The Experts below are selected from a list of 16923 Experts worldwide ranked by ideXlab platform
Suresh Bhalla - One of the best experts on this subject based on the ideXlab platform.
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monitoring early hydration of reinforced concrete structures using structural parameters identified by piezo sensors via electromechanical impedance technique
Mechanical Systems and Signal Processing, 2018Co-Authors: V Talakokula, Suresh Bhalla, Ashok GuptaAbstract:Abstract Concrete is the most widely used material in civil engineering construction. Its life begins when the hydration process is activated after mixing the cement granulates with water. In this paper, a non-dimensional hydration parameter, obtained from piezoelectric ceramic (PZT) patches bonded to rebars embedded inside concrete, is employed to monitor the early age hydration of concrete. The non-dimensional hydration parameter is derived from the Equivalent Stiffness determined from the piezo-impedance transducers using the electro-mechanical impedance (EMI) technique. The focus of the study is to monitor the hydration process of cementitious materials commencing from the early hours and continue till 28 days using single non-dimensional parameter. The experimental results show that the proposed piezo-based non-dimensional hydration parameter is very effective in monitoring the early age hydration, as it has been derived from the refined structural impedance parameters, obtained by eliminating the PZT contribution, and using both the real and imaginary components of the admittance signature.
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diagnosis of carbonation induced corrosion initiation and progression in reinforced concrete structures using piezo impedance transducers
Sensors and Actuators A-physical, 2016Co-Authors: V Talakokula, Bishwajit Bhattacharjee, Suresh Bhalla, Richard J Ball, C R Bowen, Giovanni Pesce, Rajnish Kurchania, Ashok Gupta, Kevin PaineAbstract:In addition to chloride induced corrosion, the other commonly occurring type of rebar corrosion in reinforced concrete structures is that induced by the ingress of atmospheric carbon dioxide into concrete, commonly referred to as ‘carbonation induced corrosion’. This paper presents a new approach for detecting the onset and quantifying the level of carbonation induced rebar corrosion. The approach is based on the changes in the mechanical impedance parameters acquired using the electro-mechanical coupling of a piezoelectric lead zirconate titanate (PZT) ceramic patch bonded to the surface of the rebar. The approach is non-destructive and is demonstrated though accelerated tests on reinforced concrete specimens subjected to controlled carbon dioxide exposure for a period spanning over 230 days. The Equivalent Stiffness parameter, extracted from the frequency response of the admittance signatures of the PZT patch, is found to increase with penetration of carbon dioxide inside the surface and the consequent carbonation, an observation that is correlated with phenolphthalein staining. After the onset of rebar corrosion, the Equivalent Stiffness parameter exhibited a reduction in magnitude over time, providing a clear indication of the occurrence of corrosion and the results are correlated with scanning electron microscope images and Raman spectroscopy measurements. The average rate of corrosion is determined using the Equivalent mass parameter. The use of PZT ceramic transducers, therefore, provides an alternate and effective technique for diagnosis of carbonation induced rebar corrosion initiation and progression in reinforced concrete structures non-destructively.
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piezo impedance transducers for residual fatigue life assessment of bolted steel joints
Structural Health Monitoring-an International Journal, 2012Co-Authors: Suresh Bhalla, Panduranga A Vittal, Milan VeljkovicAbstract:This article presents a new approach for fatigue life assessment of bolted steel joints using the Equivalent Stiffness determined by surface-bonded piezo-impedance transducers. The piezo transducer ...
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calibration of piezo impedance transducers for strength prediction and damage assessment of concrete
Smart Materials and Structures, 2005Co-Authors: Chee Kiong Soh, Suresh BhallaAbstract:This paper presents a new approach for the non-destructive evaluation of concrete, covering both strength prediction and damage assessment, using the electro-mechanical impedance technique. A new empirical method is proposed to determine in situ concrete strength non-destructively using admittance signatures of surface-bonded piezo-impedance transducers. This is followed by the 'identification' of appropriate impedance parameters for concrete. The identified parameters are found to be sensitive to structural damages as well as to concrete strength gain during curing. Comprehensive tests were conducted on concrete specimens up to failure to empirically calibrate the 'identified' system parameters with damage severity. An empirical fuzzy probabilistic damage model is proposed to quantitatively predict damage severity in concrete based on variation in the identified Equivalent Stiffness.
J A E Manson - One of the best experts on this subject based on the ideXlab platform.
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carbon fibre reinforced composite waste an environmental assessment of recycling energy recovery and landfilling
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: Robert A Witik, R Teuscher, Veronique Michaud, Christian Ludwig, J A E MansonAbstract:The environmental benefits of recycling are assessed against other end-of-life (EOL) treatments for Carbon Fibre Reinforced Plastic (CFRP) waste. Recycling via pyrolysis, incineration with energy recovery, and disposal via landfilling are compared. To account for physical changes to materials from use and recycling, equivalence between recycled and virgin materials is calculated based on the ability to produce a short fibre composite beam of Equivalent Stiffness. Secondary effects of using Recycled Carbon Fibre (RCF) in a hypothetical automotive application are also analysed. Results underline the ecological constraints towards recycling CFRPs and demonstrate that benefits from recycling are strongly linked to the impacts of the selected recovery process, the materials replaced by RCF in a secondary application, and also to the type of secondary application in which they are used.
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carbon fibre reinforced composite waste an environmental assessment of recycling energy recovery and landfilling
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: Robert A Witik, R Teuscher, Veronique Michaud, Christian Ludwig, J A E MansonAbstract:The environmental benefits of recycling are assessed against other end-of-life (EOL) treatments for Carbon Fibre Reinforced Plastic (CFRP) waste. Recycling via pyrolysis, incineration with energy recovery, and disposal via landfilling are compared. To account for physical changes to materials from use and recycling, equivalence between recycled and virgin materials is calculated based on the ability to produce a short fibre composite beam of Equivalent Stiffness. Secondary effects of using Recycled Carbon Fibre (RCF) in a hypothetical automotive application are also analysed. Results underline the ecological constraints towards recycling CFRPs and demonstrate that benefits from recycling are strongly linked to the impacts of the selected recovery process, the materials replaced by RCF in a secondary application, and also to the type of secondary application in which they are used. (C) 2013 Elsevier Ltd. All rights reserved.
Marc Thomas - One of the best experts on this subject based on the ideXlab platform.
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an electrorheological hydrostatic journal bearing for controlling rotor vibration
Computers & Structures, 2008Co-Authors: Ahmed Bouzidane, Marc ThomasAbstract:The objective of this work is to study the dynamic behavior of a rotor supported by a new hydrostatic journal bearing, and fed with a negative electrorheological (NER) fluid. The hydrostatic bearing consists of four hydrostatic bearing flat pads fed by capillary restrictors. An ER fluid consists of a suspension of micron-sized particles dispersed in a dielectric liquid. A negative electrorheological (NER) fluid is a Newtonian fluid with a viscosity which decreases when an electric field is applied, and which can restore its property when the field is removed. A reversible change in viscosity occurs in milliseconds with the electric field applied. Therefore, these fluids are suitable for the real-time control of vibration and vibration damping. A linear modeling was performed using numerical methods in order to investigate the effect of negative electrorheological fluids, recess pressure and static eccentricity ratio on carrying load capacity, flow, and the Equivalent dynamic characteristics (Stiffness, damping, damping factor) of a new NER hydrostatic journal bearing. In a first step, the flow, Equivalent Stiffness and damping and damping factor is studied according to the pressure ratio, for different electric field values at the point of operation. In a second step, the variation of carrying load capacity and Equivalent Stiffness and damping is studied according to the static eccentric ratio, for different electric field values. In a third step, an application study of an NER hydrostatic journal bearing based on linear theory is presented in order to reduce or suppresses the imbalance-induced vibration or the force transmitted to the base. The discussion of results includes some thoughts on future trends.
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Equivalent Stiffness and damping investigation of a hydrostatic journal bearing
Tribology Transactions, 2007Co-Authors: Ahmed Bouzidane, Marc ThomasAbstract:The aim of this research is to study the dynamic characteristics of a hydrostatic journal bearing, with four hydrostatic bearing flat pads fed by diaphragm restrictors and supporting a rotor. We assumed that the fluid flow is incompressible, laminar, isothermal, and steady-state. Linear modeling was performed using a numerical method in order to investigate the effects of the film thickness, the recess pressure, and the geometric configuration on the Equivalent Stiffness and damping of a hydrostatic journal bearing. In the first step, the variation of Equivalent Stiffness and damping is studied according to the pressure ratio for different geometric configurations of a hydrostatic bearing at the point of operation. In the second step, the variation of the Equivalent Stiffness and damping is studied according to the ratio of the film thickness for different geometric configurations of a hydrostatic bearing when one moves away from the point of operation. The results show that the hydrostatic journal bearin...
Jess G Snedeker - One of the best experts on this subject based on the ideXlab platform.
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Equivalent Stiffness after glycosaminoglycan depletion in tendon an ultra structural finite element model and corresponding experiments
Journal of Theoretical Biology, 2011Co-Authors: Gion Fessel, Jess G SnedekerAbstract:Abstract The glycosaminoglycan (GAG) side-chains of small leucine-rich proteoglycans have been postulated to mechanically cross-link adjacent collagen fibrils and contribute to tendon mechanics. Enzymatic depletion of tendon GAGs (chondroitin and dermatan sulfate) has emerged as a preferred method to experimentally assess this role. However, GAG removal is typically incomplete and the possibility remains that extant GAGs may remain mechanically functional. The current study specifically investigated the potential mechanical effect of the remaining GAGs after partial enzymatic digestion. A three-dimensional finite element model of tendon was created based upon the concept of proteoglycan mediated inter-fibril load sharing. Approximately 250 interacting, discontinuous collagen fibrils were modeled as having a length of 400 μm, being composed of rod elements of length 67 nm and E-modulus 1 GPa connected in series. Spatial distribution and diameters of these idealized fibrils were derived from a representative cross-sectional electron micrograph of tendon. Rod element lengths corresponded to the collagen fibril D-Period, widely accepted to act as a binding site for decorin and biglycan, the most abundant proteoglycans in tendon. Each element node was connected to nodes of any neighboring fibrils within a radius of 100 nm, the slack length of unstretched chondroitin sulfate. These GAG cross-links were the sole mechanism for lateral load sharing among the discontinuous fibrils, and were modeled as bilinear spring elements. Simulation of tensile testing of tendon with complete cross-linking closely reproduced corresponding experiments on rat tail tendons. Random reduction of 80% of GAG cross-links (matched to a conservative estimate of enzymatic depletion efficacy) predicted a drop of 14% in tendon modulus. Corresponding mechanical properties derived from experiments on rat tail tendons treated in buffer with and without chondroitinase ABC were apparently unaffected, regardless of GAG depletion. Further tests for equivalence, conservatively based on effect size limits predicted by the model, confirmed Equivalent Stiffness between enzymatically depleted tendons and their native controls. Although the model predicts that relatively small quantities of GAGs acting as primary collagen cross-linking elements could provide mechanical integrity to the tendon, partial enzymatic depletion of GAGs should result in mechanical changes that are not reflected in analogous experimental testing. We thus conclude that GAG side chains of small leucine-rich proteoglycans are not a primary determinant of tensile mechanical behavior in mature rat tail tendons.
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Equivalent Stiffness after glycosaminoglycan depletion in tendon an ultra structural finite element model and corresponding experiments
Journal of Theoretical Biology, 2011Co-Authors: Gion Fessel, Jess G SnedekerAbstract:The glycosaminoglycan (GAG) side-chains of small leucine-rich proteoglycans have been postulated to mechanically cross-link adjacent collagen fibrils and contribute to tendon mechanics. Enzymatic depletion of tendon GAGs (chondroitin and dermatan sulfate) has emerged as a preferred method to experimentally assess this role. However, GAG removal is typically incomplete and the possibility remains that extant GAGs may remain mechanically functional. The current study specifically investigated the potential mechanical effect of the remaining GAGs after partial enzymatic digestion. A three-dimensional finite element model of tendon was created based upon the concept of proteoglycan mediated inter-fibril load sharing. Approximately 250 interacting, discontinuous collagen fibrils were modeled as having a length of 400 μm, being composed of rod elements of length 67 nm and E-modulus 1 GPa connected in series. Spatial distribution and diameters of these idealized fibrils were derived from a representative cross-sectional electron micrograph of tendon. Rod element lengths corresponded to the collagen fibril D-Period, widely accepted to act as a binding site for decorin and biglycan, the most abundant proteoglycans in tendon. Each element node was connected to nodes of any neighboring fibrils within a radius of 100 nm, the slack length of unstretched chondroitin sulfate. These GAG cross-links were the sole mechanism for lateral load sharing among the discontinuous fibrils, and were modeled as bilinear spring elements. Simulation of tensile testing of tendon with complete cross-linking closely reproduced corresponding experiments on rat tail tendons. Random reduction of 80% of GAG cross-links (matched to a conservative estimate of enzymatic depletion efficacy) predicted a drop of 14% in tendon modulus. Corresponding mechanical properties derived from experiments on rat tail tendons treated in buffer with and without chondroitinase ABC were apparently unaffected, regardless of GAG depletion. Further tests for equivalence, conservatively based on effect size limits predicted by the model, confirmed Equivalent Stiffness between enzymatically depleted tendons and their native controls. Although the model predicts that relatively small quantities of GAGs acting as primary collagen cross-linking elements could provide mechanical integrity to the tendon, partial enzymatic depletion of GAGs should result in mechanical changes that are not reflected in analogous experimental testing. We thus conclude that GAG side chains of small leucine-rich proteoglycans are not a primary determinant of tensile mechanical behavior in mature rat tail tendons.
Robert A Witik - One of the best experts on this subject based on the ideXlab platform.
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carbon fibre reinforced composite waste an environmental assessment of recycling energy recovery and landfilling
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: Robert A Witik, R Teuscher, Veronique Michaud, Christian Ludwig, J A E MansonAbstract:The environmental benefits of recycling are assessed against other end-of-life (EOL) treatments for Carbon Fibre Reinforced Plastic (CFRP) waste. Recycling via pyrolysis, incineration with energy recovery, and disposal via landfilling are compared. To account for physical changes to materials from use and recycling, equivalence between recycled and virgin materials is calculated based on the ability to produce a short fibre composite beam of Equivalent Stiffness. Secondary effects of using Recycled Carbon Fibre (RCF) in a hypothetical automotive application are also analysed. Results underline the ecological constraints towards recycling CFRPs and demonstrate that benefits from recycling are strongly linked to the impacts of the selected recovery process, the materials replaced by RCF in a secondary application, and also to the type of secondary application in which they are used.
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carbon fibre reinforced composite waste an environmental assessment of recycling energy recovery and landfilling
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: Robert A Witik, R Teuscher, Veronique Michaud, Christian Ludwig, J A E MansonAbstract:The environmental benefits of recycling are assessed against other end-of-life (EOL) treatments for Carbon Fibre Reinforced Plastic (CFRP) waste. Recycling via pyrolysis, incineration with energy recovery, and disposal via landfilling are compared. To account for physical changes to materials from use and recycling, equivalence between recycled and virgin materials is calculated based on the ability to produce a short fibre composite beam of Equivalent Stiffness. Secondary effects of using Recycled Carbon Fibre (RCF) in a hypothetical automotive application are also analysed. Results underline the ecological constraints towards recycling CFRPs and demonstrate that benefits from recycling are strongly linked to the impacts of the selected recovery process, the materials replaced by RCF in a secondary application, and also to the type of secondary application in which they are used. (C) 2013 Elsevier Ltd. All rights reserved.