ABSTRACT
Advancements in additive manufacturing (AM) technology are promising for the creation of acoustic materials. Acoustic metamaterials and metasurfaces are of particular interest for the application of AM technologies as theoretical predictions suggest the need for precise arrangements of dissimilar materials within specified regions of space to reflect, transmit, guide, or absorb acoustic waves in ways that exceed the capabilities of currently available acoustic materials. This work presents the design of an acoustic metasurface (AMS) with Willis constitutive behavior, which is created from an array of multi-material inclusions embedded in an elastomeric matrix, which displays the asymmetric acoustic absorption. The finite element models of the AMS show that the asymmetric absorption is dependent on asymmetry in the distribution of materials within the inclusion and highly sensitive to small changes in the inclusion geometry. It is shown that the performance variability can be used to place constraints on the manufacturing-induced variability to ensure that an as-built AMS will perform using the as-designed parameters. The evaluation of the AMS performance is computationally expensive, thus, the design is performed with a classifier-based metamodel to support more efficient Monte Carlo simulations and quantify the sensitivity of the candidate design performance to the manufacturing variability. This work explores combinations of material choices and dimensional accuracies to demonstrate how a robust design approach can be used to help select AM fabrication methods or guide process development toward an AM process that is capable of fabricating acoustic material structures.
ABSTRACT
Multiple metrics have been proposed to measure the creativity of products, yet there is still a need for effective, reliable methods to assess the originality of new product designs. In the present article we introduce a method to assess the originality of concepts that are produced during idea generation activities within engineering design. This originality scoring method uses a decision tree that is centered around distinguishing design innovations at the system level. We describe the history and the development of our originality scoring method, and provide evidence of its reliability and validity. A full protocol is provided, including training procedures for coders and multiple examples of coded concepts that received different originality scores. We summarize data from over 500 concepts for garbage collection systems that were scored by Kershaw et al. (2015). We then show how the originality scoring method can be applied to a different design problem. Our originality scoring method, the Decision Tree for Originality Assessment in Design (DTOAD), has been a useful tool to identify differences in originality between various cohorts of Mechanical Engineering students. The DTOAD reveals cross-sectional differences in creativity between beginning and advanced students, and shows longitudinal growth in creativity from the beginning to the end of the undergraduate career, thus showing how creativity can be influenced by the curriculum. The DTOAD can be applied to concepts produced using different ideation procedures, including concepts produced both with and without a baseline example product, and concepts produced when individuals are primed to think of different users for their designs. Finally, we show how our the DTOAD compares to other measurements of creativity, such as novelty, fixation, and remoteness of association.
