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An experimental and numerical investigation on fatigue of composite and metal aircraft structures
Siddharth Pitta,Jose I. Rojas-Mendez,Francesc Rour,Daniel Crespo,Magd Abdel Wahab 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.1
The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft’s skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening
Seetharaman,Santhikumar Pitta,Krishna Moorthy,Saravanan 한국유통과학회 2016 유통과학연구 Vol.14 No.4
Purpose– This paper attempts to determine the importance of financial sustainability and the impact of Selling, General and Administrative Expenses (SG&A) on the financial sustainability of the IT industry. Research design, data, and methodology Primarily the im – -pact of SG&A expenditure on the sales revenue, assets, gross margins and profit is ascertained. After that the impact of SG&A expenditure, sales revenue, assets, gross margins and profit on the financial sustainability i.e., return on assets is worked out. Finally the impacts of financial sustainability i.e., return on assets on total enterprise value and market valuation multiples are found out. Results The empirical result shows that SG&A expenditure – most strongly impacted sales revenue, assets, gross margins and profit positively. Financial sustainability impacted in mixed manner with SG&A expenditure, sales revenue, assets, gross margins and profit. Assets and gross margins have weak positive impact on financial sustainability. Sales revenue has no impact on financial sustainability. Finally financial sustainability had moderate positive impact on total enterprise value and had no impact on market valuation multiples. Conclusions SG&A expense has moderate positive impact – on the financial sustainability and magnitude is very low.
Chemical Profile and Cytotoxicity Activity of Stem-bark of Anacardium occidentale
Shehu, Abdullahi,Ponnapalli, Mangala Gowri,Mahboob, Mohd,Prabhakar, Pitta Venkata,Olatunji, Gabriel Ademola The Korean Society of Pharmacognosy 2022 Natural Product Sciences Vol.28 No.2
Column chromatographic fractionation of the methanol and ethyl acetate extracts of the stem-bark of Anacardium occidentale led to the isolation of five compounds (1-5). Their structures were determined by spectroscopic means by comparing spectral data to be β-sitosterol (1), 2,4-dihydroxy acetophenone (2), 1-monolinolein (3), ethyl oleate (4) and β-sitosterol-3-O-β-D-glucopyranoside (5). These compounds were evaluated for cytotoxicity against human cancer cell lines: A549, SCOV3 and rat normal cell line NRK49f. Compounds 2-5 were for the first time isolated from A. occidentale.