共查询到20条相似文献,搜索用时 46 毫秒
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对以针状铁素体为主的X80管线钢进行不同工艺的热处理,分别得到具有多边形铁素体组织或板条马氏体组织的试样。研究了显微组织对不同试样在饱和H_2S环境中的氢致裂纹(HIC)敏感性和氢渗透行为的影响。结果表明:具有不同显微组织的X80钢其HIC敏感性从大到小的排序为:1水淬处理的板条马氏体组织试样,2空冷处理的多边形铁素体组织试样,3原始针状铁素体组织试样;氢在材料中的捕获效率是影响材料HIC敏感性的主要因素之一,渗氢通量J_∞、氢扩散系数D_(eff)越低,氢捕获效率越高,管线钢的氢致裂纹敏感性越高。 相似文献
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本文运用电化学渗透技术研究了18Ni 马氏体时效钢的氢扩散和捕集现象。结果表明,时效试样内存在析出相颗粒,使表观氢扩散系数减小,其原因是析出相界面捕集氢,阻滞了氢输运过程的进行;并发现500℃时效3h 表观扩散系数最小,扩散激活能最大,因为该制度时样品内析出相颗粒的数量最多,分布最弥散,此时的析出相界面捕集能为10.0kJ/mol,陷阱密度(室温时)为3.4×10~(26)/m~3。最后就常规双电解池式的电化学渗透实验,分析和讨论了几个值得注意的问题。 相似文献
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本文运用电化学渗透技术研究了18Ni 马氏体时效钢的氢扩散和捕集现象。结果表明,时效试样内存在析出相颗粒,使表观氢扩散系数减小,其原因是析出相界面捕集氢,阻滞了氢输运过程的进行;并发现500℃时效3h 表观扩散系数最小,扩散激活能最大,因为该制度时样品内析出相颗粒的数量最多,分布最弥散,此时的析出相界面捕集能为10.0kJ/mol,陷阱密度(室温时)为3.4×10~(26)/m~3。最后就常规双电解池式的电化学渗透实验,分析和讨论了几个值得注意的问题。 相似文献
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利用氢渗透试验、慢应变速率拉伸试验(SSRT)研究了1 000MPa级高强钢(HSS)焊接件在海水中的氢渗透行为及其应力腐蚀敏感性,结合SEM观察了试样的断口特征,并利用电化学试验和显微组织观察分析了焊接件不同区域的氢脆特征。结果表明:相对于焊缝区(WM)和母材区(BM),热影响区(HAZ)的自腐蚀电位最负、析氢电位最正,更容易发生腐蚀和析氢行为。热影响区的氢扩散系数最大,具有较强的吸氢倾向。动态电化学充氢对高强钢焊接件的影响主要体现在对塑性的损减方面;随着极化电位的负移,高强钢焊接件的强度没有明显变化,但断面收缩率、断后延伸率均减小,断裂方式逐渐由韧性断裂变为解理断裂;当极化电位约为-930mV(vs SCE)时,高强钢焊接件的氢脆系数达25%;在不同充氢极化电位下,焊接件试样的断裂位置多在热影响区。 相似文献
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热镀锌钢材在海洋大气环境中的氢渗透行为 总被引:1,自引:0,他引:1
用改进的Devanathan双面电解池在恒温、恒湿)条件下检测热镀锌钢材的渗氢电流密度并观测其腐蚀形貌,研究了温度对其氢渗透行为的影响.结果表明,在湿度相同的条件下,随着模拟海洋大气环境温度的升高试样的氢渗透加速,且湿度越高温度的这种加速作用越显著;在高温和高湿条件下,试样的氢吸收和氢渗透进行得更快. 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献
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Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995. 相似文献