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 …

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 …

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. …

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 …

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, …

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. …

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 …

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 …

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, …