# Orientations

 A user-defined orientation is used to define a local coordinate system for: definition of material properties—for example, anisotropic materials or jointed materials (a local coordinate system must be defined if anisotropic material properties are defined for solid elements); definition of local material directions, such as the in-plane fill and warp yarn directions of a fabric material or the fiber directions of anisotropic hyperelastic materials; definition of rebars in shell, membrane, and surface elements; definition of rotary inertia and connector elements; definition of coupling constraints; definition of loading directions for distributed general tractions, shear tractions, and general edge loads; definition of local tangent directions for contact in Abaqus/Standard; material calculations at integration points; output of components of stress, strain, and element section force; and definition of a local system of rigid body motion directions for inertia relief in Abaqus/Standard. A user-defined orientation cannot be used: at points where the smeared crack concrete material behavior (Concrete smeared cracking) is also used in Abaqus/Standard; to specify a local coordinate system for defining nodal coordinates—see Specifying a local coordinate system in which to define nodes or Specifying a local coordinate system for the nodal coordinates instead; or to specify a local coordinate system for applying loads and boundary conditions—see Transformed coordinate systems instead. Considerable generality is provided in the way the local system can be defined, since this system must often change from point to point because of the shape and construction of the structure being modeled. You can define the local orientation directly. The direct data methods provided in Abaqus are intended to give sufficient generality to model most cases easily: they are particularly useful for regular geometry. Distributions (Distribution definition) can be used to define spatially varying local coordinate systems for solid continuum, shell, and membrane (in Abaqus/Standard) elements directly for arbitrary geometries. In Abaqus/Standard you can alternatively define the local orientation in user subroutine ORIENT. The following topics are discussed:
 Related Topics Distribution definition In Other Guides About the material library Material data definition Fabric material behavior Distributed loads Kinematic coupling constraints Coupling constraints Inertia relief *ORIENTATION Creating datum coordinate systems

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