Variability Study

Setup a Variability Study to analyze and examine the squeak and rattle risks caused by manufacturing variations

The manufacturing of a parts is often related to variations of tolerances and quality of materials. In addition, the assembly process adds a set of variations on dimensions and stiffness of connections, resulting in a unique product at each build. These two major processes affect the product final quality and therefore its performance.

Squeak and Rattle are phenomena that are tightly related to the quality of the built parts, and performance can vary through the population of produced products.

By performing a variability study in SnRD the risk and effects of manufacturing problems can be studied and analyzed.

In SnRD, the following model parameters can be used as design variables* in the study:
  • Component Thickness
  • Material Characteristics
    • Youngs' Modulus
    • Density
  • Attachment Stiffness
  • Damping
Note: *A design variable is a system parameter that influences the system performance in the chosen output response. Typical design variables may be a part's thickness or material property. Ranges, with lower and upper bounds, are specified and the variable's value will vary within the study.

In order to setup a Variability Study, you should first setup a transient loadcase in the model.

Variability Study Setup

  1. From the Setup group, select Variability Study.
    Figure 1.
    A guide bar will appear.
    Note: If a transient loadcase is not detected in the model, a user message will be displayed.
    Figure 2.
  2. Select what type of model parameter to include in variation study. Available parameters are-
    • Material Parameters
    • Attachment Stiffness
    • Thickness
    • Damping
  3. Select properties/curves/material in the graphics area or by using the advanced selection dialog.
  4. In the microdialog specify the lower and upper bounds for the variation.
    Figure 3.
  5. Optional: Click on to update name.
  6. Click .
    This will create the variation study for the selected parameter.

Review Variation Study

  1. From Setup group, select Variability Study > Review Variations.
    Figure 4.
    Review Table will appear.
    Figure 5.
  2. Check the boxes against required variation study under Export.
  3. Optional: Click Delete to delete a study.
Refer Export Variability Study know more about exporting the variation study.

Variability Study Options

Study Parameters
Material Parameters
Material Parameters are directly affected by the manufacturing process, especially in injection molding for plastic part. In the industry, variations in material properties of +/-30% are observed.
You can define study parameters for-
Figure 6.
E
Youngs Modulus
RHO
Density
Attachment Stiffness
Soft connections, such as clips or snaps, are recommended to be modeled with spring elements allowing to capture fixed and released degrees of freedom. Also, fixation stiffness can be applied to capture the local and relative stiffnesses, main contributors to S&R issues.
You can define attachment stiffnesses-
Thickness
Manufacturing process have direct impact of finished parts, affecting the global thickness distribution. Hence, local stiffness can be influenced with those variation.
Damping
S&R are directly related to amplitude of relative displacement. One of the affecting parameters, and often approximated, is the system modal damping. Applying constant or varying model damping through the frequency range is enabled by this capability.
Study name
You can define the study name by clicking to open the additional option.
Figure 7.
Variation Values
- minimum variability value
- maximum variability value