共查询到19条相似文献,搜索用时 250 毫秒
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为研究立井井壁破裂与内部应变之间的相互规律,搭建井壁实物模型以模拟井壁受力破裂过程和状态,利用分布式光纤技术对井壁内部应变进行监测,并分别从应力和应变多角度进行深入分析.结果表明:对于应变状态,当施加应力增大,井壁应变程度也随之增大,应变极大值所对应的井壁位置,其应变程度在范围内达到最大,破裂风险也就最高;对于应力作用,不同应力下井壁应变最大值与最小值之间的偏差度越大,井壁稳定性越差,越容易发生破裂;分析了应力、应变二者相互关联性,拟合各方向角所对应的井壁位置应变变化的线性方程,变化率数值越大,井壁应变增长速度就越快,当应变值超过所能承受极限时,井壁会更容易发生破裂;通过对井壁应变数据监测,分析了应变差值、偏差度和应变变化率,结合Lamé公式,建立了井壁应变破裂关系模型,为井壁破裂预警提供了新方案. 相似文献
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岩石流变力学的研究中,蠕变寿命是一个重要问题.由于长期蠕变试验资料的缺乏,难以估计蠕变破坏时间.该文进行了泥质盐岩单轴全应力 应变压缩试验,并采用陈氏加载法进行了单轴蠕变试验.对蠕变曲线进行了处理,获得了不同应力水平下的蠕变曲线簇,进而得到了等时应力-应变曲线簇.通过拟合分析,建立了等时应力-应变曲线割线模量随时间变化关系模型和等时应力 应变曲线的数学模型.对等时应力 应变曲线与全应力-应变曲线之间的关系进行了分析,获得了蠕变破坏强度和破坏应变分别与蠕变寿命之间的数学表达式.该文研究成果可以估计泥质盐岩的蠕变寿命、长期强度、长期模量、蠕变破坏线和蠕变终止线,对相关岩石流变寿命的估计具有借鉴意义. 相似文献
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本文对连续统力学的两个基本概念——应变率和应力率——进行了若干考虑,并提出一些结果.首先对应变和应力概念作了一个扼要的系统回顾.第二节用绝对符号法给出一个至今尚属未知的右伸长张量时间变化率的显表达式.尔后,本工作提议区分定义客观性应力率的两种途径.按照第二种途径分析了若干特例之后,作者提出一个称为广义Jaumann导数的作为客观性应力率.它包含了大部分现有的应力率定义,以及Hill的结果. 相似文献
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缝洞型碳酸盐岩在我国油气资源储量中占有重要地位,因此,研究缝洞型碳酸盐岩压裂井井底压力变化具有重要意义.基于渗流力学基本原理,建立考虑应力敏感和启动压力梯度影响的碳酸盐岩渗流微分方程,利用点源函数理论、Laplace积分变换和Fourier余弦积分变换等方法求得Laplace空间顶底封闭、侧向无限大外边界点源解,通过对点源积分得到面源解;通过Stehfest数值反演得到实空间井底压力解并绘制试井曲线.通过模型对比分析验证了模型的正确性.结果表明:应力敏感系数越大,压力和压力导数曲线上翘越明显;启动压力梯度越大,压力和压力导数曲线上翘时间越早;压裂井打开程度越小,压力导数球形流特征越明显;窜流系数越大,“凹子”出现的时间越早;弹性储容比越大,“凹子”越宽越深.利用该模型可以有效地对缝洞型低渗透碳酸盐岩油藏压裂井的动态曲线进行分析. 相似文献
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高体积百分比颗粒增强聚合物材料的有效粘弹性性质 总被引:1,自引:0,他引:1
聚合物材料通常表现为粘弹性性质.为了改进聚合物材料的力学性能,通常将某种无机材料以颗粒或纤维的形式填充到聚合物中,从而得到增强、增韧的聚合物基复合材料.提出了一个新的细观力学模型,用于预测颗粒增强聚合物复合材料的有效粘弹性性质,尤其针对高体积百分比的颗粒夹杂复合材料,该方法基于Laplace变换和双夹杂相互作用的弹性模型.计算了玻璃微珠/ED-6复合材料的有效松弛模量以及恒应变率下的应力应变关系.计算结果表明在高体积百分比下该文方法比基于Mori Tanaka方法预测的粘弹性效应明显减弱. 相似文献
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对GH4169高温合金开展了不同应力三轴度(-0.33~0.33)、不同应变率(0.001~5 000 s-1)、不同温度(293~1 073 K)条件下的材料性能试验.基于Johnson-Cook失效模型的框架,研究了Johnson-Cook(JC)失效模型及已有文献提出的修改形式中应力三轴度项拟合结果的不确定性及应变率对失效应变的线性关系描述局限性问题,通过提出的特定参数确定方法与耦合应力三轴度的应变率效应指数函数,建立了一种唯象修正的失效模型.基于GH4169高温合金的试验结果,标定了修正的失效模型与JC模型中各个参数.结果表明:在不同应力三轴度下,GH4169的失效应变表现出不同的应变率效应;与传统的JC模型相比,修正的失效模型更能够较好地描述GH4169的失效行为;同时能够保证失效应变的非负性. 相似文献
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The effect of strain rate on the mechanical properties and transition temperatures and the subregions of the glassy state that the latter define has been investigated for polystyrene and polymethyl methacrylate films containing various amounts of fiberglas. An inversion of the reinforcing effect of the filler is observed as the strain rate is varied at fixed temperature. Varying the temperature can also lead to an inversion of the nature of the strain-rate dependence of the strength of the reinforced polymer within the glassy state. In the low-temperature region the strength increases with decrease, and in the high-temperature region with increase in strain rate. The transition temperatures of the reinforced polymers are more sensitive than those of the unreinforced polymers to changes of strain rate. The subregions of the glassy state are almost independent of the strain rate, except that as the latter increases they are shifted into the high-temperature region.Mekhanika Polimerov, Vol. 4, No. 3, pp. 462–466, 1968 相似文献
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S. Sridhar N. Siva Prasad K. N. Seetharamu 《Finite Elements in Analysis and Design》1999,31(4):387-294
A finite element procedure for hyper-elastic materials such as rubber has been developed to estimate the temperature rise during cyclic loading. The irreversible mechanical work developed in rubber has been used to determine the heat generation rate for carrying out thermal analysis. The evaluation of the heat energy is dependent on the strains. The finite element analysis assumes Green–Lagrangian strain displacement relations, Mooney–Rivlin strain energy density function for constitutive relationship, incremental equilibrium equations, and Total Lagrangian approach and the stress and strain of the rubber-like materials are evaluated using a degenerated shell element with assumed strain field technique, considering both material and geometric non-linearities. A transient heat conduction analysis has been carried out to estimate the temperature rise for different time steps in rubber-like materials using Galerkin's formulations. A numerical example is presented and the computed temperature values for various load steps agree closely with the experimental results reported in the literature. 相似文献
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利用动态力学分析仪,详细研究了小应力作用下聚氯乙烯(PVC)接近玻璃化转变温度(63℃)时的短期蠕变性能.根据Struik-Kohlrausch (SK)方程及Struik移位方法,分析了物理老化对PVC瞬时蠕变柔量的影响,并提出了基于多松弛机制的新模型定量描述初始蠕变柔量、松弛时间和形状因子.结果表明:SK方程虽可表征不同老化时间下PVC的蠕变性能,但通过Struik移位方法却无法获得理想的主曲线,且初始蠕变柔量、松弛时间、形状因子和蠕变率均受物理老化显著影响,并在双对数坐标下随老化时间呈明显的非线性变化;新模型不仅揭示了物理老化控制参量的演化规律,而且极好地预测了PVC在物理老化进程中的高温蠕变行为. 相似文献
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Kao-Walter S. Dahlström J. Karlsson T. Magnusson A. 《Mechanics of Composite Materials》2004,40(1):29-36
The mechanical properties of a laminate consisting of aluminum-foil, adhesive, and polymer layers were studied in relation to the adhesion level. A special application for liquid-food packaging materials was considered. In experiments, laminates with and without adhesive layers were tested. Tensile tests were first run for every layer of the laminate, and the data obtained were then used in analyzing the results of tensile tests on the entire laminate, as well as in theoretical and finite-element calculations. Relations between different mechanical properties (such as Young's modulus, the peak stress, and the strain at the peak stress) and the adhesion level were analyzed. It was found that the tensile strength and the strain at the peak stress increased with adhesion level. Only slight differences in Young's modulus were observed at different adhesion levels. 相似文献
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M. N. Bokin E. V. Meshkov V. V. Poltavtsev Yu. S. Utkov V. N. Shalygin 《Mechanics of Composite Materials》1973,9(1):55-59
The state of stress and strain of polymeric coatings is determined in the case of a time varying temperature field that includes the range on which the coating goes over into the glassy state.Leningrad Mechanical Institute. Translated from Mekhanika Polimerov, No. 1, pp. 66–71, January–February, 1973. 相似文献
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Siqian Bao Gang Zhao Chibin Yu Qingming Chang Chuanlong Ye Xinping Mao 《Applied Mathematical Modelling》2011
Using a Thermecmastor-Z hot simulator, dynamic recrystallization (DRX) and static recrystallization (SRX) behavior of a Nb-microalloyed steel was investigated by single-hit compression tests and double-hit compression tests, respectively. The experimental results show that DRX will more easily occur at higher deformation temperature and lower strain rate. The deformation activation energy and stress exponent for the Nb-microalloyed steel are calculated to be 379.29 ± 23.56 kJ/mol and 5.76 in temperature range of 950 °C to 1100 °C by regression analysis, respectively. Furthermore, a semi-empirical model is developed to identify the peak stress and strain for DRX. It is found that SRX kinetics follows Avrami’s law, and the softening fraction predicted by the model agrees well with experimental results. 相似文献
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Wide application of polymer composite materials (PCM) in modern technology calls for detailed evaluation of their stress-strain properties in a broad temperature range. To obtain such information, we use the dynamic mechanical analysis and with the help of a reverse torsion pendulum measure the dynamic torsional rigidity of PCM bars of rectangular cross section in the temperature range up to 600 K. It is found that the temperature dependences of the dynamic rigidity of the calculated values of dynamic shear moduli are governed by the percentage and properties of the binder and fibers, the layout of fibers, the phase interaction along interfaces, etc. The principles of dynamic mechanical spectrometry are used to substantiate and analyze the parameters of anisotropy by which the behavior of a composite can be described in the temperature range including the transition of the binder from the glassy into a highly elastic state. For this purpose, the values of dynamic rigidity are measured under low-amplitude vibrations of the PCM specimens with a fiber orientation angle from 0 to 90°. It is shown that for unidirectional composites the dependence between the dynamic rigidity and the fiber orientation angle is of extreme character. The value and position of the peak depend on the type of the binder and fibers and change with temperature. It is found that the anisotropy degree of PCM is dictated by the molecular mobility and significantly changes in the temperature range of transition of the binder and reinforcement from the glassy into a highly elastic state (in the case of SVM fibers). The possibility of evaluating the anisotropy of composites with other reinforcement schemes, in particular, of orthogonally reinforced PCMs, is shown.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 291–308, May–June, 1999. 相似文献
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Saeed-Reza Sabbagh-Yazdi Tayebeh Amiri-SaadatAbadi 《Applied Mathematical Modelling》2013,37(1-2):82-101
Considering variation of the material properties during early ages of construction, the strain–stress fields due to cement hydration induced transient temperature field in a section of a concrete dam are computed. The 2D matrix free Galerkin Finite Volume (GFV) method is utilized to solve temperature and plane-strain equations in a sequential manner on an Unstructured Triangular Elements (UTE) meshes. For the computed temperature field at each time step some iterative solutions are performed until the force equilibrium equations are converged. In the developed numerical model, a novel method to impose gradient boundary condition is introduced that is suitable for the GFV solution on UTE meshes. The results of the developed model is verified by comparing the computed results with the experimental measurements of some bench mark test cases, and good agreement is observed. To present the ability of the introduced model to model real problems, modeling time dependent thermal stress profiles during gradual construction of a concrete dam on a natural foundation is performed for both constant and variable mechanical properties conditions. 相似文献