4. Use in Code_Aster

In Code_Aster, the definition of orthotropic elastic characteristics that are constants or functions of temperature are defined by the command DEFI_MATERIAU, keywords ELAS_ORTH, ELAS_ISTR, ELAS_ISTR_FOou ELAS_ORTH_FOpour shell elements and isoparametric massive elements or the constituent layers of a composite (see command DEFI_COMPOSITE).

To define the orthotropy coordinate system \((L,T,N)\) linked to the elements, we can refer to the documentation [U4.42.03] DEFI_COMPOSITE and [U4.42.01] AFFE_CARA_ELEM.

/ELAS_ORTH = _F (♦ E_L = ygl = ygl Longitudinal Young's Modulus.

♦ E_T = ygt transversal Young’s modulus.

◊ E_N = ygn normal Young’s modulus.

♦ GL_T = gltShear module in the \(\text{LT}\) plane.

◊ G_TN = GTNshear module in plane \(\mathrm{TN}\).

◊ G_LN = GLNshear module in plane \(\text{LN}\).

♦ NU_LT = zero Poisson’s ratio in the \(\text{LT}\) plane.

◊ NU_TN = nutn Poisson’s Ratio in the \(\mathrm{TN}\) plan.

◊ NU_LN = zero Poisson’s ratio in the \(\text{LN}\) plane. ◊ ALPHA_L = diln Longitudinal mean thermal expansion coefficient. ◊ ALPHA_T = said Transverse Mean Thermal Expansion Coefficient. ALPHA_N = DIN Normal mean thermal expansion coefficient.

Important note:

The presentation of this reference note is based on the convention of the books by J.L.Batoz and D.Gay. The documentation of DEFI_MATERIAU [U4.43.01] describes these choices, and the coefficient * NU_LT * is interpreted as follows in Code_ Aster: if we exert traction along the axis \(L\) giving rise to a deformation along this axis equal to \({\epsilon }_{L}=\frac{{\sigma }_{L}}{\text{ygl}}\) , we have a deformation along the axis \(T\) equal to: \({\epsilon }_{T}=-{\nu }_{\text{LT}}\cdot \frac{{\sigma }_{L}}{\text{ygl}}\) .