ULTIMATE LOAD-BEARING CAPACITY OF CYLINDER DERIVED FROM AUTOFRETTAGE UNDER IDEAL CONDITION

According to the basic theory on autofrettage and according to the 4th strength theory, several parameters and their relations are studied under ideal condition, including σej/σy, the equivalent stress of total stresses at elastoplastic juncture; σei/σy, the equivalent stress of total stresses at inside surface; σej＇/σy, the equivalent stress of residual stresses at elastoplastic juncture; σei＇/σy, the equivalent stress of residual stresses at inside surface; and p/σy, load-bearing capacity of an autofrettaged cylinder. By theoretical study on relations between the parameters, noticeable results and laws are achieved： to satisfy ｜σei＇｜=σy. the relation between kj and k is, k^2lnkj^2-k^2-kj^2＋2=0, when k→∞, kj = √e = 1.648 72, as based on the 3rd strength theory, where k is the outside/inside radius ratio of a cylinder, kj is the ratio of elastoplastic juncture radius to inside radius of a cylinder; If the plastic region covers the whole wall of a cylinder, for compressive yield not to occur after removing autofrettage pressure, the ultimate k is k=-2.218 46 as based on the 3rd strength theory; With k=2.218 46, a cylinder＇s ultimate load-bearing capacity equals its entire yield pressure, or p/σy=21nk/√3; The maximum and optimum load-bearing capacity of an autofrettaged cylinder is just 2 times the loading which an unautofrettaged cylinder can bear elastically, or p/σy=2（k^2-1）/√3 k^2, and the limit of the load-bearing capacity of an autofrettaged cylinder is also just 2 times that of an unautofrettaged cylinder. The conclusions are the same as based on the 3rd strength theory, but some equations are different from each other.

Effect of Optimum Plastic Depth on Stresses and Load-bearing Capacity of Autofrettaged Cylinder

Autofrettage is an effective measure to even distribution of stresses and raise load-bearing capacity for （ultra-）high pressure apparatus. Currently, the research on autofrettage has focused mostly on specific engineering problems, while general theoretical study is rarely done. To discover the general law contained in autofrettage theory, by the aid of the authors’ previous work and according to the third strength theory, theoretical problems about autofrettage are studied including residual stresses and their equivalent stress, total stresses and their equivalent stress, etc. Because of the equation of optimum depth of plastic zone which is presented in the authors’ previous work, the equations for the residual stresses and their equivalent stress as well as the total stress and their equivalent stress are simplified greatly. Thus the law of distribution of the residual stresses and their equivalent stress as well as the total stress and their equivalent stress and the varying tendency of these stresses are discovered. The relation among various parameters are revealed. The safe and optimum load-bearing conditions for cylinders are obtained. According to the results obtained by theoretical analysis, it is shown that if the two parameters, namely ratio of outside to inside radius, k, and depth of plastic zone, kj, meet the equation of optimum depth of plastic zone, when the pressure contained in an autofrettaged cylinder is lower than two times the initial yield pressure of the unautofrettaged cylinder, the equivalent residual stress and the equivalent total stress at the inside surface as well as the elastic-plastic juncture of a cylinder are lower than yield strength. When an autofrettaged cylinder is subjected to just two times the initial yield pressure of the unautofrettaged cylinder, the equivalent total stress within the whole plastic zone is just identically equal to the yield strength, or it is a constant. The proposed research theoretically depicts the stress state of ultra-）high pressure autofrettaged cylinder more accurately and more reasonably and provides the reference for design of （ultra-）high pressure apparatus.

“Extreme utilization” theory and practice in gas storages with complex geological conditions

Based on more than 20-year operation of gas storages with complex geological conditions and a series of research findings, the pressure-bearing dynamics mechanism of geological body is revealed. With the discovery of gas-water flowing law of multi-cycle relative permeability hysteresis and differential utilization in zones, the extreme utilization theory targeting at the maximum amount of stored gas, maximum injection-production capacity and maximum efficiency in space utilization is proposed to support the three-in-one evaluation method of the maximum pressure-bearing capacity of geological body, maximum well production capacity and maximum peak shaving capacity of storage space. This study realizes the full potential of gas storage(storage capacity) at maximum pressure, maximum formation-wellbore coordinate production, optimum well spacing density match with finite-time unsteady flow, and peaking shaving capacity at minimum pressure, achieving perfect balance between security and capacity. Operation in gas storages, such as Hutubi in Xinjiang, Xiangguosi in Xinan, and Shuang6 in Liaohe, proves that extreme utilization theory has promoted high quality development of gas storages in China.

A Bio-inspired Mutual-hook Strategy for the Soft Finger to Improve Load-bearing Capacity and Grasping Stability

Soft grippers have great potential applications in daily life,since they can compliantly grasp soft and delicate objects.However,the highly elastic fingers of most soft grippers are prone to separate from each other while grasping objects due to their low stiffness,thus reducing the grasping stability and load-bearing capacity.To tackle this problem,inspired from the venus flytrap plant,this work proposes a mutual-hook mechanism to restrain the separation and improve the grasping performance of soft fingers.The novel soft gripper design consists of three modules,a soft finger-cot,two Soft Hook Actuators(SHAs)and two sliding mechanisms.Here,the soft finger-cot covers on the soft finger,increasing the contact area with the target object,two SHAs are fixed to the left and right sides of the finger-cot,and the sliding mechanisms are designed to make SHAs stretch flexibly.Experiments demonstrate that the proposed design can restrain the separation of soft fingers substantially,and the soft fingers with the finger-cots can grasp objects three times heavier than the soft fingers without the proposed design.The proposed design can provide invaluable insights for soft fingers to restrain the separation while grasping,thus improving the grasping stability and the load-bearing capacity.

“Extreme utilization”development theory of unconventional natural gas

In the process of unconventional natural gas development practice,the"extreme utilization"concept that focuses on"continuously breaking through the limit of development technology"is gradually formed,and supports the scale benefit exploration of unconventional gas in China.On this basis,the development theory of"extreme utilization"is proposed,its theoretical connotation together with development technologies of unconventional natural gas are clarified.The theoretical connotation is that,aiming at"extreme gas reservoirs","extreme techniques"are utilized to build subsurface connected bodies,expand the discharge area,and enlarge the production range,to obtain the maximum single-well production,extreme recovery,and eventually achieve the"extreme effect"of production.The series of development technologies include micro/nano-scale reservoir evaluation,"sweet spot"prediction,unconventional percolation theory and production capacity evaluation,optimization of grid well pattern,optimal-fast drilling and volume fracturing,and working regulation optimization and"integrated"organizing system.The"extreme utilization"development theory has been successfully applied in the development of unconventional gas reservoirs such as Sulige tight gas,South Sichuan shale gas,and Qinshui coalbed methane.Such practices demonstrate that,the"extreme utilization"development theory has effectively promoted the development of unconventional gas industry in China,and can provide theoretical guidance for effective development of other potential unconventional and difficult-to-recovery resources.

基于PCA-GA-XGBoost模型的吉林省水资源 承载力评价

为了提高水资源承载力评价的效率和准确性,提出了一种基于主成分分析(PCA)、遗传算法(GA)和极限梯度提升树(XGBoost)的指标评价模型。定义了以水资源、社会经济、生态环境为子系统的14项评价指标;采用主成分分析法对评价指标进行降维处理;基于梯度提升决策树对吉林省2011—2021年的水资源承载力进行评价分析,并利用遗传算法对极限梯度提升树中4个参数进行优化。结果表明:经主成分分析简化评价指标后,PCA-GA-XGBoost模型的相关系数等指标均优于GA-BP、GA-SVM、GA-XGBoost和XGBoost;2011—2021年吉林省水资源承载力位于0.192~0.724,为先上升后下降再上升趋势,承载力状况逐年改善;利用模型内置的特征值重要度排序功能,识别得出重要度最大的指标为每公顷化肥施用量(0.5307),是影响吉林省水资源承载力的关键因素。

基于改进深度极限学习机的光伏扩容用户识别方法

为准确识别违规的分布式光伏扩容骗补用户,提出一种基于改进深度极限学习机的光伏扩容用户识别方法。首先利用同地区光伏发电出力具有相似性的特点,通过余弦相似度对参考电站和待测站点进行预处理;然后应用麻雀搜索算法SSA(sparrow search algorithm)对深度极限学习机DELM(deep extreme learning machine)的权值参数优化,用预处理的数据集训练SSA-DELM拟合模型,并根据光伏扩容的特性计算扩容系数。实验结果验证了所提方法对分布式光伏违规扩容用户识别的有效性。

光伏发电参与电力平衡的可信容量分析

光伏发电是新型能源体系的重要组成部分,“十四五”期间我国光伏发电装机规模快速增长。光伏发电与天气强相关,随机性和波动性强,高比例光伏并网加大了电力系统平衡难度。通过详细分析高温天气下光伏发电出力特性,指出高温天气下光伏发电具有较高的日间顶峰能力,基于可信容量分析论证了提高极端高温天气下光伏发电参与电力平衡的合理性。最后计算验证了提高极端高温天气下光伏发电可信容量可降低日间电力平衡缺口,给出了光伏参与电力平衡的相关建议。

基于最小分支剩余容量的矿井通风网络极值流算法

为计算矿井最大通风量,针对最短增广链算法随机选取增广链,造成增广链缺失和极值流偏小的问题,提出一种基于最小分支剩余容量的矿井通风网络极值流算法。该算法在选取增广链时,选择中间分支剩余容量最小的增广链进行增广;每次增广完毕后,优先选择与增广完毕的增广链包含相同分支的增广链进行下一次增广。利用Excel Solver解算模型与BA无标度随机网络进行仿真实验,结果表明该算法比最短增广链算法解算时间短,且避免了增广链缺失。研究结论为矿井最大通风量的计算提供理论参考。

浅谈GB/T 19936.2-2024《齿轮FZG试验程序第2部分:高极压油的相对胶合承载能力FZG阶梯加载试验A10/16.6R/120》

GB/T 19936.2-2024是通过FZG阶梯加载试验来模拟实际工作条件下的高极压油环境,评估齿轮在高极压油条件下的相对胶合承载能力。本文对GB/T 19936.2-2024标准制定的背景意义及主要解决的问题进行了介绍,对标准的部分要点和试验参数进行了研究,并对试验程序和各载荷级的相关参数进行分析,为更好地理解该标准提供参考。

Influence of cyclic loading on the fracture toughness and load bearing capacities of all-ceramic crowns

The purpose of this study was to investigate how cyclic loading influenced the fracture toughness of hot-press lithium disilicate and zirconia core materials and whether there was an increase in the propensity for crown failure. Two types of all-ceramic crowns including the IPS e.max Press system （n=24） and the Lava zirconia system （n=24）, were selected. Sectioned specimens were subjected to cyclic loading with the maximum magnitude of 200 N （R=0.1） until two million cycles. The material properties including Young＇s modulus （E） and hardness （H） and the fracture toughness （K,c） of the core materials were evaluated using indentation methods （n= 12 each）. The load-bearing capacities of the specimens were examined by means of monotonic load to fracture （n=12 each）. It was found that the material properties, including E, Hand Knc, of the two types of dental ceramics, were reduced. Statistical analysis indicated that there were no significant influences of fatigue loading on material properties E and H for both types of dental ceramics or Kgc for zirconia, while for the IPS e.max Press core, K,c, which was parallel to the direction of the lithium disilicate crystals, was significantly reduced （P-0.001）. A conclusion was drawn that zirconia possesses high mechanical reliability and sustainable capacity to resist fatigue loading, while fatigue loading remarkably degraded the anisotropic mechanical behaviour of hot-press lithium disilicate ceramics.

极端暴雨下城市内涝模拟与应急响应能力评估

为探究极端暴雨对城市内涝积水特征和应急响应能力的影响,基于InfoWorks ICM模型构建郑州市金水区的某片区内涝模型,分析极端暴雨情景下的城市管网排水能力和内涝积水特征,基于ArcGIS网络分析模块评估公安、医疗和消防3类应急服务部门在单一和组合情景下的可达范围和响应时间,以此确定城市应急响应能力。结果表明:研究区管网排水能力整体较低,排水能力<3 a一遇的设计暴雨(3 a一遇,下同)的管道占比为50.15%,此类管道多分布于中部和南部,不能满足城市重要地区3~5 a的排水标准;淹没范围与管网排水能力和地表类型有着密切的联系,在较大除涝标准下,如20 a一遇和100 a一遇情景下积水呈现出南多北少的分布特征,而郑州2021年“7·20”特大暴雨情景下,北部和河流附近地区的积水面积较大;应急车辆涉水能力较高的服务部门在极端暴雨下的应急响应能力更高,100 a一遇和“7·20”情景下消防部门的响应能力最高,10 min内可达范围占比分别为78%和36%;多部门联合调度可有效提升应急响应能力,如100 a一遇情景下,5、10、15 min内联合调度的应急响应可达范围比最优部门(同一时间阈值下可达范围占比最大的部门)分别增加了16%、7%、4%。

复杂地质条件储气库“极限动用”理论与实践

针对复杂地质条件储气库,基于20余年的运行实践,结合储气库系列攻关成果,揭示了储气地质体承压动力学机制,发现了“多轮相渗滞后”和“分区差异动用”气水互驱渗流规律,提出了以“储气库储气最多、井注入产出能力最大、空间利用效率最高”为目标的复杂地质条件储气库“极限动用”理论,形成了储气地质体极限承压、井极限产能、储气空间极限调峰能力三位一体的评价方法。实现了储气地质体在上限压力条件下获得最大储气空间(库容)、充分发挥地层-井筒气体流动协调的井极限产能以及满足有限时率不稳定渗流条件的最佳井网密度,获得下限压力条件下的最大调峰能力,达到安全和能力的双重极限效果。新疆呼图壁、西南相国寺、辽河双6等地下储气库的运行实践证明,“极限动用”理论有力推动了中国储气库业务高质量发展。

郑州“7·20”极端降雨的城市内涝模拟及风险评估

为科学认识和有效评估极端降雨对城市内涝风险的影响,构建了基于InfoWorks ICM的郑州市金水区老城区内涝模型,以郑州“7•20”极端降雨为例,评估了城市管道排水能力,模拟分析了城市内涝淹没情况,改进了英国基于行人安全的内涝风险评估公式中的部分参数。结果表明:郑州市金水区老城区58.54%的排水管道不能满足郑州市城市规划管理技术规定;在郑州“7•20”极端降雨中,排水能力较低的管道首先被充满,地面积水来时快、退时缓,最大满管率高达98.69%,发生时刻为当日18:00前后;由改进后的内涝风险等级评估方法计算可知,郑州市金水区老城区高风险以上区域占70.43%。该方法更适用于极端降雨下内涝风险等级的评估,可为城市极端降雨防控提供一定的技术参考。

极端高温下10kV电缆中间接头载流量分析

随着世界各地夏季环境温度不断升高,电缆中间接头的工作环境正在恶化。为此,文中基于有限元法建立10 kV三芯电缆及其中间接头仿真模型,分析不同环境温度和不同电流下中间接头的温度分布。首先,开展温升试验,得到电缆中间接头表面的稳态温度,验证仿真模型的准确性;然后,拟合不同环境温度下中间接头高压载流导体表面温度与电流的函数关系,以此可以计算不同极端环境温度下中间接头的极限安全载流量。结果表明,环境温度升高对中间接头高压载流导体表面的温度分布趋势几乎没有影响,在外护套外表面处也满足此规律。中间接头高压载流导体表面温度与电流近似成二次函数关系。当电流幅值为480 A、环境温度为75℃时,高压载流导体表面与外护套外表面最高温度分别是环境温度为30℃时的1.57倍与1.69倍。当环境温度超过55℃时,按照国标规定的持续允许载流量会使中间接头高压铜导体表面温度超过最高允许运行温度90℃。考虑到自2020年起夏季环境温度持续增加,现行国标中10 kV铜导体三芯交联聚乙烯绝缘电缆中间接头的持续允许载流量须被修正。

锂离子电池负极析锂问题的分析及对策

随着锂离子电池应用领域的拓宽和电子产品的快速迭代,对安全性能和极速充电能力提出了更高的要求。在锂离子电池的极速充电过程,易在石墨负极表面析出金属锂,产生电池容量衰减、安全风险增加、使用寿命缩短等诸多问题。阐述了负极析锂的机理。列举了负极析锂的三种分布状态,并说明了这些分布状态形成的原因。分析了负极析锂的影响因素,如电芯N/P值、充电温度、充电倍率、过充、Overhang设计。提出了解决负极析锂的对策。对负极析锂问题的研究现状进行了总结,并提出了未来负极析锂的可能研究方向。

基于XGBoost-SHAP的钢管混凝土柱轴向承载力预测模型

为了可靠、准确地预测钢管混凝土(CFST)柱的轴向承载力,建立和解释集成机器学习的CFST柱轴向承载力预测模型.使用马氏距离评估CFST柱数据库质量,通过极限梯度提升(XGBoost)算法建立CFST柱轴向承载力预测模型,使用K折交叉验证(K-Fold CV)和树结构概率密度估计(TPE)算法寻找模型的最优超参数组合.采用不同评价指标将优化后XGBoost模型的预测值与已有方法和未优化XGBoost模型的计算值比较.使用SHAP方法给出XGBoost模型预测结果的整体和局部的解释.结果表明,经过超参数调整优化的XGBoost模型的性能超越了相关规范和经验公式的性能,且SHAP方法能够有效地解释XGBoost模型的输出.

基于“情景-应对”的随县柳林镇“8·12”山洪灾害推演

【目的】降雨诱发的山洪具有暴涨暴落特点,其防御及应急也一直是我国防汛减灾工作中的薄弱环节。为指导山洪灾害应急救援工作,减少暴雨山洪带来的影响及损失,【方法】以湖北省随州市柳林镇“8·12”山洪灾害为研究对象,基于“情景-应对”式情景构建方法,采用无人机航测技术提取柳林镇地形、植被等信息要素,构建柳林镇“8·12”山洪事前、事中、事后情景;在此基础上耦合“水文-水动力”模型推演了暴雨诱发山洪的全过程,从而对本次灾害应急过程进行了深入分析。【结果】结果显示:柳林镇“8·12”山洪在12日3时30分左右洪水位开始猛增、2.5 h后即达到峰值,最高淹没深度超5 m,峰值过后3.5 h洪水基本褪却,极快的流速和暴涨的水位导致有效转移时间不足1 h。【结论】结果表明:基于“情景-应对”式灾害情景构建方法,可全景式再现山洪灾害孕灾-发灾-致灾全过程;耦合水文-水动力模型在无人机获取的高精度地形数据基础上具有较高的适用性;能力评估揭示了本次山洪灾害重大人员伤亡的主要原因是气象预警能力不足、人员撤离不及时以及应急救援力量薄弱。

Extremely low friction on gold surface with surfactant molecules induced by surface potential

An extremely low friction state was observed on the gold surface induced by applying a specific negative potential in cationic surfactant solution.The friction force showed a remarkable reduction from 8.3 to 3.5×10−2 nN(reduced by 99.6%)with increasing the period of negative applied potential,and the final friction coefficient could reduce down to 3×10−4.The extremely low friction state was robust,and it also exhibited an excellent load bearing capacity,which cannot be damaged by a high load.Moreover,the extremely low friction state achieved under negative applied potential could keep stable even after the removal of potential,but failed in a short time,once a specific positive potential was applied.It was demonstrated that there was a stable electro-adsorption of surfactant molecules on the gold surface induced by applying a negative potential,leading to the formation of a bilayer structure on the gold surface.The hydration layers of the bilayer on the gold surface and micelles on the silica probe provided a shear plane with an extremely low shear strength,leading to the extremely low friction state on the gold surface.This study provides a method to achieve extremely low friction state by applied potential.

我国松香市场容量和产量预测分析

在对世界、国内、云南脂松香产业历史和现状进行分析研究的基础上,探寻市场需求量与GDP变化的规律和相关数学模型。以云南为例对省内、国内、国外市场的近、中、远3个阶段的脂松香需求量和产量,采用数量化的市场预测方法和手段——松香需求弹性系数分析法进行分析预测。研究分析表明,松香的市场需求量和产量与省内、国内、世界的年GDP值的变化密切相关,收集整理相关信息资料,求出各个市场需求的弹性系数,建立相关数学模型,对云南松香的市场极限容量和产量进行预测分析,通过分析论证得出较为可靠的预测值。