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Eingeladener Vortrag
- nein (32)
The accuracy and comparability of nanoindentation results depend significantly on the calibration of area function and instrument compliance. The area function results should not depend on the reference material used or on the calibration method (direct or indirect). This has been investigated for 18 different Berkovich tips. A novel calibration method is proposed that confirms the material independence of the area function and gives a force-dependent instrument compliance function. An agreement between direct and indirect calibration could only be achieved by considering a radial displacement correction. Further, it is shown that the transition range from a spherical cap to the correct face angle of the pyramid can extend to a depth of more than 250 nm. A better parameter for the indenter than the tip radius is the offset of the contact radius to the radius of an ideal tip at a depth where the correct face angle is reached.
An extensive comparison between the conventional Vickers hardness at 500 mN and indentation hardness measured with Vickers indenters at 500 mN is presented for up to 20 different materials and for three different instruments. Additionally, the indentation modulus is compared to Young’s modulus, which was measured with alternative methods or taken from the literature. It is shown that the agreement between the results from depth-sensing indentation and the reference values can be improved by additional corrections, for the calculation of the indentation area. With corrections the mean hardness difference to the Vickers hardness reference as average of all investigated materials can be reduced to about 10 % although disturbing pile-up or sink-in effects can still not be considered. For the modulus, the mean difference was only about 6 %.
Force-deformation curves have been acquired using nanoindentation and atomic force microscopy on two amorphous polymer samples. The shape and size of the indenter tip was characterized using a white light interferometer and AFM. The measured nanoindentation curves were fitted with the Hertz equation to calculate the Young's modulus of the polymers. Once the Young's moduli of the polymers were known, AFM was used to acquire force-distance-curves on the same samples. We also used the Hertz theory for the analysis in this case. As a result, the tip radius of the AFM cantilever tip could be measured.
This procedure is proposed as a method to determine the shape and size of AFM tips for the quantitative characterization of surface forces through force-distance curves.
Thin polybutadiene/polystyrene blend films were deposited on glass substrates by spin-coating. The two polymers were chosen, as they are immiscible and differ strongly in their mechanical properties. The blend was characterized with Tapping Mode and force–distance curves. Several advantages of force–distance curves measurements compared to Tapping Mode are shown, most of all the capability of yielding quantitative information about several properties, such as Young's modulus and adhesion. Also the aging behaviour of the blend exposed to air could be observed, in particular the increase of the Young's modulus due to cross-linking and dewetting processes. Additionally, the sample was used to improve the resolution of force–distance curves up to 6 nm, which is to date the best resolution achieved with force–distance curves. Such an improvement resolves the major disadvantage of force–distance curves, compared to other scanning mode, i.e. its inferior resolution.
Möglichkeiten und Grenzen der Bestimmung mechanischer Eigenschaften von Kombinationsschichten
(2011)
Der Vortrag widmet sich der Kratzbeständigkeit-Prüfmethoden und deren Bewertung und beschreibt Begriffe/Definitionen, Wirtschaftliche Bedeutung der Kratzbeständigkeit, Mess- und Prüfverfahren – allgemein (Anwendbarkeit, Messunsicherheit, Validierung), Mess- und Prüfverfahren – speziell die Erzeugung, Prüfverfahren von Einzel- und Vielfach-Kratzern, die Charakterisierung von Verkratzungen und eine zusammenfassende Bewertung im Einzelnen
Der Vortrag widmet sich dem „RITZ-TEST: EVALUIERUNG UND STAND DER NORMUNG“ und beschreibt die Komponenten, Ergebnis und Messgrößen, nicht registrierende Prüfgeräte, Evaluierung Ritz-Test (Makrobereich), den Atlas der Versagensformen, Geräte für den instrumentierten Ritz-Test und die Normung des Ritz-Tests (ASTM) zur Bewertung der Haftfestigkeit“ im Einzelnen.