仪器化压痕法单次加载数据绘制应力-应变曲线计算拉伸试验结果的方法初探

采用压痕仪自动采集的位移数据减去压痕仪的弹性变形量得到压痕深度,进而计算出压痕直径,再根据TABOR提出的关于压痕方法测试拉伸性能的系列关系式,计算出真应力、工程应力和应变,绘制出压痕法的连续应力-应变曲线和lg W-lg d曲线,根据两种曲线计算出抗拉强度、屈服强度和应变硬化指数(n值)。实测数据显示压痕法的连续应力-应变曲线与拉伸法的应力-应变曲线存在显著差异。对压痕法测得的抗拉强度、屈服强度和n值的测量不确定度进行了详细分析,结果表明:抗拉强度的测量不确定度小于抗拉强度值的10%,而n值的相对测量不确定度显著大于抗拉强度的相对测量不确定度,目前尚未找到可靠评估屈服强度测量不确定度的方法。     

布氏硬度不确定度评定

引言国际标准化组织 (ＩＳＯ)于 1 993年正式发布的“测量不确定度表示指南” ,已成为测量不确定度方面的权威性文件。测量数据是计量技术机构和产品质量检验机构以及各类检测机构的主要依据 ,没有给出不确定度的测量数据是没有意义的也是无法使用的。本文尝试用现代不确定度评定方法对布氏硬度不确定度进行评定 ,不妥之处请指正。1　布氏硬度的基本概念布氏硬度是指用一定直径的淬火钢球 (硬质合金球 ) ,以规定的负荷压入试样表面 ,保持至规定时间后卸除负荷 ,测量试样压痕的表面积 ,计算出布氏硬度值 ,该值是以试样压痕表面积的试验力表示…     

高精度布氏硬度压痕测量系统

通过对布氏硬度测量不确定度分析,得知在其各分量中以压痕测量系统的不确定度为最大.根据布氏硬度计量基准装置的基本要求,研制了新的高精度布氏硬度压痕测量系统,提高了原有系统的精度和稳定性.     

卷烟条包装盒压痕挺度测量不确定度的评定

目的以卷烟条包装盒为研究对象,依据YC/T 330测定卷烟条包装盒的纵、横向压痕挺度,分析由折痕挺度仪、试样裁切尺寸偏差及测量重复性所引入的测量不确定度值,从而得到卷烟条包装盒压痕挺度的测量不确定度。方法通过对压痕挺度进行10次独立重复性试验,由计算标准偏差得出标准不确定度值,也称A类不确定度;然后再按B类不确定度评价方法对测量仪器及取样尺寸偏差带来的不确定度进行计算,得出B类不确定度;计算合成不确定度;最后计算扩展不确定度。结果依据YC/T 330测定卷烟条包装盒A的扩展不确定度U_纵=(83.1±6.22)g,k=2;U_横=(59.7±4.20)g,k=2。结论通过评定结果可知,对不确定度影响分量由大到小依次为试样裁切尺寸偏差、测量重复性、折痕挺度仪校准参数。     

电缆压痕激光测量系统设计与不确定度分析

针对人工测量电缆压痕效率慢以及受人为切片水平影响较大的问题,设计了一套自动测量装置。该装置通过软件对运动控制板卡发送指令,从而驱动电机实现对装有电缆夹具的二维移动平台的移动控制;同时激光传感器进行数据采集,得到数据集;对数据集进行滑动平均滤波处理,采用差分方法判断压痕;对非压痕数据进行线性回归处理,与压痕段数据相减,获得压痕深度。分析了测量计算过程中引入的不确定度来源,对一段电缆试样的测量结果进行不确定度评定,取包含因子k=2,扩展不确定度U=0.028mm。     

5252H32铝合金维氏硬度试验的测量不确定度评定

依据GB/T 4340.1-2009对5252H32铝合金进行了维氏硬度试验,并对试验结果进行了测量不确定度评定。结果表明:5252H32铝合金维氏硬度试验的测量不确定度主要来源于压痕对角线的不确定度、载荷的不确定度及数值修约引入的不确定度;控制影响不确定度的主要因素,可以减小测量不确定度,保证试验结果的准确性。     

金属布氏硬度试验的测量不确定度评定

金属布氏硬度试验是用较大直径球体压出较大的压痕 ,用压痕表面面积与试验力之比计算出硬度值。该方法测出的硬度值比较稳定、精度高、操作简单。试件的制备较其他力学试样和硬度试样容易。试验误差来源于试验力、压头、压痕测量装置、试样、试验力保持时间等 ,评定测量不确定度以知晓试验结果的可信度。1　试验方法1 1　原理将一定直径球体压入试样表面 ,保持一定时间后卸除试验力 ,用压痕表面面积与试验力之比计算出硬度值 ,即 :ＨＢ =ＦＳ =ＦπＤｈ=2ＦπＤ(Ｄ -Ｄ2 -ｄ2 )式中　Ｆ为试验力 ,Ｎ ;Ｓ为压痕表面积 ,ｍｍ2 ;Ｄ为球体压头…     

压痕应变法测量残余应力的不确定度分析

压痕应变法是近期出现的一种非常有价值的(焊接)残余应力测量技术,它具有无损、快捷、精确、成本低等特点。采用该技术测量残余应力时的误差大小或不确定度分析是人们关注的问题之一。应用B类评定法对采用该技术测量Q345低合金钢中焊接残余应力的不确定度进行了详尽分析,结果表明,应力相对不确定度的大小主要决定于应变的绝对值,低应变情况下的相对不确定度主要由重复性试验的应变不确定度决定。一般情况下,应力的标准不确定度数值为20～30MPa。     

温度条件在光面环规直径测量中的影响

通过对环规直径测量不确定度的评定,计算由于温度条件引起的不确定度分量,探讨改进温度条件的途径,分析提高环规直径测量准确度的方法。     

压痕测试法的新发展

介绍了压痕测试法的最新发展,指出了确定超薄薄膜t<10 nm及很硬的薄膜t<100 nm的硬度及模量是对计量学中纳米范围的挑战.以压痕测试法替代显微维氏实验可显著地降低测量不确定度及实现自动化.压痕测试法在纳米范围及显微范围内可为微电子学、微电机械系统、技术光学等领域采用.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

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.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

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.     

Estimation of potentialities of methods of summation of direct measurement errors

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.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

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.     

水三相点复现的不确定度评定

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)。