Other Mechanical Engineering Commons^™

High-Velocity Projectile Impact Induced 9r Phase In Ultrafine-Grained Aluminium, Sichuang Xue, Zhe Fan, Olawale B. Lawal, Ramathasan Thevamaran, Qiang Li, Yue Liu, K. Y. Yu, Jian Wang, Edwin L. Thomas, Haiyan Wang, Xinghang Zhang

Department of Mechanical and Materials Engineering: Faculty Publications

Aluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations …

Controllable Energy Absorption Of Double Sided Corrugated Tubes Under Axial Crushing, Hozhabr Mozafari, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the mechanical advantage of the DSC tube in comparison with both SSC and classical straight (S) tubes under axial crushing. Results have shown that the total absorbed energy of the DSC aluminum tube with 14 corrugations was 330% and 32% higher than that of the SSC tube with 14 corrugations and the …

Novel Polyethylene Fibers Of Very High Thermal Conductivity Enabled By Amorphous Restructuring, Bowen Zhu, Jing Liu, Tianyu Wang, Shah R. Valloppilly, Shen Xu, Xinwei Wang

Department of Mechanical and Materials Engineering: Faculty Publications

High-thermal-conductivity polymers are very sought after for applications in various thermal management systems. Although improving crystallinity is a common way for increasing the thermal conductivity (k) of polymers, it has very limited capacity when the crystallinity is already high. In this work, by heat-stretching a highly crystalline microfiber, a significant k enhancement is observed. More interestingly, it coincides with a reduction in crystallinity. The sample is a Spectra S-900 ultrahigh-molecular-weight polyethylene (UHMW-PE) microfiber of 92% crystallinity and high degree of orientation. The optimum stretching condition is 131.5 °C, with a strain rate of 0.0129 s−1 to a low strain ratio …

Dislocations Interaction Induced Structural Instability In Intermetallic Al2Cu, Qing Zhou, Jian Wang, Amit Misra, Ping Huang, Fei Wang, Kewei Xu

Department of Mechanical and Materials Engineering: Faculty Publications

Intermetallic precipitates are widely used to tailor mechanical properties of structural alloys but are often destabilized during plastic deformation. Using atomistic simulations, we elucidate structural instability mechanisms of intermetallic precipitates associated with dislocation motion in a model system of Al₂Cu. Interaction of non-coplanar <001> dislocation dipoles during plastic deformation results in anomalous reactions—the creation of vacancies accompanied with climb and collective glide of <001> dislocation associated with the dislocation core change and atomic shuffle—accounting for structural instability in intermetallic Al₂Cu. This process is profound with decreasing separation of non-coplanar dislocations and increasing temperature and is likely to be …

A Rapid And Non-Invasive Method For Measuring The Peak Positive Pressure Of Hifu Fields By A Laser Beam, Hua Wang, Deping Zeng, Ziguang Chen, Zengtao Yang

Department of Mechanical and Materials Engineering: Faculty Publications

Based on the acousto-optic interaction, we propose a laser deflection method for rapidly, non-invasively and quantitatively measuring the peak positive pressure of HIFU fields. In the characterization of HIFU fields, the effect of nonlinear propagation is considered. The relation between the laser deflection length and the peak positive pressure is derived. Then the laser deflection method is assessed by comparing it with the hydrophone method. The experimental results show that the peak positive pressure measured by laser deflection method is little higher than that obtained by the hydrophone, confirming that they are in reasonable agreement. Considering that the peak pressure …

Benchmark Burnishing With Almen Strip For Surface Integrity, Z. Y. Liu, C. H. Fu, M. P. Sealy, Y. Zhao, Y. B. Guo

Department of Mechanical and Materials Engineering: Faculty Publications

Burnishing is a surface treatment process widely used in aerospace, navy and other industries to improve fatigue and corrosion resistance by introducing a compressive residual stress layer. The measurement of residual stress by XRD is expensive, time consuming, and tedious. This work presented a quick method to determine the residual stress by using Almen strips. Inspired by the application of Almen strips in shot peening, deflections of burnished Almen strips under different burnishing conditions were measured. It was found that the deflection of Almen strip reflects the magnitude and penetration depth into subsurface of induced stress. Higher burnishing force, smaller …

Effects Of Aspect Ratio On The Mode Couplings Of Thin-Film Bulk Acoustic Wave Resonators, Nian Li, Zhenghua Qian, Jiashi Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We studied mode couplings in thin film bulk acoustic wave resonators of a piezoelectric film on a dielectric layer operating with the fundamental thickness-extensional mode. A system of plate equations derived in our previous paper was used which includes the couplings to the unwanted in-plane extension, flexure, fundamental and second-order thickness shear modes. It was shown that the couplings depend strongly on the plate length/thickness ratio. For a relatively clean operating mode with weak couplings to unwanted modes, a series of discrete values of the plate length/thickness ratio should be avoided and these values were determined in the present paper. …

Clustering On Magnesium Surfaces – Formation And Diffusion Energies, Haijian Chu, Hanchen Huang, Jian Wang

Department of Mechanical and Materials Engineering: Faculty Publications

The formation and diffusion energies of atomic clusters on Mg surfaces determine the surface roughness and formation of faulted structure, which in turn affect the mechanical deformation of Mg. This paper reports first principles density function theory (DFT) based quantum mechanics calculation results of atomic clustering on the low energy surfaces {0001} and {1011}. In parallel, molecular statics calculations serve to test the validity of two interatomic potentials and to extend the scope of the DFT studies. On a {0001} surface, a compact cluster consisting of few than three atoms energetically prefers a facecentered- cubic stacking, to serve as a …

Review Of Sustainability Issues In Non-Traditional Machining Processes, Kamlakar Rajurkar, H. Hadidi, J. Pariti, G. C. Reddy

Department of Mechanical and Materials Engineering: Faculty Publications

Non-traditional machining processes (such as EDM and ECM) provide alternatives or sometimes the only alternative in generating highly complex 3-D features in very difficult-to -machine materials. This paper reviews recently published work on sustainability issues related to these processes. For example in Electrochemical machining (ECM) the effect of sludge generation and selection of dielectric in Electrodischarge machining (EDM) need to be investigated from the sustainability point of view. All processes need to be studied not only for resulting productivity and accuracy but also their environmental impact during product generation and usage. This paper addresses process mechanisms, surface integrity, sensing and …

Accommodation Of The Human Lens Capsule Using A Finite Element Model Based On Nonlinear Regionally Anisotropic Biomembranes, G. David, Ryan M. Pedrigi, J. D. Humphrey

Department of Mechanical and Materials Engineering: Faculty Publications

Accommodation of the eyes, the mechanism that allows humans to focus their vision on near objects, naturally diminishes with age via presbyopia. People who have undergone cataract surgery, using current surgical methods and artificial lens implants, are also left without the ability to accommodate. The process of accommodation is generally well known; however the specific mechanical details have not been adequately explained due to difficulties and consequences of performing in vivo studies. Most studies have modeled the mechanics of accommodation under assumptions of a linearly elastic, isotropic, homogenous lens and lens capsule. Recent experimental and numerical studies showed that the …

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

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing (FLSP) can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophobicity/-hydrophilicity. In this study, the subsurface microstructure of a series of mound-like FLSP structures formed on commercially pure titanium using five combinations of laser fluence and cumulative pulse counts was studied. Using a dual beam Scanning Electron Microscope with a Focused Ion Beam, the subsurface microstructure for each FLSP structure type was revealed by cross-sectioning. The microstructure of the mounds formed using the lowest fluence value consists of the original Ti grains. This is evidence that preferential laser …

Design And Field Testing Of A Combined Flaming And Cultivation Implement For Effective Weed Control, Brian D. Neilson, Chris A. Bruening, Strahinja Stepanovic, Avishek Datta, Stevan Z. Knezevic, George Gogos

Department of Mechanical and Materials Engineering: Faculty Publications

Flaming is a thermal weed control method that uses heat to control weeds within or between crop rows. Mechanical cultivation is another weed control method which undercuts weeds between crop rows, while leaving a strip of weeds within the crop row. A combination flamer/cultivator implement was designed to take advantage of the good qualities of both flaming and cultivation methods to provide a more consistent weed control than using either flaming or mechanical cultivation alone. Flaming hoods were designed in the spring of 2010 and retrofitted on an existing row crop cultivator. The flaming hoods were redesigned in the spring …

Robotic Surgical Devices, Systems, And Related Methods, Shane M. Farritor, Erik Mumm, Philip Chu, Nishant Kumar, Jason Dumpert, Yutaka Tsutano

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incorporated into robotic and/or in vivo medical devices. Certain embodiments include various modular medical devices for in vivo medical procedures.

Methods , Systems , And Devices Relating To Surgical End Effectors, Shane M. Farritor, Tom Fredrick, Joe Bartels

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incorporated into robotic and/or in vivo medical devices, and more specifically including end effectors that can be incorporated into such devices. Certain end effector embodiments include various vessel cautery devices that have rotational movement as well as cautery and cutting functions while maintaining a relatively compact structure. Other end effector embodiments include various end effector devices that have more than one end effector.

System For Imaging And Measuring Rail Deflection, Shane M. Farritor

Department of Mechanical and Materials Engineering: Faculty Publications

Devices, systems, and methods for imaging and measuring deflections in structures such as railroad rail are disclosed. One exemplary embodiment relates to a vision system having a high-speed, visible-light imaging camera and an evaluation unit configured for analyzing images from the camera to detect geometric variations in the structure. In a second example, additional sensors are used to identify the wheel location(s) in the same reference frame as the mea Surement system. In analyzing structures Such as railroad track rail, the imaging camera can be coupled to a moving rail vehicle and configured for generating images of the rail as …

Effect Of Random Ethylene Comonomer On Relaxation Of Flow-Induced Precursors In Isotactic Polypropylene, Benjamin Schammé, Eric Dargent, Lucia Fernandez-Ballester

Department of Mechanical and Materials Engineering: Faculty Publications

The effect of comonomer on structure and relaxation of flow-induced precursors was investigated in a series of isotactic polypropylene and random propylene−ethylene copolymers. The polymers were subjected to flow by fiber pulling and allowed to relax above their nominal melting temperature for specific times. The type of morphology developed after cooling revealed whether flow-induced precursors were still present or the melt had fully reequilibrated. Precursors were long-lived and, at fixed temperature, decayed significantly faster with higher ethylene content. The critical time for precursor relaxation followed an Arrhenius-type dependence with temperature. The apparent energy of activation for precursor dissolution decreased with …

Rapidly Solidified Rare-Earth Permanent Magnets: Processing, Properties, And Applications, Shampa Aich, Dillip K. Satapathy, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Rapidly solidified rare-earth-based permanent magnets are considered to have better potential as permanent magnets compared to the conventional bulk materials, which can be attributed to their improved microstructure and better magnetic properties compared to rare-earth magnets synthesized by the conventional (powder metallurgy) routes. The performance (quality) of these magnets depends on the thermodynamics and kinetics of the different processing routes, such as atomization, melt spinning, and melt extraction. Here, we review the various processing routes of rapidly solidified rare-earth permanent magnets and the related properties and applications. In the review, some specific alloy systems, such as Sm–Co-based alloys, Nd–Fe–B, and …

Biodegradable Elastic Nanofibrous Platforms With Integrated Flexible Heaters For On-Demand Drug Delivery, Ali Tamayol, Alireza Hassani Najafabadi, Pooria Mostafalu, Ali K. Yetisen, Mattia Commotto, Musab Aldhahri, Mohamed Shaaban Abdel-Wahab, Zeynab Izadi Najafabadi, Shahrzad Latifi, Mohsen Akbari, Nasim Annabi, Seok Hyun Yun, Adnan Memic, Mehmet R. Dokmeci, Ali Khademhosseini

Department of Mechanical and Materials Engineering: Faculty Publications

Delivery of drugs with controlled temporal profiles is essential for wound treatment and regenerative medicine applications. For example, bacterial infection is a key challenge in the treatment of chronic and deep wounds. Current treatment strategies are based on systemic administration of high doses of antibiotics, which result in side effects and drug resistance. On-demand delivery of drugs with controlled temporal profile is highly desirable. Here, we have developed thermally controllable, antibiotic-releasing nanofibrous sheets. Poly(glycerol sebacate)- poly(caprolactone) (PGS-PCL) blends were electrospun to form elastic polymeric sheets with fiber diameters ranging from 350 to 1100 nm and substrates with a tensile modulus …

Nondestructive Testing System Design For Biological Product Based On Vibration Signal Analysis Of Acceleration Sensor, Xiaohao Li, Tao Shen

Department of Mechanical and Materials Engineering: Faculty Publications

In order to reduce the disadvantages of current biological product quality testing methods, taking the quality testing in cocoon trade markets as an example, this paper has proposed a quality nondestructive testing method for biological products based on the analysis of vibration signal from acceleration sensors. According to the wavelet transformation analysis on the random vibration signal acquired from the acceleration sensor, the random vibration signal related to the silkworm chrysalis quality has been analyzed and reconstructed; then the characteristic values such as: mean value, variance, mean square root, waveform index, pulse factor, and so on of the quality signal …

Solution Nuclear Magnetic Resonance Spectroscopy On A Nanostructured Diamond Chip, P. Kehayias, A. Jarmola, N. Mosavian, I. Fescenko, F.M. Benito, A. Laraoui, J. Smits, L. Bougas, D. Budker, A. Neumann, S.R.J. Brueck, V.M. Acosta

Department of Mechanical and Materials Engineering: Faculty Publications

Sensors using nitrogen-vacancy centers in diamond are a promising tool for small-volume nuclear magnetic resonance (NMR) spectroscopy, but the limited sensitivity remains a challenge. Here we show nearly two orders of magnitude improvement in concentration sensitivity over previous nitrogen-vacancy and picoliter NMR studies. We demonstrate NMR spectroscopy of picoliter-volume solutions using a nanostructured diamond chip with dense, high-aspect-ratio nanogratings, enhancing the surface area by 15 times. The nanograting sidewalls are doped with nitrogen-vacancies located a few nanometers from the diamond surface to detect the NMR spectrum of roughly 1 pl of fluid lying within adjacent nanograting grooves. We perform 1H …

Micro/Nanostructures Formation By Femtosecond Laser Surface Processing On Amorphous And Polycrystalline Ni60nb40, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Meiyu Wang, Ryan Bell, Michael J. Lucis, Troy P. Anderson, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Faculty Publications

Femtosecond laser surface processing is a technology that can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophilicity/superhydrophobicity. In this study, two unique classes of surface structures, below surface growth (BSG) and above surface growth (ASG) mounds, were formed by femtosecond laser surface processing on amorphous and polycrystalline Ni₆₀Nb₄₀ with two different grain sizes. Cross sectional imaging of these mounds revealed thermal evidence of the unique formation processes for each class of surface structure. BSG mounds formed on all three substrates using the same laser parameters had similar surface …

Methods , Systems , And Devices Relating To Robotic Surgical Devices , End Effectors , And Controllers, Shane M. Farritor, Thomas Frederick, Joe Bartels, Eric Markvicka, Jack Mondry

Department of Mechanical and Materials Engineering: Faculty Publications

The various embodiments disclosed herein relate to improved robotic surgical systems, including robotic surgical devices having improved arm components and/or bio metric sensors, contact detection systems for robotic surgical devices, gross positioning systems and devices for use in robotic surgical systems, and improved external controllers and consoles.

The Effect Of A Powered Ankle Foot Orthosis On Walking In A Stroke Subject: A Case Study, Ali Pourghasem, Ismail Ebrahimi Takamjani, Mohammad Taghi Karimi, Mohammad Kamali, Mohammad Jannesari, Iman Salafian

Department of Mechanical and Materials Engineering: Faculty Publications

[Purpose] Standing and walking are impaired in stroke patients. Therefore, assisted devices are required to restore their walking abilities. The ankle foot orthosis with an external powered source is a new type of orthosis. The aim of this study was to evaluate the performance of a powered ankle foot orthosis compared with unpowered orthoses in a stroke patient.

[Subjects and Methods] A single stroke subject participated in this study. The subject was fitted with three types of ankle foot orthosis (powered, posterior leg spring, and carbon ankle foot orthoses). He was asked to walk with and without the three types …

Self-Patterning Gd Nano-Fibers In Mg-Gd Alloys, Yangxin Li, Jian Wang, Kaiguo Chen, Meiyue Shao, Yao Shen, Li Jin, Guo-Zhen Zhu

Department of Mechanical and Materials Engineering: Faculty Publications

Manipulating the shape and distribution of strengthening units, e.g. particles, fibers, and precipitates, in a bulk metal, has been a widely applied strategy of tailoring their mechanical properties. Here, we report self-assembled patterns of Gd nano-fibers in Mg-Gd alloys for the purpose of improving their strength and deformability. 1-nm Gd nano-fibers, with a 〈c〉-rod shape, are formed and hexagonally patterned in association with Gd segregations along dislocations that nucleated during hot extrusion. Such Gd-fiber patterns are able to regulate the relative activities of slips and twinning, as a result, overcome the inherent limitations in strength and ductility of Mg alloys. …

Single Site Robotc Device And Related Systems And Methods, Jack Mondry, Shane M. Farritor, Eric Markvicka, Thomas Frederick, Joseph Bartels

Department of Mechanical and Materials Engineering: Faculty Publications

The embodiments disclosed herein relate to various medical device components, including components that can be incor porated into robotic and/or in vivo medical devices. Certain embodiments include various medical devices for in vivo medical procedures.

Video Capture And Post-Processing Technique For Approximating 3d Projectile Trajectory, Chase M. Pfeifer, Judith M. Burnfield, Guilherme M. Cesar, Max H. Twedt, Jeff A. Hawks

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper we introduce a low-cost procedure and methodology for markerless projectile tracking in three-dimensional (3D) space. Understanding the 3D trajectory of an object in flight can often be essential in examining variables relating to launch and landing conditions. Many systems exist to track the 3D motion of projectiles but are often constrained by space or the type of object the system can recognize (Qualisys, Göteborg, Sweden; Vicon, Oxford, United Kingdom; Opti-Track, Corvallis, Oregon USA; Motion Analysis, Santa Rosa, California USA; Flight Scope, Orlando, Florida USA). These technologies can also be quite expensive, often costing hundreds of thousand dollars. …

Thermal Analysis Of Continuous And Patterned Multilayer Films In The Presence Of A Nanoscale Hot Spot, Jia-Yang Juang, Jinglin Zheng

Department of Mechanical and Materials Engineering: Faculty Publications

Thermal responses of multilayer films play essential roles in state-of-the-art electronic systems, such as photo/micro-electronic devices, data storage systems, and silicon-on-insulator transistors. In this paper, we focus on the thermal aspects of multilayer films in the presence of a nanoscale hot spot induced by near field laser heating. The problem is set up in the scenario of heat assisted magnetic recording (HAMR), the next-generation technology to overcome the data storage density limit imposed by superparamagnetism. We characterized thermal responses of both continuous and patterned multilayer media films using transient thermal modeling. We observed that material configurations, in particular, the thermal …

Case Study Of Quantifying Energy Loss Through Ceiling-Attic Recessed Lighting Fixtures Through 3d Numerical Simulation, Ri Na, Shengmao Lin, Zhigang Shen, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Abstract Air leakage through recessed lighting fixtures has been identified as a common issue that causes extra energy consumption in residential buildings. However, few quantitative studies in this area were found. As such, a preliminary assessment of the magnitude of this type of energy loss was conducted by using three-dimensional (3D) transient computational fluid dynamics (CFD) models. A hypothetical layout of recessed lighting fixtures was designed with boundary conditions of four different seasons, which were obtained from recorded roof/attic temperature data sets. The results of the study indicate that leakage of recessed lighting fixtures could be a significant channel of …

Compositionally Graded Bulk Heterojunction Devices And Methods Of Manufacturing The Same, Jinsong Huang, Zhengguo Xiao

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods are described to form compositionally graded BHJ structures utilizing solvent-fluxing techniques. In implementations, the systems and methods described herein involve a high boiling point additive, a solution of a polymer donor and an acceptor, a substrate material, a working solvent, and a flux solvent for formation of compositionally graded BHJ structures.

Bioink Properties Before, During And After 3d Bioprinting, Katja Hölzl, Shengmao Lin, Liesbeth Tytgat, Sandra Van Vlierberghe, Linxia Gu, Aleksandr Ovsianikov

Department of Mechanical and Materials Engineering: Faculty Publications

Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration …