20005 research outputs found
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Novel lightweight design of additively manufactured structural components through biomimetics
No full textPBF-LB/M offers efficient production of complex and functional metal components. Research shows that the mechanical performance of components can be enhanced by incorporating biomimetic shapes, such as banana pseudo stem-inspired biomimetic beams. This work addresses three mechanical topology optimization problems, using AlSi10Mg. Leveraging these models, novel component designs featuring biomimetic beams and novel node designs were developed based on the input topology optimization. The new biomimetic component designs were compared to their topology optimization counterparts that were used as references. Numerical analyses of mass and structural integrity were performed to evaluate improvements. Lightweight biomimetic component designs for additively manufactured components were developed using the developed methods. Weight savings of 12.5-30.3 % were achieved compared to the input topology optimization results. However, further research on the design methodologies is needed to ensure that the mechanical stress criterion is also met within the nodes of the generated biomimetic designs
Hybrid biological hydrogel provides favorable bioenergetic, adhesive, and antioxidative effects on wound healing
No full textWound healing is a dynamic and complex process that demands substantial energy expenditure and a biomimetic microenvironment. Developing a simple and effective biological hydrogel to enhance mitochondrial energy metabolism could effectively promote wound healing. To this end, we developed a hybrid biological hydrogel based on Escherichia coli lipoate protein ligase A (LplA), which combines its catalytic and self-assembling properties to promote wound healing. In murine fibroblast L929 cell models, LplA significantly enhances cellular activity and intracellular metabolism, promoting cell proliferation and energy supply. However, cells aggregated into spherical clusters on the pure LplA hydrogel. To address this issue, we integrated glutaraldehyde (GA) as a cross-linker into the LplA hydrogel. The GA-LplA hydrogel enhances cell adhesion and proliferation and, unexpectedly, exhibits higher catalytic activity compared with the pure LplA hydrogel. Furthermore, LplA was observed to decompose H2O2, and the GA-LplA hybrid hydrogel significantly reduced reactive oxygen species (ROS) production. The promise of this hybrid hydrogel is successfully demonstrated in a male mice full-thickness skin defect model with accelerated re-epithelialization and cell proliferation while reducing inflammation
Hot double sided incremental forming of continuous fiber reinforced thermoplastics: Process analysis and system design
No full textInterest in fiber reinforced thermoplastics (FRTP) is increasing due to their superior recyclability and processability over thermoset composites, but the need for part-specific tooling constrains their application in small-lot production. Incremental sheet forming (ISF) presents a flexible manufacturing alternative. However, existing ISF methods, predominantly developed for metals, need to be adapted to the specific process requirements of FRTP. Prior research into the ISF of FRTP has focused on single-point incremental forming (SPIF). To enable new processing strategies, this work presents the development of a robot-based hot double sided incremental forming (DSIF) setup for FRTP. A process analysis serves as the basis of the design and integration of the core system components. The setup shows great potential as a platform to explore a wide range of new ways to advance the ISF of FRTP
Round-robin study on the determination of weld geometry parameters—part B: analysis of welded specimen
No full textThe local geometry of the weld toe or the weld seam has a high influence on the fatigue strength of welded joints. Two main parameters for the geometrical description of the weld toe are the weld toe radius and the weld toe angle. Currently, there is no uniform definition or standardized measurement approach for the assessment of these parameters. For this reason, the presented extensive round-robin (RR) study focusses on the influence of different evaluation techniques and measurement systems regarding the mentioned parameters based on 3D surface scans. In total, 20 participants take part in this two stage RR (19 participants in the second part). In this work, the results of the second part (part B) of the RR, namely the evaluation of weld toe radius and weld toe angle on real welded joints, are presented, where the actual weld toe geometry is not known a priori. For this, 22 data sets were evaluated. The data sets consist of measured values for the radius and angle of the weld toe in relation to the position along the weld seam. In general, significant variations are determined for the evaluated weld geometry parameters, especially for the weld toe radius. It is also shown that the condition of the weld toe transition has a high influence on the parameter. Particularly for weld seams with a low weld toe angle, the measurement results for the radius of the individual participants show high variations. For small weld toe radii, the results are quite comparable between the participants. The results for the weld toe angle are comparable for flat welds, but a wide range of results is observed for sharp weld toes. The degree of automation of the measurement method also has a high influence on the results. The most accurate results are expected from manual measurements, while the fully automatic and semi-automatic methods show larger deviations
Distributed event-triggered attitude estimation without angular velocity measurements
No full textIn this paper, a distributed event-triggered attitude estimation problem is considered for multiple rigid body systems on SO(3). The error in attitude estimation converges asymptotically to a common orientation among multiple rigid body systems, based on relative attitude measurements under undirected graphs. To eliminate the reliance on direct angular velocity measurements, a cascaded estimation scheme is proposed, employing indirected angular velocity estimation through a single vector measurement that is readily accessible using accelerometers or magnetometers. An event-triggered condition (ETC), grounded in clock variables, is proposed to reduce the communication and computation requirements associated with the attitude estimation. Subsequently, a rigorous convergence analysis of the attitude estimation errors is conducted, relying upon a stability criteria of invariant sets for cascade-connected systems. Furthermore, a self-triggered condition is developed to overcome the challenge of continuous monitoring throughout the event detection process. Ultimately, the efficacy of the proposed framework is validated through a numerical simulation encompassing multiple small satellites
Analysis of DC–DC converters as critical components for maritime DC grid simulation
No full textThe level of simulation detail accounts for system stability and dynamic response performance and is key to optimize between simulation accuracy and complexity. This study investigate its impact in shipboard DC grids focusing on power electronic converters as a critical component. A DC–DC forward converter model was analyzed with varying levels of complexity incorporating parasitic elements and compared to empirical data recorded at 100 kHz from a real DC–DC converter. The comparison was made regarding their time domain response to a load steps and their frequency domain characteristics. Results indicate that key characteristics like settling time and steady-state behavior can be accurately represented at moderate complexity, whereas capturing full system dynamics in time as well as frequency domain requires coupled hardware and digital simulations (Hardware-in-the-loop - HiL) due to component intricacies and parameter uncertainties
DuRTL - information flow analysis tool for register transfer level hardware designs
No full textIn this tool paper, we present a design information flow analysis tool called DuRTL. DuRTL is an open-source hardware information flow analysis tool implemented in C++ that helps designers understand and comprehend unknown hardware designs written in Verilog and VHDL. DuRTL implements an approach for Hardware Information Flow Tracking based on a tagging mechanism where unique tags are injected into a hardware design. Each tag is associated with a signal at a specific time and identifies a flow of information during the traversal of the circuit. We explain the methodology and IFT implementation of DuRTL and some of the design choices made during the development. We also present some experiments that show the capabilities of DuRTL
Optimizing mechanical pretreatment of cotton textile waste to enhance enzymatic hydrolysis
No full textEnzymatic recycling processes of cotton from waste materials have gained increasing interest in recent years. Therefore, the aim of this study was to optimize the application of mechanical shear forces to end-of-life cotton-based textile suspensions, followed by an enzymatic hydrolysis to glucose. Mechanical pretreatment in a cutting mill followed by a wet-rotor-milling process was investigated by varying solids load and mill parameter settings. The results indicated that both a smaller gap width and higher solids load during mechanical pretreatment resulted in enhanced enzymatic hydrolysis. Additionally, it was found that a minimum amount of energy input while milling was necessary to enable a higher glucose yield. The relationship between energy input, enzymatic hydrolysis, and crystallinity facilitates the assessment of the effect of energy input within the milling process. Furthermore, a decrease in enzyme activity was observed with increasing solids load during enzymatic hydrolysis. Overall, the findings of this research suggest that wet milling presents a promising technology to improve the enzymatic hydrolysis of end-of-life cotton textiles
Micro- and nanostructural investigations of high and ultra-high performance concrete under fatigue
No full textA fine-grained UHPC, both undamaged and damaged by fatigue loading, was comparatively examined by various microstructural analytical methods, to evaluate the different techniques with respect to their applicability and relevance for the investigation of fatigue damage processes. The fatigue tests were stopped at the transition from phase II to phase III of the s-shaped strain development. The cyclic compression loading was performed with a frequency of ft = 1 Hz, and a stress level between Smin = 0.05 and Smax = 0.75 (fcm = 170.2 MPa). The fatigue process under these loading conditions is dominated by alterations and damages on the nano-scale, that can be observed by transmission electron microscopy. The resulting coarsening of the pore structure was also visible with dynamic vapor sorption. Nanoindentation indicates, that changes of the HD-C-S-H-phase occur. IR spectroscopy also indicates changes of the C-S-H phase and thermal analysis changes of the water content. Dynamic mechanical analysis (DMA) gave insight into the complex Young's modulus and Poisson's ratio changes. The acoustic emission technique gives information on the different processes during the single phases of fatigue and reveal a very different damage behaviour of dry and moist materials. Some microcracks are visible with light microscopy. It appears, that the number of cracks after fatigue is higher than before. With X-ray computed tomography, X-ray powder diffraction, the drying behaviour, the free water uptake, the water uptake under vacuum and by mercury intrusion porosimetry no significant differences between specimens with and without fatigue loading could be observed in this examination