Stress rupture behavior of a thermal barrier coated AE 437A Ni-based superalloy used for aero turbine blades

The stress rupture characteristics of bare and thermal barrier coated (TBC) superalloy AE 437A were determined in air at temperatures between 600 and 850 °C with both short and long term testing undertaken at 800 °C. Because the bond coat contributed an addition 10% cross-sectional area and was able to support load, the higher stress, shorter term rupture lives of the TBC coated alloy exceed those for the bare material. However under lower stress, longer life conditions the ability of the bond coat to support loading was reduced, and the rupture lives of both bare and TBC coated alloy were similar

Bamboo—A functionally graded composite-correlation between microstructure and mechanical strength

Bamboo is supposed to be one of the best functionally gradient composite materials available. In a piece of bamboo, not only the number of fibres (‘vascular bundles’) but also the fibre quality varies from outer to inner-most periphery. It has been observed that near the outer periphery, within 1 mm2 area, the number of fibres is approximately 8 whereas the same at the inner-most periphery is approximately 2. Again the cross-sectional shape of fibre at outer periphery is almost circular (diameter 0.14 mm) and compacted but at the inner-most periphery, a fibre (diameter of major axis 0.93 × diameter of minor axis 0.78 mm) has been sprayed, and contain matrix in it. This structural behaviour causes the variation of tensile strength, e.g., the strength of a fibre at the outer periphery is about 160 kg/mm2 and the same at the inner-most periphery is only 45 kg/mm2. It has also been observed that the matrix of bamboo can preferentially be removed from the fibre by alkali treatment. 10% NaOH can remove adhered matrix with little effect on fibres while 20% or stronger alkali reduces the strength of fibre

Efficacy of thermal barrier coated superalloy used in turbines

The life of thermal barrier coating prior to spallation is dominated by micro cracking in both the thermally grown oxide and the yttria stabilized zirconia top coat. The damage generated by this microcracking is expected to be a primary life-limiting factor. High temperature force controlled fatigue testing of thermal barrier coated (TBC), bond coated only and bare Superni C263 superalloy, employed for manufacturing the combustion chamber of aero turbines, were conducted in air. Additionally, several accelerated creep tests on the TBC coated and on the bare Supemi C263 alloy were carried out in air

Turbine blade failure in a thermal power plant

The failure of a LP (low pressure) turbine blade of a 220 MW thermal power plant is presented. The blade was made of martensitic stainless steel and the structure was tempered martensite. There was no evidence of degradation of blade material. The fracture took place at the aerofoil region, 113-mm from the root. Throughout the blade surface Si rich phases were detected. Several pits/grooves were found on the edges of the blades and chloride was detected in these pits. These were responsible for the crevice type corrosion. The probable carriers of Cl− were Ca and K, which were found on the blade. The failure mode was intergranular type. Possibly the ultimate failure was due to corrosion-fatigue

Physico-chemical investigations on the sintering behaviour of red mud - flue dust composites

Two industrial waste products namely red mud and flue dust have been utilised to form composites and their sintering behaviour was investigated in this study. It has been observed that red mud alone can be sintered around 1250°C. Addition of flue dust can reduce the sintering temperature and bring it in the range of 1150 - 1200°C depending on the extent of flue dust addition (10-30%). The sintering kinetics initially follows the Johnson - Mehl model of nucleation and grain growth and subsequently beyond fractional conversion of 0.7. follows the three dimensional contracting geometry model. XRD studies reveal that there are at least 6-8 phases in the sintered product. Some of these are Fe,O, Ca,Fe,Si,Ofz, SiO,. NaAlSiO4, FeT(O,, 710, and Na,Si,O, EPMA studies show that apart from the above phases, smaller amounts of ZrSiO, and a few other rare earth compounds were also present in the sintered product. The silicate phases are essentially present in the grain boundaries of other non-silicate phases and these phases are responsible for reduction in the sintering temperature. These glassy phases are also responsible for inter-particle bonding in the composites. This conclusion has also been verified through scanning electron microscopy (SEM). The sintering temperature and fraction of the flue dust in the composites have been optimised at 1200°C and 20% respectively

MADS-box gene family in rice: genome-wide identification, organization and expression profiling during reproductive development and stress

<p>Abstract</p> <p>Background</p> <p>MADS-box transcription factors, besides being involved in floral organ specification, have also been implicated in several aspects of plant growth and development. In recent years, there have been reports on genomic localization, protein motif structure, phylogenetic relationships, gene structure and expression of the entire MADS-box family in the model plant system, <it>Arabidopsis</it>. Though there have been some studies in rice as well, an analysis of the complete MADS-box family along with a comprehensive expression profiling was still awaited after the completion of rice genome sequencing. Furthermore, owing to the role of MADS-box family in flower development, an analysis involving structure, expression and functional aspects of MADS-box genes in rice and <it>Arabidopsis </it>was required to understand the role of this gene family in reproductive development.</p> <p>Results</p> <p>A genome-wide molecular characterization and microarray-based expression profiling of the genes encoding MADS-box transcription factor family in rice is presented. Using a thorough annotation exercise, 75 MADS-box genes have been identified in rice and categorized into MIKC^c, MIKC*, Mα, Mβ and Mγ groups based on phylogeny. Chromosomal localization of these genes reveals that 16 MADS-box genes, mostly MIKC^c-type, are located within the duplicated segments of the rice genome, whereas most of the M-type genes, 20 in all, seem to have resulted from tandem duplications. Nine members belonging to the Mβ group, which was considered absent in monocots, have also been identified. The expression profiles of all the MADS-box genes have been analyzed under 11 temporal stages of panicle and seed development, three abiotic stress conditions, along with three stages of vegetative development. Transcripts for 31 genes accumulate preferentially in the reproductive phase, of which, 12 genes are specifically expressed in seeds, and six genes show expression specific to panicle development. Differential expression of seven genes under stress conditions is also evident. An attempt has been made to gain insight into plausible functions of rice MADS-box genes by collating the expression data of functionally validated genes in rice and <it>Arabidopsis</it>.</p> <p>Conclusion</p> <p>Only a limited number of MADS genes have been functionally validated in rice. A comprehensive annotation and transcriptome profiling undertaken in this investigation adds to our understanding of the involvement of MADS-box family genes during reproductive development and stress in rice and also provides the basis for selection of candidate genes for functional validation studies.</p

Uncertainty in Damage Assessment and Remaining Life Prediction of Engineering Materials Used In Petrochemical Industry

In this paper creep damage assessment of about 11 years’ service exposed HP-40 grade of steel used in hydrogen reformer of a petrochemical industry has been carried out in terms of a discontinuous Markov process. Experimentally determined conventional creep data under identical testing condition were used in the present investigation. Scatter and damage accumulation due to creep deformation were evaluated through microstructural assessment using light optical microscope and scanning electron microscope. Quantification of creep damage was made from replicated creep data in terms of two damage parameters A and A*. Statistical analysis of void area fraction has been carried out extensively for the both top and bottom portions of the reformer tube at 870 o C in the stress range of 52-68 MPa. In addition, the proposed probabilistic model has been compared with the Kachanav’s Continuum Damage Mechanics (CDM) model. Both the approaches displayed quantitative experimental support. A residual life of > 10 years is estimated at 870 degree C / operating stress. For 55 years’ service exposed Catalytic Cold Cracking (CCU) reactor vessel and Feed Processing Unit (FPU) distillation column materials of a petrochemical industry remnant life assessment studies were estimated by incorporating the uncertainty involved in calculation of LMP (Larson Miller Parameter) values and from extrapolation of stress vs. LMP plot. Variability of normalized creep damage for reactor and column materials is well approximated with the aid of Weibull distribution. As expected, it is observed that the distributions shift towards the higher range of damage with increase in service exposure time

Kahler Independence of the G2-MSSM

The G2-MSSM is a model of particle physics coupled to moduli fields with interesting phenomenology both for colliders and astrophysical experiments. In this paper we consider a more general model - whose moduli Kahler potential is a completely arbitrary G2-holonomy Kahler potential and whose matter Kahler potential is also more general. We prove that the vacuum structure and spectrum of BSM particles is largely unchanged in this much more general class of theories. In particular, gaugino masses are still supressed relative to the gravitino mass and moduli masses. We also consider the effects of higher order corrections to the matter Kahler potential and find a connection between the nature of the LSP and flavor effects.Comment: Final version, matches the version published in JHE

Genetic Variants Associated with Arsenic Susceptibility: Study of Purine Nucleoside Phosphorylase, Arsenic (+3) Methyltransferase, and Glutathione S-Transferase Omega Genes

BACKGROUND: Individual variability in arsenic metabolism may underlie individual susceptibility toward arsenic-induced skin lesions and skin cancer. Metabolism of arsenic proceeds through sequential reduction and oxidative methylation being mediated by the following genes: purine nucleoside phosphorylase (PNP), arsenic (+3) methyltransferase (As3MT), glutathione S-transferase omega 1 (GSTO1), and omega 2 (GSTO2). PNP functions as arsenate reductase; As3MT methylates inorganic arsenic and its metabolites; and both GSTO1 and GSTO2 reduce the metabolites. Alteration in functions of these gene products may lead to arsenic-specific disease manifestations. OBJECTIVES: To find any probable association between arsenicism and the exonic single nucleotide polymorphisms (SNPs) of the above-mentioned arsenic-metabolizing genes, we screened all the exons in those genes in an arsenic-exposed population. METHODS: Using polymerase chain reaction restriction fragment length polymorphism analysis, we screened the exons in 25 cases (individuals with arsenic-induced skin lesions) and 25 controls (individuals without arsenic-induced skin lesions), both groups drinking similar arsenic-contaminated water. The exonic SNPs identified were further genotyped in a total of 428 genetically unrelated individuals (229 cases and 199 controls) for association study. RESULTS: Among four candidate genes, PNP, As3MT, GSTO1, and GSTO2, we found that distribution of three exonic polymorphisms, His20His, Gly51Ser, and Pro57Pro of PNP, was associated with arsenicism. Genotypes having the minor alleles were significantly overrepresented in the case group: odds ratio (OR) = 1.69 [95% confidence interval (CI), 1.08–2.66] for His20His; OR = 1.66 [95% CI, 1.04–2.64] for Gly51Ser; and OR = 1.67 [95% CI, 1.05–2.66] for Pro57Pro. CONCLUSIONS: The results indicate that the three PNP variants render individuals susceptible toward developing arsenic-induced skin lesions. KEY WORDS: arsenic, As3MT, GSTO1, GSTO2, PNP, skin lesion, susceptibility. Environ Health Perspect 116:501–505 (2008). doi:10.1289/ehp.10581 available via http://dx.doi.org/ [Online 14 January 2008