共查询到19条相似文献,搜索用时 140 毫秒
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采用布氏硬度计和电火花烧蚀方法在S38C车轴钢疲劳试样上引入压痕和电火花凹坑两类人工缺陷,研究含不同尺寸人工缺陷试样的疲劳极限,并与Murakami模型的计算结果进行对比。结果表明:疲劳裂纹从人工缺陷底部萌生;在研究范围内,含人工压痕和电火花凹坑试样的疲劳极限均随着缺陷投影面积的增加而呈线性降低趋势;在缺陷于横截面上投影面积相同条件下,试验得到含电火花凹坑试样的疲劳极限比含人工压痕试样的低30 MPa左右,含人工压痕试样的疲劳极限试验值比计算值高约50MPa,而含电火花凹坑试样的疲劳极限仅比计算值高约20MPa,含该类缺陷试样的疲劳极限可由Murakami方程进行近似预测。 相似文献
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对光热技术测量材料缺陷的原理及实验方法进行了研究。通过对试样光热信号的振幅和相位的测量,确定出材料缺陷的位置,并由理论公式通过计算机拟合出缺陷大小的尺度。设计了硬件与软件,实现了测量自动化,并对C/Al复合材料的表面缺陷进行了测量。 相似文献
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为给选择公式或拓展公式应用范围提供依据,应用概率论知识和数理统计理论,建立了公式稳定性与精度的比较与评价方法.基于承压圆筒实际爆破压力与有关公式计算值之比是基本符合正态分布随机变量的研究,从分布参数波动范围的变化系数比较与评价公式稳定性,从分布参数取值区间的重合度比较与评价公式精度.在双侧置信度98%时和公式的应用范围内,比较与评价了中径公式、特雷斯卡公式、福贝尔公式与流变应力公式的稳定性和精度.研究表明:(1)稳定性与精度不降低是选择公式或拓展公式应用范围的基本条件;(2)对于单层承压圆筒,中径公式的实测爆破压力应用范围,可由标准规定的不超过105 MPa拓展到不超过329.6 MPa,公式的稳定性明显提高且精度不降低;特雷斯卡公式的实测爆破压力应用范围,可由标准规定的位于91.0 MPa~300 MPa之间拓展到不超过329.6 MPa,公式的稳定性明显提高且精度不降低;在实测爆破压力不超过329.6 MPa时,中径公式与特雷斯卡公式的稳定性与精度无显著差异;在流变应力公式的应用范围为实测爆破压力不低于220 MPa,以及福贝尔公式的应用范围为实测爆破压力不低于250 MPa时,两个公式的精度没有明显差异,流变应力公式的稳定性明显比福贝尔公式好;当中径公式或特雷斯卡公式应用范围为实测爆破压力不超过329.6 MPa,以及流变应力公式的应用范围为实测爆破压力不低于220 MPa时,中径公式或特雷斯卡公式的稳定性明显比流变应力公式的好,精度也高于流变应力公式.(3)对于实测爆破压力不超过209.7 MPa的扁平绕带式压力容器,中径公式的精度和稳定性比单层承压圆筒爆破压力的4个预测公式低. 相似文献
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车轴遭受异物冲击缺陷存在多种形式,其中棱角冲击对车轴疲劳性能影响较大,会加速车轴的失效。为研究棱角冲击缺陷对车轴疲劳极限的影响,针对30Ni Cr Mo V12车轴钢,采用软件模拟与疲劳试验相结合的方法,借助ABAQUS对冲击缺陷区域进行应力场分析,对预制好的缺陷车轴试样进行疲劳试验,依据试验结果采用近似欧文单侧公差极限法拟合各试样组疲劳P-S-N曲线,得到相应的疲劳极限。根据各试样组的疲劳试验结果预测全尺寸车轴疲劳极限。考虑冲击缺陷深度的分散性,对缺陷深度和全尺寸车轴疲劳极限两参数进行拟合。最后基于EI-HADDAD公式,建立含棱角冲击缺陷的30Ni Cr Mo V12车轴钢的多变量疲劳极限预测模型。采用该模型能够快速预估含不同尺寸棱角缺陷的全尺寸车轴疲劳极限。 相似文献
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Chan Hee Cho Hee Jong Lee Min Woo Nam Hyun Ju Yoo Sung-Yull Hong 《Journal of Mechanical Science and Technology》2013,27(3):679-683
The reliability and performance of steam generators (SGs) are serious concerns in the operation of nuclear power plants. In particular, SG tubing is subject to a variety of degradation processes that can lead to potential leakage or rupture. To prevent a plant shutdown from this kind of event, the integrity of SG tubing should be periodically determined. The eddy current test is widely used for the inspection of SG tubing during in-service inspection. For the evaluation of eddy current data, analysts are required to have the Level II or greater qualification based on the american society for nondestructive testing (ASNT) standard. In addition, analysts evaluating eddy current data obtained from SG tubing are required to have a qualification of performance demonstration. The performance demonstration program in Korea has existed since 2004 and uses the qualified data analyst (QDA) program developed by the electric power research institute (EPRI). Recently, the QDA program was updated by EPRI. The updated QDA program has been in effect for SG tubing analysts in Korea since 2010. In this paper, we describe the performance demonstration program, the degradation mechanisms, and the inspection techniques for SG tubing in nuclear power plants. 相似文献
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蒸汽发生器检测技术的发展 总被引:1,自引:0,他引:1
以前的蒸汽发生器检测系统通常由多个独立的模块组成,相互间的控制与通讯连接往往需要大量的电缆与适配器。采用的检查方法是单频涡流仪与BOBB IN探头,这对体积性缺陷有很高的检测率。但是传热管上不断发现的其他形式的缺陷对其完整性造成了很大影响,甚至可能影响到电站的可靠性、功率以及经济效益。在越来越严厉的电站规范要求和确保公众与环境的安全的前提下,旧系统的检测能力难以满足规范要求。为了能够快速检出这些多样化缺陷,对其进行定量、定性解释,并满足辐射防护原则的要求,由先进探头技术和基于高速计算机与远程通信系统平台的多用途仪器构成的检测系统在近10年得到了很大的发展。整个检测系统的智能化与集成度越来越高,使蒸汽发生器检测质量更高,速度更快,经济效益也更高。 相似文献
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连铸球墨铸铁扭转缺口强度的研究 总被引:1,自引:0,他引:1
研究了一种用水平连铸技术生产的球墨铸铁型材的扭转强度和缺口扭转强度。实验发现光滑扭转试样是沿45°方向开裂,开裂面是最大拉应力面,表现为典型的脆性断裂。缺口试样的断裂模式分两种情况:当为钝缺口时(即(ρ≥0.75mm,Kt≤1.6),其断裂特征与光滑试件相同;而当为尖锐缺口时(即ρ<0.375mm,Kt>2.1)的开裂出现在缺口根部,并且开裂面垂直于轴线方向,是剪应力作用。实验结果还表现出扭转缺口强度与应力集中系数的关系,即应力集中系数越大,扭转缺口强度反而越高。该球墨铸铁的缺口敏感性(NSR)大于1,故缺口完全不敏感。 相似文献
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Lizhong Wang 《International Journal of Mechanical Sciences》2011,53(5):348-354
Based on a unified yield criterion (UYC), the plastic collapse analysis of thin-walled pipes is conducted in the framework of finite strain. A unified analytical solution for the burst pressure of end-capped defect-free pipes is derived, which is fit for various kinds of non-SD (strength differential) materials. A series of solutions can be deduced from this unified solution, and those solutions of burst pressure on the basis of Tresca, von Mises, ASSY, and TS criteria are special cases of it. By comparing with existing test result, it is found that the present unified solution is very convenient and effective for the prediction of burst pressure. 相似文献
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W. J. TRIFFO H. PALSDOTTIR K. L. McDONALD J. K. LEE J. L. INMAN M. J. BISSELL R. M. RAPHAEL & M. AUER 《Journal of microscopy》2008,230(2):278-287
High‐pressure freezing is the preferred method to prepare thick biological specimens for ultrastructural studies. However, the advantages obtained by this method often prove unattainable for samples that are difficult to handle during the freezing and substitution protocols. Delicate and sparse samples are difficult to manipulate and maintain intact throughout the sequence of freezing, infiltration, embedding and final orientation for sectioning and subsequent transmission electron microscopy. An established approach to surmount these difficulties is the use of cellulose microdialysis tubing to transport the sample. With an inner diameter of 200 μm, the tubing protects small and fragile samples within the thickness constraints of high‐pressure freezing, and the tube ends can be sealed to avoid loss of sample. Importantly, the transparency of the tubing allows optical study of the specimen at different steps in the process. Here, we describe the use of a micromanipulator and microinjection apparatus to handle and position delicate specimens within the tubing. We report two biologically significant examples that benefit from this approach, 3D cultures of mammary epithelial cells and cochlear outer hair cells. We illustrate the potential for correlative light and electron microscopy as well as electron tomography. 相似文献
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J. R. Casley-Smith 《Journal of microscopy》1972,96(3):363-365
Methods are described for the estimation of the dry specific gravities (SG) of specimens in thin sections, especially for the comparison of one group with another and for the quantification of electron stains. Variations in section thickness are overcome by using the naked supporting film as a base-line, and relating the SG of the specimen to that of the resin, which acts as a standard. Section thicknesses may also be estimated by using similar methods. The optical densities of their images are compared with those of standards; knowledge of the SG of the resin allows one to calculate its thickness. 相似文献
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水平井中钻柱屈曲的非线性有限元分析 总被引:1,自引:0,他引:1
建立了直井中钻柱屈曲的平衡方程及对应的泛函表达式,使用有限元法对不同约束下水平井中钻柱从稳定到非线性屈曲的整个过程进行了分析。力学模型中考虑了重力和扭矩对屈曲的影响。分析结果表明:钻柱的屈曲是一个从局部屈曲到总体屈曲的过程,屈曲段的井壁约束力、钻柱弯矩和屈曲位移呈周期性变化;重力在水平井中对屈曲有较强的抑制作用;边界约束对屈曲的影响不可忽略;扭矩对屈曲的影响很小,可以忽略。 相似文献
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采用新型奥迪轿车(AUDI1002.6E)在湖北襄樊东风汽车集团专用试车场高速环形道上,以满负荷、高油温和高速度的条件下,对15W/40SG级汽油机油进行了使用性能的试验,以考察油品在行车试验过程中的衰变规律以及对车辆有关部件的影响。试验结果表明,该15W/40SG级汽油机油具有优良的高温使用性能(抗氧化、清净分散性和抗磨性)。 相似文献