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Euler-Rodrigues and Cayley Formulae for Rotation of Elasticity TensorsMechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854-8058, USA It is well known that rotation in three dimensions can be expressed as a quadratic in a skew symmetric matrix via the Euler-Rodrigues formula. A generalized Euler-Rodrigues polynomial of degree 2n in a skew symmetric generating matrix is derived for the rotation matrix of tensors of order n. The Euler-Rodrigues formula for rigid body rotation is recovered by n = 1. A Cayley form of the nth-order rotation tensor is also derived. The representations simplify if there exists some underlying symmetry, as is the case for elasticity tensors such as strain and the fourth-order tensor of elastic moduli. A new formula is presented for the transformation of elastic moduli under rotation: as a 21-vector with a rotation matrix given by a polynomial of degree 8. Explicit spectral representations are constructed from three vectors: the axis of rotation and two orthogonal bivectors. The tensor rotation formulae are related to Cartan decomposition of elastic moduli and projection onto hexagonal symmetry.
Key Words: rotation tensor transverse isotropy Cartan
This version was published on August
1, 2008 Mathematics and Mechanics of Solids, Vol. 13, No. 6,
465-498 (2008) |
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