Examination of the energy phase space of mixed copper grain boundaries by EBSD and the sphere-on-a-plate method

This article reports on an experimental study of the energy phase space of mixed copper grain boundaries by a combination of electron backscatter diffraction (EBSD) and the so-called sphere-on-a-plate method. Single crystal copper spheres with diameters of a few microns were sintered onto flat single crystal {1 1 1} copper plates, resulting in random initial grain boundary configurations. EBSD measurements together with an assumption about the grain boundary plane orientation were used for the determination of the five macroscopic degrees of freedom of the grain boundaries. The tilt and twist components of the grain boundaries were calculated making use of the interface plane scheme representation of grain boundaries. Upon annealing, the spheres rotated along gradients in the grain boundary energy phase space. Thus, points of the trajectories of single spheres could be recorded between the single annealing steps, allowing for tracing the path of single spheres towards and into energy minima regions. The results gathered from 13 spheres underline a strong complexity of the grain boundary energy phase space.     

Adhesive bonding of CFRP: a comparison of different surface pre-treatment strategies and their effect on the bonding shear strength

A promising joining technology for thermoset CFRP is adhesive bonding. However, the mechanical performance is influenced negatively by contaminants, like release agents, as well as an excess of matrix in the top layer. In order to generate most suitable surface qualities prior to the bonding process, carbon fibre reinforced plastics are treated with different – UV (355 nm) and IR (1064 nm) – lasers. The results are compared to commonly applied grinding surface preparation. The preliminary results on surface properties, e.g. energy and topography point towards high levels of free surface energy, as well as new originated surface structures. After the bonding process mechanical tests are subsequently carried out in Mode II, to characterize the final joint by its tensile shear strength. Finally, the individual fracture behaviour is examined in post mortem analysis. The results indicate that it is possible to increase the tensile shear strength of the joints to a maximum, which equals the interlaminar shear strength of the CFRP-laminate. Therefore, ultrashort pulsed IR-laser techniques show the best reproducibility and the highest tensile shear strength. In addition, IR-laser treatment is expected to have the highest potential for later applications.     

Operational behavior and application regime assessment of the magnetic acceleration plasma facility IMAX

Design, operation and application of pulsed magnetoplasmadynamic self-field accelerators are described and the facility IMAX (Institut für Raumfahrtsysteme der Universität Stuttgart (IRS), Magnetoplasmadynamic Accelerator-Experiment), is considered in further detail on the basis of an experimental reference condition at a capacitor bank load voltage of 12 kV and an ambient air pressure of 10⁻³ Pa. This high power coaxial accelerator has been investigated for space propulsion and for terrestrial plasma processes in particular for metal treatment. Lessons learnt from the operation of the facility and its potentially dangerous functional behavior are discussed. Its operational sensitivities are depicted by numerical analysis using an advanced snowplow model. The analysis shows consistency with previously reported experimental results.     

Ionic liquid based absorption chillers for usage of low grade waste heat in industry

The standard working pairs for absorption chillers, ammonia/water and water/lithium bromide show problematic behaviours like crystallisation and corrosiveness. Because of their convenient solving properties and their low vapour pressure, ionic liquids are a new promising class of sorbents for absorption cooling purposes. In this study, the working pairs water/1,3‐dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and water/1‐ethyl‐3‐methylimidazolium dimethylphosphate ([EMIM][DMP]) are implemented in AspenPlus. The performance of a single effect cycle with these pairs is simulated and compared to results of a cycle with water/LiBr. For [EMIM][DMP] a coefficient of performance (COP) comparable to that of LiBr or even higher (up to 0.85) is found. [MMIM][DMP] shows a smaller maximum COP but a largely wider operating temperature range than LiBr. Results are compared with those of other groups, discrepancies discussed and improvements suggested. Copyright © 2013 John Wiley & Sons, Ltd.     

Processing Fiber-Reinforced Polymers: Specific Wear Phenomena Caused by Filler Materials

Fiber-reinforced polymers allow for the implementation of plastic materials in structural components. However, increasing incorporation of fibers up to 50 wt% causes accelerated component wear in injection molding machines. In particular, the barrel and screw in the compression zone suffer from increased wear. The abrasive fibers of the compacted polymer pellets in the solid bed protrude from the surfaces of the resin having an abrasive, brush-like behavior. A modified pin-on-disk testing system with specially designed polymer pins was used to emulate the described tribological system in laboratory scale. Through varying contact pressure, temperature, and surface modifications of the counterparts (blank or coated powder-metallurgical steel), abrasive wear as observed in industrial-sized extruder screws could be successfully simulated on a laboratory-scale testing system. Detailed investigations of the pins and disks highlighted that the glass fibers plow and cut the surface leading to abrasion as observed in the real field application. Temperature has been proven to be the most decisive driving force. Surface modifications such as protective physical vapor-deposited CrN coatings are effective against abrasive wear, clearly outperforming untreated steels. The presented pin-on-disk-test setup will improve screening of materials for extruders, thus enhancing the durability of injection molding machines. POLYM. ENG. SCI., 60:78–85, 2020. © 2019 Society of Plastics Engineers     

Lanthanide and Heavy Metal Free Long White Persistent Luminescence from Ti Doped Li–Hackmanite: A Versatile,Low‐Cost Material

Persistent luminescence (PeL) materials are used in everyday glow‐in‐the‐dark applications and they show high potential for, e.g., medical imaging, night‐vision surveillance, and enhancement of solar cells. However, the best performing materials contain rare earths and/or other heavy metal and expensive elements such as Ga and Ge, increasing the production costs. Here, (Li,Na)₈Al₆Si₆O₂₄(Cl,S)₂:Ti, a heavy‐metal‐ and rare‐earth‐free low‐cost material is presented. It can give white PeL that stays 7 h above the 0.3 mcd m^?2 limit and is observable for more than 100 h with a spectrometer. This is a record‐long duration for white PeL and visible PeL without rare earths. The material has great potential to be applied in white light emitting devices (LEDs) combined with self‐sustained night vision using only a single phosphor. The material also exhibits PeL in aqueous suspensions and is capable of showing easily detectable photoluminescence even in nanomolar concentrations, indicating potential for use as a diagnostic marker. Because it is excitable with sunlight, this material is expected to additionally be well‐suited for outdoor applications.     

How Good Is My Test Data? Introducing Safety Analysis for Computer Vision

Good test data is crucial for driving new developments in computer vision (CV), but two questions remain unanswered: which situations should be covered by the test data, and how much testing is enough to reach a conclusion? In this paper we propose a new answer to these questions using a standard procedure devised by the safety community to validate complex systems: the hazard and operability analysis (HAZOP). It is designed to systematically identify possible causes of system failure or performance loss. We introduce a generic CV model that creates the basis for the hazard analysis and—for the first time—apply an extensive HAZOP to the CV domain. The result is a publicly available checklist with more than 900 identified individual hazards. This checklist can be utilized to evaluate existing test datasets by quantifying the covered hazards. We evaluate our approach by first analyzing and annotating the popular stereo vision test datasets Middlebury and KITTI. Second, we demonstrate a clearly negative influence of the hazards in the checklist on the performance of six popular stereo matching algorithms. The presented approach is a useful tool to evaluate and improve test datasets and creates a common basis for future dataset designs.