Mechanical Engineering Commons^™

Prediction Of In-Plane Stiffnesses And Thermomechanical Stresses In Cylindrical Composite Cross-Sections, Bryson M. Chan

Master's Theses

Accurate mechanical analysis of composite structures is necessary for the prediction of laminate behavior. Cylindrical composite tubes are a mainstay in many structural applications. The fundamental design of circular composite cross-sections necessitates the development of a comprehensive composite lamination theory. A new analytical method is developed to characterize the behavior of thin-walled composite cylindrical tubes using a modified plate theory. A generated numerical solver can predict properties such as axial stiffness, bending stiffness, layer stresses, and layer strains in composite tubes subjected to combined mechanical loading and thermal effects. The model accounts for the curvature by transforming and translating the …

A Single-Stage Passive Vibration Isolation System For Scanning Tunneling Microscopy, Toan T. Le

Master's Theses

Scanning Tunneling Microscopy (STM) uses quantum tunneling effect to study the surfaces of materials on an atomic scale. Since the probe of the microscope is on the order of nanometers away from the surface, the device is prone to noises due to vibrations from the surroundings. To minimize the random noises and floor vibrations, passive vibration isolation is a commonly used technique due to its low cost and simpler design compared to active vibration isolation, especially when the entire vibration isolation system (VIS) stays inside an Ultra High Vacuum (UHV) environment. This research aims to analyze and build a single-stage …

Design Of Structural Stand For High-Precision Optics Microscopy, Sara T. Novell

Master's Theses

Lawrence Livermore National Lab (LLNL) is home to the National Ignition Facility (NIF), the world’s largest and most energetic laser. Each of the 192 beamlines contains dozens of large optics, which require offline damage inspection using large, raster-scanning microscopes. The primary microscope used to measure and characterize the optical damage sites has a precision level of 1 µm. Mounted in a class 100 clean room with a raised tile floor, the microscope is supported by a steel stand that structurally connects the microscope to the concrete ground. Due to ambient vibrations experienced in the system, the microscope is only able …

Investigation Of Design, Manufacture, Analysis, And Test Of A Composite Connecting Rod Under Compression, Thomas Juhl Rohrbach

Master's Theses

Composite materials hold great potential for the replacement of traditional materials in machines utilized on a daily basis. One such example is within an engine block assembly where massive components inherently reduce the efficiency of the system they constitute. By replacing metal elements such as connecting rods, cylinder caps, or a crank shaft with composite alternatives, a significant increase in performance may be achieved with respect to mechanical strength, thermal stability, and durability, while also reducing mass. Exploration of this technology applied to a connecting rod geometry was investigated through a combination of process development, manufacturing, numerical analysis and testing. …

Subject-Specific Finite Element Predictions Of Knee Cartilage Pressure And Investigation Of Cartilage Material Models, Michael G. Rumery

Master's Theses

An estimated 27 million Americans suffer from osteoarthritis (OA). Symptomatic OA is often treated with total knee replacement, a procedure which is expected to increase in number by 673% from 2005 to 2030, and costs to perform total knee replacement surgeries exceeded $11 billion in 2005. Subject-specific modeling and finite element (FE) predictions are state-of-the-art computational methods for anatomically accurate predictions of joint tissue loads in surgical-planning and rehabilitation. Knee joint FE models have been used to predict in-vivo joint kinematics, loads, stresses and strains, and joint contact area and pressure. Abnormal cartilage contact pressure is considered a risk factor …

Rotordynamic Analysis Of Theoretical Models And Experimental Systems, Cameron R. Naugle

Master's Theses

This thesis is intended to provide fundamental information for the construction and

analysis of rotordynamic theoretical models, and their comparison the experimental

systems. Finite Element Method (FEM) is used to construct models using Timoshenko

beam elements with viscous and hysteretic internal damping. Eigenvalues

and eigenvectors of state space equations are used to perform stability analysis, produce

critical speed maps, and visualize mode shapes. Frequency domain analysis

of theoretical models is used to provide Bode diagrams and in experimental data

full spectrum cascade plots. Experimental and theoretical model analyses are used

to optimize the control algorithm for an Active Magnetic Bearing …

Manufacture Of Complex Geometry Component For Advanced Material Stiffness, David Russell Bydalek

Master's Theses

The manufacture, laminate design, and modeling of a part with complex geometry are explored. The ultimate goal of the research is to produce a model that accurately predicts part stiffness. This is validated with experimental results of composite parts, which refine material properties for use in a final prototype part model. The secondary goal of this project is to explore manufacturing methods for improved manufacturability of the complex part. The manufacturing portion of the thesis and feedback into material model has incorporated a senior project team to perform research on manufacturing and create composite part to be used for experimental …

Design And Analysis Of The Impact Diffusion Helmet Through A Finite Element Analysis Approach, Steven Paul Warnert

Master's Theses

By applying the finite element approach to the design and analysis of the impact diffusion helmet, many helmet configurations were able to be analyzed. Initially it was important to determine what design variables had an influence on the impact reducing abilities of the helmet design. The helmet was run through a series of Abaqus simulations that determined that a design with two oval shaped channels running along the length of the helmet was best. Next, these options were optimized to generate the helmet that produced the greatest impact reduction. The optimization simulations determined that a helmet that pushed the channels …

Continuum Modeling Of The Densification Of W-Ni-Fe During Selective Laser Sintering, Connor M. West

Master's Theses

The purpose of this thesis is to effectively model the time history of the temperature distribution during the selective laser sintering process and use this information to investigate the resulting relative density. The temperature is a critical parameter of the process because it directly effects the overall quality of the part. First, an efficient, affordable, and reliable simulation was developed within the finite element software, Abaqus. Next, the results from the simulations were compared to the experimental results performed by Wang et al. (2016). The FEA model consisted of a 3 layer simulation. Multiple simulations at various laser recipes were …

Analysis Of A Carbon Fiber Reinforced Polymer Impact Attenuator For A Formula Sae Vehicle Using Finite Element Analysis, John T. Rappolt

Master's Theses

The Hashin failure criteria and damage evolution model for laminated fiber reinforced polymers are explored. A series of tensile coupon finite element analyses are run to characterize the variables in the physical model as well as modeling techniques for using an explicit dynamic solver for a quasi-static problem. An attempt to validate the model on an axial tube crush is presented. It was found that fiber buckling was not occurring at the impactor-tube interface. Results and speculation as to why the failure initiation is incorrect are discussed. Lessons learned from the tube crush are applied successfully to the quasi-static Formula …

Development Of A Finite Element Model For Predicting The Impact Energy Absorbing Performance Of A Composite Structure, Matthew Lowell Roberts

Master's Theses

Because of their high strength-to-weight ratio, Fiber Reinforced Composite (FRC) materials are well suited for use in high performance racing applications where weight must be kept to a minimum. Formula SAE (FSAE) race cars are designed and built by college students, roughly following the model of a scaled down Formula One car. Strict regulations are placed on specific components of the car in the interest of equalizing competition and ensuring the safety of the drivers. Students are required to construct a survival cell (the chassis), which can resist large amounts of energy in the event of a crash, with an …

Poroelastic Finite Element Analysis Of A Heterogeneous Articular Cartilage Explant Under Dynamic Compression In Abaqus, Kelsey Kiyo Kam

Master's Theses

A poroelastic finite element model of a heterogeneous articular cartilage disc was

created to examine the tissue response to low amplitude (± 2% strain), low

frequency (0.1 Hz) dynamic unconfined compression (UCC). A strong correlation

has been made between the relative fluid velocity and stimulation of

glycosaminoglycan synthesis. A contour plot of the model shows the relative fluid

velocity during compression exceeds a trigger value of 0.25 μm/s at the radial

periphery. Dynamic UCC biochemical results have also reported a higher

glycosaminoglycan content in this region versus that of day 0 specimens. Fluid

velocity was also found not to be …

A Prediction Of The Acoustical Output Of A Golf Driver Head Using Finite Elements, Roger Sharpe

Master's Theses

A simulation was created using LS-DYNA® to determine the acoustical properties of a golf ball and golf driver head impact. LS-DYNA® has a coupled finite element analysis (FEA) and boundary element method (BEM) solver that uses the integral form of Helmholtz’s acoustic wave equation to deliver predicted sound pressure levels at predetermined acoustic points. Validation of the modeling was done on a simple plate donated by Titleist Golf. The plate was modeled and meshed using TrueGrid and impacted by a three layer golf ball model derived from “Tanka’s” paper on multilayered golf balls. The final converging model consisted of 10,900 …

Non-Linear Contact Analysis Of Meshing Gears, Chun Hung Lee

Master's Theses

Gear transmission systems are considered one of the critical aspects of vibration analysis, and it contains various potential faults such as misalignment, cracks, and noise. Therefore, it requires vibration monitoring to ensure the system is operating properly. Case mounted accelerometers are frequently used to monitor frequencies in a system. However, it is not a simple task to identify and interpret the acceleration data since there are many gear mesh frequencies present. One of the approaches utilized by researchers to perform gear diagnostic is Finite Element Modeling. This study focuses on stiffness cycle and meshing stiffness of non-linear quasi-static finite element …