Papers by Keyword: Measurement Uncertainty

Abstract: Two common types of internal defects of additively manufactured (AM) samples are lack-of-fusion and gas-entrapped porosities. These internal defects can have different physical origins and particular local characteristics (e.g., different shape, size). Thus, the use of reliable non-destructive inspection techniques is essential for the accurate assessment of integrity, allowing the applicable AM processing parameters correction. To overcome this challenge, this work aims to evaluate the accuracy of volumetric characteristics measured by computed tomography for porosity evaluations in AM samples, including assessment of measurement uncertainty. The effect of different cumulative thickness on the evaluated measurements accuracy is also assessed. The results show that deviations of defect size measurements can be below 2% if the proposed procedure is followed. In addition, the expanded uncertainty can be up to 10% of the measured magnitude when the cumulative thickness is increased to 70 mm. The physical relationships obtained between the cumulative thickness and the individual measurements are also presented.

Abstract: Measuring dimensional parameters (such as diameter, distance) by industrial computed tomography (CT) becomes more and more popular because of its advantages such as non-destructive method and short measurement time. However, the goodness of the measured values needs to be evaluated as a requirement of quality control. An aluminium test piece are designed and manufactured for mapping the measurement errors and uncertainties in case of dimensional CT measurements. In this article, the measurement errors are investigated based on the results of an experimental design, response surface method (RSM). Three main factors are varied systematically: the magnification of the CT, the numbers of views (NoV), and the set-up of the scanning mode. In the course of measurement evaluation several GD&T parameters are determined such as diameter of holes, distances between the holes, flatness and perpendicularity. The purpose of this research is to calculate the measurement errors and to determine the factors which have an effect on the dimensional CT measurement process.

Abstract: Information on the influence of the state of the production process of production and the uncertainty of the measurement on the decision on the product's suitability is given. It is shown on the example of brick production that the decision to accept a batch of bricks, taking into account the measurement uncertainty under unstable condition of the production process, may be erroneous. Three variants of the state of the production process for the production of 100-grade brick are considered. The first option - the average value of compressive strength does not coincide with the middle of the tolerance field, the production process is characterized as unstable, the second option - the average value of compressive strength does not coincide with the middle of the tolerance field, a greater value of the spread of the indicators compared with the first version and is characterized as an unstable process, the third option is the average value of the tensile strength, and compression coincides with the middle of the tolerance field, is characterized as a stable and reproducible process. It is established, that, if the production process is in a state of statistical controllability, i.e. stable, then taking into account the uncertainty of measurement, the brick grade remains 100. In an unstable process with an increase in the value of the standard uncertainty of type A, the controller's decision to identify the brand of brick 100 may be erroneous. Statistically stable and reproducible process makes it possible to increase the reliability of product quality control and to avoid mistakes in deciding on the rejection of products.

Abstract: Focusing on heritage structures, various non-destructive tests (NDT) or minor-destructive techniques (MDT) can be applied while the application of destructive testing is limited. The probabilistic models for tensile and compressive strengths of historic cast iron are developed on the basis of destructive tests (DTs) and MDTs, respectively. NDT results are critically compared with DTs. It appears that numerous uncertainties affecting estimated resistance can be treated by statistical approaches along with the semi-probabilistic verification method. Non-destructive hardness tests can hardly be used to estimate strength of cast iron and must be supplemented by destructive tests.

Abstract: The method of X-ray fluorescence spectrometry (XRF) for the determination of MgO in magnesia refractories was introduced. The uncertainty of the MgO in refractory materials was analyzed by melting method of XRF. The measurement uncertainty was evaluated, and the related mathematical models was established. The uncertainty of synthetic standard was calculated by the evaluation of the uncertainty of each component standard. And eventually converted to the measurement results to expand the uncertainty. The effects of two melting methods on the uncertainty of magnesium oxide content were compared.

Abstract: The objective of this paper is to present a methodology for the measurement of the uncertainty in the calculation result in the shear strength test. Is intended with this work is to gather subsidies to justify the adoption of the measurement of the uncertainty in calculation procedure as a regulatory requirement and part of the report of wood characterization tests. The motivation for submitting this proposal is due to the difficulty in reaching some technical requirements specified by the rules, especially the requirement on "quality assurance testing and calibration results". The proposed methodology consolidates the procedures necessary to obtain the individual measurement uncertainty of the failure stress and the mean result of the uncertainty of failure stress. This methodology meets the requirements of a quality management system. The uncertainty values of the individual results of failure stress were negligible indicating a high-quality equipment and good calibration of them. The uncertainty of the measurement of the mean failure stress was considerable, indicating the importance of their consideration in the safety of wooden structures.

Abstract: The purpose of this paper is to propose appropriate evaluation method of measurement uncertainty with respect to the measurement results of polymer thin film capacitive humidity sensor according to dew point temperature variation. All of the evaluation process concerning the measurement uncertainty of polymer thin film capacitive humidity sensor is based on experiment and numerical analysis. To estimate uncertainty contribution properly for polymer thin film capacitive sensor strongly influenced by measurement environment, the experiments are performed in the reference relative humidity range from 5 % to 30 % at a setting dry bulb temperature of 23°C. Also, the reference standards are chilled mirror hygrometer (CMH) and platinum resistance thermometer (PRT). In particular, the uncertainty sources are considered differently according to the range of below or above 0°C, reference dew point. From the budgets, uncertainty contributions to the standard uncertainty are clearly dominated by the effect of the uncertainty due to super-cooling in case of condition below 0°C, dew point temperature. Also, the contributions for stability and distribution of humidity generator have a mainly effect on the expanded uncertainty of polymeric humidity sensor. It is desired that measurement uncertainties of polymeric humidity sensor are comprised separately on the basis of reference dew point, 0°C. The evaluation procedure of measurement uncertainty is developed in accordance with the principles established in the documents EA-4/02, Expression of the Uncertainty of Measurement in Calibration [1].

Abstract: This paper analyses the uncertainty of pressure measurements in-cylinder and in injection pipe conducted during the studies of a compression ignition engine. Type A and type B evaluations were used to determine the uncertainties of the results. The results are presented for the engine running on diesel or bio-fuel and operating under full load conditions. The results of normality tests provide grounds to reject H0 in some cases. Slightly lower standard uncertainty of the maximum pressure measurement calculated using type A evaluation were acquired for the engine running on bio-fuel.

Abstract: The purpose of this paper is to analyze the effect of tube length in calibration instrumentation on dew point measurement of dew point sensors (DPS) and evaluation of measurement uncertainty. When measuring dew point temperature, various tube lengths between dew point generator and dew point sensor (DPS) cause a significant error due to moisture absorption of inner tube. The measurement is carried out to analyze the variation on measured dew point temperature for four cases of tube lengths with 300 mm, 1200 mm, 2500 mm and 5000 mm. The dew point temperature measurements were performed in the range from-60 °C to 10 °C by using calibrated standard chilled mirror hygrometer as reference standard. In order to investigate contribution to the standard uncertainty for the tube length variation as an uncertainty source, expanded uncertainties were evaluated for the cases including the effect of tube length variation as an uncertainty source and excluding it at each measurement point. The measurement was conducted according to standard calibration procedure of Korea Testing Laboratory which assures suitability and traceable results. It is also based on international standards.

Abstract: Ball pressure test is the heat resistance test of the electrical products material, whether it meets the requirements of material performance to eliminate security risks. Using reading microscope for ball pressure test measurement and its measurement uncertainty was analyzed in this paper, including measurement uncertainty sources, established mathematical model, uncertainty example and measurement uncertainty result. The measurement uncertainty was analyzed to ensure the accuracy of ball pressure test measurement result.