有限元方法将会在很大程度上弥补这些不足。

Application of 3D stereoscopic visualization technology in casting aspect

3D stereoscopic visualization technology is coming into more and more common use in the field of entertainment,and this technology is also beginning to cut a striking figure in casting industry and scientific research.The history,fundamental principle,and devices of 3D stereoscopic visualization technology are reviewed in this paper.The authors’research achievements on the 3D stereoscopic visualization technology in the modeling and simulation of the casting process are presented.This technology can be used for the observation of complex 3D solid models of castings and the simulated results of solidification processes such as temperature,fluid flow,displacement,stress strain and microstructure,as well as the predicted defects such as shrinkage/porosity,cracks,and deformation.It can also be used for other areas relating to 3D models,such as assembling of dies,cores,etc.Several cases are given to compare the illustration of simulated results by traditional images and red-blue 3D stereoscopic images.The spatial shape is observed better by the new method.The prospect of3D stereoscopic visualization in the casting aspect is discussed as well.The need for aided-viewing devices is still the most prominent problem of 3D stereoscopic visualization technology.However,3D stereoscopic visualization represents the tendency of visualization technology in the future;and as the problem is solved in the years ahead,great breakthroughs will certainly be made for its application in casting design and modeling and simulation of the casting processes.

基于ABAQUS的平纹织物同面对向弯曲有限元模拟

为明晰织物结构对其弯曲性能的影响机制,对织物弯曲过程进行了有限元模拟和实验验证。以涤纶织物为例,通过VHX-5000型超景深数码显微镜观测织物,得到纱线几何参数;根据纱线实际尺寸,利用SolidWorks专业建模软件构建涤纶平纹织物的三维几何模型;基于有限元分析软件ABAQUS研究织物同面对向弯曲性能,分析纱线弹性模量、摩擦因数、泊松比等参数对弯曲实验的影响,并将有限元仿真结果与实验结果进行对比。结果表明:模拟所得抗弯力-位移曲线与实验曲线在0.01水平上呈显著相关,模拟结果与实验结果一致,证明用有限元模拟弯曲织物模型的有效性。

复杂断块构造的地应力场研究——以海拉尔盆地贝尔凹陷希3断块为例

根据贝尔凹陷希3断块的井孔崩落资料以及差应变和波速各向异性法得到的地应力测量数据,采用有限元约束优化反演法,对希3断块的三维地应力场进行了模拟,探讨了断层对地应力场的影响以及断块构造的地应力分布特征.研究结果表明:断层附近的地应力分布主要受邻近断层的影响,且与扰乱程度、断层的几何尺寸和距离断层的远近等因素相关.不同类型断层的纵向延伸加剧了纵向上地应力场分布的复杂性.这一现象在单断式断块油气藏有所体现,在双断式、三断式以及断阶式断块油气藏中表现得尤为突出;断层对应力方向的扰动作用在弹性模量高的硬地层中更为剧烈.离散"点"的实测值不能全面反映断块构造应力场全貌,三维数值模拟是断块油气藏地应力场定量分析的有效手段.

电磁发射复合型结构拦截弹的3维电磁场有限元建模与仿真

为了达到拦截弹的连续发射、提高拦截效果和加固驱动线圈的目的,提出了一种复合型结构的拦截弹。在建立数学模型时,基于麦克斯韦方程组,对非铁磁材料区域、铁磁材料区域、空间区域等求解区采用矢量磁位和标量磁位来描述3维电磁场,并采用Ansoft有限元分析软件中的MAXWELL3D模块对新型结构拦截弹的电磁场和涡流场分布情况进行了仿真研究。通过对仿真结果的分析发现,使用了铁磁材料的拦截弹具有其它类型电磁发射弹丸所不具备的磁场分布特点:感应层与驱动线圈之间为斥力,屏蔽层与驱动线圈之间为吸力。这使得实现了一体化设计的拦截弹不仅可以满足连续发射的需要,而且还提高了拦截效果,同时对驱动线圈起到了加固作用。

基于CAD/CAE/CAM技术的按键注塑模具设计

分析了按键结构特点,以Moldflow为工具,对按键的注塑成型过程进行CAE模拟分析,确定了模具的浇注系统以及冷却系统。在模拟分析的基础上运用Pro/E软件完成了模具的三维分模,将Pro/E中提取的加工信息,导入到MasterCAM软件中进行模具零件的数控自动编程和模拟加工。与传统的注塑模具设计方法相比,基于CAD/CAE/CAM技术提高了模具设计的效率,缩短了模具设计和制造周期,降低了成本。

基于Pro/E和ADAMS的牛头刨床导杆机构仿真分析

阐述了牛头刨床导杆机构在Pro/E环境中建模和ADAMS环境中运动仿真过程。通过对机构中滑枕的速度和加速度曲线分析,说明了滑枕在工作阶段运行平稳,返回阶段速度较快。分析了导杆的摆角曲线,计算了机构的行程速比系数,说明了机构存在急回特性。另外分析了驱动的平衡力矩和功率曲线,结果表明,由于返回阶段速度较快,所需的驱动力矩及功率的损耗相应增加,运动参数符合刨床的工作特点,机构设计合理。

ADSS光缆与高压输电线路同杆并架全程三维电场分析与光缆挂点优化设计软件

详细给出了沿高压输电线路加挂ADSS光缆时电场的空间三维计算原理。为了优化计算,提出了线电荷与点电荷相结合的等效电荷法。在此基础上编制了分析输电线路任意截面及沿ADSS光缆走向的电位、场强分布的三维计算软件。此外,该程序还能考虑转角、换位、舞动等工况。对不同塔型的计算结果表明:软件中采用的算法合理,所得结果对ADSS的挂点选择和优化具有参考价值。

激光冷却铬原子的3维仿真分析

为了研究铬原子在激光冷却场中的3维表现形式,分析和探讨了铬原子与激光冷却场的相互作用过程,并基于半经典理论的多普勒力和偏振梯度冷却力的3维特性,采用4阶龙格-库塔算法模拟铬原子的3维运动轨迹,同时得到了铬原子的3维落点分布状态,当铬原子束经过激光冷却场后,其发散角变小,速率降低。结果表明,铬原子3维仿真结果与2维情况下的铬原子分布相吻合,并且能提供更全面和丰富的冷却信息。