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Squeak and Rattle
Create and evaluate evaluation lines and optimize interfaces to eliminate squeak and rattle issues.
Technical Concepts
Technology and problem evaluation approaches used in SnRD.
Root Cause Analysis
SnRD Post-Processing proposes two modules: Modal Contribution and Modal Sensitivity.

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Squeak and Rattle
Create and evaluate evaluation lines and optimize interfaces to eliminate squeak and rattle issues.
- Technical Concepts
  Technology and problem evaluation approaches used in SnRD.
  - Rattle Evaluation
    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.
  - Squeak Evaluation
    Squeak evaluation is based on the contact plane relative displacement as per the E-Line method definition, in X and Y local Direction.
  - Root Cause Analysis
    SnRD Post-Processing proposes two modules: Modal Contribution and Modal Sensitivity.
  - Combined Loading
    SnRD solution analyzes squeak and rattles for static and dynamic load types. In the post-processing module, a combined loading module is available to study combination scenarios.
  - Optimization
    Once risk and issue areas are identified and their root cause (mode shapes and frequency), you can setup an optimization solver deck to get solution proposals. Problems are categorized as systematic issues and non-systematic issues.
  - Variabilities Analysis
    SnRD Post Stochastics and DOE module can be used to investigate hundreds of simulation results in a powerful way.
- Launch Squeak and Rattle Director
- Pre-Processing
  Explore the SnRD Pre-Processing user interface.
- Post Processing
  Launch and explore SnRD Post Processing.
- Ziegler PEM Material Database
  Use of Altair Ziegler SnRD Material Database.

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Root Cause Analysis

SnRD Post-Processing proposes two modules: Modal Contribution and Modal Sensitivity.

Modal Contribution

The E-Line method is a time domain analysis approach, using Modal Transient Analysis, also known as the Modal Superposition Method. This enables a transition to the frequency domain.

U (t) = \sum_{i = 1}^{N} m_{i} \times Ψ_{i} (t)

Where:

$U (t)$ is the time domain displacement.
$N$ is the number of modes extracted.
$m_{i}$ is the Modal displacement for a mode $i$ .
$Ψ_{i}$ is the Participation factor for mode $i$ .

With all the above responses available in the standard outputs from OptiStruct Analysis, the Relative Modal Contribution [%] values can be calculated. These will describe the participation of a mode or modes on a peak of the time domain response.

Figure 1.

Modal Sensitivity

Use modal sensitivity to live perform what-if studies by altering the time domain response of an E-Point or complete E-Line. This is achieved by decomposition of the Modal Superposition response, applying a factor (between 0 and 1) on selected modes, damping, and canceling or isolating them.

Figure 2.