Filling mode and regularity of vertical centrifugal casting process of titanium alloy in thin-walled cylinder cavity

The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.

Assessing the range of blasting-induced cracks in the surrounding rock of deeply buried tunnels based on the unified strength theory

Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.

Collapse mode of rock mass induced by a concealed karst cave above a deep cavity

Reliable prediction of the potential collapse region of rock mass is a key challenge for deep underground cavity excavation, especially if a concealed karst cave is located above the excavated cavity. Because of the effect of the blast vibration, a possible collapse would occur at a certain region between the concealed karst cave and the excavated cavity. This paper aims to study the roof collapse of a deep buried cavity induced by a concealed karst cave base on a two-dimensional failure mechanism by using upper bound theorem. The failure mechanism is constituted by arbitrary curves which is similar to the collapse observed in an actual cavity excavation. The shape and range of the collapse block is determined by virtual work equation in conjunction with variational approach. The results obtained by the presented approach are approximate with the numerical results provided by finite difference code, which indicates that the proposed method in this work is valid.

A new failure mechanism for deep cavity and upper bound solution of supporting pressure

The investigation of supporting pressure is of great significance to the design of underground structures.Based on the kinematical approach of limit analysis,an improved failure mechanism is proposed,and the supporting pressure is investigated for deep buried cavity.Three failure mechanisms are first introduced according to the existing failure mechanisms of geotechnical structures of limit analysis.A comparison with respect to the optimal failure mechanisms and the upper bound solutions provided among these three mechanisms are then conducted in an attempt to obtain the improved failure mechanism.The results provided by the improved failure mechanism are in good agreement with those by the existing method,the numerical solution and field monitoring,which demonstrates that the proposed failure mechanism is effective for the upper bound analysis of supporting pressure.

Effect of die cavity dimension on micro U deep drawing behaviour with T2 foil

The strips U deep drawing experiments were carried out to study the effect of die cavity dimension with an extension machine manufactured by SANS company. The effects of parameters were analyzed in deep drawing process under different experimental conditions, such as punch load, reduction of thickness, angle of U part and surface quality. The experiment results show that the punch load increases with the decrease of female radius, and larger blank holder force enlarges the range of increasing. With the increasing of blank holder force, the angle of U part increases, and the reduction of foil thickness at the corner becomes larger. Obvious scratch and accumulation at the die cavity corner were observed by SEM. The investigation results indicate that micro U deep drawing of foil is affected by micro die cavity dimension.

Numerical Investigation of Lid-Driven Deep Cavity with Local Grid Refinement of MRT-LBM

In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.

超深层断控碳酸盐岩油藏地质力学建模及其在开发中的应用

为提高超深断控碳酸盐岩油藏的开发效益,通过开展大尺寸岩样力学实验,揭示高角度—近直立断裂面变形与连通机理;基于高压注水提采的力学与流动耦合原理,通过地质力学建模,明确了断控碳酸盐岩油藏现今地应力场和断裂活动性分布规律;发现不同方位的断裂活动性以及不同部位的缝洞体连通性有明显差异,进而分析了不同井眼轨迹的开发效果,提出了地质工程一体化工作方法,科学指导井眼轨迹设计和注水方案优化。结果表明:①走滑断裂变形中的大尺度破碎体和高角度裂缝系统是影响储层品质的关键因素,高压注水一方面能够激活先存裂缝,一方面还能在先存裂缝基础上发生延伸扩展,甚至可以产生新的裂缝,促进了断控缝洞体在纵横向上的互相连通;②高压注水过程中断裂体内部发生力学与流动之间的耦合变化,渗流环境得到改善,通过循环举升,从而提高油气采收率;③根据断裂体形态、产状以及断裂面动态剪切变形连通性,可优选定向井最佳井点和井眼轨迹,并优化注水方案;④塔里木盆地断控油藏试验区通过高压注水,采收率提高5个百分点,该方法为超深断控型油藏高效开发提供了较好的理论依据和技术支撑。

基于探地雷达的隧道衬砌空洞检测方法

隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only Look Once version 5)目标检测模型,结合数据集目标特征,提出一种检测衬砌空洞的算法,引入特征融合模块提高网络感受野,并采用K-means聚类算法提高检测准确率。通过现场检测,本文的检测方法准确率达到了97.7%,准确可靠,可在工程中进行应用。

基于多尺度空洞卷积结构的路面裂缝分割方法

为了实现道路裂缝的自动化检测,改善现有裂缝分割模型存在分割不连续与嘈杂背景误分割等问题,提出了一种基于多尺度空洞卷积结构的裂缝分割模型MAC-UNet。以UNet作为基础网络,首先提出了多尺度空洞卷积结构,替换编码器与解码器中的双卷积结构,提升了网络对复杂拓扑结构的分割性能。然后,构建了交叉注意力机制,使用金字塔注意力模块代替编、解码器之间的跳跃连接,保留因池化丢失的空间特征。增加通道注意力引导多尺度信息,有效地融合到解码器特征中,使得恢复裂缝时,细节更加丰富,定位更准确。最后,在道路裂缝数据集CFD和GAPS384上与FCN、PSPNet等5种方法进行试验对比,相较于UNet,在CFD数据集上,MIOU和Kappa系数分别提升了8.4%和8.52%。在GAPS384数据集上,分别提升了6.84%和8.23%,对于道路裂缝的分割更加清晰与完整。结果表明:与主流的分割算法相比,所提出算法的识别精度方面具有较明显的优势,在光照不均匀、各种噪音干扰、背景灰度水平不同的情况下,所提模型仍然能够获取稳定的检测结果,能够应对复杂裂缝分割问题,并且可视化裂缝检测误差较小,符合实际工程需求,且模型体积较小,具有一定的工程应用价值。

孔喉结构对超深层碳酸盐岩气藏多类型储层渗流能力的影响

超深层碳酸盐岩气藏孔喉结构非均质性强,渗流机制复杂。选取川西北地区双鱼石区块栖霞组储层岩心,通过多尺度CT试验、核磁共振试验和储层条件下的单相渗流、气水两相渗流及应力敏感试验等,系统定量地研究超深层多类型储层孔喉结构特征参数与渗流特征参数的相关性,深入剖析裂缝、大孔和基质孔隙对超深层多类型气藏气体单相和气水两相渗流的影响。结果表明:不同于中深层储层,增加喉道数量对于提高目的超深层储层的渗流能力非常关键;裂缝发育增加了岩样喉道数量、提高了岩样的连通性从而来大幅度提高岩样的气体渗流能力,并降低了含水气藏的启动压力梯度,缩小了岩样的气水两相共渗区间,但裂缝受压易形变的特质导致岩样的应力敏感性增强,在高压差时岩样的渗流能力和弹性能也急速下降;大孔喉发育提高了储层的储容能力,其抵抗变形能力强的特质有利于降低岩样的应力敏感性,在高压差时维持岩样较高的渗流能力和弹性能。在实际生产过程中,应考虑对裂缝-孔隙型和裂缝-孔洞型储层在生产初期控制产气速度以维持长期稳产,对孔洞型和孔隙型储层增大生产压差或进行压裂和酸化等工艺措施以释放储层产能。

深地、深海油气藏储量评估中针对不确定性的可靠技术选择与应用

对于新领域和复杂类型油气藏,储量评估关键参数的确定意义重大,也是勘探开发的难点和重点,建立可靠技术开展储量评估是目前国际主流做法,但国内强调勘探开发主体技术却少有关于储量评估可靠技术的研究。近年来国内石油公司不断在近万米深层和水深超过500m海域取得重大油气突破,在勘探评价阶段发现的超深层大型碳酸盐岩缝洞型油气藏和深海油气藏储量评估面临资料有限、投资约束和井控程度低等问题,如何选择或建立可靠技术开展储量评估已成为该领域的研究重点。从可靠技术的定义和适用性出发,重点针对深海和深地油气藏勘探投资大、不能大面积部署探井,以及深地和深海油气藏储量评估过程中的复杂性、特殊性及不确定性,开展可靠技术在储量评估关键参数选取中的适用条件和应用范围研究,通过典型案例解剖认为,深海油气藏地震振幅随偏移距变化(AVO)、直接烃指标(DHI)和压力系统法等可靠技术可识别油气藏的油水界面,4个区块验证成功率高达92%,应用该技术降低了勘探评价阶段的投资及开发风险。深地缝洞型碳酸盐岩油气藏利用地震敏感属性分析技术确定含油气边界和含油气面积,该技术通过钻井放空漏失、测井解释结果和生产动态等证实储层预测的可靠性较高,地震储层预测与实钻吻合率达84%,从而使储量评估结果更加接近油藏实际,确保了少井情况下储量评估结果的合理性,同时也推动了可靠技术在储量评估领域的应用。

深层—超深层海相碳酸盐岩成储成藏机理与油气藏开发方法研究进展

基于钻井、地震、测井、测试以及实验分析等新资料,针对中西部叠合盆地深层—超深层海相碳酸盐岩层系成储、成藏和油气藏高效开发面临的关键科学问题开展持续攻关。研究表明:(1)断裂主导形成的储集体和古老层系白云岩储层是深层—超深层海相碳酸盐岩两类重要的储层;以断裂为主导形成的规模储集体,根据成因可进一步分为3种类型:断裂活动过程中构造破裂形成的缝洞储集体、致密碳酸盐岩受断裂和流体双重改造形成的储集体与早期丘滩等高能相带受断裂和流体改造形成的储层;优势丘滩相、早期白云石化和溶蚀、酸性流体环境、膏盐岩封盖和超压是优质白云岩储层形成和保持的关键。(2)中国中西部叠合盆地海相碳酸盐岩层系富有机质页岩主要发育于被动陆缘深水陆棚、碳酸盐缓坡等环境中,构造-热体制是控制深层—超深层油气藏赋存相态的重要因素,改造型动力场控制中西部叠合盆地深层—超深层海相碳酸盐岩油气成藏与分布。(3)普光等高含硫酸性气田开发过程中硫析出堵塞井筒,采用井筒溶硫剂配合连续油管解硫堵效果明显;基于沉积模拟的双重介质建模数模一体化技术可以精细刻画水侵前缘空间展布及变化,并据此提出气井全生命周期调、排、堵控水对策。(4)超深断控缝洞油气藏开发过程中,储层应力敏感,渗透率随压力下降而显著降低,产量递减较快;凝析气藏相态变化快,压降显著影响凝析油采出程度;据此提出“注水+注天然气”重力驱油藏开发方法和“高注低采”天然气驱凝析气藏开发方法;采用分层次约束、逐级地质建模和流-固-热耦合的复合介质数值模拟有效提高了油气藏开发生产动态模拟的预测精度。

Ti-6Al-4V六槽深浅腔动静压轴承刚度数值分析

针对传统材料制造的动静压轴承刚度较差的问题,提出一种基于Ti-6Al-4V材料制造六槽深浅腔交错分布的动静压轴承。利用ANSYS有限元软件建立六槽深浅腔动静压轴承流固耦合模型,研究轴径间隙、转速以及偏心率对QSn4-3轴承和Ti-6Al-4V轴承刚度的影响规律。结果表明:钛合金材料制成的轴承刚度优于传统锡基合金材料制造的轴承,各工况参数中,轴径间隙对轴承刚度的影响最为显著,其次是偏心率。该研究可为钛合金滑动轴承的数值模拟和设计提供参考。

塔里木盆地塔北地区多期断裂差异匹配控制下超深岩溶缝洞储层成藏特征

超深断控岩溶缝洞型油藏是塔北地区重要油藏类型,探讨多期构造活动与深层油气成藏匹配关系对区域油气勘探具有重要意义。基于哈拉哈塘油田、金跃油田和富满油田连片地震资料,以野外地质露头断裂特征为指导,采用多种地震精细解释手段,分期、分级、分段刻画研究区断裂。基于研究区中寒武统玉尔吐斯烃源岩认识,结合加里东期、海西期和喜马拉雅期3期成藏的特点,将研究区走滑为主的控藏断裂划分为加里东早期、加里东中晚期、海西晚期和喜马拉雅期。进一步分析多期断裂继承性关系、通源特点和调整作用等,结合多种类型岩溶缝洞型储层的开发现状,探讨了研究区走滑断裂控制下的岩溶缝洞型储层成藏差异性。结果表明:(1)研究区油气藏关键因素是油源断裂通源性与后期断裂的调整作用,将加里东早期正断裂系统定义为源内断裂,加里东晚期形成的走滑断裂系统定义为源外断裂,源内断裂利于寒武系烃源岩排烃,源外断裂进一步沟通烃源岩实现油气运移成藏,基于这种认识建立4种通源模式;(2)结合研究区存在加里东晚期、海西期和喜马拉雅期3个主力生烃期的认识,海西晚期部分北西向走滑断裂继承性发育至二叠系,对加里东期油藏有一定的破坏和调整作用,喜马拉雅期部分北东向走滑断裂系统继承性发育至新近系,对早期油气藏起破坏和调整作用,建立了3种调整样式;(3)根据断裂匹配关系,建立6种走滑断裂控藏等级,并将研究区加里东中晚期走滑断裂带逐一划分,叠合开采现状图显示差异控藏断裂与油气生产情况匹配度较高;(4)选择发育断裂与岩溶共同控储的研究区,建立多期断裂系统与多种类型岩溶缝洞油气藏的匹配关系,并将认识成功应用于研究区井位勘探中,取得较好效果,为受控于走滑断层的岩溶缝洞油气藏勘探开发提供一定指导意义。

瓶腔深孔构件精密镗削切屑卷曲半径预测及控制

以航天发动机涡轮轴为代表的瓶腔深孔结构零件,在精密镗削过程中容易出现排屑困难、加工效率低等问题,现对镗孔时切屑的形成进行研究,掌握不同工艺参数对切屑形态以及排屑效果的影响规律。基于Box-Behnken法设计试验,利用有限元分析法模拟瓶腔深孔加工过程,以工艺参数为自变量,建立切屑卷曲半径预测模型,选择合理的工艺参数,优化排屑。进行实际加工试验,验证切屑卷曲半径预测模型的准确性;试验结果表明试验值与预测值相似度达90%以上,证明了切屑卷曲半径预测模型的有效性、准确性。

典型薄壁窄槽深盲腔钛合金铸件工艺数值模拟及优化

聚焦于钛合金铸件,尤其是薄壁窄槽深盲腔结构件的熔模真空离心铸造技术,鉴于钛合金具有较高的化学活性,易与多种大气成分发生反应,因此对型壳材料的选择及其干燥过程提出了严格要求。然而,由于窄槽深盲腔型壳受限于干燥条件,浇注过程中易产生冷隔、欠铸、气缩孔等缺陷,导致其铸件质量的稳定性未能满足服役标准。针对这一问题,采用铸造模拟仿真技术,对金属液充型行为进行精确分析,以确保薄壁区域按序填充,并优化离心铸造中的补缩路径和气体逸散通道,有效解决了密集气孔的问题,实现复杂钛合金铸件的稳定批量生产。

金丝球焊近壁键合技术

在引线键合工艺应用中,由于球焊键合工艺具有键合方向灵活、键合速度快等优势,在半导体芯片的封装互联领域被广泛应用。针对金丝球焊键合工艺中的近壁键合问题进行了研究,从键合方式、劈刀设计两个方面进行优化、改进,制定了两种不同的解决方案,并分析了两种方案的应用局限性。

具有深腔结构的刚挠结合板制作方法探讨

印制电路板(PCB)需要在有限的空间内集成更多的功能模块,因此有一种相应的深腔设计。但深腔制作存在深度控制精度差、工艺流程复杂及制作难度高等问题。以一种具有深腔结构的有机发光二极管(OLED)模组刚挠结合板为研究对象,通过解析关键制程工艺、关键控制点,以及对比不同工艺优缺点的方式,对深腔结构的制作难点进行分析,重点介绍了深腔加工的关键制作技术。

薄壁深腔小脱模斜度箱体塑件注塑模具设计

针对某办公设备上的薄壁深腔小脱模斜度箱体塑件为研究对象,根据塑件深腔、薄壁、脱模斜度小的结构特点和适用于大批量生产的技术要求,设计了一副包含:定模芯入子优先抽芯结构、动模芯入子优先抽芯结构和四边滑块侧向抽芯结构的复杂注塑模具。模具设计采用四边滑块侧向抽芯机构,解决塑件两侧脱模方向倒扣及塑件表面脱模斜度小、高度方向太深易黏定模的问题,同时可以优化分型面结构,提高加工效率;模具设计的定模芯入子优先抽芯结构,通过在两处环形筋位处设置的前模芯镶件入子,利用镶件的排气特性,解决定模侧两处环形深的筋位在注塑成型时易出现困气、烧焦及填充困难的问题,通过优先抽芯前模芯的镶件入子,解决此两处深的筋位黏模的问题;模具设计的动模芯入子优先抽芯结构解决了塑件深腔、薄壁结构包紧力过大顶出困难的问题,利用动模芯入子的优先抽芯结构,先脱出动模型芯,即可轻松顶出塑件同时不会造成顶出变形。针对塑件成型时易出现的问题,经过模具结构优化设计,模具在后续实际生产中表现优异、符合预期。

CPTU数据校准上海深层软土参数的随机力学-贝叶斯方法

城市深层地下空间的开发需要开展科学计算。合理的本构模型和准确的岩土参数是岩土力学分析的两大支撑。修正剑桥模型(modified cam-clay,MCC)的岩土参数简单直观,被广泛应用于岩土工程实践。室内土工试验由于取样扰动、试验误差等不可避免的缺陷,难以精确获得深层岩土参数。结合先验知识、室内试验数据和孔压静力触探(piezocone penetration test,CPTU)测试数据,将关键岩土参数视为随机变量,采用随机力学-贝叶斯方法,校准深层软土的关键岩土参数,如临界状态应力比、压缩系数、回弹系数和超固结比。以上海市苏州河深层排水调蓄管道系统工程——云岭竖井基坑工程为背景,以基础底板处的深部第(8)层土为研究对象。首先,利用MCC模型的柱孔扩张理论,揭示了CPTU数据(锥尖阻力、侧摩阻力和孔隙水压力)与极限扩孔应力之间的力学转换机理,利用苏格兰Bothkennar岩土试验场地的试验数据,验证CPTU测试数据力学模型的适用性;其次,建立关键岩土参数与CPTU数据之间的二次非交叉响应面,利用MCMC(Markov-chain Monte Carlo)抽样算法,获得关键岩土参数的后验统计特征;最后,结合岩土参数的后验均值,开展超深基坑工程的数值计算。结果表明,经过柱孔扩张随机力学-贝叶斯方法校准后,关键岩土参数的不确定性大幅度降低,后验均值的预测结果与监测值较为接近,证明了该方法的高效、合理性。