Luminescent photoelastic coatings

Abstract

In this paper we describe a new technique to measure the surface strain field on complex three-dimensional structural components under static load. It is cost-efficient to implement and suitable to be integrated in the product design cycle in conjunction with finite element analysis tools. The technique employs novel luminescent photoelastic coatings and digital imaging to map the in-plane strain field. The coatings consist of a binder, generally polymeric in nature, and luminescent dyes that are applied to the surface of a test part using conventional aerosol techniques. When excited with circular polarized ultraviolet or blue illumination, the corresponding emission intensity from the coating is measured via a digital camera. The relative change in emission magnitude and phase as measured after passing through an analyzing polarizer is related to the in-plane shear strain and its corresponding principal direction. Several basic test results are presented and discussed, showing quantitative, repeatable, and high spatial resolution measurements.

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Abbreviations

E :

electric field wave magnitude

h :

coating thickness

I :

measured emission intensity, proportional toE 2

K :

photoelastic optical sensitivity

r :

luminescence anisotropy

t :

time

α:

analyzer angle

γ:

shear strain

δ:

optical strain response, φ p for a dual-layer coating

Δ:

angular retardation

ɛ:

normal strain

θ:

principal direction

λ:

wavelength of light

ν:

Poisson constant

ϕ:

efficiency or attenuation

σ:

standard deviation

ω:

angular frequency of light

avg :

average

ex :

excitation

c :

combined

em :

emission

f :

fast axis

H :

horizontal orientation

max :

maximum

np :

non-polarized

p :

polarized or polarization

q :

quantum

r :

residual

s :

slow axis

t :

transmission or true

V :

vertical orientation

1:

primary in-plane principal direction

2:

secondary in-plane principal direction

References

  1. 1.

    Coker, E.G. andFilon, L.N.G., A Treatise on Photoelasticity, Cambridge University Press, London (1931).

    Google Scholar 

  2. 2.

    Frocht, M.M., Photoelasticity, Vol. 1, Wiley, New York (1941), Vol. 2 (1948).

    Google Scholar 

  3. 3.

    Zandman, F., Redner, S., andDally, J.W., Photoelastic Coatings Iowa State University Press, Ames (1977).

    Google Scholar 

  4. 4.

    Dally, J.W. andRiley, W.F., Experimental Stress Analysis, 3rd edition, McGraw-Hill, New York, 424–500, 541–580 (1991).

    Google Scholar 

  5. 5.

    Ramesh, K. andMangal, S.K., “Data Acquisition Techniques in Digital Photoelasticity: A Review,” Optics and Lasers Engineering,30,53–75 (1998).

    Article  Google Scholar 

  6. 6.

    Barone, S. andPatterson, E.A., “Full-Field Separation of Principle Stresses by Combined Thermo- and Photoelasticity,” EXPERIMENTAL MECHANICS,36(4),318–324 (1996).

    Article  Google Scholar 

  7. 7.

    Hubner, J.P., Ifju, P.G., Schanze, K.S., Jaing, S., Liu, Y., and El-Ratal, W., “Luminescent Strain Sensitive Coatings,” AIAA Journal, in press, AIAA Paper 2003-1437 (2004).

  8. 8.

    Lesniak, J.R., Zickel, M.J., Welch, C.S., and Johnson, D.F., “An Innovative Polariscope for Photoelastic Stress Analysis,” Proceedings of Society of Experimental Mechanics Spring Conference, June, 219–244 (1997).

  9. 9.

    Lesniak, J.R., Bazile, D.J., and Zickel, M.J., “New Coating Techniques in Photoelasticity,” Proceedings of Society of Experimental Mechanics Spring Conference, June (1999).

  10. 10.

    Chen, L., Hubner, J., Liu, Y., Schanze, K., Ifju, P, Nicolosi, J., and El-Ratal, W. “Characterization of a New Luminescent Photoelastic Coating,” SEM X International Congress and Exposition on Experimental and Applied Mechanics, Paper 192, June (2004).

  11. 11.

    Lakowicz, J.R., Principles of Fluorescence Spectroscopy, 2nd edition, Kluwer Academic/Plenum, New York, 291–303 (1999).

    Google Scholar 

  12. 12.

    Hubner, J.P., Ifju, P.G., Schanze, K.S., Jiang, S., Liu, Y., Jenkins, D.A., and El-Ratal, W., Method and Apparatus for Measuring Strain Using a Luminescent Photoelastic Coating, US Patent Application 10/407,602 (2003).

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Hubner, J.P., Ifju, P.G., Schanze, K.S. et al. Luminescent photoelastic coatings. Experimental Mechanics 44, 416–424 (2004). https://doi.org/10.1007/BF02428095

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Key Words

  • Luminescent
  • photoelastic coating
  • strain
  • full-field