Leibniz-Institut für Werkstofforientierte Technologien - IWT
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Institut für Werkstofftechnik (IWT)
Stiftung Institut für Werkstofftechnik IWT
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DE
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Bremen
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Item-typ:Veröffentlichung, Atomization efficiency enhancement in internal-mixing Y-jet nozzles using distinct dispersing media(2025-09-19); ; 48 42 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, In-situ-Untersuchung von Randschichten während des Gasnitrierens mittels Röntgendiffraktometrie und photothermischer RadiometrieThe aim of most applications of nitriding treatments at steel components is to obtain a compact compound layer and/or a deep diffusion layer. The possibility of a survey of the nitriding treatment by analyzing directly the component´s surface state during the nitriding process is particularly interesting, since it allows a process monitoring and control based on the actual nitriding result. In the present study, two measurement methods were developed and combined with the aim of direct surface state analysis during a nitriding treatment: the in-situ X-ray diffraction method and the photothermal radiometry. An experimental setup including a miniature nitriding furnace was developed in order to allow the combined application of both methods during a nitriding process under controlled atmosphere. In the present work, results of combined in-situ measurements on the steel AISI 4140 regarding the nitride layer formation during nitriding process as well as the nitride layer change during the following denitriding of the layer in nitrogen gas are presented and discussed. The investigations show that the photothermal radiometry is sensitive to the changing surface properties due to growing compound layers and when porous layers are generated. This method has a high potential for implementation in industrial nitriding furnaces, but for this, further development for quantitative evaluations of the measurements will be required.Wissenschaftlicher ArtikelBand:72Heft:395 90 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, A simulation study to systematically evaluate the effects by design modifications in a complex gear geometry on distortion behavior(2025-04-16); In response to economic and ecological demands, weight reduction has become a paramount objective in the automotive industry, driving innovation in materials and component design for lightweight construction. However, achieving lightweight components without compromising production feasibility presents challenges. The process of heat treatment, aimed at enhancing material properties, introduces size and shape alterations, alongside residual stresses, which can impact subsequent manufacturing and component longevity. Understanding the mechanisms behind these changes is crucial for cost-effective design and post-processing. While in-situ measurement techniques are limited in heat treatment facilities, simulation software offers a viable alternative for studying dimensional alterations. Despite recent advancements in simulation tools, the complexity of heat treatment processes demands comprehensive material parameters and boundary conditions, often making computations time-consuming. While existing simulations primarily focus on process optimization and property enhancement, research into the impact of geometric variations on final distortion behavior remains limited. This study aims to bridge this gap by investigating the influence of geometric variations on distortion behavior through heat treatment simulation, contributing to a deeper understanding of lightweight component design optimization. In preparation for the numerical investigations, extensive work was carried out to determine the temperature- and location-dependent heat transfer coefficient (HTC) and the conversion behavior. Extensive calibration and validation work was also carried out. In the numerical area, cyclical boundary conditions were programmed for 3D simulation of the gear. After partial validation, this model was used in close combination with experimental work to evaluate the compensation potential of modified cross-sectional transitions. Ultimately, the model was used to gain a deeper understanding of the complex interplay of geometry, thermal and transformation-induced strains.Dissertation43 28 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Redox Activity and Nano–Bio Interactions Determine the Skin Injury Potential of Co3O4-Based Metal Oxide Nanoparticles toward Zebrafish(American chemical society, 2020-03-19); ; ; ; Redox-active metal oxide nanoparticles show varying oxidizing capacities and injury potentials toward biological systems. Here, two metal oxide libraries including transition-metal-doped Co3O4 and PdO-Co3O4 with strong chemical contacts were design-synthesized and used to investigate their biological injury potential and mechanisms using zebrafish as a model organism. Among different dopants, Cu significantly increased the oxidizing capacity of Co3O4. An increased amount of PdO resulted in higher density of heterojunctions, which also led to higher oxidizing capacity. The oxidizing capacity of these nanoparticles was positively correlated with higher mortality of dechorionated embryos and severe larval skin injury upon exposure. Using transgenic zebrafish Tg(LysC:eGFP), we show in real time that the redox-active nanoparticles induced skin injury and activated the infiltration of immune cells. Such inflammatory response was confirmed by the increased mRNA expression level of Nrf2a, HO-1, IL-1β, and IL-6 genes. Although the exposure to the nanoparticles alone was not lethal, the skin injury did lower the tolerance level against other environmental contaminants. More importantly, after withdrawing from the nanoparticle exposure, larvae with skin injury could recover within 24 h in uncontaminated medium, indicating such injury was transient and recoverable.Wissenschaftlicher ArtikelBand:14Heft:433 36 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The Use of the Size Effect in Grinding for Work-hardeningThis paper shows the possibility of using the size effect of the specific grinding energy for a targeted surface layer work-hardening of metal parts. The research includes the combination of abrasive material removal and plastic deformation in a single grinding step. Therefore high specific energy values are needed and thermal effects counteracting the work-hardening have to be minimised. This can be achieved by low cutting speeds in combination with low depths of cut. The new approach results in an in-process work-hardening of the surface layer, which was found to lead to higher hardness, a compressive residual stress state, and higher wear resistance.Wissenschaftlicher ArtikelBand:56Heft:188 73 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The impact of metal doping on fumed silica structure and amino acid thermal condensation catalytic properties(Springer, 2021-08-18); ; ; ; Fumed silica nanoparticles (FSN) are one of the most common synthetic forms of silica, but prolonged exposure leads to cell toxicity and apoptosis due to reactive oxygen species (ROS) generation and cell membrane perturbation resulting from hydrogen bonding and electrostatic interactions. Increasing attention is being put on synthesizing FSN material that is safer both for workers involved in large-scale industrial production, and consumers coming in contact with FSN additives. In the present work, we explore the molecular structural differences and efficacy of Al- and Ti-metal-doped FSN which has previously been shown to reduce toxicity effects of FSN. We use a combination of 29Si and 27Al solid-state magic angle spinning (MAS) NMR, Raman spectroscopy, and thermogravimetric analysis (TGA) to probe the surface and bulk structure and quantify the adsorption capacity and reactivity of the metal-doped FSN with respect to amino acid thermal condensation. Alanine was selected as the amino acid of choice for its simplicity and ubiquity in biochemical reactions. The results indicate that metal doping has a modest impact on the fumed silica molecular structure with a small decrease in amino acid adsorption capacity and thermal condensation reactivity as a function of increased metal doping.Wissenschaftlicher ArtikelBand:5644 72 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Thermo-mechanical tool setting mechanism for ultra-precision milling with multiple cutting edges(2019-01); Ultra-precision milling operations are particularly ineffective machining processes, due to the fact that they are typically operated with a singular cutting edge (fly-cutting). For meeting the tight tolerances of optical and high precision surfaces, a nanometer precision tool setting mechanism is mandatory when adding more cutting edges. On the basis of a theoretical assessment of the surface generation, this paper presents a novel tool setting mechanism based on a thermo-mechanical actuator that has specific advantages compared to electrical or mechanical solutions. The prototype design for a two-tool holder for diamond milling using this actuator is presented and the choice of substrate material is assessed by FEM simulations. It was found that 1.2083 type steel potentially offers a larger stroke and therefore was chosen for the prototype. Next, the requirements for the heat input are discussed and a novel device for quasi-continuous heating during spindle rotation—an IR-LED ring light—is presented. Using the ring light, it is demonstrated that the tool holder can be selectively heated and a localized expansion of up to 1 μm is achievable at a spindle speed of 240 min-1.Wissenschaftlicher ArtikelBand:5580 58 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Beating Thermal Coarsening in Nanoporous Materials via High-Entropy DesignControlling the feature sizes of 3D bicontinuous nanoporous (3DNP) materials is essential for their advanced applications in catalysis, sensing, energy systems, etc., requiring high specific surface area. However, the intrinsic coarsening of nanoporous materials naturally reduces their surface energy leading to the deterioration of physical properties over time, even at ambient temperatures. A novel 3DNP material beating the universal relationship of thermal coarsening is reported via high-entropy alloy (HEA) design. In newly developed TiVNbMoTa 3DNP HEAs, the nanoporous structure is constructed by very fine nanoscale ligaments of a solid-solution phase due to enhanced phase stability by maximizing the configuration entropy and suppressed surface diffusion. The smallest size of 3DNP HEA synthesized at 873 K is about 10 nm, which is one order of magnitude smaller than that of conventional porous materials. More importantly, the yield strength of ligament in 3DNP HEA approaches its theoretical strength of G/2π of the corresponding HEA alloy even after thermal exposure. This finding signifies the key benefit of high-entropy design in nanoporous materials—exceptional stability of size-related physical properties. This high-entropy strategy should thus open new opportunities for developing ultrastable nanomaterials against its environment.Wissenschaftlicher Artikel134 346 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Diamond Micro Chiseling of large-scale retroreflective arrays(2012-06-18); ; Triple mirror retroreflectors are essential components for safety applications, communications and measurement equipment. While downscaling of characteristic dimension is possible for triangular retroreflectors, this is a challenging task for full-cube retroreflectors, due to the absence of continuous tool paths. Thus, the Diamond Micro Chiseling (DMC) process has been developed which allows the machining of full-cube retroreflectors by overlapping a series of sharp-edged pyramidal microcavities. In the past, this has been successfully demonstrated on a small-scale up to 3 mm × 3 mm with a structure size of 150 μm. Industrial applications, however, require the structuring of areas which are significantly larger than 10 mm × 10 mm. This paper will introduce the technology for machining such pattern with the help of the DMC process. Particular attention will be given to the measurement procedures and required tolerances for performing an in situ tool change as well as the optimization strategies for reducing the required process time.Wissenschaftlicher ArtikelBand:36Heft:4205 378 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Influence of gear hobbing feed marks on the resulting gear quality after discontinuous profile grindingGear hobbing is one of the most common soft-machining processes for pre-toothing. The process kinematics result in a characteristic tooth-flank topography, which is mainly determined by so-called feed marks. For an economical finishing process by gear grinding in automotive applications, the feed-mark depths should not exceed a maximum value of 35 mm. In the present study the validity of this limit has been investigated in view of the development of increasingly powerful grinding machines and grinding wheels. For this purpose, gears with feed-mark depths dx below and above 35 mm were machined and ground by means of discontinuous profile gear grinding afterwards. The influence of the feed marks on the grinding process with roughing parameters was systematically evaluated on the basis of various process variables such as the increase in spindle power Ps or the degree of grinding-wheel clogging Zs, while the resulting gear quality was mainly analyzed by various parameters to describe macro- and micro-geometry deviations of the ground tooth flanks. With increasing feed-mark depth, an increase in spindle power was found due to the additional machined volume. An influence of increasing feed-mark depths on the clogging degree, the grinding-wheel wear and the gear quality could not be proven. Therefore, economical finishing of gears by gear grinding is also possible with feed-mark depths of more than 35 mm. A new definition of this limit should be sought.Wissenschaftlicher ArtikelBand:31119 127