Mess- und Analysemethoden in der Laserakustik bei breitbandiger Laseranregung

Singer, Ferdinand

doi:10.1515/teme-2014-0030

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…This method uses two signals of the same acoustic wave

and

with a certain path difference

and compares the phase change between both signals. This is achieved with the following formula [ 55 , 56 ]:

…”

Section: Materials and Methodsmentioning

confidence: 99%

“…The phase difference

can be calculated from the Fourier-transformed signals of both windowed signals [ 56 ]:

where

is the operator for the fast Fourier transformation, ∗ is the operator for the complex conjugated value, and

and

are operators for the imaginary and real parts, respectively.…”

Section: Materials and Methodsmentioning

confidence: 99%

“…The phase difference ∆ϕ can be calculated from the Fourier-transformed signals of both windowed signals [56]:…”

Section: Determination Of Phase Velocitymentioning

confidence: 99%

See 2 more Smart Citations

Frequency-Resolved High-Frequency Broadband Measurement of Acoustic Longitudinal Waves by Laser-Based Excitation and Detection

Brand,

Drese

2024

Sensors

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Optoacoustics is a metrology widely used for material characterisation. In this study, a measurement setup for the selective determination of the frequency-resolved phase velocities and attenuations of longitudinal waves over a wide frequency range (3– 55MHz) is presented. The ultrasonic waves in this setup were excited by a pulsed laser within an absorption layer in the thermoelastic regime and directed through a layer of water onto a sample. The acoustic waves were detected using a self-built adaptive interferometer with a photorefractive crystal. The instrument transmits compression waves only, is low-contact, non-destructive, and has a sample-independent excitation. The limitations of the approach were studied both by simulation and experiments to determine how the frequency range and precision can be improved. It was shown that measurements are possible for all investigated materials (silicon, silicone, aluminium, and water) and that the relative error for the phase velocity is less than 0.2 .

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“…This method uses two signals of the same acoustic wave

and

with a certain path difference

and compares the phase change between both signals. This is achieved with the following formula [ 55 , 56 ]:

…”

Section: Materials and Methodsmentioning

confidence: 99%

“…The phase difference

can be calculated from the Fourier-transformed signals of both windowed signals [ 56 ]:

where

is the operator for the fast Fourier transformation, ∗ is the operator for the complex conjugated value, and

and

are operators for the imaginary and real parts, respectively.…”

Section: Materials and Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Frequency-Resolved High-Frequency Broadband Measurement of Acoustic Longitudinal Waves by Laser-Based Excitation and Detection

Brand,

Drese

2024

Sensors

View full text Add to dashboard Cite

show abstract

“…Knowing the thickness of the specimens,

, the frequency dependent phase velocity can be calculated [ 58 ]:

…”

Section: Methodsmentioning

confidence: 99%

Quantification of Humidity and Salt Detection in Historical Building Materials via Broadband Radar Measurement

Blaschke,

Brand,

Drese

2023

Sensors

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For the investigation of moisture and salt content in historic masonry, destructive drilling samples followed by a gravimetric investigation is still the preferred method. In order to prevent the destructive intrusion into the building substance and to enable a large-area measurement, a nondestructive and easy-to-use measuring principle is needed. Previous systems for moisture measurement usually fail due to a strong dependence on contained salts. In this work, a ground penetrating radar (GPR) system was used to determine the frequency-dependent complex permittivity in the range between 1 and 3 GHz on salt-loaded samples of historical building materials. By choosing this frequency range, it was possible to determine the moisture in the samples independently of the salt content. In addition, it was possible to make a quantitative statement about the salt level. The applied method demonstrates that with ground penetrating radar measurements in the frequency range selected here, a salt-independent moisture determination can be carried out.

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“…Humidity and water are environmentally abundant, and ingress into and migration within the building material leading to weathering is a common challenge [1][2][3][4][5]. In order to prevent permanent damage to the building shell due to weathering, it is necessary to determine the exact moisture and salt content of the building and its masonry [6].…”

Section: Introductionmentioning

confidence: 99%

Quantification of Moisture in Masonry via AI-Evaluated Broadband Radar Reflectometry

Frenzel,

Blaschke,

Franzen

et al. 2023

Heritage

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Humidity, salt content, and migration in building materials lead to weathering and are a common challenge. To understand damage phenomena and select the right conservation treatments, knowledge on both the amount and distribution of moisture and salt load in the masonry is crucial. It was shown that commercial portable devices addressing moisture are often limited by the mutual interference of these values. This can be improved by exploiting broadband radar reflectometry for the quantification of humidity in historic masonry. Due to the above-mentioned limitations, today’s gold standard for evaluating the moisture content in historic buildings is still conducted by taking drilling samples with a subsequent evaluation in a specially designed laboratory, the so-called Darr method. In this paper, a new broadband frequency approach in the range between 0.4 and 6 GHz with improved artificial-intelligence data analysis makes sure to optimize the reflected signal, simplify the evaluation of the generated data, and minimise the effects of variables such as salt contamination that influence the permittivity. In this way, the amount of water could be determined independently from the salt content in the material and an estimate of the salt load. With new machine learning algorithms, the analysis of the permittivity is improved and can be made accessible for everyday use on building sites with minimal intervention by the user. These algorithms were trained with generated data from different drying studies on single building bricks from the masonries. The findings from the laboratory studies were then validated and evaluated on real historic buildings at real construction sites. Thus, the paper shows a spatially resolved and salt-independent measurement system for determining building moisture.

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Mess- und Analysemethoden in der Laserakustik bei breitbandiger Laseranregung

Cited by 8 publications

References 13 publications

Frequency-Resolved High-Frequency Broadband Measurement of Acoustic Longitudinal Waves by Laser-Based Excitation and Detection

Frequency-Resolved High-Frequency Broadband Measurement of Acoustic Longitudinal Waves by Laser-Based Excitation and Detection

Quantification of Humidity and Salt Detection in Historical Building Materials via Broadband Radar Measurement

Quantification of Moisture in Masonry via AI-Evaluated Broadband Radar Reflectometry

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