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Acoustic emissions from reinforced concrete (1994)

Maji, A. K. ; Sahu, R.

Springer

Experimental mechanics 34 (1994), S. 379-388

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ISSN: 1741-2765

Keywords: Acoustic Emission ; Reinforced Concrete ; Fracture ; Source Location ; Nondestructive Evaluation (NDE)

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Acoustic emissions from reinforced-concrete beams, reinforcing bars and plain concrete cylinders were monitored. Acoustic-emission events were used in a study of source locations, frequency characteristics, and other analytical methods that have found use in the past for evaluating acoustic-emission data in other fields of engineering. Tests were done on reinforced-concrete beams under flexural loading, individual reinforcing bars under pure tension, concrete cylinders under compression, and reinforcing bars subject to pullout tests. The experimental data were first analyzed with conventional acoustic-emission methodology. A critical look at many acoustic-emission techniques currently used in other materials (metals, composites, etc.) demonstrated some of the difficulties of applying the same techniques to reinforced concrete. More importantly, it illustrated the limitations of signal processing and parameter estimation of acoustic-emission events as viable nondestructive-evaluation (NDE) techniques for reinforced-concrete structures. Subsequently, on the basis of the experimental results, some of the more promising aspects of developing acoustic emission into a structural monitoring tool are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02325153

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Studies in nickel(IV) chemistry. Electron transfer kinetics of the reaction between tris(dimethylglyoximato)nickelate(IV) and hexacyanoferrate(II) in aqueous medium (1983)

Sahu, R. ; Neogi, G. ; Acharya, S. ; [et al.]

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 15 (1983), S. 823-833

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ISSN: 0538-8066

Keywords: Chemistry ; Physical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The kinetics of electron transfer from hexacyanoferrate(II) to tris(dimethylglyoximato)-nickelate(IV), Ni(dmg)32-, to produce Fe(CN)63- and Ni(dmgH)2, follows a pseudo-first-order disappearance in the Ni(IV). The pseudo-first-order rate constants kobs are linearly dependent on [Fe(CN)64-]0 in a fiftyfold range of 2 × 10-4-1 × 10-2M, and the average values of kobs/[Fe(CN)64-]0 range from 194M-1·s-1 at pH = 5.20 to 0.2M-1·s-1 at pH = 9.07 in aqueous medium at 35°C and μ = 0.57M. Results are interpreted in terms of a probable mechanism involving rate-determining outer sphere one-electron transfer steps from the reductant and one-protonated reductant species to the unprotonated and one-protonated Ni(IV) species present in solution. The more electrophilic one-protonated reductant species apparently reacts several orders of magnitude faster than the unprotonated one.

Additional Material: 1 Ill.