| NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
| Recipient: |
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| Initial Amendment Date: | July 6, 2016 |
| Latest Amendment Date: | March 27, 2017 |
| Award Number: | 1649111 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Siddiq Qidwai
sqidwai@nsf.gov (703)292-2211 CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
| Start Date: | September 1, 2016 |
| End Date: | February 28, 2019 (Estimated) |
| Total Intended Award Amount: | $150,000.00 |
| Total Awarded Amount to Date: | $166,000.00 |
| Funds Obligated to Date: |
FY 2017 = $16,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
520 LEE ENTRANCE STE 211 AMHERST NY US 14228-2577 (716)645-2634 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
240 Ketter Hall Buffalo NY US 14260-4300 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Mechanics of Materials and Str |
| Primary Program Source: |
01001718DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
This EArly-concept Grant for Exploratory Research (EAGER) award supports fundamental research to provide knowledge for a pattern-transformable granular phononic crystal, which may have tunable low-frequency band-gaps. Phononic band-gap materials are composite materials characterized by phononic band-gaps, i.e., frequency ranges in which the propagation of mechanical waves is prohibited. Phononic band-gap materials made of conventional structural materials possess typically fixed narrow phononic band-gaps in some high-frequency ranges. However, unwanted vibrations and noises disturbing human body are characterized by broadband frequency contents in rather low-frequency ranges. Thus, due to this knowledge gap, their practical products has not appeared yet. This new research will open the possibility of practical phononic band-gap materials. Therefore, if this project succeeds, results from this research will benefit the U.S. manufacturing industry. Furthermore, the PI will design hands-on activities relating to pattern transformations for diverse audiences including under-represented minorities and female students. With these activities, the goal is to stimulate students to pursue a career in engineering.
The objective of this project is to explore the proof-of-concept of a pattern-transformable two-dimensional granular crystals, which is characterized by its low-frequency tunable phononic band-gaps. The objective is based on the central hypothesis that instability is closely relating to the pattern-transformation-induced bandgap tunability. The hypothesis will be demonstrated by performing the following specific tasks: (1) identification of pattern transform mechanism, (2) experimental validation of the identified mechanism, (3) numerical phononic dispersion relations, and (4) experimental validation of the numerical phononic dispersion relations. The research attempts to take a transformative approach that links conventional instability theory to an uncharted area of granular phononic crystals. Instability phenomenon is nearly length-scale independent. Therefore, the successful completion of this research could have a significant impact in the field of phononic band-gap materials, because the instability-induced mechanism can be adopted for the design of tunable granular phononic crystals using various actuations in a wide range of length scales.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The main objective of this EAGER project was to explore the proof-of-concept of a pattern-transformable 2-D granular phononic crystal (GPC), which is characterized by its low-frequency tunable phononic band-gap. Here, phononic band gaps can be viewed as low transmission zones in frequency response functions).
To investigate pattern-transformable 2-D GPCs, we completed both quasi-static analysis and phononic band-structure analysis. During the quasi-static investigation, we performed numerical pattern-transformation analysis of four 2-D GPCs using periodic boundary conditions as well as finite size specimens, and then experimentally validated the identified pattern-transformation. After the quasi-static investigation, we calculated the phononic dispersion relations of the GPCs using discrete element method (DEM), where the motion of soft granular particles are simplified by using discrete masses and non-linear springs. Furthermore, we also calculated phononic dispersion relation of the GPCs using finite element method (FEM), by which the nonlinear behavior of soft granular particles are accurately modeled. In addition, we constructed an experimental setup to observe the wave propagation characteristics of the considered 2-D GPCs, and performed a series of dynamic experiments to identify the evolution of the frequency response function of the considered 2-D GPCs upon compression.
From the completed activities, we have identified a new class of diatomic 2-D soft granular crystals, which features pattern transformation under compression with lateral confinement. The proposed granular crystals are composed of two different types of cylinders: large soft cylinders and small hard cylinders. The pattern-transformable granular crystals are obtained by exploring perturbed packing patterns as potential configurations, and compression with lateral confinement as the driving force of the transition. The conducted research was original because the mechanism of pattern transformations in granular crystals has never been investigated, and we took a transformative approach that links conventional theory (i.e., compact packing theory) to an uncharted area of granular crystals (i.e., pattern transformations in granular crystals and their application to tunable GPCs). The scale-independent compact packing theory serves as an underlying mechanism of the observed pattern transformations of granular crystals, so the proposed granular crystals can open new avenues in the microstructural design of functional materials towards practical applications.
While studying the numerical aspect of the identified GPCs, we found the critical limitation of discrete element method for band-structure analysis. Due to the computational efficiency of the discrete element method (DEM), DEM has been more commonly adopted to study the nonlinear behavior of soft granular crystals than the finite element method (FEM). Our study confirms that DEM is effective to study quasi-static mechanical properties of granular crystals. However, it also reveals that DEM results on the dispersion relations of the considered granular crystal are substantially different from the corresponding FEM results. The lack of decoupled rotational stiffness in the conventional DEM contact force model induces the wide discrepancy in the phononic dispersion relation. The coupling of shear and rotation in the adopted DEM contact model prevents shear motion from independently appearing without activating rotation, consequently resulting in a substantial discrepancy in the overall phononic dispersion relation. This study provides that special care should be given to interpreting the results of phononic band-structure obtained by DEM.
While working on this project, we trained two talented undergraduate students. One student was trained to use CAD software and designed the fixture of a biaxial loading frame. The other student learned to operate the data acquisition system and deployed a biaxial loading frame for pattern transformation. During this project period, we made three presentations at international conferences. In addition, we published one journal paper, and submitted another manuscript for journal publication.
Last Modified: 06/14/2019
Modified by: Jongmin Shim
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