Journal of Zhejiang University-SCIENCE A最新文献

{"title":"Effect of low operating temperature on the aerodynamic characteristics of a high-speed train","authors":"Xiu-juan Miao, G. Gao, Jiabin Wang, Yan Zhang, Wenfei Shang","doi":"10.1631/jzus.A2200166","DOIUrl":"https://doi.org/10.1631/jzus.A2200166","url":null,"abstract":"In this study, an improved delayed detached eddy simulation (IDDES) method based on the shear-stress transport (SST) k-ω turbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re =1.85×10^6. The accuracy of the numerical method has been validated by wind tunnel tests. The aerodynamic drag of the train, pressure distribution on the surface of the train, the flow around the vehicle, and the wake flow are compared for four temperature values: +15 °C, 0 °C, −15 °C, and −30 °C. It was found that lower operating temperatures significantly increased the aerodynamic drag force of the train. The drag overall at low temperatures increased by 5.3% (0 °C), 11.0% (−15 °C), and 17.4% (−30 °C), respectively, relative to the drag at +15 −C. In addition, the low temperature enhances the positive and negative pressures around and on the surface of the car body, raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity. The range of train-induced winds around the car body is significantly reduced, the distribution area of vorticity moves backwards, and the airflow velocity in the bogie cavity is significantly increased. At the same time, the temperature causes a significant velocity reduction in the wake flow. It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption, and significantly interfering with the airflow characteristics around the car body. 目的 受空气物理参数变化影响,低温下列车周围的流场特性与常温时存在差异。本文旨在对高速列车在低运行温度下的空气动力学性能及流场特性变化研究予以补充,探究低温对列车周围流场、列车风及列车尾流等方面的影响,以提高高速列车的抗高寒性能。 创新点 1. 将气体参数设置为低温环境,探究列车相比常温下的气动性能及周围流场的变化。2. 对比不同低温环境,探究不同程度低温对列车气动特性的影响。 方法 1. 通过基于SST k-ω湍流模型的IDDES数值计算方法对高速列车在雷诺数约为1.85×106的条件下低温运行的流动特性进行仿真。2. 依托后处理软件对不同温度下列车气动阻力、表面压力分布、车身周围流动及尾流等进行分析。3. 将结果进行比对,得出不同程度低温对列车气动特性的影响。 结论 1. 低温显著增加列车气动阻力;相比常温环境,0 °C、−15 °C及∑30 °C时的气动阻力分别增加了5.3%、11.0%和17.4%。2. 低温会增强车体周围的正负压力场,进而提高冲击流及流速快速变化区域的正负压力峰值。3. 低温时,列车风的作用范围缩小,涡量分布区域后移,而转向架舱内的气流流速增加。4. 低温时,列车的尾流速度降低。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"31 1","pages":"284-298"},"PeriodicalIF":3.2,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85751155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adaptive fault-tolerant control of high-speed maglev train suspension system with partial actuator failure: design and experiments","authors":"Yougang Sun, Fengxing Li, G. Lin, Junqi Xu, Zhenyu He","doi":"10.1631/jzus.A2200189","DOIUrl":"https://doi.org/10.1631/jzus.A2200189","url":null,"abstract":"目的 在强磁场持续运行下,高速磁悬浮列车悬浮系统的执行器容易发生部分故障,使得悬浮控制问题具有挑战性。为了降低容错的成本和能耗,提升高速磁悬浮列车悬浮系统对执行器故障的容忍度,本文从实用的角度出发,提出一种新型的高速磁浮列车悬浮系统自适应补偿非线性容错控制策略。 创新点 1. 无需知道执行器的故障信息,自适应补偿控制律随系统故障的发生而变化,并自适应地进行重构,降低系统的保守性;2. 在没有任何线性化近似的情况下,证明控制器的设计和稳定性。 方法 1. 通过数学推导,建立基于连接结构的悬浮系统的动力学模型（图2和公式(12)）;2. 通过理论分析,描述执行器故障的类型（公式(14)）;3. 通过数学分析,设计一种具有自适应更新律的非线性容错悬浮控制律,以实现针对部分执行器故障的稳定悬浮（公式(19)和(20)）。利用Lyapunov理论和扩展的Barbalat引理来严格证明闭环渐近稳定性（公式(23)）;4. 通过在高速磁悬浮车辆-轨道磁耦合实验平台进行硬件实验,验证所提方法的可行性和有效性（图4~17）。 结论 1. 提出的具有自适应补偿的非线性容错控制策略在无故障诊断和隔离的情况下,实现了部分执行器故障时优越的悬浮控制性能;推导出的容错控制律结构简单,可以随着故障的发生而自适应变化,从而提高了系统的可靠性和暂态性能;通过严格的数学分析,证明了整个闭环系统是全局渐近稳定的。2. 通过硬件实验,实现了常规悬浮控制或跟踪悬浮控制,同时也补偿了实际中的部分执行器故障,证明所提方法具有良好的鲁棒性。 High-speed maglev trains will play an important role in the high-speed transportation system in the near future. However, under the conditions of strong magnetic fields and continuous operation, the actuators of the high-speed maglev train suspension system are prone to lose partial effectiveness, which makes the suspension control problem challenging. In addition, most existing fault-tolerant control (FTC) methods for suspension systems require linearization around the equilibrium points during the controller design or stability analysis. Therefore, from a practical perspective, this study presents a novel nonlinear FTC strategy with adaptive compensation for high-speed maglev train suspension systems. First, a nonlinear dynamic model of the suspension system based on join-structure is established and the actuator failures are described. Then, a nonlinear fault-tolerant suspension control law with an adaptive update law is designed to achieve stable suspension against partial actuator failure. The Lyapunov theory and extended Barbalat lemma are utilized to rigorously prove the closed-loop asymptotic stability even if there is partial actuator failure, without any approximation to the original nonlinear dynamics. Finally, hardware experimental results are included to demonstrate the effectiveness of the proposed approach.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"67 1","pages":"272-283"},"PeriodicalIF":3.2,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78249910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deformation pre-compensated optimization design of cam ring for low pulsation hydraulic motors","authors":"Chao Zhang, Hao Tan, Y. Fang, Xiao-long Zhang, Y. Yang, Yiman Duan, Min Han, Shaojian Cui, Bing Xu, Jun-hui Zhang","doi":"10.1631/jzus.A2200552","DOIUrl":"https://doi.org/10.1631/jzus.A2200552","url":null,"abstract":"Cam-lobe radial-piston hydraulic motors are widely used in large machinery due to their excellent capability to withstand high loading at low speed. However, the line contact between the roller and cam ring generates elastic deformation of the cam ring under high loading, leading to obvious speed and torque pulsations and even the detrimental crawl problem of hydraulic motors. To address this issue, we propose a deformation pre-compensated optimization design approach to compensate for the cam ring deformation in advance, thereby eliminating the influence of cam ring deformation on the hydraulic motor’s pulsation. In this approach, the design process is divided into two steps: first, the overall profile of the cam ring is optimized based on the calculated elastic deformation; second, the local profile of cam ring is further optimized until the hydraulic motor’s pulsations no longer reduce. Finally, a case study is carried out to verify the effectiveness of this approach. The result indicates the pulsation rate of a deformation pre-compensated cam ring is 40% lower than that of an uncompensated one. This study offers an easy and feasible way to design an optimized cam ring profile for low pulsation hydraulic motors. 目的 内曲线液压马达在重载工况下凸轮环与滚子接触产生的弹性变形, 改变了预设的运行轨迹, 使得马达产生较大 的转速转矩脉动。本文提出一种凸轮环变形预补偿的优化设计方法, 在设计阶段耦合弹性变形的影响, 以降低 马达在实际工作时的脉动, 从而提高马达的稳定性。 创新点 1. 通过赫兹接触理论和马达结构的受力分析, 建立凸轮环弹性变形非均匀分布的计算方法; 2. 建立凸轮环弹性 变形预补偿的设计方法, 并通过实验进行验证。 方法 1. 通过理论推导建立凸轮环非均匀弹性变形与工作压力之间的直接关系, 基于此提出凸轮环弹性变形预补偿的 设计方法, 并给出完整的流程与计算方法。2. 通过仿真模拟, 对凸轮环变形计算进行验证, 初步证明所提方法 的正确性。3. 通过实验验证, 对在不同工况下, 马达的脉动率进行分析, 验证所提方法的有效性。 结论 1. 提出凸轮环变形预补偿优化设计方法, 包括初始的整体补偿和二次局部补偿。2. 在对马达进行详细运动学和 受力分析的基础上, 推导出凸轮环变形的计算过程, 并用有限元仿真方法进行实例验证。3. 脉动降低率随着工 作压力的增加而增加, 并且在45 MPa 工作压力下可以实现40%的高脉动降低率。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"104 1","pages":"130-145"},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77809501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preparation and 3D printing of high-thermal-conductivity continuous mesophase-pitch-based carbon fiber/epoxy composites","authors":"Haiguang Zhang, Kunlong Zhao, Qingxi Hu, Jinhe Wang","doi":"10.1631/jzus.A2200413","DOIUrl":"https://doi.org/10.1631/jzus.A2200413","url":null,"abstract":"To meet the requirements of spacecraft for the thermal conductivity of resins and solve the problem of low thermal conduction efficiency when 3D printing complex parts, we propose a new type of continuous mesophase-pitch-based carbon fiber/thermoplastic polyurethane/epoxy (CMPCF/TPU/epoxy) composite filament and its preparation process in this study. The composite filament is based on the high thermal conductivity of CMPCF, the high elasticity of TPU, and the high-temperature resistance of epoxy. The tensile strength and thermal conductivity of the CMPCF/TPU/epoxy composite filament were tested. The CMPCF/TPU/epoxy composites are formed by 3D printing technology, and the composite filament is laid according to the direction of heat conduction so that the printed part can meet the needs of directional heat conduction. The experimental results show that the thermal conductivity of the printed sample is 40.549 W/(m·K), which is 160 times that of pure epoxy resin (0.254 W/(m·K)). It is also approximately 13 times better than that of polyacrylonitrile carbon fiber/epoxy (PAN-CF/epoxy) composites. This study breaks through the technical bottleneck of poor printability of CMPCF. It provides a new method for achieving directional thermal conductivity printing, which is important for the development of complex high-performance thermal conductivity products. 目的 为满足航天器对树脂导热性能的要求, 解决3D 打印复杂零件时导热效率低的问题, 本研究提出一种新型连续 中间相沥青基碳纤维/热塑性聚氨酯/环氧树脂(CMPCF/TPU/epoxy)复合长丝并介绍其制备工艺。 创新点 1. 该复合长丝的制备基于连续中间相沥青基碳纤维(CMPCF)的高导热性能、热塑性聚氨酯(TPU)的高弹 性和环氧树脂(epoxy)的耐高温性能。2. 沿导热方向打印长丝, 并提出热固性复合丝材打印件的新固化方式。 方法 1. 采用上浆剂法进行表面上浆, 选取水溶性聚氨酯作为表面上浆剂, 提升连续中间相沥青基碳纤维聚束性。2. 通过增韧预处理, 选取TPU 作为增韧基体材料, 在上浆后的碳纤维束外包裹一层具有高韧性高强度的树脂层。 3. 采用浸涂处理工艺, 选取固态环氧树脂, 成功制备出高导热CMPCF/TPU/epoxy 复合丝材。4. 沿导热方向规 划打印路径并进行打印测试, 验证复合长丝的可打印性和打印件的导热系数。 结论 1. 通过对CMPCF 进行表面上浆、增韧预处理和预浸处理, 成功制备出高导热性能的CMPCF/TPU/epoxy 复合 长丝; 在CMPCF 外包裹TPU, 解决了CMPCF 因脆性而难以打印的问题。2. 3D 打印使纤维沿导热方向铺设, 为制备具有高导热系数的复杂打印件提供了一种新方法。3. 导热系数测试表明, 当CMPCF 体积含量仅为6.6% 时, 复合材料的导热系数为40.549 W/(m·K), 是纯环氧树脂的160 倍, 是聚丙烯腈基碳纤维(PAN-CF)体积 为14.6%时复合材料的13 倍, 因此CMPCF 的加入明显提高了打印件的导热性能。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"7 1","pages":"162-172"},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87980213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reliability measure approach considering mixture uncertainties under insufficient input data","authors":"Zhenyu Liu, Yufeng Lyu, Guodong Sa, Jianrong Tan","doi":"10.1631/jzus.A2200300","DOIUrl":"https://doi.org/10.1631/jzus.A2200300","url":null,"abstract":"目的 可靠性优化需要精确度量含不确定性变量的系统可靠性。然而, 工程实践中往往不能获取充足的样本数据计算 可靠性指标, 因此本文针对不完备数据下的系统可靠性度量开展研究。 创新点 1. 提出了随机变量、稀疏变量以及区间变量混合不确定性下的可靠性度量方法; 2. 本方法可以推广到p-box 和 证据理论变量等不确定性变量。 方法 1. 建立不完备数据下的失效概率函数; 2. 基于中间辅助变量实现失效概率的一致性计算; 3. 针对数据不完备前 提下失效概率自身也是不确定性变量的问题, 对失效概率指标进行敏感度分析; 4. 将提出的失效概率计算方法 推广到p-box 变量、多模态分布变量以及证据理论变量; 5. 采用经典函数案例验证方法的有效性, 并将方法应 用于锻压机的可靠性分析。 结论 1. 不完备数据下的系统可靠性存在较大的不确定性; 2. 通过中间辅助变量可以精确分析混合不确定性下系统的 失效概率, 确定失效概率的随机分布特性; 3. 提出的方法可以用较少的计算时间获得准确的可靠性结果; 4.本 文方法可以扩展到更多不确定性类型的可靠性分析, 辅助混合不确定性优化设计。 Reliability analysis and reliability-based optimization design require accurate measurement of failure probability under input uncertainties. A unified probabilistic reliability measure approach is proposed to calculate the probability of failure and sensitivity indices considering a mixture of uncertainties under insufficient input data. The input uncertainty variables are classified into statistical variables, sparse variables, and interval variables. The conservativeness level of the failure probability is calculated through uncertainty propagation analysis of distribution parameters of sparse variables and auxiliary parameters of interval variables. The design sensitivity of the conservativeness level of the failure probability at design points is derived using a semi-analysis and sampling-based method. The proposed unified reliability measure method is extended to consider p -box variables, multi-domain variables, and evidence theory variables. Numerical and engineering examples demonstrate the effectiveness of the proposed method, which can obtain an accurate confidence level of reliability index and sensitivity indices with lower function evaluation number.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"85 1","pages":"146-161"},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80329215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced ocean wave energy harvesting: current progress and future trends","authors":"Fang He, Yibei Liu, Jiapeng Pan, Xinghong Ye, Pengcheng Jiao","doi":"10.1631/jzus.A2200598","DOIUrl":"https://doi.org/10.1631/jzus.A2200598","url":null,"abstract":"With a transition towards clean and low-carbon renewable energy, against the backdrop of the fossil-energy crisis and rising pollution, ocean energy has been proposed as a significant possibility for mitigating climate change and energy shortages for its characteristics of clean, renewable, and abundant. The rapid development of energy harvesting technology has led to extensive applications of ocean wave energy, which, however, has faced certain challenges due to the low-frequency and unstable nature of ocean waves. This paper overviews the debut and development of ocean wave energy harvesting technology, and discusses the potential and application paradigm for energy harvesting in the “intelligent ocean.” We first describe for readers the mechanisms and applications of traditional wave energy converters, and then discuss current challenges in energy harvesting performance connected to the characteristics of ocean waves. Next, we summarize the progress in wave energy harvesting with a focus on advanced technologies (e.g., data-driven design and optimization) and multifunctional energy materials (e.g., triboelectric metamaterials), and finally propose recommendations for future development. 在化石能源危机和环境污染加剧的背景下, 能源产业正在向着清洁低碳方向转变。海洋能有望成为缓解气候变 化和能源短缺的重要能量来源。波浪能是海洋能的重要组成部分。然而由于波浪的低频和不稳定性, 其采集存 在一定技术挑战。本文通过梳理波浪能转换装置的基本机理与主要应用, 讨论现有波浪能采集技术的瓶颈与挑 战; 通过引入近年来出现的数据驱动结构优化等先进设计技术和摩擦电超材料等新型电学功能材料, 提出波浪 能采集技术的可能解决方案和未来发展方向, 并讨论和展望能量采集在“智慧海洋”中的应用潜力和应用范式。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"44 1","pages":"91-108"},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85336638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Examining the influence of the loading path on the cracking characteristics of a pre-fractured rock specimen with discrete element method simulation","authors":"K. Duan, Rihua Jiang, Xue-jian Li, Luchao Wang, Zemin Yang","doi":"10.1631/jzus.A2200235","DOIUrl":"https://doi.org/10.1631/jzus.A2200235","url":null,"abstract":"目的 结构面是岩体的重要组成部分,其对岩体工程结构的变形和失稳有着重要的影响。本文旨在探究加载路径和围压对预制裂缝试样裂纹扩展和强度的影响,揭示不同加载路径下含预制裂缝岩石试样的微观破坏机理。 创新点 1. 设计可以模拟各种工程场景(如隧道、边坡开挖)下应力状态变化的加载路径,包括轴向加载试验、围压卸载试验和围压卸载伴随的轴向加载试验;2. 研究试样裂纹扩展路径及其与加载路径和围压的关系;3. 通过对局部应力集中和裂纹类型的分析,探讨影响断裂过程的微观机制。 方法 1. 基于试验数据,开展离散元模拟参数校准,实现对岩石试样宏观力学参数的再现(表3和图4);2. 基于校准获得微观参数,并开展三种加载路径下预制裂缝岩石试样数值模拟试验,获得加载路径与围压对试样裂纹扩展的影响(图5~12);3. 通过分析试样加载过程的应力分布以及微裂纹类型的占比,获得预制裂缝试样 裂纹扩展的微观机理(图13~16)。 结论 1. 预制裂缝岩石试样加载过程中,裂纹扩展路径与轨迹受围压与加载路径的共同作用,围压的增大降低了加载路径对裂纹扩展的影响。2. 加载过程中,不同类型裂纹的产生主要与不同局部应力的集中有关;在轴向加载条件下,会出现剪切应力的局部集中,抑制了张拉裂纹沿主应力方向扩展,但也会促进垂直于预制裂缝方向的剪切带的产生;卸围压的加载条件下会出现张拉应力的局部应力集中,进而促进细观张拉裂纹的产生。3. 准静态条件下,预制裂缝岩石试样的失效阶段可以通过Hoek-Brown准则进行预测。 Damage in a rock mass is heavily dependent on the existence and growth of joints, which are also influenced by the complex stress states induced by human activities (e.g., tunneling and excavation). A proper representation of the loading path is essential for understanding the mechanical behaviors of rock masses. Based on the discrete element method (DEM), the influence of the loading path on the cracking process of a rock specimen containing an open flaw is examined. The effectiveness of the model is confirmed by comparing the simulation results under a uniaxial compression test to existing research findings, where wing crack initiates first and secondary cracks contribute to the failure of the specimen. Simulation results confirm that the cracking process is dependent upon both the confining pressure and the loading path. Under the axial loading test, a higher confining pressure suppresses the development of tensile wing cracks and forces the formation of secondary cracks in the form of shear bands perpendicular to the flaw. Increase of confining pressure also decreases the influence of the loading path on the cracking process. Reduction of confining pressure during an unloading test amplifies the concentration of tensile stress and ultimately promotes the appearance of a tensile splitting fracture at meso-scale. Confining pressure at the failure stage is well predicted by the Hoek-Brown failure criterion under quasi-static conditions.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"11 1","pages":"332-349"},"PeriodicalIF":3.2,"publicationDate":"2023-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74557590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and numerical study of seepage-induced suffusion under K_0 stress state","authors":"Tuo Wang, Feng-shou Zhang, Pei Wang","doi":"10.1631/jzus.A2200198","DOIUrl":"https://doi.org/10.1631/jzus.A2200198","url":null,"abstract":"Suffusion in gap-graded soil involves selective erosion of fine particles through the pores formed by coarse particles under seepage forces. As the fines content (FC) decreases, the hydraulic and mechanical behavior of the soil will change, posing a huge threat to engineering safety. In this study, we first conduct a series of experimental tests of suffusion by using gap-graded soils and then analyze the evolution process of suffusion and the effect of the hydraulic gradient. Subsequently, according to the physical model, a discrete element method (DEM) numerical model with dynamic fluid mesh (DFM) is developed to extend the experimental study to the pore scale. Our results reveal the migration process of fines and the formation of erosion zones. A parametric study is then conducted to investigate the effect of the hydraulic gradient, FC, and K _0 pressure (which limits the lateral displacement of the sample and applies vertical pressure) on eroded weight. The results show that the eroded weight increases with the increase of the hydraulic gradient and FC but decreases with the increase of K _0 pressure. 目的 目前,潜蚀过程并不能被直接观察到。本研究期望采用透明仪器直接观察潜蚀的演化过程,探讨 K 0应力状态下间断级配土的潜蚀过程。 创新点 1. 研制出一个透明潜蚀仪器,可直接观测间断级配土的潜蚀过程;2. 建立数值模型,扩展试验参数,在颗粒尺度上解释潜蚀规律。 方法 1. 采用透明的潜蚀仪器,直接观测间断级配土的潜蚀过程,并记录潜蚀质量;2. 通过离散元数值模拟的方法,在颗粒尺度上揭示颗粒的迁移规律。 结论 1. 随着侵蚀的进行,试样内部形成侵蚀带并逐渐扩大;从力链分析可知,细颗粒在水流作用下逐渐堆积在粗颗粒形成的孔隙中,并被粗颗粒堵塞。2. 当侵蚀和阻塞区形成时,流速也逐渐局部化;在侵蚀区,孔隙度增大,流速普遍较快,但在阻塞区,流速较慢。3. 参数分析表明,最终潜蚀重量与水力梯度呈正相关关系,且潜蚀重量随 K 0压力的增大而减小;随着细粉含量的增加,潜蚀重量增加。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"12 1","pages":"319-331"},"PeriodicalIF":3.2,"publicationDate":"2023-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73994481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical investigations of the failure mechanism evolution of rock-like disc specimens containing unfilled or filled flaws","authors":"Tian-zhen Wang, Jian Wang, Shengke Jiang, Jiahe Zhang","doi":"10.1631/jzus.A2200238","DOIUrl":"https://doi.org/10.1631/jzus.A2200238","url":null,"abstract":"目的 岩石的力学响应和最终破坏模式与破坏机制的演化有关。本文旨在通过光滑粒子流体力学(SPH)方法模拟材料混合破坏行为, 探讨含填充及未填充裂缝的类岩圆盘试件加载后的破坏机制演变。 创新点 1. 在SPH框架中引入混合破坏模型模拟类岩圆盘试样的破坏行为; 2. 通过SPH数值模拟方法分析圆盘试样的破坏机制演化过程, 研究裂纹聚结和裂缝填充的破坏行为。 方法 1. 在SPH框架下, 分别采用张拉损伤模型和Drucker-Prager模型计算材料的张拉破坏和剪切破坏; 模拟一系列巴西圆盘试样的破坏行为并与试验结果对比, 验证所提SPH方法是否可用于模拟岩石的破坏机制演化。2. 通过统计分析, 研究不同裂缝倾角和材料属性联合作用对试样宏观破坏形态及力学响应的影响。 结论 1. 对于含未填充裂缝的圆盘试样, 岩桥区裂纹的聚结机制受裂缝倾角和材料性能的组合影响。2. 对于含填充裂缝的圆盘试件, 当圆盘和填充材料的抗拉强度与粘聚力的比值接近时, 试样的张拉损伤的增长速度更快, 使得整个试件表现更多的脆性特征。3. 随着充填物分布不均匀程度的增加, 试样张拉损伤的增长速率降低, 且圆盘试样展现出更多的延性特征; 当预制裂缝倾角接近45°时, 填充物的影响更大。 The mechanical responses and ultimate failure patterns of rocks are associated with the failure mechanism evolution. In this study, smoothed particle hydrodynamics (SPH) method with the mixed-mode failure model is proposed to probe into failure mechanism evolutions for disc specimens upon loading. The tensile damage model and the Drucker-Prager model are used to calculate the tensile failure and shear failure of the material, respectively. It is concluded that for flaw-unfilled disc specimens, the crack coalescence mechanism in the rock bridge area is affected by the flaw inclination angle and the material property. Considering disc specimens with filled flaws, the incremental rate of tensile damage grows more rapidly when the disc and filling material have a closer ratio of tensile strength to cohesion, which makes the entire specimen response greater brittleness. Furthermore, with the increasing non-uniformity of filling distribution, the incremental rate of tensile-activated damage decreases and the disc specimen performs more ductile. Besides, the influence of the fillings is greater when the flaw inclination angle is approaching 45°. It is proved that the proposed SPH method can be used to simulate the failure mechanism evolution of rocks, which lays a foundation for the study of more complex rock failure.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"104 1","pages":"64-79"},"PeriodicalIF":3.2,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90578985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanistic investigation on Hg^0 capture over MnO_x adsorbents: effects of the synthesis methods","authors":"Dong Ye, Yongjin Hu, Zhichang Jiang, Xin Liu, Haining Wang","doi":"10.1631/jzus.A2200388","DOIUrl":"https://doi.org/10.1631/jzus.A2200388","url":null,"abstract":"目的 针对当前单质汞高效脱除难题, 本文旨在探讨不同制备方法对锰氧化物吸附剂单质汞捕集性能的影响, 并通过对吸附剂物理化学性质的研究, 揭示锰氧化物吸附剂的构效关系及脱汞机理。 创新点 1. 揭示锰氧化物吸附剂脱汞性能与物化性质之间的构效关系; 2. 阐明锰氧化物吸附剂表面脱汞机理, 并揭示其中的活性位点。 方法 1. 采用常规的沉淀法、水热法及溶胶凝胶法合成锰氧化物吸附剂; 2. 采用微型固定床反应器研究系列锰吸附剂的脱汞性能; 3. 采用物化表征研究系列锰氧化物汞吸附剂的物化特性, 揭示其中的构效关系; 4. 结合动力学计算, 揭示锰氧化物汞吸附剂表面脱汞机理, 并阐明影响吸附剂脱汞性能的关键因素。 结论 1. 与采用沉淀法及水热法制备的汞吸附剂相比, 采用溶胶凝胶法制备的汞吸附剂在150~250 °C的温度区间内具有更为优异的脱汞性能; 2. 采用溶胶凝胶法制备的锰氧化物吸附剂具有丰富的表面酸性位点, 可促进单质汞的吸附, 并为接下来的单质汞氧化步骤提供充足的反应物, 这也是该吸附剂具有优异脱汞性能的主要原因; 3. 脱汞过程中, 初始吸附阶段是主要的速控阶段, 而Mn4+及化学吸附氧为该反应中的主要活性位点。 This study demonstrated the impacts of the synthesis methods on the textural structures, chemical properties, and Hg^0 capture capability of the MnO_ x system. Compared with the samples synthesized using the precipitation (PR) and hydrothermal (HT) methods, the adsorbent prepared via the sol-gel (SG) technique gave the best performance. At 150 °C, ca. 90% Hg^0 removal efficiency was reached after 7.5 h for MnO_ x prepared by the SG method, ca. 40% higher than that of the other two methods. The specific surface area of the adsorbent synthesized via the SG technique (23 m^2/g) was almost double that of the adsorbent prepared by the HT method (12 m^2/g) and three times that of the one prepared by the PR method (7 m^2/g). The presence of plentiful acid sites from the SG method facilitated the physisorption of Hg^0, making more Hg^0 available to be oxidized to HgO by the redox sites and thus giving the adsorbent prepared by the SG method the highest Hg^0 removal efficiency. The strong oxidative ability accelerated the oxidation of the physically adsorbed Hg^0 to HgO, which explained the higher Hg^0 removal efficiency of the sample prepared using the HT method than that of the one synthesized by the PR technique. During the whole Hg^0 removal cycles, chemisorption dominated, with the initial adsorption stage and the external mass-transfer process playing important roles.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"59 1","pages":"80-90"},"PeriodicalIF":3.2,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83014027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}