Dissertations / Theses: 'Aging properties'

1

Chau, Nguyen Lan. "Aging Effects on the Mechanical Properties of Waste Landfills." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/179380.

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2

Chang, Geng-Wen. "Physical aging in the mechanical properties of miscible polymer blends." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056644954.

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3

Cho, Sung-Woo. "Aging and heat-sealing properties of films based on wheat gluten /." Stockholm : Kemi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4489.

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4

Plunkett, Richard. "Assessment of residual composite properties as influenced by thermal mechanical aging." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11072008-063142/.

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5

Punsalan, David Troy. "A sorption and dilation investigation of amorphous glassy polymers and physical aging." Access restricted to users with UT Austin EID, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035168.

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6

Clements, Thomas Martin. "THE EFFECT OF LOOSE MIX AGING ON THE PERFORMANCE PROPERTIES OF WARM ASPHALTS." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/120.

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Recent improvements in warm mix asphalt technologies have spurred an aggressive adoption of these new practices within the asphalt paving industry. Concerns have arisen among federal and state agencies about the effects of this line of products on the performance of asphalt pavements. An investigation of the effects of lowering mixing, aging and compactions temperatures while varying the loose mix aging time was performed. Hamburg Wheel Tracking, Flow Number, Dynamic Modulus and Fracture Energy testing were used to evaluate mechanistic properties of the materials.

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Whitley, Karen Suzanne. "Tensile and Compressive Mechanical Behavior of IM7/PETI-5 at Cryogenic Temperatures." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35944.

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In order for future space transportation vehicles to be considered economically viable, the extensive use of lightweight materials is critical. For spacecraft with liquid fueled rocket engines, one area identified as a potential source for significant weight reduction is the replacement of traditional metallic cryogenic fuel tanks with newer designs based on polymer matrix composites. For long-term applications such as those dictated by manned, reusable launch vehicles, an efficient cryo-tank design must ensure a safe and reliable operating environment. To execute this design, extensive experimental data must be collected on the lifetime durability of PMC's subjected to realistic thermal and mechanical environments. However, since polymer matrix composites (PMC's) have seen limited use as structural materials in the extreme environment of cryogenic tanks, the available literature provides few sources of experimental data on the strength, stiffness, and durability of PMC's operating at cryogenic temperatures.

It is recognized that a broad spectrum of factors influence the mechanical properties of PMC's including material selection, composite fabrication and handling, aging or preconditioning, specimen preparation, laminate ply lay-up, and test procedures. It is the intent of this thesis to investigate and report performance of PMC's in cryogenic environments by providing analysis of results from experimental data developed from a series of thermal/mechanical tests. The selected test conditions represented a range of exposure times, loads and temperatures similar to those experienced during the lifetime of a cryogenic, hydrogen fuel tank. Fundamental, lamina-level material properties along with properties of typical design laminates were measured, analyzed, and correlated against test environments. Material stiffness, strength, and damage, will be given as a function of both cryogenic test temperatures and pre-test cryogenic aging conditions.

This study focused on test temperature, preconditioning methods, and laminate configuration as the primary test variables. The material used in the study, (IM7/PETI-5), is an advanced carbon fiber, thermoplastic polyimide composite.
Master of Science

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8

Sivakulam, Sivakkolunthar. "Impact of anti-strip additives on long-term aging properties of asphalt mixtures." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1472979.

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9

Ali, Mahdi. "Study of the bitumen aging effects on the rheological properties and fatigue behavior." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16255/.

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A study of bitumen aging effects on the rheological properties and fatigue behavior is carried out on five polymer modified bitumen provided by an oil company. Dynamic Shear Rheometer (DSR), is used to perform advanced experimental investigation. It allows practicing frequency sweep tests, fatigue tests and time sweep tests. Polymer modified bitumen with different percentage of SBS with or without the presence of crumb rubber are tested before and after short and long aging processes. Master curves were generated based on frequency sweep tests data, they are studied, and a comparison was conducted between each bitumen before and after aging. In this thesis, the DSR is presented, as well as the testing procedure and the tested materials. A fatigue life analysis of the results, based on the use of two different criteria, the first criterion is classically used: it consists in defining the failure as a 50% loss of the initial stiffness. The other criteria based on dissipated energy data. This thesis provides results which show the effects of several factors on fatigue and healing response such as bitumen type, ageing, the presence of rubber and polymer modification.

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Haynes, Premi. "TRANSMURAL HETEROGENEITY OF CELLULAR LEVEL CARDIAC CONTRACTILE PROPERTIES IN AGING AND HEART FAILURE." UKnowledge, 2014. http://uknowledge.uky.edu/physiology_etds/16.

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The left ventricle of the heart relaxes when it fills with blood and contracts to eject blood into circulation to meet the body’s metabolic demands. Dysfunction in either relaxation or contraction of the left ventricle can lead to heart failure. Transmural heterogeneity is thought to contribute to normal ventricular wall motion but it is not well understood how transmural modifications affect the failing left ventricle. The overall hypothesis of this dissertation is that normal left ventricles exhibit transmural heterogeneity in cellular level contractile properties and with aging and heart failure there are region-specific changes in cellular level contractile mechanisms. Age is the biggest risk factor associated with heart failure and therefore we investigated transmural changes in Ca2+ handling and contractile proteins in aging F344 rats before the onset of heart failure. We found that in 22-month old F344 rats there is a region-specific decrease in cardiac troponin I phosphorylation in the sub-epicardium that may contribute to slowed myocyte relaxation in the sub-epicardial cells of the same age. We then investigated the transmural patterns of contractile properties in myocardial tissue samples from patients with heart failure. Force and power output reduced most significantly in the samples from the mid-myocardial region when compared to sub-epicardium and sub-endocardium of the failing hearts. There was a region-specific increase in fibrosis is the mid-myocardium of the failing hearts. Myocardial power output was correlated with key sarcomeric proteins including cardiac troponin I, desmin and myosin light chain-1. The results in this dissertation reveal novel region-specific modifications in contractile properties in aging and heart failure. These transmural effects can potentially contribute to disruption in normal wall motion and lead to ventricular dysfunction.

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11

Guo, Guannan. "Aluminum microstructure evolution and effects on mechanical properties in quenching and aging process." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/334.

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"High strength aluminum alloys are recently widely used in aircraft, automobile and construction industry fields. Typical T6 heat treatment process can be applied to improve the heat treatable aluminum alloy in order to facilitate the formation of prime strengthening precipitate phases. Critical steps in T6 heat treatment process include solution treatment, quenching and aging. Due to high thermal gradients in quenching process and aging process, large thermal stress will remain in the matrix and may bring unexpected deformation or distortion in further machining. Therefore, in order to predict the thermal stress effects, constitutive model and precipitate hardening model are needed to simulate the mechanical properties of alloy. In this dissertation, an optimized constitutive model, which is used to describe the mechanical behavior during quenching and intermediate period of quenching and aging process, was given based on constitutive models with Zenor-Holloman parameter. Modification for constitutive model is based on the microstructure model, which is developed for the quenching and aging processes. Quench factor analysis method was applied to describe the microstructure evolution and volume fraction of primary precipitate phases during quenching process. Some experimental phenomena are discussed and explained by precipitate distributions. Classical precipitate hardening models were reviewed and two models were selected for Al-Cu-Mn alloy aging treatment. Thermal growth model and Euler algorithm were used to improve the accuracy and the selected precipitate hardening models were validated by yield stress and microstructure observations of Al-Cu-Mn aging response experiments."

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12

Shimer, Matthew Timothy. "Nonequilibrium Relaxation and Aging Scaling Properties of the Coulomb Glass and Bose Glass." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28926.

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We use Monte Carlo simulations in order to investigate the density of states and the two-time density autocorrelation function for the two- and three-dimensional Coulomb glass as well as the Bose glass phase of flux lines in type-II superconductors. We find a very fast forming gap in the density of states and explore the dependence of temperature and filling fraction. By studying two scaling methods, we find that the nonequilibrium relaxation properties can be described sufficiently by a full-aging scaling analysis. The scaling exponents depend on both temperature and filling fraction, and are thus non-universal. We look at the trends of these exponents and found that as either the temperature decreases or the filling fraction deviates more from half-filling, the exponents reflect slower relaxation kinetics. With two separate interaction potentials, a comparison of relaxation rates and the gap in the density of states is made.
Ph. D.

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13

Robert, Mylène. "Impact of degradation and aging on properties of PFSA membranes for fuel cells." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0004.

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Bien que déjà présentées comme une technologie sûre et propre, les piles à combustible à membrane échangeuse de protons (PEMFC) restent confrontées à de solides verrous en termes de durabilité et de fiabilité, limitant leur commercialisation à large échelle. De nombreuses études ont déjà permis d’affiner la compréhension des phénomènes de vieillissement et ont permis de désigner la dégradation de la membrane comme l’un des principaux facteurs limitant la durée de vie des PEMFC. Cette étude vise à apporter des éléments de compréhension sur les mécanismes de dégradations chimique et mécanique par l’intermédiaire de protocoles de vieillissement ex-situ, ainsi qu’à comprendre l’impact de ces dégradations sur la structure et les propriétés fonctionnelles des membranes. Dans un premier temps, il a été nécessaire de clarifier l’influence de la réaction de Fenton, un protocole de vieillissement ex-situ largement reconnu dans la littérature, sur la dégradation chimique des membranes Nafion™. Les résultats ont confirmé que la concentration en réactifs de Fenton influençait significativement la décomposition chimique du polymère, à la fois d’un point de vue chimique et morphologique. Par la suite, nous avons choisi de suivre l’évolution de la dégradation chimique des membranes Nafion™ en fonction du temps et d’étudier son impact sur la structure de la membrane, ses propriétés de sorption et de diffusion de l’eau ainsi que son fonctionnement en pile. À cet égard, différentes techniques de caractérisation telles que la spectroscopie RMN 19F ou 1H ainsi que la spectroscopie FTIR ont permis de corréler les propriétés physico-chimiques de la membrane à ses caractéristiques structurelles et de mettre ainsi en évidence plusieurs marqueurs de la dégradation chimique. Enfin, un dispositif sur-mesure a été conçu afin d’étudier l’impact des contraintes mécanique et chimique conjointes sur les membranes Nafion™. L’objectif de ce dispositif était de reproduire des conditions de vieillissement proches de celles rencontrées lors du fonctionnement en pile
Although proton-exchange membrane fuel cells (PEMFC) are nowadays considered as a safe and clean energy technology, they still suffer from durability and reliability issues restricting their widespread commercialization. Innumerable studies have already led to a better understanding of aging phenomena and highlighted membrane degradation as one of the main factors limiting PEMFC lifetime. This study aims at bringing some clarifications on the chemical and mechanical degradation mechanisms of membranes through ex-situ aging protocols as well as understanding the impact of these degradations on the membrane structure and functional properties. First, it was necessary to clarify the influence of Fenton’s reaction, an ex-situ aging protocol widely recognized in the literature, on the chemical degradation of Nafion™ membranes. The results confirmed that Fenton’s reagents concentration significantly influenced polymer chemical decomposition, both from a chemical and morphological point of view. Subsequently, we chose to monitor the evolution of pure chemical degradation of Nafion™ membranes as a function of time and to study its impact on the membrane structure, water sorption and diffusion properties, as well as operability in fuel cells. In that respect, various characterization techniques such as 19F or 1H-NMR as well as FTIR spectroscopies allowed us to correlate physico-chemical properties of the membrane to its structural characteristics and to thus highlight several indicators of chemical degradation. Finally, a custom-made device has been developed to study the impact of conjoint mechanical and chemical stress on Nafion™ membranes. The objective of this device was to replicate aging conditions close to those encountered during fuel cell operation

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14

Yang, Sha. "Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/72985.

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The time dependence of the physical properties of ethylene/1-octene (EO)-copolymers after primary crystallization is investigated by calorimetry, density, and creep measurements. The temporal evolution of the multiple melting of EO-copolymers is monitored by differential scanning calorimetry. The low temperature endotherm displays an evolution similar to that observed for the enthalpy recovery in glasses after physical aging. Using this analogy, a calorimetry-aging rate is defined, which quantifies the change in the low endotherm temperature with time. Similarly a density-aging rate is defined from the evolution of density with time. A non-classical creep behavior is observed for short aging times, consistent with crystallization-induced shrinkage. The change in crystallinity during aging leads to a change in the shape of the relaxation spectrum. Hence, analysis of creep data cannot be carried out using Struik's superposition method. For both short and long aging times, the creep rate exhibits a dependence on copolymer composition similar to those associated with the calorimetry- and the density-aging rates, suggesting a common origin for the evolution of the low endotherm, the creep behavior and the bulk density. The calorimetry, density, and creep data are reexamined based on the following assumptions: First, a single population of small crystals is formed during crystallization at low temperature; Second, these small crystals increase in stability under isothermal conditions, easily melt and recrystallize during heating and serve as efficient thermo-reversible cross-links to increase the conformational constraints in the residual amorphous fraction. These assumptions appear to be consistent with all observations made to date.
Master of Science

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15

McKiernan, Erin C., and Diano F. Marrone. "CA1 pyramidal cells have diverse biophysical properties, affected by development, experience, and aging." PEERJ INC, 2017. http://hdl.handle.net/10150/625990.

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Neuron types (e.g., pyramidal cells) within one area of the brain are often considered homogeneous, despite variability in their biophysical properties. Here we review literature demonstrating variability in the electrical activity of CA1 hippocampal pyramidal cells (PCs), including responses to somatic current injection, synaptic stimulation, and spontaneous network-related activity. In addition, we describe how responses of CA1 PCs vary with development, experience, and aging, and some of the underlying ionic currents responsible. Finally, we suggest directions that may be the most impactful in expanding this knowledge, including the use of text and data mining to systematically study cellular heterogeneity in more depth; dynamical systems theory to understand and potentially classify neuron firing patterns; and mathematical modeling to study the interaction between cellular properties and network output. Our goals are to provide a synthesis of the literature for experimentalists studying CA1 PCs, to give theorists an idea of the rich diversity of behaviors models may need to reproduce to accurately represent these cells, and to provide suggestions for future research.

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Laot, Christelle Marie. "Gas transport properties in polycarbonate - Influence of the cooling rate, physical aging, and orientation." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29844.

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The objective of this research work was to understand the molecular mechanism of gas transport through amorphous glassy polymers. Especially, emphasis was placed on determining whether or not gas transport in amorphous glassy polymers is directly correlated with the free volume content. Free volume arguments are indeed commonly used to explain the gas transport process. The gas transport properties of bisphenol-A polycarbonate films were examined as a function of the cooling rate, physical aging, and orientation. Such conditions affect the free volume content and its size and shape distribution. Results obtained from permeation experiments were accompanied with dynamic mechanical and density measurements. The experimental results suggest that the diffusion coefficient of small gas molecules in glassy polycarbonate is influenced by the local dynamics or mobility of the polymer chains rather than by the overall free volume content. Indeed, the diffusion coefficient of nitrogen for instance was reduced in fast-cooled samples, despite of the fact that those samples possessed a greater overall free volume content. Fast cooling rates may generate highly restricted conformations which hinder local motions, and therefore tend to increase the activation energy of diffusion. As expected, the greater the free volume content, the greater was the solubility coefficient. The increase in the polymer relaxation times with aging time is believed to restrict the local chain motions, leading to enhanced activation energies of diffusion, and therefore to reduced diffusion coefficients. The change in the solubility coefficients with physical aging revealed that the aging process might not affect all the cavity sizes in polycarbonate equally. According to free volume arguments, one would anticipate that the physical aging of fast-cooled samples (which possess more free volume) should be enhanced compared to that of slowly-cooled samples. Quite interestingly, the decrease in the diffusion coefficient with aging was found to occur much slower in fast-cooled samples, despite of the higher initial free volume content. In contrast, properties directly related to the free volume content, such as density or isothermal DMTA measurements actually showed a greater aging rate in the sample containing the greatest amount of free volume. Slow-cooled samples that are in a low energy conformational state may loose their internal degrees of freedom more rapidly, due to the closer interchain packing and the possibly restricted segmental motions. Studies dealing with orientation and gas transport were complicated by several factors. For instance the fact that the permeation experiments were performed perpendicularly to the orientation of the chains and not along the orientation axis limited the sensitivity of the gas transport properties to orientation. This work points out that dynamic rather than static models should be developed to predict the gas transport phenomenon.
Ph. D.

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17

Chander, Kunal. "Effects of aging on dentin bonding and mechanical properties of restorative glass ionomer cements." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58839.

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Objectives: To examine changes in shear bond strength to dentin (SBS), flexural strength (FS) and diametral tensile strength (DTS) of four restorative glass ionomer cements: Fuji II LC (GC/America), Equia (GC/America), Ketac Nano (3M/ESPE), and Ketac Molar (3M/ESPE) after aging in artificial saliva. Materials and Methods: For SBS testing, sound extracted human permanent molars were ground to flat occlusal dentin surfaces and fixed in circular molds with auto-cured acrylic resin.. Teeth were randomly divided into four groups: Fuji II LC, Equia, Ketac Nano, Ketac Molar. For each dentin surface, two glass ionomer cylinders were bonded. Specimens were stored in artificial saliva (37°C) and tested at 24-hour and 6-month time points (Shear Testing Machine, Bisco). For each material, FS bars (25mm x 2mm x 2mm) and DS discs (4mm x 2mm) were fabricated, stored in artificial saliva (37°C), and tested at 24-hour and 6-month time points. (Shimadzu). An additional FS study was conducted with glass ionomer specimens, stored either in distilled water or artificial saliva (37°C), and tested at 24-hour and 2-month time points. (Shimadzu). Data analysis included two-way ANOVA (p<0.05) with post-hoc Tukey’s tests to compare interactions. Results: There were no significant differences in SBS after 6 months storage, except for Ketac Nano, which showed a significant decrease in bond strength after aging. There were no differences in SBS among the four glass ionomers, at 24 hours or 6 months saliva storage. The diametral tensile strength values did not change significantly after aging except for Fuji II LC. All materials had a significant increase in flexural strength after aging regardless of the storage media (water or saliva). Fuji II LC had significantly higher DS and FS compared to other materials, at both 24 hours and 6 months storage. Conclusions: Aging did not affect SBS of materials except Ketac Nano. Flexural strength of all glass ionomer cements increased over time. Storage media did not affect flexural strength properties. Diametral tensile strength remained unchanged over time for all materials. Overall, Fuji II LC had superior mechanical properties compared to other materials.
Dentistry, Faculty of
Graduate

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18

Alcorn, Justin Dow. "Osteogenic effect of electric muscle stimulation as a countermeasure during hindlimb unloading." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5816.

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Rats that undergo hindlimb unloading (HU) as a simulation for space flight experience bone changes similar to astronauts in microgravity. The purpose of this research was to assess whether an exercise countermeasure would be effective in preventing or mitigating bone degradation during HU. Controlled electrical muscle stimulation was applied to the lower left hindlimb to simulate resistive exercise. Adult 6-mo. old male rats were assigned to 3 groups of 12 each: hindlimb unloaded (HU), aging cage control (CC), and baseline (BL). The CC group was pair-fed to match the nutritional intake of HU animals during the 28 days of the study. The left leg was exercised 3 days a week for the duration of the study, with the unexercised right leg serving as a contra-lateral control. Mechanical tests were conducted to assess the strength of cancellous bone in the proximal tibia metaphysis. Although isolated specimens of cancellous bone are not feasible, reduced platen compression (RPC) was employed to directly load only the cancellous core region of each specimen. There was no significant difference in ultimate stress or elastic modulus between BL, CC, and HU-Ex (exercised). However, HU-Ex results were dramatically and significantly higher than HU-No Ex (contra-lateral unexercised control) for both ultimate stress (68%) and elastic modulus (81%). It is also notable that ultimate stress was 32% higher (but not statistically significant) for HU-Ex compared to CC. The total bone mineral density in the tibial metaphysis was significantly larger, 11%, in the HUEx compared to the HU-No Ex group's values. The results clearly demonstrate the efficacy of the exercise protocol in preventing the substantial mechanical deterioration induced by HU.

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Donato, Anthony John. "Effects of aging and exercise training on structural and vasoconstrictor properties of skeletal muscle arterioles." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1290.

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Aging is associated with increases in regional and systemic vascular resistance and arterial blood pressure. One possible mechanism through which these age-associated alterations occur is enhanced vasoconstrictor responsiveness, or alterations in the structural properties of the resistance vasculature. We hypothesized that stiffness and vasoconstriction would be greater in skeletal muscle arterioles from old rats, and that endurance exercise training would ameliorate the associated with aging alterations. METHODS: Young sedentary (YS; 4 months), old sedentary (OS; 24 months), young trained (YT) and old trained (OT) male Fischer 344 rats were used. Training modality was treadmill exercise at 15 m/min up a 15o incline, 5 days/wk for 12wks. Skeletal muscle first-order arterioles were isolated for in vitro experimentation. Intraluminal diameter was measured in response to the cumulative addition of endothelin-1, norepinephrine, KCl, and isoproterenol. Stiffness was measure by examining the arterioles' stress and strain relation to increased luminal pressure in Ca++ free solution. RESULTS: Skeletal muscle arterioles had augmented vasoconstriction to endothelin-1 and norepinephrine. Adrenergic vasodilation was diminished in aged rat arterioles. Stiffness increased with age. Exercise training ameliorated the age-associated changes in stiffness and norepinephrine vasoconstriction. Exercise training did not alter endothelin-1 vasoconstriction or adrenergic vasodilation. CONCLUSIONS: These findings suggest that enhanced vascular sensitivity to vasoconstrictors and increased arteriole stiffness may play a role in the increase in skeletal muscle and systemic vascular resistance and, thus, contribute to the elevated blood pressure which occurs in aging humans. These results also demonstrate some of the cardioprotective effects of exercise training.

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McCaig, Michael Scott. "Effect of bromine substitution, physical aging and crosslinking on the gas transport properties of polyarylates /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Rahbar-Rastegar, Reyhaneh. "Cracking in Asphalt Pavements| Impact of Component Properties and Aging on Fatigue and Thermal Cracking." Thesis, University of New Hampshire, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10622119.

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Cracking in asphalt pavements is one of the most common and critical pavement distresses. Cracks let the water penetrate from the surface to underlying layers resulting in shorter pavement service life and poor riding quality. There are various factors that affect the cracking potential of asphalt mixtures including the properties of asphalt components, mix design factors, loading time and loading mode, temperature, stress state, and aging. While several researchers have conducted studies investigating the cracking of asphalt mixtures, the effective parameters are not all well understood to allow engineers to design and construct more resistant pavements against cracking.

The work presented in this dissertation provides some additional insights into the effects of component properties and aging condition on asphalt cracking. The cracking susceptibility of hot mix asphalt (HMA) is evaluated through the experimental testing and numerical modeling on mixtures produced either in design (laboratory) or production (plant) stage. Various criteria and approaches for the prediction of cracking in asphalt binder and asphalt mixture are assessed and their correlation are discussed. Different levels of aging in laboratory are simulated, and the effects of long term oven aging (LTOA) on linear viscoelastic parameters, fatigue and fracture characteristics of asphalt mixtures are explored. The uniaxial tensile fatigue testing based on simplified viscoelastic continuum damage (SVECD) approach is conducted to characterize fatigue behavior, and semi circular bending (SCB), disc-shaped compact tension (DCT) testing and cohesive zone model are used to evaluate thermal cracking in asphalt mixtures.

This dissertation makes a good contribution in improvement of available approaches for evaluation of cracking potential of asphalt pavements and allows for assessment of different mixtures at early stage of material selection. The results of this study can lead to develop a new parameter to predict fatigue and thermal cracking susceptibility of flexible pavements in performance-based specifications, resulting in a better ride quality and cost saving for contractors and taxpayers.

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Linero, Jiménez Adriano. "DEVELOPMENT OF A MODEL OF THE DEGRADATION OF THE MECHANICAL PROPERTIES OF POLYOXYMETHYLENE (POM) IN THE PRESENCE OF BIODIESEL." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-10160.

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This project analyses the impact in the mechanical properties of Polyoxymethylene (POM) of three different blends of biodiesels: B0 with 0% of Rapeseed Methyl-ester (RME), B20 with 20% of RME and B100 with 100% of RME. Polyoxymethylene specimens have been subjected to an accelerated aging during 1600 hours at 85ºC. This is the equivalent to 20 years of life time. In addition, a thermal oxidation in air at the same temperature has been performed to check the impact of the temperature in the final degradation.Three different methods have been performed to calculate the diffusion rate, however and one of them has been selected for its reliable results. The second Fick´s law have been chosen to model the diffusion. The diffusion rate has been calculated for the B20 and B100 blend due to the B0 blend has a non-constant diffusion rate. B20 shows also some divergence while B100 fits the Fickian behaviour.A Finite Different approximation method has been used to predict the concentration profiles of the diffusion process of B20 blend. They have been compared with the results of the IR Microscope, with a clear misalignment between the expected and the actual values.Tensile tests have been done in different stages of the test to check the stress-strain behaviour of the specimens for each aging type. The most relevant parameter of degradation is the Elongation At Break (EAB), which decrease considerably a cause of the embrittlement. A study of the real stress-strain has been also done to assure the real behaviour of the material.A fracture surface study through Scanning Electron Microscope (SEM) and Light Microscope has been done to assure the brittle behaviour with the aging and the changes in the structure of the material.The swelling behaviour has been also modelled, and the bases for a future FEM analysis have been exposed.

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Shabani, Amin. "Thermal and radiochemical of neat and ATH filled EPDM : establishment of structure/properties relationships." Phd thesis, Paris, ENSAM, 2013. http://pastel.archives-ouvertes.fr/pastel-00941289.

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EPDM elastomer is widely used as the insulation of low to medium voltage electrical cables used in power plants, for which the life-time prediction has been hampered by the lack of knowledge on structure/mechanical properties, and the nonexistence of pertinent criteria of structural failure. In an attempt to fill this gap, three EPDM matrices filled with 0, 33 and 100 phr of pristine and surface treated ATH were crosslinked by dicumyl peroxide at 170°C and, subsequently, aged thermally at 90,110 and 130°C, and radiochemically under 0.1, 1 and 10 kGy.h-1, in air. A multi-scale approach was employed to analyze the oxidation of EPDM at molecular scale, and to determine its consequences at macromolecular and macroscopic scales by using several complementary characterization techniques: FTIR spectrophotometry, differential calorimetry, rheometry in melt state, swelling test, uniaxial tensile testing, etc. The structure/properties relationships established in this study are capable to explain, in particular, the alteration of elastic and fracture properties of the EPDM matrices due to chain scissions, and the reinforcement of the filler/matrix interphases induced by the specific conditions of oxidation.

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Wang, Jason Lee. "Effects of aging and remodeling on bone microdamage formation." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37114.

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Skeletal fragility is characterized by low bone mass, negative changes in bone microarchitecture, and compromised tissue matrix properties, including accumulation of microdamage. Microdamage accumulates in vivo from daily physiological loading and is targeted for repair through a normal remodeling process, thus preventing microcrack growth and potential fracture. However, impaired remodeling is associated with aging and osteoporosis, resulting in an increased accumulation of microdamage which contributes to reduced bone mechanical properties. The current clinical method for assessing increased risk of fracture involves measuring bone mineral density (BMD) of the hip and spine, locations of trabecular bone where high rates of remodeling occur. The bisphosphonate alendronate (ALN) reduces clinical risk for fracture by significantly increasing BMD, but studies have shown a concomitant reduction in intrinsic properties that may be the underlying cause for recent reports of spontaneous fractures with long-term alendronate use. Another anti-resorptive agent called raloxifene (RAL) is a selective estrogen receptor modulator (SERM) and has been shown to modestly improve BMD while decreasing fracture risk to a similar degree as alendronate. The combination of RAL and ALN as a treatment for osteoporosis may provide the benefits of each drug without the negative effects of ALN. Therefore, the overall goal of this thesis was to address the effects of aging and anti-resorptive agents on the properties of bone through the formation of microdamage. Assessment of age-related effects on bone was conducted through quantification of microdamage progression. It was found that old bone results in greater incidences of microdamage progression, reflecting a compromised tissue matrix with reduced resistance to crack growth. Effects of combination treatment with RAL and ALN were evaluated through biomechanical testing, micro-CT imaging, and microdamage quantification. Results showed improved trabecular bone volume and ultimate load with positive effects on trabecular architecture. Combination treatment reduced the proportion of microdamage that may lead to catastrophic fracture, indicating an improvement in the local tissue matrix properties.

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Karakas, Mustafa Serdar. "Effect Of Aging On The Mechanical Properties Of Boron Carbide Particle Reinforced Aluminum Metal Matrix Composites." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608944/index.pdf.

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Metal matrix composites (MMCs) of Al - 4 wt.% Cu reinforced with different volumetric fractions of B4C particles were produced by hot pressing. The effect of aging temperature on the age hardening response of the composites was studied and compared with the characteristics exhibited by the matrix alloy. Reinforcement addition was found to considerably affect the age hardening behavior. Detailed transmission electron microscopy and differential scanning calorimetry observations were made to understand the aging response of the composites. The low strain rate and high strain rate deformation behavior of the MMCs were determined utilizing low velocity transverse rupture tests and true armor-piercing steel projectiles, respectively. Increasing the volume fraction of B4C led to a decrease in flexural strength. The flexural strength vs. strain rate plots showed a slight increase in strength followed by a decrease for all samples. The mechanical performance of the composites and the unreinforced alloy were greatly improved by heat treatment. The MMCs were found to be inferior to monolithic ceramics when used as facing plates in armors.

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26

Venkatadri, Vikram. "Quantitative assessment of long term aging effects on the mechanical properties of lead free solder joints." Diss., Online access via UMI:, 2009.

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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2009.
Includes bibliographical references.

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27

Hixon, Jeff. "Effects of thermal aging on Stress Corrosion Cracking and mechanical properties of stainless steel weld metals." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41270.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.
Includes bibliographical references (p. 589).
Stress Corrosion Cracking (SCC) in and around primary loop piping welds in Boiling Water Reactors has been observed worldwide as plants continue to operate at temperatures and pressures near 2880C (5500F) and 6.9 MPa (1000 PSI). An experimental program was designed to explore the effect of thermal aging on the SCC crack growth rate in weld materials for type 316 and 304 stainless steels. An autoclave facility was designed and constructed for the measurement of SCC crack growth rates under BWR conditions and testing was underway at the time of this writing. The effects of composition and thermal aging on mechanical properties (i.e. tensile, micro-hardness, nano-hardness, Jic, and Charpy-impact toughness) was in process and initial results show an increase in yield strength and a decrease in fracture toughness after aging for 1000 hours at 430 and 400 *C. Thermal aging results in no discernable changes to the 6-ferrite morphology when viewed optically at 500 X agnifications and in the scanning electron microscope.
by Jeff Hixon.
S.M.

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28

Heinze, Marvin H. "The effect of aging treatment on the microstructure and properties of copper-precipitation strengthened HSLA steel." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23189.

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Approved for public release; distribution is unlimited
The high strength low alloy (HSLA) steels which are being developed as replacements for the HY family of steels ire low carbon steels which derive their strength in part due to the precipitation of fine coherent copper particles formed during a quench and aging heat treatment. HSLA- 100 is being developed to meet the strength and oughness requirements of HY-100 but can be easily welded without preheat, thereby reducing fabrication costs. This investigation uses light and electron microscopy for microstructural characterization while tensile, Charpy, ind hardness tests are relied upon for the mechanical properties. The microstructure and mechanical characteristics }f HSLA- 100 after aging at several different temperatures was correlated. A high ductility and the minimum 100 csi yield strength was found after aging at 675 C, although this temperature was found to be close to the low jutectoid temperature displayed by HSLA- 100. Splitting was observed in the tensile fracture surfaces but the nechanical properties were not adversely affected.
http://archive.org/details/effectofagingtre00hein
Lieutenant, United States Navy

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29

Velikov, Vesselin Hristov Jr. "Time Dependent Properties of Semicrystalline Poly(Arylene Ether Ether Ketone) (Peek) Above and Below the Glass Transition." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/39845.

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Long time annealing of semicrystalline PEEK above the glass transition results in the observation of several time dependent phenomena - "physical aging", "secondary crystallization", "multiple melting" of lamellae with different thermal stability etc. Their interrelation - common origin and kinetics of development, is characterized extensively for the first time in this study.

The evolution of the crystallinity during the secondary crystallization process was monitored by DSC and density measurements. Crystallinity was characterized according to the standard two-phase model of semicrystalline polymers and analyzed with respect to the failure of the model to adequately describe the physical state of the polymer. A discrepancy was observed between DSC and density crystallinity values and their respective rates of development during the secondary crystallization stage.

WAXS reveals that the crystal density is not a physical constant, but depends on the crystallization and/or annealing temperature. Furthermore, the crystalline lamellae densify with time during crystallization and/or annealing. This observation leads to the conclusion that there is no one-to-one correspondence between density and crystallinity and necessitates the application of a revised equation for density crystallinity which accounts for the dynamics of crystal densification.

The characteristics of the low temperature endothermic peak in the DSC scan of PEEK (peak maximum, transition enthalpy etc.) were found to evolve with annealing time and temperature during the secondary crystallization process in a way similar to the kinetics of development of the enthalpy relaxation process in amorphous polymeric glasses.

This study reports for the first time in the literature the observation of "physical aging" above the glass transition in the case of PEEK (according to the definition of this term given by Struik). An extensive investigation of the "double melting"/"multiple melting" phenomenon, which is observed as a result of isothermal treatment of the polymer above Tg, was performed and several new observations reported.

After the end of the primary crystallization process, the semicrystalline polymer is a nonequilibrium system due to the fact that crystallinity is less than unity. The system's continuing approach to equilibrium and its response to mechanical perturbations follow kinetics similar to that of segmental relaxation below the glass transition.
Ph. D.

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30

Cierocka, Joanna, and Jiayue Tang. "Vibrational tests of preloaded rubber vibration isolators : A cam controlled displacement excitation." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-53703.

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Vibrations are very common phenomenon. It influences structures and generates acoustic noise which might be harmful to human beings. The vibration isolator was invented to reduce the effect from vibrations. However, the behavior of rubber material, which many vibration isolators are made of, is hard to predict. Consequently, vibration tests are needed to obtain the dynamic properties of rubber isolator.In this case, a six-year old LORD 2204-5 rubber isolator provided by Atlas Copco was tested. The aim of this paper is to obtain the FRF (Frequency Response Function) diagram which can describe the property of the rubber material. Moreover, the influence of aging of rubber material on the dynamic properties was studied.As the vibration test should simulate the working environment of the isolators that are both a static load from the structure and a dynamic force from the engine, a new excitation method was designed. The camshaft with the shape of an epitrochoid induced the sinusoidal signal of the isolator and the frame transferred the static load from the hydraulic machine. The artificial aging was performed in a hot air oven in 90°C for 42 hours, which according to Arrhenius equation should be equivalent to six years of natural aging. The vibration isolator was tested again after being aged.The obtained data showed that the aging process decreased the stiffness of the material. The results were corresponding with other studies regarding aging of rubber.

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Chaves, Jose Mauro. "Structural and functional properties of human [alpha]A-crystallin." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008d/chaves.pdf.

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Alin, Maishah. "Effect of rejuvenators on rheological properties of asphalt binders." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525216636988378.

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33

An, Ke. "Mechanical Properties and Electrochemical Durability of Solid Oxide Fuel Cells." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11088.

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The mechanical properties of unaged and aged constituent materials for solid oxide fuel cells were evaluated using microindentation, plate tensile, four-point bend, ball on ring and pressure on ring tests. The Vickers hardness of the anode, interconnect and electrolyte was determined before and after 1000 hours aging at 1000 oC in air. The fracture toughness KIC was found for the electrolyte materials. Finite element analysis (FEA) was validated and used to calculate the stress distribution and peak stress for the biaxial strength test. A Weibull analysis was carried out on the test/FEA-predicted peak stresses, and Weibull strength, modulus and material scale parameters were found for each test methodology. The methodologies were evaluated based on the results of the Weibull analysis and the pressure on ring test is preferred one for brittle thin film fracture strength testing. Half cell SOFCs with composite cathode (Pr0.7Sr0.3)MnO3Â±Î´ /8YSZ on the 8YSZ electrolyte were aged 1000 hours at 1000 oC in air with/without polarization and investigated using Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (B.E.T.) method and X-ray Diffraction (XRD). The performance of the half cell SOFCs degraded after aging with/without polarization compared to the initial state, which was ascribed to the decrease of the electrolyte conductivity. The current load was shown to have impact on the performance by slowing down the decreasing rate of the polarization resistance of the SOFCs. After aging, the microstructural properties - pore size and pore volume changed, and growth of grains was found on the (Pr0.7Sr0.3)MnO3 phases, which may have contributed to the decrease of the activation polarization by decreasing the capacitance and increasing the number of active sites. After aging the high frequency EIS arcs/peaks shifted to a lower frequency range, and the low frequency arcs/peaks became unapparent compared to before aging. A 3-D multiphysics finite element model was used to simulate the performance of the half cell SOFC. The effective exchange current density and the effective ionic conductivity of the cathodes showed much influence on the performance of the SOFC. Predicted and observed performance was compared. Suggestions were given for the further experiments on the composite cathode.
Ph. D.

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34

Klongcheongsan, Thananart. "Driven Magnetic Flux Lines in Type-II Superconductors: Nonequilibrium Steady States and Relaxation Properties." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26726.

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We investigate the nonequilibrium steady state of driven magnetic flux lines in type-II superconductors subject to strong point or columnar pinning centers and the aging dynamics of nonequilibrium relaxation process in the presence of weak point pinning centers. We employ a three-dimensional elastic line model and Metropolis Monte Carlo simulations. For the first part, we characterize the system by means of the force-velocity / current-voltage curve, static structure factor, mean vortex radius of gyration, number of double-kink and half-loop excitations, and velocity / voltage noise features. We compare the results for the above quantities for randomly distributed point and columnar defects. Most of both numerical works have been done in two-dimensional systems such as thin film in which the structure of flux lines is treated as a point-like particle. Our main point of investigation in this paper is to demonstrate that the vortex structure and its other transport properties may exhibit a remarkable variety of complex phenomena in three-dimensional or bulk superconductors. The second part devotes to the study of aging phenomena in the absence of a driving force in disordered superconductors with much weaker point disorder. By investigating the density autocorrelation function, we observe all three crucial properties of the aging phenomena; slow power-law relaxation, breaking of time-translation invariance, and the presence of the dynamical scaling. We measure the dynamical exponents b and lambda_c/z and compare to other work. We find exponent values increase for increasing pinning strength, smaller interaction range, lower temperature, and denser defect density while the exponents measured in other approach tend to decrease.
Ph. D.

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Olabarrieta, Idoia. "Strategies to improve the aging, barrier and mechanical properties of chitosan, whey and wheat gluten protein films." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208.

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Lewis, Christopher James. "Quantifying the effects of aging on the mecahnical properties of medical grade polycarbonate and UV cured adhesives /." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd571.pdf.

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Lewis, Christopher James. "Quantifying the Effects of Aging on the Mechanical Properties of Medical Grade Polycarbonate and UV Cured Adhesives." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/199.

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Advances in engineering polymer technology have created a generation of high strength-to-weight materials for medical applications, with virtually no adverse interactions with body fluids. Polycarbonate is a widely used engineering polymer, and is often used in connection with ultra-violet light (UV) cured adhesives. Because of the chemical complexity of polymers, little is known about their actual aging characteristics. By characterizing the effects of aging, storage environment, and sterilization on medical grade polycarbonate/adhesive system properties, more accurate failure predictions can be made. In this thesis, efforts to better understand the effects of accelerated aging on a medical grade polycarbonate and UV cured adhesive system are presented. A case study in which we applied our findings to improve an existing medical device is also described. The resin investigated was DOW Calibre 2081-15 MFR. The adhesives investigated were Dymax 190-M, Loctite 3311, and Loctite 3921. By adapting ASTM test standards, tests were developed to evaluate the effects one type of accelerated aging method had on the polymers. The polycarbonate resin experienced significant changes in material properties after sterilization. The biggest change was in percent elongation which went from 130% to 40%. The Dymax 190-M had the highest shear break values initially; however, the Loctite 3311 was more consistent. The Loctite material experienced a 15% decrease in shear break value over three years accelerated aging, while the Dymax material experienced a 35% decrease. The use of post sterilization or three year accelerated aging properties for polycarbonate designs is better than using published data. This ensures more accurate evaluation for the safety factor and failure profile. It was found that the accelerated aging method used in this study is reliable for general studies through two years, but accuracy declined significantly after this time. By using our findings we were able to significantly improve the case study assembly. Understanding how material properties change over time helped us identify the major contributors to part failure to create a more robust design and final product.

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38

Giard, Baptiste, and Sofia Karlsson. "Machine learning for the prediction of duplex stainless steel mechanical properties : Hardness evolution under low temperature aging." Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298415.

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Duplex stainless steels, DSS are stainless steels that consist of the two phases austenite and ferrite. The DSS have superb properties and are widely used in industries such as nuclear power and in pressure vessels, pipes and in pipelines. The use of DSS are limited due to embrittlement which occurs at temperatures from 250 to 550 oC. This imposes a general limited service temperature of 250 oC. The mechanism mainly responsible for the embrittlement is a phase separation occurring in the ferrite phase. Furthermore, there is a direct link between the phase separation and the mechanical properties: the ferrite hardness increases whereas the toughness decreases under low temperature aging. In this thesis, the low-temperature embrittlement of duplex stainless steels was studied through machine learning modelling and experimental hardness- and microscopy measurements. The resulting model describes the data with an accuracy, R-squared = 0.94. In combination with the experimental results, nickel was identified as an important parameter for the hardness evolution. This work aims to provide a fundamental study for understanding the importance of alloying elements on the phase separation in DSS, and provides a new methodology via a combination of machine learning and key experiments for the material design.
Duplexa rostfria stål är rostfria stål som består av de båda faserna ferrit och austenit. De har extraordinära egenskaper och används brett inom industrin, t ex. i kärnkraftverk och i tryckkärl och pipelines. Användningen av duplexa rostfria stål är begränsad p.g.a. försprödning som uppstår i legeringarna vid temperaturer mellan 250-550 oC, vilket medför att den tillåtna temperaturen vid användning begränsas till under 250 oC. Den främsta orsaken till försprödningen är en fasseparation i den ferrita fasen under åldring vid låg temperatur. Vidare leder fasseparationen till mekaniska förändringar i ferritfasen: hårdheten ökar medan segheten minskar. I den här rapporten undersöks försprödningen av duplexa rostfria stål vid åldring med hjälp av datormodellering med maskininlärning samt av experimentella hårdhets- och mikroskopiska mätningar. Modellen hade en noggrannhet (determinationsko- efficienten, R2) på 0.94. Resultatet från modellen visade tillsammans med de experimentella resultaten att nickel är ett legeringsämne som har stor betydelse för hårdhetsökningen. Detta arbete syftar till att utgöra en grundläggande studie för att förstå påverkan från olika legeringsämnen på fasseparationer i DSS, och bidrar med en ny metodik för materialdesign som kombinerar maskininlärning och utvaldaexperiment.
EIT RawMaterial Project ENDUREIT

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39

Highfill, Carrie. "Effects of subprimal, quality grade, and aging on display color and sensory properties of ground beef patties." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14946.

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Master of Science
Food Science
John Unruh
A factorial arrangement of treatments was used to evaluate the effects of two subprimal types (chuck roll and knuckle), two quality grades (Premium Choice and Select), and three vacuum storage aging times before processing (7, 21, and 42 d) on ground beef patty display color stability and sensory attributes. At the end of each aging time, four knuckles or two chuck rolls representing their respective quality grade categories were combined and ground to form a sample batch. After a final grind, patties were formed using a patty machine, packaged in overwrapped trays, and displayed in a coffin-type retail case under continuous fluorescent lighting. Ground beef patties from chuck roll and Premium Choice subprimals had brighter red visual color scores, less discoloration, and higher (P<0.05) L*, a*, b*, and chroma values than those from knuckle and Select subprimals, respectfully. With increased display time, patties became (P<0.05) darker red and more discolored and had decreased L*, a*, b*, a/b ratio, and chroma values and increased hue angle values. Ground beef patties from Select knuckle subprimals had greater (P<0.05) oxygen consumption rate (OCR) than those from Premium Choice chuck roll, Select chuck roll and Premium Choice knuckle subprimals. Patties from subprimals aged 42 d had a lower metmyoglobin reducing ability (MRA) than those from subprimals aged 7 and 21 d. Greater aging and display times had higher (P<0.05) aerobic and lactic acid plate counts. In addition, thiobarbituric acid reactive substances values increased (P<0.05) from 7 to 21 d of aging and from 0 to 24 h of display. Ground beef patties from Premium Choice subprimals had a higher MUFA:SFA ratio (P<0.05) than those from Select subprimals. All treatments had acceptable sensory panel results with minimal differences due to treatment. Lower (P<0.05) peak force values for slice shear force and Lee-Kramer were recorded for patties from chuck roll, Premium Choice, and 42 d aged subprimals than those from knuckle, Select, and 7 d aged subprimals, respectfully. Overall, Premium Choice chuck rolls aged for fewer days would result in the most color stability and extended display life.

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Beechko, Alexander Nicholas. "Effects of Life-Long Wheel Running Behavior on Plantar Flexor Contractile Properties." CSUSB ScholarWorks, 2019. https://scholarworks.lib.csusb.edu/etd/849.

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Aging in skeletal muscle is characterized by a loss in muscular performance. This is in part related to the direct loss of muscle mass due to senescence, known as sarcopenia. With age, skeletal muscles lose force production, contractile speed, and power production. The force velocity relationship of muscle is a product of force production and contraction speed, both of which decline with age; however, the mechanisms and trajectory of this decline are not well understood. Exercise has positive effects on muscle, and thus may assist in maintaining performance in old age. However, few long-term studies have been performed to examine the effects of life-long exercise on muscle contractile performance. In order to test the potential for life-long exercise to reduce the effects of again on muscle contractile performance, muscle performance was determined in control mice and mice selected for high voluntary wheel running at baseline, adult, and old ages. Peak isometric force declined with age in control (C) mice without exercise (P

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Uan-Zo-li, Julie Tammy. "The Effects of Structure, Humidity and Aging on the Mechanical Properties of Polymeric Ionomers for Fuel Cell Applications." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/36259.

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The purpose of this work was to investigate the effects of structure, humidity and aging on the mechanical behavior of Nafion® and Dais® ionomers. It was determined that the majority of the properties of these membranes were controlled by the formation and growth of the ionic clusters that were the direct result of the ionic nature of these materials. In the process of this study, the properties of Nafion® and sulfonated Dais® polymers were investigated by dynamic mechanical analysis and thermal gravimetric analysis and their water uptake and sorption and desorption isotherms were measured. A mastercurve and a shift factor plot were constructed for 60% sulfonated Dais® membrane. It was determined that an increase in the degree of sulfonation raised the glass transition temperature of these materials by facilitating the formation of the ionic clusters which acted as physical crosslinks, thereby reducing the mobility of polymeric chains. Water was found to effectively plasticize the membranes, especially in the case of Dais® materials, by reducing the storage modulus and decreasing the structural integrity of the ionomers. The effect of pre-treatment of Nafion® was investigated and the glass transition temperature was found to increase as a function of the severity of the treatment procedure. The maximum water uptakes were determined for virgin and aged Nafion® and Dais® membranes and their vapor phase water sorption diffusion coefficients were calculated. The sorption process was found to follow pseudo-Fickian behavior, while the movement of water out of the membranes during the desorption process was determined to be controlled by mechanisms other than diffusion. Lastly, the effect of exposure of Nafion® and 30% sulfonated Dais® membranes to the saturated environment at elevated temperatures was investigated and found to result in the increase in the glass transition temperature of the materials. Results of the exposure effects on the diffusion properties of Nafion® and Dais® were inconclusive. Preliminary findings attributed the changes in the properties of the materials to the counteractive actions of physical aging and the growth of the ionic clusters.
Master of Science

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42

Hahn, Daniel Robert. "Examination of the Aging Properties of Novel Cyanate Ester Thermosets and the Subsequent Evaluation of the Material under Application Conditions." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11158.

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Cyanate ester thermosetting resins are a novel family of materials for high technology and aerospace applications. The high glass transition temperatures available from cured cyanate ester networks and subsequently, their resistances to corrosive materials make these resins attractive for harsh environmental applications. These features of cyanate ester resins presented a threefold opportunity for investigation, namely: 1) establish a characterization technique for the long term mechanical properties of the cured resins, 2) develop a method for determining the effect of physical and chemical aging on these mechanical properties, and 3) evaluate the AroCy® B-10 cyanate ester resin from Ciba-Geigy for use in applications where temperatures could easily reach 177°C (300°F). Dynamic mechanical analysis used in a step isothermal mode was developed to characterize the mechanical properties of the cured resin and a family of isothermal modulus curves was established. These data were then shifted, following WLF theory, to create a master curve of storage modulus with respect to measurement frequency. The resultant master curves allowed the prediction of long term mechanical behavior of the resin networks via short duration, accelerated experimental tests. The test methodology and experimental procedures were especially useful in determining the effects of physical and chemical aging on the mechanical properties of the resin. Cured resins were aged in oxidative and inert atmospheres (air and nitrogen, respectively) for varying time and temperature to study the suitability of cyanate ester resins for harsh environmental applications. After aging, the samples were tested by DMA, DSC and TGA and master curves of their mechanical behavior were generated. The results were then grouped to form a family of master curves as a function of atmosphere, time and temperature. This approach allowed for the separation of the competing chemical and physical degradation processes and established the practical application conditions for this class of cross-linked polymers. Using the techniques established above, a model cyanate ester resin was selected based upon its chemical simplicity and availability. AroCy® B-10 cyanate ester resin manufactured commercially by Ciba-Geigy was evaluated for its application where temperatures could easily reach 177C. While this material was clearly unacceptable for the stated application conditions (especially in an oxygen rich atmosphere), its investigation provided experimental confirmation of the techniques developed. The test procedures and performance evaluation techniques described allow for the systematic assessment of not only the cyanate ester class of networking polymers, but any glass forming material, and a separation methodology for their concomitant chemical and physical degradation pathways.
Ph. D.

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Batterham, Ian, and n/a. "Office Copying 1950-1970 : thermographic processes, their deterioration and preservation." University of Canberra. School of Resource, Environmental & Heritage Sciences, 2000. http://erl.canberra.edu.au./public/adt-AUC20060607.171830.

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This work looks at a range of copying processes used between 1950 and 1970 and which can be gathered under the heading 'Thermography'. Thermography is a broad term covering those processes which utilise heat to produce their image. The main aims of the work were: to examine how and when each process was used; to determine the chemistry of each process; to examine the permanence of existing copies produced using the various processes; and to look at possible ways of improving the preservation prospects of these copies. These aims were addressed through both primary and secondary research mechanisms. Research included examination of documentary source material, seeking out persons with first hand knowledge of the development of the processes, as well as analysis of extant copies from the various processes. Finally a series of preliminary experiments into the aging properties of the papers and the possibilities of preservation through the use of protective materials were carried out.

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Kusumanindyah, Nur Andriani Pramudita. "Study of the physicochemical properties of an extinguishing powder for sodium fires : aging, fabrication, and mechanism of extinction." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0012/document.

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Le Commissariat à l’Energie atomique et aux énergies alternatives (CEA) a développé une poudre extinctrice efficace capable d'éteindre le feu de sodium. Elle est une poudre à base d'un mélange de carbonate de lithium (Li2CO3) et de carbonate de sodium à basse hydraté (Na2CO3.H2O) dans une proportion proche de l'eutectique, avec une température de fusion d'environ 500°C, associée à du graphite. Cependant, depuis le démantèlement de plusieurs anciennes installations de sodium, le CEA dispose d'un stock important de lots de poudre inutilisés. L'idée de réutiliser ces poudres initie la question sur leur efficacité pour éteindre un feu de sodium après un stockage à long terme. Cette étude a proposé des analyses physicochimiques de ces poudres afin d'identifier leurs compositions et les caractéristiques des différents lots. Les résultats mettent en évidence la présence de carbonate de lithium de sodium (LiNaCO3) et trona (Na2CO3.NaHCO3.2H2O) qui ne sont pas mentionnés dans le brevet. Les expériences de vieillissement ont été développées pour étudier le rôle de l'humidité et du dioxyde de carbone à l’air ambiant au cours du stockage. Les résultats montrent que LiNaCO3 est sensible à la présence d'humidité, capable de transformer en carbonate de lithium et le carbonate de sodium monohydrate, quant à celui-ci réagit avec de l'eau et du dioxyde de carbone pour former du trona. Une étude de la formation de LiNaCO3 a permis d’avoir la compréhension du procédé de fabrication de la poudre. Ce composé se trouve à se produire grâce aux réactions mécanochimiques entre Li2CO3 et Na2CO3.H2O au cours du processus de broyage. Le Chris(X)ti-Na installation expérimentale est construit pour comprendre les mécanismes d'extinction en particulier concernant le rôle des propriétés physicochimiques sur l'extinction. Deux étapes de mécanismes d'extinction sont proposés, qui comprend (1) la formation d'hydroxyde de sodium liquide (NaOH) et (2) la fusion des carbonates eutectique. La première étape peut se produire directement (par la réaction directe du trôna et / ou Na2CO3.H2O avec Na(g) et / ou Na2O(s)), soit indirectement (par l'intermédiaire de la réaction de décomposition du trôna et Na2CO3.H2O avant la réaction de H2O(g) libéré avec Na(g) et / ou Na2O(s)). Les deux réactions mènent la possibilité de la formation d'hydrogène (H2) qui pourrait être représenté par la flamme flash observée avant l'extinction. Ils contribuent également à la diminution rapide de la température due à la formation d'hydroxyde de sodium liquide (NaOH) en tant que couche protectrice. Cette couche est nécessaire pour couvrir la surface de sodium d'un contact prolongé avec de l'oxygène. La présence de trona semble ne pas altérer la capacité d'extinction de la poudre. Avec la même quantité de NaOH produit par les deux composés, trona libère plus de quantité de H2 et plus exothermique que celle de Na2CO3.H2O. Dans l'ensemble, 0,5-0,9g d'eau est nécessaire pour éteindre 19,6 cm2 de sodium feu en nappe, ce qui équivalent à 1-2g de NaOH. Sur la base de ces tests, la teneur minimale en eau nécessaire à l'extinction est 5.6w%. Les poudres dont la teneur en eau d'hydratation est proche de 13w% semblent plus susceptibles de produire une flamme vigoureuse élevée avant l'extinction. La deuxième étape est considérée comme étant plus lent que l'étape précédente. La couche de carbonates eutectique a une viscosité supérieure à celle de NaOH qui le rend moins avantageux pour former la couche étanche à la surface de sodium. Par conséquent, son rôle pourrait être moins important en particulier pour le feu de sodium ayant commencé à basse température. Néanmoins, son effet est considéré comme plus important lorsqu'il est appliqué au feu de sodium à température élevée (supérieure à 500°C). Enfin, la taille des particules apparemment ne démontre pas une contribution significative à la performance d'extinction outre qu’affecter les performances d'épandage
The French Atomic and alternatives Energy Commission (CEA) developed an effective powder capable of extinguishing sodium fire. It is a powder based on a mixture of lithium carbonate (Li2CO3) and low-hydrated sodium carbonate (Na2CO3.H2O) in a near eutectic proportion, with a melting temperature of around 500°C, associated with graphite. However, ever since the dismantling of several old sodium installations, CEA has at its disposal an important stock of unused powder batches. The idea of reutilizing these powders initiates the question about their efficiency to extinguish a sodium fire after long term storage. This study proposed the physicochemical analyses of these powders in order to identify their compositions and characteristics for different batches. The results highlight the presence of lithium sodium carbonate (LiNaCO3) and trona (Na2CO3.NaHCO3.2H2O), which are not mentioned in the patent. The aging experiments were developed to study the role of moisture and ambient carbon dioxide during the storage. The results showed that LiNaCO3 is sensitive to the presence of moisture, able to transform it into lithium carbonate and sodium carbonate monohydrate, meanwhile the latter reacts with water and carbon dioxide to form trona. A study of the formation of LiNaCO3 allowed the understanding of the fabrication method of the powder. This compound is found to be produced as the results of mechanochemical reactions between Li2CO3 and Na2CO3.H2O during the grinding process. The Chris(X)ti-Na experimental facility is built to understand the mechanisms of extinction especially related to the role of physicochemical properties on extinction. Two steps of extinction mechanisms are proposed that includes (1) the formation of liquid sodium hydroxide (NaOH) and (2) the melting of eutectic carbonates. The first step can happen directly (via the direct reaction of trona and/or Na2CO3.H2O with Na(g) and/or Na2O(s)) or indirectly (via the decomposition reaction of trona and Na2CO3.H2O prior to reaction of H2O(g) released with Na(g) and Na2O(s)). Both reactions explore the possibility of hydrogen (H2) formation that might be represented by the flash flame observed prior to extinction. They also contribute to the rapid decrease of temperature due to the formation of liquid sodium hydroxide (NaOH) as a protective layer. This layer is essential to cover the sodium surface from prolonged contact with oxygen. The presence of trona appears to be not altering the extinction capacity of the powder. With the same amount of NaOH produced by both compounds, trona releases more quantity of H2 and more exothermic in terms of energy release than that of Na2CO3.H2O. Overall, 0.5-0.9 g of water is necessary to extinguish 19.6 cm2 of sodium pool fire, which equivalent to 1-2g of NaOH. Based on these tests, the minimum water content required for extinction is 5.6w%. Meanwhile, powders whose hydration water content is close to 13w% seem more likely to produce a high vigorous H2 flame prior to the extinction. The second step is considered to be slower than the previous step. The eutectic carbonates layer has higher viscosity than NaOH that makes it less beneficial to form sealed layer on the sodium surface. Therefore, its role might be less significant especially for the sodium fire starts at low temperature. Nevertheless, the effect is considered to be more important when applied to sodium fire at higher temperature (more than 500°C). Finally, the particle size apparently doesn’t demonstrate a significant contribution in the extinguishing performance other than affecting the spreading performance

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45

Lin, Yu-Hui, and 林郁卉. "Studies on the aging properties of paper." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/44447640855255180261.

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46

Kucera, Shawn Anthony 1974. "Physical and chemical properties of acrylic polymers influencing physical aging." Thesis, 2007. http://hdl.handle.net/2152/3802.

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The influence of water soluble and insoluble stabilizing excipients on the physical stability of coated dosage forms was investigated in this study. The effect of the excipients on the thermal and physico-mechanical properties, and water vapor permeability of free films was studied, as was the influence of these excipients on the physical stability and release kinetics of coated pellets. The effect of water-soluble proteins, bovine serum albumin (BSA) and Type B gelatin, on the physical aging of Eudragit[trademark] RS/RL 30 D films was investigated. It was found that ionic interactions occurred above the isoelectric point of BSA and caused unstable films which showed accelerated decreases in drug release rate. The adjustment of the pH of the dispersion below the isoelectric point of BSA resulted in electrostatic repulsive charges that stabilized the drug release rate from coated dosage forms at both ambient and accelerated conditions. The addition of gelatin to the coating dispersion increased the drug release rate due to the formation of gel-domains through which the drug was able to easily diffuse. The influence of silicon dioxide on the stability of Eudragit[trademark] RS/RL 30 D films was investigated. Colloidal grades showed enhanced incorporation in the acrylic matrix; however, unstable films were formed. The addition of silicon dioxide with a larger particle size increased the permeability of the film and stabilization in drug release rate was attributed to constant water vapor permeability values of free films. The influence of ethylcellulose on the physical aging of Eudragit[trademark] NE 30 D coated pellets was studied. The two polymers were found to be substantially immiscible and the drug release rate of coated pellets was constant at both ambient and accelerated conditions which correlated to stabilizations in both the physico-mechanical properties and water vapor permeability of free films. Blending both Eudragit[trademark] NE 30 D and RS 30 D resulted in the formation of coherent films without the need of plasticizer. The two polymers were found to be miscible and both films and coated dosage forms were stable when stored below the glass transition temperature of the polymer blend. When films were stored above this temperature, instabilities occurred as a result of the further coalescence and densification of the polymer blend.

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Ma, ChouLong, and 馬肇隆. "Manufacturing and Aging Properties of Submicro Particulate Reinforced Aluminum Alloy." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/41022487900698236665.

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碩士
淡江大學
機械工程學系
88
The present research use the compocasting method to introduce the sub micro (0.05μm) Al2O3 particulate into 6061-aluminum alloy and the high temperature forging method to accomplished the casting. Than using the solid rotation and friction method to disperse the clustering 0.05μm Al2O3 particulate by seizing, inserting and the plastic atomic flow field into the friction bits. At last, mixed the friction bits with melted 6061-aluminum alloy and cast. 6061-aluminum alloy/0.05μm Al2O3 particulate composites with uniform particulate distribution can be manufactured by these three steps. Discussion the influence of aging hardening behavior resulted from different particulate contained (0wt%, 0.3wt%, 0.6wt%, 0.9wt%, and 0.3wt%) and different aging temperature. The result shows the peak-aging time of the composites decrease with increasing aging temperature, because the different thermal coefficient of the Al2O3 particulate and 6061-aluminum alloy provided the driving force to nucleation of precipitate. And the peak-aging hardness (HRB) also decreases with increasing aging temperature, because of over growth of precipitate. The hardness (HRB) of the composites decreases with increasing of the weight percent of the Al2O3 particulate. This is because of the composites influenced by the different thermal coefficient of the Al2O3 particulate and 6061-aluminum alloy, the fine grain size hardening resulted from the ceramic particulate and the dispersion hardening resulted from the uniform particulate distribution. The residual stress and the fine crystal increase the driving force and the diffusion path of precipitate result in the increasing of precipitation rate and the acceleration aging behavior.

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Lee, Jia-Ying, and 李佳盈. "Mechanical Properties of Wood-Plastic Composites Under Environment Aging Effects." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/kp3yr9.

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碩士
國立清華大學
動力機械工程學系
98
Concern for the environment, both in term of limiting the use of finite resources and the need to manage waste disposal, one of the rising environment protection materials is wood plastic composites(WPC). The study investigates the feasibility of using recycle Nylon6, Poly(ethylene terephthalate) and wood flour to manufacture experimental composite specimens. The specimens were made through extrusion, pelletised and injection molding. By adding POE-g-MA as agent into PET/Nylon (60/40、50/50、40/60), and MBS as impact- resistant agent into PET/Nylon (60/40、50/50、40/60), then discuss mechanical properties of WPC under different thermal and humid aging, thermal and humid effect and accelerate weathering. After thermal and humid aging for 200 hours and then accelerate weathering for one month, the result showed that no matter add POE-g-MA or MBS in the WPC, its tensile strength, flexure strength and flexure modulus will lose the biggest amount in the 55℃/90RH%. After accelerate weathering for one month, the result showed a decreasing trend. Besides, the impact strength in the 55℃/90RH% will enhance because the moisture absorption of Nylon6 can make WPC become more tougher. When it comes to the effect in accelerate weathering, the mechanical properties will be changed, and during exposure to UV radiation and water spray, will cause the material fade. In the end, we discuss creep of the WPC on the influence of different thermal and humid effects.

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TAN, JUN-XIONG, and 譚俊雄. "Structure and properties of high filled elastomers in aging processes." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/40842819142052330476.

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Qiu, Chong. "Atmospheric Aerosols Aging Involving Organic Compounds and Impacts on Particle Properties." Thesis, 2013. http://hdl.handle.net/1969.1/149291.

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In the first part of this dissertation, we study the aging of soot, a representative type of primary aerosols, in the presence of OH-initiated oxidation products of toluene. Monodisperse soot particles are introduced into an environmental chamber where toluene is oxidized by OH radicals. The variations in soot particle properties are simultaneously monitored, including particle size, mass, organic mass faction, hygroscopicity, and optical properties. The changes in particle properties are found to be largely governed by the thickness of the organic coating that is closely related to reaction time and initial reactant concentrations. Derived from particle size and mass, the effective density increases while dynamic shape factor decreases as the organic coating grows, suggesting a compaction of the soot morphology. As the organic coating grows, the particles become more hygroscopic and have enhanced light scattering and absorption. The second part discusses the potential reactions between amines and some aerosol constituents and alteration of aerosol properties. The reactions between alkylamines and ammonium sulfate/bisulfate have been studied using a low-pressure fast flow reactor coupled to a mass spectrometer at 293 K. Alkylamines react with ammonium sulfate/bisulfate to form alkylaminium sulfates, suggesting the existence of alkylaminium salts in particle phase. We have extended our study to characterize the physicochemical properties of alkylaminium sulfates. The hygroscopicity, thermostability, and density of five representative alkylaminium sulfates have been measured by an integrated aerosol analytical system. All alkylaminium sulfate aerosols show monotonic size growth when exposed to increasing relative humidity. Mixing ammonium sulfate with alkylaminium sulfates lowers the deliquescence point corresponding to ammonium sulfate. Alkylaminium sulfates are thermally comparable to or more stable than ammonium sulfate. The densities of alkylaminium sulfate particles are lower than that of ammonium sulfate. Our results suggest that the organic compounds can effectively alter the composition and properties of atmospheric aerosols, considerably influencing the impacts of aerosols on air quality, climate forcing, and human health.

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Dissertations / Theses on the topic 'Aging properties'

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