Engineering Commons^™

Improved Mobile Wireless In Vivo Surgical Robots: Modular Design, Experimental Results, And Analysis, Jeff Hawks

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

Laparoscopic surgery results in superior patient outcomes as measured by less painful recovery and an earlier return to functional health compared to conventional open surgery. However, the difficulty of manipulating laparoscopic tools from outside the patient’s body generally limits these benefits to patients undergoing relatively simple procedures. The use of miniature in vivo robots that fit entirely inside the peritoneal cavity represents a novel approach to laparoscopic surgery. These robots enable more complex laparoscopic procedures, increasing the number of patients that benefit from laparoscopic surgery.

This thesis describes recent work focused on developing a modular wireless mobile platform that can …

Anomalous Loss Of Toughness Of Work Toughened Polycarbonate, Shawn E. Meagher

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Glassy polymers such as polycarbonate (PC) can be toughened through compressive plastic deformation. The increase in toughness is substantial, showing as much as a fifteen fold increase in the amount of dissipated energy during failure for samples compressed to 50% plastic strain. This toughness increase can be reversed through thermal aging at temperatures below the glass transition temperature (T_g = 147°C).

The combined effect of plastic compression and thermal aging has been studied using Charpy, Single Edge Notch Bending (SENB), and Compact Tension (CT) tests. The tests mapped the response of samples cut along different orientations relative to the …

Development And Characterization Of Shock Tubes For Laboratory Scale Blast Wave Simulation, Aaron D. Holmberg

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

The prevalence of traumatic brain injury (TBI) in American soldiers exposed to a blast wave has created an urgent need to better understand the effects of blast wave insult to the head. Developing techniques that can experimentally simulate well controlled blast waves in a laboratory environment is a critical component of the research efforts towards this goal. For this work, a 4-in. cylindrical uniform shock tube and a nonuniform shock tube combining a 4-in. cylindrical gas driver with a 9-in. square driven section have been developed. The hosting laboratory, gas handling system, multichannel data acquisition systems, and the related network …

Hybrid Nanomanufacturing Process For High-Rate Polymer Nanofiber Production, Chad T. Peterson

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Nanotechnology and nanomaterials have the potential to revolutionize existing and create entirely new industries. Unique physical, mechanical, chemical, and biological properties of nanomaterials have been extensively documented in the last two decades. However, most nanomaterials are discontinuous in nature, creating problems with their processing and manipulation into devices and raising health concerns. Continuous nanofibers represent an emerging class of nanomaterials with critical advantages to applications. Continuous nanofibers are readily produced by electrospinning process comprising spinning polymer solutions in high electric fields. Electrospinning is a very economic top-down nanomanufacturing process that has been used to produce ultrafine continuous nanofibers from several …

Bulging Factors In Geometrically Nonlinear Cracked Laminated Shell Structure Under Dynamic Internal Pressure, Nitin B. Ingale Mr.

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

This thesis is about the investigation of the geometrically nonlinear responses and bulging factors of cracked laminated composite cylindrical shell structures subjected to internal pressure. Hybrid strain based three-node flat triangular shell elements, developed by To and Wang were used.

Effects of dynamic responses of various numbers of layers and their angle arrangements of cracked cylindrical shell structures clamped at both ends are analyzed and studied. Bulging factors based on the concept of equivalent Young’s modulus of elasticity are found and compared with single and multiple layer composite cylindrical shell structures.

Finally, bulging factors for similar laminated composite cylindrical shells …

Nanomanufacturing And Analysis Of Novel Integrated Continuous Nanofibers, John E. Hannappel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Complex nanostructured materials have great potential for applications in many areas of nanotechnology. This potential is being unlocked by precise control of their nanoscale architecture and properties. Most current methods of creating these nanostructures are expensive and difficult to control, with the majority of techniques resulting in non-continuous nanostructures and nanoparticles. Electrospinning is an economic nanomanufacturing method resulting in continuous nanofibers. The method consists of spinning fiber-forming liquids in high electric fields. In this work, a modified electrospinning process was analyzed. The process utilized two concentric liquids that resulted in integrated continuous hollow or composite nanofibers. A new adjustable co-axial …

Electromagnetic Field Calculations For Microlens Optical Systems, Jian Wang

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

Microlenses are becoming more widely used in modern optical equipment. When the microlens diameter is comparable with the incident electromagnetic illumination wavelength, diffraction effects through the microlens aperture dominate and significantly affect the microlens optical properties leading to differences from that predicted by ordinary geometrical optics theory. In this work, the continuous-profile symmetrical biconvex microlens is selected for investigation. Its optical properties, with both monochromatic plane wave and TEM00 mode Gaussian beam illumination, are studied using the full-field Separation-of-Variables method (SVM) in the oblate spheroidal coordinate system by calculating the electromagnetic field distributions inside of and adjacent to the microlens. …

The Relation Between The Arterial Stress And Restenosis Rate After Coronary Stenting, Linxia Gu, Shijia Zhao, Aswini K. Muttyam, James M. Hammel

Department of Mechanical and Materials Engineering: Faculty Publications

Two commercially available stents (the Palmaz–Schatz (PS) and S670 stents) with reported high and low restenosis rates, respectively, have been investigated in this paper. Finite element models simulating the stent, plaque, and artery interactions in 3 mm stenosed right coronary arteries were developed. These models were used to determine the stress field in artery walls after stent implantation. The material properties of porcine arteries were measured and implemented in the numerical models. The stress concentration induced in the artery by the PS stent was found to be more than double that of the S670 stent. It demonstrated a good correlation …

Stochastic Optimal Control In Nonlinear Systems, Celestin Nkundineza

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

Stochastic control is an important area of research in engineering systems that undergo disturbances. Controlling individual states in such systems is critical. The present investigation is concerned with the application of the stochastic optimal control strategy developed by To (2010) and its implementation as well as providing computed results of linear and nonlinear systems under stationary and nonstationary random excitations. In the strategy the feedback matrix is designed based on the achievement of the objectives for individual states in the system through the application of the Lyapunov equation for the system. Each diagonal element in the gain or associated gain …

Newsletter 42 Issue 2 - Summer 2010 - Nuts And Bolts, Tractor Museum

Friends of the Larsen Tractor Museum

No abstract provided.

Measurement, Simulation, And Analysis Of The Mechanical Response Of Railroad Track, Curt J. Greisen

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

Increased railroad traffic volumes, speeds, and axle loads have created a need to better measure track quality. Previous research has indicated that the vertical track deflection provides a meaningful indicator of track integrity. The measured deflection can be related to the bending stresses in the rail as well as characterize the mechanical response of the track.

This investigation summarizes the simulation, analysis and development of a measurement system at the University of Nebraska (UNL) to measure vertical track deflection in real-time from a car moving at revenue speeds. The UNL system operates continuously over long distances and in revenue service. …

Fracture Of Bone Using Microindentation, Séverine Vennin

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Osteoporosis is a current disease which is especially of concern to post-menopausal women. It is characterized by a decrease of bone density and an increase in the risk of fracture. Interest in the fracture mechanisms with respect to the underlying biological structure of the bone is of great interest to researchers in this field. In this thesis, a new method based on microindentation on rat femurs was developed to determine the relation between the viscoelastic and the fracture properties of bone. The main goal is to measure the viscoelastic properties by using a dynamic mechanical analysis indentation method and then …

Diffuse Ultrasonic Scattering In Advanced Composites, Christer Stenström

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Non destructive testing (NDT) is a noninvasive technique used for characterization and inspection of the integrity of objects. NDT is an important tool for research, manufacturing monitoring and in-service inspections. Ultrasonic testing is the most used NDT technique, which for advanced composites can identify several types of defects, like delamination and interlaminar cracks. Diffuse ultrasonics has shown to be able to extract information at the microscale of metals and therefore it is believed it can be used for advanced composites to extract microstructural information, i.e. at the level of fibers.

In this thesis, diffuse ultrasonic methods, together with spatial variance …

Characterization, Modeling, And Consequences Of The Development During Plastic Flow Of Large Anisotropy In The Wave-Speeds, Quentin Fichot

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

There is a substantial change in the anisotropy of some glassy polymers when they are subjected to large plastic deformations. The most pronounced case probably is seen in polycarbonate (PC), which is a tough thermoplastic used for many structural applications, including as a protective transparent armor for such applications as bulletproof glass. This development of anisotropy in the elastic response can be of the same order as the applied strains, and, therefore, becomes important in problems that show substantial plastic flow. In spite of this, this characteristic of glassy polymers has not been included in the current models. We propose …

Time Dependence Of Self-Assembly Process For The Formation Of Inorganic-Organic Hybrid Nanolayers, Alexandre Dhôtel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

There is increasing interest in self-assembled materials for energy storage, flexible electronics and hydrophobic barriers. Inorganic/organic hybrid thin films and especially organosilane-based coatings already have demonstrated their ability to achieve those goals. However, some fundamental points of their formation process by molecular self-assembly remain unexplained. Although the literature widely reports the effect of temperature on the final nanostructure, until now, no one has taken into account the importance of time during their synthesis.

The main objective of this study was to improve and complete the understanding of mechanisms responsible for the self-organization of organic/inorganic molecules into a highly ordered, layered …

Material Modeling And Analysis For The Development Of A Realistic Blast Headform, S. G. M. Hossain

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

Blast traumatic brain injury (BTBI) has become an important topic of study because of the increase of such incidents, especially due to the recent growth of improvised explosive devices (IEDs). This thesis discusses a project in which laboratory testing of BTBI was made possible by performing blast loading on experimental models simulating the human head. Three versions of experimental models were prepared – one having a simple geometry and the other two having geometry similar to a human head. For developing the head models, three important parts of the head were considered for material modeling and analysis – the skin, …

Global Competence: Determination Of Its Importance For Engineers Working In A Global Environment, Gregg M. Warnick

Department of Educational Administration: Dissertations, Theses, and Student Research

We live and work in a world that is even more interconnected and interdependent than ever before. Engineers must now not only develop technical engineering competence, but must also develop additional skills and competencies including global competence to obtain success within a global engineering environment.

The purpose of this study was to determine whether multinational companies considered global competence an important skill in mechanical engineering graduates when making hiring decisions. The study was an exploratory study that utilized an extensive literature review to identify eight global competencies for engineering success within a global environment and also included a survey instrument …

Structural And Magnetic Properties Of Neodymium - Iron - Boron Clusters, Jeremy J. Anderson

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

Using inert gas condensation techniques the properties of sputtered neodymium-iron-born clusters were investigated. A D.C. magnetron sputtering source created vaporous Nd-Fe-B which was then condensed into clusters and deposited onto silicon substrates. A composite target of Nd-Fe-B discs on an iron plate and a composite target of Nd-(Fe-Co)-B were utilized to create clusters. The clusters were coated with a carbon layer through R.F. sputtering to prevent oxidation.

Samples were investigated in the TEM and showed a size distribution with an average particle diameter of 8.11 nm. The clusters, upon deposition, were amorphous as indicated by diffuse diffraction patterns obtained through …

Design And Analysis Of Multifunctional Robot For Notes, Akiko Nakamura

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

The elimination of all external incisions is an important step in reducing the invasiveness of surgical procedures. Natural Orifice Translumenal Endoscopic Surgery (NOTES) is an incision-less surgery and provides explicit benefits such as reducing patient trauma and shortening recovery time. However, technological difficulties impede the widespread utilization of the NOTES method. A novel robotic tool has been developed, which makes NOTES procedures feasible by using multiple interchangeable tool tips.

The robotic tool has the capability of entering the body cavity through an orifice or a single incision using a flexible articulated positioning mechanism and once inserted is not constrained by …

Mechanical Testing Device For Viscoelastic Biomaterials, Jeff D. Berg

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

Nearly all biologic tissues exhibit viscoelastic behavior. This behavior is characterized by hysteresis in the response of the material to load or strain. This information can be utilized in extrapolation of life expectancy of vascular implant materials including native tissues and synthetic materials. This behavior is exhibited in many engineering materials as well such as the polymers PTFE, polyamide, polyethylene, etc. While procedures have been developed for evaluating the engineering polymers the techniques for biologic tissues are not as mature. There are multiple reasons for this. A major one is a cultural divide between the medical and engineering communities. Biomedical …

Steady-State Green’S Function Solution For Moving Media With Axial Conduction, A. Haji-Sheikh, J. V. Beck, Kevin D. Cole

Department of Mechanical and Materials Engineering: Faculty Publications

The objective of this presentation is the development of a generalized steady-state Green’s function solution to study the temperature field in moving bodies. This type of solution permits the inclusion of different nonhomogeneous boundary conditions, volumetric heat sources, and possible position-dependent thermophysical properties. Although the mathematical formulation is for moving solids, it can be used to study the heat transfer in a moving fluid with a non-uniform velocity distribution passing through a micro-channel or fluid-saturated porous ducts. Additionally, this presentation includes the application of this Green’s function solution to acquire numerical information for selected examples to further illustrate the numerical …

Adaptive Cutting Force Control For Process Stability Of Micro Ultrasonic Machining, Ala'a M. Al-Okaily

Department of Industrial and Management Systems Engineering: Dissertations, Theses, and Student Research

The growing demand for miniaturized products motivates the advancement in micromanufacturing processes research and development. Micro Ultrasonic Machining (Micro USM) is a downscaled version of a macro USM process that is developed to fabricate complex features in chemically inert, nonconductive, hard, brittle materials such as quartz, glass, and ceramics. These materials have many applications in various fields such as optics, electronics, MEMS, and biotechnology. The micro USM process stability is hard to accomplish, because it is highly influenced by the accuracy of the machining system and the variation of the process control parameters. The repeatability of micro USM machined features …

Eutectic Solidification Limits And Mechanical Properties Of Sm-Co-Fe Alloys, Wendy Ann Wagner

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

Creating a permanent magnet with a higher energy product than existing materials is attractive in order to optimize magnetic performance. The eutectic microstructure of Sm-Co alloys is attractive for magnets since primary rods of the Co-phase can act as a soft magnetic phase in the matrix of the Sm₂Co₁₇ hard magnetic phase, forming two-phase magnets. Fe replacement in Sm-Co alloys provides an opportunity to maintain the desirable eutectic microstructure of Co_1-xFe_x rods embedded in a Sm₂(Co_1-xFe_x)₁₇ matrix while improving the magnetization and lowering the cost. The purpose …

Mechanical Milling Of Co-Rich Melt-Spun Sm-Co Alloys, Farhad Reza Golkar-Fard

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

MECHANICAL MILLING OF CO-RICH MELT-SPUN SM-CO ALLOYS Farhad Reza Golkar-Fard, M.S UNIVERSITY OF NEBRASKA, 2010 Advisor: Jeffrey E. Shield Rare-earth, high-energy permanent magnets are currently the best performing permanent magnets used today. The discovery of single domain magnetism in 1950’s ultimately led to the development of nanocomposite magnets which had superior magnetic properties. Previous work has shown that mechanical milling (MM) effectively generates nanoscale structures in Sm-Co-based alloys. MM of more Co-rich, melt-spun Sm-Co alloys (up to the eutectic composition) and the role of initial structure on the milling behavior were investigated.

Sm-Co alloys with compositions of Sm_10.5Co …

Coupled Dem-Fem For Dynamic Analysis Of Granular Systems In Bending, Kitti Rattanadit

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Characterizing the dynamic behavior of granular materials is one of the great challenges in the mechanics of granular matter. Methods for evaluating the mechanical properties of granular matter have applications in a variety of industries, mining and geotechnical activities, defense and military operations. A coupled 2D Discrete Element Method-Finite Element Method (DEM-FEM) code, called "BobKit", is developed and implemented for analyzing the behavior of a 2D granular layer on top of an elastic beam under deforming (quasi-static) or vibrating (dynamic) of the beam. The explicit time-integration dynamic code is used to simulate quasi-static and dynamic bending of the granular layer …

A Concise Model Of 3x7 Wire Rope Used In Cable Guardrail Systems, Cody S. Stolle

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

Wire rope is a versatile, flexible, high-strength member that is used in many mechanical systems. However, due to the complexity of wire rope, analytical investigations have been relatively limited. Previous attempts to create simplified models of wire rope were not validated with physical testing and used a cumbersome beam-and-shell or beam-and-solid method for simulating the wire rope. An improved LS-DYNA model of 19-mm diameter 3x7 wire rope commonly used in roadside cable guardrail installations has been developed. A Belytschko-Schwer beam element was selected along with material *MAT_166. Since wire rope displays internal damping due to friction of strands and wires, …

Newsletter 41 Issue 1 - Spring 2010 - Nuts And Bolts, Larsen Tractor Museum

Friends of the Larsen Tractor Museum

No abstract provided.

Nuts And Bolts - Ltm Newsletters, Tractor Museum

Friends of the Larsen Tractor Museum

Newsletters published by the Larsen Tractor Museum in 2010

Where do we grow from here? by Curt McConnell, editor

Chris Ford has big plans for small groups in 2010 by Curt McConnell, editor

News from Exhibits by Luis Vasquez, chair of collections committee

Engine comes together as Co-Op E3 progresses by Curt McConnell

Description of our Sound Level Measuring and Analyzing Equipment by Lou Leviticus

Development of conservation tillage methods by Bill Splinter, museum director

Curator's Report by Lou Leviticus

Associate Report by Jeremy Steele, museum associate

Obituary Note - Robert Kleis

Steady-Periodic Heating In Parallel-Plate Microchannel Flow With Participating Walls, Kevin D. Cole

Department of Mechanical and Materials Engineering: Faculty Publications

Simulations are presented for thermal sensing of steady laminar flow in a parallel-plate microchannel. Steady-periodic heating is introduced at the channel wall and temperatures are reported at upstream and downstream locations to represent temperature sensors. Exact analytical expressions for the temperature are given in the form of integrals, and numerical values are found by quadrature. Because axial conduction is prominent, there is a well-defined measurable flow range associated with each thermal-sensor geometry. Various fluid-flow rates, heating frequencies, sensor locations, and wall properties are explored. The results are given as a design correlation which shows the extent to which a given …

Newsletter 43 Issue 3 - Fall 2010 - Nuts And Bolts

Friends of the Larsen Tractor Museum

No abstract provided.