• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.15-22
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• 2007

A hybrid experimental-numerical method is presented for determining the stresses around a circular hole in a finite-width, tensile loaded plate. Measured fringe orders along straight lines provided the input information on the external boundary of the hybrid element. In order to see the effects of varying stress field, different numbers of terms in a power-series representation of the complex type conformal mapping stress function were tested. For qualitative comparison, actual isochromatic fringes were compared with reconstructed theoretical fringes using stress-optic law. For quantitative comparison, relative errors and standard deviations with respective to relative errors were analyzed for all measured points by changing the number of terms of stress function. The hybrid results are highly comparable with those predicted by FEA. The results show that this approach is effective and promising because isochromatic data along the straight lines in photoelasticity can be conveniently measured by use of phase shifting photoelasticity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1287-1292
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• 2010

In this paper, a hybrid technique is presented. First, the isochromatic fringe data of a given set of points are calculated by the finite element method and are used as input data in complex variable formulations. Then the numerical model of the specimen with a central inclined crack is transformed from the physical plane to the complex plane by conformal mapping. The stress field is analyzed and the mixed-mode stress intensity factors are calculated for this complex plane. The stress intensity factors are calculated by the finite element method as well as by a theoretical method and compared with each other. In order to conveniently compare these values with each other, both actual and regenerated photoelastic fringe patterns are multiplied by a factor of two and sharpened by digital image processing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1297-1304
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• 2000

The reflective photoelastic experiment can be used more effectively than the transparent type in industrial fields. Therefore the reflective photoelastic experimental hybrid method applied to the fatigue fracture problems is introduced in this research. It is verified that the reflective photoelastic experimental hybrid method is very useful on the determination of crack propagation velocity and stress intensity factor of the fatigue crack and on the separation of stress components in the vicinity of fatigue crack tip etc.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.319-320
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• 2009

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.434-442
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• 2001

When the interfacial crack of two dissimilar isotropic bi-materials is propagated with constant velocity along the interface, stress and displacement components are derived in this research. The dynamic photoelastic experimental hybrid method for bimaterial is introduced. It is assured that stress components and dynamic photoelastic hybrid method developed in this research are valid. Separating method of stress component is introduced from only dynamic photoelastic fringe patterns. Crack propagating velocity of interfacial crack is 80∼85% (in case of aluminum, 24.3∼25.9%) of Rayleigh wave velocity of epoxy resin. The near-field stress components of crack-tip are similar with those of pure isotropic material under static or dynamic loading, but very near-field stress components of crack-tip are different from those.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1799-1806
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• 2004

The static photoelastic experiment was applied to orthotropic materials. And then the specimens used in photoelastic experiment were fractured under static load. The static photoelastic experimental hybrid method for orthotropic material was introduced and its validity had been assured. Crack propagation criterion used the stress components, which are considered the higher order terms, obtained from the static photoelastic experimental hybrid method was introduced and it was applied to the minimum strain energy density criterion, the maximum tangential stress criterion and mode mixity. Comparing the actual initial angle of crack propagation with the theoretical initial angle of crack propagation obtained from the above failure criterions, the validities of the above two criterions are assured and the optimal distance (${\gamma}$) from the crack-tip is 0.01mm in order to get the initial angle of crack propagation of orthotropic material(C.F.E.C.).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2220-2227
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• 2000

In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. The dynamic photoelastic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced. Dynamic loading device manufactured in this research can be used on the research of dynamic behavior when mechanical resonance is produced and when crack is propagated with the constant velocity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.345-352
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• 2013

In this research, a study on stress shape functions was conducted to analyze the contact stress problem by using a hybrid photoelasticity. Because the contact stress problem is generally solved as a half-plane problem, the relationship between two analytical stress functions, which are compositions of the Airy stress function, was similar to one of the crack problem. However, this relationship in itself could not be used to solve the contact stress problem (especially one with singular points). Therefore, to analyze the contact stress problem more correctly, stress shape functions based on the condition of two contact end points had to be considered in the form of these two analytical stress functions. The four types of stress shape functions were related to the stress singularities at the two contact end points. Among them, the primary two types used for the analysis of an O-ring were selected, and their validities were verified in this work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.988-1000
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• 1999

An experimental study is presented for the effect of number of terms of a pewee series type stress function on stress analysis around a hole in tensile loaded plate. The hybrid method coupling photoelastsic data inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width tensile plate. In order to measure isochromatic data accurately, actual photoelastic fringe patterns are two times multiplied and sharpened by digital image processing. For qualitative comparison, actual fringes are compared with calculated ones. For quantitative comparison, percentage errors and standard deviations with respect to percentage errors are caculated for all measured points by changing the number of terms of stress function. The experimental results indicate that stress concentration factors analyzed by the hybrid method are accurate within three percent compared with ones obtained by theoretical and finite element analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1229-1236
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• 2004

The specimen materials used in this research are isotropic epoxy resins. The static photoelastic experiment was applied to them. And then the specimens used in photoelastic experiment were fractured under static load. The static photoelastic experimental hybrid method was introduced and its validity had been assured. Crack propagation criterion used the stress components, which are considered the higher order terms, obtained from the static photoelastic experimental hybrid method was introduced and it was applied to the minimum strain energy density criterion, the maximum tangential stress criterion and mode mixity. Comparing the actual initial angle of crack propagation with the theoretical initial angle of crack propagation obtained from the above failure criterions, the validities of the above two criterions are assured and the optimal distance (r) from the crack-tip is 0.01mm in order to get the initial angle of crack propagation of isotropic epoxy resin.