Development of an Ultralight with a Ducted Fan

This paper introduces the UL-39 project, an ultralight aircraft with a ducted fan, and some of the problems that have arisen in the course of its development. Several problems with the design of a non-traditional aircraft of this kind are mentioned, e.g. the design of the airframe, and the design of the propulsion unit. The paper describes the specific procedure for determining the basic thrust characteristics of this unusual aircraft concept, and also the experimental determination of these characteristics. Further options for applying the experience gained during the work, and the futurefocus of work on these issues, are outlined at the end of the paper

The effect of production parameters on the plasticity of structural steel

Diplomová práce se zabývá vlivem tepelného zpracování a doby skladování na mikrostrukturu a mechanické vlastnosti oceli 26MnB5, která se používá pro výrobu trubkových součástí tvářených v zušlechtěném stavu. Cílem bylo zvýšit plasticitu oceli definováním nových procesních parametrů linky indukčního tepelného zpracování. Byly stanoveny nové popouštěcí diagramy oceli 26MnB5 pro dvě různé rychlosti zušlechťovací linky, na jejichž základě byla stanovena nová popouštěcí teplota a rychlost linky. Sledování vlivu doby skladování na mechanické vlastnosti oceli neodhalilo, že by podléhala stárnutí.The master thesis deals with the influence of heat treatment and storage time on microstructure and mechanical properties of 26MnB5 steel, which is used in the production of tubular components in the quenched and tempered state. The objective was to increase the plasticity of the steel by the definition of new process parameters of the induction heat treatment line. New tempering diagrams of 26MnB5 steel for two various speeds of the heat treatment line were established and used to determine new tempering temperature and speed of the heat treatment line. Observation of the influence of storage time on mechanical properties of the steel did not reveal that it is liable to ageing.

Analysis of surface defects in composites using digital image correlation and acoustic emission

This work employs the acoustic emission (AE) method for material state monitoring. AE presents a non-destructive evaluation technique, which could be used for detection of microstructural changes in composite material. Work describes the process of acquisition of AE in tensile loading of carbon composite materials. In course of tensile stress, the composite was monitored with optical method, applying principles of digital image correction (DIC). Optical stereovision method enables calculation of field shift and field of proportional deformation at composite surface. The objective is analysis of damage in carbon composite materials and employ the methodology of AE signal processing for facilitation of early damage diagnostics and prediction of structural failure. For this purpose, the experimental setup was designed to obtain results from 50 nominally identical composite samples in tensile loading test. Force load applied on samples was synchronically recorded along with AE and image data. Experimental data were subsequently analysed in a way enabling the description of typical phenomena in course of every measurement. Results show that observation of AE sources could be employed in facilitation of early damage diagnostics and establishment of failure prognosis. It is about internal changes in composite material.O

Elasto-plastic material model of oak at two moisture content levels

The mechanical properties of wood show a very high dependence on the moisture content (MC). A consideration of MC in numerical simulations increases the applicability of such prediction with respect to application and moisture states of the wood material. The goal of this work is to develop an accurate orthotropic elasto-plastic model for oak wood (Quercus robur L.) at two different MC levels applicable for finite element analysis (FEA). To achieve this goal, the following steps were carried out: (a) in-house standard specimens tests in compression, tension, and shear and in all three orthogonal directions, followed by three-point bending, where all specimens were conditioned to a 12 and 25.6% MC, prior to the mechanical test; (b) integration of all obtained material characteristics into the consistent numerical material models; (c) validation of the developed material models by comparing the numerically predicted values with the experimental ones; and (d) iterative calibration of the material models by adjusting the individual material characteristics to minimize error using a reference. Material models were successfully developed with the following mean relative errors: 5.2% for 12% MC and 5.8% for 25.6% MC, respectively. Both numerical material models consistently predicted the oak elasto-plastic response that can be easily integrated into any FEA.OA-hybri

Auditive Wissenskulturen: Wissen, Macht und die Welt der Klänge

In der Einleitung zum Sammelband Auditive Wissenskulturen – Das Wissen klanglicher Praxis stellen die Autoren zuerst die Diskrepanzen der jeweiligen Beziehungen des Visuellen und des Auditiven zu Wissen anhand einiger Beispiele vor. Sie exemplifzieren auch, wie sowohl auditive Praxis als auch die Hervorbringung und Vermittlung von Wissen in soziale Prozesse eingebunden sind und damit einhergehend mit Machtverhältnissen in Verbindung stehen. Die Erforschung von Klang durch Sound Studies und anthropologische Studien werden genauer behandelt, ebenso Gemeinsamkeiten und Unterschiede in den Herangehensweisen an Klänge seitens der Wissenschafen und der Künste. Schließlich schlagen sie vor, den Begrif der Wissenskulturen als Forschungsstrategie zum Verstehen von auditivem Wissen zu benutzen, um explizites und implizites Wissen, wissenschafliche und künstlerische, sowie klangproduzierende Prozesse und Hörverständnis gleichermaßen innerhalb sozialer und kollektiver Felder beschreib- und analysierbar zu machen. Diese Forschungsstrategie wird anhand einer Übersicht über die Beiträge im vorliegenden Band im Detail vorgestellt

Using 3D digital image correlation in an identification of defects of trees subjected to bending

Abrupt changes of climate have intensified during the last few decades, bringing higher risks from tree failures by either uprooting or stem breakage. To eliminate the risks, many techniques of tree assessment are being used. In the presented work, an optical technique based on 3D Digital Image Correlation (3D-DIC) was investigated as one of the tools to be used in identification of tree defects. Within the work, two ash trees were examined by pulling tests coupling 3D-DIC and standard techniques. The trees were measured in five consecutive steps of artificially made defects of two kinds - root and stem damage. We hypothesized defects can be identified using full-field strains and displacements. Results indicated that 3D-DIC provides comparable strains as standard semi-destructive extensometers. Statistical tests (α = 0.05) showed the 3D-DIC technique method is capable of identifying changes of displacements and strains after creating artificial defects in trees. However, despite the statistical differences, the practical arboricultural considerations of findings are still limited due to low absolute differences. The study also suggests there might exist path-dependency of the defect creation order when evaluating stiffness/strains from extensometers of two different positions. This could have impact on a practical assessment of tree stability in the future, but it must be further tested on larger data sets due to the proof-of-concept character of this work. In general, 3D-DIC brings extensive improvement in data acquisition quality and quantity, especially from the perspective of natural variability and heterogeneity in trees and wood.OA-hybri

Thermally modified (TM) beech wood: compression properties, fracture toughness and cohesive law in mode II obtained from the three-point end-notched flexure (3ENF) test

[EN] The fracture properties of thermally modified beech (Fagus sylvatica) wood (TMW) at 180 degrees and 200 degrees C were evaluated in mode II using the three-point end-notched flexure (3ENF) scheme assisted by three-dimensional (3D) stereovision equipment for obtaining displacements and strains. The compliance-based beam method (CBBM) provided the strain energy release rates (G(II)) of TMW and cohesive laws for both native wood (W) and TMW. Based on the CBBM and equivalent crack length approach (ECLA), G(II) was obtained directly from the force-deflection data. The thermal modification (TM) process reduced the compressive strength by 4.4% and increased the compressive elastic modulus by 38.3%, whereas G(II) was reduced substantially by 40.8% and 67.9% at TM180 degrees C and TM200 degrees C, respectively. TM also increased wood brittleness that was visible on the displacement slip reduction. The resulting mean cohesive models can be used for numerical analyses. The fracture properties of TMW have to be taken into consideration for constructional wood application, when cyclic loading may lead to microcracking and material fatigue.The authors would like to thank COST Action FP1407 (Funder Id: https://dx.doi.org/10.13039/501100000921), the European Commission for funding the InnoRenew CoE project under the Horizon2020 Widespread-Teaming program (grant agreement #739574), the Republic of Slovenia for providing support from the European Regional Development Funds, and the financial support provided by the Internal Grant Agency (IGA) of the Faculty of Forestry and Wood Technology, Mendel University in Brno (LDF_PSV_2016015).Sebera, V.; Redón-Santafé, M.; Brabec, M.; Decky, D.; Cermak, P.; Tippner, J.; Milch, J. (2019). Thermally modified (TM) beech wood: compression properties, fracture toughness and cohesive law in mode II obtained from the three-point end-notched flexure (3ENF) test. Holzforschung. 73(7):663-672. https://doi.org/10.1515/hf-2018-018866367273

Plasticity increase of beech veneer by steaming and gaseous ammonia treatment

Ammonia treatment was used in order to change the colour of wood and also to plasticize the wood before bending or compressing. The mechanism and the process of gaseous ammonia treatment impact on wood are not very well known. The goal of this study was to quantify the effect of gaseousammonia on mechanical properties, i.e., modulus of elasticity (MOE), modulus of rupture (MOR) and deflection at maximal loading force (yFmax). When wood was treated by water and ammonia vapour together, significant changes in plasticity of wood were observed. The samples which were firstlyexposed to water vapour and then to ammonia vapour exhibit the lowest values of MOE and MOR and an enhanced flexibility of the material. The results show that ammonia treatment increases wood plasticity. This process can be used for manufacturing of bent furniture