Using the Oak Ridge National Laboratory (ORNL) constitutive model in plasticity and creep calculations

The ORNL constitutive model in Abaqus/Standard applies to Types 304 and 316 stainless steel, as specified in nuclear standard NE F9–5T(1981). The constitutive theory is uncoupled into a rate-independent plasticity response and a rate-dependent creep response, each of which is governed by a separate constitutive law. For more information, see ORNL – Oak Ridge National Laboratory constitutive model, and ORNL constitutive theory.

  1. Create a material model as described in one of the following sections:

  2. From the Suboptions menu in the Edit Material dialog box, select Ornl.

    A Suboption Editor appears.

  3. In the Saturation rates for kinematic shift field, enter a value for A, the parameter equal to the saturation rates for kinematic shift caused by creep strain. This parameter is defined by Equation (15) of Section 4.3.3--3 of the Nuclear Standard. The default value is 0.3. Set A=0.0 to use the 1986 revision of the Standard.

  4. In the Rate of kinematic shift wrt creep strain field, enter a value for H, the parameter equal to the rate of kinematic shift with respect to creep strain. This parameter is defined by Equation (7) of Section 4.3.2–1 of the Nuclear Standard. Set H=0.0 to use the 1986 revision of the Standard. If you omit this parameter, Abaqus determines the value of H according to Section 4.3.3–3 of the 1981 revision of the Standard.

  5. If desired, toggle on Invoke reset procedure to invoke the optional α reset procedure described in Section 4.3.5 of the Nuclear Standard.

  6. Click OK to return to the Edit Material dialog box.