Applied Mechanics Commons^™

Experimental And Numerical Study On The Influence Of Carbon Fiber Reinforcement On The In-Plane Compressive Properties Of 3d Printed Hexagonal Honeycomb Core Structures, Deon Wallace

All Theses

There is difficulty with numerically replicating the behavior of composite honeycomb core structures numerically due to the trouble of gathering material properties from a hollow structure. Also, complex part geometries and carbon fiber reinforcement strategies can lead to unwanted structural weaknesses and variance in material properties that may not be reflected in numerical analysis when the part is additively manufactured. In this study, edgewise compressive testing is used to characterize the mechanical behavior and performance characteristics of these structures. The experimental results indicate an increase in the Young’s moduli of the honeycomb core structures as carbon fiber concentration increases. However, …

Predicting Long-Term Creep Behavior Using Short-Term Stress Relaxation Data In Expanded Polyethylene Foam, Andrew M. Seelig

All Theses

Closed cell expanded polyethylene (EPE) foams are widely used for protective packaging due to their high energy absorption properties and recyclability. However, these foams can be subjected to sustained compressive stresses (13.78 - 36.20 kPa), depending on density and application, leading to time-dependent deformation (creep). Creep reduces cushioning performance, making its understanding critical for effective protective packaging. Two standards, ASTM D3575 and ASTM D2221, define methods for conducting compressive creep tests on foam materials, with test durations extending up to 1000 hours. Accelerated methods such as Time Temperature Superposition (TTS) and the Stepped Isostress Method (SSM) have been explored for …

Residential Hvac Installation Faults: Field Prevalence, Drivers, And Energy Impacts, Seyed Ali Rooholghodos

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Faults in residential comfort systems can have detrimental effects on the performance of the system, reducing the energy efficiency, affecting indoor comfort, and shortening equipment lifespan. Many of the faults occur at installation. However, there has not previously been a systematic and nationally representative study to indicate the prevalence of the faults, meaning the distribution of faults by fault type and fault intensity. Understanding true fault prevalence is essential to be able to identify derivers, and to assess the incremental electricity consumption of the new installation systems.

This study presents on-site data from 341 new central cooling systems—air conditioners and …

In-Field Tractor Operational Load Profile Generation In Support Of Advanced Tractor Testing In Mixedmode Power, Andrew Donesky

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This dissertation addresses the need to better characterize real-world tractor power requirements across drawbar, power take-off (PTO), and hydraulic modes to support more representative tractor testing. Conventional testing protocols, such as OECD Code 2, emphasize steady-state performance under controlled high-load conditions, which do not reflect the mixed and dynamic demands of modern field operations. To address this gap, a Tractor Instrumentation System (TIS) was developed, validated, and deployed to collect high-resolution, mixed-mode power data during planting, anhydrous ammonia application, and grain cart operations. The TIS integrates physical sensors, including custom load pins, hydraulic pressure/flow sensors, and a redesigned PTO torque …

Cnn-Based Hybrid Model For Detecting Blight Diseases In Potato Crops With Advanced Image Processing Techniques, Farian S. Ishengoma

Tanzania Journal of Engineering and Technology (TJET)

Potato production plays a vital role in global agriculture as a major food source for large populations. However, potato crops are highly susceptible to diseases, particularly Early Blight and Late Blight, which result in substantial yield losses. Timely detection and effective control of these diseases are essential for maintaining stable crop output. This study explores the integration of Convolutional Neural Networks (CNNs) and advanced image processing techniques to differentiate between diseased and healthy potato plants accurately. Two datasets comprising original and enhanced images were used to train four CNN models: InceptionV3, Xception, Densenet201, and Resnet152V2. The original images underwent background …

Compost Grinder For The University Of South Carolina Office Of Sustainability, Rori E. Pumphrey, Grace Yaegel, Aaron R. Sawyer, Bradley White

Senior Theses

This project originates from a collaboration with the USC Office of Sustainability, which seeks to improve the handling and processing of food waste generated on campus. The primary challenge is the difficulty in composting certain types of food waste, such as avocado pits, pumpkin rinds, and other dense or fibrous organic materials that are not easily broken down using conventional methods. Existing commercial solutions are often too large and expensive, or electrically powered, and are thus not well suited for the volume or nature of USC's food waste. To address these limitations, our team designed a manually operated food waste …

Reduced Order Approach For Peening Stress Field Variability, Langdon Feltner, Paul Mort

15th International Conference on Shot Peening

A common goal in shot peening research is to connect operational parameters to resultant residual stress fields, providing a means to control and optimize the effectiveness of surface treatment. In practice, experimental measurements of residual stresses are often averaged values over regions that are large in comparison to an impact dimple. In fact, the stochastic nature of impact locations leads to residual stress fields that are distributed. Finite element peening simulations confirm this observation. The goal of this report is to connect operational parameters to localized fluctuations in residual stress through probabilistic reasoning (Figure 1). In particular, the development of …

Investigations On The Fatigue Strength Of Threads Produced By Different Fabrication Techniques, Philippe Du Maire, Jürgen Hoffmeister, Andreas Öchsner, Michael Johlitz

15th International Conference on Shot Peening

The increasing importance of sustainability in engineering demands the development of long-lasting, high-performance components that reduce material and energy consumption over time. This study investigates how different thread manufacturing processes, i.e., cutting, rolling, and deep rolling, affect the fatigue strength of bolts made from 42CrMo4+QT steel. Cylindrical specimens with M12 threads were subjected to cyclic tensile loading with constant mean stress. Fatigue strength was evaluated using the staircase method, and supporting analyses included X-ray diffraction for residual stress, and full width half maximum examination and Vickers microhardness measurements. Results show that thread rolling significantly improves fatigue strength, achieving 113.8 MPa …

Numerical Assessment Of Shot Peening Contribution To The Fatigue Strength Of Gear Tooth Root, Gurutz Cortabitarte Laucirica, Xuban Telleria, Iñigo Llavori, Ibai Ulacia, Miren Larrañaga, Jon Ander Esnaola

15th International Conference on Shot Peening

Gears are commonly treated with shot peening (SP) and/or case hardening to enhance fatigue resistance. However, their effects are often conservatively assessed using standardized methods, which can limit their optimal application in industrial components. Particularly, the effect of SP over case-hardened gears remains insufficiently explored. Therefore, the present study evaluates the contribution of SP on single tooth bending fatigue (STBF) strength of raw and case-hardened spur gears, commonly used in automotive and heavy machinery industries. In the study four conditions are addressed: (i) untreated, (ii) case-hardened, (iii) shot-peened, and (iv) case-hardened and shot-peened. First, the residual stress field of the …

Improving Fatigue Strength And Life Of Single Crystal Cmsx-4, Jochen Peter Fuhr, Lloyd Hackel, Nicolau I. Morar, Noah Holtham, Keivan Davami, Montu Sharma, Rajkumar Roy

15th International Conference on Shot Peening

The deep penetration of laser peening (LP) and retention of residual stress at high temperature by LP is significant in improving fatigue life and strength of superalloys exposed to high temperature and corrosion. Single crystal CMSX-4, was evaluated for stress relaxation and both fatigue life and fatigue strength of material that was LP-treated compared to non-LP and shot-peened (SP) specimens. LP was done with multiple layers using a 20 J/pulse laser where the laser high energy enabled using a 5 mm spot size on the metal surface. Stress measurements by the slitting technique showed the plastic penetration depth exceeded SP …

Effect Of A Small Control Rod On The Aerodynamic Forces And Wake Structure Of Side-By-Side Cylinders At Moderate Reynolds Number, M. M. Mosallem

Journal of Engineering Research

The unsteady wake interaction between two side-by-side circular cylinders often leads to significant vortex shedding and fluctuating aerodynamic forces. This numerical study investigates the effect of a small passive control rod with a rod-to-cylinder diameter ratio d/D = 0.07 on the wake dynamics and aerodynamic forces of two side-by-side circular cylinders. Two configurations are explored: one where the control rod is placed directly behind the cylinders (x/D = 0), and another where it is located downstream (x/D = 0.5). The two cylinders are arranged with a center-to-center spacing ratio T/D = 1.25. The simulations were …

Design Of A 10-Ton Capacity Solar-Powered Cold Storage At The Cituis Fish Auction Site, Tangerang, Banten, Indonesia, Wardi Wardi, Muhammad Arif Budiyanto

Journal of Materials Exploration and Findings

This study presents the design of a 10-ton capacity solar-powered cold storage system for the Cituis Fish Auction Site (TPI) in Tangerang, Indonesia, as a sustainable solution to support the coastal fisheries sector. The system comprises two temperature zones: an anteroom at 5°C and a freezer room at -30°C, both integrated with a hybrid system utilizing solar panels and batteries. The total power consumption of the cooling system reaches 27.51 kW. The simulation results, obtained using HOMER Pro software, indicate that the hybrid PV system can reduce CO₂ emissions by up to 16,754 kg per year. From an economic …

Mass Effects On Energy Transfer Paths In Nonlinear Vibrating Systems, Manal Mustafa

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This dissertation examines the role of mass in nonlinear systems, uncovering its role in enabling passive energy redistribution and robust vibration control in both idealized and real-world structures. Focusing on a strongly nonlinear two-degree-of-freedom system, it investigates how changes in mass ratio influence the dynamics of energy transfer, nonlinear normal modes (NNMs), and dissipation behavior.

A number of significant contributions are introduced in this work beginning with the introduction of the frequency-energy-peaks (FE-pks) plot, a novel tool that visualizes how energy flows through the system, revealing transient resonance orbits, internal resonance effects, and effectively capturing the different nonlinear phenomena with …

Predicting Leakage From Nuclear Material Containers At Los Alamos National Laboratory Through Drop Testing, Leak Testing, Finite Element Analysis And Digital Image Correlation, Jude M. Oka, Yu-Lin Shen, Osman Anderoglu, Pankaj Kumar, Rajendra Vaidya

Mechanical Engineering ETDs

Los Alamos National Laboratory (LANL) relies on containment vessels to safely manage special nuclear material. These containers are subject to rigorous testing—such as drop, fire, and water ingress testing—to ensure integrity under adverse conditions. While elastomer-based seals are well studied, metal-to-metal sealing mechanisms remain under investigation, particularly under dynamic loading. This research focuses on the relationship between container mating surfaces and impact loading through drop testing. Finite Element Analysis (FEA) models were developed and validated using Digital Image Correlation (DIC) to measure strain during impact. Drop tests at varying heights showed strong correlation between FEA and DIC results, confirming the …

The Role Of Internal Factors On Vehicular Mobility, Aziz Mdimi

Tanzania Journal of Engineering and Technology (TJET)

Vehicle mobility internal factors are influenced by the performance state of the road surface quality, governor, engine, gear train, differential unit and mobility unit. Studies on vehicular mobility models exist for off-road external factors but absent on on-road internal factors. The on-road internal factors model describes the vehicular mobility performance as a function of internal factors. In the current undertaking, results are generated by the determination of mobility performance characteristics with the application of 2nd Order Ordinary Differential Equations and using Laplace operator with MATLAB Software simulation. The effect of road surface against the time taken varies accordingly. At a …

Lidss Raft Battery Pack Integration, Jack Maxwell, Vincent Stevens, Matthew Hoodmaker, Colin Flanders

Mechanical Engineering

Lawrence Livermore National Laboratory is a critical member of the United States Department of Defense. Their Independent Diagnostics Scoring System (LIDSS) uses rafts that operate in the ocean to collect missile test data. Several times a year, the United States will test their Inter-Continental Ballistic Missiles by launching them into the ocean near the Marshall Islands. This is where the LIDSS rafts collect their test data. Our project was centered around re-designing the battery pack used by the rafts. The current battery pack design experiences water ingress problems and is difficult to access. Our re-designed battery pack is waterproof to …

Trailer Transport System For Multi-Ton Bins, Joanna Lizbeth Bendy, Kevin Matthew Creel, Annelise Vaara Cuneo, Hugo Alonso Valdez

Mechanical Engineering

This project aimed to improve the process of transporting 10,000-pound industrial waste bins. The current method for relocating these bins poses safety risks and requires significant manual effort. This project presents a conceptual solution that enables a single operator to efficiently and safely move roll-off bins using a custom-designed trailer system. The design incorporates three main subsystems: a trailer frame, an integrated winch system, and an off-the-market puller device to guide and secure the bin during transport. Two scaled proof-of-concept prototypes were fabricated to evaluate key aspects of the system's functionality. Testing and analysis suggested that the system is viable …

Large Backflow Check Valve Life Cycle Test Stand, Colin Bentley, Christopher Carloni, Ethan Gray, Luke Romanini

Mechanical Engineering

Backflow preventers are plumbing devices containing internal check valves used to prevent cross-contamination between downstream contaminants and potable water supply. Zurn Wilkins needs a life cycle test stand to mechanically force open check valves submerged in contaminated water and verify check performance. The stand needs to be modular to work with a range of check types and sizes.

Zurn Wilkins is the primary stakeholder for this project. Secondary stakeholders include commercial and residential building owners, contractors, and water utility companies, who rely on their products for safe and efficient water management. The team for this project consists of four Cal …

Effect Of Manufacturing And Machining Process On Recycled Composite Connecting Rods Under Tension And Compression, Walter W. Oppelt

Master's Theses

Carbon fiber reinforced polymer (CFRP) is an engineering material renowned for its high-strength and low-density material properties. Such properties make CFRPs especially useful for applications across many industries, including aerospace, automotive, marine, sporting goods, oil and gas, and more. However, with such favorable material properties comes the cost of high energy usage required to produce raw carbon fiber. Recycled carbon fiber (rCF) has emerged as a promising alternative, offering a significant reduction in energy usage. This research explores the viability of applying recycled CFRPs to internal combustion engines to both reduce energy costs during manufacturing and while in use. Mechanical …

Model-Based Design Of Compressed Lithium-Metal Pouch Cell Battery Modules For Evtol Applications, Scott J. Stirling

Master's Theses

Batteries with higher specific energy and power are essential for extending the range and performance of electric vertical takeoff and landing aircraft (eVTOLs). Anode-free lithium-metal pouch cells offer strong potential at the cell-level but require high compressive pressures to enhance cycle life and discharge performance. These pressures necessitate heavier structural components, reducing packaging efficiency at the module level.

To evaluate this tradeoff, a full-factorial enumeration model was developed to explore viable module designs within a constrained packaging volume. The model scales subsystem masses, enforces design rules and material limits, and accounts for large (~20%) cell thickness changes during cycling.

Results …