photoelastic
/ˌfəʊtəʊɪˈlastɪk/Science and Engineering
adjective
Employing or exhibiting the property of becoming birefringent when mechanically stressed, so that stress patterns in such a substance can be determined from the interference fringes formed by polarized light passed through it.
Origin
Early 20th century. From photo- + elastic. Compare earlier photoelasticity.