TY - JOUR A1 - Bohl, Stefan A1 - Kirchhof, Robert A1 - Koch, Stephan T1 - Einsatzmöglichkeiten von Mehrsystemfahrzeugen für einen umsteigefreien SPNV im Land Brandenburg KW - Schienenverkehr KW - Straßenbahn KW - Karlsruher Modell KW - Tram-Train KW - Schienenpersonennahverkehr, SPNV KW - Mehrsystemfahrzeuge KW - Mischbetrieb KW - umsteigefrei KW - Brandenburg KW - Diesel-Hybridantrieb KW - Potsdam KW - Beelitz Y1 - 2001 ER - TY - GEN A1 - Kirchhof, Stephan A1 - Ams, Alfons A1 - Hütter, Geralf T1 - On the Question of the Sign of Size Effects in the Elastic Behavior of Foams T2 - Journal of Elasticity N2 - Due to their good ratio of stiffness and strength to weight, foam materials find use in lightweight engineering. Though, in many applications like structural bending or tension, the scale separation between macroscopic structure and the foam’s mesostructure like cells size, is relatively weak and the mechanical properties of the foam appear to be size dependent. Positive as well as negative size effects have been observed for certain basic tests of foams, i.e., the material appears either to be more compliant or stiffer than would be expected from larger specimens. Performing tests with sufficiently small specimens is challenging as any disturbances from damage of cell walls during sample preparation or from loading devices must be avoided. Correspondingly, the number of respective data in literature is relatively low and the results are partly contradictory. In order to avoid the problems from sample preparation or bearings, the present study employs virtual tests with CT data of real medium-density ceramic foams. A number of samples of different size is “cut” from the resulting voxel data. Subsequently, the apparent elastic properties of each virtual sample are “measured” directly by a free vibrational analysis using finite cell method, thereby avoiding any disturbances from load application or bearings. The results exhibit a large scatter of the apparent moduli per sample size, but with a clear negative size effect in all investigated basic modes of deformation (bending, torsion, uniaxial). Finally, the results are compared qualitatively and quantitatively to available experimental data from literature, yielding common trends as well as open questions. KW - Foam KW - Cellular material KW - Elastic size effect KW - Bending KW - Torsion KW - Virtual testing Y1 - 2023 UR - https://link.springer.com/article/10.1007/s10659-023-10037-6 U6 - https://doi.org/10.1007/s10659-023-10037-6 SN - 1573-2681 ER -