Matching Items (7)
Description
This paper describes an effort to bring wing structural stiffness and aeroelastic considerations early in the conceptual design process with an automated tool. Stiffness and aeroelasticity can be well represented with a stochastic model during conceptual design because of the high level of uncertainty and variability in wing non-structural mass such as fuel loading and control surfaces. To accomplish this, an improvement is made to existing design tools utilizing rule based automated design to generate wing torque box geometry from a specific wing outer mold-line. Simple analysis on deflection and inferred stiffness shows how early conceptual design choices can strongly impact the stiffness of the structure. The impacts of design choices and how the buckling constraints drive structural weight in particular examples are discussed. The model is then carried further to include a finite element model (FEM) to analyze resulting mode shapes and frequencies for use in aeroelastic analysis. The natural frequencies of several selected wing torque boxes across a range of loading cases are compared.
ContributorsMiskin, Daniel L (Author) / Takahashi, Timothy T (Thesis advisor) / Mignolet, Marc (Committee member) / Murthy, Raghavendra (Committee member) / Arizona State University (Publisher)
Created2018
Description
It is a common assumption in the bicycle industry that stiffer frames generally perform better than flexible frames, because they transfer power more efficiently and absorb less energy from the rider's pedal stroke in the form of spring potential energy. However, in the last few years, Jan Heine of Bicycle Quarterly has developed an alternative theory, which he calls "planing", whereby a flexible frame can improve rider performance by not resisting the leg muscles as much, preventing premature muscle fatigue and allowing the rider to actually produce more consistent power, an effect which overwhelms any difference in power transfer between the different stiffness levels of frames. I performed several tests in which I measured the power input to the bicycle through the crankset and power output through a power-measuring trainer in the place of the rear hub. Heart rate data was collected along with most of these tests. Four bicycles were used with three distinct levels of stiffness. After performing several ANOVA tests to determine the effect of stiffness on the parameters of average power output during a sprint, maximum power output during a sprint, maximum heart rate during a sprint, difference between power-in and power-out during both sprints and longer efforts, and power quotient during a sprint, I found no effects of frame stiffness on any of these factors except power quotient. The finding for power quotient suggests a positive relationship between quotient and stiffness, which directly refutes the Planing Theory for the test riders and levels of stiffness represented in this test. Also, no statistically significant effect of stiffness on the difference between power-in and power-out was found, refuting the Power Transfer Theory for the riders and levels of stiffness represented in this test.
ContributorsSparks, Graham Philip (Author) / Takahashi, Timothy (Thesis director) / Middleton, James (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
We experience spatial separation and temporal asynchrony between visual and
haptic information in many virtual-reality, augmented-reality, or teleoperation systems.
Three studies were conducted to examine the spatial and temporal characteristic of
multisensory integration. Participants interacted with virtual springs using both visual and
haptic senses, and their perception of stiffness and ability to differentiate stiffness were
measured. The results revealed that a constant visual delay increased the perceived stiffness,
while a variable visual delay made participants depend more on the haptic sensations in
stiffness perception. We also found that participants judged stiffness stiffer when they
interact with virtual springs at faster speeds, and interaction speed was positively correlated
with stiffness overestimation. In addition, it has been found that participants could learn an
association between visual and haptic inputs despite the fact that they were spatially
separated, resulting in the improvement of typing performance. These results show the
limitations of Maximum-Likelihood Estimation model, suggesting that a Bayesian
inference model should be used.
haptic information in many virtual-reality, augmented-reality, or teleoperation systems.
Three studies were conducted to examine the spatial and temporal characteristic of
multisensory integration. Participants interacted with virtual springs using both visual and
haptic senses, and their perception of stiffness and ability to differentiate stiffness were
measured. The results revealed that a constant visual delay increased the perceived stiffness,
while a variable visual delay made participants depend more on the haptic sensations in
stiffness perception. We also found that participants judged stiffness stiffer when they
interact with virtual springs at faster speeds, and interaction speed was positively correlated
with stiffness overestimation. In addition, it has been found that participants could learn an
association between visual and haptic inputs despite the fact that they were spatially
separated, resulting in the improvement of typing performance. These results show the
limitations of Maximum-Likelihood Estimation model, suggesting that a Bayesian
inference model should be used.
ContributorsSim, Sung Hun (Author) / Wu, Bing (Thesis advisor) / Cooke, Nancy J. (Committee member) / Gray, Robert (Committee member) / Branaghan, Russell (Committee member) / Arizona State University (Publisher)
Created2017
Description
Stiffness and flexibility are essential in many fields, including robotics, aerospace, bioengineering, etc. In recent years, origami-based mechanical metamaterials were designed for better mechanical properties including tunable stiffness and tunable collapsibility. However, in existing studies, the tunable stiffness is only with limited range and limited controllability. To overcome these challenges, two objectives were proposed and achieved in this dissertation: first, to design mechanical metamaterials with metamaterials with selective stiffness and collapsibility; second, to design mechanical metamaterials with in-situ tunable stiffness among positive, zero, and negative.In the first part, triangulated cylinder origami was employed to build deployable mechanical metamaterials through folding and unfolding along the crease lines. These deployable structures are flexible in the deploy direction so that it can be easily collapsed along the same way as it was deployed. An origami-inspired mechanical metamaterial was designed for on-demand deployability and selective collapsibility: autonomous deployability from the collapsed state and selective collapsibility along two different paths, with low stiffness for one path and substantially high stiffness for another path. The created mechanical metamaterial yields unprecedented load bearing capability in the deploy direction while possessing great deployability and collapsibility. The principle in this prospectus can be utilized to design and create versatile origami-inspired mechanical metamaterials that can find many applications.
In the second part, curved origami patterns were designed to accomplish in situ stiffness manipulation covering positive, zero, and negative stiffness by activating predefined creases on one curved origami pattern. This elegant design enables in situ stiffness switching in lightweight and space-saving applications, as demonstrated through three robotic-related components. Under a uniform load, the curved origami can provide universal gripping, controlled force transmissibility, and multistage stiffness response. This work illustrates an unexplored and unprecedented capability of curved origami, which opens new applications in robotics for this particular family of origami patterns.
ContributorsZhai, Zirui (Author) / Nian, Qiong (Thesis advisor) / Zhuang, Houlong (Committee member) / Huang, Huei-Ping (Committee member) / Zhang, Wenlong (Committee member) / Liu, Yongming (Committee member) / Arizona State University (Publisher)
Created2021
Description
Mechanical properties (e.g. deformability or stiffness) are critical to a cancer cell's ability to maneuver through and exert forces upon the extracellular matrix, and thus affect its ability to metastasize. §3.1 introduces the experimental method combining atomic force microscope (AFM) based indentation and confocal laser scanning microscopy (CLSM). §3.2 presents a method combining AFM and confocal microscopy (AFM stiffness nanotomography), and results on normal and pre-cancerous esophageal cells which indicate that even in the earliest stages, cancer cells exhibit increased deformability. §3.3 presents experimental results on weakly metastatic breast cancer cells that compare well with values obtained from other experimental methods and demonstrates that the mechanical response of cells to sharp and mesoscale probes differ significantly. §3.4 presents experimental results indicating that metastatic breast cancer cells are more deformable than normal counterparts, and demonstrates that indentation measurements with sharp probes are capable of identifying mechanical differences between cytoplasmic, nuclear and nucleolar regions of the cell. §3.5 presents results on weakly metastatic breast cancer cells sensitive and resistant to tamoxifen (an estrogen antagonist), and demonstrate that estrogen has a significant effect on cell stiffness. §3.6 applies stiffness nanotomography to study metastatic breast cancer cells allowed to invade 3D collagen gels, demonstrating the ability to use AFM indentation on heterogeneous samples, and shows that cell stiffness increases during the invasion process for partially and fully embedded metastatic breast cancer cells.
ContributorsStaunton, Jack Rory (Author) / Ros, Robert (Thesis advisor) / Lindsay, Stuart M. (Committee member) / Davies, Paul C. W. (Committee member) / Vaiana, Sara M. (Committee member) / Arizona State University (Publisher)
Created2014
Description
Stromal cells play an important role in facilitating disease progression of ductal carcinoma. Cancer associated fibroblasts (CAFs) are an important component of the extracellular matrix (ECM) which constitutes the microenvironment of breast tumor cells. They are known to participate in chemotherapeutic drug resistance by modulating various biochemical and biophysical factors that contribute to increased matrix stiffness and collagen I density of the tumor-adjacent stroma. To address these issues in terms of patient treatment, anti-cancer drug regimes have been assembled to incorporate both chemotherapeutic as well as anti-fibrotic drugs to both target tumor cells while also diminishing the elastic modulus of the microenvironment by targeting CAFs. The quantitative assessment of these drug regimes on tumor progression is missing in terms of CAFs role alone.
A high density 3D tumor model was utilized to recapitulate the tumor microenvironment of ductal carcinoma in vitro. The tumor model consisted of MDA-MB-231 tumors seeded within micromolded collagen wells, chemically immobilized upon a surface treated PDMS substrate. CAFs were seeded within the greater collagen structure from which the microwells were formed. The combinatorial effect of anti-fibrotic drug (Tranilast) and chemotherapy drug (Doxorubicin) were studied within 3D co culture conditions. Specifically, the combinatorial effects of the drugs on tumor cell viability, proliferation, and invasion were examined dynamically upon coculture with CAFs using the microengineered model.
The results of the study showed that the combinatorial effects of Tranilast and Doxorubicin significantly decreased the proliferative ability of tumor cells, in addition to significantly decreasing the ability of tumor cells to remain viable and invade their surrounding stroma, compared to control conditions.
A high density 3D tumor model was utilized to recapitulate the tumor microenvironment of ductal carcinoma in vitro. The tumor model consisted of MDA-MB-231 tumors seeded within micromolded collagen wells, chemically immobilized upon a surface treated PDMS substrate. CAFs were seeded within the greater collagen structure from which the microwells were formed. The combinatorial effect of anti-fibrotic drug (Tranilast) and chemotherapy drug (Doxorubicin) were studied within 3D co culture conditions. Specifically, the combinatorial effects of the drugs on tumor cell viability, proliferation, and invasion were examined dynamically upon coculture with CAFs using the microengineered model.
The results of the study showed that the combinatorial effects of Tranilast and Doxorubicin significantly decreased the proliferative ability of tumor cells, in addition to significantly decreasing the ability of tumor cells to remain viable and invade their surrounding stroma, compared to control conditions.
ContributorsSilva, Casey Rudolph (Author) / Nikkhah, Mehdi (Thesis director) / Saini, Harpinder (Committee member) / Harrington Bioengineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Advancements in the field of design and control of lower extremity robotics requires a comprehensive understanding of the underlying mechanics of the human ankle. The ankle joint acts as an essential interface between the neuromuscular system of the body and the physical world, especially during locomotion. This paper investigates how the modulation of ankle stiffness is altered throughout the stance phase of the gait cycle depending on the environment the ankle is interacting with. Ten young healthy subjects with no neurological impairments or history of ankle injury were tested by walking over a robotic platform which collected torque and position data. The platform performed a perturbation on the ankle at 20%, 40%, and 60% of their stance phase in order to estimate ankle stiffness and evaluate if the environment plays a role on its modulation. The platform provided either a rigid environment or a compliant environment in which it was compliant and deflected according to the torque applied to the platform. Subjects adapted in different ways to achieve balance in the different environments. When comparing the environments, subjects modulated their stiffness to either increase, decrease, or remain the same. Notably, stiffness as well as the subjects’ center of pressure was found to increase with time as they transitioned from late loading to terminal stance (heel strike to toe-off) regardless of environmental conditions. This allowed for a model of ankle stiffness to be developed as a function of center of pressure, independent of whether a subject is walking on the rigid or compliant environment. The modulation of stiffness parameters characterized in this study can be used in the design and control of lower extremity robotics which focus on accurate biomimicry of the healthy human ankle. The stiffness characteristics can also be used to help identify particular ankle impairments and to design proper treatment for individuals such as those who have suffered from a stroke or MS. Changing environments is where a majority of tripping incidents occur, which can lead to significant injuries. For this reason, studying healthy ankle behavior in a variety of environments is of particular interest.
ContributorsBliss, Clayton F (Author) / Lee, Hyunglae (Thesis director) / Marvi, Hamid (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05