Applied Mechanics Commons^™

Study On The Impact Abrasive Wear Of New Super-High Manganese Steel, Wenyan Wang

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

No abstract provided.

Numerical And Experimental Characterization Of Material Flow In Forged Aluminum Wheel, Jong-Ning Aoh, Ming-Chiu Li, Chong-Jin Li

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

No abstract provided.

Simulation On The Sealing Of Aluminum Ball Joint, Haobin Tian, Xiaohang Liu, Xuelei Li, Jun Feng

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

No abstract provided.

Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed

Theses and Dissertations

The objective of this research is to generate design maps to identify functionally graded microstructures with enhanced fracture toughness. Several Functionally Graded Materials (FGMs) with an edge crack and membrane loading are considered and the resulting J-integral values are computed numerically using Finite Element Analysis. In order to capture the resulting stress fields accurately, Barsoum elements are used in the vicinity of the crack tip and the simulations are carried out for several crack lengths (a) and material contrasts (κ). The averages of the J-integral values are used to determine the normalized Stress Intensity Factors which are then benchmarked with …

Finite Element Modeling Of Delamination Damage In Carbon Fiber Laminates Subject To Low-Velocity Impact And Comparison With Experimental Impact Tests Using Nondestructive Vibrothermography Evaluation, George Rodriguez Iv

Master's Theses

Carbon fiber reinforced composites are utilized in many design applications where high strength, low weight, and/or high stiffness are required. While composite materials can provide high strength and stiffness-to-weight ratios, they are also more complicated to analyze due to their inhomogeneous nature. One important failure mode of composite structures is delamination. This failure mode is common when composite laminates are subject to impact loading.

Various finite element methods for analyzing delamination exist. In this research, a modeling strategy based on contact tiebreak definitions in LS-DYNA^®was used. A finite element model of a low-velocity impact event was created to …

A Parametric Study Of Meso-Scale Patterns For Auxetic Mechanical Behavior Optimization, Matthew C. Schuler

Honors Undergraduate Theses

This thesis focuses on the development, parameterization and optimization of a novel meso-scale pattern used to induce auxetic behavior, i.e., negative Poisson's ratio, at the bulk scale. Currently, the majority of auxetic structures are too porous to be utilized in conventional load-bearing applications. For others, manufacturing methods have yet to realize the meso-scale pattern. Consequently, new auxetic structures must be developed in order to confer superior thermo-mechanical responses to structures at high temperature. Additionally, patterns that take into account manufacturing limitations, while maintaining the properties characteristically attached to negative Poisson's Ratio materials, are ideal in order to utilize the potential …

Three-Dimensional Microstructural Effects On Multi-Site Fatigue Crack Nucleation Behaviors Of High Strength Aluminum Alloys, Yan Jin

Theses and Dissertations--Chemical and Materials Engineering

An experimental method was further developed to quantify the anisotropy of multi-site fatigue crack initiation behaviors in high strength Al alloys by four-point bend fatigue testing under stress control. In this method, fatigue crack initiation sites (fatigue weak-links, FWLs) were measured on the sample surface at different cyclic stress levels. The FWL density in an alloy could be best described using a three-parameter Weibull function of stress, though other types of sigmoidal functions might also be used to quantify the relationship between FWL density and stress. The strength distribution of the FWLs was derived from the Weibull function determined by …

Effects Of Magnetic Field On The Shape Memory Behavior Of Single And Polycrystalline Magnetic Shape Memory Alloys, Ali S. Turabi

Theses and Dissertations--Mechanical and Aerospace Engineering

Magnetic Shape Memory Alloys (MSMAs) have the unique ability to change their shape within a magnetic field, or in the presence of stress and a change in temperature. MSMAs have been widely investigated in the past decade due to their ability to demonstrate large magnetic field induced strain and higher frequency response than conventional shape memory alloys (SMAs). NiMn-based alloys are the workhorse of metamagnetic shape memory alloys since they are able to exhibit magnetic field induced phase transformation. In these alloys, martensite and austenite phases have different magnetization behavior, such as the parent phase can be ferromagnetic and martensite …

Shape Memory Behavior Of Single Crystal And Polycrystalline Ni-Rich Nitihf High Temperature Shape Memory Alloys, Sayed M. Saghaian

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTiHf shape memory alloys have been receiving considerable attention for high temperature and high strength applications since they could have transformation temperatures above 100 °C, shape memory effect under high stress (above 500 MPa) and superelasticity at high temperatures. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf alloys have some drawbacks such as low ductility and high work hardening in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing.

Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti29.3Hf20, …

Influence Of Spatial Variations Of Railroad Track Stiffness And Material Inclusions On Fatigue Life, Celestin Nkundineza

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

Railroad transportation is very important for economic growth and effective maintenance is one critical factor for its economic sustainability. The high repetitive forces from a moving railcar induce cyclic stresses that lead to rail bending and potential deterioration due to fatigue crack initiation and propagation. Previous research for prediction of fatigue life has been done under the assumptions of a uniform track bed and a homogeneous rail. However the spatial variation of the track stiffness is expected to increase the maximum stresses in the rail and, therefore, accelerate the fatigue process. The research described in this dissertation is focused on …

Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson

Graduate Theses and Dissertations

Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective …

Microstructure Development Of Granular System During Compaction, Chen Shang, Marcial Gonzalez

The Summer Undergraduate Research Fellowship (SURF) Symposium

Granular materials is the second most manipulated material in the industry today. They are easy to transport and more and more newly developed materials cannot stand the process of traditional casting, like energetic materials and bio-materials, but will survive the powder compaction process. Having a better understanding of the microstructure development of granular systems during compaction process, especially for particles that will heavily deform under loading, will give an insight of how to better process the powders to produce materials with overall better performance comparing to bulk materials. The main theory and mechanism applied are Hertz law and nonlocal contact …

Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman

Graduate Theses and Dissertations

The objectives of this work are to investigate the structure and energetic stability of different alumina (Al₂O₃) phases using atomistic simulation and virtual diffraction characterization. To meet these objectives, this research performs molecular statics and molecular dynamics simulations employing the reactive force-field (ReaxFF) potential to model bulk, interface, and surface structures in the θ-, γ-, κ-, and α-Al₂O₃ system. Simulations throughout this study are characterized using a new virtual diffraction algorithm, developed and implemented for this work, that creates both selected area electron diffraction (SAED) and x-ray diffraction (XRD) line profiles without assuming …

Characterization Of 3d Interconnected Microstructural Network In Mixed Ionic And Electronic Conducting Ceramic Composites, William M. Harris, Kyle S. Brinkman, Ye Lin, Dong Su, Alex P. Cocco, Arata Nakajo, Matthew B. Degostin, Yu-Chen Karen Chen-Wiegart, Jun Wang, Fanglin Chen, Yong S. Chu, Wilson K. S. Chiu

Faculty Publications

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce_0.8Gd_0.2O₂ (GDC) oxygen ion conductive phase and a CoFe₂O₄ (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered …

A Sinteractive Ni-Bazr0.8Y0.2O3-Δ Composite Membrane For Hydrogen Separation, Shumin Fang, Siwei Wang, Kyle S. Brinkman, Fanglin Chen

Faculty Publications

BaZr_0.8Y_0.2O_3−δ (BZY) is an excellent candidate material for hydrogen permeation membranes due to its high bulk proton conductivity, mechanical robustness, and chemical stability in H₂O- and CO₂-containing environments. Unfortunately, the use of BZY as a separation membrane has been greatly restrained by its highly refractory nature, poor grain boundary proton conductivity, high number of grain boundaries resulting from limited grain growth during sintering, as well as low electronic conductivity. These problems can be resolved by the fabrication of a Ni–BZY composite membrane with large BZY grains, which requires the development …

Investigation Of The High-Temperature Redox Chemistry Of Sr2Fe1.5Mo0.5O6-Δ Via In Situ Neutron Diffraction, Daniel E. Bugaris, Jason P. Hodges, Ashfia Hug, W. Michael Chance, Andreas Heyden, Fanglin Chen, Hans-Conrad Zur Loye

Faculty Publications

Crystallographic structural changes were investigated for Sr₂Fe_1.5Mo_0.5O_6−δ, an electrode material for symmetric solid oxide fuel cells. The samples of this material were heated and cooled in wet hydrogen and wet oxygen atmospheres, to simulate the reducing and oxidizing conditions experienced under actual fuel cell operating conditions, and their structures and oxygen contents were determined using in situ powder neutron diffraction. The existence of a reversible tetragonal to cubic phase transition was established to occur between room temperature and 400 °C, both on heating and cooling in either oxygen or hydrogen. The …

Design, Fabrication, And Properties Of 2-2 Connectivity Cement/Polymer Based Piezoelectric Composites With Varied Piezoelectric Phase Distribution, Xu Dongyu, Cheng Xin, Sourav Banerjee, Huang Shifeng

Faculty Publications

The laminated 2-2 connectivity cement/polymer based piezoelectric composites with variedpiezoelectric phase distribution were fabricated by employing Lead Zirconium Titanate ceramicas active phase, and mixture of cement powder, epoxy resin, and hardener as matrix phase with a mass proportion of 4:4:1. The dielectric, piezoelectric, and electromechanical coupling properties of the composites were studied. The composites with large total volume fraction ofpiezoelectric phase have large piezoelectric strain constant and relative permittivity, and thepiezoelectric and dielectric properties of the composites are independent of the dimensional variations of the piezoelectric ceramic layer. The composites with small total volume fraction of piezoelectric phase have large …

Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary

Graduate Theses and Dissertations

The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially address these shortcomings …

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 …

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 …

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 …

Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita

Graduate Theses and Dissertations

Abrasive grinding is widely used across manufacturing industry for finishing parts and components requiring smooth superficial textures and precise dimensional tolerances and accuracy. Unlike any other machining operations, the complex thermo-mechanical processes during grinding produce excessive friction-induced energy consumption, heat, and intense contact seizures. Lubrication and cooling from grinding fluids is crucial in minimizing the deleterious effects of friction and heat to maximize the output part quality and process efficiency. The conventional flood grinding approach of an uneconomical application of large quantities of chemically active fluids has been found ineffective to provide sufficient lubrication and produces waste streams and pollutants …

Vulnerability Of Progressive Collapse In Reinforced Concrete Flat-Plate Buildings, Jinrong Liu

College of Engineering: Graduate Celebration Programs

• Progressive collapse is the spread of initial local failure, causing partial or
  even total collapse of a building.
• Flat plate structure is widely used for office and residential buildings.
• There is a large inventory of older flat plate building without continuous slab bottom reinforcement through columns.
• Limited knowledge exists regarding the risk of disproportionate collapse in
  older flat-plates under sudden column removal during abnormal events.
• Reliable mechanical model is needed for structural evaluation.

Numerical Modeling And Characterization Of Vertically Aligned Carbon Nanotube Arrays, Johnson Joseph

Theses and Dissertations--Mechanical and Aerospace Engineering

Since their discoveries, carbon nanotubes have been widely studied, but mostly in the forms of 1D individual carbon nanotube (CNT). From practical application point of view, it is highly desirable to produce carbon nanotubes in large scales. This has resulted in a new class of carbon nanotube material, called the vertically aligned carbon nanotube arrays (VA-CNTs). To date, our ability to design and model this complex material is still limited. The classical molecular mechanics methods used to model individual CNTs are not applicable to the modeling of VA-CNT structures due to the significant computational efforts required. This research is to …

High Performance Low Temperature Solid Oxide Fuel Cells With Novel Electrode Architecture, Yu Chen, Qian Liu, Zhibin Yang, Fanglin Chen, Minfang Han

Faculty Publications

In this study, we have fabricated high performance low temperature solid oxide fuel cells (LT-SOFCs) with both acicular anodes and cathodes with thin Gd-doped ceria (GDC) electrolyte film. The acicular Ni-Gd_0.1Ce_0.9O_2−δ (Ni-GDC) anode was prepared using freeze drying tape casting, while the hierarchically porous cathode with nano-size Sm_0.5Sr_0.5CoO₃ (SSC) particles covering an acicular GDC skeleton was prepared by a combination of freeze drying tape casting and self-rising approaches. The acicular electrodes with 5–200 μm pores/channels enhance mass transport, while SSC particles of about 50 nm in the cathode promote …

Biaxial & Twist Testing Of Composite Carbon-Fiber Sandwich Panels For Automotive Racing Vehicles, Erik Eckberg

Materials Engineering

Composite sandwich panels were constructed with 4-ply plain weave carbon-fiber/epoxy face sheets in the 0^o/45^o/0^o/45^o orientation and 1/8^th inch Nomex honeycomb core. The panels were cut into 5-inch square test plates for mechanical testing. All testing was done on a fixture designed and fabricated by Pratt & Miller Engineering and installed on an Instron testing system at Cal Poly. The twist test was performed by supporting diagonal corners of the plate while simultaneously loading the opposite two corners at a crosshead rate of .06 in/min (ASTM 3044-94R11). Out of 10 panels tested, …

Advanced Design Optimization For Composite Structure: Stress Reduction, Weight Decrease And Manufacturing Cost Savings, Shayan Ahmadian

Master's Theses

An injection moldable chopped fiber composite actuator with detailed drawing and tolerances was designed within one year. A vendor was selected and a quote for injection molding tooling cost for production was obtained and the first prototype was built in addition of six months. The risks are identified and material characterization tests are proposed.

The objective of this project was redesigning an aluminum made actuator with a continuous fiber composite for weight saving purposes. After searching the literature and consulting with experts in the field it was concluded that manufacturing costs associated with continuous fiber composite are 3 times as …

A Conductivity Testing System Coupled With A Tensile Testing Machine To Measure The Surface Properties Of Polymer Specimens, Nguyen T. Nguyen

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

Polymers play an essential role in our everyday life due to their employment in a widespread range of applications. Polymers are used in industries such as space, biomedical, electronics, etc. in which their electrical and mechanical properties are major aspects which need to be investigated prior to implementation. When subjected to mechanical stimulations, polymers may exhibit changes in electrical conductivity which can vary locally within the specimens, especially in those of conducting polymers. In mechanical investigations a tensile testing machine is used to understand polymers’ strength, elasticity or other mechanical properties. In electrical analysis, using a four-point probe to examine …

Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

The impacts of the two-beam interference heating on the number of core-shell and embedded nanoparticles and on nanostructure coarsening are studied numerically based on the non-linear dynamical model for dewetting of the pulsed-laser irradiated, thin (< 20 nm) metallic bilayers. The model incorporates thermocapillary forces and disjoining pressures, and assumes dewetting from the optically transparent substrate atop of the reflective support layer, which results in the complicated dependence of light reflectivity and absorption on the thicknesses of the layers. Stabilizing thermocapillary effect is due to the local thickness-dependent, steady- state temperature profile in the liquid, which is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Linear stability analysis of the model equations set for Ag/Co bilayer predicts the dewetting length scales in the qualitative agreement with experiment.

Finite Element Analysis Of The Contact Deformation Of Piezoelectric Materials, Ming Liu

Theses and Dissertations--Chemical and Materials Engineering

Piezoelectric materials in the forms of both bulk and thin-film have been widely used as actuators and sensors due to their electromechanical coupling. The characterization of piezoelectric materials plays an important role in determining device performance and reliability. Instrumented indentation is a promising method for probing mechanical as well as electrical properties of piezoelectric materials.

The use of instrumented indentation to characterize the properties of piezoelectric materials requires analytical relations. Finite element methods are used to analyze the indentation of piezoelectric materials under different mechanical and electrical boundary conditions.

For indentation of a piezoelectric half space, a three-dimensional finite element …