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In this presentation the actual state of the ongoing investigations of spray painting processes are summarized. Already at the end of the last century, first experimental and numerical work was done aiming to estimate the film thickness distribution and the transfer efficiency of spray painting processes of complex workpieces. First successful numerical simulations basically used the classical Euler-Langrange approach, in case of electrostatically supported atomizers extended by the necessary models for the charging of droplets and the interaction between charged droplets and electrical fields. Measured droplet size distributions and velocities near the atomizers have been applied as inlet conditions for the simulations.
Effects of Reusing Polyamide 12 Powder on the Mechanical Properties of Additively Manufactured Parts
(2022)
This paper describes the modelling, simulation and energy management of a fuel cell hybrid heavy-duty truck. For this purpose, a longitudinal dynamic model of a 26t truck was set up and the load requirement for the drive train was determined based on a driving cycle. To meet this load requirement as efficiently and dynamically as possible three different energy management strategies were implemented, tested and the impact on the overall system was analysed. In addition, the behaviour of the hybrid system with the various energy management strategies with different battery capacity is shown and analysed.
Application of Induction Thermography for Detection of Near Surface Defects in Steel Products
(2020)
Infusion stands are a central tool in health care. They are mainly found in hospitals, are
usually in use for many years, sometimes carry enormous loads (e.g. irrigation solutions,
perfusors), are also used by mobility-impaired persons to support walking, promote mobility
and self-determination during ongoing infusion therapy, and must be stored in sufficient
numbers. The weaknesses of the existing design of infusion stands are well known to users.
Nevertheless, for decades there has been no further development or adaptation to new,
changed requirements, let alone to new technical possibilities. In the short term, it makes
sense to further develop the existing infusion stand models in an evolutionary manner in
order to quickly produce an improvement in the functions and to mitigate the greatest
weaknesses. In this respect, the project team has shown in the context of technical
developments that there are very simple, but in terms of functionality, safety and data
protection very worthwhile adaptations that can and should be taken up by the industry. The
redesign of the basic element alone brings so much improvement for the use of this aid that
an industrialization in several senses – for the individual and society – would be more than
promising. With this research project, the project group would like to give an impulse for the
participatory involvement of users in assistive technology research. The user groups can
participate in different phases of the product development; at least the products should be
evaluated regularly in their application by the users.
The objective of this study is to investigate the influence of veneering technique (hand-layering vs. milling) on the fracture resistance of bi-layer implant-supported zirconia-based hybrid-abutment crowns. Mandibular molar copings were anatomically designed and milled. Copings were then veneered by hand-layering (HL) (n = 20) and milling using the Cad-On technique (LD) (n = 20). Crowns were cemented to zirconia hybrid-abutments. Ten samples of each group acted as a control while the remaining ten samples were subjected to fatigue in a chewing simulator. Crowns were loaded between 50 and 100 N for 1.2 million cycles under simultaneous temperature fluctuation between 5 and 55 °C. Crowns were then subjected to static load a to fracture test. Data were statistically analysed using the one-way ANOVA. Randomly selected crowns from each group were observed under scanning electron microscopy to view fractured surfaces. Study results indicate that during fatigue, LD crowns had a 100% survival rate; while HL crowns had a 50% failure rate. Fracture resistance of LD crowns was statistically significantly higher than that of HL crowns at the baseline and after fatigue (p ≤ 0.05). However, fatigue did not cause a statistically significant reduction in fracture resistance in both LD and HL groups (p > 0.05). Copings fractured in the LD crowns only and the fracture path was different in both LD and HL groups. According to the results, it was concluded that milled veneer implant-supported hybrid-abutment crowns exhibit significantly higher fracture resistance, and better withstand clinical masticatory loads in the posterior region compared to the hand-layered technique. Also, fatigue application and artificial aging caused no significant strength reduction in both techniques. Clinical significance: Different veneering techniques and materials (hand-layering or milling) act differently to clinical forces and environment and may be prone to early chipping during service. Therefore, practitioners are urged to consider the appropriate veneering protocol for posterior implant-supported hybrid-abutment restorations.
Our current mobility paradigm increasingly faces economic, ecological, and social limits in urban areas. The aim of this paper is to analyse if a fleet of shared autonomous electric vehicles (AEVs) can meet these challenges while satisfying the current requirements of privately-owned internal combustion engine vehicles (ICEVs). Therefore, analytical models have been developed to simulate and investigate the impacts of mobility behaviour in Berlin and Stuttgart (Germany). The collected data were used to calculate the fleet size, the energy consumption, the emission of particulate matter, nitrogen oxides, and the carbon footprint of different shared AEVs in comparison with privately owned ICEVs. The approach shows that the system of a shared AEV fleet could lower externalities (accident avoidance, traffic jams, free spaces, parking costs and lifetime losses) in cities and generate cost benefits for customers.
HElmar-LiMo 2040
(2023)
Approach to denoising of interfered 4-channel FMCW radar data using Convolutional Neural Network
(2023)
Approach to denoising of interfered 4-channel FMCW radar data using Convolutional Neural Network
(2023)
TCP Usage Guidance in the Internet of Things (IoT), draft-ietf-lwig-tcp-constrained-node-networks-13
(2020)
This document provides guidance on how to implement and use the Transmission Control Protocol (TCP) in Constrained-Node Networks(CNNs), which are a characteristic of the Internet of Things (IoT).Such environments require a lightweight TCP implementation and may not make use of optional functionality. This document explains a number of known and deployed techniques to simplify a TCP stack as well as corresponding tradeoffs. The objective is to help embedded
developers with decisions on which TCP features to use.
OAFuser: Online Adaptive Extended Object Tracking and Fusion using automotive Radar Detections
(2020)
This paper presents the Online Adaptive Fuser: OAFuser, a novel method for online adaptive estimation of motion and measurement uncertainties for efficient tracking and fusion by applying a system of several estimators for ongoing noise along with the conventional state and state covariance estimation. In our system, process and measurement noises are estimated with steady-state filters to obtain combined measurement noise and process noise estimators for all sensors in order to obtain state estimation with a linear Minimum Mean Square Error (MMSE) estimator and accelerating the system’s performance. The proposed adaptive tracking and fusion system was tested based on high fidelity simulation data and several real-world scenarios for automotive radar, where ground truth data is available for evaluation. We demonstrate the proposed method’s accuracy and efficiency in a challenging, highly dynamic scenario where our system is benchmarked with Multiple Model filter in terms of error statistics and run time performance.
Hot isostatic pressing can be utilized to reduce the anisotropic mechanical properties of Al–Si–Mg alloys fabricated by laser powder-bed fusion (L-PBF). The implementation of post processing densification processes can open up new fields of application by meeting high quality requirements defined by aircraft and automotive industries. A gas pressure of 75 MPa during hot isostatic pressing lowers the critical cooling rate required to achieve a supersaturated solid solution. Direct aging uses this pressure related effect during heat treatment in modern hot isostatic presses, which offer advanced cooling capabilities, thereby avoiding the necessity of a separate solution annealing step for Al–Si–Mg cast alloys. Hot isostatic pressing, followed by rapid quenching, was applied to both sand cast as well as laser powder-bed fused Al–Si–Mg aluminum alloys. It was shown that the critical cooling rate required to achieve a supersaturated solid solution is significantly higher for additively manufactured, age-hardenable aluminum alloys than it is for comparable sand cast material. The application of hot isostatic pressing can be combined with heat treatment, consisting of solution annealing, quenching and direct aging, in order to achieve both a dense material with a small number of preferred locations for the initiation of fatigue cracks and a high material strength.
Comparing multidimensional sensor data from vehicle fleets with methods of sequential data mining
(2020)
A matter of reality
(2018)
Due to the increasing relevance of data, more and more data from various sources is accumulated for a variety of purposes. At the same time, however, there is a shortage of data in areas where it is urgently needed. Particularly in the field of machine learning, there is a lack of good and usable training data. Therefore, this research paper is concerned with the virtual data acquisition for the training of neural networks. For this purpose, first an application was developed that aims to generate virtual, automatically labeled data. Subsequently, a neural network was trained on the generated virtual data and tested on real data.
A matter of reality
(2018)
Due to the increasing relevance of data, more and more data from various sources is accumulated for a variety of purposes. At the same time, however, there is a shortage of data in areas where it is urgently needed. Particularly in the field of machine learning, there is a lack of good and usable training data. Therefore, this research paper is concerned with the virtual data acquisition for the training of neural networks. For this purpose, first an application was developed that aims to generate virtual, automatically labeled data. Subsequently, a neural network was trained on the generated virtual data and tested on real data.
An optimal control problem for equations with p-structure and its finite element discretization
(2022)
Laser powder-bed fusion (LPBF) has significantly gained in importance and has become one of the major fabrication techniques within metal additive manufacturing. The fast cooling rates achieved in LPBF due to a relatively small melt pool on a much larger component or substrate, acting as heat sink, result in fine-grained microstructures and high oversaturation of alloying elements in the α-aluminum. Al-Si-Mg alloys thus can be effectively precipitation hardened. Moreover, the solidified material undergoes an intrinsic heat treatment, whilst the layers above are irradiated and the elevated temperature in the built chamber starts the clustering process of alloying elements directly after a scan track is fabricated. These silicon-magnesium clusters were observed with atom probe tomography in as-built samples. Similar beneficial clustering behavior at higher temperatures is known from the direct-aging approach in cast samples, whereby the artificial aging is performed immediately after solution annealing and quenching. Transferring this approach to LPBF samples as a possible post-heat treatment revealed that even after direct aging, the outstanding hardness of the as-built condition could, at best, be met, but for most instances it was significantly lower. Our investigations showed that LPBF Al-Si-Mg exhibited a high dependency on the quenching rate, which is significantly more pronounced than in cast reference samples, requiring two to three times higher quenching rate after solution annealing to yield similar hardness results. This suggests that due to the finer microstructure and the shorter diffusion path in Al-Si-Mg fabricated by LPBF, it is more challenging to achieve a metastable oversaturation necessary for precipitation hardening. This may be especially problematic in larger components.
Laser powder bed fusion has become one of the major techniques within metal additive manufacturing, especially when delicate structures and high geometric accuracy are concerned. Lately, the awareness of the material-specific macroscopic anisotropy has risen and led to widespread investigations on the static mechanical strength. However, little is known about the fracture behavior of the layer-wise fabricated metal components and their affinity of crack propagation between consecutive layers, which is particularly important for aluminium–silicon alloys containing embrittled zones in double-irradiated areas. A recent study indicated that there is a significant drop in fracture toughness in case the crack growth direction is parallel to the layering. To investigate this matter further and to shed light on the fracture toughness behavior in the range of a 0°–45° angle offset between the crack growth direction relative to the layering, notched samples with varying polar angles were subjected to mode I fracture toughness testing. Our results indicate that the fracture toughness is an almost-stable characteristic up to a mismatch of about 20° between the crack propagation path and the layering, at which point the fracture toughness decreases by up to 10%.