Solution of stress intensity factors of multiple cracks in plane elasticity with eigen COD formulation of boundary integral equation

The concept of eigen crack opening displacement （COD） can be defined as the COD of a crack in infinite plate under the tractions acting on the crack surface. By introducing this concept, the eigen COD formulation of boundary integral equation is proposed in this paper, together with the solution procedures for multiple crack problems in plane elasticity. With the proposed approach, the multiple crack problems can be solved with the conventional displacement discontinuity boundary integral equations in an iterative fashion with a small size of system matrix as that in the numerical Green’s function （NGF） approach but without the trouble to determine the complementary solutions since the standard boundary element discretization on the crack surface is no longer required with the proposed approach. Some numerical examples computing the stress intensity factors are presented and compared with those in literature to show the accuracy and the effectiveness of the proposed approach.

超声破解剩余污泥碳、磷生物可利用性分析

为实现剩余污泥资源化利用,该研究利用超声破解装置释放剩余污泥的碳、磷,优化超声破解参数,并对破碎前后成份进行分析。结果表明,在超声时间为22 min、超声功率为720 W条件下,污泥中碳、磷释放完全。三维荧光和磷形态分析显示,超声破解后上清液主要成份为有机碳和有机磷,底层为无机脱水固体。污泥微观形态分析显示,超声可以有效破碎生物污泥絮体结构,实现污泥絮体和无机固体颗粒分离。研究发现,通过超声破解能够实现污泥有机和无机成份分离,有助于实现污泥资源回收利用。

基于材料断裂韧度测试的COD换算方法研究

考虑到断裂韧度J积分塑性分量的塑性功由载荷与加载线位移关系得到,通过测试CT(compact tension)和SEB(single edge bending)试样的裂纹嘴张开位移实现J积分计算,提出适用于两种试样的裂纹嘴张开位移与加载线张开位移转换的换算公式,并采用45钢CT试样和30CrMo钢SEB试样对新公式进行有限元数值比对和试验比对。结果表明,新公式结果与规范演算结果之间的相对误差不超过0.4%,与有限元分析结果之间的相对误差不超过0.6%,与CT试样试验结果之间的相对误差小于4.5%,与SEB试样试验结果之间的相对误差小于6%。

COD阻力曲线的单试样三曲线分析法

在三曲线分析的基础上,提出了一种新的单试样测定 COD 阻力曲线的方法和步骤,编制了计算机应用程序。用三曲线法测定了 C—Mn 钢,Cr-Mo 钢和一种焊缝金属的 COD 阻力曲线,与标准的多试样法实验结果符合较好。该方法使用方便经济。有推广使用的价值。

净化污水COD分析和应对措施

针对近期催化裂化装置出现净化污水COD含量高的现状,分析了造成该问题的原因。结合装置烟气除尘脱硫单元设计数据和数据对比,指出了是原料含硫量及氧化罐溶液PH值等因素导致净化污水COD偏高。通过采取降低原料硫含量、调整氧化罐溶液停留时间和PH值范围的措施,可以有效将净化污水COD含量控制到较低水平,对实际生产中有较好的指导作用和参考价值。

Strip-coalesced interior zone model for two unequal collinear cracks weakening piezoelectric media

In this paper, a mathematical strip-saturation model is proposed for a poled transversely isotropic piezoelectric plate weakened by two impermeable unequal-collinear hairline straight cracks. Remotely applied in-plane unidirectional electromechanical loads open the cracks in mode-I such that the saturation zone developed at the interior tips of cracks gets coalesced. The developed saturation zones are arrested by distributing over their rims in-plane normal cohesive electrical displacement. The problem is solved using the Stroh formalism and the complex variable technique. The expressions are derived for the stress intensity factors （SIFs）, the lengths of the saturation zones developed, the crack opening displacement （COD）, and the energy release rate. An illustrative numerical case study is presented for the poled PZT-5H ceramic to investigate the effect of prescribed electromechanical loads on parameters affecting crack arrest. Also, the effect of different lengths of cracks on the SIFs and the local energy release rate （LERR） has been studied. The results obtained are graphically presented and analyzed.

催化裂化烟气脱硫脱硝装置废水COD超标原因分析及应对措施

针对中国石化海南炼油化工有限公司重油催化裂化烟气脱硫脱硝装置外排废水COD(化学需氧量)超标的问题,通过分析补充新鲜水COD、综合塔补水量、余热锅炉出口烟气中SO2浓度、燃料气中C5+组分浓度、余热锅炉操作条件、废水氧化时间等因素,并采用重整轻汽油加入浆液中试验考察其对亚硫酸盐和亚硫酸氢盐氧化反应的影响。通过综合判断,认为烟气中SO2浓度严重超设计值以及废水中C5+烃类对亚硫酸盐和亚硫酸氢盐氧化的抑制是导致废水COD高的原因。根据分析结果,采取降低加工原油中阿曼原油比例或调整渣油加氢装置反应深度,以降低催化裂化原料硫质量分数至0.4%以下,并控制燃料气中C5+组分体积分数不大于0.5%等措施,从而确保废水COD稳定达标排放。

屈服强度和裂纹深度对COD降低系数的影响

研究了屈服强度σ_y和裂纹相对深度a/W对COD降低系数m的影响.结果表明,m与σ_y之间呈双曲线关系;m与a/w之间呈抛物线关系.

Mechanical properties of AISI 1045 ceramic coated materials by nano indentation and crack opening displacement method

Abstract： An effective approach was conducted for estimating fracture toughness using the crack opening displacement （COD） method for plasma enhanced chemical vapor deposition （PECVD） coating materials. For this evaluation, an elastoplastic analysis was used to estimate critical COD values for single edge notched bending （SENB） specimens. The relationship between fracture toughness （Kic） and critical COD for SENB specimens was obtained. Microstructure of the interface between AleO3-TiO2 composite ceramic coatings and AISI 1045 steel substrates was studied by using scanning electron microscope （SEM）. Chemical compositions were clarified by energy-dispersive X-ray spectroscopy （EDS）. The results show that the interface between of Al203-TiO2 and substrate has mechanical combining. The nanohardness of the coatings can reach 1 200 GPa examined by nanoindentation. The Klc was calculated according to this relationship from critical COD. The bending process produces a significant relationship of COD independent of the axial force applied. Fractographic analysis was conducted to determine the crack length. From the physical analysis of nanoindentation curves, the elastic modulus of 1045/AI2O3-TiO2 is 180 GPa for the 50 μm film. The highest value of fracture toughness for 1045/A1203-TiO2-250 μm is 348 MPa·mv2.

PERIODICAL INTERFACIAL CRACKS IN ANISOTROPIC ELASTOPLASTIC MEDIA

By using Fourier transformation the boundary problem of periodical interfacial cracks in anisotropic elastoplastic bimaterial was transformed into a set of dual integral equations and then it was further reduced by means of definite integral transformation into a group of singular equations. Closed form of its solution was obtained and three corresponding problems of isotropic bimaterial, of a single anisotropic material and of a bimaterial of isotropy- anisotropy were treated as the specific cases. The plastic zone length of the crack tip and crack openning displacement ( COD) decline as the smaller yield limit of the two bonded materials rises, and they were also determined by crack length and the space between two neighboring cracks . In addition , COD also relates it with moduli of the materials .

Moving line crack accompanied with damage zone subject to remote tensile loading

In the 1920s, a closed-form solution of the moving Criffith crack was first obtained by Yoffe. Based on Yoffe＇s solution, the Dugdale model for the moving crack case gives a good result. However, the Dugddle model fails when the crack speed is closed to the Rayleigh wave speed because of the discontinuity occurred in the crack opening displacement （COD）. The problem is solved in this paper by introducing a restraining stress zone ahead of the crack tip and two velocity functions. The restraining stresses are linearly distributed and related to the velocity of the moving crack. An analytical solution of the problem is obtained by use of the superposition principle and a complex function method. The final result of the COD is continuous while the crack moves at a Rayleigh wave speed. The characteristics of the strain energy density （SED） and numerical results are discussed, and conclusions are given.

STUDY ON THE RELATIONSHIP BETWEEN J-INTEGRAL AND COD

J-integral arid crack opening displacement 8 （COD） were important parameters for characterization of fractures in engineering materials. The relationship between J-integral arid COD has been investigated for a long time and was generally represented as J = m σy, δ, where σy is the yield strength arid m is a function of specimen geometry arid material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis （ FRASTA ） for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD arid fracture surface average profile, the relationship between J-integral arid COD was deduced arid compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.

烟气脱硫装置外排污水COD超标的控制

烟气脱硫装置的废水具有高含盐、高COD的特点,受国家排放指标的要求,中国石油哈尔滨石化公司烟气脱硫装置外排污水COD超标。通过对该烟气脱硫装置外排污水COD高的原因进行分析,总结了操作方法和相关技术改造,提出并实施了控制和解决方案,成效显著。

裂缝及介质非均匀散射

为配合地球物理衍射CT的研究，本文对几何非均匀（尤指裂缝）引起的散射及介质非均匀（尤指弹性系数摄动）所产生的散射场，运用弹性动力学得到了解析式与数值结果。裂纹散射场可用裂纹张开位移COD与Green应力张量的褶积表示。其远场特性的研究在油气勘探中对预测裂隙位置、方向及大小均有重要意义。

锅炉汽包裂纹扩展分析与计算

针对锅炉汽包本身的缺陷和裂纹会在压力和温度载荷作用下扩展而导致汽包失效问题,依据《压力容器缺陷评定规范》,运用有限元方法计算出了某125 MW锅炉在启动、运行和停机3种工况下汽包危险区域的应力分布及随时间变化的规律,采用CTOD方法计算了该处临界裂纹尺寸与年裂纹扩展量.

开裂混凝土衬砌的渗透模型

混凝土的渗透性在控制混凝土的质量及混凝土结构的行为上起着关键性作用,裂缝的存在为水体及其他有损于混凝土结构耐久性的物质提供了入侵通道,这样,开裂混凝土的渗透性就直接影响混凝土的长期耐久性。文章从开裂混凝土衬砌的水体渗透特性出发,分析混凝土在裂缝开展过程中的渗透动态特征,在裂缝开度恒定时的稳定渗流特性。给出拉伸应力作用下混凝土的渗透模型,包括两部分,第一部分为裂缝开度与拉应力的关系模型,认为两者间存在着固定的线性关系;第二部分为裂缝开度与渗透性关系模型,认为在裂缝开度小于80μm时,其渗透规律与其他阶段有着显著的差别;从而推求混凝土拉应力与渗透性的直接关系。最后,通过成熟的试验数据对提出的开裂混凝土的渗透模型进行了实际验证,结果较为吻合。

混凝土重力坝抗震配筋加固措施的效果研究

混凝土坝遭遇强烈地震导致坝体严重受损已有先例。工程界建议布置坝面钢筋以提高坝体抗震性能。基于此,本文应用嵌入式滑移模型和钢筋刚化模型模拟混凝土重力坝配筋前后的地震动力响应,据此评价坝面配筋措施的抗震效果。计算结果显示,配筋前后结构整体响应基本一致,但布置坝面钢筋后坝体裂缝由集中裂缝分散为多条裂缝,裂缝张开位移和扩展深度较配筋前减小;此外,钢筋滑移对坝体裂缝分布形态也有一定影响。研究表明:配置坝面钢筋对限制与分散混凝土开裂将起到一定的作用,有助于提高混凝土坝抗震性能。

基于断裂力学的射孔套管孔边开裂行为分析

针对内压作用下的射孔套管的孔边开裂行为,应用断裂力学分别对线弹性条件和弹塑性条件下的孔边开裂进行分析,给出线弹性条件下圆柱壳体孔边裂纹应力强度因子和临界开裂内压公式,以及弹塑性条件下含孔边裂纹管道的临界开裂内压公式;通过MATLAB对两种条件下的力学模型进行解析,首先从线弹性条件下内压、裂纹长度以及孔径对应力强度因子的影响展开分析;然后从弹塑性条件下孔径和裂纹长度对临界开裂内压的影响进行分析;最后对小范围屈服情况下的两种断裂判据的套管临界开裂内压进行了对比。

两种粘弹塑性材料中Ⅲ型界面裂纹的断裂特性分析

将Dugdale Barenblatt模型推广应用于两种粘弹塑性材料之间裂纹问题的分析 ,对沿切向具有跳跃边界条件的边值问题的控制方程进行富里叶变换 ,然后用逐段定积分变换方法 ,将该边值问题转化为奇异积分方程组。解方程后计算了裂纹尖端塑性区尺寸及裂纹尖端张开位移COD ,给出了应变能释放率算式。结果表明 ,裂纹尖端塑性区尺寸和COD均决定于两种材料的最小屈服极限τs。

夹杂物体积分数和平均间距对高Co-Ni超高强度钢断裂韧度的影响

微孔聚集延性断裂模式的高Co-Ni超高强度钢的断裂韧度受显微组织和夹杂物特征控制。影响断裂韧度的夹杂物特征包括夹杂物性质、大小、体积分数、平均间距和夹杂物抗空穴形核能力。在固定显微组织和夹杂物抗空穴形核能力因素的基础上,分析夹杂物体积分数f、夹杂物平均间距X0对临界裂纹尖端张开位移δIc的影响,得出高Co-Ni超高强度钢临界裂纹尖端张开位移与夹杂物体积分数f-1/3和平均间距X0呈线性关系。结果表明,减小夹杂物体积分数、增大夹杂物平均间距有利于高Co-Ni超高强度钢断裂韧度的改善。