Applied Mechanics Commons^™

Kolsky Bar Experiment For High-Rate Large Deformations Of Polycarbonate, Jason Gerald Vogeler

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

Polycarbonate (PC) is a tough, transparent engineering thermoplastic. Its impact strength and ability undergo large plastic deformations without shatter make PC an ideal protective material for impact-resilient eyewear, aircraft windows and transparent armor. A good understanding of the response of this material to large deformations at high strain rates is critical for its utilization in these applications. To this end, a striker-less Kolsky bar device is employed in this work for the needed material characterization. The apparatus allow impulsive torsion and/or compression loadings with pulse durations sufficiently long for the plastic flow behavior to develop fully. Three new testing techniques …

Heat Transfer Experiment: Energy Conservation, Ben Ward, Brett Wallace, Ryan Waltman

Mechanical Engineering

This proposal, prepared for the Mechanical Engineering Department by the HTEC design team will redesign and replace the current energy conversion lab that is inaccurate and out of date. The team will evaluate methods of energy conversion, specifically using braking systems, as well as existing labs in order to design an accurate and relatable experiment for this lab. The project team will work with Professor Kim Shollenberger in order to design an experiment that demonstrates energy conversion through the first law of thermodynamics while utilizing a common device that is practical in student’s lives. The final result of this project …

Design Of An Automatic Wood Trimming Machine, Van Ho, Nicholas Maskal, Andrew Rutland

Mechanical Engineering

This final design report, prepared for Sunrise Arts by the Cal Poly design team Mahogany Automation, details the year-long process in which the team of three engineering students designed and built an automated wooden -plank edge trimming machine that incorporates anti-jamming and continuous loading features. The team has examined current woodworking machines and features available on the industrial and commercial market, and used these as guides along with device requirements set by the project sponsor, Bruce Palmer. The focus has been on designing the simplest and most cost effective device that allows operators to make production runs of wooden slats …

Kinematic Synthesis Of Planar, Shape-Changing, Rigid Body Mechanisms For Design Profiles With Significant Differences In Arc Length, Shamsul A. Shamsudin, Andrew P. Murray, David H. Myszka, James P. Schmiedeler

Mechanical and Aerospace Engineering Faculty Publications

This paper presents a kinematic procedure to synthesize planar mechanisms capable of approximating a shape change defined by a general set of curves. These “morphing curves,” referred to as design profiles, differ from each other by a combination of displacement in the plane, shape variation, and notable differences in arc length. Where previous rigid-body shape-change work focused on mechanisms composed of rigid links and revolute joints to approximate curves of roughly equal arc length, this work introduces prismatic joints into the mechanisms in order to produce the different desired arc lengths. A method is presented to iteratively search along the …

Experimental And Finite Element Studies Of Shock Transmission, Eldon Jerry Goddard

UNLV Theses, Dissertations, Professional Papers, and Capstones

Composite materials are more widely used today in engineering products than ever before. Shock transmission in jointed composite sections needs to be investigated to understand the affect of composite materials on the dynamic response of the system. There exists limited published work on transient shock propagation through composite sections. The aim of this study is to analyze the transient behavior of joints in composite materials subjected to low impact loads and to develop a computational model that provides an improved physics based shock model. The jointed connection will be investigated experimentally and using Finite Element Analysis (FEA). The bolted joint …

Large-Displacement Lightweight Armor, Eric C. Clough

Master's Theses

Randomly entangled fibers forming loosely bound nonwoven structures are evaluated for use in lightweight armor applications. These materials sacrifice volumetric efficiency in order to realize a reduction in mass versus traditional armor materials, while maintaining equivalent ballistic performance. The primary material characterized, polyester fiberfill, is shown to have improved ballistic performance over control samples of monolithic polyester as well as 1095 steel sheets. The response of fiberfill is investigated at a variety of strain rates, from quasistatic to ballistic, under compression, tension, and shear deformation to elucidate mechanisms at work during ballistic defeat. Fiberfill’s primary mechanisms during loading are fiber …

Ultrasonic Propagation And Scattering In Pearlitic Steel, Hualong Du

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

Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for improving flaw detection in materials. In this dissertation, this approach is applied to inspection of railroad wheels. To improve the wear resistance, the tread surfaces of railroad wheels are usually quenched with water to increase the hardness. The pearlite phase of iron, characterized by alternating ferrite and cementite phases, is created by the quenching and the lamellar spacing within grains increases progressively from the quenched tread surface to deeper locations due to the non-uniform cooling rate. The quench depth is an important parameter governing the wheel …

Experimental Study On The Effect Of Air Flow On Soap Bubble Formation, John M. Davidson

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

Soap bubbles are a common interfacial fluid dynamics phenomenon having applications such as buoyant hollow spherical fillers and flow visualization of large scale airflows. In contrast to the dynamics of liquid drops in gas and gas bubbles in liquid, the dynamics of soap bubbles has not been well documented, possibly because soap bubbles have gas-liquid-gas interfaces. Having the thin-liquid-film interface seems to alter the characteristics of the bubble/drop creation process. Thus, the main objective of this study is to experimentally examine how airflow develops and interacts with the soap liquid film as the film stretches and finally collapses to pinch-off. …

Load Path Uncertainty In A Wood Structure And The Effect On Structural Reliability, Wenqi Wang, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

The roof truss bearing points of a light-framed wood house were instrumented with load cells. It was found that under dead load alone, symmetric and theoretically identical truss reactions have significant variation. A similar degree of reaction discrepancy was found under the application of uplift pressures caused by hurricane winds. Analysis revealed that the majority of this discrepancy is caused by inherent uncertainties in load path. Although uncertainties in load magnitude and material resistance are accounted for in design by use of appropriate load and resistance factors, load path is generally taken to be deterministic. In this study, load path …

Reliability Analysis Of Reinforced Concrete Columns Exposed To Fire, Christopher D. Eamon, Elin A. Jensen

Civil and Environmental Engineering Faculty Research Publications

A reliability analysis is conducted on reinforced concrete columns subjected to fire load. From an evaluation of load frequency of occurrence, load random variables are taken to be dead load, sustained live load, and fire temperature. Resistance is developed for axial capacity, with random variables taken as steel yield strength, concrete compressive strength, placement of reinforcement, and section width and height. A rational interaction model based on the Rankine approach is used to estimate column capacity as a function of fire exposure time. Various factors were considered in the analysis such as fire type, load ratio, reinforcement ratio, cover, concrete …

Active Dense Tensegrity Structure: A Novel Concept For Shape Morphing Structures, Zhiwei Wu, Thomas Siegmund

The Summer Undergraduate Research Fellowship (SURF) Symposium

Shape morphing is of relevance for advanced engineering systems such as future aerospace vehicles. Tensegrity structures, a structure comprised of a set of discontinuous compressed struts held together with a continuous web of tensioned cables, can function as the foundation of a shape morphing system (Keith et al, 2007). However, the classic tensegrity structures may not be ideal in all configurations because the space within the structure is not utilized. As an alternative, the present work proposes a dense tensegrity system as an assembly of cables carrying tensions only and polyhedral elements under compression only. An active dense tensegrity can …

Computer Simulation Study Of Slipper Lubrication In Hydraulic Machines, Jordyn B. Miller, Monika Ivantysynova

The Summer Undergraduate Research Fellowship (SURF) Symposium

Hydraulic pumps and motors are vital components used in many applications today. Specifically, the axial piston pump is important because it is reliable, relatively compact, and has a high horsepower-to-weight ratio. These features make this type of pump very advantageous in hydraulic systems. Maintaining proper lubrication between surfaces in an axial pump, such as the slipper and swashplate, is imperative in order to have smooth operation of the system and prevent metal-to-metal contact. The aim of this research is to find the optimal slipper design and fluid film thickness to simultaneously maintain a balanced pressure and decrease power loss in …

Crane Shaking Platform Design, Bixing Yan, Andrea Vacca

The Summer Undergraduate Research Fellowship (SURF) Symposium

Most of the control methodology of Mobile hydraulic crane is not as energy efficient as people think or want, and the desire to innovate novel, energy-efficient control strategy is the target of most hydraulic experts. To develop or test the control method under real road and off-road conditions, a platform that could simulate the movement and vibration of the crane truck is desired. To design and build the multi-operation platform, a design process includes brain storming, design selection, FEA (Fundamental Element Analysis), mechanical sizing, hydraulic sizing and Bill of Material is required and preferred. After going through all the steps …

Linear Controller Establishment For Displacement-Control Pump Switching System, Yangqiao Zheng, Monika Ivantysynova

The Summer Undergraduate Research Fellowship (SURF) Symposium

Displacement Controlled (DC) hydraulics system is booming recently due to its high efficiency and accurate controllability, while the surplus numbers of pumps restrains its further development. DC pump switch technique is a promising application to reduce the number of pumps as well as the cost products to promote DC hydraulics technique. It is necessary to support an innovative DC hydraulic pump switching system with a controller which would allow rapid and accurate estimation and adaptation for all the parameters, like pressures and velocities, in the system. Dynamics and Hydraulics characteristics have initially been investigated for a simplified DC pump switching …

An Investigation Of Phase-Change Effects During Rapid Compression Machine Experiments, Colin Banyon

Master's Theses (2009 -)

Rapid compression machines (RCMs) are well characterized laboratory scale devices capable of achieving internal combustion (IC) engine relevant thermodynamic environments. These machines are often used to collect ignition delay times as targets for gas-phase chemical kinetic fuel autoigntion models. Modern RCMs utilize creviced piston(s) to improve charge homogeneity and allow for an adequate validation of detailed chemistry mechanisms against experiments using computationally efficient, homogeneous reactor models (HRMs). Conventionally, experiments are preformed by introducing a premixed gas of fuel + oxidizer + diluent into the machine, which is compressed volumetrically via a piston. Experiments investigating low-vapor pressure fuels (e.g. diesels, biodiesels, …

Enhanced Reducibility And Conductivity Of Na/K-Doped Srti0.8Nb0.2O3, Guoliang Xiao, Sirikanda Nuansaeng, Lei Zhang, Suwit Suthirakun, Andreas Heyden, Hans-Conrad Zur Loye, Fanglin Chen

Faculty Publications

Donor and acceptor co-doped SrTiO₃ materials have shown interesting features in their conductivity and reducibility. In this work, 10 mol% Na⁺ or K⁺ as acceptor dopants have been introduced into the A-site of donor-doped strontium titanate, SrTi_0.8Nb_0.2O₃, and the doping impact on their properties has been studied. By doping with Na or K, the sinterability of SrTi_0.8Nb_0.2O₃ in reducing atmospheres has been improved. Na_0.1Sr_0.9Ti_0.8Nb_0.2O₃ and K_0.1Sr_0.9Ti_0.8Nb_0.2O₃ show metallic …

The Mechanics Of Intracranial Loading During Blast And Blunt Impacts: Experimental And Numerical Studies, Veera Selvan Kuppuswamy

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

Head injuries in an explosion occur as a result of a sudden pressure changes (e.g. shock-blast) in the atmosphere (primary injury), high velocity impacts of debris (secondary injury) and people being thrown against the solid objects (tertiary injury) in the field. In this thesis, experimental and numerical approaches are used to delineate the intracranial loading mechanics of both primary (blast) and tertiary injuries (blunt).

The blast induced head injuries are simulated using a fluid-filled cylinder. This simplified model represents the head-brain complex and the model is subjected to a blast with the Friedlander waveform type of loading. We measured the …

Propagation Of Thermo-Mechanical Waves In Deforming Nonlinear Viscoelastic Bodies, Lili Zhang

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

This work studies the propagation of thermo-mechanical disturbances in bodies made of viscoelastic materials that might already be loaded such that they are undergoing large inhomogeneous time varying deformations. In the process of this study we develop the general equations governing the thermo-mechanical motion of such disturbances and ones for internally constrained systems, provide the general structure of the solution, match the solution to existing results for the special case of time harmonic plane waves in elastic bodies and in viscoelastic bodies under constant homogenous loading, and consider some special applications.

The results of this work should have applications in …

An Applied Numerical Simulation Of Entrained-Flow Coal Gasification With Improved Sub-Models, Xijia Lu

LSU New Orleans Theses and Dissertations

The United States holds the world's largest estimated reserves of coal and is also a net exporter of it. Coal gasification provides a cleaner way to utilize coal than directly burning it. Gasification is an incomplete oxidation process that converts various carbon-based feedstocks into clean synthetic gas (syngas), which can be used to produce electricity and mechanical power with significantly reduced emissions. Syngas can also be used as feedstock for making chemicals and various materials.

A Computational Fluid Dynamics (CFD) scheme has been used to simulate the gasification process for many years. However, many sub-models still need to be developed …

Relaxation Of Shear-Induced Precursors In Isotactic Polypropylene And Random Propylene–Ethylene Copolymers, Benjamin Schammé

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

Flow induced crystallization (FIC) has a large impact on kinetics and morphology of semicrystalline polymers, and can therefore drastically change final properties such as dimensional and thermal stability, modulus and strength. Processing of polymers usually involves flow, so it is important to understand the mechanism of FIC. It is known that oriented precursors formed during flow are the key to FIC but they are not yet well understood. In this study, flow induced precursors are investigated by examining their relaxation, and the effect of comonomer is probed.

Using a commercial isotactic polypropylene and random propylene-ethylene copolymers, a fiber pull-out technique …