Mechanical Engineering Commons^™

Measurement And Description Of Dynamics Required For In Vivo Surgical Robotics Via Kinematic Methods, Jacob G. Greenburg

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

With the goal of improved recovery times and reduced trauma to the patient there has been a substantial shift in the medical community’s demand for minimally invasive surgical (MIS) techniques. With the standardization of MIS becoming more commonplace in the medical field there are still many improvements that are desired. Traditional, manual methods of these surgeries require multiple incisions on the abdomen for the tools and instruments to be inserted. The more recent demand has been to localize the incisions into what is being referred to as a Laparoendoscopic Single-Site (LESS) surgery. Furthermore, the manual instruments that are commonly used …

Development Of A Controllable Polymer System Using Interpenetrating Networks, Emilie Bobo

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

My research partners and I have studied the possibility of building a material system with controllable properties using two interpenetrating polymer networks (IPNs). This study is part of a project to build a rapid prototyping system that allows for the printing of objects with predefined spatial distribution of properties, with the goal that property distributions are controlled though interactions at the molecular level.

One can change the properties of an IPN by adjusting the ratio of interpenetrating networks present in a given cured mixture. This is similar to how one obtains different shades of the color green by gradually changing …

Interface Properties Of Bio-Based Composites Of Polylactic Acid And Bamboo Fibers, Quentin Viel

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

Environmental impact plays an ever-increasing role in the industrial production of materials, and because of its importance, the scientific community is examining a wide variety of new materials that are more environmentally friendly. Bioplastics are characterized by the fact that the usual petrochemical resins (polypropylene, polyethylene etc.) are replaced by bio-sourced resins and the reinforcements (glass fibers, carbon fibers etc.) are replaced by natural fibers (bamboo, flax, cotton, etc.). Polylactic acid (PLA) is a biodegradable polymer that is increasingly used in biomedical applications and in packaging. Additionally, bamboo is a promising source of fibers that could be used as reinforcement. …

Design Of A Compliant Underactuated Robotic Finger With Coordinated Stiffness, Etienne Dessauw

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

The concept of underactuation has been previously developed in the robotic field for grasping applications. For these anthropomorphic grippers, the minimization of the number of input signals, or in other words underactuation, is the most expected characteristic. This method has become very popular in recent decades. Indeed, by minimizing the number of input signals, it minimizes the complexity of the system’s control and at the same time avoids increased weight and cost. The inconvenience of such a technique is that the design of this type of system remains a difficult task if the behavior of the underactuated set of joints …

Design Of Experimental Methods To Test The Performance Of Pads And Helmets Under Blast Loading Conditions, Kurtis Palu

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

Improvised explosive devices (IEDs) have become a primary weapon in conflicts against US and allied forces. Improvements in body armor and medicine have increased the survivability of such events. These factors have caused an increase in traumatic brain injury (TBI) and mild traumatic brain injury (mTBI) induced by primary blast waves. Injury mechanisms caused from primary blast waves are not clearly understood or defined. How primary blast waves interact with materials or between narrow gaps found between helmet pads is not known. Two novel test fixtures were developed to provide a basic understanding of these two issues.

The first fixture …

Mechanics Of Blast Loading On Post-Mortem Human And Surrogate Heads In The Study Of Traumatic Brain Injury (Tbi) Using Experimental And Computational Approaches, Shailesh Govind Ganpule

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

Blast induced neurotrauma (BINT) has been designated as the “signature injury” to warfighters in the recent military conflicts. The occurrence of traumatic brain injury (TBI) in blasts is controversial in the medical and scientific communities because the manifesting symptoms occur without visible injuries. Whether the primary blast waves alone can cause mechanical insult that is comparable to existing traumatic brain injury thresholds is still an open question, and this work is aimed to address this issue.

In the first part of this dissertation, mechanics of primary blast loading on Realistic Explosive Dummy (RED) head with and without helmets is studied …

Testing The Fuel Efficiency Of Tractors With Continuously Variable And Standard Geared Transmissions, Christopher N. Howard, Michael F. Kocher, Roger M. Hoy, Erin E. Blankenship

Department of Biological Systems Engineering: Papers and Publications

A John Deere 8295R IVT tractor with a continuously variable transmission (CVT) and a John Deere 8295R PowerShift (PST) tractor with a standard geared transmission (GT) were tested for fuel consumption at three different travel speeds with six different load levels applied per speed. The JD 8295R PST tractor was tested both at full throttle (FT) and shifted up two gears and throttled back (SUTB) to achieve the same travel speed as at full throttle. For each travel speed with each transmission mode, fuel consumption was determined to be linearly related to drawbar power. Linear regression analyses were performed, and …

Implementation Of Magnetic Resonance Elastography For The Investigation Of Traumatic Brain Injuries, Thomas Boulet

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

Magnetic resonance elastography (MRE) is a potentially transformative imaging modality allowing local and non-invasive measurement of biological tissue mechanical properties. It uses a specific phase contrast MR pulse sequence to measure induced vibratory motion in soft material, from which material properties can be estimated. Compared to other imaging techniques, MRE is able to detect tissue pathology at early stages by quantifying the changes in tissue stiffness associated with diseases. In an effort to develop the technique and improve its capabilities, two inversion algorithms were written to evaluate viscoelastic properties from the measured displacements fields. The first one was based on …

A Conductivity Testing System Coupled With A Tensile Testing Machine To Measure The Surface Properties Of Polymer Specimens, Nguyen T. Nguyen

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

Polymers play an essential role in our everyday life due to their employment in a widespread range of applications. Polymers are used in industries such as space, biomedical, electronics, etc. in which their electrical and mechanical properties are major aspects which need to be investigated prior to implementation. When subjected to mechanical stimulations, polymers may exhibit changes in electrical conductivity which can vary locally within the specimens, especially in those of conducting polymers. In mechanical investigations a tensile testing machine is used to understand polymers’ strength, elasticity or other mechanical properties. In electrical analysis, using a four-point probe to examine …

Peridynamic Models For Dynamic Brittle Fracture, Wenke Hu

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

Damage and failure in composite materials under dynamic loading has been extensively studied in experiments for several decades. Composite materials exhibit various damage and failure patterns under different loading rates, such as splitting and branching. Classical models cannot directly be applied to problems with discontinuous fields. A new nonlocal continuum model, peridynamics, has been proposed with the goal of solving dynamic fracture problems.

The J-integral has the physical significance of energy flow into the crack tip region. We present a rigorous derivation for the formulation of the J-integral in peridynamics using the crack infinitesimal virtual extension approach. We …

History Of The Biological Systems Engineering Program In Nebraska, University Of Nebraska-Lincoln, William E. Splinter

Tractor Testing Development and Research Documents

The Farm Machinery/Agricultural Engineering/Biological Systems Engineering program current and former faculty members at the University of Nebraska, as demonstrated here, has made a statewide, national, and worldwide impact on the efficient production of food. The quality of this recognition is evidenced best by peer professionals through recognized ASABE awards received by Nebraska alumni or professors. Since its inception in 1909 and until 2010, there have been 10 national presidents, 19 gold medal recipients and 33 named national award recipients. Currently there are 31 ASABE Fellows and two members of the National Academy of Engineering. This national recognition comes as a …

Newsletter 44 Issue 1 - Spring 2011 - Nuts And Bolts

Friends of the Larsen Tractor Museum

No abstract provided.

A Shock Tube Technique For Blast Wave Simulation And Studies Of Flow Structure Interactions In Shock Tube Blast Experiments, Nicholas N. Kleinschmit

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

Improvised explosive devices (IED’s) are widely used against US and allied forces fighting in Iraq and Afghanistan. Exposure to IED blast may cause blast-induced traumatic brain injury (bTBI). The injury mechanisms are however not well understood. A critical need in bTBI-related research is the ability to replicate the loading conditions of IED blast waves in a laboratory environment. In this work, experimental studies have been carried out to explore the use of the shock tube technique for generating air shock waves that mimic the temporal and spatial characteristics of free-field blast waves and to investigate the blast wave-test sample interactions …

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.

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

Newsletter 43 Issue 3 - Fall 2010 - Nuts And Bolts

Friends of the Larsen Tractor Museum

No abstract provided.

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

October 2009, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Agenda, minutes, treasurer report, director report, docent report, associate report, activities report, test lab report

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

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

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the …

Newsletters Of First 10 Years, Tractor Museum

Friends of the Larsen Tractor Museum

Newsletters distributed to supporters of the Larsen Tractor Museum.

1998 Spring Newsletter 1 - Non-profit Status, Dedication of Museum, Nebraska Tractor Test Law Beginnings

1998 Winter Newsletter 2 - First Annual Meeting, Library Established, State Fair Report, Winnepeg Plowing Contests

1999 Spring Newsletter 3 - Nebraska State Museum Affiliation, Fundraising Goals, Fuel Saving Devices in the 1920s

1999 Fall Newsletter 4 - Museum Studies Luis Vasquez, Tractor Raffle, Renovation Goals, Fundraising Goals, Annalyzing Tractor Test Results

1999 Winter Newsletter 5 - Mission Statement, Logo and Letterhead, Tractor Storage Facility, Bylaw Amendments, Hand Tool History, The Davidson Traction Dynamometer

2000 Spring …

Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.

Department of Engineering Mechanics: Faculty Publications

We introduce here adaptive refinement algorithms for the non-local method peridynamics, which was proposed (in J. Mech. Phys. Solids 2000; 48:175–209) as a reformulation of classical elasticity for discontinuities and long-range forces. We use scaling of the micromodulus and horizon and discuss the particular features of adaptivity in peridynamics for which multiscale modeling and grid refinement are closely connected. We discuss three types of numerical convergence for peridynamics and obtain uniform convergence to the classical solutions of static and dynamic elasticity problems in 1D in the limit of the horizon going to zero. Continuous micromoduli lead to optimal rates of …

Co-Op E3 Cockshutt 30 Restoration, Tractor Museum

Tractor Maintenance Repair and Restoration

Larsen Tractor Museum 2009 Restoration Project

Newsletters For The Larsen Tractor Museum, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

No abstract provided.

Lester Larsen: Progress Of Tractor Test Work 1946 -1956, Tractor Museum

Individuals Associated with the Nebraska Tractor Test

When Lester F. Larsen was hired as Engineer in Charge of the Nebraska Tractor Test, the laboratory had been inactive since 1941 due to World War II. Much of the test equipment was out of order and in need of repair. He kept a journal called the Progress of Tractor Test Work. This journal of day to day activities extended from 1946 through 1956.

Test 006: Case 10-20, Tractor Museum

Case-New Holland

Test 006: Case 10-20

All tractors tested at the Nebraska Tractor Test Laboratory were certified by their manufacturers as being stock model machines, conforming to specifications filed with the application for test. No special or high-test fuels were used except as recommended by the manufacturer as necessary.

All results within the official tractor test report were actually attained in tests and are without correction or allowances for friction, temperature, altitude, etc. The results were initially accomplished with the tractor in charge of skilled operators employed by the University.

Unless otherwise noted, each tractor was apparently in good condition at the …

Test007: Case 20-30, Tractor Museum

Case-New Holland

All tractors tested at the Nebraska Tractor Test Laboratory were certified by their manufacturers as being stock model machines, conforming to specifications filed with the application for test. No special or high-test fuels were used except as recommended by the manufacturer as necessary.

All results within the official tractor test report were actually attained in tests and are without correction or allowances for friction, temperature, altitude, etc. The results were initially accomplished with the tractor in charge of skilled operators employed by the University.

Unless otherwise noted, each tractor was apparently in good condition at the end of the testing …

Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …

Dec 2004, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Introductions Treasurer's Report Curator's Report