Stress analysis of functionally graded rotating discs: analytical and numerical solutions

This study deals with stress analysis of annular rotating discs made of functionally graded materials（FGMs）.Elasticity modulus and density of the discs are assumed to vary radially according to a power law function,but the material is of constant Poisson＇s ratio.A gradient parameter n is chosen between 0 and 1.0.When n = 0,the disc becomes a homogeneous isotropic material.Tangential and radial stress distributions and displacements on the disc are investigated for various gradient parameters n by means of the diverse elasticity modulus and density by using analytical and numerical solutions.Finally,a homogenous tangential stress distribution and the lowest radial stresses along the radius of a rotating disc are approximately obtained for the gradient parameter n = 1.0 compared with the homogeneous,isotropic case n = 0.This means that a disc made of FGMs has the capability of higher angular rotations compared with the homogeneous isotropic disc.

SCATTERING OF HARMONIC ANTI-PLANE SHEAR STRESS WAVES BY A CRACK IN FUNCTIONALLY GRADED PIEZOELECTRIC/PIEZOMAGNETIC MATERIALS

In this paper, the dynamic behavior of a permeable crack in functionally graded piezoelectric/piezomagnetic materials is investigated. To make the analysis tractable, it is assumed that the material properties vary exponentially with the coordinate parallel to the crack. By using the Fourier transform, the problem can be solved with the help of a pair of dual integral equations in which the unknown is the jump of displacements across the crack surfaces. These equations are solved to obtain the relations between the electric filed, the magnetic flux field and the dynamic stress field near the crack tips using the Schmidt method. Numerical examples are provided to show the effect of the functionally graded parameter and the circular frequency of the incident waves upon the stress, the electric displacement and the magnetic flux intensity factors of the crack.

SCATTERING OF THE HARMONIC STRESS WAVE BY CRACKS IN FUNCTIONALLY GRADED PIEZOELECTRIC MATERIALS

The present paper considers the scattering of the time harmonic stress wave by a single crack and two collinear cracks in functionally graded piezoelectric material （FGPM）. It is assumed that the properties of the FGPM vary continuously as an exponential function. By using the Fourier transform and defining the jumps of displacements and electric potential components across the crack surface as the unknown functions, two pairs of dual integral equations are derived. To solve the dual integral equations, the jumps of the displacement and electric potential components across the crack surface are expanded in a series of Jacobi polynomials. Numerical examples are provided to show the influences of material properties on the dynamic stress and the electric displacement intensity factors.

THERMAL STRESSES RELAXATION DESIGN OF Ni/NiFe_(2)O_(4) SYSTEM FUNCTIONALLY GRADED CERMET INERT ANODE

The thermal stresses relaxation of Ni/NiFe2O4 system functionally graded cermet inert anode for aluminum electrolysis was optimally designed. The transient thermal stresses of the inert anode under complex boundary condition during high-temp （955℃） electrolysis were calculated using the finite-element software ANSYS, the influence of different parameters on the distribution of the thermal stresses were analyzed. The results showed that, during the process of thermal shock, the thermal hoop tensile stress on the surface of the anode is very large, which is possibly the major cause of anode crack; when the radius of the anode is between 0.05-0.15m, a range that can be realized by recent manufacturing technology, the optimum composition distribution exponent p is 0.25; The hoop tensile stresses reduce with the decrease of anode scale and also decrease with the decrease of the convection coefficient between the electrolyte and the anode.

MICROSTRUCTURE AND THERMAL STRESS RELAXATION OF ZrO_2－Ni FUNCTIONALLY GRADED MATERIAL

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DYNAMIC STRESS FIELD AROUND THE MODE Ⅲ CRACK TIP IN AN ORTHOTROPIC FUNCTIONALLY GRADED MATERIAL

The problem of a Griffith crack in an unbounded orthotropic functionally graded material subjected to antipole shear impact was studied. The shear moduli in two directions of the functionally graded material were assumed to vary proportionately as definite gradient. By using integral transforms and dual integral equations, the local dynamic stress field was obtained. The results of dynamic stress intensity factor show that increasing shear moduli's gradient of FGM or increasing the shear modulus in direction perpendicular to crack surface can restrain the magnitude of dynamic stress intensity factor.

Evaluation of strongly singular domain integrals for internal stresses in functionally graded materials analyses using RIBEM

An accurate evaluation of strongly singular domain integral appearing in the stress representation formula is a crucial problem in the stress analysis of functionally graded materials using boundary element method.To solve this problem,a singularity separation technique is presented in the paper to split the singular integral into regular and singular parts by subtracting and adding a singular term.The singular domain integral is transformed into a boundary integral using the radial integration method.Analytical expressions of the radial integrals are obtained for two commonly used shear moduli varying with spatial coordinates.The regular domain integral,after expressing the displacements in terms of the radial basis functions,is also transformed to the boundary using the radial integration method.Finally,a boundary element method without internal cells is established for computing the stresses at internal nodes of the functionally graded materials with varying shear modulus.

Displacements, Strains, and Stresses Investigations in an Inhomogeneous Rotating Hollow Cylinder Made of Functionally Graded Materials under an Axisymmetric Radial Loading

In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted. We have considered the rotating hollow cylinder submitted to an asymmetric radial loading. It is assumed that, because of the functional graduation of the material, the mechanical properties such as Young elastic modulus and the density varies in the radial direction, in accordance with a the power law function. The inhomogeneity parameter was selected between -1 and 1. On the basis of the second law of Newton, Hooke’s law and the strain-stress relationship, we established the differential equation which governs the equilibrium for a rotating hollow cylinder. We found the analytical solution and compared to the numerical solution obtained by using the shooting method and the fourth order Runge-Kutta algorithm. The analytical and numerical results lead to the conclusion that the magnitude of the tangential stresses is greater than that of the radial stresses. The changes due to the graduation of FGM does not produce consistent variations in the distribution of radial stresses, but strongly affects the distribution of tangential stresses. The tangential stresses, tangential strains and displacements are much higher at the inner surface of the cylinder wall. The internal radial pressure intensely affects the radial stresses and the radial strain.

Effect of Initial Stress on a Thermoelastic Functionally Graded Material with Energy Dissipation

In this paper we introduce the effect of initial stress on a magneto-thermoe- lastic functionally graded material (FGM) with Green Naghdi theory with energy dissipation. A system of PDE was obtained. The normal mode analysis method is used to convert these equations into ODE and get the analytical solution to write expressions for displacements, temperatures, stresses. Some comparisons carried out to view the initial stress influence on the field variables. Numerical results are graphed to view the influence of initial stress. Some particular cases are deduced in this study.

收敛约束法在挤压性围岩隧道中的应用

由于挤压性围岩隧道围岩性质与应力环境的特殊性,其围岩特征曲线与常规隧道有明显差异。为研究挤压性围岩隧道围岩-支护相互作用关系,考虑支护效应修正围岩特征曲线,研究不同变形等级对修正围岩特征曲线的影响规律,优化挤压性围岩双线铁路隧道初期支护。研究结果表明,毛洞状态下,受双线隧道断面应力集中影响,拱脚和墙脚为安全控制位置;随着变形等级和侧压力系数增加,支护特征曲线与修正围岩特征曲线不再相交;Ⅰ、Ⅱ级变形采用单层支护可满足安全要求,锚杆只需布置在拱部和边墙位置,Ⅱ级及以上变形锚杆需要全环布置;Ⅳ级变形在采用双层支护的同时,需考虑改善洞室形状、超前加固等措施。

P110S钢级油管管体断裂原因

某油井P110S钢级油管接箍下方8 m位置处发生断裂,采用宏观观察、化学成分分析、金相检验、扫描电镜和能谱分析、X射线衍射分析等方法对油管断裂原因进行分析。结果表明:该批油管力学性能不稳定,油管断口上的腐蚀产物主要为FeS;油管的强度较高、使用温度较低且质量较大,导致油管内部形成硫化物应力腐蚀开裂。

高温对香菇菌丝生理特性的影响及胁迫等级构建

以香菇(Lentinula edode)‘豫香1号’为参试菌株,模拟夏季高温季节气温变化特点,设置15个高温胁迫处理:H1(30℃,12 h)、H2(33℃,12 h)、H3(33℃,24 h)、H4(33℃,48 h)、H5(36℃,48 h)、H6(39℃,4 h)、H7(39℃,8 h)、H8(39℃,12 h)、H9(39℃,48 h)及H10~H15(36℃每天4 h,连续2、4、6、8、10、12 d),对照在25℃下培养(CK),研究高温胁迫对香菇菌丝生长、细胞形态,胞外漆酶、蛋白酶、纤维素酶活性,邻氨基苯甲酸合酶(TrpE)、6磷酸-海藻糖合成酶(TPS)、过氧化氢(H_(2)O_(2))含量,活性氧(ROS)水平的影响。通过主成分分析选取关键生理指标,计算不同处理的高温胁迫指数(Z),根据Z值划分胁迫等级,引入胁迫积温指数(ATSI)建立高温和持续时间的定量关系。结果表明,随胁迫温度升高及时间延长,香菇菌丝生长速度降低,菌丝胞外漆酶和羧甲基纤维素酶活性下降,TrpE、TPS、H_(2)O_(2)含量和ROS水平上升。以H_(2)O_(2)、TrpE、TPS含量和胞外漆酶活性为关键指标,根据Z值将高温胁迫划分为4个等级,轻度(1.5<Z≤3.0)、中度(3.0<Z≤4.5)、重度(4.5<Z≤6.0)、特重度(6.0<Z)。处理H1~H5和H10~H15的Z值与其ATSI值呈极显著正相关,Z值随ATSI值的变化较小;处理H6~H8的Z值与其ATSI值呈显著正相关,但Z值随ATSI值的变化较大;处理H9受高温胁迫后,菌丝完全不能恢复生长。研究结果可为香菇栽培温度调控管理及高温灾害防御提供参考。

基于“脾失运化”探讨运脾法调节多囊卵巢综合征内质网应激作用

多囊卵巢综合征(PCOS)是临床常见的异质性疾病,生殖障碍和代谢异常为本病两大病理特征。内质网应激指的是由于多种因素导致未折叠和(或)蛋白质聚集,通过恢复蛋白质正确的折叠方式的一种真核细胞的适应性反应。通过对脾主运化理论的古籍文献梳理发现,脾脏运化水谷,将精微物质布散周身的功能与现代医学中内质网在细胞中的重要作用有着类似之处,即通过承担蛋白质折叠和钙储存等多项任务,保证细胞能够正常发挥生理功能。若脾失运化,痰湿阻滞是本病的核心病机,现代研究认为内质网应激能够较好地阐释脾失运化的发生学原理,这与中医学的病机认识相同。因本病的发病机制与内质网应激存在相似之处,即其发生发展均与炎症、氧化应激、雄激素过多和胰岛素合成及分泌异常等相关。内质网应激的发生可能在PCOS的疾病进展中扮演着重要角色。运脾法能够延缓内质网应激的发生,同时也可有效缓解PCOS的肥胖、胰岛素代偿性增高等相关特征。因此,缓解内质网应激有望成为治疗本病的新思路。健运脾气,补益脾阳为本病治疗大法,从恢复脾运的角度调控内质网应激,以期为改善PCOS相关临床症状提供不同的治疗角度。

高海拔地区18 kV水轮发电机定子绕组端部防晕技术研究

为满足海拔高度为2 500 m的某大型水电站18 kV水轮发电机的防晕要求,本文从理论方面分析了目标海拔高度下的空气击穿场强及影响因素,并通过建立定子绕组端部三维仿真模型评估了端部电场特性,分析了间隙距离与绑扎结构对端部斜边电场的影响,确定了定子绕组端部斜边最小间隙距离控制在15 mm的方案。最后,在构建的大型高海拔环境模拟试验室完成了18 kV水轮发电机定子线圈和绕组的防晕性能进行测试验证。结果表明:该18 kV水轮发电机的防晕性能良好,满足在2 500 m海拔高度下的防晕要求。

表面效应对热-机多孔悬臂纳米梁力学性能的影响

表面效应对纳米结构的力学性能有重要影响。飞机上很多微纳尺度的结构可简化为悬臂梁。本工作分析表面效应对随从载荷作用下梯度多孔材料纳米悬臂梁在高温环境下非线性力学响应的影响。基于GurtinMurdoch表面弹性理论和非线性梁理论,建立梯度多孔材料梁在随从载荷以及温度场中的非线性控制微分方程。假定梯度多孔材料的性能在整个厚度范围内连续变化,且沿厚度呈两种余弦形式的非均匀孔隙率分布模式。采用打靶法求解梯度多孔材料悬臂纳米梁在热-随从载荷下的非线性力学响应。获得各种孔隙率系数和不同非均匀升温下悬臂纳米梁非线性力学响应的数值解,详细讨论材料表面弹性常数和表面应力对纳米悬臂梁力学响应的影响。结果表明:不同孔隙率系数和不同非均匀升温下梁的力学行为是不同的;纳米梁表现出十分显著的表面效应。

弹性支撑功能梯度压电多孔微圆柱壳的自由振动分析

旨在研究热-力-电载荷下弹性支撑功能梯度压电多孔微圆柱壳的自由振动。首先,建立弹性支撑功能梯度压电多孔微圆柱壳动力学模型;然后,应用三阶剪切变形壳体理论和修正的偶应力理论,推出弹性支撑功能梯度压电多孔微圆柱壳模态频率的解析解;最后,通过数值算例分析了微圆柱壳模态频率的影响因素。结果表明:Pasternak弹性支撑比Winkler弹性支撑更有利于提高微圆柱壳的模态频率;改变弹性支撑的刚度系数、轴向力、外加电压、孔隙分布、材料体积分数指数和结构尺寸可调节微圆柱壳的模态频率;孔隙体积分数越大,温度或轴向力对模态频率的影响越大,而电压对模态频率的影响则越小;不同材料指数下,增大孔隙体积分数对模态频率的影响趋势不同;弹性支撑会减弱温度、轴向力和电压对模态频率的影响,对薄圆柱壳或短圆柱壳模态频率的影响较为显著。

急性脊髓损伤患者早期血清标志物与AISA分级的相关性

背景:目前临床针对急性脊髓损伤严重程度的评估方法存在一定局限性,亟需一种快速、精准的评估手段。目的:分析急性脊髓损伤患者血清内相关氧化应激、神经损伤指标表达量与疾病严重程度的相关性。方法:选择2020年8月至2022年5月濮阳市中医医院收治的患者65例,其中急性脊髓损伤患者32例(试验组),单纯脊柱骨折患者33例(对照组),入院8 h内,评估患者美国脊髓损伤协会(ASIA)残损分级及神经功能评分,采集静脉血样本来检测血清中超氧化物歧化酶、丙二醛、谷胱甘肽、一氧化氮、神经胶质纤维酸性蛋白和神经元特异性烯醇化酶的水平,分析上述血清指标与ASIA残损分级、神经功能评分的相关性。结果与结论:(1)与对照组相比,试验组患者血清超氧化物歧化酶、谷胱甘肽水平降低(P <0.001),丙二醛、一氧化氮、神经胶质纤维酸性蛋白和神经元特异性烯醇化酶水平升高(P <0.01);(2)Pearson或Spearman相关分析显示,试验组患者血清中超氧化物歧化酶、谷胱甘肽水平与AISA残损分级呈正相关(r=0.862 4,0.849 3,P <0.01),丙二醛、神经胶质纤维酸性蛋白、神经元特异性烯醇化酶水平与AISA残损分级呈负相关(r=-0.866 1,-0.638 1,-0.746 6,P <0.001),一氧化氮与AISA残损分级无明显相关性(r=-0.177 5,P> 0.05);试验组患者血清中谷胱甘肽水平与AISA感觉功能评分呈正相关(r=0.569 9,P <0.001),丙二醛、神经胶质纤维酸性蛋白、神经元特异性烯醇化酶与AISA感觉功能评分呈负相关(r=-0.574 1,-0.376 2,-0.708 6,P <0.05),超氧化物歧化酶、一氧化氮水平与AISA感觉功能评分无明显相关性(r=0.230 8,-0.099 2,P> 0.05);试验组患者血清超氧化物歧化酶、谷胱甘肽水平与ASIA运动功能评分呈正相关(r=0.380,0.524 7,P <0.05),丙二醛、神经胶质纤维酸性蛋白、神经元特异性烯醇化酶水平与ASIA运动功能评分呈负相关(r=-0.577 9,-0.452 2,-0.662 8,P <0.05),一氧化氮水平与ASIA运动功能评分无明显相关性(r=-0.049 7,P> 0.05);(3)结果显示,急性脊髓损伤患者血清中超氧化物歧化酶、丙二醛、谷胱甘肽、神经胶质纤维酸性蛋白、神经元特异性烯醇化酶水平与ASIA残损分级及神经功能评分具有显著相关性,作为临床早期评估疾病严重程度的生物标志物具有一定潜力。

含双腐蚀缺陷高钢级油气管道剩余强度研究

为了加强含双腐蚀缺陷高钢级管道的安全评价,基于塑性失效准则,利用Workbench有限元分析软件对缺陷处的等效应力和剩余强度进行了模拟,考察了缺陷长度、缺陷深度和缺陷间距等参数对剩余强度的影响,利用99%相互作用准则确定极限作用距离,形成双腐蚀缺陷剩余强度评价方法,并进行数据验证。结果表明,随着内压的增加,管道先后经历弹性阶段、屈服阶段和强化阶段;在缺陷深度较深时,轴向间距对缺陷轴向分布时的最大等效应力影响较大,不同环向间距下的最大等效应力几乎不发生变化。当相邻腐蚀轴向间距系数n小于2.5、相邻腐蚀环向间距系数c小于1.26时,需考虑缺陷间的相互作用和影响;修正后公式可用于计算含双点腐蚀缺陷的高等级钢剩余强度,结果较DNV-RP-F101规范更接近有限元分析结果,最大相对误差不超过1.74%。研究结果可为提高管道完整性管理水平提供理论依据和实际参考。

重载铁路基床级配碎石动弹性模量及颗粒破碎试验研究

针对级配碎石的动力特性以及颗粒破碎性质,采用室内动三轴试验,研究其在循环荷载作用下循环应力比(cyclic stress ratio,CSR)、围压以及加载次数对累积动应变、动弹性模量、颗粒形状系数和颗粒破碎的影响。研究结果表明,不同CSR条件下,加载次数达到10000次时,累积动应变基本完成。随着加载次数的增加,不同CSR下的动弹性模量逐渐减小,滞回圈面积逐渐增加后保持稳定。低围压下,CSR对动弹性模量影响不显著,动弹性模量增加幅度较少;高围压下,动弹性模量随着CSR的增加而增长较大。循环荷载作用下,颗粒破碎方式主要为研磨;颗粒粒径越大,试验后的颗粒形状系数球度越大,颗粒越靠近球形,其轮廓线越圆滑。当CSR小于0.3时,影响颗粒破碎的主要因素为动应力大小,而围压影响不显著;当CSR大于0.3时,颗粒破碎主要因素受动应力和围压共同影响。

Grade 91耐热钢的硬度与持久强度、许用应力和运行/剩余寿命的相关性研究

利用不同硬度Grade 91钢试件的持久强度数据研究该钢硬度与持久强度和最大许用应力的相关性。结果表明,采用系列硬度试件所做确定温度和外力下的持久实验同时存在性能高估和低估现象,将这些数据综合在一起预测/外推钢的持久强度与实际值差距较大,利用由此确定的105 h持久强度计算得到的最大许用应力对应用产生不完全符合实际的影响。同时研究得到Grade 91钢在确定温度下满足最大许用应力的硬度下限的确定方法:对于硬度在201(205)HBW及其以上的Grade 91钢部件,在575(600)℃及其以下温度运行时可满足ASME BPVC 2019版规范对Type 1和Type 2型材料最大许用应力的要求;硬度在204HBW及其以上的Grade 91钢部件在575℃及其以下温度运行时可满足ASME BPVC 2017版规范对壁厚大于75 mm部件最大许用应力的要求。因此,在已有硬度范围规定(ASME BPVC 2017-2019对Grade 91钢:190~250HBW)的情况下,下调最大许用应力的ASME BPVC 2019新规范给现有硬度范围下限的实施带来一定困难,即满足该硬度下限要求却不能满足最大许用应力要求。为解决这一问题未来有必要上调硬度下限值。此外,研究了Grade 91钢运行/剩余寿命评估算法中利用短时实验数据外延105 h持久强度的函数优化。结果表明,现用算法采用幂函数拟合存在性能高估现象,若采用对数函数将不同硬度试件的持久数据分开拟合则可明显提高与实验数据的吻合性;在此基础上研究所得已知运行条件下部件厚度-硬度-运行/剩余寿命的关系将安全性评估的技术参数融为一体,可体现该方法的适用性、可靠性和直观性。以上研究结果可供相关标准修订和工业实际应用参考。