# Rattle Evaluation

The rattle evaluation is based on the assessment of relative displacement between two parts along the defined E-Line. The relative displacement is compared to the Gap and Tolerance values defined during the pre-processing workflow.

The automatic assessment allows the understanding of the rattle phenomena using the following:
• Relative displacement magnitude and in local Z-direction
• Dynamic Tolerance is defined as: Gap [mm] - Tolerance [mm] - Relative Displacement in Z
In addition, SnRD proposes a unitless Contact Rattle Index (CRI) coupled to the material pair along the Rattle E-Line. Named as Contact Type, this criterion is based on the material stiffness values:
• Soft - foam, leather, rubber, etc... materials - default Youngs(E) Modulus < 500 MPa
• Medium - soft plastics material - 501 MPa < E-modulus < 10000 MPa
• Hard - hard plastics, metals, glass materials - E-modulus > 10000 MPa
Note: The range of Young Modulus is fully customizable in SnRD Post. This allows you to exclude from rattle evaluation interfaces where material like fabrics are applied in the real world, while not modeled in the FE model. The evaluation process based for the CRI is set as the following:
Evaluation based on CRI:
Contact Risk Index Matrix:

Issue and risk areas are then easily identified, guiding the analyst for deeper investigation of root cause and problem solving.