Beulverhalten von ringversteiften Kreiszylinderschalen unter Axialdruck – Teil 1: Versuche und geometrische Imperfektionsanalyse/Buckling behavior of ring-stiffened cylinder shells under axial pressure – Part 1: Tests and geometric imperfection analysis

Moderne Behälter werden oft als ringversteifte Kreiszylinderschalen ausgeführt. Der traglaststeigernde Effekt eng liegender Ringsteifen unter Axialdruck erfuhr in der Forschung bis heute nur geringe Beachtung. Er ist bisher ungeregelt und infolge unnötig hohen Materialeinsatzes bleiben Stahlbehältern Marktanteile und bessere Nachhaltigkeit verwehrt. Anhand von Versuchen und einer numerischen Studie werden die neuesten Forschungsergebnisse des Einflusses der Ringsteifen auf das Axialbeulverhalten von Kreiszylinderschalen erläutert. Die Ergebnisse zeigen, dass die ringversteiften Kreiszylinder unter Axialdruck nach der aktuellen Bemessungspraxis unwirtschaftlich bemessen werden.   Im Teil 1 dieses Beitrags werden Versuche im verkleinertem Maßstab durchgeführt, um den Einfluss der Ringsteifen auf das Beulverhalten der Kreiszylinderschalen unter Axialdruck zu erforschen. Gemäß einem Vergleich von Versuchsergebnissen wird eine mehrfach höhere Tragfähigkeit ringversteifter Schalen gegenüber unversteiften Schalen ermittelt. Die geometrischen Imperfektionen des Probekörpers werden durch eine 3D-Scan-Technologie gemessen und danach mittels der Methode der Fourier-Reihen analysiert. Im Teil 2 folgen die numerische Simulation und das Ableiten eines Ingenieurmodells.

Effect of Global Ventilation to Perfusion Ratio, for Normal Lungs, on Desflurane and Sevoflurane Elimination Kinetics

Background Kinetics of the uptake of inhaled anesthetics have been well studied, but the kinetics of elimination might be of more practical importance. The objective of the authors’ study was to assess the effect of the overall ventilation/perfusion ratio ( .VA/.Q ), for normal lungs, on elimination kinetics of desflurane and sevoflurane. Methods The authors developed a mathematical model of inhaled anesthetic elimination that explicitly relates the terminal washout time constant to the global lung .VA/.Q ratio. Assumptions and results of the model were tested with experimental data from a recent study, where desflurane and sevoflurane elimination were observed for three different .VA/.Q conditions: normal, low, and high. Results The mathematical model predicts that the global .VA/.Q ratio, for normal lungs, modifies the time constant for tissue anesthetic washout throughout the entire elimination. For all three .VA/.Q conditions, the ratio of arterial to mixed venous anesthetic partial pressure Part/Pmv reached a constant value after 5 min of elimination, as predicted by the retention equation. The time constant corrected for incomplete lung clearance was a better predictor of late-stage kinetics than the intrinsic tissue time constant. Conclusions In addition to the well-known role of the lungs in the early phases of inhaled anesthetic washout, the lungs play a long-overlooked role in modulating the kinetics of tissue washout during the later stages of inhaled anesthetic elimination. The .VA/.Q ratio influences the kinetics of desflurane and sevoflurane elimination throughout the entire elimination, with more pronounced slowing of tissue washout at lower .VA/.Q ratios. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Reversal modeling and optimal design of hyper-elastic diaphragm in space fuel tanks

Diaphragm tanks are a common type of pressurized tanks in which the diaphragm is used to separate the fuel part from the high-pressure part, compress the fuel in the tank, and reduce free space to avoid liquid fuel sloshing. The main purpose of the application of the diaphragm tanks is to ensure the continuous flow of pure fuel without the gas bubble into the spacecraft engine. In space mission, diaphragm tanks will experience a wide range of acceleration at different levels of filling. These conditions change the state of equilibrium between the volume of the gas and the fluid and move the diaphragm toward the discharge portion of the tank. As a result of this movement, the diaphragm curvature is changed and the structure collapses at rest, which is called folding. When large nonlinear folding occurs, there is potential for diaphragm damage through wear, rubbing, and excessive stress. Predicting diaphragm behavior in order to calculate a diaphragm’s susceptibility to corrosion, rupture, and surface strain is one of the major design challenges. In this study, new method is provided to analyze deformation of diaphragm tanks by using numerical techniques. Also, the investigation method is verified by using experimental methods. In this process, first a 3D numerical model is developed to investigate the inverse behavior of a hyper-elastic diaphragm by using ANSYS software and the results of the simulations are compared with the results of experimental tests in the same situation. After validation, a second case study is performed to survey the effect of reducing diaphragm thickness according to the strain energy and natural frequency behavior of the diaphragm in different fill levels. The results of this study showed that numerical simulations are capable of reconstructing diaphragm inversion properties with good accuracy. In addition, the numerical model can detect the proper thickness for the diaphragm. In the last section, algorithm and software for optimal automatic modeling of diaphragm tanks are proposed.

Determining High-Temperature Oxidation Resistance of (TI-Al-X-N) Based Coatings for Titanium Alloys

Basic titanium alloys are successfully used in modern aviation GTE (gas turbine engine). They are used for parts of a compressor and partly in low pressure part of turbine (intermetallic Ti-Al alloys) due to their high specific strength and at the same time low density, high corrosion resistance but can be used only up to 700 °C. The paper deals with the results of heat resistance testing at 750 °C of Ti-Al-(X)+N based thin ion-plasm multilayers coatings, with different priority of monolayers- intermetallic, conglomerate or nitride for gas turbine engine (GTE) blades from titanium alloys. All coatings showed high resistance during the test, with a maximum efficiency 42.8 of coating with a priority of conglomerate after 30 hours of testing.

Revalorisation of the Szewalski’s concept of the law of varying the last-stage blade retraction in a gas-steam turbine

The article presents the implementations of the free vortex law to the blade of the last stage of a gas-steam turbine. First, a thermodynamic analysis was carried out, determining the parameters at the inlet, then the number of stages of the high and low-pressure part of the turbine was constructed, together with the kinematics and velocity vectors for subsequent stages of the axial turbine. The last step of article was to take into account the law of variation of the peripheral component of the velocity of the medium working with the radius of the turbine in a discrete way and to make a 3D drawing of the resulting geometry. When creating the spatial model, the atlas of profiles of reaction turbine stages was used.

Structural Transformations in Crystals Induced by Radiation and Pressure. Part 10. The Crystallographic Picture of Photochemical Behaviour of bi(anthracene-9,10-dimethylene) under High Pressure

The results of the monitoring of the [4 + 4] photocycloaddition reaction path in single crystals of bi(anthracene-9,10-dimethylene) at high pressure are presented. The crystal structures for several steps of the phototransformation at 0.3 GPa and 1.0 GPa were determined and analysed. The applied high pressure did not halt the photochemical reaction and almost 100% of the product molecules were obtained, although the reaction was very slowly reversible similarly to that of ambient conditions. During the crystal phototransformation the intramolecular geometry, molecular orientation and intermolecular interactions of the reactant changed more and more towards the values observed for the product. The initial increase in the unit cell volume brought about by the photochemical reaction was diminished by high pressure. High pressure itself did not significantly influence the intramolecular geometry of the reactant and product molecules, but it influenced the intermolecular interactions.