Mechanical Engineering Commons^™

In Situ Measurement Of Fatigue Induced Crack Growth In Inconel 718 Using Direct Current Potential Drop Method, Joel C. Lindsay

Graduate Theses, Dissertations, and Problem Reports

With recent advances in air breathable engines comes more extreme temperature environments that engine components must tolerate. During the design of these engines, it is necessary to understand how material fatigue failures occur at these new, higher operating temperatures. In providing understanding, the following fundamental study focuses on the statistical nature of crack jumps (changes in crack length over time) during fatigue in a polycrystalline nickel-based superalloy, Inconel 718 (IN718). In situ measurement of the crack length at several loading conditions were conducted using a direct current potential drop (DCPD) measurement method. Experimental data was collected at six different fatigue …

Development Of A Rapid Fatigue Life Testing Method For Reliability Assessment Of Flip-Chip Solder Interconnects, Cody Jackson Marbut

Graduate Theses and Dissertations

The underlying physics of failure are critical in assessing the long term reliability of power packages in their intended field applications, yet traditional reliability determination methods are largely inadequate when considering thermomechanical failures. With current reliability determination methods, long test durations, high costs, and a conglomerate of concurrent reliability degrading threat factors make effective understanding of device reliability difficult and expensive. In this work, an alternative reliability testing apparatus and associated protocol was developed to address these concerns; targeting rapid testing times with minimal cost while preserving fatigue life prediction accuracy. Two test stands were fabricated to evaluate device reliability …

Numerical Evaluation Of Energy Release Rate At Material Interfaces For Fatigue Life Predictions, Robert L. Hendrickson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Composite materials are becoming popular in almost all industries. Carbon-fiber and glass-fiber composites are used in aircraft, sports equipment, boats, prosthetics, and wind turbine blades. In all these applications, the composites are subjected to different loads. Loads can take the form of impact or cyclic/fatigue loading, both of which decrease the strength of composites as micro-cracks grow through the composite. Composite laminates are made up of fiber plies (thin layers of fiber) and the fibers are surrounded by a resin like epoxy. It is common for laminates to fail because of delamination growth (plies peeling apart). Small delaminations do not …

A Nanoindentation Study Of The Fatigue Properties Of Al/A-Si Core-Shell Nanostructures, Jason Steck

Mechanical Engineering Undergraduate Honors Theses

Nanostructure-textured surfaces can reduce friction and increase the reliability of micro- and nanoelectromechanical systems (NEMS/MEMS). For MEMS incorporating moving parts, the fatigue properties of nanostructures pose a challenge to their reliability in long-term applications. In this study, the fatigue behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), bare hemispherical Al nanodots, and a flat Al/a-Si layered thin film have been studied using nanoindentation and nano-scale dynamic mechanical analysis (nano-DMA) techniques. Fatigue testing with nano-DMA shows that the deformation resistance of CSNs persists through 5.0 × 10⁴ loading cycles at estimated contact pressures greater than 15 GPa. When the a-Si shell …

Determination Of Chemical Notch, KChem On Aluminum And Steel When Subjected Under Slow Strain Rate Test In Corrosive Environment, Joshua Teo Lee Kuok

Masters Theses

When designing for any mechanical components or system, the question would arise as to how the material would react to the loads subjected on it? Would the component survive its service load? How would it react to environmental corrosion? To answer these questions, the technique used in this thesis paper is the Slow Strain Rate Test (SSRT) method. Aluminum and steel were chosen as the material to be tested in this paper. Al 7075-T651, and Al 6061-T651 was chosen due to its wide range of application, high strength to weight ratio and ease of machinability. It is highly used in …

Peridynamic Models For Fatigue And Fracture In Isotropic And In Polycrystalline Materials, Guanfeng Zhang

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

To improve design and reliability, extensive efforts has been devoted to understanding damage and failure of materials and structures using numerical simulation, as a complement of theory and experiment. In this thesis, peridynamics is adopted to study fatigue and dynamic failure problems.

Fatigue is a major failure mode in engineering structures. Predicting fracture/failure under cyclic loading is a challenging problem. Classical model cannot directly be applied to problems with discontinuities. A peridynamic model is adopted in this work because of important advantages of peridynamics in allowing autonomous crack initiation and propagation. A recently proposed peridynamic fatigue crack model is considered …

Studies On Woven Carbon/Vinyl Ester Composites: Environmental Effects, Joining And Hybridization, Ricardo Garcia

Open Access Theses & Dissertations

The incessant demand for fiber reinforced polymer composites, or FRPCs, in industrial applications which desire materials that possess high strength-to-weight ratios, generates a theory-to-practice void which must be filled with scientific research. In this Thesis, woven carbon/vinyl ester composites are studied under a wide spectrum of settings and conditions. The adverse effects of sea water environment and arctic temperatures on such mentioned composites are explored in the form of moisture uptake, impact on flexural modulus, strength and structural damage. It was found that sea water saturation in general degrades the flexural strength up to 19.45%, and arctic exposure and combined …

Final Design Report: Polymer Fatigue Characterization Test Method, Wyatt Ayling, Tyler Price, Brandon Stell, Michela Upson

Mechanical Engineering

Polylogix is a team dedicated to the design, build, and testing of a fatigue machine to simulate cyclic loading on a biomedical polymer. This project is sponsored by Endologix, Inc. to provide test data characterizing mechanical material properties of various formulations of polymer used in abdominal aortic aneurysm surgeries. With this project goal, the machine must be able to test the polymer at body conditions; these include a testing temperature of 37°C and a cycling frequency ranging from 1 Hz to 10 Hz. This report proposes the following solution to this design challenge: an AC motor-driven mechanism utilizing a planetary …

Dynamic Monitoring And Life Prediction Of Internal Strain-Gage Balances, David Leon Yoder

Masters Theses

Wind tunnel test customers continue to push the limits by producing air vehicle designs that produce high aerodynamic loads at the desired test conditions. These loads are a combination of steady aerodynamic, unsteady aerodynamic, and inertial forces. A methodology to monitor the health of a wind tunnel strain-gage balance has been developed. The objective of this methodology is to define the stress limits of the balance and monitor these limits so the balance can be safely tested without failure of the balance. A balance failure could result in costly damage to the wind tunnel model, support system, and the wind …

Fatigue Analysis Of The Welded Region In The Automotive Torsion Beam Rear Suspension System, Nan Zhan, Xiaochuan Zhang

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Properties That Characterize The Material X46cr13 Steel, Josip Brnic, Sanjin Krscanski, Marino Brcic, Jitai Niu

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte

Master's Theses (2009 -)

This thesis presents the study of fatigue crack propagation in a low carbon steel (ASTM A36) and two different weld metals (AWS A5.18 and AWS A5.28). Fatigue crack propagation data for each weld wire is of interest because of its use for predicting and analyzing service failures. Fatigue crack growth test specimens were developed and fabricated for the low carbon steel base metal and for each weld wire. Weld specimens were stress relieved prior to fatigue testing. Specimens were tested on a closed-loop servo hydraulic test machine at two different load ratios. Fatigue test data was collected to characterize both …

Mechanical Reliability Of Implantable Polyimide-Based Magnetic Microactuators For Biofouling Removal, Christian G. Figueroa-Espada, Qi Yang, Hyowon Lee

The Summer Undergraduate Research Fellowship (SURF) Symposium

Hydrocephalus is a neurological disorder that typically requires a long-term implantation of a shunt system to manage its symptoms. These shunt systems are notorious for their extremely high failure rate. More than 40% of all implanted shunt systems fail within the first year of implantation. On average, 85% of all hydrocephalus patients with shunt systems undergo at least two shunt-revision surgeries within 10 years of implantation. A large portion of this high failure rate can be attributed to biofouling-related obstructions and infections. Previously, we developed flexible polyimide-based magnetic microactuators to remove obstructions formed on hydrocephalus shunts. To test the long-term …

Tapered Roller Bearing Accelerated Life Test Rig Design And Fabrication, Laith Naeem, Andrew Nguyen, Bryson Sin, Ramon Vargas

Capstone Design Expo Posters

L₁₀ bearing fatigue life testing is a costly and prolonged process, as the bearing is characteristically designed for durability and reliability. Within the current testing methods, faulty materials still have the potential of passing the test. However, with this life test rig, the bearing will be tested to failure, thus providing an indicator for its predicted life span.

The purpose of this project is to optimize and construct a L₁₀ life test rig for accelerated fatigue testing of the Association of American Railroad Class K, 6 ½ x 9-inch double-row tapered roller bearing to their maximum fatigue life …

Equi-Biaxial Fatigue Testing Of Epm Utilising Bubble Inflation, Mark Johnson, Niall Murphy, Ray Ekins, John Hanley, Stephen Jerrams

Articles

This paper describes an equi-biaxial tension fatigue test system which utilises the bubble inflation method to subject elastomers to equi-biaxial fatigue loading between user-defined limits of pressure, volume, stretch ratio or stress. The test system integrates a hydraulic inflation system, a high speed vision system and a control system. The high-speed vision system allows the stretch ratio and stress acting on the test specimen to be evaluated in real-time during testing. This in turn allows either stretch ratio or stress to be used as a direct control limit. In this research, constant maximum engineering stress control tests have been carried …

Methodology For Analysis Of Stress, Creep, And Fatigue Behavior Of Compliant Mechanisms, Joshua Allen Crews

Doctoral Dissertations

"A methodology is developed for analyzing stress within homogeneous and metallic-reinforced, fixed-free compliant segments and small-length flexural pivots. Boundary conditions related to the inclusion of metallic reinforcing components within a polymer compliant segment are investigated. The analysis method outlined herein relies on key outputs from the pseudo-rigid-body models (PRBMs). A method is presented for the redesign of compliant mechanisms to include metallic reinforcement to reduce stress while maintaining force-deflection behavior. Examples are provided in which a compliant segment is redesigned to include metallic reinforcement by using the stress equations developed from the PRBM. The effect of bonding between the polymer …

Finite Element Analysis And Topology Optimization Of Differential Case And Control Arm For Static And Fatigue Loading, Pankaj N. Kalan

Dissertations, Master's Theses and Master's Reports

Optimization of the automobile components can result in a significant decrease in vehicle weight, increase in fuel efficiency and reduction in environmental damage. For example, the lightweight vehicle production will save over 4.4×109 GJ of energy and 4.1×108 tons of CO2 over a 10 year period, compared to the current non-light weight vehicles. This equates to 890 billion miles or 42 billion gallons of gas savings (Wu 2016). This study evaluates the weight reduction possible by using manual and automatic (using Optistruct software) topology optimization processes. Optimization of a vehicle differential case done in this study shows that a weight …

Fatigue Performance Of Glass Fiber/Epoxy Composite At Low Temperature, Prajakta Govande 2817401530, Dominic R. Cross, Kwek Tze Tan

Williams Honors College, Honors Research Projects

Due to technological advancement in the manufacturing methods of composites, these materials find a plethora of applications which include but are not limited to wind energy projects in the form of turbine blades. These blades at times are exposed to temperatures as low as -40ᵒC. Therefore, there is a need to study low-temperature effects on such materials under different loading scenarios. This study investigates the possibility of utilizing MAC/GMC as a simulation tool to match trends of mechanical properties such as fatigue performance and stiffness variation of a given Glass fiber/Epoxy composite at 23ᵒC (room temperature) and -40 ᵒC, under …

Elucidating The Role Of Microstructure, Texture, And Microtexture On The Dwell Fatigue Response Of Ti-6al-4v, Alec Mitchell Blankenship

Browse all Theses and Dissertations

Ambient temperature dwell sensitivity is known to be deleterious to the fatigue response of near-alpha titanium alloys. Dwell fatigue refers to the presence of a sustained hold at peak stress as opposed to the continuous variation of normal cyclic fatigue loading. This reduction in failure life-times from dwell loading is attributed to early crack nucleation and faster crack propagation. The degradation is the result of plastic anisotropy on the microstructural scale along with tendency of titanium alloys to creep at low temperatures at stresses well below the 0.2% offset yield strength. Despite being the most widely used titanium alloy, Ti-6Al-4V …

Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.

Browse all Theses and Dissertations

In this thesis, the Locally-Optimized Covariance (LOC) Kriging method is developed. This method represents a flexible surrogate modeling approach for approximating a non-stationary Kriging covariance structures for deterministic responses. The non-stationary covariance structure is approximated by aggregating multiple stationary localities. The aforementioned localities are determined to be statistically significant utilizing the Non-Stationary Identification Test. This methodology is applied to various demonstration problems including simple one and two-dimensional analytical cases, a deterministic fatigue and creep life model, and a five-dimensional fluid-structural interaction problem. The practical significance of LOC-Kriging is discussed in detail and is directly compared to stationary Kriging considering computational …

Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou

Electronic Thesis and Dissertation Repository

Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design …

Tracking Of Spall Deterioration On Tapered Roller Bearings, Amy Gonzalez, Constantine Tarawneh, Ping Hu, Joseph A. Turner, Brent Wilson

Mechanical Engineering Faculty Publications and Presentations

Fatigue spall initiation is one of the major modes of premature bearing failure. The spall initiation is often exacerbated by the presence of impurities in the near-surface region (∼400 μm) of the bearing raceways. Once a spall initiates, it can propagate rapidly, leading to abnormal bearing operation and possible catastrophic failure if not detected early. Testing performed at the University of Texas-Pan American (UTPA) has focused on ultrasonically scanned tapered roller bearings found to have inclusion content within 400 μm of the surface of the raceways. These bearings undergo accelerated service life tests in which spall initiation is detected and …

Fatigue Life Estimation Of Modified Railroad Bearing Adapters For Onboard Monitoring Applications, Alexis Trevino, Arturo A. Fuentes, Constantine Tarawneh, Joseph Montalvo

Mechanical Engineering Faculty Publications and Presentations

This paper presents a study of the fatigue life (i.e. number of stress cycles before failure) of Class K cast iron conventional and modified railroad bearing adapters for onboard monitoring applications under different operational conditions based on experimentally validated Finite Element Analysis (FEA) stress results. Currently, freight railcars rely heavily on wayside hot-box detectors (HBDs) at strategic intervals to record bearing cup temperatures as the train passes at specified velocities. Hence, most temperature measurements are limited to certain physical railroad locations. This limitation gave way for an optimized sensor that could potentially deliver significant insight on continuous bearing temperature conditions. …

Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy

Dissertations

The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …

Fatigue Performance Improvement By Dynamic Strain Aging And Dynamic Precipitation In Warm Laser Shock Peening Of Aisi 4140 Steel, Chang Ye, Gary Cheng

Dr. Chang Ye

Warm laser shock peening (WLSP) integrates the advantages of laser shock peening and thermal-mechanical treatment (TMT) to improve material fatigue performance. Compared to traditional laser shock peening (LSP), warm laser shock peening, i.e. LSP at elevated temperature, leads to better performance in many aspects. WLSP can induce nanoscale precipitations by dynamic precipitation and high density dislocation by dynamic strain aging (DSA), resulting in higher surface strength, which is beneficial for fatigue life improvement. Due to pinning of dislocation structure by nanoscale precipitates, and the pinning of dislocation structure by Cottrell atmosphere, or the DSA effect, stability of the dislocation arrangement …

Mechanism Of Fatigue Performance Enhancement In A Superhard Nanoparticles Integrated Nanocomposites By A Hybrid Manufacturing Technique, Dong Lin, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng

Dr. Chang Ye

A hybrid manufacturing process, which contains Laser Sintering (LS) and Laser shock peening (LSP), is introduced to generate iron-TiN nanoparticle nanocomposites. It is a two-step process including LS followed with LSP. Before LS, TiN nanoparticles mixed with iron powders are coated on samples surface. After LS, TiN nanoparticles are embedded into iron matrix to strengthen materials. Then LSP is performed to introduce work hardening and compressive residual stress. The existed nanoparticles increase the dislocation density and also help to pin the dislocation movement. Better residual stress stability under thermal annealing can be obtained by better dislocation movement stabilization, which is …

Face Sheet/Core Debonding In Sandwich Composites Under Static And Fatigue Loading, Manjinder Singh Warriach

Wayne State University Dissertations

Delamination growth due to face sheet/core debonding is a major concern due to its inherent weakness in sandwich composites which can be exacerbated due to the presence of flaws. In this research work The primary objective of this research was to characterize the delamination crack growth behavior in E-glass face sheet/polyurethane foam core sandwich composite with pre-existing initial delamination crack at a face sheet/core interface under static and fatigue for mode I and mixed mode loading. For mode I static loading two types of delamination experiments, namely T-peel test and wedge test were implemented to evaluate fracture toughness in polyurethane …

Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali

LSU Doctoral Dissertations

Irreversible material degradation due to cyclic mechanical loading is investigated utilizing the concept of thermodynamic entropy, plastic strain energy, and temperature slope measurement. Uniaxial tension-compression and fully-reversed bending fatigue tests are performed over a wide range of loading conditions with metallic and composite materials subject to both constant- and variable-amplitude loading. A methodology is developed for the estimation of the fatigue fracture entropy (FFE) and fatigue toughness of metallic specimens in a rapid fashion. It is found that the FFE and the fatigue toughness of each material tested are within a small band. The value of FFE is found to …

Implementation Of Analytical Fatigue Models Into Opensim To Predict The Effects Of Fatigue On Anterior Cruciate Ligament Loading, Michael A. Samann

Mechanical & Aerospace Engineering Theses & Dissertations

The anterior cruciate ligament (ACL) provides stability to the knee joint while performing activities such as a side step cut. Neuromuscular fatigue, a reduction in muscle force producing capabilities, alters lower extremity mechanics while performing a side step cut and may increase the risk of ACL injury, particularly in females. Musculoskeletal modeling allows for the measurement of muscle forces, which are difficult to measure in-vivo. Therefore, musculoskeletal modeling, may improve our understanding of the effects of neuromuscular fatigue on muscle force production and loading of the ACL. Therefore, the purpose of this study was to develop a musculoskeletal model which …

Prediction Of Tribological Behavior Of Candidate Materials For Rotor Seals, John W. Franzino, Will F. Michul

Materials Engineering

To reduce high costs associated with manufacturing and testing materials for rotor seals, a procedure needs to be developed to quickly and accurately test candidate materials as they are released. The test should reduce the amount of fabrication required and model working conditions in order to accurately assess the tribological behavior of candidate materials. A possible solution was examined that utilized a rig meant to model operational stresses and wear. Compression modulus data was then taken in order to quantify the accumulation of damage due to microcracking, the primary mode of failure, through a damage index parameter. Testing results concluded …