Thermal barrier coating life prediction model development

The objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep

Effects of MAR-M247 substrate (modified) composition on coating oxidation coating/substrate interdiffusion

The effects of gamma+gamma' Mar-M247 substrate composition on gamma+beta Ni-Cr-Al-Zr coating oxidation and coating/substrate interdiffusion were evaluated. These results were also compared to a prior study for a Ni-Cr-Al-Zr coated gamma Ni-Cr-Al substrate with equivalent Al and Cr atomic percentages. Cyclic oxidation behavior at 1130 C was investigated using change in weight curves. Concentration/distance profiles were measured for Al, Cr, Co, W, and Ta. The surface oxides were examined by X-ray diffraction and scanning electron microscopy. The results indicate that variations of Ta and C concentrations in the substrate do not affect oxidation resistance, while additions of grain boundary strengthening elements (Zr, Hf, B) increase oxidation resistance. In addition, the results indicate that oxidation phenomena in gamma+beta/gamma+gamma' Mar-M247 systems have similar characteristics to the l gamma+beta/gamma Ni-Cr-Al system

Thermal barrier coating life prediction model development

This report describes work performed to determine the predominat modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consisted of a low pressure plasma sprayed NiCrAlY bond coat, an air plasma sprayed ZrO2-Y2O3 top coat, and a Rene' 80 substrate. The work was divided into 3 technical tasks. The primary failure mode to be addressed was loss of the zirconia layer through spalling. Experiments showed that oxidation of the bond coat is a significant contributor to coating failure. It was evident from the test results that the species of oxide scale initially formed on the bond coat plays a role in coating degradation and failure. It was also shown that elevated temperature creep of the bond coat plays a role in coating failure. An empirical model was developed for predicting the test life of specimens with selected coating, specimen, and test condition variations. In the second task, a coating life prediction model was developed based on the data from Task 1 experiments, results from thermomechanical experiments performed as part of Task 2, and finite element analyses of the TBC system during thermal cycles. The third and final task attempted to verify the validity of the model developed in Task 2. This was done by using the model to predict the test lives of several coating variations and specimen geometries, then comparing these predicted lives to experimentally determined test lives. It was found that the model correctly predicts trends, but that additional refinement is needed to accurately predict coating life

Thermal barrier coating life prediction model

This is the first report of the first phase of a 3-year program. Its objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, then to develop and verify life prediction models accounting for these degradation modes. The first task (Task I) is to determine the major failure mechanisms. Presently, bond coat oxidation and bond coat creep are being evaluated as potential TBC failure mechanisms. The baseline TBC system consists of an air plasma sprayed ZrO2-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene'80 substrate. Pre-exposures in air and argon combined with thermal cycle tests in air and argon are being utilized to evaluate bond coat oxidation as a failure mechanism. Unexpectedly, the specimens pre-exposed in argon failed before the specimens pre-exposed in air in subsequent thermal cycles testing in air. Four bond coats with different creep strengths are being utilized to evaluate the effect of bond coat creep on TBC degradation. These bond coats received an aluminide overcoat prior to application of the top coat to reduce the differences in bond coat oxidation behavior. Thermal cycle testing has been initiated. Methods have been selected for measuring tensile strength, Poisson's ratio, dynamic modulus and coefficient of thermal expansion both of the bond coat and top coat layers

Effect of bond coat creep and oxidation on TBC integrity

The potential of thermal barrier coatings (TBCs) on high-pressure turbine (HPT) nozzles and blades is limited at present by the inability to quantitatively predict TBC life for these components. The goal is to isolate the major TBC failure mechanisms, which is part of the larger program aimed at developing TBC life prediction models. Based on the results of experiments to isolate TBC failure mechanisms, the effects of bond coat oxidation and bond coat creep on TBC integrity is discussed. In bond coat oxidation experiments, Rene prime 80 specimens coated with a NiCrAlY/ZrO2-8 percent Y2O3 TBC received isothermal pre-exposures at 2000 F in static argon, static air, or received no pre-exposure. The effects of oxidation due to the pre-exposures were determined by thermal cycle tests in both static air and static argon at 2000 F. To study the effect of bond coat creep on TBS behavior, four bond coats with different creep properties were evaluated by thermal cycle tests in air at 2000 F. The test results, the relative importance of these two failure mechanisms, and how their effects may be quantified will also be discussed

Thermal barrier coating life prediction model

The objectives of this program are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. The program is divided into two phases, each consisting of several tasks. The work in Phase 1 is aimed at identifying the relative importance of the various failure modes, and developing and verifying life prediction model(s) for the predominant model for a thermal barrier coating system. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep. The work in Phase 2 will develop design-capable, causal, life prediction models for thermomechanical and thermochemical failure modes, and for the exceptional conditions of foreign object damage and erosion

Problem Solving and Maternal Distress at the Time of Child's Cancer Diagnosis: English Versus Spanish-Speaking Mothers

In the United States, cancer is the leading cause of death by disease among children; approximately 9500 new cases of were diagnosed in 2006 among children under 19 years of age. Among these children it was estimated that 1850 of these cases were Hispanic children. Survival rates have sharply risen over the past 25 years and now more than 75% of children diagnosed with cancer in the US are alive 5 years after diagnosis. This increase in childhood survival rates have exposed a need for increased understanding of parental functioning following their child's cancer diagnosis. While a majority of parents report increased distress following a traumatic event such as a child's cancer diagnosis, the aim of this study was to investigate distress and problem-solving skills between English (N=253) and monolingual Spanish-speaking (N=44) mothers. Data for this study was extracted from a pre-existing data set from a large intervention study on maternal problem-solving skills training and participants were mothers who were recruited within 2 to 16 weeks following their child's cancer diagnosis. Compared with English-speaking mothers, monolingual Spanish-speaking mothers reported greater distress and poorer problem-solving skills at baseline, but only one distress measure (IES-R) was significant after controlling for maternal education. The findings from this exploratory analysis are significant to public health because it is important to assess psychosocial adjustment following traumatic events, such as a child's cancer diagnosis, among the fastest growing minority population in the United States. It is also important to determine the contribution of socio-cultural characteristics to parental adjustment for minority populations. A better understanding of these socio-cultural differences in family adjustment to traumatic events has the potential to create interventions to improve the quality of life for families

The European Union as a Green Normative Power? The Case of the EU’s Sustainable Energy Cooperation with China

Given energy’s powerful role in achieving sustainable development (SD), the relevance of turning to sustainable energy (SE) – understood as renewable energy and energy efficiency – has been recognised as an essential instrument in the global SD agenda. In its Treaties, the European Union (EU) made a profound commitment to the SD principle, and to environmental sustainability, by enshrining it as an objective of the Union and vowing to promote it both domestically and abroad. With Manners’ introduction in 2002 of the ‘Normative Power Europe’ (NPE) conceptualisation of the EU, this commitment can be linked to the EU’s very identity (Manners 2002). The EU is to be a norm promoter in the world to which it can be held accountable. The objective of this thesis is to determine if the EU can legitimately be called a green normative power to the extent that it abides by its commitment to promote SD in the world. In order to test this proposition this research applies Manners’ NPE approach to the case study of the EU’s SE cooperation with China. With its fast paced rise as an economic powerhouse and main fossil fuel consumer, China currently poses one of the single greatest challenges to the achievement of effective SD for the planet. China is also one of the main countries with which the EU developed its SE cooperation. This work presents three main contributions. First, the thesis' main originality derives from the use of Manners’ tripartite analytical framework (Manners 2009b) in the context of EU-China relations in SE. This provides for a comprehensive assessment of the EU’s normative status, not only addressing the EU’s commitment to SD but also to promoting it in a normative way (Manners 2002) by looking at the whole policy process. In doing so, this research seeks firstly to enrich the currently very limited NPE literature on the EU’s status as green normative power by extending it to the field of SE. Secondly, the thesis also aims to add an originally researched case study on China to the NPE field of study. Finally, the thesis also contributes to expanding the application of Manners’ analytical framework by operationalizing it to the study of the SD norm as a concept

Thermal barrier coating life prediction model

This is the second annual report of the first 3-year phase of a 2-phase, 5-year program. The objectives of the first phase are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consists of an air plasma sprayed ZrO-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene' 80 substrate. Task I was to evaluate TBC failure mechanisms. Both bond coat oxidation and bond coat creep have been identified as contributors to TBC failure. Key property determinations have also been made for the bond coat and the top coat, including tensile strength, Poisson's ratio, dynamic modulus, and coefficient of thermal expansion. Task II is to develop TBC life prediction models for the predominant failure modes. These models will be developed based on the results of thermmechanical experiments and finite element analysis. The thermomechanical experiments have been defined and testing initiated. Finite element models have also been developed to handle TBCs and are being utilized to evaluate different TBC failure regimes

Aging Induces Profound Changes in sncRNA in Rat Sperm and These Changes Are Modified by Perinatal Exposure to Environmental Flame Retardant

Advanced paternal age at fertilization is a risk factor for multiple disorders in offspring and may be linked to age-related epigenetic changes in the father’s sperm. An understanding of aging-related epigenetic changes in sperm and environmental factors that modify such changes is needed. Here, we characterize changes in sperm small non-coding RNA (sncRNA) between young pubertal and mature rats. We also analyze the modification of these changes by exposure to environmental xenobiotic 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47). sncRNA libraries prepared from epididymal spermatozoa were sequenced and analyzed using DESeq 2. The distribution of small RNA fractions changed with age, with fractions mapping to rRNA and lncRNA decreasing and fractions mapping to tRNA and miRNA increasing. In total, 249 miRNA, 908 piRNA and 227 tRNA-derived RNA were differentially expressed (twofold change, false discovery rate (FDR) p ≤ 0.05) between age groups in control animals. Differentially expressed miRNA and piRNA were enriched for protein-coding targets involved in development and metabolism, while piRNA were enriched for long terminal repeat (LTR) targets. BDE-47 accelerated age-dependent changes in sncRNA in younger animals, decelerated these changes in older animals and increased the variance in expression of all sncRNA. Our results indicate that the natural aging process has profound effects on sperm sncRNA profiles and this effect may be modified by environmental exposure