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Abstract

The article presents the method of identifying surface damage by measuring changes in resistance in graphitebased sensing skin. The research focused on analysis of conductivity anomalies caused by surface damage. Sensitivity maps obtained with Finite Element Method (FEM) in conjunction with the analytical damage model were used to build the coating evaluation algorithm. The experiment confirmed the ability of this method to identify a single elliptical-shape damage. Eight electrodes were enough to locate the damage that covered about 0.1‰ of the examined area. The proposed algorithm can prove useful in simple applications for surface condition monitoring. It can be implemented wherever it is possible to apply a thin layer of conductor to a non-conductive surface.
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Authors and Affiliations

Marek Stepnowski
1
Daniel Janczak
2
Małgorzata Jakubowska
2
Paweł Pyrzanowski
1
ORCID: ORCID

  1. Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Nowowiejska 24, 00-665 Warsaw, Poland
  2. Warsaw University of Technology, Institute of Metrology and Biomedical Engineering, Sw. Andrzeja Boboli 8, 02-525 Warsaw, Poland
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Abstract

Temperature change is one of key factors which should be taken into account in logistics during transportation or storage of many types of goods. In this study, a passive UHF RFID-enabled sensor system for elevated temperature (above 58°C) detection has been demonstrated. This system consists of an RFID reader and disposable temperature sensor comprising an UHF antenna, chip and temperature sensitive unit. The UHF antenna was designed and simulated in an IE3D software. The properties of the system were examined depending on the temperature level, type of package which contains the studied objects and the type of antenna substrate.

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Authors and Affiliations

Kamil Janeczek
Małgorzata Jakubowska
Grażyna Kozioł
Piotr Jankowski-Mihułowicz
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Abstract

Graphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase.

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Authors and Affiliations

Krzysztof Mleczko
Piotr Ptak
Zbigniew Zawiślak
Marcin Słoma
Małgorzata Jakubowska
Andrzej Kolek
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Abstract

The Low Temperature Joining Technique (LTJT) using silver compounds enables to significantly increase the thermal conductivity between joined elements, which is much higher than for soldered joints. However, it also makes difficult to measure the thermal conductivity of the joint. The Laser Flash Analysis (LFA) is a non-intrusive method of measuring the temperature rise of one surface of a specimen after excitation with a laser pulse of its other surface. The main limitation of the LFA method is its standard computer software, which assumes the dimensions of a bonded component to be similar to those of the substrate, because it uses the standard Parker’s formula dedicated for one-dimensional heat flow. In the paper a special design of measured specimen was proposed, consisting of two copper plates of different size joined with the sintered silver layer. It was shown that heat properties of these specimens can also be measured after modifying the LFA method. The authors adapted these specimens by masking the false heat signal sourced from the uncovered plate area. Another adaptation was introducing a correcting factor of the heat travel distance, which was calculated with heat-flow simulations and placed into the Parker’s formula. The heat-flow simulated data were compared with the real LFA measurement results, which enabled estimation of the joint properties, e.g. its porosity.
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Authors and Affiliations

Jerzy Szałapak
Konrad Kiełbasiński
Jakub Krzemiński
Anna Młożniak
Elżbieta Zwierkowska
Małgorzata Jakubowska
Radosław Pawłowski

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