Mechanical Engineering Commons^™

Contact-Resonance Atomic Force Microscopy For Viscoelasticity, P. A. Yuya, D. C. Hurley, Joseph A. Turner

Department of Engineering Mechanics: Faculty Publications

We present a quantitative method for determining the viscoelastic properties of materials with nanometer spatial resolution. The approach is based on the atomic force acoustic microscopy technique that involves the resonant frequencies of the atomic force microscopy cantilever when its tip is in contact with a sample surface. We derive expressions for the viscoelastic properties of the sample in terms of the cantilever frequency response and damping loss. We demonstrate the approach by obtaining experimental values for the storage and loss moduli of a poly(methyl methacrylate) film using a polystyrene sample as a reference material. Experimental techniques and system calibration …

Newsletters For The Larsen Tractor Museum, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

No abstract provided.

Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru

Department of Engineering Mechanics: Faculty Publications

In this paper a review of impact mechanics and high-energy absorbing materials is presented. We review different theoretical models (rigid-body dynamics, elastic, shock, and plastic wave propagation, and nonclassical or nonlocal models. and computational methods (finite-element, finite-difference, and mesh-free methods. used in impact mechanics. Some recent developments in numerical simulation of impact (e.g., peridynamics) and new design concepts proposed as high energy absorbing materials (lattice and truss structures, hybrid sandwich composites, metal foams, magnetorheological fluids, porous shape memory alloys. are discussed. Recent studies on experimental evaluation and constitutive modeling of strain rate-dependent polymer matrix composites are also presented. Impact damage …

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.

Finite Element Analysis Using Nonconforming Mesh, Ashok V. Kumar, Ravi Buria, Sanjeev Padmanabhan, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

A method for finite element analysis using a regular or structured grid is described that eliminates the need for generating conforming mesh for the geometry. The geometry of the domain is represented using implicit equations, which can be generated from traditional solid models. Solution structures are constructed using implicit equations such that the essential boundary conditions are satisfied exactly. This approach is used to solve boundary value problems arising in thermal and structural analysis. Convergence analysis is performed for several numerical examples and the results are compared with analytical and finite element analysis solutions to show that the method gives …

High-Impact, Energy-Absorbing Vehicle Barrier System : United States Patent 7,410,320 B2, Ronald K. Faller, Dean L. Sicking, John R. Rohde, John D. Reid, Robert W. Bielenberg, James C. Holloway, Karla A. Polivka

Department of Mechanical and Materials Engineering: Faculty Publications

A high-impact, energy-absorbing vehicle barrier system generally includes a substantially rigid outer containment wall coupled via strap assemblies with an energy-absorbing inner impact wall, and energy-absorbing cartridges strategically positioned between the impact wall and containment wall. The impact wall is constructed of a number of tubes coupled with one another to present a substantially smooth, unifonn surface to passing vehicles. The energy-absorbing cartridges generally consist of a foam member or a number of foam sheets which compress and crush between the containment wall and impact wall to absorb energy from an errant vehicle striking the face of the impact wall, …

Method And Apparatus For Noncontact Relative Rail Displacement, Track Modulus And Stiffness Measurement By A Moving Rail Vehicle: Us Patent No. Us 7,403,296 B2, Shane Farritor, Richard Arnold, Chris Norman

Department of Mechanical and Materials Engineering: Faculty Publications

An on-board, noncontact measurement system and method is disclosed for measuring track quality, vertical track stiffness and vertical track modulus for a portion of track underlying the rail vehicle. The system comprises first and second optical emitters mounted to the vehicle and configured to emit beams of light that are detectable on the underlying surface; a camera mounted to the vehicle for recording the distance between the beams of light as the vehicle travels along the surface, a mechanism for measuring the distance between the beams of light for a particular portion of the surface; and a mechanism for determining …

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 …

Phase-Field Modeling Of The Formation Of Lamellar Nanostructures In Diblock Copolymer Thin Films Under Inplanar Electric Fields, Xiang-Fa Wu, Yuris A. Dzenis

Department of Engineering Mechanics: Faculty Publications

Recent experiments show that external inplanar electric field can be employed to guide the molecular self-assembly in diblock copolymer (BCP) thin films to form lamellar nanostructures with potential applications in nanotechnology. We study this self-assembly process through a detailed coarse-grained phase separation modeling. During the process, the free energy of the BCP films is modeled as the Ginzburg-Landau free energy with nonlocal interaction and electrostatic coupling. The resulting Cahn-Hilliard (CH) equation is solved using an efficient semi-implicit Fourier-spectral algorithm. Numerical results show that the morphology of order parameter formed in either symmetric or asymmetric BCP thin films is strongly influenced …

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 …

Modeling Of Thermodynamically Coupled Reaction-Transport Systems, Yaşar Demirel

Yaşar Demirel Publications

Nonisothermal reaction-diffusion systems control the behavior of many transport and rate processes in physical, chemical and biological systems, such as pattern formation and chemical pumps. Considerable work has been published on mathematically coupled nonlinear differential equations by neglecting thermodynamic coupling between a chemical reaction and transport processes of mass and heat. This study presents the modeling of thermodynamically coupled system of a simple elementary chemical reaction with molecular heat and mass transport. The thermodynamic coupling refers that a flow occurs without or against its primary thermodynamic driving force, which may be a gradient of temperature or chemical potential or reaction …

Digital Media Agco Challenger, Nebraska Tractor Test Lab

Nebraska Tractor Tests

Images and videos of the 2008 Agco Challenger Tractor Testing.

Tractor Inventory, Nebraska Tractor Test Lab

Nebraska Tractor Tests

No abstract provided.

Free-Edge Stresses And Progressive Cracking In Surface Coatings Of Circular Torsion Bars, Xiang-Fa Wu, Yuris A. Dzenis, Kyle W. Strabala

Department of Engineering Mechanics: Faculty Publications

This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of complementary strain energy. Criterion for progressive cracking in the coating layer was established in sense of strain energy conservation, and the crack density is thereby estimated. Effects …

Subcritical And Supercritical Droplet Evaporation Within A Zero-Gravity Environment: Low Weber Number Relative Motion, Hongtao Zhang, Vasudevan Raghavan, George Gogos

Department of Mechanical and Materials Engineering: Faculty Publications

A validated comprehensive axisymmetric numerical model, which includes the high pressure transient effects, variable thermo-physical properties and inert species solubility in the liquid phase, has been employed to study the evaporation of moving n-heptane droplets within a zero-gravity nitrogen environment, for a wide range of ambient pressures and initial freestream velocities. At the high ambient temperature considered (1000 K), the evaporation constant increases with the ambient pressure. At low ambient pressure, the evaporation constant becomes almost a constant during the end of the lifetime. At high ambient pressures, the transient behavior is present throughout the droplet lifetime. The final penetration …

Experimental Characterization Of The Impact-Damage Tolerance Of A Cross-Ply Graphite-Fiber/Epoxy Laminate, Xiang-Fa Wu, Goutam Ghoushal, Mikhail Kartashov, Zuleyha Aslan, Joseph A. Turner, Yuris A. Dzenis

Xiang-Fa Wu Publications

In this study, the impact-damage tolerance of a graphite-fiber/epoxy composite laminate is studied by examining the correlation between the impact force and the resulting delamination area in the laminate. The cross-ply [0₂/90₂/0₂]_s composite laminate was made of thermosetting P7051S-20Q-1000 prepregs (Toray Composites America). A Hopkinson pressure bar (HPB) was employed to create the impulsive loading with varying magnitude. Transient impact force, displacement, impact power, and transmitted impact energy were calculated using the transient signals recorded from the strain gage mounted on the HPB. Impulsive loads with controllable magnitude were used to induce delamination …

Surgical Camera Robot: United States Patent No. Us 7,339,341 B2, Dmitry Oleynikov, Shane Farritor, Mark E. Rentschler, Stephen R. Platt, Jason Dumpert

Department of Mechanical and Materials Engineering: Faculty Publications

The present invention is a miniature camera robot which can be placed entirely within an open space such as an abdominal cavity. The instant camera robot has pan and tilt capabilities, an adjustable focus camera, and a support component for supporting the robot body. In particular embodiments, the camera robot further contains a light source for illumination and a handle to position the camera robot. A system and method for using the instant camera robot are also provided.

Influence Of Spatial Correlation Function On Attenuation Of Ultrasonic Waves In Two-Phase Materials, Dalie Liu, Joseph A. Turner

Department of Engineering Mechanics: Faculty Publications

Successful processing of materials by powder sintering relies on the creation of strong interparticle bonds. During certain critical stages of the sintering process, the medium may be modeled as two phases consisting of the particles and a surrounding matrix. Ultrasonic methods have been proposed as a potential tool for monitoring such sintering processes. Thus, an understanding of the propagation and scattering of elastic waves in two-phase solids is of fundamental importance to these monitoring techniques. In this article, expressions for the ultrasonic attenuations are developed based on the spatial statistics of the density and Lamé parameters of the material constituents …

Tractor Test 1920: New Holland Tt 75a, 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 …

Nebraska Summary: S673 New Holland T6030 Elite Pc, 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 …

Nebraska Summary: S651 Massey Ferguson 8680, 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 …

Test 1940: John Deere 9230 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 …

Conduction In Rectangular Plates With Boundary Temperatures Specified, James V. Beck, Neil T. Wright, A. Haji-Sheikh, Kevin D. Cole, Donald E. Amos

Department of Mechanical and Materials Engineering: Faculty Publications

Steady-state components of heat conduction solutions may have very slowly convergent series for temperatures and non-convergent heat fluxes for temperature boundary conditions. Previous papers have proposed methods to remove these convergence problems. However, even more effective procedures based on insights of Morse and Feshbach are given herein. In some cases it is possible to replace poorly-convergent or non-convergent series by closed-form algebraic solutions. Examples are given.

Test 1898a: Case Ih Magnum 215 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 …

Nebraska Summary: S721 New Holland T4030, 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 …

Nebraska Summary: S765 New Holland Td5030, 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 …

Test 1938a: Case Ih Dx 50 Also Farmall 50, 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 …

Thermodynamically Coupled Transport In Simple Catalytic Reactions, Yaşar Demirel

Yaşar Demirel Publications

Considerable work published on chemical reaction-diffusion systems investigates mainly mathematically coupled nonlinear differential equations. This study presents the modeling of a simple elementary chemical reaction with thermodynamically and mathematically coupled heat and mass transport with external mass and heat transfer resistances. The thermodynamic coupling refers that a flow occurs without or against its primary thermodynamic driving force, which may be a gradient of temperature or chemical potential. The modeling is based on the linear nonequilibrium thermodynamics approach and phenomenological equations by assuming that the system is in the vicinity of global equilibrium. This approach does not need detailed coupling mechanisms. …

Nebraska Summary: S648 Massey Ferguson 8650, 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 …

Computer Simulation Of Radio Frequency Heating Of Model Fruit Immersed In Water, Sohan Birla, Shaojin Wang, Juming Tang

Department of Engineering Mechanics: Faculty Publications

The present study investigated the effect of different factors on temperature distribution within a spherical object in a parallel plate radio frequency (RF) heating system. A finite element-computer simulation program - FEMLAB was used to solve the electromagnetic and Navier-Stoke equations for developing a model to study the effect of dielectric properties of a model fruit and its surrounding medium. The model fruit was prepared from 1% gellan gel for experimental validation of the simulation results. The results showed that spherically-shaped samples surrounded with air between RF electrodes and placed in the proximity of electrodes would not heat uniformly. Immersing …