Leibniz-Institut für Werkstofforientierte Technologien - IWT
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Institut für Werkstofftechnik (IWT)
Stiftung Institut für Werkstofftechnik IWT
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Item type:Publication, 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.journal articleBand:56Heft:188 73 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.doctoral thesis43 28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal article134 346 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal articleBand:36Heft:4205 376 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal articleBand:31119 126 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 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.journal articleBand:72Heft:394 90 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Atomization efficiency enhancement in internal-mixing Y-jet nozzles using distinct dispersing media(2025-09-19); ; 48 40 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comprehensive analysis of the thermal impact and its depth effect in grindingThe focus of this work is the analysis of the thermal impact and its depth effect in different grinding processes. The investigated processes cover different kinematics and thus broad ranges of the relative speeds and the intensities of the moving heat source regarding the ground surface. A uniform lower process limit characterizing the onset of grinding burn for the different kinematics is identified by means of the specific grinding power and the contact time. The experimental results together with the theoretical considerations of peak temperatures lead to the conclusion that the process specific range of the contact time is mainly responsible for the thermal depth effect. The results enable the targeted exceeding of the critical process limit in roughing and the subsequent correction by finishing.journal articleBand:70Heft:1134 156 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Impact of process flow conditions on particle morphology in metal powder production via gas atomizationAdditive manufacturing processes as for instance selective laser melting or electron beam melting are becoming more common and just turning into standard manufacturing processes for metal components. Nevertheless, these processes are still new compared to classic powder metallurgy manufacturing routes such as pressing and sintering. Hence not all necessary requirements for the powders in use are fully known yet. This makes an increase in control of the powder properties a crucial task to achieve. To reach this goal one must understand the different influences on the powder production process from the beginning of the whole production route. In this work, the influence of the spray chamber flow on the particle morphology is examined. The nozzle system used to produce the metal powders is a close-coupled atomization system with a convergent-divergent gas nozzle configuration. The particle morphology as well as the particle size distribution have been analyzed to examine the influence of the atomization gas flow compared to an additional use of a coaxial gas flow. To review the changes of the flow patterns, computational fluid dynamic simulations have been performed. The particle trajectories were calculated to assess the change in particle behavior as well. Atomization experiments have been conducted with an AISI 52100 (1.3505) steel in a small batch atomization plant to evaluate the influence of the change in flow on the particle size distribution and circularity. The experimental results show that a use of additional coaxial gas leads to an increase in particle circularity up to 10% for relevant particle sizes. An approach for the quantification of satellite occurrence is given by examination of the shift of the particle size distribution to smaller diameters.journal articleBand:31Heft:182 118 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Laseradditive Fertigung von Ti-6Al-4V: Prozessschrittübergreifende Korrelation zwischen Einzelfaktoren und resultierenden Eigenschaften(2025-12-11); ; 98 75