Photoelastic stress analysis using an object step-loading method

Ng, Tuck Wah

doi:10.1007/bf02317849

Cited by 27 publications

(19 citation statements)

References 11 publications

(3 reference statements)

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“…The numerical results shown in Fig. 8 agree well with those predicted theoretically by means ofeq (13). The experimental results follow the same trend as the numerical and the theoretical results, with a deviation of less than 0.03 fringe orders, most likely due to various experimental errors not present in the numerical simulation, such as the error of the quarter-wave plates and the errors of the acquisition system.…”

Section: Compari Son Wi Th Numeri Cal Si Mulati On and Theorysupporting

confidence: 88%

“…13 In photoelasticity, unlike other optical methods such as moir6 and holographic interferometry, the light intensity depends on two parameters related to the stress field, that is, the retardation (isochromatics) ~ and the isoclinic parameter cc The evaluation of the retardation using the Fourier transform method with carrier fringes is considered in Ref. 4, where the alignment between the principal stresses in the model and in the carder is assumed.…”

Section: Introductionmentioning

confidence: 99%

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Limitation of fourier transform photoelasticity: Influence of isoclinics

Ajovalasit

Zuccarello

2000

Experimental Mechanics

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ABSTRACT--The application of the Fourier transform to photoelasticity was used in the evaluation of the retardation using a carrier system of fringes. In photoelasticity, the light intensity from the analyzer in a circular polariscope depends on both the retardation (isochromatics) and the isoclinic parameter. The theoretical analysis shows that the angle between the principal stresses in the model and in the carrier system of fringes influences the evaluation of the retardation (isochromatics), as occurs when misaligned compensators (namely, Babinet) are used. As a consequence, this method may not be applied as a full-field technique, although the error is small if the angle between the principal stresses in the model and in the carrier is less than 25 deg. Numerical simulations and experimental tests were conducted to corroborate this prediction. KEY WORDS--Experimental mechanics, image processing, photoelasticityNomenclature C = stress optic coefficient d = thickness of the model f = fringe frequency of the model fc = fringe frequency of the carrier I --light intensity emerging from the polariscope I0 = background intensity I1 = modulation term 12 = noise If = intensity of the in-phase signal Iq = intensity of the in-quadrature signal ---angle between the maximum principal stress in the model and the horizontal reference axis ~c --angle between the maximum principal stress in the carrier and the horizontal reference axis fir = angle between the maximum principal stresses in the model and in the carrier (absolute value) --retardation of the model ~c = retardation of the carrier ~c* = wrapped retardation of the carrier ~t = total retardation 8;" --wrapped total retardation k = light wavelength 01, or2 = principal stresses in the model (gl > or2) Crlc, ~2c = principal stresses in the carrier (eric > Cr2c)

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Section: Compari Son Wi Th Numeri Cal Si Mulati On and Theorysupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Limitation of fourier transform photoelasticity: Influence of isoclinics

Ajovalasit

Zuccarello

2000

Experimental Mechanics

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“…Therefore, the principal orientation can be determined using either equation (6b) or (7). Finally, equation (6c) is used to evaluate the sum of principal stresses, but once again the fringe order and sign must be interpreted by tracking the time variation of the fringe data in order to determine whether the thickness increases or decreases.…”

Section: Experimental Arrangementmentioning

confidence: 99%

“…Phase shifting photoelasticity has been studied recently by numerous researchers (see [1,4,7,8] and others). The main idea behind the phase shifting methods is to acquire multiple images with a known phase change introduced in the optical path that are in addition to the phase change caused by the stressed specimen; this is accomplished by introducing changes in the orientations of the quarter-wave plates, and/or the polarizers.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Measurement of Two Dimensional Stress Components in Birefringent Materials

Lim

Ravi‐Chandar

2008

Exp Mech

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We adopt classical methods of photoelasticity and Mach-Zehnder interferometry in a combined arrangement in order to determine both principal stresses and their orientations simultaneously. The method is equally applicable to static and dynamic problems. In dynamic problems the measurement may be made with a high-speed photodetector at very high temporal resolution at a single point or a small array of points depending on the detector array and recording device; this eliminates the need for a high-speed photographic system, but more importantly the method described here provides complete, time-resolved evolution of all stress components. Examples of application of the method are demonstrated.

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“…It is important to remark that, as mentioned by Larkin [1], the interferogram demodulation does not require an accurate estimate of the fringe direction-field. The second was a simulated load-stepping photoelastic experiment using the model of a circular disc under diametral compression to evaluate the relative retardation [9,10]. Figure 3 (A) shows some samples of a sequence increasing the load compression.…”

Section: Numerical Experimentsmentioning

confidence: 99%

N-dimensional regularized fringe direction-estimator

Villa¹,

Quiroga²,

Servı́n³

et al. 2010

Opt. Express

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Abstract:It has been demonstrated that the vectorial fringe-direction field is very important to demodulate fringe patterns without a dominant (or carrier) frequency. Unfortunately, the computation of this direction-filed is by far the most difficult task in the full interferogram phase-demodulation process. In this paper we present an algorithm to estimate this fringedirection vector-field of a single n-dimensional fringe pattern. Despite that our theoretical results are valid at any dimension in the Euclidean space, we present some computer-simulated results in three dimensions because it is the most useful case in practical applications. As herein demonstrated, our method is based on linear matrix and vector analysis, this translates into a low computational cost.

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Photoelastic stress analysis using an object step-loading method

Cited by 27 publications

References 11 publications

Limitation of fourier transform photoelasticity: Influence of isoclinics

Limitation of fourier transform photoelasticity: Influence of isoclinics

Dynamic Measurement of Two Dimensional Stress Components in Birefringent Materials

N-dimensional regularized fringe direction-estimator

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