Development of a new irradiation-embrittlement prediction model for reactor pressure-vessel steels

Predicting the transition-temperature shift(TTS)induced by neutron irradiation in reactor pressure-vessel(RPV)steels is important for the evaluation and extension of nuclear power-plant lifetimes.Current prediction models may fail to properly describe the embrittlement trend curves of Chinese domestic RPV steels with relatively low Cu content.Based on the screened surveillance data of Chinese domestic and similar international RPV steels,we have developed a new fluencedependent model for predicting the irradiation-embrittlement trend.The fast neutron fluence(E>1 MeV)exhibited the highest correlation coefficient with the measured TTS data;thus,it is a crucial parameter in the prediction model.The chemical composition has little relevance to the TTS residual calculated by the fluence-dependent model.The results show that the newly developed model with a simple power-law functional form of the neutron fluence is suitable for predicting the irradiation-embrittlement trend of Chinese domestic RPVs,regardless of the effect of the chemical composition.

Exploration on the Optimization Strategy for the Layup of Composite Material Pressure Vessels Based on Advanced Algorithms

This study aims to explore the influence of the laying angle on the pressure shell structure made of composite materials under the condition of a fixed shape. By using a composite material composed of a mixture of T800 carbon fiber and AG80 epoxy resin to design pressure vessels, this material combination can significantly improve the interlaminar shear strength and heat resistance. The article elaborates on the basic concepts and failure criteria of composite materials, such as the maximum stress criterion, the maximum strain criterion, the Tsai-Hill criterion, etc. With the help of the APDL parametric modeling language, the arc-shaped, parabolic, elliptical, and fitting curve-shaped pressure vessel models are accurately constructed, and the material property settings and mesh division are completed. Subsequently, APDL is used for static analysis, and the genetic algorithm toolbox built into Matlab is combined to carry out optimization calculations to determine the optimal laying angle. The research results show that the equivalent stress corresponding to the optimal laying angle of the arc-shaped pressure vessel is 5.3685e+08 Pa, the elliptical one is 5.1969e+08 Pa, the parabolic one is 5.8692e+08 Pa, and the fitting curve-shaped one is 5.36862e+08 Pa. Among them, the stress distribution of the fitting curve-shaped pressure vessel is relatively more uniform, with a deformation of 0.568E−03 m, a minimum equivalent stress value of 0.261E+09 Pa, a maximum equivalent stress value of 0.537E+09 Pa, and a ratio of 0.48, which conforms to the equivalent stress criterion. In addition, the fitting curve of this model can adapt to various models and has higher practical value. However, the stress distribution of the elliptical and parabolic pressure vessels is uneven, and their applicability is poor. In the future, further exploration can be conducted on the application of the fitting curve model in composite materials to optimize the design of pressure vessels. This study provides important theoretical support and practical guidance for the design of composite material pressure vessels.

Finite Element Modeling of Variable Membrane Thickness for Field Fabricated Spherical (LNG) Pressure Vessels

This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.

Deformation mechanism and limit support pressure of cutting steel plate during connection between pipes in large spacing using pipe curtain structure method

The pipe curtain structure method(PSM)is a novel construction method to control ground deformation strictly.Compared with the traditional pipe-roofing and pipe jacking method,the connection between pipes in large spacings using PSM is widely acknowledged as a unique construction procedure.Further study on this connection procedure is needed to resolve similar cases in that the pipes are inevitably constructed on both sides of existing piles.Cutting the steel plate during the connection procedure is the first step,which is crucial to control the safety and stability of the surrounding environment and existing structures.The deformation mechanism and limit support pressure of the cutting steel plate during the connection between pipes in large spacings are studied in this paper,relying on the undercrossing Yifeng gate tower project of Jianning West Road River Crossing Channel in Nanjing,China.A modified 3D wedge-prism failure model is proposed using the 3D discrete element method.Combined with Terzaghi loose earth pressure theory and the limit equilibrium theory,the analytical solutions for the limit support pressure of the excavation face of the cutting steel plate are derived.The modified 3D wedge-prism failure model and corresponding analytical solutions are categorised into two cases:(a)unilateral cutting scheme,and(b)bilateral cutting scheme.The analytical solutions for the two cases are verified from the numerical simulation and in-situ data and compared with the previous solutions.The comparative analysis between the unilateral and bilateral cutting schemes indicates that the bilateral cutting scheme can be adopted as a priority.The bilateral cutting scheme saves more time and induces less ground deformation than the unilateral one due to the resistance generated from the superimposed wedge.In addition,the parametric sensitivity analysis is carried out using an orthogonal experimental design.The main influencing factors arranged from high to low are the pipe spacing,the cutting size,and the pipe burial depth.The ground deformation increases with the increased cutting size and pipe spacing.The pipe burial depth slightly affects the ground deformation if the other two factors are minor.Cutting steel plates in small sizes,excavating soil under low disturbance,and supporting pipes for high frequency can effectively reduce the ground surface subsidence.

水合物开采模拟超重力试验装置的研发及应用

天然气水合物是突破世界能源瓶颈的重要潜在能源,广泛分布于深海沉积物和陆域永冻土。水合物赋存在高压低温环境下,储层厚度达数十至百米,大尺度储层重力场显著影响其开采时的液气渗流、储层变形和传热过程,进而影响开采产气效率且可能诱发工程灾变。研发了一套能够在超重力场下模拟大尺度水合物储层长历时开采演变过程的离心模型试验装置,主要由高压釜系统、水合物制备模块、水压力控制模块、水合物开采模块、监测与响应模块组成。该装置能够在100g超重力下伺服调控高压釜内气液压力和温度环境,在模型尺度上有效再现水合物储层应力、温度和荷载条件。在系统介绍装置研发思路和技术特色的基础上,通过100g下水合物储层模型降压分解试验探析了原位等效重力场下储层不同深度处孔压演化规律及开采产气特性,再现了Nankai海槽原位试采产气速率峰值模式,为揭示水合物储层开采相变多相多场耦合机制和灾变防控提供了新的研究手段。

Impact of Revascularization on the Distal to Proximal Pressure Ratio in Case of Multiple Coronary Stenoses

Objective: In order to take a decision about the revascularization approach to be adopted, it is of fundamental importance to determine whether coronary artery stenoses induce ischemia or not. An index, named (Fractional Flow Reserve), based on pressure measurements has been proposed to this aim and is usually interpreted in terms of flows. The objective of this work is to compute simultaneously pressures and flow rates in the coronary network of patients with three-vessel disease, in order to study more precisely the relationship between these two quantities. Approach: 22 patients have been included in the study. Some pressure and flow rate measurements were collected during by-pass surgery. These clinical data allow determining parameters for a patient’s specific model, based on the electric/hydraulic analogy. Collateral pathways are included in the model, as well as the severity of the disease and the impact of revascularization. Main Results: For patients with stenoses on LAD, LCx, LMCA and occlusion of the RCA, the flow rate delivered to the right territory is of course a function of the aortic pressure, the left stenoses severity, and the pressure distal to the thrombosis. But it mainly depends on the capillary and collateral resistances, and on the proportion between them. Abnormal microvascular hemodynamics, may be present in patients with non-hemodynamic significant lesions as assessed by the pressure ratio. Complete revascularization with the 3 grafts is demonstrated to be fully justified. The direction of collateral flows may be reversed, depending on the pressure gradient. In any case, they remain low and become negligible when the 3 grafts are operating. Significance: Surgical decision based only on pressure measurements may miss some real hemodynamic problems due to the considered stenosis. This risk is even greater in case of serial stenoses.

基于直接数值模拟的压力容器入口射流湍流模型评价

采用基于谱元法的开源软件Nek5000对压力容器入口射流进行直接数值模拟(DNS)。压力容器模拟在环向简化为1/3的尺度,主管段雷诺数为63700,下降段雷诺数为14014,工质为碘化钠溶液。通过对常见物理量进行统计,构建高精度湍流数据库。并采用FLUENT对常见的壁面函数和湍流模型进行适应性评价,评价标准包括速度、湍动能和湍流黏度。结果表明:在上升段Stress-ω模型适用性最好;在下降段,Standard k-ω模型适用性最优。

基于巴特沃斯幅频特性的自适应粒子群算法

针对传统粒子群算法存在求解精度低和易陷入局部最优等问题,提出一种基于巴特沃斯幅频特性的自适应粒子群算法(Butterworth amplitude-frequency characteristics based adaptive particle swarm optimization algorithm,BAC-PSO).一方面,借助巴特沃斯幅频特性设计一种惯性权重非线性递减策略,均衡算法中粒子的局部与全局搜索能力;另一方面,通过S型函数的粒子群优化策略和Sigmoid函数改进位置更新方法,进一步提升算法的求解精度.以5个经典的测试函数为基准,将BAC-PSO算法与5种经典粒子群算法的性能进行对比,并将其应用到求解压力容器模型的设计问题中.实验结果表明,相较于其他经典粒子群算法,BAC-PSO算法的求解精度更高,收敛速度更快,稳定性更好.

考虑张力制度影响的碳纤维缠绕容器爆破性能预测与仿真插件开发

针对缠绕张力对碳纤维缠绕容器承载性能影响规律尚不明确的问题,基于ABAQUSTM软件开发了一套用户友好、自主选择性好且高效的插件工具,能够自动化完成模型建立和相关设置工作,实现了考虑多种缠绕工艺参数的容器结构精细化建模。基于该插件工具,对碳纤维缠绕容器在不同缠绕张力制度下的爆破性能进行了参数化分析,通过爆破试验验证了数值模型的有效性。对于直径为Ф155 mm和Ф474 mm的容器,90 N-80 N-60 N和200 N-180 N-160 N逐层减小的缠绕张力制度将提高容器的爆破性能;对于20 N和30 N递减张力制度,直径Ф474 mm容器的爆破压强随着内层张力的减小逐渐降低,当张力递减幅度增加时,容器的爆破压强趋于稳定,其下降幅度由16.79%减小到3.05%。此外,容器封头段与筒身段过渡区域的应变水平最高,为碳纤维缠绕容器的薄弱位置。

基于形态学脑网络连接模型预测脑小血管病患者的认知功能

目的 构建脑小血管病(cerebral small vessel disease, CSVD)患者形态学脑网络并预测其认知功能。方法 回顾性选择2020年1月至2024年2月南京医科大学附属江宁医院神经内科住院的老年CSVD患者64例。完善临床资料收集、认知功能评估、多模态磁共振成像扫描等。认知功能评估包括简易智能状态检查量表(mini-mental state examination, MMSE)评分和蒙特利尔认知评估量表(Montreal cognitive assessment, MoCA)评分。利用3D T_(1)加权成像基于Kullback-Leibler散度的相似性方法构建个体形态学脑网络,并结合连接组预测模型方法构建认知预测模型。结果 与MMSE评分和MoCA评分呈显著正相关的网络主要位于默认网络内,且利用显著正相关的形态学脑网络可有效预测个体MMSE评分和MoCA评分(r=0.795,P=4.436×10^(-15);r=0.794,P=4.974×10^(-15),P<0.01)。与MMSE评分和MoCA评分呈显著负相关的连接主要位于凸显/腹侧注意网络与其他网络之间,也可有效地预测个体MMSE评分和MoCA评分(r=0.766,P=1.679×10^(-13);r=0.850,P=6.915×10^(-19),P<0.01)。联合正相关与负相关连接网络,模型预测能力进一步提升(r=0.849,P=7.603×10^(-19);r=0.888,P=1.445×10^(-22),P<0.01)。结论 基于个体形态学脑网络可有效预测CSVD患者认知功能评分,可以作为早期预警CSVD相关认知障碍的一种便捷工具。

核电站安全壳打压试验泄压速率优化研究

核电站安全壳打压试验是机组大修期间的绝对关键路径工作,试验执行质量影响机组大修的总体进度。其中泄压速率作为决定安全壳打压试验工期的重要因素,通过建立核电站安全壳内外结构仿真模型,对25 kPa/h泄压速率时安全壳结构的安全性进行分析,提出泄压速率提升的理论依据,同时将模拟数据与缩尺安全壳模型进行对比验证,旨在为安全壳打压试验全面优化提供技术指导。

壳体单元与实体单元在大型压力容器吊装分析中的对比分析

研究压力容器各结构在吊装过程是否会发生塑性垮塌至关重要,但压力容器结构复杂,建立的有限元模型网格数量较多,降低了计算效率。基于此,提出用壳体单元模型替代实体单元模型的方法,并对结果的可靠性进行验证。研究结果表明,壳体单元最大Mises当量应力位置、变形趋势与实体单元相同,但由于实体单元存在峰值应力,实体单元的Mises当量应力大于壳体单元;壳体单元的薄膜应力与薄膜加弯曲应力均大于实体单元,实体单元的Mises当量应力大于壳体单元,这是因为壳体单元仅计算了一次应力与二次应力,无峰值应力,但不影响塑性垮塌评定。因此,对于非疲劳工况的压力容器,可采用壳体单元代替实体单元进行分析,以在减少计算量的情况下得到精确的数值解。

Crystal Structure Evolution of the Cu-rich Nano Precipitates from bcc to 9R in Reactor Pressure Vessel Model Steel

The crystal structure evolution of the Cu-rich nano precipitates from bcc to 9R during thermal aging was studied in nuclear reactor pressure vessel （RPV） model steels. The specimens, contained higher copper and nickel contents than commercially available one, were heated at 890 ~C for 0.5 h and then water quenched followed by tempering at 0（50 ~C for I0 h and aging at 400 ~C for 1000 h. It was observed that bcc and 9R orthogonal structure, as well as 9R orthogonal and 9R monoclinic structure, coexist in a single Cu-rich nano precipitate. Further analyses pointed out that Cu-rich nano precipitates of bcc structure were not stable, it may preferentially transform to 9R orthogonal structure and then to 9R monoclinic structure. This results showed that the crystal structure evolution of the Cu-rich nano precipitates was complex.

Flow stress behavior and constitutive modeling of 20MnNiMo low carbon alloy

The hot deformation behavior of 20 Mn Ni Mo low carbon alloy was investigated by isothermal compression tests over wide ranges of temperature(1223-1523 K) and strain rate(0.01-10 s^(-1)). According to the experimental true stress-true strain data, the constitutive relationships were comparatively studied based on the Arrhenius-type model, Johnson-Cook(JC) model and artificial neural network(ANN), respectively. Furthermore, the predictability of the developed models was evaluated by calculating the correlation coefficient(R) and mean absolute relative error(AARE). The results indicate that the flow stress behavior of 20 Mn NiM o low carbon alloy is significantly influenced by the strain rate and deformation temperature. Compared with the Arrhenius-type model and Johnson-Cook(JC) model, the ANN model is more efficient and has much higher accuracy in describing the flow stress behavior during hot compressing deformation for 20 Mn Ni Mo low carbon alloy.

基于深度学习主动视觉压力容器焊缝质量参数检测方法

压力容器A、B类对接焊缝是重要受力部位,其质量参数测量是焊接质量评估重要环节,本文研究基于深度学习主动视觉压力容器焊缝质量参数检测方法。提出多缺陷共存下焊缝参数计算方法,突破焊缝缺陷参数共存下存在焊缝质量参数难以计算或无法计算问题;开展编码-解码图像特征点提取网络(EDE-net)结构设计,较好实现焊缝表面参数特征点一次性准确提取;研究深度网络结构化通道剪枝方法,有效提高压力容器焊缝检测实时性能。以不同尺寸压力容器焊缝为实验对象,结果表明Resnet50骨干的EDE-net网络在模型整体压缩率CR=0.5下,单张图片提取时间由0.31 s降低到0.19 s,减少38.7%;第三方检测机构给出测试报告,装置同时测量对接焊缝(A、B类)焊缝5个参数耗时<0.63 s,测量误差允许误差≤0.08 mm。

换流变阀侧套管表带触指接触电阻数值计算

换流变阀侧套管的载流连接结构由中心导杆、载流端子以及表带触指组成。为了研究单片表带触指接触电阻与其所受压力的关系,基于Greenwood和Williamson接触模型(G–W模型)推导出单片表带触指接触电阻与压力的关系式,引入表带触指受力偏转修正和接触区域表面轮廓修正,得到3种不同电极组合(紫铜–紫铜、紫铜镀银–紫铜镀银、铝合金镀银–铝合金镀银)下单片触指接触电阻与压力的关系。同时,开展试验验证触指的受力偏转现象,测量了不同电极组合下单片触指随压力变化的接触电阻。研究结果表明:接触电阻随压力增大而减小,当单片触指压力为5~9 N时,修正后计算值与试验值的相对误差在10%以内,验证了修正的准确性。该研究可为提高套管电连接可靠性提供参考。

水下储气装置的水动力学特性分析

在复杂的海洋环境中,由于受到海流的影响,水下储气装置会发生疲劳破坏。针对这一问题,采用模型实验与数值模拟相结合的方法对水下储气装置的水动力学特性进行了研究。首先,选取气球状储气装置作为研究对象,依据相似原理设计了储气装置的缩尺模型,并对其进行了水动力学实验;然后,采用大涡模拟(LES)方法对储气装置进行了数值模拟,分析了其流场结构及受力特性;最后,通过对比数值模拟结果与实验结果,对数值模拟结果的可靠性进行了验证。研究结果表明:气球状储气装置的涡结构复杂、旋涡尺度丰富,并且装置后方存在明显的卡门涡街,0.4 m/s流速下平均阻力系数和升力系数分别稳定在0.09和0.04。该结果描述了气球状水下储气装置在复杂海洋环境中的水动力学特性,可以为储气装置的优化设计提供一定的理论依据。

基于知识蒸馏KD压力容器焊缝参数特征点提取实时性提升方法

压力容器对接纵焊缝是重要受力部位,对其测量是焊接质量评估的重要环节,从焊缝激光线中提取焊缝参数测量特征点是视觉焊缝测量重要内容。针对深度学习的焊缝图像参数特征点提取网络,其复杂骨干网络在模型部署、模型训练、模型正向传播时间成本而带来检测实时性限制问题,研究基于深度学习的压力容器焊缝图像特征点提取网络、焊缝参数特征点提取的相邻阶段数据融合KD模型的实时性提升方法,并以压力容器焊缝实验对象进行验证。结果表明,知识蒸馏KD训练后学生模型特征点提取精度有明显提升,且部署时间、单张图片提取时间分别减少70.8%、79.7%。

Mechanical analysis and reasonable design for Ti-Al alloy liner wound with carbon fiber resin composite high pressure vessel

To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.