Dynamic micro testing over more than 5 decades of strain rates

Based on the combined experience in micro testing [1] and testing under crash and impact loads [2] at Fraunhofer Institute for Mechanics of Materials IWM, a new testing system was developed for micro sample testing over a wide range of strain rates. The aim was to realize a testing facility allowing the investigation at small sample sizes, taken out of sheet materials or components for local material characterization over a large range of strain rates [3]. The first application and reference testing series was performed at a dual phase steel HCT490X rolled to a thickness of 0.56 mm with sample main dimensions of 3.5 mm x 3.5 mm. These tests were performed in parallel with mini tensile samples (Fig. 1, right) at a conventional fast servo hydraulic testing machine (VeryHighSpeed, VHS) at com parable strain rates, ranging from 0.001 s-1 up to 1000 s-1 [3] These parallel testing series showed up the benefit of small micro samples for strain rate dependent investigations. The micro sample tests showed comparable stress strain reactions with significant smaller oscillations in the force signal than the mini sample test. For this strain rate range the oscillations in the force signals were significantly improved compared to the conventional tests. For ongoing tests the samples were prepared out of different polymer materials including long fiber reinforced thermoplastics (LFT). These tests focus on the investigation in homogenous local material reaction to different loading velocities. For these tests, the sample preparation was already a challenge that was overcome using micro water jet cutting with a well-defined process chain and sample finishing. The test series are subject of actual investigations. In this paper an overview of the actual status of dynamic micro testing is given

Rateneffekte und Skaleneffekte bei der Werkstoffprüfung auf der Mikroskala

Kenntnisse der lokalen Werkstoffeigenschaften sind eine grundlegende Voraussetzung der erfolgreichen Umsetzung der Digitalisierung der Werkstoffe. Im Belastungsbereich verschiedener Dehnraten liegen fast keine durchgehenden transiente experimentellen Daten lokaler Werkstoffeigenschaften vor. Um diese Lücke zu schließen wurde eine variabel dynamische Mikroprüfung entwickelt. Die Versuchsanlage IWM DynMicro wurde an 0.5 mm dickem Dualphasenstahl HCT490X erprobt und durch Vergleichsversuche mit größeren Proben an einer konventionellen Schnellzerreißmaschine verifiziert. Untersuchungen die nur mit Mikroproben möglich sind werden an dem Beispiel PP LGF 30 dargestellt. An diesem Werkstoff wird gezeigt, wie lokale Effekte das homogenisierte Verhalten einerseits beeinflussen aber auch davon abweichen

Zoonotic helminths affecting the human eye

<p>Abstract</p> <p>Nowaday, zoonoses are an important cause of human parasitic diseases worldwide and a major threat to the socio-economic development, mainly in developing countries. Importantly, zoonotic helminths that affect human eyes (HIE) may cause blindness with severe socio-economic consequences to human communities. These infections include nematodes, cestodes and trematodes, which may be transmitted by vectors (dirofilariasis, onchocerciasis, thelaziasis), food consumption (sparganosis, trichinellosis) and those acquired indirectly from the environment (ascariasis, echinococcosis, fascioliasis). Adult and/or larval stages of HIE may localize into human ocular tissues externally (i.e., lachrymal glands, eyelids, conjunctival sacs) or into the ocular globe (i.e., intravitreous retina, anterior and or posterior chamber) causing symptoms due to the parasitic localization in the eyes or to the immune reaction they elicit in the host. Unfortunately, data on HIE are scant and mostly limited to case reports from different countries. The biology and epidemiology of the most frequently reported HIE are discussed as well as clinical description of the diseases, diagnostic considerations and video clips on their presentation and surgical treatment.</p> <p><b><it>Homines amplius oculis, quam auribus credunt</it></b></p> <p><b>Seneca Ep 6,5</b></p> <p><b>Men believe their eyes more than their ears</b></p