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  • 1
    Electronic Resource
    Electronic Resource
    Experimental investigation of phase-strain-temperature models for structurally embedded interferometric fiber-optic sensors (1993)
    Springer
    Experimental mechanics 33 (1993), S. 26-31 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Analytical models relating the optical phase change in a structurally embedded optical fiber sensor to the strain and temperature state integrated along that sensor path is investigated in this paper. Generalized plane strain elasticity solutions are combined with two phase-strain-temperature models to predict the thermomechanically induced optical retardation of the light propagating in the fiber sensor. These predictions are compared with experimental data obtained from Mach-Zehnder and Fabry-Perot sensors embedded in transverse compression and uniformly heated specimens respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02322546
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Displacement and strain measurement with automated grid methods (1991)
    Springer
    Experimental mechanics 31 (1991), S. 382-388 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An image-processing-based automated grid method is investigated to determine the method's displacement and strain accuracy limits, and how these limits are influenced by the choice of camera-calibration models. A CCD camera and a PC-based frame grabber are used to record grid spot motion, then ordering and centroiding are used to identify each spot and calculate their individual displacements. The displacements are fitted with a moving biquadratic surface, and the strains are obtained by analytical differentiation of that surface. Camera-calibration models which are considered include various combinations of image-perspective transformation, image stretching, and elliptical-lens distortion. The strain and displacement accuracy are explored through rigid-body motion and uniaxial tension tests. In the process, sensitivity to in-plane and out-of-plane rigid-body translation, and extreme sensitivity to in-plane rigid-body rotation (for non-synchronized frame grabbers) are confirmed. It is found that under the best conditions the displacement accuracy is 015 pixels and that the strain accuracy is 120 microstrain. Finally, the automated grid method is used to investigate the strains developed in an aluminum perforated strip subjected to uniaxial tension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325997
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fabry-Perot sensors for dynamic studies using spectrally based passive quadrature signal processing (1997)
    Springer
    Experimental mechanics 37 (1997), S. 119-125 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper describes a simple, optically passive detection scheme for in-line Fabry-Perot etalon (ILFE) sensors that is also useful for intrinsic Fabry-Perot (IFP) and extrinsic Fabry-Perot interferometer (EFPI) sensors. This detection scheme is based on two spectrally shiffed Bragg wavelengths from in-line Bragg gratings to produce two quadrature phase shifted signals from the spectral transfer function of the Fabry-Perot sensor. Using the amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA) as a low-coherence, high-power broad-band source, the passive detection technique is used to demonstrate the use of ILFE sensors in high strain rate dynamics studies. This study is designed to characterize the high strain rate response of optical fiber sensors and test their ability to monitor dynamic strain changes resulting from one-dimensional stress wave propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317846
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature and strain measurement by combining ILFE and bragg grating optical fiber sensors (1997)
    Springer
    Experimental mechanics 37 (1997), S. 414-419 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents two optical fiber sensor configurations that are capable of simultaneously measuring temperature and strain. These sensor configurations use serial and parallel combinations of in-line fiber etalon (ILFE) and in-fiber Bragg grating sensors, along with wavelength division multiplexing concepts. The results obtained while simultaneously varying the temperature over 130°C and strain field over 1500 με showed favorable agreement with thermistors and resistance strain gages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317307
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Interferometric-fiber-optic strain sensor (1988)
    Springer
    Experimental mechanics 28 (1988), S. 170-176 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An interferometric-fiber-optic sensor and an efficient fringe-detection scheme are described. The fiberoptic interferometer consists of two fibers; they are labeled the reference fiber and the sensing fiber. The reference fiber is arranged in a circular pattern, whereas the sensing fiber is arranged in an ‘S’ pattern. These fibers are exposed to the same strain field and each experiences a strain-induced phase shift. A difference in the phase shift between the two fibers indicates a change in strain. The strain-induced phase difference causes the interferometrically produced fringes to shift spatially. Analysis shows that the number of fringes passing an arbitrary point on a screen (the detection point) is linearly related to the strain in the fiber. In this analysis, the strain sensor is assumed to be perfectly bonded so that the fibers experience the same strain field as the specimen. It is further assumed that the sensor covers a sufficiently small area so that the strain can be considered constant over the entire strain sensor. Also, the phase change produced by transverse strain components (with respect to the fiber) induced by the specimen is assumed negligible compared to the phase changes attributable to the axial strain components. A cantilever beam was used as a specimen. Experimentally determined strains correlated well with the strains predicted by beam theory. The fringe-detection scheme described is a high-speed fringe counter. The speed of this counter is necessary to detect vibrational phase noise which is invisible to the human eye. Two photodiodes detect the fringes, and a logic circuit counts the fringe shifts, both strain and noise induced. Since noise is random in nature, it can be averaged out. This fringe detector exhibits good sensitivity and is the key to moving the sensor from the laboratory to the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317568
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Displacement pattern matching and boundary-element methods for elastic-plastic stress analysis (1990)
    Springer
    Experimental mechanics 30 (1990), S. 26-33 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A two-dimensional hybrid experimental-numerical technique for elastic-plastic stress analysis is presented. This technique results from merging two relatively new technologies in engineering mechanics: boundary-element methods and image processing. A syntactic pattern recognition scheme, termed ‘displacement pattern matching’ (DPM), determines the displacement boundary conditions which are used in an elasticplastic boundary-element method (EPBEM) code. The result is an automated stress-analysis tool. Displacement pattern matching is a process where displacements are measured by tracking an arbitrary array of ‘black’ spots on a ‘white’ specimen. The digitized images of the specimen are compared in a double-exposure format to determine displacements. Displacement pattern matching is a full-field technique, with spatial resolution on the order of. 1 pixels. Displacement pattern matching supplies the actual specimen displacement increments to the EPBEM code which is based on a von Mises, isotropic work-hardening constitutive model. Given these displacements and free surface conditions, EPBEM is able to incrementally calculate the internal state of stress at selected locations. Results obtained for a variety of geometries and loading conditions compared well with ANSYS finite-element solutions and selected published experimental solutions and therefore are encouraging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02322698
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Moiré analysis of thick composites with embedded optical fibers (1994)
    Springer
    Experimental mechanics 34 (1994), S. 300-305 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Moiré interferometry is used with Fourier transform fringe analysis to investigate the strain fields in a region local to 125-μm uncoated silica optical fibers embedded in a quasi-isotropic graphite/PEEK thick composite compression specimens. Analysis of several regions in several specimens showed no measurable strain concentrations resulting from the embedded optical fibers, even though the optical fibers clearly alter the local microarchitecture of the host material system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325144
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Extended range pseudo-heterodyne demodulation for fiber optic sensors (1996)
    Springer
    Experimental mechanics 36 (1996), S. 135-141 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This article describes a pseudo-heterodyne demodulation technique for interferometric fiber optic sensors that has a larger measurement range than is currently possible with pseudo-heterodyne demodulation. This sensor demodulation technique has a bandwidth of 30 Hz to 2.5 kHz, is capable of resolving optical phase angles as small as 5×10−4 rad, and has a maximum measurement range of tens of radians in a bandwidth of 30–500 Hz. A comparison between the response obtained from a resistance strain gage and a fiber optic sensor using this demodulation is favorable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02328709
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    In-fiber doppler velocimeter for velocity measurements of moving surfaces (1997)
    Springer
    Experimental mechanics 37 (1997), S. 328-332 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An optical fiber Doppler velocimeter using a 3×3 coupler with a large path imbalance Mach-Zehnder interferometer for passive demodulation of Doppler wavelength shifts is demonstrated. The particle velocity on the free surface end of the Hopkinson bar is directly obtained using the all-fiber Doppler velocimeter. These data show good agreement with the particle velocity predicted using strain gage data combined with one-dimensional stress wave propagation theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317426
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    Paper (German National Licenses)
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