Detection Of 4-Point Bend Induced Micro-Cracks In Cfrp Laminates Via Coda Wave Nde, 2017 Iowa State University
Detection Of 4-Point Bend Induced Micro-Cracks In Cfrp Laminates Via Coda Wave Nde, Richard Livings, Dan Barnard, Vinay Dayal
Although coda wave NDE has been shown to have some sensitivity to realistic damage in concrete structures, the technique’s capability for detecting micro-cracks in fibrous composite materials has yet to be evaluated. This paper reports on the first investigation of realistic damage, specifically micro-cracks, in fibrous composite materials using coda wave differential signal features. Micro-cracks were generated in CFRP samples using the 4-point bending configuration shown in Fig. 1. The damage was monitored during loading with Acoustic Emission, and the loading was stopped after each significant damage event. The damage was then examined with coda wave NDE, immersion UT ...
Cylindrical Shell Based Phase Transforming Cellular Materials: Designing A Recoverable Energy Dissipating Material, Gordon F. Jarrold, David Restrepo, Nilesh Mankame, Pablo Zavattieri
The Summer Undergraduate Research Fellowship (SURF) Symposium
Energy dissipating materials are used in a variety of impact events to protect more important parts of a system; one example of this is a football player’s helmet protecting a brain. A major drawback to classic energy dissipating materials however is that they dissipate energy through plastic deformation, meaning that after a single use, permanent deformations will prevent the material from being reusable to the same capacity as initially. We have designed a 1D cellular material in which geometric phase transformations in cylindrical shell elements are the primary energy dissipating mechanism, allowing for recoverability after use while keeping high ...
Comparison Of Pm-Hip To Cast Alloy 625 For Nuclear Applications, 2017 Purdue University
Comparison Of Pm-Hip To Cast Alloy 625 For Nuclear Applications, Alexander L. Bullens, Keyou Mao, Janelle P. Wharry, Esteban Bautista
The Summer Undergraduate Research Fellowship (SURF) Symposium
PM-HIP, or Powder Metallurgy and Hot Isostatic Pressing, metals have been a low cost alternative to forged and cast structural metals within various industries. The nuclear industry has recently developed interest in PM-HIP alloys, but further research needs to be done to quantify their mechanical properties and characterize the microstructure. Specifically, we must understand the mechanical and microstructural evolution of PM-HIP materials after long-term operation at the elevated temperatures that PM-HIP components will experience in service. We focus on Ni-base alloy Inconel 625, and compare the PM-HIP version to the cast version. Our methodology consists of annealing samples to various ...
Core-Shell Copper And Nickel Nanofoam: Uniform Electroplating And Properties, 2017 Washington State University
Core-Shell Copper And Nickel Nanofoam: Uniform Electroplating And Properties, Hassan Zbib, David Bahr
The Summer Undergraduate Research Fellowship (SURF) Symposium
Characterizing materials on the nanoscale is a key factor to enhance nanotechnology in diverse applications, ranging from electronics to energy fields. However, controlling the structure of the material at the nanoscale or mimicking the nanoscale features of a structure that already exists requires linking processing conditions to the nanostructure. This work focuses on solids that show porous patterns at the nano-micro scale; these are often called cellular solids and classified into two categories: honeycombs and foams. This study focuses on nanofoams; with ligament dimensions in the sub-micron scale. Electrospinning has been developed to produce nanofoam structures of polymers with controlled ...
Viscoelastic Analysis And Fatigue Characterization Of Bituminous Materials In Two Length Scales Under The Influence Of Aging, 2017 University of Nebraska-Lincoln
Viscoelastic Analysis And Fatigue Characterization Of Bituminous Materials In Two Length Scales Under The Influence Of Aging, Santosh Reddy Kommidi
Civil Engineering Theses, Dissertations, and Student Research
Fatigue cracking in asphalt concrete (AC) is of immense importance to pavement design and analysis because it is one of the most important forms of distress that can lead to structural failure in pavement. Once started, these types of cracks can be combined with other environmental factors leading to detrimental effects such as faster rates of pavement deterioration and shortened pavement life and functionality.
Currently AASHTO TP101, also known as linear amplitude sweep (LAS) specification, is being widely used to evaluate the ability of an asphalt binder to resist fatigue. The LAS method, although mechanistic in its approach, has certain ...
Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, 2017 University of Arkansas, Fayetteville
Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, Robert Andrew Fleming
Theses and Dissertations
Al/a-Si core-shell nanostructures (CSNs), consisting of a hemispherical Al core surrounded by a hard shell of a-Si, have been shown to display unusual mechanical behavior in response to compression loading. Most notably, these nanostructures exhibit substantial deformation recovery, even when loaded much beyond the elastic limit. Nanoindentation measurements revealed a unique mechanical response characterized by discontinuous signatures in the load-displacement data. In conjunction with the indentation signatures, nearly complete deformation recovery is observed. This behavior is attributed to dislocation nucleation and annihilation events enabled by the 3-dimensional confinement of the Al core. As the core confinement is reduced, either ...
Optimization Of Concrete Mixtures For Use In Structural Elements, 2017 University of Arkansas, Fayetteville
Optimization Of Concrete Mixtures For Use In Structural Elements, Waleed Almutairi
Theses and Dissertations
Portland cement is an essential ingredient in concrete. The use of cement is to enhance the strength as well as other hardened properties of concrete mixtures. Determining the accurate amount of cement is important because the required strength may not be achieved if not enough cement is used. By contrast, when using too much cement, concrete cracking may occur that leads to reducing durability. Researchers at the University of Arkansas (UA) have shown that many bridge decks achieve their 28 day design strength of 4000 psi by 7 days of age. Bridge decks having high strength may experience cracking, which ...
Mitigation And Evaluation Of Alkali-Silica Reaction (Asr) And Freezing And Thawing In Concrete Transportation Structures, 2017 University of Arkansas, Fayetteville
Mitigation And Evaluation Of Alkali-Silica Reaction (Asr) And Freezing And Thawing In Concrete Transportation Structures, Richard Albert Deschenes Jr.
Theses and Dissertations
An evaluation of alkali-silica reaction (ASR) and freezing and thawing (F/T) in concrete transportation structures is presented along with mitigation methods for slowing the rate of deterioration in concrete. A combination of field and laboratory testing confirms ASR deterioration is exacerbated by exposure to F/T. Laboratory testing indicates an aggregate previously deemed inert to ASR, caused ASR deterioration in several concrete pavement and transportation structures. Existing standard test methods deem this aggregate safe for use in concrete. A modified test method shows the concrete can deteriorate rapidly when subjected to cycles of conditions promoting ASR and F/T ...
The Mechanism Of Radiation-Induced Nanocluster Evolution In Oxide Dispersion Strengthened And Ferritic-Martensitic Alloys, Matthew John Swenson
Boise State University Theses and Dissertations
The objective of this study is to evaluate the mechanism of irradiation-induced nanoparticle evolution in a model Fe-9%Cr oxide dispersion strengthened steel and commercial ferritic-martensitic alloys HCM12A and HT9. Each alloy is irradiated with Fe2+ ions, protons, or neutrons to doses ranging from 1-100 displacements per atoms at 500°C. The morphology of nanoclusters are characterized using atom probe tomography. The evolution of clusters in each alloy are notably different with each irradiating particle, and the competing effects of ballistic dissolution and radiation-enhanced, diffusion-driven growth are attributed to the respective differences in cluster evolution. A phase evolution model ...
A Study In The Use Of Elastic Materials In Expandable Containment Units, 2017 Liberty University
A Study In The Use Of Elastic Materials In Expandable Containment Units, Andrew J. Eisenman, Joby Anthony Iii, David Satagaj
Montview Liberty University Journal of Undergraduate Research
The rigidity of materials in conjunction with the aspect of elasticity has been a concern of modern technologies and construction in recent centuries because of the advantages that expandable storage would bring to the fields of containment units with respect to population growth and space exploration. The world population is currently growing at an exponential rate, and as our population grows, the more important it will become to have containment units that can both contain large volumes of material as well as minuscule amounts of material without wasting space. In order accomplish this, we will need a new type of ...
Probability Of Detection In Structural Health Monitoring, 2017 Iowa State University
Probability Of Detection In Structural Health Monitoring, William Q. Meeker
William Q Meeker
Structural Health Monitoring (SHM) is being proposed to replace traditional scheduled NDE inspections. This is raising questions about how to quantify Probability of Detection (POD) and whether the POD statistical methods of MIL-HDBK 1823 can still be used. The answer depends on the application, the nature of the SHM information, and how that information is mapped into a detect/not-detect decision. This talk will outline some of the issues involved in characterizing POD for different kinds of SHM applications.
Models For Ut Inspection Of Bolthole Cracks In Layered Structures, 2017 Iowa State University
Models For Ut Inspection Of Bolthole Cracks In Layered Structures, Robert Grandin, Tim Gray, Ron Roberts
Due to the geometrical complexities of bolted, layered airframe structures, the application of Model Assisted Probability of Detection, or MAPOD, is an important tool for helping to assess the ultrasonic inspectability of those components. Of particular importance is the need to inspect for cracks on or near boltholes in those structures. This presentation describes the development and testing of analytical computer models of and their application to bolthole crack inspection. The modeling approach includes approximate, paraxial, bulk-wave models as well as more rigorous, analytical models that include both bulk and surface/plate modes. The simpler models have the flexibility and ...
Characterization Of Slm Printed 316l Stainless Steel And Investigation Of Microlattice Geometry, 2017 California Polytechnic State University, San Luis Obispo
Characterization Of Slm Printed 316l Stainless Steel And Investigation Of Microlattice Geometry, Finley H. Marbury
The goal of this project was firstly to characterize Cal Poly’s SLM printed 316L stainless steel. SEM analysis showed Cal Poly’s as-printed 316L material to have a cellular dendritic microstructure containing mostly austenite and a small amount of δ-ferrite. After being heat treated to eliminate warp, its yeild and ultimate tensile strength were on par with the literature, however higher modulus and lower elongation were observed. XRD analysis confirmed residual stresses in the material, and that grains are preferentially oriented in both heat treated and non heat treated samples. The amount of porosity in the material was found ...
Invariant-Based Method For Improving Efficiency Of Mechanical Testing In Aerospace Certification Of Carbon Fiber-Epoxy Composites, 2017 California Polytechnic State University, San Luis Obispo
Invariant-Based Method For Improving Efficiency Of Mechanical Testing In Aerospace Certification Of Carbon Fiber-Epoxy Composites, Alyssa Rina Gruezo, Erika Gabrielle Hansen
The current challenge with qualification of carbon fiber composites in the aerospace industry would be the low efficiency of testing hundreds of samples. The Trace Theory strives to streamline the qualification process by utilizing a material’s Trace to predict properties of composites using Excel programs and basis data. To test this theory, predicted properties from the program, QuickLam, were compared to experimental data. Unidirectional 0° (T1), unidirectional 90° (T2), quasi-isotropic (T3), and hard quasi-isotropic (T4) laminates were made using HexTowR carbon fiber and TC250 resin provided by TenCate Advanced Composites. Tensile and compression tests were done according to ASTM ...
Development Of Low Cost Braze Alloys For Aerospace Applications, 2017 California Polytechnic State University, San Luis Obispo
Development Of Low Cost Braze Alloys For Aerospace Applications, Alyssa M. Elliott, Sandy Babich, Blake Whitmee
Non-precious metal braze alloys can help lower the cost of brazing, which is a commonly-used joining process in the aerospace industry. A-286, a stainless steel superalloy, and Inconel© 718, a nickel-based superalloy, are both commonly used alloys at Aerojet Rocketdyne. Both alloys were brazed into butt joints using nickel-based braze alloys: AMS 4776, 4777, and 4778. The brazed samples were machined into a modified version of the ASTM E8 subsize specimen samples and tensile tested to compare the strength and calculated elongation of the brazed samples to the base metals’ properties. All of the brazed samples fractured at the joint ...
Bear Minimum: Ultralight Composite Bear Canister, 2017 California Polytechnic State University, San Luis Obispo
Bear Minimum: Ultralight Composite Bear Canister, Rama B. Adajian, Adam C. Eisenbarth
The ultralight backpacking community needs a strong, easy to use, safe bear canister that is lighter than current market products for trekking in the backcountry. A full design of the lid for the bear canister is to be completed. This includes the locking mechanism to ensure it is bear proof, the interface between the lid and the canister, and the structure of the lid so it passes the strength and weight specifications. The lid, along with the already designed canister body, is to be manufactured with formal documentation. The lid will initially be tested separately and then with the canister ...
Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, 2017 University of New Mexico
Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, Mohammad Reza Zamani Kouhpanji
Electrical and Computer Engineering ETDs
Study and prediction of classical and non-classical mechanical properties of GaN is crucial due to the potential application of GaN nanowires (NWs) in piezoelectric, probe-based nanometrology, and nanolithography areas. GaN is mainly grown on sapphire substrates whose lattice constant and thermal expansion coefficient are significantly different from GaN. These discrepancies cause mechanical defects and high residual stresses and strains in GaN, which reduce its quantum efficiency.
Specifically, for nanoscale applications, the mechanical properties of materials differ significantly compared to the bulk properties due to size-effects. Therefore, it is essential to investigate the mechanical properties of GaN NWs using the non-classical ...
Study Of Knowledge-Based System (Kbs) And Decision Making Methodologies In Materials Selection For Lightweight Aircraft Metallic Structures, Pashupati R. Adhikari, Reza Mirshams
Journal of Applied Science & Engineering Technology
This paper presents an overview of knowledge-based system (KBS) in the context of decision making methodologies used in materials selection for the design of light weight aircraft metallic structures. Overall aircraft weight reduction means substantially less fuel consumption and better efficiency. Part of the solution to this problem is to find a way to reduce overall weight of metallic structures in the aircraft. Two distinct multiple criteria decision making (MCDM) methodologies are presented with examples featuring a set of short-listed materials suitable in the design of the structures. Pre-defined constraint values, mainly mechanical properties, are employed as relevant attributes satisfying ...
Deposition Velocity Dependence On Urban Morphology, 2017 Portland State University
Deposition Velocity Dependence On Urban Morphology, Rawand Muzafar Rasheed
Undergraduate Research & Mentoring Program
Understanding the interactions between the atmospheric boundary layer and urban structures provides insights into emerging problems such as green building design as well as dispersion and deposition of pollutants on urban structures. Characterization of deposition velocity dependence through the naphthalene sublimation method on model urban structures is conducted herein where the analogous fundamental transport mechanisms of momentum and mass transport is obtained via mass of naphthalene transferred. Via wind tunnel experiments, results show that deposition velocity of naphthalene from urban structures increases with increased number of urban structures ahead of the point of investigation. This is attributed to the wakes ...
Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, 2017 University of Southern Mississippi
Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles
Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of ...