Volume 52, Issue 3

Kurzfassung Zur Toxizität von Brandgasen insbesondere von organischen Stoffen liegen bisher noch unzureichende Erkenntnisse vor, obwohl diese für die Sicherheit der damit konfrontierten Personen oft von entscheidender Bedeutung sind. Ziel der hier dargestellten Untersuchungen ist es, die Zusammensetzung des Brandgases und die Menge der Brandgaskomponenten im Brandfall zu beurteilen und zu quantifizieren sowie entsprechende Prozeduren hierfür aufzuzeigen. Dazu wurden verschiedene Brandszenarien, die durch Verwendung von unterschiedlichen Arten von Prüföfen simuliert wurden, sowie Proben in den unterschiedlichen Größenmaßstäben untersucht. Durch den Einsatz eines mobilen FTIR-Gerätes (Fourier Transformations Infrarot Spektroskopie) ist es experimentell möglich, zeitaufgelöst quantitative Bestimmungen einzelner toxischer Brandgaskomponenten während der jeweiligen Brandszenarien zu ermitteln und somit eine Abschätzung der Toxizität vorzunehmen. Am Beispiel von Polyvinylchlorid (PVC) wird gezeigt, welche Auswirkungen die unterschiedlichen Brandszenarien auf die qualitative und quantitative Brandgaszusammensetzung haben.

Oxide dispersion strengthening of high-Cr steels is a well-recognized way to extend the application window including nuclear applications for this class of materials. The experimental investigation of model alloys of less complexity is important in order to separate individual influence factors and to understand the irradiation behaviour. The present work is devoted to the mechanical properties of ODS Fe-9wt%Cr alloys produced by means of spark plasma sintering. The range of material conditions covers contents of nanodispersed yttria of 0 (reference), 0.3 wt%, and 0.6 wt% as well as variations of the milling time. Results obtained for the density, elastic properties, hardness, tensile behaviour, and brittle-ductile transition are reported, and the effect of ODS content and PM process parameters is discussed.

Kurzfassung Zahlreiche Schadensfälle aus der Praxis belegen, dass die bestehenden Normen die Betriebssicherheit moderner Sportfahrräder nicht in ausreichendem Maße gewährleisten können. Im Rahmen eines Drittmittelprojektes am Fachgebiet für Sportgeräte und Materialien der Technischen Universität München sind aktuelle Betriebslastenkollektive für Mountainbikes und Rennräder ermittelt worden. Parallel dazu wurden Prüfstände für sicherheitsrelevante Bauteile entwickelt und aufgebaut, auf welchen nun Betriebsfestigkeitsnachweise in Form von mehrachsialen Blockversuchen geführt werden können.

Kurzfassung Im vorliegenden Beitrag werden Prüfverfahren und Vorgehensweisen vorgestellt, um Fahrräder auf ihre Betriebsfestigkeit hin zu testen und die Sicherheit solcher Verkehrsmittel, Spiel- und Sportgeräte zu erhöhen.

Kurzfassung Die Analyse der Temperaturverteilungen und temperaturbedingten Spannungen in Walzen beim Warmwalzen [1, 2] ermöglicht die Entwicklung von Bewertungskriterien sowie die Bestimmung der Einsatzbedingungen der Walzen in einem Walzgerüst beim Warmwalzen und erleichtert das Auswahlprinzip des Walzenwerkstoffs. Solche Kriterien sind bei der Auswahl des Walzenwerkstoffs mithilfe eines Prüfstandes wichtig.

Homogenization of aluminum extrusion billets facilitates extrusion and improves product quality. In this work, a parameter has been developed that defines the homogenization level of AA6063 extrusion billets. The insoluble α-AlFeSi and β-AlFeSi phases have been experimentally determined by evaluating the length/width ratio of the AlFeSi intermetallic in the microstructure. Using this identification, the area fraction of each phase has been measured. The area fraction of the β-AlFeSi phase in the cast structure is over 65%. In the well-homogenized sample, the β-AlFeSi area fraction decreases to values lower than 20%, while the α-AlFeSi phase ratio increases to over 80%. As the α-AlFeSi percentage in the structure increases, the elongation of the samples steadily increases, from 1% to 24%. Based on the ratio of α-AlFeSi to the entire intermetallic phase, we propose six different homogenization levels. The proposed indexing can be used to define the homogenization state of the billet, regardless of the homogenization temperature and time. The index numbers exhibit a good correlation with the deformation potential of the samples.

The determination of the size of flaws in the bulk of duplex stainless steels and the determination of the Probability of Detection (POD) from ultrasonic data is addressed. The ferritic-austenitic mixed microstructure of these steels causes a strong attenuation of the ultrasonic waves. Therefore, the Synthetic Aperture Focusing Technique SAFT has been applied which leads to a reduction of the microstructural noise signals and thus to an improvement of defect detection. Based on the ultrasonic rf-data acquired on a test block with model defects an â-versus-a-approach has been performed to determine the POD for the inspected duplex specimen according to MIL-HDBK-1823. It is shown that SAFT-processing of the ultrasonic data leads to a remarkable improvement of defect detectability.

The failure of cracked components is governed by the stresses in the vicinity of the crack tip. The singular stress contribution is characterized by stress intensity factors. The stress intensity factors depend on the geometry of the component and on loading condition. This paper addresses the evaluation of stress intensity factors (SIFs) of opening, shearing and tearing modes for compact tension specimens for bonding homogeneous materials. The aim of this work is to find the optimal pre-cracked length, crack notch radius, and crack notch angle in order to eliminate the effect of them on the SIF and then on the fracture toughness. To achieve this goal, a three- dimension finite element analysis (FEA) model using the ANSYS program is constructed for specimens made of homogeneous materials such as stainless steel bonding with epoxy as a filler material. The effects of notch angle, notch tip radius and pre-crack length on the stress intensity factors are studied for different fracture modes. The results for the stress intensity factors K I , K II and K III are obtained using the linear elastic fracture mechanics (LEFM) approach.

The development of micro-electro-mechanical systems (MEMS) is a subject of intense research due to the significant impact of miniaturization. The assembly of micro-devices involves handling of parts that are extremely small. A micro-gripper compliant mechanism is one of the key elements in micro-robotics as well as micro-assembly technologies for handling and manipulating micro-objects without damage. Topology optimization has proven to be a power- ful method for the conceptual design of structures and mechanisms. This paper presents topology optimization of three-dimensional micro-gripper compliant mechanism with straight-line path and with parallel movement gripping arms. A three-dimensional finite element analysis model using ANSYS is constructed for the propose design domain. The optimal configuration micro-grippers, which can realize a straight-line path and parallel movement of the gripping arms, are demonstrated.

This contribution presents an estimation of the measurement uncertainty of coating thickness measurement results. The measurements were performed on a steel sheet sample with an outside shell plating. The sample is protected against corrosion with two layers of 100 ¼m thick dry film. In the present case, the criteria of “80-20” have been applied. The measurement uncertainty evaluation has been carried out using Monte Carlo simulations (MCS method) in accordance with the document OIML G 1-101 Edition 2008 (E) Evaluation of Measurement Data – Supplement 1 to the Guide to the Expression of Uncertainty in Measurement – Propagation of Distributions Using a Monte Carlo Method. The criteria “80-20” was evaluated based on the mean coating thickness measurement results, as well as, on the basis of the complete measuring information. Aside from the expected value, complete measuring information comprises the value of measurement uncertainty. In the case where measurement result is described only as the mean of the measurement values a wrong conclusion regarding the fulfillment “80-20” is reached.