Luminescent photoelastic coatings


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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E :

electric field wave magnitude

h :

coating thickness

I :

measured emission intensity, proportional toE 2

K :

photoelastic optical sensitivity

r :

luminescence anisotropy

t :



analyzer angle


shear strain


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


angular retardation


normal strain


principal direction


wavelength of light


Poisson constant


efficiency or attenuation


standard deviation


angular frequency of light

avg :


ex :


c :


em :


f :

fast axis

H :

horizontal orientation

max :


np :


p :

polarized or polarization

q :


r :


s :

slow axis

t :

transmission or true

V :

vertical orientation


primary in-plane principal direction


secondary in-plane principal direction


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Hubner, J.P., Ifju, P.G., Schanze, K.S. et al. Luminescent photoelastic coatings. Experimental Mechanics 44, 416–424 (2004).

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Key Words

  • Luminescent
  • photoelastic coating
  • strain
  • full-field