Deviatoric stress and strain

With these deviatoric stress and strain responses, separating the volumetric response from the regular stresses and strain elements, the linear elastic constitutive relations become particularly simple and transparent as... 

By rewriting the constitutive equations as in Eq. 9.4, each equation contains only one material property the deviatoric stress and strain are related by the shear modulus, G, while the dilatational stress and strain are related by the bulk modulus, K. 

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