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Page 140 of 977 Results 1391 - 1400 of 9762

Andreas Kinzel, Nicole Dittmar
Monitoring of Penetration System Performance according to ISO 3452-1 by using Test Panels according to ISO 3452-3

Penetrant testing (PT) is one of the first ever industrial established non-destructive testing for detecting surface discontinuities. Because of its outstanding sensitivity as well as easy use this test procedure is even today widely used in various fields of industry. As example can be mentioned automotive industry or aerospace industry. PT also can be used for manually testing of single parts as well as automatically testing of repetition parts in serial production. Increasing of demands with respect to quality assurance aspects requires procedures to verify the test itself. Developing these verification procedures have been started by the 1970s whereas the actual verification procedure is described by standard ISO 3452-1. Alteration of penetration system performances is often known if the penetrant is used repeatedly or the penetrant is kept in open bins. Further aspects are subjected to the penetrants shelf life and other conditions of use as for example ultraviolet radiation, temperature, contamination or evaporation. So, the penetration system performance has to be monitored by the user periodically by using a »Test Panel Type 2« according to ISO 3452-3. Experiences have indicated further that the test panel itself and especially its artificial defects have to be inspected periodically. The artificial defects can appear less than original because of pollution. And it is also possible that the dimensions of these defects can increase by chemical strain or thermal stress. So, a calibration of test panels has to be done annually. Using test panels correctly enables the user to monitor the penetrant test in order with the technical standard as well as to guarantee a high performance in application. MPA Hannover has a lot of long-lasting experiences in production and calibration of test panels for PT. From 1987 till 1995 »Test Panels Type B« according to DIN 54152-3 have been produced. Since 1995 »Test Panels Type 2« according to technical standard ISO 3452-3 are produced and delivered worldwide. On basis of the outstanding experiences MPA Hannover accredited according to ISO/IEC 17025 for verification of »Test Panels Type 2« according to ISO 3452-3. By this, MPA Hannover is a qualified partner for industrial customers.

Tomáš Klier, Tomáš Míčka, Michal Polák, Milan Hedbávný
Application of the Modified Magnetoelastic Method

In technical practice there is very often a requirement of axial force determination in important structural elements of a building or engineering structure during its construction or operational state. In civil engineering practice, five experimental techniques are usually used for evaluation of axial tensile forces in these elements. Each of them has its advantages and disadvantages. One of these methods is the magnetoelastic method. The paper presents general principles of the magnetoelastic method, the magnetoelastic sensor layout and actual information and knowledge about practical application of the new approach based on the magnetoelastic principle on prestressed concrete structures. Subsequently, recent results of the experimental verification and the in situ application of the method are described in the text. The described experimental approach is usable not only for newly built structures but in particular for existing ones. Furthermore, this approach is the only one effectively usable experimental method for determination of the prestressed force on existing prestressed concrete structures in many cases in the technical practice.

Álvaro Silva Ribeiro,Luís Lages Martins, M.C Almeida, João Alves e Sousa
Optical Metrology Applied to Testing and Inspection in Civil Engineering

Optical metrology has an increasing impact on observation and experimental activities in Civil Engineering, contributing to the investigation and development of innovative, non-invasive techniques applied in testing and inspection of infrastructures to ensure safety and quality of life. Advances in specific applications are presented in the paper, highlighting the application cases carried out by LNEC (the Portuguese National Laboratory for Civil Engineering). The examples include: (i) structural monitoring of a long-span suspension bridge; (ii) use of close circuit television (CCTV) cameras in drain and sewer inspection; (iii) calibration of a large-scale seismic shaking table with laser interferometry; (iv) destructive mechanical testing of masonry specimens. Current and future research work in this field is emphasized in the final section. Examples given are related to the use of Moiré techniques for digital modelling of reduced-scale hydraulic surfaces and to the use of laser interferometry for calibration of strain measurement standard for the geometrical evaluation of concrete testing machines.

Dávid Maklári, Tamás Bodolai
Effects of Environmental Phenomena on EMC Measurements

The EMC (Electromagnetic Compatibility) is one of the most important sectors in electronic industrial and in retail area as well. As more devices and “gadgets” are connected to network via wireless communication as more challenging to avoid any malfunctioning during normal operation. The main focus is to determine how much noise come from our devices and how much they can be immune to noises before causing any problem in their normal operation. Because this high sensitivity, reaction and interaction of the environmental factors - building - EMC chamber – measurement equipment and UUT (unit under test) as a whole system should be deeply understood and analyzed. One of the most important such problems is the earthing of the chamber and the building. As a requirement of Albatross Projects GmbH (manufactureer of University of Miskolc EMC chamber), the chamber needs an earthing point with less than 1 Ohm. As well-known as less the grounding resistance as better the performance. But the question is how the effect of the grounding resistance can be determined and calculated. The difference between 1.1 Ohm and 0.9 Ohm matters in the practice. In many cases EMC chambers are installed into an existing building where this 1 ohm can be hardly achieved therefore relation between resistance value and the measurement performance should be determined.

Tomislav Škreblin,Goran Košir, Franjo Bijelić
Roller Brake Tester Measurement Uncertainty Calculation

This article contains a description of the technical, process-related and organizational procedures which accredited calibration laboratories use as a model for defining internal processes and regulations. By implementing these procedures, it is ensured that the devices to be calibrated are all treated equally in the various calibration laboratories and that the continuity and comparability of the work of the calibration laboratories are improved. The calibration certificates issued by the accredited laboratories prove the traceability to national standard as required by Standard HRN EN ISO/IEC 17025:2017 [1]. This procedure defines minimum requirements to be met by work area and equipment required to calibrate a measuring instrument used for measuring braking force on the periphery of wheels of road vehicles (hereinafter: roller brake tester), as well as the calibration procedure and the estimation of the measurement uncertainty. This article describes static method for calibration of roller brake testers. Some of the measurement uncertainty contributions stated in this document as most relevant contributions that have to be considered during uncertainty calculation, may still be exempted from measurement uncertainty calculation. In those cases calibration laboratory must prove the exemption by reasonable means such as calculations, measuring results, statistics, etc.

Peter Benko, Trevor Toman
Covariance in 3D measurement uncertainty evaluation

The accepted way of expressing measurement results is through an estimated value and its associated measurement uncertainty. Part of the uncertainty evaluation is also to consider mutual sources of uncertainties, called covariance. This paper will describe a CMM 3D measurement and its uncertainty evaluation. A 3D measurement considered here is a length measurement in three orthogonal directions along the x, y, z axes of a Cartesian coordinate system. When a point in 3D space is located it is considered to be a direct method of measurement. However, when it comes to geometrical features such as the radius of a circle (hole), sphere, cylinder, cone etc. the measurement should be considered as an indirect method of measurement. Therefore, for both the above-mentioned methods, the procedure given by ISO/IEC Guide 98-3:2008 is to apply the law of propagation in uncertainty. Standards such as ISO 10360 and VDI/VDE 2617 supply guidelines for the understanding of uncertainty contributions to 3D measurement uncertainty, and standard ISO 15530-3 describes techniques for determining uncertainty. However, these standards do not consider uncertainties having a mutual source to be dealt with as covariance. This study presents a new approach to evaluating measurement uncertainty for 3D measurement, which helps to conclude where in 3D space the measurement is most affected by uncertainties.

António Santos, Álvaro Silva Ribeiro, Luís Lages Martins
Contribution of the Measurement Uncertainty of the Daylight Factor in Buildings for the Comparison of Experimental Methods

Lighting has a major role to environmental comfort and energy efficiency in buildings, being related to parameters that establish comfortable visual environment suitable for the execution of visual tasks. The lighting of interior spaces can be accomplished using natural light, artificial light or, preferably, using a combination of the two. The measurement of Daylight Factor (DF) is required as a quantity to characterize the indoor luminous environment in buildings. The measurement of lighting conditions is usually carried out taking into account the recommendations and the reference illuminance levels contained in Standards EN 12464-1 [1], providing the conditions to indoor electric lighting, and EN 17037 [2], providing the framework of daylight in buildings, being still under evaluation to accomplish a wide variety of real scenarios. Although the characterization of artificial lighting conditions is relatively common, the systematic “in situ” assessment of daylighting conditions still has to solve the differences arising from the use of different available methods and the impact of external obstructions in the accuracy, and the suitability of the experimental approaches. In this paper, the evaluation of measurement uncertainty related with the Daylight Factor, obtained using four different experimental methods is developed and a comparison of the accuracy of the methods results is given, providing a tool to validation and to support decision-making processes.

Filip Flego, Marija Pavlović, Siniša Prugovečki
Quantification of Misunderstanding: A Case of Tolerance Limits against Calibration Uncertainty in ISO/IEC 17025 Accredited Laboratories

Measurement uncertainty undoubtedly plays a large role in the assessment of compliance with certain specifications. For example, the widely accepted ILAC G8:09/19 publication gives relatively flexible guidelines for assessing the conformity of certain instruments to their respective standards or specifications. On the other hand, the information given in calibration certificates is often interpreted too rigorously which can, unfortunately, lead to the false conclusion that the instrument in question doesn’t actually meet the client’s specified requirements. In the following paper we will examine the role measurement uncertainty has in the assessment of compliance with regards to specified tolerance limits for 5 different instruments: calipers, contact thermometers (at temperatures above 600 °C), hygrometers, temperature chambers (such as laboratory incubators or refrigerators) and piston pipettes.

Ivana Ljevaković-Musladin
Measurement Uncertainty According to ISO 19036:2019

ISO 19036 is an international standard that specifies and gives guidance for the estimation and expression of measurement uncertainty (MU) associated with quantitative results of microbial counts in foods. Standard describes top-down or global approach to MU, in which MU is calculated from experimental results with replication of the same analyses as part of the measurement process and expressed as a standard deviation of reproducibility of the final result. In a new revision from 2019 standard ISO 19036 considers three types of MU component: technical uncertainty, matrix uncertainty and distributional uncertainty. The aim of this study was to estimate all components of MU according to standard ISO 19036:2019. Technical uncertainty was estimated for quantitative enumeration tests for coagulasepositive staphylococci, Listeria monocytogenes, Escherichia coli, Enterobacteriaceae and aerobic mesophilic bacteria, while matrix uncertainty was estimated for ice cream, cheese, ready-to-eat vegetables, ready-to-eat food and cream cakes. Technical uncertainty was estimated from a reproducibility standard deviation of the final result of measurement process while the matrix uncertainty was estimated from within-sample variance by examination of multiple test portions from laboratory sample. Distributional uncertainty is estimated mathematically. The study showed that technical uncertainties of quantitative methods performed in our laboratory are the same magnitude and quite low. Matrix uncertainty was the largest contributor to combined uncertainty in composite food matrices. Our results are better than or in a close agreement with results from method validation interlaboratory studies and other published data.

Damir Ilić
The Role of Measurement Uncertainty in the Decision Making for Testing and Inspection

In this paper is analysed the influence of the expanded uncertainty in the conformity assessment based on the international standards and documents. The different approaches for the calculation of combined standard uncertainties are given, based both on the worst possible consideration up to the implementation of corrections as appropriate. Furthermore, the influence of the effective degrees of freedom and t-distribution is pointed as well. The calculations are presented on the example of the testing and/or inspection of the current instrument transformers test for accuracy.

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