Biaxial test specimen gripping jig [1]. 

Typical response of atherosclerotic plaque to cyclic testing. Dotted line represents the theoretical  "load envelope" of the tissue. [2]

[1] C.  Lally, A.  Reid and P.  Prendergast, "Elastic Behavior of Porcine Coronary Artery Tissue Under Uniaxial and Equibiaxial Tension", Annals of Biomedical Engineering, vol. 32, no. 10, pp. 1355-1364, 2004. 

[2] E.  Maher, A.  Creane, S.  Sultan, N.  Hynes, C.  Lally and D.  Kelly, "Inelasticity of Human Carotid Atherosclerotic Plaque", Annals of Biomedical Engineering, vol. 39, no. 9, pp. 2445-2455, 2011. Available: 10.1007/s10439-011-0331-4.