Mycologg: a new accelerated test method for wood durability above ground
If not properly handled, selected and protected, wood will be degraded by bacteria, fungi and also insects. In order to ensure service life, durability tests are needed. Most accelerated laboratory tests on wood durability are focused either on fungi attacks or the uptake of moisture. Accelerated field tests in ground contact are of limited use since they could be difficult to reproduce and are sensitive to the characteristics of the soil in which the wood is placed. In addition, the results cannot be directly transferred to wood in use above ground because such wood is subjected to different set of conditions. The Mycologg is a new accelerated test method for estimating the durability of wood in above ground applications. The Mycologg allows the test panels to be subjected to the discolouring fungi and different RH (relative humidity) cycles simultaneously. Every 30 min, the temperature, the RH, and the moisture content in each test panel are measured and saved in special software. This allows for a constant update of the moisture patterns during a fungi attack. A trial was made with Scots pine (Pinus sylvestris) heartwood samples, where fungal growth after 6, 8 and 10 weeks in the Mycologg were compared to weather exposure of duplicate samples after 12, 16, and 26 months. The results showed that 10 weeks into the Mycologg accelerated test method corresponds well to real-time weather exposure with respect to fungal discolouration.
Development of a new rapid method for mould testing in a climate chamber: preliminary tests
The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12–14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.ZusammenfassungZweck dieser Studie war die Entwicklung eines schnellen, einfachen und robusten Verfahrens zur Prüfung von Schimmelbefall auf Massivholz im Labor. Ziel war es, die Anfälligkeit von in der Prüfkammer unterschiedlich angeordneten Prüfkörpern für Schimmelbefall zu untersuchen. Die vorgeschlagene Methode basiert auf natürlicher Kontamination nicht steriler Oberflächen in Klimata, die Schimmelwachstum fördern. Hierfür wurde eine Klimakammer mit regulierbarer Temperatur und relativer Luftfeuchte verwendet. Die Klimakammer wurde mittels einer horizontal über dem Ventilator angebrachten dünnen Edelstahlplatte in einen oberen und einen unteren Teil abgeteilt, um die Luftzirkulation im Bereich der Prüfkörper in der oberen Kammer zu minimieren. Von Schimmel befallene Prüfkörper aus Freilandversuchen dienten als Infektionsquelle. An Kiefernsplintholz (Pinus sylvestris L.) wurden Testversuche durchgeführt. Die Prüfkörper wurden an der Decke der oberen Kammer aufgehängt und in der Kammer wurden verschiedene Temperatur- und Feuchteniveaus eingestellt. Nach 12-14 Tagen wurde starker Schimmelbefall festgestellt. Anschließend wurde der Befall visuell bewertet. Abgesehen von einigen Einschränkungen erwies sich diese Methode als sehr einfach, schnell und effektiv. Noch wichtiger war jedoch, dass dieses Verfahren, im Vergleich zu anderen Prüfverfahren, Schimmelbefall am realistischsten modelliert.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.