共查询到19条相似文献，搜索用时 218 毫秒
1.
《武汉工程职业技术学院学报》2019,(4)
测量结果的可信度及适用范围不仅取决于其数值大小,也和试验过程的不确定度密不可分。测量不确定度是对测量结果质量的定量表征,测量结果必须附有不确定度说明才是完整并有意义的。针对型钢产品进行了洛氏硬度试验中不确定度的评定。结果表明,考虑硬度计最大允许误差的方法1及考虑硬度计系统误差的方法2,其扩展不确定度分别为10.7%及8.7%,所以在较严苛的评定中应采用方法1。各影响因素之间比较而言,重复性误差是不确定度的主要贡献者,而压痕测量系统分辨力的影响很小,可忽略不计。 相似文献
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不确定度是从事计量检测的工作人员经常接触的,本文介绍紫外可见分光光度计紫外区透射比示值误差测量值的不确定度的评定分析。 相似文献
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通过对电能表计量标准测量不确定度分析,来理解计量标准测量不确定度评定方法与各项误差源的解析,并利用数理统计及试验方法对计量标准测量不确定度进行计算和评定。 相似文献
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影响纳米压痕试验结果的因素很多,导致分别计算A类和B类不确定度十分困难。该文采取实验室间比对的方法,通过对熔融石英样品进行纳米压痕试验,得出压痕硬度和压痕模量的重复性限r和复现性限R。在r和R的基础上推导出纳米压痕硬度和模量扩展不确定度的近似计算公式,从而大大简化了纳米压痕试验测量不确定度的评定。不确定度评定结果表明纳米压痕试验测量不确定度较大;试验次数超过5次后,其对扩展不确定度的影响不大。 相似文献
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金属材料低温冲击试验结果的影响因素很多,为了使冲击试验结果的测量不确定度评定具有可操作性和相当的可靠性,采用综合法对船用耐蚀钢-20℃冲击试验和桥梁用钢-40℃冲击试验进行不确定度评定,包含测量重复性、试验机误差、标准试样标准偏差、测量结果数值修约四个主要的不确定度分量。结果表明,其扩展不确定度分别为12.28%和22.16%,相对而言,其中测量重复性及试验机误差所占比重较大,而数值修约所引入的不确定度分量基本可忽略不计。 相似文献
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测量不确定度的分析及应用 总被引：4，自引：0，他引：4
简要介绍了误差理论的发展历程，阐述了测量不确定度与误差的区别与联系，分析了不确定度的A类评定与B类评定方法，并给出了工程测量中的实践应用模式。 相似文献
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以物距像距法测量薄凸透镜的焦距并讨论了焦距误差的计算方法,着重讨论了清晰像位置判断不确定所引入的测量误差,同时分析了改变物距对透镜焦距测量不确定度的影响. 相似文献
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目的:以最小二乘法直线度评定食品中砷测定过程中存在的不确定度,并找出影响不确定度的因素较大的环节。方法:根据GB/T 5009.11-2003《食品中总砷及无机砷的测定》的方法,应用最小二乘法拟合直线,进行不确定度评估,并计算出合成不确定度。结果:各分量中工作曲线变动性、移液管、样品定容过程及测量重复性引入的不确定度贡献较大,相对扩展不确定度为U=2.5%(k=2)。结论:以最小二乘法直线度评定食品中砷的不确定度,提高了评定的可信度,通过实验各环节的分析,要求操作过程必须细心、准确、规范,尽量减少不确定度。 相似文献
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误差理论简介与测量不确定度应用 总被引：1，自引：0，他引：1
有测量就有误差,就有不确定度。本文详细介绍了测量不确定度的分类和A类、B类、合成标准不确定度的定义以及在实际测量中的计算方法。 相似文献
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谢鹏 《广东轻工职业技术学院学报》2011,10(1):18-21,32
目的：对门冬酰胺酶效价测量的不确定度进行评定。方法：分析了门冬酰胺酶效价测量过程中几种因素对门冬酰胺酶效价测定不确定度的影响,其中包括：重复性测量,对照品和样品的稀释体积及使用仪器等测量因素并进行了评定,由此计算合成不确定度,最终给出测量在95%置信区间下的扩展不确定度。结果：本实验测量结果为（10495.29±165.82）IU/瓶（K=2）。结论：分析并量化了检测方法的不确定度,为优化实验方法提供科学依据。 相似文献
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金属材料拉伸缺口变形行为的研究 总被引：1，自引：0，他引：1
通过拉伸试验研究了在"缺口效应"影响下塑性金属材料试样不同截面处的塑性变形规律及其它常规力学性能指标,结果表明所试验金属材料缺口拉伸塑性变形主要集中发生在缺口附近局部区域,同时探讨了增加"缺口塑性"这一新的性能指标及建立相关试验标准的必要性。 相似文献
12.
XIE Hua 《实验室研究与探索》2007,(10)
由于影响金属材料断裂韧性的测量不确定度评定的因素比较多,不同人员认识到的影响因素也有差异,因此其评定还处于初级阶段。本文从试验方法上对金属材料断裂韧性KIC的测量不确定度进行了评定,从试验机等级、试样尺寸测量、试验人员、引伸计等方面对引起不确定性的因素进行了详细讨论和计算。评定过程没有考虑材料不均匀带来的影响。指出影响断裂韧性测量不确定度大小的最主要因素是力值和f(a/W)的测量误差,其中试验机的等级和人员技术水平又是主要因素。 相似文献
13.
Qiu Zhao Kongsheng Chen Meizhong Chen Bruno Briseghella Zhiyong Guo Guotao Yang 《天津大学学报(英文版)》2018,(5)
The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test. 相似文献
14.
曾其科 《河北能源职业技术学院学报》2021,21(1)
金属垫片被广泛地用于高温、高压、强腐蚀介质的法兰联接中,是压力容器和管道中常见的密封形式。本文建立了螺栓-法兰-垫片联接系统模型,分析了预紧状态和工作状态平面金属垫片的应力应变。结果显示,垫片高应力区域出现在外圆周部分,圆周外沿首先发生塑性变形;介质压力作用加剧了垫片塑形变形,对垫片轴向变形量影响较大。 相似文献
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A new type of green reactive powder concrete (GRPC) with compressive strength of 200 MPa is prepared by utilizing composite mineral admixtures, natural fine aggregates, and short and fine steel fibers. The quasi-static mechanical properties (mechanical strength, toughness, fracture energy and interfacial bonding strength) of GRPC specimens, cured in three different types of regimes, are investigated. The experimental results show that the mechanical properties of the C200 GRPC made with the powder binders that is composed of 40% of Portland cement, 25% of ultra fine slag, 25% of ultra fine fly ash and 10% of silica fume are better than the others'. The corresponding compressive strength, flexural strength and fracture energy are more than 200 MPa, and 30 000 J/ m2 respectively. The dynamic tensile behavior of the C200 GRPC is also investigated through the split Hopkinson pressure bar (SHPB) according to the spalling phenomenon. The dynamic testing results demonstrate that strain rate has an important effect on the dynamic tensile behavior of GRPC. With the increase of strain rate, its peak stress and relevant strain increase. The GRPC exhibits an excellent strain ratio stiffening effect under the dynamic tensile load with high strain ratio, resulting in a significant change of the fracture pattern. 相似文献
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Due to traffic and wave actions, cast steel joints are subjected to variable-amplitude fatigue loading, which may cause fatigue problems. The ratio of the minimum strain to the maximum strain(strain ratio)can be employed to analyze the influence of variable-amplitude fatigue both in the elastic and plastic ranges. To evaluate the effect of the strain ratio on G20Mn5QT cast steel, the fatigue tests of smooth specimens were carried out at the strain ratio of 0.1. The cyclic deformation and the relationships between the strain amplitude, the stress amplitude, the Smith, Watson and Topper(SWT)parameter and fatigue life were studied and compared with those at the strain ratio of -1. Compared with other methods, Basquin formula and Solonberg formula provide reliable and appropriate ranges of S-N curve and fatigue limit at different strain ratios respectively. The SWT parameter can be used to predict the fatigue life at other strain ratios accurately. 相似文献
18.
Rate-dependent constitutive model of poly（ethylene terephthalate） for dynamic analysis 总被引：1，自引：0，他引：1
Uniaxial tensile testing at strain rates ranging from 10-3 to 10-1 s-1 was carried out to study the rate-dependent me-chanical behavior for poly（ethylene terephthalate） （PET） used in the packaging industry. The experimental results show that a rate-dependent plastic behavior exists for PET material. The value of the yield strength was found to increase with the increasing strain rate. A new constitutive model based on the improved Cowper-Symonds rate-dependent constitutive model is proposed to describe the mechanical behavior of PET material in the strain rate ranging from 10-3 to 10-1 s-1, providing more accurate material data for the subsequent simulation analysis of drop test and dynamic buckling. The predictions obtained using the proposed model are compared with experimental results of the improved Cowper-Symonds model. The simulating results of the proposed model agree well with the experimental data. For a low strain rate, the predictions of this model are more precise than those obtained using the improved Cowper-Symonds model. This confirms that the new constitutive model is suitable for describing the me-chanical behavior of PET material at a low strain rate and modeling impact problem. 相似文献
19.
Theone dimensionalinfinitesimalstrainconsolida tiontheorydevelopedbyTerzaghiassumedthattheper meabilityandcompressibilityoftheclayremainedcon stantduringconsolidationunderaparticularincrementofload[1] .So ,inpractice ,thetheorywasonlyapproxi matelysatisfying .Variousresearcheshavesoughttoex tendtheclassicaltheorytotakeaccountofthevariationofpermeabilityandcompressibilityduringconsolidationinoneormoreways .Thecompressibilityandcoefficientofpermeabilitywereassumedtobefunctionsofthede greeofsatur… 相似文献