Experimental determination of stress concentrations in orthotropic composites

Baek, Tae Hyun; Rowlands, R. E.

doi:10.1243/0309324991513902

Cited by 17 publications

(4 citation statements)

References 11 publications

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“…0.509 i Figure 2 shows the test specimen for this numerical study. This specimen was used in the previous analyses using both the moiré-numerical hybrid method (2) and numerical technique (3) . The conceptual discretization is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Full-Field Stress Determination Around Circular Discontinuity in a Tensile-Loaded Plate using x-displacements Only

Baek

Chung

Panganiban

2008

JMMP

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The significant effects of stress raisers demand well-defined evaluation techniques to accurately determine the stress along the geometric boundary. A simple and accurate method for the determination of stress concentration around circular geometric discontinuity in a tensile-loaded plate is illustrated. The method is based on the least-squares technique, mapping functions, and a complex power series representation (Laurent series) of the stress functions for the calculation of tangential stress around the hole. Traction-free conditions were satisfied at the geometric discontinuity using conformal mapping and analytic continuation. In this study, we use only a relatively small amount of x-component displacement data of points away from the discontinuity of concern with their respective coordinates. Having this information we can easily obtain full-field stresses at the edge of the geometric discontinuity. Excellent results were obtained when the number of terms of the power series expansions, m = 1. The maximum stress concentration calculation results using the present method and FEM using ANSYS agree well by less than one per cent difference. Experimental advantage of the method underscores the use of relatively small amount of data which are conveniently determined being away from the edge. Moreover, the small amount of measured input data needed affords the approach suitable for applications such as the multi-parameter concept used to obtain stress intensity factors from measured data. The use of laser speckle interferometry and moiré interferometry are also potential future related fields since the optical system for one-directional measurement is much simple.

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Section: Resultsmentioning

confidence: 99%

“…(7). For example, there would be two coefficients (a -1 , a 1 ) for m=1, four coefficients (a -3 , a -1 , a 1 , a 3 ) for m=3, six coefficients (a -5 , a -3 , ..., a 3 , a 5 ) for m=5, and so on (3) . An over-determined system of simultaneous linear equations, i.e.…”

Section: Resultsmentioning

confidence: 99%

Full-Field Stress Determination Around Circular Discontinuity in a Tensile-Loaded Plate using x-displacements Only

Baek

Chung

Panganiban

2008

JMMP

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“…The accuracy and reliability of the said in-plane displacement measuring method had been well-established. [4][5][6]8,9 For this reason, it is a useful tool for the hybrid stress analysis presented herein. In this study, phase-shifting method using Fourier transform was utilized.…”

Section: Optical Experimentsmentioning

confidence: 99%

A hybrid stress measurement using only x-displacements by phase shifting method with fourier transform (PSM/FT) in laser speckle interferometry and least squares method

Baek

Rudolphi

2010

Int. J. Precis. Eng. Manuf.

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Stress measurement around the edge of a circular hole at the center of a tensile-loaded plate was performed using an improved hybrid method. Phase-shifting method by Fourier transformation (PSM/FT) in laser speckle interferometry was utilized to measure micro-scale displacement of points away from the edge of the hole. Using few x-displacement and location data only, least-squares method integrated with a Laurent series representation of the stress function and local collocation was used to do reliable stress evaluation on the hole boundary. Traction-free conditions are satisfied at the geometric discontinuity using conformal mapping and analytic continuation. The results of the present improved hybrid method agree well with that of finite element method using commercial software, ABAQUS. Different values of number of term (m) in the complex stress functions were tested to see its effect. In the comparison between input x-displacement data and calculated the hybrid method is effective with an error below 1% in all values of m. On the other hand, it came out that at point of high stress concentration ( θ =90°), well-comparable results was attained at decreasing value of m. The best value of m is consistently known to be equal to 1 which results are accurate by less than one percent. Results showed that the method is accurate and reliable as compared with the widely-used ABAQUS.

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“…Unlike the hybrid method based on Mitchell solution, which is limited to isotropic response, the CVM, based on analytic continuation and mapping techniques, were extensively used to evaluate reliable hybrid stresses in loaded isotropic and orthotropic components on the boundary of different geometrical discontinuities (side notch, circular hole, elliptical hole) and stress intensity factors in cracks from different experimental techniques: thermoelastic data, 20–24 photoelastic data, 25 strains, 26 and displacements. 27,28 The hybrid method based on complex-variable formulation is suitable for finite (can be difficult theoretically) and infinite geometries. Advantages over other such hybrid analyses include the fact that this hybrid method based on complex-variable formulation satisfies the equilibrium, compatibility, and local boundary conditions; requires few measured input data which can be arbitrarily located; requires few terms in the stress function representation; does not necessitate knowing the entire boundary, distant loading conditions, or material elastic constants; applies for isotropic and anisotropic responses; smooths the original measured input data; enhances the edge information; and determines the individual full-field stresses, strains, and displacements throughout, including on the edge of the hole, even though no information were used there.…”

Section: Introductionmentioning

confidence: 99%

Hybrid stress analysis of a near-surface circular hole in finite structures

Alshaya

Lin

2019

Proceedings of the Institution of Mechanical Engineers, Part C:

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The ability to stress-analyze complicated structures from recorded load-induced temperatures is demonstrated. The considered structures have a near-surface hole and subjected to a concentrated load. The complexity of the structure is simplified by conformal mapping, the traction-free condition on the boundary of the hole is analytically satisfied by analytic continuation, and the equilibrium and compatibility conditions are satisfied by means of Airy stress function in complex-variable formulation. For isotropic member that is cyclically loaded within its elastic range, the produced in-phase temperature variations are linearly proportional to the local changes in the normal stresses. Even though no recorded thermal data were used at or near to the edges, the present hybrid method simultaneously separates the load-induced temperatures into the individual stress components, determines reliably the boundary stress and hence the stress concentration, and smooths the measured input data. Unlike prior capabilities of using geometrical symmetry to simply the stress function representation, the present analysis retains all the terms in the stress functions. Therefore, the considered hybrid stress analysis approach of such complex structures extends significantly the applicability of thermoelastic stress analysis compared to prior capabilities and is considered to be the most complicated formulation of the hybrid complex-variable method to date. To support the reliability of the present hybrid method, the results were compared with finite element predictions and previous results based on Mitchell solution.

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Experimental determination of stress concentrations in orthotropic composites

Cited by 17 publications

References 11 publications

Full-Field Stress Determination Around Circular Discontinuity in a Tensile-Loaded Plate using x-displacements Only

Full-Field Stress Determination Around Circular Discontinuity in a Tensile-Loaded Plate using x-displacements Only

A hybrid stress measurement using only x-displacements by phase shifting method with fourier transform (PSM/FT) in laser speckle interferometry and least squares method

Hybrid stress analysis of a near-surface circular hole in finite structures

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