Finite element elastic-plastic-creep and cyclic life analysis of a cowl lip

Results are presented of elastic, elastic-plastic, and elastic-plastic-creep analyses of a test-rig component of an actively cooled cowl lip. A cowl lip is part of the leading edge of an engine inlet of proposed hypersonic aircraft and is subject to severe thermal loadings and gradients during flight. Values of stresses calculated by elastic analysis are well above the yield strength of the cowl lip material. Such values are highly unrealistic, and thus elastic stress analyses are inappropriate. The inelastic (elastic-plastic and elastic-plastic-creep) analyses produce more reasonable and acceptable stress and strain distributions in the component. Finally, using the results from these analyses, predictions are made for the cyclic crack initiation life of a cowl lip. A comparison of predicted cyclic lives shows the cyclic life prediction from the elastic-plastic-creep analysis to be the lowest and, hence, most realistic

Structural response of SSME turbine blade airfoils

Reusable space propulsion hot gas-path components are required to operate under severe thermal and mechanical loading conditions. These operating conditions produce elevated temperature and thermal transients which results in significant thermally induced inelastic strains, particularly, in the turbopump turbine blades. An inelastic analysis for this component may therefore be necessary. Anisotropic alloys such as MAR M-247 or PWA-1480 are being considered to meet the safety and durability requirements of this component. An anisotropic inelastic structural analysis for an SSME fuel turbopump turbine blade was performed. The thermal loads used resulted from a transient heat transfer analysis of a turbine blade. A comparison of preliminary results from the elastic and inelastic analyses is presented

Thermal Fatigue Limitations of Continuous Fiber Metal Matrix Composites

The potential structural benefits of unidirectional, continuous-fiber, metal matrix composites (MMC's) are legendary. When compared to their monolithic matrices, MMC's possess superior properties such as higher stiffness and tensile strength, and lower coefficient of thermal expansion in the direction of the reinforcing fibers. As an added bonus, the MMC density will be lower if the fibers are less dense than the matrix matErial they replace. The potential has been demonstrated unequivocally both analytically and experimentally, especially at ambient temperatures. Successes prompted heavily-funded National efforts within the United States (USAF and NASA) and elsewhere to extend the promise of MMC's into the temperature regime wherein creep, stress relaxation, oxidation, and thermal fatigue damage mechanisms lurk. This is the very regime for which alternative high-temperature materials are becoming mandatory, since further enhancement of state- of-the-art monolithic alloys is rapidly approaching a point of diminishing returns

Life assessment of structural components using inelastic finite element analyses

The need for enhanced and improved performance of structural components subject to severe cyclic thermal/mechanical loadings, such as in the aerospace industry, requires development of appropriate solution technologies involving time-dependent inelastic analyses. Such analyses are mandatory to predict local stress-strain response and to assess more accurately the cyclic life time of structural components. The NASA-Lewis Research Center is cognizant of this need. As a result of concerted efforts at Lewis during the last few years, several such finite element solution technologies (in conjunction with the finite element program MARC) were developed and successfully applied to numerous uniaxial and multiaxial problems. These solution technologies, although developed for use with MARC program, are general in nature and can easily be extended for adaptation with other finite element programs such as ABAQUS, ANSYS, etc. The description and results obtained from two such inelastic finite element solution technologies are presented. The first employs a classical (non-unified) creep-plasticity model. An application of this technology is presented for a hypersonic inlet cowl-lip problem. The second of these technologies uses a unified creep-plasticity model put forth by Freed. The structural component for which this finite element solution technology is illustrated, is a cylindrical rocket engine thrust chamber. The advantages of employing a viscoplastic model for nonlinear time-dependent structural analyses are demonstrated. The life analyses for cowl-lip and cylindrical thrust chambers are presented. These analyses are conducted by using the stress-strain response of these components obtained from the corresponding finite element analyses

Role of MRI and ultrasonography in evaluation of multifidus muscle in chronic low back pain patients

Background: Low back pain (LBP) is a condition that will affect 60-80% of the population at some stage in their life. Epidemiological studies have shown that simple backache has point prevalence and a 1-month prevalence of 15-30% and 30-40% respectively. Studies that have been performed state that LBP is a self-limiting condition, but many people who have suffered from LBP will experience recurring episodes, which could lead to the development of chronic LBP. The objective of the study was to assess the role of MRI and USG in evaluating degenerative changes in multifidus muscle in chronic low back pain patients.Methods: A Cross-sectional Observational study was done in 30 patients. Adult patients of either sex who presented with low back pain for 6 weeks or more and Grade 1 and grade 2 degenerative intervertebral disc changes as seen on plain skiagrams of L-S spine, A-P and lateral views were subjected to MRI and Ultrasound.Results: Multifidus and paraspinal muscle atrophy and fatty degeneration should be considered in association with the clinical presentation and other abnormalities seen in MRI examination.Conclusions: Whether LBP duration, severity and associated functional disability affect the degree of paraspinal muscle degenerative changes remains unclear. Possible reasons underlying the discrepant findings include variations among the age and symptoms of duration of the studied populations and small sample size

Alcoholic Extract of Eclipta alba

As per WHO estimates, 80% of people around the world use medicinal plants for the cure and prevention of various diseases including cancer owing to their easy availability and cost effectiveness. Eclipta alba has long been used in Ayurveda to treat liver diseases, eye ailments, and hair related disorders. The promising medicinal value of E. alba prompted us to study the antioxidant, nontoxic, and anticancer potential of its alcoholic extract. In the current study, we evaluated the in vitro cytotoxic and antioxidant effect of the alcoholic extract of Eclipta alba (AEEA) in multiple cancer cell lines along with control. We have also evaluated its effect on different in vivo toxicity parameters. Here, we found that AEEA was found to be most active in most of the cancer cell lines but it significantly induced apoptosis in human breast cancer cell lines by disrupting mitochondrial membrane potential and DNA damage. Moreover, AEEA treatment inhibited migration in both MCF 7 and MDA-MB-231 cells in a dose dependent manner. Further, AEEA possesses robust in vitro antioxidant activity along with high total phenolic and flavonoid contents. In summary, our results indicate that Eclipta alba has enormous potential in complementary and alternative medicine for the treatment of cancer

Prevalence of gestational diabetes mellitus in intrahepatic cholestasis of pregnancy

Background: Incidence of IHCP in Indian population is 0.02%-2.4% and that of GDM is 3.8%-17.9%. Frequent co-existence of both has raised the question of any association. There exists only few studies to prove or disprove any association. Objective of current study was to determine the prevalence of GDM in women with IHCP and to compare the feto-maternal outcome in women with GDM with or without IHCP. Methods: The study was conducted in the Department of Obstetrics and Gynaecology, VMMC and SJH, New Delhi. Women with singleton pregnancy ≥28wks were recruited for the study and further categorized as women with IHCP and women without IHCP according to their diagnosis of IHCP by the RCOG guidelines. OGTT with 75g glucose was done to make the diagnosis of GDM. Management was as per obstetrics protocol and feto-maternal outcomes recorded till delivery. Results: No statistically significant difference in the prevalence of GDM observed in both groups (5.4% in women with IHCP and 8.2% in women without IHCP, p=0.220). Significantly higher number of preterm deliveries (21%, p<0.001), induced labour (53.6%, p<0.001), women undergoing LSCS (46.3%, p<0.001) in women with IHCP. No association of FGR, MSL, Fetal maturity, labour onset, mode of delivery, stillbirth, low APGAR score, NICU admission, or PPH in women with GDM with or without IHCP. Conclusions: The prevalence of GDM is not higher in women with IHCP but significantly higher incidence of preterm delivery, induced labour, and Caesarean sections in women with IHCP. No significant difference in feto-maternal outcome in women with GDM with or without IHCP