Envelope calculations

You use envelope calculations to retrieve the extreme value for an output variable over a number of fields. Envelope calculations are especially useful for retrieving the extreme values over a number of load cases.

The following operators consider a list of fields and perform the envelope calculation:

(env, lcIndex) = maxEnvelope([field1, field2, ...])
(env, lcIndex) = minEnvelope([field1, field2, ...])

(env, lcIndex) = maxEnvelope([field1, field2, ...],
                             invariant)
(env, lcIndex) = minEnvelope([field1, field2, ...],
                             invariant)

(env, lcIndex) = maxEnvelope([field1, field2, ...],
                             componentLabel)
(env, lcIndex) = minEnvelope([field1, field2, ...],
                             componentLabel)

The envelope commands return two FieldOutput objects.

  • The first object contains the requested extreme values.

  • The second object contains the indices of the fields for which the extreme values were found. The indices derive from the order in which you supplied the fields to the command.

The optional invariant argument is a Symbolic Constant specifying the invariant to be used when comparing vectors or tensors. The optional componentLabel argument is a odb_String specifying the component of the vector or tensor to be used for selecting the extreme value.

The following rules apply to envelope calculations:

  • Abaqus compares the values using scalar data. If you are looking for the extreme value of a vector or a tensor, you must supply an invariant or a component label for the selection of the extreme value. For example, for vectors you can supply the MAGNITUDE invariant and for tensors you can supply the MISES invariant.

  • The fields being compared must be similar. For example,

    • VECTOR and TENSOR_3D_FULL fields cannot appear in the same list.

    • The output region of all the fields must be the same. All the fields must apply to the whole model, or all the fields must apply to the same set.