Mechanical Engineering Commons^™

Development Of The End-Effector Of A Cable-Driven Parallel Manipulator For Automated Crop Sensing, Iman Salafian

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

A four cable-driven parallel manipulator (4CDPM), consisting of sophisticated spectrometers and imagers, is under development for use in acquiring phenotypic and environmental data over an acre-sized maize field. This thesis presents the design, controls, and testing of two sub-systems in a 4CDPM: a Center of Mass Balance System (CMBS) and a Drop-Down System (DDS).

One of the factors that influences stability is the center of mass (COM) position of the end effector. An offset in COM can cause a pendulum effect or an undesired tilt angle. A center of mass balancing system is presented in this thesis to minimize the …

Meniscus-Assisted Solution Printing Of Largegrained Perovskite Films For High-Efficiency Solar Cells, Ming He, Bo Li, Xun Cui, Beibei Jiang, Yanjie He, Yihuang Chen, Daniel O'Neil, Paul Szymanski, Mostafa A. El-Sayed, Jinsong Huang, Zhiqun Lin

Department of Mechanical and Materials Engineering: Faculty Publications

Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics. However, this remains particularly challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Here we report a simple yet effective meniscus-assisted solution printing (MASP) strategy to yield large-grained dense perovskite film with good crystallization and preferred orientation. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparts the transport of perovskite solutes, thus facilitating the growth of micrometre-scale perovskite grains. The growth kinetics of perovskite …

Application Of Dfx Methods To A Gait Rehabilitation System, Devin K. Elley

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Walking is an important physical activity that offers major health benefits for those who are able to perform the task. However, there are millions of people worldwide who have lost the ability to walk from physical accidents or a disease which limits the ability for them to use their legs. Often these patients use gait therapy to learn how to walk again. During this gait therapy, a physical therapist may use gait rehabilitation machines to assist the patient in learning to walk in a correct gait path.

Two gait rehabilitation machine iterations were designed to produce an effective rehabilitation machine …

Dissipative Elastic Metamaterial With A Lowfrequency Passband, Yongquan Liu, Jianlin Yi, Zheng Li, Xianyue Su, Wenlong Li, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its …

Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

Scattering of elastic waves in heterogeneous media has become one of the most important problems in the field of wave propagation due to its broad applications in seismology, natural resource exploration, ultrasonic nondestructive evaluation and biomedical ultrasound. Nevertheless, it is one of the most challenging problems because of the complicated medium inhomogeneity and the complexity of the elastodynamic equations. A widely accepted model for the propagation and scattering of elastic waves, which properly incorporates the multiple scattering phenomenon and the statistical information of the inhomogeneities is still missing. In this work, the author developed a multiple scattering model for heterogeneous …

A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman

Department of Mechanical and Materials Engineering: Faculty Publications

An important goal for treatment of sports injuries is to have as short a recovery time as possible. The critical problem with current orthopedic implants is that they are designed to be permanent and have a high complication rate (15%) that often requires removal and replacement with a second surgery; and subsequently a second rehabilitation cycle. This study was designed to test the feasibility of having a device that could provide the needed mechanical properties, while promoting healing, for a specified amount of time and then degrade away, to shorten the recovery time. The specific strategy was to create a …

Safer Sweep Auger Operation Using Robotics, Nathan A. Wulf

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis presents a remotely controlled robotic solution for those who must sometimes enter agriculturally confined spaces in attempts to assist with grain bin cleanout, particularly by manipulating the sweep auger. In 2015 alone, there were at least 47 documented incidents that occurred in agriculturally confined spaces, of which more than half were fatal. While there have been several advancements in the quality and effectiveness of sweep augers, there have been very few that offer the safety and adaptability of the robotic solution proposed. This robotic solution is a four-wheeled, skid-steering style robot with camera and lighting attachments that allow …

Peridynamic Models For Fatigue And Fracture In Isotropic And In Polycrystalline Materials, Guanfeng Zhang

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

To improve design and reliability, extensive efforts has been devoted to understanding damage and failure of materials and structures using numerical simulation, as a complement of theory and experiment. In this thesis, peridynamics is adopted to study fatigue and dynamic failure problems.

Fatigue is a major failure mode in engineering structures. Predicting fracture/failure under cyclic loading is a challenging problem. Classical model cannot directly be applied to problems with discontinuities. A peridynamic model is adopted in this work because of important advantages of peridynamics in allowing autonomous crack initiation and propagation. A recently proposed peridynamic fatigue crack model is considered …

Applications Of Femtosecond Laser Processed Metallic Surfaces: Leidenfrost Point And Thermal Stability Of Rare Earth Oxide Coatings, Anton Charles Hassebrook

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In this thesis, micro/nano structured surfaces were created through the use of Femtosecond Laser Surface Processing (FLSP). In the first part of the thesis, an experimental investigation of the effects of droplet diameters and fluid properties on the Leidenfrost temperature of polished and nano/microstructured surfaces has been carried out. Leidenfrost experiments were conducted on a stainless steel 304 polished surface and a stainless steel surface which was processed by a femtosecond laser to form Above Surface Growth (ASG) nano/microstructures. Surface preparation resulted in a root mean square roughness (R_rms) of 4.8 µm and 0.04 µm on the laser …

Development Of Peritoneal Microbubble Oxygenation As An Extrapulmonary Treatment For Hypoxia, Nathan Legband

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Patients affected by a respiratory disease or injury experience a substantially impaired respiratory system and as a consequence are unable to obtain a sufficient amount of oxygen. Hypoxia can quickly result in developing permanent tissue damage or death. Currently, the medical methods of treating hypoxia are mechanical ventilation or extracorporeal membrane oxygenation. However, these treatments are ineffective in certain cases and possess significant additional risks including barotrauma, infection, hemorrhage, and thrombosis.

The extrapulmonary method of peritoneal oxygenation has been investigated by other research groups as a potential alternative to providing supplemental oxygen in hypoxic animals. In peritoneal oxygenation, the peritoneum, …

On The Wetting States Of Low Melting Point Metal Galinstan And Wetting Characteristics Of 3-Dimensional Nanostructured Fractal Surfaces, Ethan Allan Davis

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Exergy, or the availability of energy for useful work, is a critical issue that must be addressed to accommodate growing energy demands of society. Increasing population and steady advancement of technology necessitates novel approaches to the management, conversion, and storage of energy. Per the Lawrence Livermore National Laboratory, approximately 60 percent of the energy used by the United States in 2015 was rejected as waste [1]; a large quantity of which can be assumed to be in the form of heat. Therefore, novel thermal management methods for waste heat are critical to increasing energy efficiency and sustainability in the future. …

Near-Field Thermal Radiation For Solar Thermophotovoltaics And High Temperature Thermal Logic And Memory Applications, Mahmoud Elzouka

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (~1 μm). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties.

Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a …

Design And Validation Of An In Vivo Long-Term Attachment Capsule Robot, Wanchuan Xie

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The invention of capsule endoscopy (CE) made the non-invasive monitoring of the entire small bowel possible and became the primary means for diagnosing small bowel pathology. In the last decade, capsule robots have been transformed from diagnostic devices into a widely studied biomedical platform with the potential for active locomotion, drug delivery and therapeutic capabilities. To perform accurate on-site drug release and therapy, it is necessary for a capsule robot to be able to attach to the intestinal tissue and maintain its position long-term. Design challenges derive from the task of long-term mucosal adhesion which requires firm, quick-response attachment without …

Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

No abstract provided.

Superpositioning High Power Lasers For Mid-Air Image Formations, Auston Viotto

UCARE: Research Products

This research evaluates different methods to create voxels, 3-dimensional pixels, in air without the need for special glasses or reflections off of surfaces. Research on the advantages of superimposing or the culmination, focusing, of laser light will be conducted. The point of superpositioning/culmination will be evaluated by the brightness of the voxel due to the Rayleigh Scatter Effect. The voxel’s brightness is dependent on the laser output strength and inversely proportional to its wavelength. Once a superimposed/culminated voxel has been created in the lab the next step will be to manipulate the location of the voxel through 3-dimensional space. This …

Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

There is controversy regarding the directional dependence of head responses subjected to blast loading. The goal of this work is to characterize the role of head orientation in the mechanics of blast wave-head interactions as well as the load transmitting to the brain. A three-dimensional human head model with anatomical details was reconstructed from computed tomography images. Three different head orientations with respect to the oncoming blast wave, i.e., front-on with head facing blast, back-on with head facing away from blast, and side-on with right side exposed to blast, were considered. The reflected pressure at the blast wave-head interface positively …

Oxidation Of Ti2Alc In High Temperature Steam Environment, Ziyad M. Smoqi

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

High temperature oxidation of fuel cladding materials, during the loss of coolant accident (LOCA), is of utmost importance for next-generation nuclear energy systems. Ti₂AlC is a promising candidate material for nuclear applications due to its outstanding properties such as thermal stability at high temperatures, oxidation resistance in air, thermal shock resistance, low neutron absorption cross-section, and the resistance to irradiation-induced amorphization. In this research, high temperature steam oxidation experiments were conducted to evaluate the oxidation resistance of Ti₂AlC in LOCA conditions. After oxidation in 100% steam at 600 and 800˚C, the oxidation kinetics followed a parabolic …

Negahban Group Report: Saw-Tooth Shear Response Of Aged Poly(Methyl Methacrylate) (Pmma), Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

Results for isothermal saw-tooth shear loading experiments conducted on annealed and oven-cooled poly(methyl methacrylate) (PMMA) at temperatures between 50^oC and 140^oC. The experiments were conducted 1996.

Formation Of Mound-Like Multiscale Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Ryan Bell, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Surface Functionalization Technique • Femtosecond Laser Surface Processing (FLSP) • Utilize high power, femtosecond (10-15 s) laser pulses • Produce self-organized, multiscale surface micro/nanostructures • Diverse range of applicable substrates: semiconductors, metals, polymers, & composites

Why? • What are the different types of FLSP structures on Ti? • Physical evidence needed for FLSP formation models • Optimize FLSP of Ti for biomedical & other applications

How? • Obtain evidence of mound growth processes by examining underlying microstructure • Utilize dual beam Scanning Electron Microscope-Focused Ion Beam instrument to cross section surface structures & fabricate transmission electron microscopy samples

Dirichlet Process Gaussian Mixture Models For Real-Time Monitoring And Their Application To Chemical Mechanical Planarization, Jia (Peter) Liu, Omer F. Beyca, Prahalad K. Rao, Zhenyu (James) Kong, Satish T. S. Bukkapatnam

Department of Mechanical and Materials Engineering: Faculty Publications

The goal of this work is to use sensor data for online detection and identification of process anomalies (faults). In pursuit of this goal, we propose Dirichlet process Gaussian mixture (DPGM) models. The proposed DPGM models have two novel outcomes: 1) DP-based statistical process control (SPC) chart for anomaly detection and 2) unsupervised recurrent hierarchical DP clustering model for identification of specific process anomalies. The presented DPGM models are validated using numerical simulation studies as well as wireless vibration signals acquired from an experimental semiconductor chemical mechanical planarization (CMP) test bed. Through these numerically simulated and experimental sensor data, we …

Nebraska Summary: S1141 John Deere 6120r, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

Tractor Test 2174: John Deere 9620rx Diesel, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane …

The Effect Of Number Of Corrugation On Crashworthiness Of Aluminum Corrugated Tube Under Lateral Loading, Hozhabr Mozafari, Arameh Eyvazian, Abdel Magid Hamouda

Department of Mechanical and Materials Engineering: Faculty Publications

Thin-walled tubes have been developed and are growing in use as new energy absorber structures. The objective of this study is to investigate the energy absorption and crushing characteristics of corrugated tubes with different number of corrugation in a specific length exposed to lateral loading. At the first step, experimental tests were carried out on a corrugated tube with three con'ugations (two inner and one outer) and a tube without corrugation. After that, a finite element model was developed by means of ABAQUS software in order to study the effect of corrugation number on crushing properties of thin-walled tubes. The …

Methods, Systems, And Devices For Surgical Visualization And Device Manipulation, Shane M. Farritor, Mark Rentschler, Amy Lehman, Nathan A. Wood, Adam Bock, Reed Prior

Department of Mechanical and Materials Engineering: Faculty Publications

A surgical device includes a console having a visual display and a manipulator arm, a robotic device having a camera and a connection component. The robotic device is configured to be positioned completely within a body cavity. The camera is configured to transmit visual images to the visual display. The connection component operably couples the console and the robotic device. The manipulator arm is positioned relative to the visual display so as to appear to be penetrating the visual display.

Local And Segmental Motions Of The Mobile Amorphous Fraction In Semi-Crystalline Polylactide Crystallized Under Quiescent And Flow-Induced Conditions, Xavier Monnier, Laurence Chevalier, Antonello Esposito, Lucia Fernandez-Ballester, Allisson Saiter, Eric Dargent

Department of Mechanical and Materials Engineering: Faculty Publications

The molecular dynamics of the constrained and unconstrained mobile amorphous fractions in semicrystalline polylactide (PLA) was investigated in the presence of both flow-induced crystalline structures and spherulites by fast scanning calorimetry (FSC) through cooperativity and physical aging concepts. First, the shear rate conditions leading to flow-induced crystallization were characterized by examining the relaxation of shear-induced precursors. At a temperature of 150 °C, the critical relaxation time is so long that cooling down the sheared melt to the crystallization temperature does not affect significantly the precursors. Therefore, highly oriented structures develop. The arrangement of the crystalline fraction, either in flow-induced crystalline …

Experimental Study Of Corrugated Metal-Composite Tubes Under Axial Loading, Arameh Eyvazian, Hozhabr Mozafari, Abdel Magid Hamouda

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, crushing behavior of corrugated metal-composite tube was examined experimentally under axial loading condition. Six types of specimens, classified into two groups of metal and metal-composite, were tested under quasi static axial loading. The failure mechanism and failure history of the specimens were presented and discussed. The experimental result showed that corrugated metal composite tubes demonstrate perfect energy absorption characteristics in terms of uniformity of load-displacement diagram, reduction of initial peak load and controlling failure mechanism. Moreover, it was also found that adding filament wound layer of composite on the surface of metallic corrugated tube compensated weakness of …

Disturbed Cyclical Stretch Of Endothelial Cells Promotes Nuclear Expression Of The Pro-Atherogenic Transcription Factor Nf-Kb, Ryan M. Pedrigi, Konstantinos I. Papadimitriou, Avinash Kondiboyina, Sukhjinder Sidhu, James Chau, Miten B. Patel, Daniel C. Baeriswyl, Emmanuel M. Drakakis, Rob Krams

Department of Mechanical and Materials Engineering: Faculty Publications

Exposure of endothelial cells to low and multidirectional blood flow is known to promote a pro-atherogenic phenotype. The mechanics of the vessel wall is another important mechano-stimulus within the endothelial cell environment, but no study has examined whether changes in the magnitude and direction of cell stretch can be pro-atherogenic. Herein, we developed a custom cell stretching device to replicate the in vivo stretch environment of the endothelial cell and examined whether low and multidirectional stretch promote nuclear translocation of NF-kB. A fluid–structure interaction model of the device demonstrated a nearly uniform strain within the region of cell attachment and …

Quantification Of Re-Absorption And Re-Emission Processes To Determine Photon Recycling Efficiency In Perovskite Single Crystals, Yanjun Fang, Haotong Wei, Qingfeng Dong, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Photon recycling, that is, iterative self-absorption and re-emission by the photoactive layer itself, has been speculated to contribute to the high open-circuit voltage in several types of high efficiency solar cells. For organic–inorganic halide perovskites that have yielded highly efficient photovoltaic devices, however, it remains unclear whether the photon recycling effect is significant enough to improve solar cell efficiency. Here we quantitatively evaluate the re-absorption and re-emission processes to determine photon recycling efficiency in hybrid perovskite with its single crystals by measuring the ratio of the re-emitted photons to the initially excited photons, which is realized by modulating their polarization …

Target Lesion Calcium Arc Influence The Performance Of Stenting, Pengfei Dong, Shengmao Lin, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Percutaneous coronary intervention (PCI) is the most common revascularization procedure, in which, fibrocalcific plaques are found in 17–35% of patients undergoing PCI [1]. Numbers will rise with population aging and prolonged statin treatment. Calcifications often lead to stent under expansion and strut malapposition, with increased risk of thrombosis and in-stent restenosis [2]. Presence of calcium strongly inhibits stent performance, a well-documented metric for outcome [3]. The goal of this work is to develop the finite element models for inspecting the influence of the calcium arc extent on the stenting outcomes, such as the stress and strain distribution within the plaque, …