This paper explores the influences that potential variances in material properties and nominal dimensions have on the overall mechanical behavior of an additively manufactured meta-material. The investigation looks at deviations between expected and experimental mechanical responses obtained through performance validation testing. Three sources for discrepancies were identified through literature review and model/experimental comparison. Sensitivity analyses were employed to obtain the significance of the design parameters, and preliminary work in boundary condition improvements is discussed.
Topology optimization of periodic metamaterials for structural applications usually results in uniformly distributed cells. This paper presents a novel concept designed to better tailor unit cell-based meta-material designs for nonlinear structural applications. First, previous work in the development of a systematic method for the construction and optimization of these advanced materials is reviewed. Results of a previous case study for the design of meta-material backer pads for the wheels of the Abrams tank are presented to provide a platform for the introduction of layer specific dimensional multipliers, dubbed “size factors”. These add an additional layer of complexity for the previously designed homogeneous materials. The methodology behind the size factors is presented and the implementation of the “size factors”, as it pertains to the meta-materials designed using the Modified Unit Cell Synthesis method, is then discussed. Initial assumptions for a final size factor arrangement are presented, prompting the creation of two optimization procedures to compare against one another. Results for both optimizations are obtained and while both show an increase in nonlinearity over the original material, the unorganized arrangement of the parameters results in the most optimal designs, with near zero error between the target and obtained non-linear force-strain relationships.
R6sum6.-La friction interne de l'alliage Fer-24 % Nickel a ete Ctudike dans un domaine de tempkratures de 200 a 1 100 oC, en montke et descente de tempkrature, a une frequence d'oscillation de 1 Hz. Le spectre de friction interne consiste en cinq pics ayant lieu B. 146O, 4620, 5190, 670° et 779 O C durant la montee en temperature, et de deux pics A 7840 et 144 O C durant le refroidissement. Le pic a 460 O C semble 6tre un pic de joint de grains caus6 par les atomes de fer ou de nickel diffusant a travers l'interface de martensite-austknite. Les pics B 5190 et 144 O C semblent Ctre causks par la transformation martensitique. Le pic a 670 O C serait connect6 avec la recristallisation du metal aprks la transformation austenitique. Les pics 779 et 784 O C peuvent 6tre causds par des relaxations de joint de grains en phase austenitique.
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