Low Frequency Electrical and Magnetic Methods for  Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview

Faifer, Marco; Ferrara, Liberato; Ottoboni, R.; Toscani, Sergio

doi:10.3390/s130101300

Cited by 20 publications

(11 citation statements)

References 21 publications

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“…The homogeneity of the examined volume V can be described via the scheme of the equivalent model exhibiting concentrated parameters, which include the capacitance C0, resistance R0, and inductance L0, as indicated in Fig.4. The previously used procedure [17] for evaluating the homogeneity of composite material components via an assessment of the impedance ܼ መ differs from the technique discussed herein (namely, an approach to operate within an area close to series resonance, [1]) in that the impedance ܼ መ in the complex form and within the area close to series resonance is very sensitive to changes in the distribution of the monitored composite material component in the region of the sensed magnetic field [15], [17]. The sensitivity may be two to three orders of magnitude higher than that exhibited by currently used methods and methodologies.…”

Section: A Design Of the Measuring Devicementioning

confidence: 99%

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

Bachorec

Fiala²,

Steinbauer

et al. 2018

Measurement Science Review

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Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to cracking. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite are distributed evenly. Current methods to evaluate the distribution and concentration in a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses auxiliary techniques and laboratory tests that evaluate the density and orientation of the fibers in a composite material, presenting an innovative approach to impedance-based non-destructive testing. The actual methodology utilizes the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of f = 10 kHz and 2 GHz.

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Section: A Design Of the Measuring Devicementioning

confidence: 99%

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

Bachorec

Fiala²,

Steinbauer

et al. 2018

Measurement Science Review

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“…In particular, the method proposed by Faifer et al [70] , which has been employed in this work, relies on the fact that the steel fiber reinforced concrete is a mixture of two materials with very different magnetic permeability. The presence and the arrangement of the fibers modify the path of the magnetic field lines generated by the winding of a probe which results in a variation of its inductance.…”

Section: Non-destructive Monitoring Of Fiber Dispersionmentioning

confidence: 99%

“…Besides its good sensitivity and robustness, the method also features an ease of use, due to a portable equipment, which just needs to be laid of the surface of a structural element, even sub-vertical ones, such as walls or slabs accessible only from the bottom, without any dedicated care about the coupling between the element free surface and the sensor. The authors also tested a twin coil probe with the attempt of investigating also the dissipative effects due to the alternating magnetic field which invests the steel fibers [70].…”

Section: Non-destructive Monitoring Of Fiber Dispersionmentioning

confidence: 99%

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Structural elements made with highly flowable UHPFRC: Correlating computational fluid dynamics (CFD) predictions and non-destructive survey of fiber dispersion with failure modes

Ferrara

Cremonesi

Faifer

et al. 2017

Engineering Structures

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Structural design with highly flowable Fibre Reinforced Concrete has to duly take into account the preferential alignment of fibers, which can be governed through the rheological properties of the fluid mixture and the casting process and by the geometry of the structure. The possibility of predicting the fiber alignment, by tailoring the casting process, and of non-destructively monitoring it, can foster more efficient structural applications and design approaches. Focusing on UHPFRC slabs with pre-arranged casting defects, the flowinduced alignment of the fibers has been predicted by means of a suitable CFD modelling approach and hence monitored via a non-destructive method based on magnetic inductance properties of the fiber reinforced composite. The comparison between the assessed data on the fibre orientation and the crack patterns as visualized by image analysis supports the effectiveness of casting flow modelling and non-destructive fiber dispersion monitoring in supporting the structural design of elements made with highly flowable fiber reinforced cementitious composites. Response to the reviewers of the manuscript ENGSTRUCT D-16-00912Structural elements made with highly flowable UHPFRC:can Computational Fluid Dynamics (CFD) and non-destructive survey of fiber dispersion complement structural design in predicting failure modes? submitted for publication to Engineering StructuresThe authors thank the reviewers for the time they have dedicated to read their manuscript and for the insightful comments they have made and for the overall evaluation of the manuscript.The authors have taken in high consideration all the comments, mainly made by the second reviewers, and have addressed them in the revised version of the manuscript, which is now resubmitted.In detail:RESPONSE TO REVIEWER 1 -The authors agree that citing "structural design" in the title may rise some expectations in the reader which the paper does not fully address. In view of this the tile has been modified as follows Structural elements made with highly flowable UHPFRC: correlating Computational FluidDynamics (CFD) predictions and non-destructive survey of fiber dispersion with failure modes? (see also response to 1st general remark of reviewer 2) -The thickness of the slab (30 mm) has been declared -Reference [93] (which has now become reference [94]) contains details about the test set-up and the mechanical test results with elaboration of the digital image correlation measurements of the cracks, which in this paper are taken as reference and simply compared with CFD predictions and ND fiber dispersion monitoring. -The citation by Svec has been added. As for the other reference cited by the reviewer, the authors are doubtful whether to cite or not since it is likely an internal publication which is not indexed nor widely available. -With reference to the slab with the defect at 1/3 of the side it is not true that the defect does not affect the crack pattern; even in the major crack does not develop along the casting defect line, the...

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“…When a SFRC cubic sample is placed inside the coil, a modification of the magnetic permeability of the medium is observed [12,13]. This modification leads to a change in the inductance [14] measured with the LCR impedance analyser. The method takes advantage of the fact that steel fibres are several orders of magnitude more magnetic than plain concrete [15].…”

Section: Introductionmentioning

confidence: 99%

Assessment of fibre content and 3D profile in cylindrical SFRC specimens

et al. 2015

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The inductive method proposed by Torrents et al. [1] and improved by Cavalaro et al. [2] is used to assess the fibre content and distribution in steel fibre reinforced concrete, providing valuable information for the design and the quality control. Despite several advantages, the method presents limitations. On one hand, it was conceived for the test of cubic specimens, which complicates its application in existing structures due to the difficulty to extract cubic cores. On the other hand, only a partial characterization of the fibre orientation is obtained given that the determination is restricted to the three axes of the specimen. With these measurements, it is not possible to derive the fibre orientation in other directions different from the ones used to test the sample. The objective of this paper is to propose an assessment of the fibre content and distribution in any direction using the inductive method and cylindrical specimens. For that, first a modification of the method is proposed. Then, new equations are deducted to generalize the test to samples with different shapes and to assess the anisotropy level as well as the directions with the maximum and the minimum fibre contribution. Next, an extensive experimental program and FEM numerical simulations are performed to validate and to determine the accuracy of the formulation developed. The results show that the application of these equations and the execution of only one additional measurement per specimen are enough to determine the fibre profile in all in-plane directions with a high accuracy.

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Low Frequency Electrical and Magnetic Methods for Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview

Cited by 20 publications

References 21 publications

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

Structural elements made with highly flowable UHPFRC: Correlating computational fluid dynamics (CFD) predictions and non-destructive survey of fiber dispersion with failure modes

Assessment of fibre content and 3D profile in cylindrical SFRC specimens

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