Defining and Running the Reliability Study

You define a Robustness and Reliability study that assesses the impact of installation and manufacturing tolerances on design performance. To reduce the runtime for these studies, you predict the responses using the previously generated surrogate models.

Generally, for a reliability study to be accurate, the study must consider a high number (hundreds to thousands) of permutations around the best design. In this tutorial, you run the reliability study with 500 designs using the surrogate models computed previously.

In this study, you apply a probability distribution to the input parameters. This probability distribution describes the likelihood that an input parameter will take a particular value. For the industrial exhaust manifold, you specify a relative triangular variation of ±3.5 % around the best design data points. You specify the data points as baseline values using the input parameter values that you obtained for the best design—Design 66.

To define the reliability study:

  1. Right-click the Design Studies node and select New.
  2. Rename the Design Study 2 node as Reliability.
  3. Select the Reliability node and set the following properties:
    Property Setting
    Study Type Robustness and Reliability
    Evaluation Method Surrogates
  4. Select the Reliability > Robustness and Reliability Settings node and set Designs to Run to 500.
  5. Specify the input parameters:
    1. Right-click the Input Parameters node and select Edit.
    2. In the Reliability - Input Parameters dialog, click Add/Remove Parameters.
    3. In the Select Reference Parameters dialog, select all parameters except Deflector Translation _Z and Deflector Thickness, then click OK.


    4. In the Reliability - Input Parameters dialog, specify the following settings for each input parameter:
      Name Baseline Value Distribution Min Variation Max Variation
      Bottom Angle Path 84.0 deg Triangular -3.5% +3.5%
      Deflector Angle 97.0 deg
      Deflector Horizontal Distance 0.1 m
      Deflector Radius 0.31 m
      Deflector Translation_X -1.0 m
      Deflector Translation_Y -1.0 m
      Deflector Vertical Distance 3.2 m
      Top Angle Path 77 deg
    5. Click Close.
  6. Specify the responses:
    1. Select the Responses node and set Responses to Pressure Drop MA and Velocity Uniformity MA.
    2. Select the Responses > Pressure Drop MA node and set Surrogate to Surrogates Generation.Pressure Drop MA_Kriging.
    3. Select the Responses > Velocity Uniformity MA node and set the following properties:
      Node Property Setting
      Velocity Uniformity MA Surrogate Surrogates Generation.Velocity Uniformity MA_Kriging
      Is Constraint Activated
      Constraint Properties Type Minimum
      Minimum Constraint Minimum 0.87
  7. Right-click the Reliability node and select Run Study.
    The Output Table - Reliability - All tab opens showing you the state of each design, the input parameters, and the results. Despite the high number of designs to run, the study finishes fairly quickly due to the use of surrogates.