Pompejiföreställningen : Undersökningar av det historiska odlingslandskapets destruktiva inverkan på järnålderbosättningen vid Änge, Buttle socken. Rapport från arkeologisk undersökning vid Buttle Änge 2017. Del II

In the preface to his and Gerda Boëthius' book on Gotland's Iron Age settlement sites, John Nihlén described the stone wall house sites and 'adjoining field walls' as Sweden's Pompeii. The description vividly illustrate how Nihlén perceived the preservation status of the stone wall houses. Nihlén seems to have thought that the stone wall houses had been covered by a 'protecting layer of volcanic dust' and laid untouched since the day they had been abandoned. Even though most of Nihlén's theories on the Iron Age settlement sites of Gotland has since been dismissed, the 'Pompeii idea' has seemingly been passed on to later generations of researchers (as for instance in the work of Carlsson 1979 and Cassel 1998). This conception is however far from accurate. Field inventories on Central and Eastern Gotland, as well as cartographical studies and the result of the excavations at Änge, Buttle parish has clearly demonstrated how the stone wall house sites has been damaged and affected by cultivation and other activities during Early Modern and Modern times. To further investigate and document the impact and extent of destructive elements on stone wall house sites, special attention was given to the topic during the 2017 excavation campaign at Änge. The survey was divided into three different sections; 1. Excavation and analysis of the construction and chronology for so called 'field walls' or ancient enclosures [sw. stensträngar]; 2.To evaluate the hypothesis that 'impediments' (marked objects in fields) on historical maps represent ancient remains, particularly stone wall houses; and finally 3. to define the spacial extent of the Iron Age settlement site, to be able to conclude which of the historical features that can be labelled as 'destructive elements'. The fieldwork section of the project was carried out within the borders of the research projects Climate Change and Social Competition: re-approaching the Archaeology of Gotland AD 300-900 and Houses and Hierarchies: From Roman to Viking influences on Gotland Island in the Baltic sea, and conducted in July and August of 2017 in conjunction with Uppsala university campus Gotland's summer-semester fieldwork-course for archaeology students. The excavation documentation and the preliminary results of the survey is presented in this report.OBS: Andreeff är författare för 2017, del 1; Melander är författare för 2017, del 2.</p

The significance of microstructure heterogeneities on the fatigue thresholds of aluminum castings

Industrial in-series aluminum castings contain a wide range of microstructural heterogeneities like differences in secondary dendrite arm spacing (SDAS), eutectic silicon and intermetallic precipitates of varying morphologies and diverse-shaped and-sized porosity. Regarding to technical and economic limitations, the complete elimination of them is hard to achieve, which requires conservative design, i.e., increased wall thicknesses to accommodate the failure tolerance. To improve the performance of cast aluminum products concerning safety and fatigue properties, the present work deals with the significance of such structures with respect to the threshold for crack propagation ΔKI,th under pure bending and the fatigue behaviour in the high-and very-high-cycle-fatigue regime (HCF and VHCF). Therefore, two automotive cast alloys taken from engine blocks (AlSi8Cu3) and cylinder heads (AlSi7Cu0.5Mg) and a gravity die cast set (AlSi7Mg0.3), either T6 conditioned or additionally hot isostatic pressed (HIP), were used. For in-series castings, two positions of maximal difference in cooling rate and respective microstructure were extracted. With this set of specimens, the significance of SDAS in interaction with (i) eutectic silicon regions, (ii) intermetallic precipitates in varying occurrence, (iii) the crystallographic orientation, and (iv) the porosity in correlation with the fatigue threshold is shown and compared with first results of fatigue damaging mechanisms in quasi pore-free material

The significance of microstructure heterogeneities on the fatigue thresholds of aluminum castings

Industrial in-series aluminum castings contain a wide range of microstructural heterogeneities like differences in secondary dendrite arm spacing (SDAS), eutectic silicon and intermetallic precipitates of varying morphologies and diverse-shaped and-sized porosity. Regarding to technical and economic limitations, the complete elimination of them is hard to achieve, which requires conservative design, i.e., increased wall thicknesses to accommodate the failure tolerance. To improve the performance of cast aluminum products concerning safety and fatigue properties, the present work deals with the significance of such structures with respect to the threshold for crack propagation ΔKI,th under pure bending and the fatigue behaviour in the high-and very-high-cycle-fatigue regime (HCF and VHCF). Therefore, two automotive cast alloys taken from engine blocks (AlSi8Cu3) and cylinder heads (AlSi7Cu0.5Mg) and a gravity die cast set (AlSi7Mg0.3), either T6 conditioned or additionally hot isostatic pressed (HIP), were used. For in-series castings, two positions of maximal difference in cooling rate and respective microstructure were extracted. With this set of specimens, the significance of SDAS in interaction with (i) eutectic silicon regions, (ii) intermetallic precipitates in varying occurrence, (iii) the crystallographic orientation, and (iv) the porosity in correlation with the fatigue threshold is shown and compared with first results of fatigue damaging mechanisms in quasi pore-free material