Analysis of Three-dimensional Crack Propagation by Using Displacement Discontinuity Method

A technique for modelling of three-dimensional(3D)quasi-statically propagating cracks in elastic bodies by the displacement discontinuity method(DDM)was described.When the crack is closed,the Mohr-coulomb rule on the two contacted surfaces of the crack must be satisfied.A simple iterative method was adopted in order to consider three different states of cracks.Under the assumption that the advance of the point on the crack front would occur only in the normal plane which is through this edge point,the maximum energy release rate criterion is modified to be used as the criterion for the crack growth.With discretization,the process of crack propagation can be seen as the advance of the vertices of the crack front.The program MCP3D was developed based on these theories to simulate the 3D quasi-static crack propagation.A numerical example of a penny-shaped crack subject to tension and compression in an infinite elastic media was analyzed with MCP3D,and the results in comparison with others' show that the present method for 3D crack propagation is effective.

Autologous nerve graft repair of different degrees of sciatic nerve defect:stress and displacement at the anastomosis in a three-dimensional finite element simulation model

In the repair of peripheral nerve injury using autologous or synthetic nerve grafting, the mag- nitude of tensile forces at the anastomosis affects its response to physiological stress and the ultimate success of the treatment. One-dimensional stretching is commonly used to measure changes in tensile stress and strain; however, the accuracy of this simple method is limited. There- fore, in the present study, we established three-dimensional finite element models of sciatic nerve defects repaired by autologous nerve grafts. Using PRO E 5.0 finite element simulation software, we calculated the maximum stress and displacement of an anastomosis under a 5 N load in 10-, 20-, 30-, 40-mm long autologous nerve grafts. We found that maximum displacement increased with graft length, consistent with specimen force. These findings indicate that three-dimensional finite element simulation is a feasible method for analyzing stress and displacement at the anas- tomosis after autologous nerve grafting.

Study on Injection-Production System Adjustment of Fault Block Reservoir Based on Equilibrium Displacement

This paper proposed a method of injection-production system adjustment to solve the problem that the water flooding effect was restricted because of the horizontal and vertical contradictions during the development process of fault block reservoirs. Considering the heterogeneity of reservoir, the Buckley-Leverett water flooding theory was applied to establish the relationship between the recovery and cumulative water injection. In order to achieve the goal of vertically balanced recovery of each section, the calculation method of vertical sectional injection allocation was proposed. The planar triangular seepage unit was assumed and sweep coefficients of different oil-water distribution patterns were characterized using multi-flow tube method. In order to balance and maximize the plane sweep coefficient, the calculation method of plane production system optimization was obtained. Then the injection-production system stereoscopic adjustment method based on equilibrium displacement was proposed with vertical sectional injection allocation and plane production system optimization. This method was applied to injection and production adjustment of BZ oilfield in southern Bohai. The effect of water control and oil increase was obvious. This method can greatly improve the effect of water flooding of offshore fault block reservoirs with the adjustment of injection-production system.

A structural topological optimization method for multi-displacement constraints and any initial topology configuration

In density-based topological design, one expects that the final result consists of elements either black （solid material） or white （void）, without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multidisplacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.

Study of the mechanisms of streamline-adjustment-assisted heterogeneous combination flooding for enhanced oil recovery for post-polymer-flooded reservoirs

Streamline-adjustment-assisted heterogeneous combination flooding is a new technology for enhanced oil recovery for post-polymer-flooded reservoirs.In this work,we first carried out a series of 2D visualization experiments for different chemical flooding scenarios after polymer flooding.Then,we explored the synergistic mechanisms of streamline-adjustment-assisted heterogeneous combination flooding for enhanced oil recovery and the contribution of each component.Test results show that for single heterogeneous combination flooding,the residual oil in the main streamline area after polymer flooding is ready to be driven,but it is difficult to be recovered in the non-main streamline area.Due to the effect of drainage and synergism,the streamline-adjustment-assisted heterogeneous combination flooding diverts the injected chemical agent from the main streamline area to the non-main streamline area,which consequently expands the active area of chemical flooding.Based on the results from the single-factor contribution of the quantitative analysis,the contribution of temporary plugging and profile control of branched preformed particle gels ranks in the first place and followed by the polymer profile control and the effect of streamline adjustment.On the contrary,the surfactant contributes the least to enhance the efficiency of oil displacement.

Three-dimensional finite element analysis on effects of tunnel construction on nearby pile foundation

A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.

The relationship between three-dimensional coseismic displacement and distribution of coseismic landslides

In mountainous areas,landslides induced by destructive earthquakes are one of the main causes of human casualties,which is an important link in the chain of earthquake hazards.Earthquake-triggered landslides are mainly controlled by three factors,namely seismic property,topography,and geology.Many studies have been conducted on these controlling factors of earthquake-triggered landslides.However,little is known about the effect of coseismic displacement on the distribution of landslides under different slope aspects and slope angles,hindering our understanding of the mechanism of inducing landslides by the combination of surface displacement and slope geometry at the local scale and leading to controversial opinions about the abnormal number of earthquake-triggered landslides in several cases.Here,we took the 2008 Wenchuan M_(w) 7.9 earthquake in China,the 2015 Gorkha M_(w) 7.8 earthquake in Nepal,and the 2016 Kaikōura M_(w) 7.8 earthquake in New Zealand as examples to investigate the relationship between the distribution of large earthquake-triggered landslides and the three-dimensional (3D)coseismic displacement field.We divided the landslide-prone area around the epicenter into regular grids and calculated the 3D coseismic displacement in each grid according to the radar satellite images and slip distribution model.Then,the 3D coseismic displacement was projected to two coordinate systems related to the slope where the landslides were located for statistical analysis.We determined that the surface uplift perpendicular to the slope is more likely to induce landslides,particularly when combined with large slope angles.Meanwhile,the number of landslides will be significantly reduced where the subsidence occurs.Regardless of uplift or subsidence,landslides are more likely to occur when the direction of coseismic horizontal displacement is far from the slope.The larger the slope angles are,the greater the effects of horizontal displacement and slope aspect.A dominant slope aspect also exists for earthquake-triggered landslides,which is different from the mean slope aspect calculated from the background topography.This dominant aspect angle is related to the focal mechanism and striking angle of surface rupture.These results indicate that we can simulate the 3D coseismic displacement field from known fault location and earthquake mechanism and combine the topographic data for landslide risk assessment in earthquake-prone mountainous areas to minimize the damage caused by possible earthquake-triggered landslides.

新型三轴调节式定位器辅助经皮椎间孔镜手术治疗多节段腰椎间盘突出症效果及初步随访

目的探讨新型三轴调节式定位器辅助经皮椎间孔镜手术(percutaneous transforaminal endoscope discectomy,PTED)治疗多节段腰椎间盘突出症(lumber disc herniation,LDH)效果及随访结果。方法选取我院100例多节段LDH患者,简单随机化法分组,各50例。对照组行传统PTED,观察组行新型三轴节式定位器辅助PTED。观察对比2组围术期指标、并发症、手术优良率及手术前后炎症应激指标[白细胞介素2(interleukin-2,IL-2)、白细胞介素6(interleukin-6,IL-6)、白细胞介素17(interleukin-17,IL-17)]、患侧多裂肌表面肌电图[均方根值(root mean square,RMS)、中位频率值(median frequencyMF)、积分肌电值(integrated EMG,IEMG)]、Oswestry功能障碍指数问卷表(Oswestry dysfunction index,ODI)评分、视觉模拟评分法(visual analogue scale,VAS)评分及手术优良率。结果观察组透视次数、穿刺次数、术中出血量少于对照组,穿刺时间、手术时间短于对照组,一次性穿刺成功率高于对照组(P<0.05);2组并发症发生率比较差异无统计学意义(P>0.05);术后1 d观察组血清IL-17、IL-6、IL-2水平低于对照组(P<0.05);术后1个月、3个月、6个月、12个月2组患侧多裂肌RMS、MF、IEMG均高于术前,ODI评分均低于术前(P<0.05);术后1 d、5 d观察组腰背部、下肢VAS评分低于对照组(P<0.05);术后12个月2组手术优良率比较,差异无统计学意义(P>0.05)。结论新型三轴调节式定位器辅助PTED与传统PTED治疗多节段LDH均能取得满意效果,能改善患侧多裂肌表面肌电图,恢复腰椎功能,缓解患者疼痛,且具有较好安全性,但前者能优化手术操作,缩短手术时间,减轻术后炎症反应,有助于早期疼痛缓解。

气承式膜结构煤棚调整内压下的实测位移响应分析

随着气承式膜结构煤棚跨度和单体面积的增加,内压分布特征的变化复杂。目前缺乏针对大型项目的内压升降与位移响应变化关系的实测验证,以确定结构位移响应理论计算值与实测数据是否吻合。基于布设在浙江乐清电厂115m×317m的气承式膜结构煤棚的健康监测系统,在台风来临前对结构进行了升降压-保压测试。实测了结构7个不同测点的位移响应,分析了调整内压时结构的位移响应特征。同时,将实测结果与数值模拟结果进行对比分析,验证了对于大跨度气承式膜结构基于压力等效分析方法的可靠性。

基于光束偏转法的原子力显微镜探针一致性装配系统研究

为解决原子力显微镜(Atomic Force Microscope,AFM)系统更换探针后光路调整复杂耗时、精度不足的问题,本文首次提出通过精密控制探针与探针夹装配位置来实现更换的探针相对AFM系统原光路位置的一致,进而实现免去AFM系统换针后调整光路步骤。该系统的光路一致性组件采用光束偏转法对探针位置与偏转进行放大与监测,并使用高精度位移与角度调节平台进行探针相对于探针夹的方位调整。通过实物搭建对探针一致性效果进行了验证,并对紫外光(Ultraviolet,UV)胶水固化过程导致探针位置偏移影响;探针不同偏移量时产生的探测器噪音对AFM系统成像质量影响进行了系统分析。实验结果表明:经由该系统装配的探针平均位置精度接近1.1μm;并且在AFM系统中更换一致性探针仅需8 s。该系统实现了高精度且质量稳定的探针一致性装配,极大地简化了AFM系统重新校准光路的操作步骤,其与自动换针装置配合可有效提升工业计量型AFM的操作与测量性能。

带低屈服点钢耗能梁段高强钢框筒结构的结构影响系数和位移放大系数研究

在传统钢框筒结构的部分裙梁跨中处设置LYP225低屈服点钢耗能梁段,其余构件采用Q460高强度钢材,提出带低屈服点钢耗能梁段高强钢框筒结构(HSS-FTS-LSL)。在地震作用下耗能梁段发生剪切屈服耗散地震能量,梁、柱等构件由于采用高强钢从而保持弹性或部分进入塑性阶段。为了研究HSS-FTS-LSL的结构影响系数和位移放大系数,以楼层数、耗能梁段长度及布置方式为变量,按照我国规范设计了3组共8个HSS-FTS-LSL算例,并且考虑高阶振型的影响,采用分布侧向力调整法对各算例进行了Pushover分析,基于改进的能力谱法计算了8个算例的结构影响系数和位移放大系数,分析了结构层数、耗能梁段长度及布置方式对结构性能系数的影响并给出了建议取值。最后,根据提出的HSS-FTS-LSL抗震设计反应谱对其中一个结构算例进行重设计,并对重设计前后两个算例结构进行弹塑性分析,对比了二者的抗震性能以及用钢量,验证了本文提出的HSS-FTS-LSL结构影响系数建议值的合理性。

双吊机悬臂吊装四点起吊快速精调施工方法

基于钢箱梁节段4点起吊的力学平衡原理,根据吊装节段4点吊装状态的姿态平衡特性,提出分离纵坡与横坡2个正交变量的快速精调定位方法,确定精调施工先调整纵坡后调整横坡的正确操作顺序。工程实例应用于九江长江二桥江心侧的钢箱梁悬臂拼装施工匹配定位施工,节段就位误差小于2 mm,钢箱梁吊装合龙前桥梁线型的控制精度超过L/10000,梁段拼接无尖角,线型平顺。结合实际,给出了应用纵、横坡正交变量分离法精调宽大节段悬臂吊装施工注意事项。

基于动态反演的“双高”油田驱油效率研究及挖潜实践

“双高”开发阶段油田水淹程度强,剩余油呈现整体分散、局部富集的分布特点,开展剩余油潜力精准评价对该阶段调整挖潜意义重大。以矿场实际生产数据为基础,在极限驱油效率室内试验认识的基础上,综合考虑矿场典型井网模式、水淹厚度、采出程度和含水率等因素,建立矿场级别下极限驱油效率动态反演数学模型,定量计算典型井网模式极限驱油效率。研究结果表明:1)原油黏度不同,驱油效率有差异,原油黏度为50 mPa·s时,驱油效率可达68%,原油黏度为300 mPa·s时,驱油效率可达62%;2)井网模式不同,驱油效率变化规律差异较大,结合SZ油田开发实际,定向井网极限驱油效率可达48%,水平井-定向井联合井网驱油效率可达61%~68%。SZ油田驱油效率仍有大幅提高空间,后续可通过调整井网进一步提高驱油效率。该研究成果考虑黏度差异的影响,定量评价高含水期油田井网调整对提高驱油效率的影响,为SZ油田潜力评价提供了指导,同时也为其他相同开发阶段油田提供借鉴。

采煤机行程传感调高液压缸的研制

根据井下工况特点,研制了一种适用于采煤机的行程传感调高液压缸,介绍了传感器全内置的安装结构和行程测量原理,建立了采高测量模型及其控制系统,指出了行程传感液压缸的性能特点和优势,经现场使用验证,可有效提升采高监测的准确性和可靠性。

Inferring three-dimensional surface displacement field by combining SAR interferometric phase and amplitude information of ascending and descending orbits

Conventional Interferometric Synthetic Aperture Radar(InSAR) technology can only measure one-dimensional surface displacement(along the radar line-of-sight(LOS) direction).Here we presents a method to infer three-dimensional surface displacement field by combining SAR interferometric phase and amplitude information of ascending and descending orbits.The method is realized in three steps:(1) measuring surface displacements along the LOS directions of both ascending and descending orbits based on interferometric phases;(2) measuring surface displacements along the azimuth directions of both the ascending and descending orbits based on the SAR amplitude data;and(3) estimating the three-dimensional(3D) surface displacement field by combining the above four independent one-dimensional displacements using the method of least squares and Helmert variance component estimation.We apply the method to infer the 3D surface displacement field caused by the 2003 Bam,Iran,earthquake.The results reveal that in the northern part of Bam the ground surface experienced both subsidence and southwestward horizontal movement,while in the southern part uplift and southeastward horizontal movement occurred.The displacement field thus determined matches the location of the fault very well with the maximal displacements reaching 22,40,and 30 cm,respectively in the up,northing and easting directions.Finally,we compare the 3D displacement field with that simulated from the Okada model.The results demonstrate that the method presented here can be used to generate reliable and highly accurate 3D surface displacement fields.

Effect of proximal contact strength on the three-dimensional displacements of implant-supported cantilever fixed partial dentures under axial loading

Objective:This study investigated the effect of proximal contact strength on the three-dimensional displacements of cantilever fixed partial denture(CFPD) under vertically concentrated loading with digital laser speckle(DLS) technique.Methods:Fresh mandible of beagle dog was used to establish the implant-supported CFPD for specimen.DLS technique was employed for measuring the three-dimensional displacement of the prosthesis under vertically concentrated loading ranging from 200 to 3 000 g.The effect of the contact tightness on the displacement of CFPD was investigated by means of changing the contact tightness.Results:When an axial concentrated loading was exerted on the pontic of the implant-supported CFPD,the displacement of the CFPD was the greatest.The displacement of the prosthesis decreased with the increase of contact strength.When the contact strength was 0,0.95,and 3.25 N,the displacement of the buccolingual direction was smaller than that of the mesiodistal direction but greater than that of the occlusogingival direction.When the force on the contact area was 6.50 N,the mesiodistal displacement of the prosthesis was the biggest while the buccolingual displacement was the smallest.Conclusions:The implant supported CFPD is an effective therapy for fully or partially edentulous patients.The restoration of the contact area and the selection of the appropriate contact strength can reduce the displacement of the CFPD,and get a better stress distribution.The most appropriate force value is 3.25 N in this study.

Distributed sparse bundle adjustment algorithm based on three-dimensional point partition and asynchronous communication

Sparse bundle adjustment(SBA) is a key but time-and memory-consuming step in three-dimensional(3 D) reconstruction. In this paper, we propose a 3 D point-based distributed SBA algorithm(DSBA) to improve the speed and scalability of SBA. The algorithm uses an asynchronously distributed sparse bundle adjustment(A-DSBA)to overlap data communication with equation computation. Compared with the synchronous DSBA mechanism(SDSBA), A-DSBA reduces the running time by 46%. The experimental results on several 3 D reconstruction datasets reveal that our distributed algorithm running on eight nodes is up to five times faster than that of the stand-alone parallel SBA. Furthermore, the speedup of the proposed algorithm(running on eight nodes with 48 cores) is up to41 times that of the serial SBA(running on a single node).

A modified moire interferometer for three-dimensional displacement measurement

This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system are described. The experimental results of thermal displacement of an electronic device are shown.

Characteristic finite element scheme and analysis the three-dimensional two-phase displacement semi-definite problem

NUMERICAL simulation of the two-phase (oil and water) displacement problem is the mathematical basis of energy sources. For two-dimensional positive problem, Douglas et al. put forward the well-known characteristic finite difference method and characteristic finite element method. However, for numerical analysis there exist some difficulties. They assumed that the problem is periodic and the diffusion matrix of the concentration equation is positive difinite

Research on error accumulation control of three-dimensional adjustment with offset constraint

Background Currently,laser tracker is the primary instrument used to carry out three-dimensional position measurement in accelerator alignment.Theoretically,three-dimensional measuring data processed by three-dimensional adjustment are more rigorous,however,error accumulation is found in practice.Purpose In order to control error accumulation and further improve the measurement accuracy of accelerator alignment,this research introduces the laser alignment system into the activity of measurement and data processing.Methods A measurement scheme combining laser tracker and laser alignment system is proposed.To construct the constraint condition,the offset values from the measuring points to the laser straight-line datum were used.To carry out the three-dimensional adjustment with offset constraint,the laser tracker observations were used.Results A three-dimensional adjustment function model of laser tracker observations is given.The construction method of the constraint equation is researched,and the calculation formulas of the three-dimensional adjustment with offset constraint are derived.A 200 m linac tunnel control network is designed,using simulation measurement method,the measuring data of laser tracker and the offset values from the measuring points to the laser straight-line datum were generated.The simulated data are calculated by the method given in this paper and the result is analyzed.Conclusion Simulation result shows introducing the laser alignment system into laser tracker measurement and applying the three-dimensional adjustment with offset constraint can effectively suppress the error accumulation caused by long distance move station measurement.