Vera Rede

Measurement and control of copper and tin coatings

Abstract Comparison of thickness measurement for selectively applied copper and tin coatings on printed circuit boards was performed by use of destructive and non-destructive methods. The analysis of measurement results was performed by applying criterion of critical difference of repeatability and reproducibility according to international standard ISO 5725-(1-6):1994. Comparison of results for measuring ranges on the basis of critical difference of reproducibility, shows that results of measurement for copper and tin coatings obtained by using different methods are mutually comparable. In measuring tin coating, repeatability of measurement results was achieved and that means that results obtained in very strict conditions are comparable.

Statistical analysis of fracture toughness of SiC ceramics determined by Vickers indentation method

In this paper fracture toughness, KIC, of CVD SiC ceramics was determined by measuring the crack lengths associate with a Vickers indentation. It is well known that the measured fracture of brittle ceramics shows large variability. Therefore, the probabilistic characteristics of fracture toughness were analysed by a two–parameter Weibull distribution function, with scale parameter, K0, and the Weibull modulus, m. These parameters were determined by the linear regression method for KIC data measured at load of 9.81, 29.43, 49.01 and 98.1 N, respectively. It was found that the measured fracture toughness follow a Weibull distribution.

Determining the Fracture Toughness of Alumina Ceramics from Vickers Indentations

Abstract Many methods are currently used to measure fracture toughness of ceramic materials. Due to its simplicity, its non-destructive nature, and the fact that minimal machining is required to prepare the sample, the use of the Vickers hardness indentations to measure fracture toughness (KIC) has become quite popular. The aim of the present work is to investigate the hardness from Vickers indentations and the fracture toughness based on crack-length measurements of cracks introduced into the sample surface of cold isostatically pressed (CIP)-Al2O3 with 99.8% purity.

Characterization of Thermal Oxides on Austenitic Stainless Steel

Abstract In this paper, phases, chemical compositions and size of thermal oxides on an austenitic stainless steel AISI 316L were investigated. The steel specimens were subjected to isothermal heating at 200 °C up to 1000 °C in order to simulate production conditions and then compared with unheated specimens. X-ray diffraction analysis, Auger electron spectroscopy, Scanning electron microscopy and optical micrography have been used for characterization of the thermal oxides on the steel specimens.

Influence of thermal oxides on pitting corrosion of austenitic and duplex steels

Abstract The influence of thermal oxides on the pitting corrosion of austenitic and duplex (austenitic-ferrite) steels has been studied. Austenitic steel specimens AISI 316L were subjected to heating isothermally (200 to 1000 °C) in order to simulate conditions of the application in production. Duplex steel specimens AISI S31803 were heated isothermally at (1100 to 1300 °C) in order to simulate welding parameters. The characterization of thermal oxides formed by heating isothermally on austenitic steel was performed by AES, and XPS analyses. The microstructures and thickness of thermal oxides on austenitic specimens and microstructures on duplex specimens was determined. Pitting susceptibility of such specimens was tested by exposure to FeCl3 solution at 22 ±2 °C during 72 h (ASTM G 48-99a). Pitting criteria show that oxides developed at 600 °C cause the highest susceptibility to pitting corrosion for austenitic steel and 1300 °C for duplex steel.