汽轮机转子热应力解析计算中的误差分析与简化计算

文中分析了放热系数和物性参数随实际工况变化对汽轮机转子热应力解析计算结果的影响,提出一种修正计算方法和简化计算公式。     

微光夜视仪空间棱镜架有限元热分析

空间棱镜架是单管双目微光夜视仪机械结构重要组成部分,其设计的好坏直接影响夜视仪系统成像质量和整机性能.文中基于有限元分析理论,利用ANSYS研究了单管双目微光夜视仪空间棱镜架的温度场及热应力.通过建立结构三维有限元分析模型,计算棱镜架温度场分布,对热应变和热应力进行求解,完成空间棱镜架有限元热分析.在满足工作环境从-30℃到50℃变化条件下,对比有限元热分析求解结果,选取改性聚苯醚作为结构最终材料,改进初始结构,完成夜视仪空间棱镜架设计.     

硅酸盐钻井液稳定井壁机理分析

以硅酸钾或硅酸钠为主要处理剂的硅酸盐钻井液体系近年来应用较多,该类体系具有很强的稳定井壁能力和环境相容性,其稳定井壁机理不同于其它常用水基泥浆体系。文中在介绍该类泥浆体系及应用情况基础上详细分析了其稳定井壁机理,认为有四个方面：①快速在近井壁堵塞孔隙和微缝,阻止滤液进入地层,减少压力穿透;②抑制页岩中粘土矿物水化;③硅酸盐和粘土矿物发生反应;④其它无机盐的协同稳定作用。     

高温换热设备管口保护结构热应力的分析与计算

对高温换热设备管口热保护结构建立了热应力计算的物理模型和数学模型 ,并采用有限元法对热应力进行了计算。计算结果表明 ,由于在高温换热设备管口热保护区存在温度畸变 ,使得瓷保护套管内产生较大剪应力 ,从而造成瓷套管的热应力破坏。     

考虑热粘弹性力学性质时低碳钢材料的非定常热应力计算

文中从考虑低碳钢材料的热粘弹性力争性质出发，依据变温粘弹性松弛型本构方程及热传导理论，对低碳钢材料的非定常热应力进行了计算．     

考虑热粘弹性力学性质时低碳钢材料的非定常热应力计算

文中从考虑低碳钢材料的热粘弹性力学性质出发，依据变温粘弹性松弛型本构方程及热传导理论，对低碳钢材料的非定常热应力进行了计算。     

高温换热设备管口保护结构热应力的分析与计算

对高温换热设备管口热保护结构建立了热应力计算的物理模型和数学模型，并采用有限元法对热应力进行了计算。计算结果表明，由于在高温换热设备管口热保护区存在温度畸变，使得瓷保护套管内产生较大剪应力，从而造成瓷套管的热应力破坏。     

Mechanical Study of Nano-ceramic Thermal Barrier Coatings by the Equation of Phonon Radiative Transfer

基于辐射模型的微、纳米尺度陶瓷热涂层的热力学性能分析

张士元¹,郑百林²,贺鹏飞²

（1 福建工程学院 土木工程系,福建福州,350007;2 同济大学 航空航天与力学学院,上海,200092）

摘要：温度场、热应力（特别是剥离力）和J积分对于热冲击下的热涂层具有重要作用,在微、纳米尺度上,能量传输机制与宏观尺度上有显著的不同。对于热冲击条件下微、纳米尺度陶瓷热涂层结构,采用声子辐射输运方程(EPRT)（用于纳米尺度陶瓷涂层）和傅里叶热传导定理（用于基底）相结合求得温度场,继而得到热应力和J积分。将这些结果与涂层和基底都采用傅里叶热传导定理计算的结果进行比较,同时分析了热物理特性（如弛豫时间和声子速度）对这些结果的影响。结果表明,用EPRT计算的温度、热应力和J积分,低于采用傅里叶热传导定理计算的结果。此外,TBCs的热物理性质对温度场和热应力的影响在TBCs表面和内部不同。

关键词:微纳尺度陶瓷热涂层,纯声子辐射模型,热应力,J积分

     

泥页岩水化膨胀压的理论计算方法

泥页岩水化膨胀可诱发或加剧井壁岩石受力平衡，水化膨胀压是泥页岩井段井眼不稳定研究中必须研究的内容，而直接测定泥页岩水化膨胀压相当困难。泥页岩水化膨胀压是其中粘土颗粒间的排斥力。文中介绍了根据双电层理论，用矿物学参数计算水化膨胀压的方法。这些参数包括比表面积，表面电荷密度、膨胀后孔隙水中离子浓度，双电层中反离子价数及粘土颗粒间距。还具体说明了计算步骤和这些参数的获取方法并给出了算例。     

定向井井眼轨迹与井壁稳定性关系研究

从力学角度分析南海西部海域涠洲XX油田的地层岩石特征,提出适合该油田的井壁稳定分析方法。基于适合该油田定向井的井壁稳定计算模型,分析井眼轨迹与井壁稳定的关系,并总结其规律。合理设计定向井井眼轨迹是预防涠洲XX油田井壁失稳的有效措施之一。     

裂缝面及井眼附近的应力分析

从力学角度出发,建立了川西致密气层井眼,裂缝面及地层的有限元模型,应用ANSYS软件仿真模拟了裂缝面与水平面面夹角的变化引起裂缝面上及井眼附近的应力变化,重点研究了水平裂缝面上及井眼附近的主应力和等效应力的应力等值线变化规律,随着地层裂缝倾角的增加,裂缝面上井眼附近的最大等效应力逐渐转移到井眼椭圆截在的短轴两端附近,研究结果对进一步研究井眼稳定,井壁崩落方向或裂缝面上的应力敏感性具有指导意义。     

蒸汽吞吐机理数值模拟与正交试验分析

目前蒸汽吞吐是稠油开发中最常用的生产方法,其开采机理主要为地层能量驱动、原油加热降黏、加 热改善油水相对渗透性、液体热膨胀和近井地带解堵。但是,关于各种机理对蒸汽吞吐贡献的大小问题却鲜有论 述。利用油藏数值模拟软件,采用正交试验分析方法进行研究的结果表明,这五种机理对吞吐采收率的贡献从大到 小的顺序为地层能量驱动、原油加热降黏、近井地带解堵、液体热膨胀和加热改善油水相对渗透性,并且前两者起决 定性的作用,是蒸汽吞吐能否取得较高采收率的关键。研究结果可指导设计人员高效地进行稠油油藏蒸汽吞吐开 发设计,同时可指导研究人员利用数值模拟软件对蒸汽吞吐进行数值模拟。     

An investigation of machine learning techniques to estimate minimum horizontal stress magnitude from borehole breakout

Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination, and breakout geometrical parameters, such as width and depth, have been used to estimate both horizontal stress magnitudes. However, the accuracy of minimum horizontal stress estimation from borehole breakout remains relatively low in comparison to maximum horizontal stress estimation. This paper aims to compare and improve the minimum horizontal stress estimation via a number of machine learning (ML) regression techniques, including parametric and non-parametric models, which have rarely been explored. ML models were trained based on 79 laboratory data from published literature and validated against 23 field data. A systematic bias was observed in the prediction for the validation dataset whenever the horizontal stress value exceeded the maximum value in the training data. Nevertheless, the pattern was captured, and the removal of systematic bias showed that the artificial neural network is capable of predicting the minimum horizontal stress with an average error rate of 10.16% and a root mean square error of 3.87 MPa when compared to actual values obtained through conventional in-situ measurement techniques. This is a meaningful improvement considering the importance of in-situ stress knowledge for underground operations and the availability of borehole breakout data.     

Numerical simulation on borehole breakout and borehole size effect using discrete element method

Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries, although there are critical research gaps that remain unfilled. In this paper, numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect, including temperature influence. The discrete element method(DEM) model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction. This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation. The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking. This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition, the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells. Based on the results, the higher temperature led to lower breakout initiation stress with same borehole size, and more proportion of shear cracks was generated under higher temperature. This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries. Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions, suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.     

冷却速度对SiCp/2024Al热残余应力影响的数值模拟

针对冷却速度对SiCp／2024Al复合材料热残余应力的影响，通过复合材料显微组织观察，根据复合材料的形貌特征，建立了平面应力状态的复合材料组织模型，利用有限元方法对SiCp／2024Al复合材料淬火和退火过程的热应力进行了数值模拟．结果表明，由于SiC增强颗粒与铝基体之间的热膨胀系数差异较大，热处理后颗粒和基体的界面附近产生很大的热残余应力场，同时基体发生塑性应变；冷却速度对复合材料热残余应力没有明显影响．     

颗粒形状对铝基复合材料热残余应力影响的有限元分析

通过复合材料显微组织观察，建立了平面应力状态的复合材料组织模型，利用有限元方法对Al2O3p/2024Al复合材料和SiCp/2024Al复合材料淬火过程的热应力进行了数值模拟，研究了颗粒形状对铝基复合材料淬火处理过程下热残余应力的影响．结果表明，由于增强颗粒与铝基体之间的热膨胀系数差异较大，淬火处理后颗粒和基体的界面附近产生很大的热残余应力场，同时基体发生塑性应变．     

预测钻井过程中井内温度分布的新模型

在钻井过程中,井内温度分布对钻井作业有较大的影响。在前人研究的基础上,考虑各种因素的影响,根据能量守恒原理,建立了循环和静止过程中井内温度分布的预测模型,并用有限体积法实现了该模型的求解。最后用现场试验数据对模型模拟结果进行了验证。该模型可用于计算井内钻井液的循环温度和静止温度,也可用于确定井眼周围地层的温度分布。     

岩石软弱面产状对井壁稳定性的影响

在连续介质力学井壁稳定性分析的基础上,采用简化的岩石软弱面地质模型和力学模型,计算分析了岩石软弱面倾角和倾斜方位角改变对直井,斜井井壁稳定性的影响。结果表明：相同作用条件下,岩石软弱面的稳定性明显低于基质岩块的稳定性,当井周围存在裂缝或节理等软弱面时,井壁的稳定性将受到软弱面的影响而明显降低;斜井条件下,井壁失 的位置和失稳的程度与软弱面的产状密切相关;直井条件下,井壁垮塌的方位将可能偏离原地最小水平主应力的方位,而主要取决于岩石软弱面的倾角和倾斜方位角。     

反循环压井井筒温度场计算与分析

反循环压井过程中,井筒温度场受环境及压井液物理性质等外部参数影响十分明显。从反循环压井工艺特点出发,以传热学基本理论为基础,通过理论推导,得到反循环压井过程井筒温度场计算模型。对影响反循环压井过程中井筒温度的因素进行分析,结果表明,在压井过程中,泥浆排量、泥浆比热、地温梯度、井深以及压井循环时间和泥浆入口温度对循环过程中井下温度分布的影响较大;调整泥浆排量和泥浆入口温度可以作为调节井筒温度的有效途径。     

Digital microstructure insights to phase evolution and thermal flow properties of hydrates by X-ray computed tomography

Natural gas-hydrates are valuable energy resource with rich deposits, and their thermal transport and thermal dynamic mechanical behaviors significantly affect the long-term production process and phase change-based thermal energy storage characteristics of these energy resources. This paper aims to propose novel relations to predict the thermophysical properties, to investigate the hydrate phase evolution in microstructures, and to study the thermal transport and thermal dynamic mechanical properties. Hydrates formation experiments in sandpack samples and ultrasonic wave tests are conducted with the aid of X-ray CT imaging. Digitalization microstructures models and variables are defined to describe the hydrate phase evolution, and novel relations are proposed to accurately predict the thermophysical properties based on the microporosity and ultrasonic wave velocities. The thermal transport and thermal dynamic mechanical properties in microstructures with hydrate, water, residuary pore and grain phases are studied. Results show that the average errors of porosity, P-wave and S-wave velocities between the experimental data and computed results by the proposed relations are less than 5%, indicating the accuracy and reliability of the proposed method. The temperature fraction decreases with increasing underground temperature and decreasing hydrate saturation. The thermal stress and thermal displacement increase as temperature and hydrate saturation increase. There are strong anisotropy for the temperature fraction, thermal stress and thermal displacement during the thermal transport of hydrates.