Squeak and Rattle Analysis

3 Squeak and Rattle Noise

Squeak • RD (relative displacement): stick-slip phenomenon • Energy release when µstatic > µkinetic • 200 Hz – 10 kHz • Shear move of 1mm enough to create squeak

Rattle

•RD: impact-induced •Loose or overly flexible elements or insufficient attachment/structural strength

•200 Hz – 2 kHz

4 Squeak and Rattle Noise in Automobile

• IP (Instrument Panel), seats and doors responsible for over 50% of the total S&R problems

• Squeak & rattle perceived as general lack of quality in the product

• Tradition “find-and-fix” approach expensive in product costs and time consuming

5 SnR (Squeak and Rattle) Director

SnRD (Squeak and Rattle Director) – Overview

• Integrated module in HyperWorks, providing a semi-automated process centric approach to streamline the SnR analysis

• Based on Industry Best Practice: SAE 2010-01-1423 and SAE 2012-01-1553

• Identify the risk areas for SnR early during the design phase

• Reduce the amount of physical testing to be performed

SnRD (Squeak and Rattle Director) – Set of compressive automations

6 SnRD Methodology SnRD – Simulation process

2. Calculation - Input signal in time domain - Displacements of master/slave

components in time domain

3. Post-processing - Relative displacements - Dynamic tolerance - Root Cause Analysis

E-line (Evaluation line) Spring element with local coordinate system Null stiffness (Kx = Ky = Kz = 0 N) Gap & tolerance (Dimensional Technical Specification) used in post-processing Relative displacement evaluated for normal direction from master surface

Allows different configurations to be modelled regardless the quality of the mesh

1. Pre-processing - Definition of interfaces - DTS input

7 SnRD Methodology SnRD – Simulation process

1. Pre-processing - Definition of interfaces - DTS input

2. Calculation - Input signal in time domain - Displacements of master/slave

components in time domain

3. Post-processing - Relative displacements - Dynamic tolerance - Root Cause Analysis

8 SnRD Methodology SnRD – Simulation process

1. Pre-processing - Definition of interfaces - DTS input

2. Calculation - Input signal in time domain - Displacements of master/slave

components in time domain

3. Post-processing - Relative displacements - Dynamic tolerance - Root Cause Analysis

How to define a Rattle?

• Statistical evaluation: max value in the relative displacement NOT representative of the entire response

How to estimate a risk of rattle ?

• Dynamic tolerance = Gap – Tolerance – RDz

• Rattle noise occurs when Dynamic tolerance < 0

9 SnRD Analysis

X-axis

Y-axis

Z-axis

Pre-processing

Calculation

Post-processing

10 SnRD Demo Analysis

11 SnRD Demo Analysis

12 SnRD Demo Analysis

13 SnRD Demo Analysis

Mode 10 – F = 17,44 Hz

14 SnRD Demo Analysis

Mode 10 – F = 17,44 Hz

15 SnRD Analysis

Simulation driven design process • Virtual test rig for risk detection on standard NVH model • Various loading conditions • Root cause analysis • Implementation in early design phase

Industrial perspective

• Different industrial applications