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Dirk Lehmhus published an article in August 2017.
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(2002 - 2017)
(2002 - 2017)
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Article 0 Reads 2 Citations From Stochastic Foam to Designed Structure: Balancing Cost and Performance of Cellular Metals Published: 08 August 2017
Materials, doi: 10.3390/ma10080922
Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason for this sluggish uptake is their high cost. Many cellular metals require expensive raw materials, complex manufacturing procedures, or a combination thereof. Some attempts have been made to decrease costs by introducing novel foams based on cheaper components and new manufacturing procedures. However, this has often yielded materials with unreliable properties that inhibit utilization of their full potential. The resulting balance between cost and performance of cellular metals is probed in this editorial, which attempts to consider cost not in absolute figures, but in relation to performance. To approach such a distinction, an alternative classification of cellular metals is suggested which centers on structural aspects and the effort of realizing them. The range thus covered extends from fully stochastic foams to cellular structures designed-to-purpose.
Article 1 Read 0 Citations Effect of Fly-Ash Cenospheres on Properties of Clay-Ceramic Syntactic Foams Published: 19 July 2017
Materials, doi: 10.3390/ma10070828
A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, reference samples without cenospheres were produced for property comparison. The materials comprising different amount of the additives were fired at temperatures of 600, 950, 1000, 1050, 1100, 1150 and 1200 °C. Firing times were kept constant at 30 min. Processing characteristics of the materials were evaluated in terms of density achieved and shrinkage observed as functions of both the CS content and the sintering temperature. The compressive strength and water uptake were determined as application-oriented properties. Except for the reference and the low CS level samples, the materials show an increase in strength with the increase in firing temperature, and a decrease of mechanical reliability with a decrease in density, which is typical for porous materials. Exceptions are the samples with no or low (10 vol %) content of cenospheres. In this case, the maximum strength is obtained at an intermediate sintering temperature of 1100 °C. At a low density (1.10 and 1.25 g/cm3), the highest levels of strength are obtained after sintering at 1200 °C. For nominal porosity levels of 50 and 60 vol %, 41 and 26 MPa peak stresses, respectively, are recorded under compressive load.
Article 2 Reads 1 Citation Mechanical Behavior of Particulate Aluminium-Epoxy Hybrid Foams Based on Cold-Setting Polymers Published: 08 May 2017
Advanced Engineering Materials, doi: 10.1002/adem.201700090
New types of hybrid foams with cold-setting polymer foam matrix have been developed. These are based on AlSi10 foam granules and a cold-setting epoxy polymer foam phase. The mechanical characteristics of the hybrid foams like stiffness, compressive, and tensile strength were determined using quasi-static compression and tensile tests. Their overall mechanical behavior is compared to APM-(Advanced Pore Morphology)-based hybrid foams comprising similar aluminium foam granules in combination with single component hot setting epoxy foams. While the latter generally outperform the cold-setting variants at their present state of development, the ease of manufacturing in conjunction with promising levels of strength, and stiffness will support future application of the new material.
Article 1 Read 5 Citations Vibration-Assisted Sputter Coating of Cenospheres: A New Approach for Realizing Cu-Based Metal Matrix Syntactic Foams Published: 07 January 2017
Metals, doi: 10.3390/met7010016
Article 1 Read 2 Citations Data Evaluation in Smart Sensor Networks Using Inverse Methods and Artificial Intelligence (AI): Towards Real-Time Capab... Published: 01 October 2016
Advances in Science and Technology, doi: 10.4028/www.scientific.net/ast.101.55
Data evaluation is crucial for gaining information from sensor networks. Main challenges include processing speed and adaptivity to system change, both prerequisites for SHM-based weight reduction via relaxed safety factors. Our study looks at soft real time solutions providing feedback within defined but flexible, application-controlled intervals. These can rely on minimizing computation/communication latencies e.g. by parallel computation. Strategies towards this aim can be model-based, including inverse FEM, or model-free, including machine learning, which in practice bases training on a defined system state, too, hence also facing challenges at state changes. We thus introduce hybrid data evaluation combining multi-agent based systems (MAS) with inverse FEM, mainly relying on matrix operations that can be partially distributed: The MAS perform sensor data acquisition, aggregation, pre-computation, and finally application (the LM/SHM itself and higher information processing and visualization layers, i.e., WEB interfaces). System capabilities are evaluated against a virtual test case, demonstrating enhanced stability and reliability. Besides, we analyze system performance under conditions of in-service change and discuss system layouts suited to improve coverage of this issue.
Article 1 Read 5 Citations Customized Smartness: A Survey on Links between Additive Manufacturing and Sensor Integration Published: 01 January 2016
Procedia Technology, doi: 10.1016/j.protcy.2016.08.038