Friday, February 26th, 2016

Christine Buffinton – Buffinton, Christine; Buffinton, Elise M.; Bieryla, Kathleen; and Pratt, Jerry E. “Biomechanics of Step Initiation After Balance Recovery With Implications for Humanoid Robot Locomotion.” Journal of Biomechanical Engineering 138, no. 3 (2016 ).

Christine Buffinton, Assistant Professor of Mechanical Engineering

Buffinton, Christine; Buffinton, Elise M.; Bieryla, Kathleen; and Pratt, Jerry E. “Biomechanics of Step Initiation After Balance Recovery With Implications for Humanoid Robot Locomotion.” Journal of Biomechanical Engineering 138, no. 3 (2016 ).

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Friday, February 26th, 2016

Christine Buffinton – Buffinton, Christine; Tong, Kelly J.; Blaho, Roberta A.; Buffinton, Elise M.; and Ebenstein, Donna M. “Comparison of Mechanical Testing Methods for Biomaterials: Pipette Aspiration, Nanoindentation, and Macroscale Testing.” Journal of the Mechanical Behavior of Biomedical Materials 51, (2015) : 367-379.

Christine Buffinton, Assistant Professor of Mechanical Engineering

Characterization of the mechanical properties of biological materials is often complicated by small volume, irregular geometry, fragility, and environmental sensitivity. Pipette aspiration and nanoindentation testing deal well with these limitations and have seen increasing use in biomaterial characterization, but little research has been done to systematically validate these techniques for soft materials. This study compared the results of pipette aspiration, nanoindentation, and bulk uniaxial tension and compression in determining the small-strain elastic moduli of a range of biomedically-relevant materials, a series of silicone elastomers and polyacrylamide hydrogels. A custom apparatus was developed for pipette aspiration testing, a commercial Hysitron instrument with custom spherical tip was used for nanoindentation, and standard commercial machines were used for tension and compression testing. The measured small-strain elastic moduli ranged from 27 to 368kPa for the silicones and 11 to 44kPa for the polyacrylamide gels. All methods detected expected trends in material stiffness, except for the results from one inconsistent silicone. Pipette aspiration and nanoindentation measured similar elastic moduli for silicone materials, but pipette aspiration measured consistently larger stiffness in the hydrogels, which may be explained by the gels׳ resistance to tension. Despite the difference in size scale among the testing methods, size does not appear to influence the results. These results suggest that both pipette aspiration and nanoindentation are suitable for measuring mechanical properties of soft biomaterials and appear to have no more limitations than bulk techniques.

Copyright 2015 Elsevier Ltd. All rights reserved.

Buffinton, Christine; Tong, Kelly J.; Blaho, Roberta A.; Buffinton, Elise M.; and Ebenstein, Donna M. “Comparison of Mechanical Testing Methods for Biomaterials: Pipette Aspiration, Nanoindentation, and Macroscale Testing.” Journal of the Mechanical Behavior of Biomedical Materials 51, (2015) : 367-379.

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Friday, February 26th, 2016

Christine Buffinton – Bieryla, Katie and Buffinton, Christine. “Effects of Age and Step Length on Joint Kinetics During Stepping Task.” Journal of Biomechanics 48, no. 10 (2015) : 1679-1686.

Christine Buffinton, Assistant Professor of Mechanical Engineering

Following a balance perturbation, a stepping response is commonly used to regain support, and the distance of the recovery step can vary. To date, no other studies have examined joint kinetics in young and old adults during increasing step distances, when participants are required to bring their rear foot forward. Therefore, the purpose of this study was to examine age-related differences in joint kinetics with increasing step distance. Twenty young and 20 old adults completed the study. Participants completed a step starting from double support, at an initial distance equal to the individual’s average step length. The distance was increased by 10% body height until an unsuccessful attempt. A one-way, repeated measures ANOVA was used to determine the effects of age on joint kinetics during the maximum step distance. A two-way, repeated measures, mixed model ANOVA was used to determine the effects of age, step distance, and their interaction on joint kinetics during the first three step distances for all participants. Young adults completed a significantly longer step than old adults. During the maximum step, in general, kinetic measures were greater in the young than in the old. As step distance increased, all but one kinetic measure increased for both young and old adults. This study has shown the ability to discriminate between young and old adults, and could potentially be used in the future to distinguish between fallers and non-fallers.

Copyright 2015 Elsevier Ltd. All rights reserved.

Bieryla, Katie and Buffinton, Christine. “Effects of Age and Step Length on Joint Kinetics During Stepping Task.” Journal of Biomechanics 48, no. 10 (2015) : 1679-1686.

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Friday, February 26th, 2016

Charles Kim – Krishnan, Girish; Bishop-Moser, Joshua; Kim, Charles; and Kota, Sridhar. “Kinematics of a Generalized Class of Pneumatic Artificial Muscles.” Journal of Mechanisms and Robotics–Transactions of the ASME 7, no. 4 (2015) : 041014.

Charles Kim, Associate Professor of Mechanical Engineering

Fluid filled fiber reinforced elastomeric enclosures (FREEs) have been a popular choice for actuators in prosthetics and soft robots owing to their high power density and cost effective manufacturing. While a narrow class of FREEs known as McKibben’s actuators have been extensively studied, there is a wide unexplored class that could be potentially used as actuators and soft structural members. This paper analyzes the mobility of generalized FREEs based on simple geometric relationships that result from the inextensibility of fibers and fluidic actuation. The analysis conducted can be classified into instantaneous kinematics and global or large deformation kinematics. Instantaneous kinematics reveals that the most general deformation pattern of the FREE is a screw motion about the axis of its cylinder, whose pitch is a function of fiber orientations. Furthermore, a set of fiber angles, which do not deform under volumetric actuation were identified as the locked manifold (LM). Global kinematic analysis revealed that every FREE continued to deform until its fiber configuration approached the LM. These insights were corroborated with finite element analysis (FEA) and testing for a small sample of FREE actuators.

Krishnan, Girish; Bishop-Moser, Joshua; Kim, Charles; and Kota, Sridhar. “Kinematics of a Generalized Class of Pneumatic Artificial Muscles.” Journal of Mechanisms and Robotics–Transactions of the ASME 7, no. 4 (2015) : 041014.

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Friday, February 26th, 2016

Mala M. Sharma – Sharma, Mala M.; Tomedi, Josh D.; and Parks, Jeffrey M. “A Microscopic Study on the Corrosion Fatigue of Ultra-Fine Grained and Conventional Al-Mg Alloy.” Corrosion Science 93 (2015): 180-190.

Mala M. Sharma, Associate Professor of Mechanical Engineering

The corrosion behavior of a nanocrystalline (NC)/ultrafine grained (UFG) Al–Mg based alloy was investigated and compared to its conventional counterpart 5083(H111). The corrosion fatigue (CF) was studied with respect to pit initiation, pit location and crack propagation as a function of environment. Scanning electron microscopy (SEM) with EDS was used to analyze the fracture surface of the failed specimen with respect to pitting characteristics, crack propagation and corrosion product. Load vs. cycles to failure was measured and S/N curves were generated for the UFG Al–Mg based alloy and the conventional counterpart 5083 in air and seawater.

Sharma, Mala M.; Tomedi, Josh D.; and Parks, Jeffrey M. “A Microscopic Study on the Corrosion Fatigue of Ultra-Fine Grained and Conventional Al-Mg Alloy.” Corrosion Science 93 (2015): 180-190.

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Friday, February 26th, 2016

Mala M. Sharma – Sharma, Mala M.; Eden, Timothy; and Golesich, Brock T. “Effect of Surface Preparation on the Microstructure, Adhesion, and Tensile Properties of Cold-Sprayed Aluminum Coatings on AA2024 Substrates.” Journal of Thermal Spray Technology 23, no. 3 (2015): 410-422.

Mala M. Sharma, Associate Professor of Mechanical Engineering

Commercially pure aluminum coatings (CP-Al) were applied to AA 2024-T351 substrates utilizing the cold spray process using different surface preparation methods and carrier gases; the resulting microstructures and mechanical properties were investigated. Substrate preparation methods were examined to understand the effect of substrate roughness on coating properties, to minimize embedded grit, and to identify the surface preparation method that yielded the best combination of coating properties. Three substrate roughing preparations, glass bead, SiC grit, and alumina grit blast, were examined while utilizing both helium and nitrogen as carrier gases in the cold spray process. Coatings that were oxide free, possessing densities greater than 99% were achieved, with the mean coating porosity ranging 0.1-0.5%. The highest mean adhesion strength was 42 MPa for the nitrogen gas and 20 MPa for the helium gas, both using glass bead surface preparation. For the nitrogen process gas samples, the surface preparation methods that produced high pull strengths correlated to bend test specimens that showed no signs of cracking on surfaces or edges. The overall best combination of mechanical property results was achieved with coatings prepared by glass bead surface roughening using nitrogen as a carrier gas.

Sharma, Mala M.; Eden, Timothy; and Golesich, Brock T. “Effect of Surface Preparation on the Microstructure, Adhesion, and Tensile Properties of Cold-Sprayed Aluminum Coatings on AA2024 Substrates.” Journal of Thermal Spray Technology 23, no. 3 (2015): 410-422.

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Friday, February 26th, 2016

Nathan P. Siegel – Siegel, Nathan P.; Gross, Michael D.; and Coury, Robert. “The Development of Direct Absorption and Storage Media for Falling Particle Solar Central Receivers.” ASME Journal of Solar Energy Engineering 137, no. 4 (2015).

Nathan P. Siegel, Assistant Professor of Mechanical Engineering

Spherical sintered bauxite particles between 200 μm and 700 μm in diameter have been shown to be effective in the direct absorption and storage of concentrated solar energy. These particles are commercially available in large quantities and exhibit as-received solar weighted absorptance (αs) greater than 0.90, which gradually degrades with extended heating in air at 700 °C and above. The degradation mechanism is an oxidation reaction that can be reversed via thermal or chemical reduction, resulting in αs > 0.95 along with enhanced resistance to further degradation for some formulations. Certain metal oxide pigments, added to Al2O3:SiO2, have proven to achieve solar weighted absorptance levels similar to those of the commercially available particles and may be promising alternatives to currently available materials.

Siegel, Nathan P.; Gross, Michael D.; and Coury, Robert. “The Development of Direct Absorption and Storage Media for Falling Particle Solar Central Receivers.” ASME Journal of Solar Energy Engineering 137, no. 4 (2015).

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Friday, February 26th, 2016

Constance W. Ziemian – Ziemian, Sophia; Okwara, Maryvivian; and Ziemian, Constance W. “Tensile and Fatigue Behavior of Layered Acrylonitrile Butadiene Styrene.” Rapid Prototyping Journal 21, no. 3 (2015) : 270-278.

Constance W. Ziemian, Professor of Mechanical Engineering

Purpose – This paper aims to define the effect of specimen mesostructure on the monotonic tensile behavior and tensile-fatigue life of layered acrylonitrile butadiene styrene (ABS) components fabricated by fused deposition modeling (FDM).

Design/methodology/approach – Tensile tests were performed on FDM dogbone specimens with four different raster orientations according to ASTM standard D638-03. Resulting ultimate tensile stresses (UTS) for each raster orientation were used to compute the maximum stress for fatigue testing, i.e. 90, 75, 60 and 50 or 45 per cent nominal values of the UTS. Multiple specimens were subjected to tension – tension fatigue cycling with stress ratio of R = 0.10 in accordance with ASTM standard D7791-12.

Findings – Both tensile strength and fatigue performance exhibited anisotropic behavior. The longitudinal (0 degrees) and default (+45/-45 degrees) raster orientations performed significantly better than the diagonal (45 degrees) or transverse (90 degrees) orientations in regards to fatigue life, as displayed in the resulting Wohler curves.

Practical implications – Raster orientation has a significant effect on the fatigue performance of FDM ABS components. Aligning FDM fibers along the axis of the applied stress provides improved fatigue life. If the direction of applied stresses is not expected to be constant in given application, the default raster orientation is recommended.

Originality/value – This project provides knowledge to the limited work published on the fatigue performance of FDM ABS components. It provides S-N fatigue life results that can serve as a foundation for future work, combining experimental investigations with theoretical principles and the statistical analysis of data.

Ziemian, Sophia; Okwara, Maryvivian; and Ziemian, Constance W. “Tensile and Fatigue Behavior of Layered Acrylonitrile Butadiene Styrene.” Rapid Prototyping Journal 21, no. 3 (2015) : 270-278.

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