Mary Frecker

William Penn University, Worcester, Massachusetts, United States

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Publications (118)78.05 Total impact

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    ABSTRACT: Unmanned Aerial Vehicles (UAVs) are proliferating in both the civil and military markets. Flapping wing UAVs, or ornithopters, have the potential to combine the agility and maneuverability of rotary wing aircraft with excellent performance in the low Reynolds number flight regimes. The purpose of this paper is to present new free flight experimental results for an ornithopter equipped with single degree of freedom compliant spines. The compliant spines are designed and optimized in terms of mass, maximum von-Mises stress, and desired wing bending deflections. The spines are inserted in an experimental ornithopter wing leading edge spar, in order to achieve a set of desired kinematics during the up and down strokes of a flapping cycle. The ornithopter is flown at Wright Patterson Air Force Base in the Air Force Research Laboratory Small Unmanned Air Systems (SUAS) indoor flight facility. Vicon (R) motion tracking cameras are used to track the motion of the vehicle for four different wing configurations. The effect of the presence of the compliant spine on the wings and body kinematics, as well as the leading edge spar deflection during free flight is presented in this paper. Several metrics were used to evaluate the vehicle performance with various compliant spine designs inserted in the leading edge spar of the wings. Results show that passively morphing the wings, via adding compliance in the leading edge spar, does not require additional power expenditure and is beneficial to the overall vertical and horizontal propulsive force production.
    03/2015; 7(1):21-40. DOI:10.1260/1756-8293.7.1.21
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    ABSTRACT: Origami engineering – the use of origami principles in engineering applications – provides numerous opportunities to revolutionize the way we design, manufacture, assemble, and package products and devices. By combining origami principles with active materials, we can create reconfigurable products and devices that can fold and unfold on demand. In origami, the folded medium is paper, yet many engineering applications require materials with finite thickness to provide the necessary strength and stiffness to achieve the desired functionality. In such applications, it is important to distinguish between bending and folding so that we understand the differences in material behavior when actuated. In this paper, we propose definitions for bending and folding for materials used in engineering applications. The literature is reviewed in detail to provide context and support for the proposed definitions, and examples from our own research with active materials, specifically, magneto-active elastomers (MAE) and dielectric elastomers (DE), are used to illustrate the subtle, yet important, differences between bending and folding in materials with finite thickness.
    International Design and Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE), Buffalo, New York; 08/2014
  • S Ahmed, Z Ounaies, M Frecker
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    ABSTRACT: Origami engineering aims to combine origami principles with advanced materials to yield active origami shapes, which fold and unfold in response to external stimuli. This paper explores the potential and limitations of dielectric elastomers (DEs) as the enabling material in active origami engineering. DEs are compliant materials in which the coupled electro-mechanical actuation takes advantage of their low modulus and high breakdown strength. Until recently, prestraining of relatively thick DE materials was necessary in order to achieve the high electric fields needed to trigger electrostatic actuation without inducing a dielectric breakdown. Although prestrain improves the breakdown strength of the DE films and reduces the voltage required for actuation, the need for a solid frame to retain the prestrain state is a limitation for the practical implementation of DEs, especially for active origami structures. However, the recent availability of thinner DE materials (50 μm, 130 μm, 260 μm) has made DEs a likely medium for active origami. In this work, the folding and unfolding of DE multilayered structures, along with the realization of origami-inspired 3D shapes, are explored. In addition, an exhaustive study on the fundamentals of DE actuation is done by directly investigating the thickness actuation mechanism and comparing their performance using different electrode types. Finally, changes in dielectric permittivity as a function of strain, electrode type and applied electric field are assessed and analyzed. These fundamental studies are key to obtaining more dramatic folding and to realizing active origami structures using DE materials.
    Smart Materials and Structures 08/2014; 23(9):094003. DOI:10.1088/0964-1726/23/9/094003 · 2.45 Impact Factor
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    ABSTRACT: The field of active origami explores the incorporation of active materials into origami-inspired structures in order to serve as a means of actuation. Active origami-inspired structures capable of folding into complex three-dimensional (3D) shapes have the potential to be lightweight and versatile compared to traditional methods of actuation. This paper details the finite element analysis and experimental validation of unimorph actuators. Actuators are fabricated by adhering layers of electroded dielectric elastomer (3M VHB F9473PC) onto a passive substrate layer (3M Magic Scotch Tape). Finite element analysis of the actuators simulates the electromechanical coupling of the dielectric elastomer under an applied voltage by applying pressures to the surfaces of the dielectric elastomer where the compliant electrode (conductive carbon grease) is present. 3D finite element analysis of the bending actuators shows that applying contact boundary conditions to the electroded region of the active and passive layers provides better agreement to experimental data compared to modeling the entire actuator as continuous. To improve the applicability of dielectric elastomer-based actuators for active origami-inspired structures, folding actuators are developed by taking advantage of localized deformation caused by a passive layer with non-uniform thickness. Two-dimensional analysis of the folding actuators shows that agreement to experimental data diminishes as localized deformation increases. Limitations of using pressures to approximate the electromechanical coupling of the dielectric elastomer under an applied electric field and additional modeling considerations are also discussed.
    Smart Materials and Structures 08/2014; 23(9):094002. DOI:10.1088/0964-1726/23/9/094002 · 2.45 Impact Factor
  • Smart Materials and Structures 08/2014; 23(9):090201. DOI:10.1088/0964-1726/23/9/090201 · 2.45 Impact Factor
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    ABSTRACT: A contact-aided compliant mechanism (CCM) called a compliant spine (CS) is presented in this paper. It is flexible when bending in one direction and stiff when bending in the opposite direction, giving it a nonlinear bending stiffness. The fundamental element of this mechanism is a compliant joint (CJ), which consists of a compliant hinge (CH) and contact surfaces. The design of the compliant joint and the number of compliant joints in a compliant spine determine its stiffness. This paper presents the design and optimization of such a compliant spine. A multi-objective optimization problem with three objectives is formulated in order to perform the design optimization of the compliant spine. The goal of the optimization is to minimize the peak stress and mass while maximizing the deflection, subject to geometric and other constraints. Flapping wing unmanned air vehicles, also known as ornithopters, are used as a case study in this paper to test the accuracy of the design optimization procedure and to prove the efficacy of the compliant spine design. The optimal compliant spine designs obtained from the optimization procedure are fabricated, integrated into the ornithopter's wing leading edge spar, and flight tested. Results from the flight tests prove the ability of the compliant spine to produce an asymmetry in the ornithopter's wing kinematics during the up and down strokes.
    Journal of Mechanisms and Robotics 06/2014; 6(3):031013. DOI:10.1115/1.4027702 · 0.86 Impact Factor
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    ABSTRACT: The objective of origami engineering is to combine origami principles with advanced materials to yield active origami shapes, which fold and unfold in response to external stimuli. We are investigating the use of P(VDF-TrFE-CTFE), a relaxor ferroelectric terpolymer, to realize origami-inspired folding and unfolding of structures and also to actuate paper made origami actuators. Different approaches have been undertaken, ranging from unimorph configuration to multilayered/stacked actuator configuration, to achieve electrostriction based origami structures Apart from building active origami structures, both quasi-static and dynamic thickness strain (1Hz, 10Hz) for induced electric field have been measured and compared. Furthermore, electromechanical characterization has been done by conducting force displacement characterization of multilayered terpolymer actuators
    MRS Spring Meeting & Exhibit, San Francisco,CA,USA; 04/2014
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    ABSTRACT: We are investigating the use of dielectric elastomers (DE) to realize origami-inspired folding and unfolding of structures. DEs are compliant materials where the coupled electro-mechanical actuation takes advantage of the low modulus and high breakdown strength of the elastomer. Until recently, pre-straining of relatively thick DE materials was necessary in order to achieve the high electric fields required to trigger electrostatic actuation. However, the current availability of thinner DE materials (ex: VHB 9469PC-130μm, VHB 9473 PC −260 μm) has enabled their actuation at achievable electric fields without the need to pre-strain. In this work, an exhaustive study on the fundamentals of DE actuation is done by exploring thickness actuation mechanism and studying the change in dielectric permittivity; we also take advantage of the thin DEs to build actuators with very large bending angles. In particular, we relate the electrostatically-induced thickness contraction in a DE monomorph to the resulting bending once an inactive substrate is added. Both statically and dynamically induced electromechanical thickness strains are measured, and the experimental data is used as an input to a bender model to predict and optimize bending response; variables such as type of inactive material, number of DE layers, and type of electrodes are examined. We will also experimentally track the changes in the dielectric constant as a function of strain, electrode type, and applied electric field; the measured behavior will be used to model thickness and bending actuation. These fundamental studies are necessary to determine ability and limitation of DE materials in a bender configuration. Finally, bending of the DE actuator is transformed into folding by a novel geometric approach, where different shaped notches are introduced in the inactive substrate. The folding configuration is a step towards realizing active origami structure.
    ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems; 09/2013
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    ABSTRACT: A device that can provide articulation to surgical tool tips is needed in natural orifice transluminal endoscopy surgery (NOTES). In this paper, we propose a compliant articulation structure that uses superelastic NiTiNOL to achieve a large deflection angle and force in a compact size. Six geometric parameters are used to define this structure, and constraints based on the fabrication process are imposed. Using finite element analysis, a family of designs is evaluated in terms of the free deflection angle and blocked force. The same family of designs is evaluated for both NiTiNOL and stainless steel. It can be seen that significant benefits are observed when using NiTiNOL compared to 316 stainless steel; a maximum free deflection angle of 64.8° and maximum blocked force of 24.7 N are predicted. The structures are designed to avoid stress concentrations, and design guidelines are recommended. The meso-scale articulation structure is fabricated using both a Coherent Avia Q-switched, 355 nm laser and a Myachi Unitek 200 W single mode pulsed fiber laser with active water cooling. Select fabricated structures are then tested to validate the finite element models.
    Smart Materials and Structures 08/2013; 22(9):094018. DOI:10.1088/0964-1726/22/9/094018 · 2.45 Impact Factor
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    ABSTRACT: The use of origami principles to create 3-dimensional shapes has the potential to revolutionize active material structures and compliant mechanisms. Active origami structures can be applied to a broad range of areas such as reconfigurable aircraft and deployable space structures as well as instruments for minimally invasive surgery. Our current research is focused on dielectric elastomer (DE) and magneto active elastomer (MAE) materials to create multi-field responsive structures. Such multi-field responsive structures will integrate the DE and MAE materials to enable active structures that fold/unfold in different ways in response to electric and/or magnetic field. They can also unfold either as a result of eliminating the applied field or in response to the application of an opposite field. This concept is demonstrated in a folding cube shape and induced locomotion in the MAE material. Two finite element models are developed for both the DE and MAE materials and validated through physical testing of these materials. The models are then integrated to demonstrate multi-field responses of a bi-fold multi-field responsive structure. The bi fold model is designed to fold about one axis in an electric field and a perpendicular axis in a magnetic field. Future modeling efforts and research directions are also discussed based on these preliminary results.
    Proceedings of the ASME 2013 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2013, Portland, Oregon, USA; 08/2013
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    ABSTRACT: Compliant mechanisms have many advantages over rigid-link mechanisms. However, one of the challenges of compliant mechanisms is the trade-off between a large range of motion and a high out-of-plane stiffness. Furthermore, the out-of-plane stiffness is shown to vary over the range of motion. Especially for large-displacement compliant mechanisms this can be by a significant amount. In this paper the use of curved beam elements in a compliant mechanism is shown to have impact on this trade-off. The influence of curved beam elements on the out-of-plane stiffness over the entire range of motion is presented for simple structures such as a single beam element and double beam elements, as well as a compliant finger. With the use of a genetic algorithm optimization, the difference in performance of a design with only straight beam elements versus one with curved beam elements is highlighted and the effect on the out-of-plane stiffness profile is presented. The optimization with curved beam elements results in solutions with a performance in terms of objective function values that cannot be found by the optimization with only straight beam elements. It is shown that for simple structures the use of curved beam elements has a large influence on the shape of the out-of-plane stiffness profile along the range of motion, while for the compliant finger the influence is mainly in the variables of the out-of-plane stiffness profile.
    ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference; 08/2013
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    ABSTRACT: A methodology for topology optimization to the design of compliant cellular mechanisms with and without internal contact is presented. A two-step procedure is pursued. First, a baseline noncontact mechanism is developed and optimized via an inverse homogenization method using the "solid isotropic material with penalization" approach. This compliant mechanism is optimized to yield specified elasticity coefficients, with the capability to sustain large effective strains by minimizing local linear elastic strain. In the second step, a system of internal contacts is designed. The initial continuum model of a noncontact mechanism is converted into a frame model, and possible contact links are defined. A computationally efficient algorithm is employed to eliminate those mechanisms having overlapping contact links. The remaining nonoverlapping designs are exhaustively investigated for stress relief. A differential evolution optimizer is used to maximize the stress relief. The results generated for a range of specified elasticity coefficients include a honeycomb-like cell, an auxetic cell, and a diamond-shaped cell. These various cell topologies have different effective properties corresponding to different structural requirements. For each such topology, a contact mechanism is devised that demonstrates stress relief. In one such case, the contact mechanism increases the strain magnification ratio by about 30%. [DOI: 10.1115/1.4007694]
    Journal of Mechanical Design 12/2012; 134(12):121001. DOI:10.1115/1.4007694 · 1.17 Impact Factor
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    ABSTRACT: Contact-aided compliant cellular mechanisms are cellular structures designed with contact mechanisms integrated into each cell to provide stress relief. This article addresses compliant cellular structures having curved walls and internal contact mechanisms. The use of curved walls in cellular structures tends to improve their performance in terms of global strain capability and is beneficial for fabrication. In some cells, the addition of contact mechanisms results in stress relief, allowing the cells to be stretched farther than they could without contact. The cellular structures with curved walls are modeled, and finite element analysis is used to calculate the maximum global strains for comparable noncontact and contact-aided cells. An optimization procedure is performed to find the cell geometries that result in the highest global strains. Strains of up to 32.4% and 19.7% are predicted for the optimized curved noncontact and contact-aided cells, respectively. Additionally, a comparison of curved and noncurved, noncontact and contact-aided cells shows that the addition of curved walls results in a significantly greater improvement in global strains than that gained by adding a contact mechanism. Mesoscale contact-aided compliant cellular mechanism designs are fabricated via the lost mold–rapid infiltration forming process and are tested using a custom-designed test rig.
    Journal of Intelligent Material Systems and Structures 11/2012; 23(16):1773-1785. DOI:10.1177/1045389X12453962 · 2.17 Impact Factor
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    ABSTRACT: Contact aided compliant mechanisms are a class of compliant mechanisms where parts of the mechanism come into contact with one another during motion. Such mechanisms can have nonlinear stiffness, cause stress-relief, or generate non-smooth paths. New contact aided compliant mechanisms called bend-and-sweep compliant mechanisms are presented in this paper. These bend-and-sweep mechanisms are made up of compliant joints which are alternately located in two orthogonal directions, and they also exhibit nonlinear stiffness in two orthogonal directions. The stiffness properties of these mechanisms, in each direction, can be tailored by varying the geometry of the compliant joints. One application of these mechanisms is in the passive wing morphing of flapping wing UAVs or ornithopters. A design study is conducted to understand the effect of hinge geometry on the deflections and maximum von Mises stress during upstroke and downstroke. It is shown that the bend-and-sweep compliant elements deflect as desired in both the bending and sweep directions.
    ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems; 09/2012
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    ABSTRACT: This paper presents the optimization of hexagonal honeycomb structures with internal contact mechanisms for energy absorption applications. While extensive work has been reported in the literature on traditional honeycombs of varying geometries under dynamic and static loading, contact-aided compliant cellular mechanisms under quasi-static crushing or impact have not been previously considered. This paper addresses this void through the optimization of a hexagonal honeycomb unit cell containing a contact mechanism. An optimization problem is formulated that maximizes the strain energy per area of a contact-aided compliant cellular mechanism. Two- and three-variable optimization problems are considered, using variables that define the cell geometry and the initial contact gap. It is found that with the addition of a contact mechanism, more strain energy can be absorbed when compared to the same cell without a contact mechanism.
    ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference; 08/2012
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    ABSTRACT: Few standardized testing procedures exist for instruments intended for Natural Orifice Translumenal Endoscopic Surgery. These testing procedures are critical for evaluating surgical skills and surgical instruments to ensure sufficient quality. This need is widely recognized by endoscopic surgeons as a major hurdle for the advancement of Natural Orifice Translumenal Endoscopic Surgery. Beginning with tasks currently used to evaluate laparoscopic surgeons and instruments, new tasks were designed to evaluate endoscopic surgical forceps instruments. Six tasks have been developed from existing tasks, adapted and modified for use with endoscopic instruments, or newly designed to test additional features of endoscopic forceps. The new tasks include the Fuzzy Ball Task, Cup Drop Task, Ring Around Task, Material Pull Task, Simulated Biopsy Task, and the Force Gauge Task. These tasks were then used to evaluate the performance of a new forceps instrument designed at Pennsylvania State University. The need for testing procedures for the advancement of Natural Orifice Translumenal Endoscopic Surgery has been addressed in this work. The developed tasks form a basis for not only testing new forceps instruments, but also for evaluating individual performance of surgical candidates with endoscopic forceps instruments.
    JSLS: Journal of the Society of Laparoendoscopic Surgeons / Society of Laparoendoscopic Surgeons 01/2012; 16(1):95-104. DOI:10.4293/108680812X13291597716186 · 0.79 Impact Factor
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    ABSTRACT: Knowledge discovery in multi-dimensional data is a challenging problem in engineering design. For example, in trade space exploration of large design data sets, designers need to select a subset of data of interest and examine data from different data dimensions and within data clusters at different granularities. This exploration is a process that demands both humans, who can heuristically decide what data to explore and how best to explore it, and computers, which can quickly extract features that may be of interest in the data. Thus, to support this process of knowledge discovery, we need tools that can go beyond traditional computer-oriented optimisation approaches and support advanced designer-centred trade space exploration and data interaction. This paper is an effort to address this need. In particular, we propose the interactive multiscale-nested clustering and aggregation framework to support trade space exploration of multi-dimensional data common to design optimisation. A system prototype of this framework is implemented to allow users to visually examine large design data sets through interactive data clustering, aggregation, and visualisation. The paper also presents an evaluation study involving morphing wing design using this prototype system.
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    ABSTRACT: This paper presents a 3.0 mm diameter multifunctional endoscopic forceps design for use in minimally invasive flexible endoscopic surgical procedures. Multifunctional capabilities including grasping, spreading, and cauterizing tissue are demonstrated experimentally and compared to commercially available forceps. Models of the proposed design predict considerable improvements in opening range (140%) and force application (87%) for both grasping and spreading when compared to currently used endoscopic forceps. Several of the tool's design characteristics promote fail-safe malfunctions, including locking before catastrophic failure and a decreased likelihood in detached parts. Initial benchtop testing shows good agreement between prototype performance and model prediction. Frictional losses experienced during testing were found to depend on load orientation. [DOI: 10.1115/1.4005225]
    Journal of Medical Devices 12/2011; 5(4):041001. DOI:10.1115/1.4005225 · 0.62 Impact Factor
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    ABSTRACT: This paper describes a multidisciplinary project focused on developing design and fabrication methods for narrow-gauge compliant mechanisms expected to be useful in advanced minimally invasive surgery. In this paper, three aspects of the project are discussed: meso-scale fabrication, compliant mechanism design, and experimental determination of mechanical properties and forceps performance. The selected manufacturing method is a lost mold rapid infiltration forming process that is being developed at Penn State University. The process is capable of producing hundreds of freestanding metallic and ceramic parts with feature sizes ranging from sub-10 mu m to approximately 300 mu m. To fulfill surgical and manufacturing requirements, a contact-aided compliant mechanism design is proposed. A finite element analysis solution, used to evaluate large deformation and contact, is implemented into an optimization routine to maximize tool performance. A case study demonstrates the design and manufacturing processes for a 1 mm diameter austenitic (300 series) stainless steel forceps. Due to manufacturing variables that affect grain size and particle adhesion, the strength of the fabricated parts are expected to vary from the bulk material properties. Therefore, fabricated parts are experimentally tested to determine accurate material properties. Three point bend tests reveal yield strengths between 603 and 677 MPa. Results from the design optimization routine show that material strengths within this range require large instrument aspect ratios between 40 and 50 with anticipated blocked forces as high as 1.5 N. An initial prototype is assembled and tested to compare experimental and theoretical tool performance. Good agreement between the computational and experimental data confirms the efficacy of the processes used to develop a meso-scale contact-aided compliant forceps. [DOI: 10.1115/1.4004539]
    Journal of Mechanical Design 08/2011; 133(8):081005. DOI:10.1115/1.4004539 · 1.17 Impact Factor
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    ABSTRACT: Free standing, micron scale, yttria stabilized zirconia parts for surgical instrument applications have been fabricated using a lithography based mold forming technique. Problems and solutions inherent to molding micron scale ceramic parts, such as suspension viscosity, surface spallation, and surface roughness are addressed. Concentrated zirconia suspensions, achieved through a chemically aided attrition milling process, are gelcast into molds via a screen printing method to form parts. After sintering, near theoretical density (99.8%) is achieved with a grain size of 500 nm.
    Characterization and Control of Interfaces for High Quality Advanced Materials II: Ceramic Transactions, Volume 198, 06/2011: pages 179 - 184; , ISBN: 9781118144145

Publication Stats

1k Citations
78.05 Total Impact Points


  • 2002–2014
    • William Penn University
      Worcester, Massachusetts, United States
  • 1999–2014
    • Pennsylvania State University
      • • Department of Mechanical and Nuclear Engineering
      • • Department of Industrial and Manufacturing Engineering
      University Park, Maryland, United States
  • 2006
    • University of Dayton
      Dayton, Ohio, United States
  • 1998–2003
    • University of Michigan
      • Department of Mechanical Engineering
      Ann Arbor, Michigan, United States