Three-dimensional discrete element numerical simulation of Paleogene salt structures in the western Kuqa foreland thrust belt

Taking the Paleogene salt strata in the west of Kuqa foreland thrust belt as study object, the deformation features of salt structure in the compression direction and perpendicular to the compression direction were examined to find out the control factors and formation mechanisms of the salt structures. By using the three-dimensional discrete element numerical simulation method, the formation mechanisms of typical salt structures of western Kuqa foreland thrust belt in Keshen and Dabei work areas were comprehensively analyzed. The simulation results show that the salt deformation in Keshen and Dabei work areas is of forward spread type, with deformation concentrated in the piedmont zone;the salt deformation is affected by the early uplift near the compression end, pre-existing basement faults, synsedimentary process and the initial salt depocenter;in the direction perpendicular to the compression direction, salt rocks near the compression end have strong lateral mobility with the velocity component moving towards the middle part, and the closer to the middle, the larger the velocity will be, so that salt rocks will aggregate towards the middle and deform intensely, forming complex folds and separation of salt structures from salt source, and local outcrop with thrust faults. Compared with 2 D simulation, 3 D simulation can analyze salt structures in the principal stress direction and direction perpendicular to the principal stress, give us a full view of the formation mechanisms of salt structures, and guide the exploration of oil and gas reservoirs related to salt structures.

Three-Dimensional Thermo-Elastic-Plastic Finite Element Method Modeling for Predicting Weld-Induced Residual Stresses and Distortions in Steel Stiffened-Plate Structures

The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber

Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.

Parametric study on single shot peening by dimensional analysis method incorporated with finite element method

Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and re- sistance to corrosion fatigue, cracking, etc. Compressive re- sidual stress and dent profile are important factors to eval- uate the effectiveness of shot peening process. In this pa- per, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimensionless relations of pro- cessing parameters that affect the maximum compressive residual stress and the maximum depth of the dent were de- duced by dimensional analysis method. Secondly, the in- fluence of each dimensionless parameter on dimensionless variables was investigated by the finite element method. Fur- thermore, related empirical formulas were given for each di- mensionless parameter based on the simulation results. Fi- nally, comparison was made and good agreement was found between the simulation results and the empirical formula, which shows that a useful approach is provided in this pa- per for analyzing the influence of each individual parameter.

Rock bridge slice element method in slope stability analysis based on multi-scale geological structure mapping

The searching method of failure surface which consists of complex geological structures in high and steep rock slopes was studied. Based on computer simulation technology and Monte-Carlo method, three dimensional multi-scale geological structures such as engineering scale and statistical scale structures of the slope were simulated. The searching method of failure route which consists of joints and rock bridges was determined via simulation annealing method by considering the shear strength of joints or rock bridges in one supposed route. When shear strengths of all the supposed routes were computed, the least shear strength route was considered failure route. Then, the inclined slice of joint slices and rock bridge slices were separated according to the position of joints and rock bridges. For the rock bridge slices, by distinguishing the failure model, the force direction to the next slice was defined. Finally, the limit equilibrium equations for every slice were established, and the slope stability factor was obtained. One practical example indicates that the discussed method is more closely to the real condition.

Stability and structural dimension of access mechanized panel

To acquire a knowledge of the stress-strain state in the process of mining beforehand, a numerical method was used to simulate the stoping process of access mechanized panel mining in No. 3 ore-body of Tonglushan mine; and for the sake of obtaining better stability, the optimal panel dimension and access stoping sequence were researched. The results show that the integral stability of the mechanized panel of No. 3 ore-body is passable in the process of winning at full level height; the stability of panel tends to be worse gradually with continuous increasing of panel width; and the better width of access panel in No.3 ore-body is less than 52 m. It is indicated that 3D elasto-plastic finite element method can make a satisfactory study of numerical simulation on the panel stability and its structural dimension in the test for the upward access mechanized-panel mining. The results of the theoretical calculation and analysis accord with the actual situation from the field ground pressure monitoring.

Pseudo-beam method for compressive buckling characteristics analysis of space inflatable load-carrying structures

This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.

Numerical Analysis of the Adhesive Forces in Nano-Scale Structure

Nanohairs, which can be found on the epidermis of Tokay gecko＇s toes, contribute to the adhesion by means of van der Waals force, capillary force, etc. This structure has inspired many researchers to fabricate the attachable nano-scale structures. However, the efficiency of artificial nano-scale structures is not reliable sufficiently. Moreover, the mechanical parameters related to the nano-hair attachment are not yet revealed qualitatively. The mechanical parameters which have influence on the ability of adhesive nano-hairs were investigated through numerical simulation in which only van der Waals force was considered. For the numerical analysis, finite element method was utilized and van der Waals force, assumed as 12-6 Lennard-Jones potential, was implemented as the body force term in the finite element formulation.

Finite Element Simulation of the Polymeric Liquid Flow in Coat-hanger Die

A three - dimenslonal finite element model is developed to deal with the polymeric liquid flow in coat - hanger die. This model is used to predict the flow behavior of the 2％ CMC/watsr solution in the coat - hanger die with linearly taper manifolds and its validity is experimentally verified quantitatively and qualitatively by using Laser Doppler Velocimetry and Particle Image Velocimetry respectively.

某高层剪力墙结构不均匀沉降分析及处理

无新增荷载情况下的持续不均匀沉降常常发生在地基有缺陷的高层建筑中,该类沉降产生的破坏是缓慢持续的。地基不均匀沉降会导致建筑物开裂、倾斜,进一步发生结构安全事故。依据某高层剪力墙结构以及不均匀沉降监测数据,采用ABAQUS建立该高层剪力墙结构三维有限元计算模型,分析不均匀沉降工况下上部结构的内力分布及整体变形发展规律。结果显示,有限元计算得到的模型内力增大位置与实际外墙主要开裂位置相吻合,整体沉降变形发展规律与现场实测数据基本一致,证明上部结构三维有限元模型的可行性。进一步建立剪力墙结构-桩筏基础-地基耦合计算模型,开展不同筏板厚度对整体结构不均匀沉降的影响分析。同时结合实际案例制定“增设筏板+补桩”处理方法,加固完成后监测数据显示房屋处于稳定状态,变形与裂缝均无发展。

严寒地区拱坝溢流表孔三维有限元数值模拟分析

溢流表孔作为拱坝重要的泄水建筑物,对大坝安全运行具有重要的作用。以某拱坝溢流表孔为例,该表孔地处高纬度严寒地区、结构复杂且地震烈度高,通过三维有限元法对表孔在不同工况下的静、动力应力进行计算分析,根据计算结果,对表孔结构进行配筋设计,确定受拉钢筋的布置方式及配筋量,使表孔结构钢筋布置满足承载力及正常使用要求。研究结果可为类似工程配筋设计提供参考依据。

建立基于浸入边界有限元法的三维静脉瓣流固耦合数值模型

目的 探究静脉内血液与瓣膜之间的流固耦合动态过程和保证血液单向回流的生理机制。方法 基于浸入边界有限元法,结合人体下肢静脉医学图像及牛大隐静脉的解剖结构和尺寸,采用超弹性本构模型描述静脉瓣膜在生理条件下不可压缩、非线性和超弹性力学响应,构建静脉血管和静脉瓣膜的三维数值模型。结果 研究结果可视化地展示静脉动态运输血液的过程以及静脉瓣膜防止反流的功能机制,再现静脉内瓣膜运动和血液流动的周期性特点,讨论和量化了整个心动周期内的重要生理数据,包括静脉内血液的压力、流速和流量以及静脉瓣膜的开口面积、静脉瓣膜表面的应力和应变分布等。结论 三维流固耦合模型可数值再现静脉内生理动态过程,为进一步揭示静脉疾病相关机制提供重要的参考和指导意义。

“流空间”视角下西北地区城市群内部网络空间结构及其驱动机制

运用社会网络分析和ArcGIS空间分析方法,从交通、经济、人口等多要素流视角分析西北地区城市群网络的层级结构、联系格局与子群特征,借助二次指派程序回归分析方法剖析多元网络结构的影响机制.结果表明,网络中心性地区差异显著,且重心位于东翼.交通网络差异相对较小,呈单中心结构,经济网络规模分布最为集中,呈双中心结构,人口网络规模分布相对分散,呈多中心结构;城市联系表现出“东密西疏”的空间网络格局,且等级性显著.交通网络呈带状组团结构,经济网络呈中心辐射状结构,人口网络呈以省会为主的蜂房状多中心结构;网络内部均存在小团体.交通网络子群构成与联系凸显干线的串联带动作用,经济网络择优链接效应明显,人口网络受行政区划约束;地理邻近、交通可达性和经济发展是产生网络共性的主要因素,企业成长、产业结构和社会服务是网络差异性的主要贡献者.

塔里木盆地塔中地区奥陶系构造-沉积模式与碳酸盐岩裂缝储层预测

奥陶系碳酸盐岩是塔中地区油气勘探的重要目的层。本文在讨论塔中地区奥陶纪区域构造背景和奥陶系岩性段划分的基础上 ,建立了塔中地区奥陶系构造 -沉积模式 ,并用三维有限元数值模拟方法对塔中地区有利碳酸盐岩裂缝储层发育区进行了预测 ,以期指导塔中地区碳酸盐岩的油气勘探。

VI族元素修饰对二维AlN电子性质影响的第一性原理研究

采用密度泛函理论的第一性原理计算方法,研究了VI族元素(O、S、Se、Te)修饰对二维AlN电子性质的影响。计算结果表明,O修饰后,二维AlN体系的能带发生劈裂,从而转变为磁性材料;S、Se和Te修饰后,二维AlN电子态密度曲线自旋向上和自旋向下完全对称,形成了非磁性结构。从态密度图可以看出,费米能级附近的态密度主要由修饰原子的p态电子和N原子的p态电子贡献,导带底部逐渐向低能区移动,导致二维AlN的吸收波长阈值从紫外线区域向可见光移动。因此,修饰的二维AlN光催化效率提高,并有应用于可见光响应的光电子和自旋电子器件的可能。

Characterization and Three-dimensional Structural Modeling of Humic Acid via Molecular Mechanics and Molecular Dynamic Simulation

The humic acid（HA） sample obtained from the alluvial soil was characterized by elemental composition, pyrolysis gas chromatography-mass spectrometry（Py-GC-MS） and solid-state 13C nuclear magnetic resonance （13C NMR） spectroscopy. There is high fat content and a few nitrogen-containing functional groups in HA. Py-GC-MS demonstrates the characterization and structural identification of HA. One long list of identified pyrolysis products was proposed for the construction of conceptual model of HA. Solid-state 13C NMR data indicate there are higher values of alkyl-C, O-alkyl-C and aryl-C in HA. The elemental composition, structural carbon distribution and L3C NMR spectroscopy of simulated HA are consistent with those of experimental HA. HyperChem was used to simulate the three-dimensional molecular structure of the monomer, which was optimized by the molecular mechanics of the optimized potential for liquid simulations（OPLS） force field and molecular dynamics simulation to get the stable and balanced conformation. The deprotonation process study depicts that the degree of ionization of HA gets deeper, while the electronegativity of HA and the energy of van der Waals（vdW） increase. Moreover, the 3D structure of humic acid with -4 charges is the most stable. The deprotonation process is an endothermic process.

星载二维转台U型架结构轻量化与优化设计

星载二维转台是空间相机等光电设备的主要承载机构,U型架是转台的关键支撑部件。为了对星载二维转台U型架进行结构优化与轻量化设计,研制高承载比和轻量化的星载二维转台,本文设计了一种用于星载二维转台的碳纤维复合材料U型架。首先,利用碳纤维复合材料代替钛合金材料,结合考虑工艺性,设计了一种变截面管状结构U型架。接着,按照基于铺层工艺的有限元建模方法对碳纤维U型架进行有限元建模与仿真分析。然后,试制U型架样机并通过模态试验验证有限元模型的准确性。最后,提出一种理论分析法、遗传算法、有限元法相结合的三级优化方法对碳纤维U型架铺层角度、铺层厚度与铺层顺序进行优化设计。结果表明:模态试验与仿真得到的U型架振型完全一致,频率相差在5%以内。初始设计的碳纤维U型架比钛合金U型架质量减少了45.7%,通过对复合材料铺层的优化设计,使U型架质量进一步减少了13.8%,固有频率提升了10.14%。本文所采用的复合材料建模与优化方法正确,设计的碳纤维U型架满足星载二维转台轻量化设计需求。

电阻式柔性触觉传感器的研究与医养健康领域应用现状

近年来,可穿戴智能系统的进步对柔性压力传感器提出迫切的需求。其中,电阻式柔性触觉传感器因其原理简单、易于加工、集成效率高等特点得到了迅速发展。但是,如何实现传感器在宽压力监测范围内,具有高灵敏度仍是研究者们要面临的挑战。为了解决上述问题,除了选择先进的功能材料和合适的衬底材料,优化传感器结构也是一个重要的研究方向。本文立足于传感器件的结构设计,分别介绍了一维的纤维纱线传感器件,基于表面微结构、纳米结构构筑的二维平面传感器件及具有空间结构和高空隙的多维立体结构传感器件,通过以上结构设计实现了传感器件性能的提升,最后分析了其在医养健康领域的实际应用进展。

三维水-土耦合模型在深基坑降水计算中的应用

在广泛分析前人有关本课题研究资料的基础上,对三维水–土耦合模型在深基坑降水计算中的应用进行了研究,并以武汉市中山广场地下过街通道降水工程为例,对其降水过程进行了三维有限元计算。通过对该工程的三维有限元分析表明,三维数值模拟方法能够很好地模拟基坑降水中防渗帷幕、非均质和各向异性等一系列解析法难以处理的实际工程条件。因此,在深基坑降水及其引起地面沉降的计算中,运用数值模拟方法具有重要的现实意义。