(a) in Rectangular Cartesian Coordinates with unit base vectors e1, e2, e3 a state of stress at a point within the material is given by Cauchy stress tensor 100 a b a 100 C C 100 Determine the constants a, b, c so that the stress vector O on the octahedral plane becomes zero. [ (b) The figure below shows load-displacement curves for biological tissue subjected to uniaxial tension. All tissue samples were circular in shape and experimentally tested at one of three orientations: 0, 450 and 90. Solid lines and discrete points indicate the finite element predictions and experimental measurements respectively. Diamonds, crosses and triangles indicate measurements taken at 0, 45 and 90 respectively. 1.5- Centre 1- point 0.5- 6. Relative displacement of grips (mm) Identify a type of constitutive model (isotropic elastic, anisotropic elastic, isotropic hyperelastic, anisotropic hyperelastic) that would be the most appropriate to simulate the mechanical behaviour of this biological tissue. Justify your choice. [4 marks) Load on grip (N)