Hubbard and Wissa Collaborators on ASME Best Paper in Structures

Aerospace Engineering Professor James E. Hubbard, Jr. and alumna Aimy Wissa (Ph.D., 14) were collaborators on the winning paper for the 2015 Best Paper in Structures Award from the Adaptive Structures and Material Systems (ASMS) branch of the Aerospace Division of the American Society of Mechanical Engineers (ASME).

The paper, "Design and Optimization of a Contact-Aided Compliant Mechanism for Passive Bending," stemmed from a collaboration with Pennsylvania State University colleagues, Ph.D. student Yashwanth Tummala and Professor of Mechanical Engineering Mary Frecker.

The research aimed at designing and optimizing a contact-aided compliant mechanism (CCM)—called a compliant spine (CS)—that is flexible in one direction, but stiff in the opposite. According to the paper, compliant mechanisms are both lighter, and easier and cheaper to fabricate over their rigid counterparts.

The goal of optimization was to minimize the peak stress and mass while maximizing the deflection, subject to geometric and other constraints. The researchers used flapping wing unmanned air vehicles— also known as ornithopters—as their case study vehicle to test the accuracy of the design optimization procedure and prove how well the compliant spine design worked.

Next, the team fabricated the optimal compliant spine designs, integrated them into the ornithopter's wing leading edge spar and performed flight tests. The flight test results demonstrated the ability of the compliant spine to produce an asymmetry in the ornithopter's wing kinematics during the up and down strokes.

Wissa was responsible for performing test flights of the ornithopters equipped with prototype compliant spines at the Air Force Research Lab (AFRL) Wright Patterson Air Force Base (WPAFB) indoor flight facility.

Hubbard is a Samuel P. Langley Distinguished Professor and director of both the University of Maryland's Morpheus Laboratory and the National Institute of Aerospace's Alex Brown Center for Adaptive Aerospace Research.

The award, presented by the American Society of Mechanical Engineers (ASME) Technical Committee, was announced during the International Society for Optics and Photonics (SPIE) Smart Structures/NDE Conference held March 8-12 in San Diego, Calif.

Published March 26, 2015