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工业管道应力腐蚀裂纹的检验 总被引:1,自引:0,他引:1
概述了金属材料应力腐蚀裂纹的特点,提出了工业管道对其检验的内容和方法,通过对应力腐蚀裂纹宏观和微观特征的检查和分析,基本可以区别应力腐蚀裂纹和其他裂纹.应力腐蚀裂纹是比较危险的缺陷,因此在管道检修和设计时应采取必要的改进措施,防惠于未然. 相似文献
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将数字图像相关方法用于测量含I型双边裂纹复合材料薄板应力强度因子。首先,介绍了数字图像相关方法基本原理,通过最小二乘拟合法建立了裂纹尖端位移场与裂尖应力强度因子的关系。其次,搭建了数字图像相关方法非接触光学测试平台,通过对含I型双边裂纹复合材料薄板进行拉伸试验,得到了复合材料薄板双边裂纹尖端全场位移。最后,通过数字图像相关方法计算所得全场位移,提取了裂纹尖端应力强度因子,分析了最小二乘拟合项数、数字图像相关计算中子区域和步长大小的选择对裂纹尖端应力强度因子计算的影响。 相似文献
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油气管道输送介质具有易燃、易爆特性,所面临的危害因素多,运营风险高,特别是管道出现裂纹的危害较大,在疲劳、应力腐蚀的作用下易导致管道破裂失效。本文针对某长输管道内检测中发现的裂纹,基于静裂纹的模拟方法在对含裂纹缺陷管道进行有限元模拟计算方面,具有更高的计算精度和效率,建立了静裂纹管道的有限元模型,采用运动式耦合方法与管道端面进行耦合,获得裂纹尖端张开位移(Crack Tip Opening Displacement,CTOD)随应变的变化关系,并使用FAD图(Failure Assessment Diagram)评估方法进行工程失效评估,最终有效评估管道的安全性,该方法的联合使用,对于含裂纹管道的安全性精准评估具有重要意义。 相似文献
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采用实验方法研究聚乙烯(PE)管道焊接接头在机械载荷条件下的应力松弛行为,通过松弛试验得出用Prony级数表示的PE管道焊接接头的本构模型。结果表明,PE管道焊接接头的松弛曲线与PE管道木材的松弛曲线相似;结合有限元分析软件Abaqus,建立PE80焊接接头的裂纹缺陷模型,导入PE管道焊接接头与PE管道母材的Prony级数,对含裂纹缺陷PE管道的应力强度因子进行计算;借鉴GB/T 19624—2004金属管道的评定标准,给出适合PE材料的断裂判据,比较PE材料的临界应力强度因子(KIC)及计算得出的应力强度因子(KI)的大小,进而通过断裂判据对含缺陷PE管道进行安全评价。 相似文献
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利用有限元法对含外表面轴向裂纹的直管进行了分析,应用有限元软件ANSYS建立了裂纹有限元模型,采用参数化建模对内压下裂纹的应力强度因子KI进行计算,得出了影响应力强度因子的主要因素。计算表明,应力强度因子随a/t及a/c成线性变化,并与t/Do为乘幂关系。一般情况下,表面裂纹在最深点(90°)处应力强度因子最大,然后随着角度的减小应力强度因子依次减小。但是在最浅点(0°)处应力强度因子有回升趋势,且随着a/t的增加,这种回升趋势逐渐明显,当a/t=0.8时,甚至出现最浅点KI超过最深点KI的现象,这时对于结构的脆性起裂位置要慎重判断,不能单纯地以最深点KI为断裂依据。 相似文献
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根据地应力测试的基本概念及原理,结合实际地应力测试工作,介绍了地应力测试过程中的测量原理、测试设备与现场测量方法,并对测试结果进行了分析。在此基础上,根据地应力的测试结果,运用多元线性回归的方法进行了地应力场反演,并以西二采区9号煤反演结果为例进行了分析,结果表明,该采区3个工作面位于应力集中区,冲击危险性较大。 相似文献
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Kazunori Kageyama Yasumasa Iwasaki Makoto Daimon 《International journal of molecular sciences》2021,22(22)
This review addresses the molecular mechanisms of corticotropin-releasing factor (CRF) regulation in the hypothalamus under stress and stress resilience. CRF in the hypothalamus plays a central role in regulating the stress response. CRF stimulates adrenocorticotropic hormone (ACTH) release from the anterior pituitary. ACTH stimulates glucocorticoid secretion from the adrenal glands. Glucocorticoids are essential for stress coping, stress resilience, and homeostasis. The activated hypothalamic-pituitary-adrenal axis is suppressed by the negative feedback from glucocorticoids. Glucocorticoid-dependent repression of cAMP-stimulated Crf promoter activity is mediated by both the negative glucocorticoid response element and the serum response element. Conversely, the inducible cAMP-early repressor can suppress the stress response via inhibition of the cAMP-dependent Crf gene, as can the suppressor of cytokine signaling-3 in the hypothalamus. CRF receptor type 1 is mainly involved in a stress response, depression, anorexia, and seizure, while CRF receptor type 2 mediates “stress coping” mechanisms such as anxiolysis in the brain. Differential effects of FK506-binding immunophilins, FKBP4 and FKBP5, contribute to the efficiency of glucocorticoids under stress resilience. Together, a variety of factors contribute to stress resilience. All these factors would have the differential roles under stress resilience. 相似文献
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Lavinia Mareri Luigi Parrotta Giampiero Cai 《International journal of molecular sciences》2022,23(10)
Land plants are constantly subjected to multiple unfavorable or even adverse environmental conditions. Among them, abiotic stresses (such as salt, drought, heat, cold, heavy metals, ozone, UV radiation, and nutrient deficiencies) have detrimental effects on plant growth and productivity and are increasingly important considering the direct or indirect effects of climate change. Plants respond in many ways to abiotic stresses, from gene expression to physiology, from plant architecture to primary, and secondary metabolism. These complex changes allow plants to tolerate and/or adapt to adverse conditions. The complexity of plant response can be further influenced by the duration and intensity of stress, the plant genotype, the combination of different stresses, the exposed tissue and cell type, and the developmental stage at which plants perceive the stress. It is therefore important to understand more about how plants perceive stress conditions and how they respond and adapt (both in natural and anthropogenic environments). These concepts were the basis of the Special Issue that International Journal of Molecular Sciences expressly addressed to the relationship between environmental stresses and plants and that resulted in the publication of 5 reviews and 38 original research articles. The large participation of several authors and the good number of contributions testifies to the considerable interest that the topic currently receives in the plant science community, especially in the light of the foreseeable climate changes. Here, we briefly summarize the contributions included in the Special Issue, both original articles categorized by stress type and reviews that discuss more comprehensive responses to various stresses. 相似文献
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本文对某换热器的前管板在机械载荷和热载荷下利用有限元分析软件ANSYS进行强度分析。在分析时,首先进行热分析得出温度分布,得出温度最大值出现在换热管与管板接触区,且最大值为150.408℃。然后在热分析的基础上进行应力分析,得出最大应力出现在螺栓连接处,且为174 MPa。最后参照JB4732-1995《钢制压力容器分析设计标准》采用线分析法选取7处危险区域进行应力评定,得出3处应力(为机械载荷和热载荷的总应力)最大为174 MPa小于安全值438 MPa。所以该换热器在运行过程中是安全的。 相似文献
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The criterion for the stability of a large pore in a fine pore matrix is reconsidered, taking into account the pressure exerted by the densifying matrix. The result indicates that progressively larger pores can shrink, even if grain growth is minimal or absent. 相似文献
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Jie Li Wuliji O Wei Li Zhi-Gang Jiang Hossein A. Ghanbari 《International journal of molecular sciences》2013,14(12):24438-24475
Living cells continually generate reactive oxygen species (ROS) through the respiratory chain during energetic metabolism. ROS at low or moderate concentration can play important physiological roles. However, an excessive amount of ROS under oxidative stress would be extremely deleterious. The central nervous system (CNS) is particularly vulnerable to oxidative stress due to its high oxygen consumption, weakly antioxidative systems and the terminal-differentiation characteristic of neurons. Thus, oxidative stress elicits various neurodegenerative diseases. In addition, chemotherapy could result in severe side effects on the CNS and peripheral nervous system (PNS) of cancer patients, and a growing body of evidence demonstrates the involvement of ROS in drug-induced neurotoxicities as well. Therefore, development of antioxidants as neuroprotective drugs is a potentially beneficial strategy for clinical therapy. In this review, we summarize the source, balance maintenance and physiologic functions of ROS, oxidative stress and its toxic mechanisms underlying a number of neurodegenerative diseases, and the possible involvement of ROS in chemotherapy-induced toxicity to the CNS and PNS. We ultimately assess the value for antioxidants as neuroprotective drugs and provide our comments on the unmet needs. 相似文献
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玻璃的退火是浮法平板玻璃生产过程的一个重要环节。文章阐述了玻璃热应力产生和消除方法,指出在线应力检测是控制退火质量的较好途径。 相似文献
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The contribution of entanglements to the modulus of a time independent polymer is satisfactorily accounted for by the C2/λ term in the Mooney-Rivlin equation. On the other hand, the role of entanglements in time dependent polymers is less evident and seems to give rise to a non-linear Mooney plot. A model is introduced which considers an entanglement as a topological knot that tightens with initial deformation and subsequently inhibits chain slippage. The observed maximum in a Mooney plot at small values of λ is predicted, and the experimental data of plasticised PVC polybutadiene and styrenebutadiene copolymer are fitted reasonably well. 相似文献