NVH TECHNOLOGY IN THE BMW 1 SERIES

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Logan Osborne
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1 NVH TECHNOLOGY IN THE BMW 1 SERIES (Presented by) A. Fleszar LMS Americas J. Florentin, F. Durieux LMS International T. Yamamoto, Y. Kuriyama Nippon Steel Corporation

2 CONTENTS Introduction Hybrid Interior Noise Synthesis Approach Measurements on Vehicle Panel CAE Model Creation Panel Optimization for NVH and Crash Conclusion

3 Introduction ULSAB 25% Lighter CO2 (g/km) Vehicle Mass (kg) Lighter vehicles for reduced CO2 emission Preservation of safety and comfort ULSAB-AVC CO 2 <110g/km

4 Introduction Objective: Lightweight steel solution for noise performance Panel investigation using Test and CAE Hybrid Approach Candidate vehicle / panel Compact and comfortable vehicle Firewall on direct engine noise path Firewall of BMW Series 1

Approach Candidate vehicle / panel Compact and comfortable

5 PROJECT CONTENT Step 1: Vehicle measurement Step 2: Panel measurement Step 3: Panel CAE model Step 4: Panel modification Step 5: Modified panel in vehicle Project Framework Engine Noise Structure Borne Hz

Panel modification Step 5: Modified panel in vehicle

6 INTERIOR NOISE SYNTHESIS Original Noise Improvement Evaluation In full Vehicle Design Modification

7 MEASUREMENTS On Vehicle Acoustic Source Quantification Measure firewall and cabin response to structural excitation Isolate firewall contribution Estimate other panel contributions Acoustic characterization of passenger cabin On Panel Trim package evaluation Structure characterization FE model validation

Estimate other panel contributions Acoustic characterization of passenger

8 ACOUSTIC SOURCE QUANTIFICATION Roof Windshield Firewall Floor Windshield Firewall seen from engine compartment Wheel housing Right window

9 ACOUSTIC SOURCE QUANTIFICATION Firewall and floor are the dominant steel structures in the low frequency range db Firewall (CAE prediction) Floor (ASQ estimation) Hz Hz Hz Floor dominates the higher frequencies db Hz Hz Firewall Floor Roof Windshield Side Windows

10 Acoustic-acoustic FRF measurements Measure cabin dimensions ACOUSTIC CHARACTERIZATION OF PASSENGER COMPARTMENT Microphones Source Microphones on panel Acoustic source Build and validate acoustic FE model

COMPARTMENT Microphones Source Microphones on

11 ACOUSTIC CHARACTERIZATION OF PASSENGER COMPARTMENT Modes of firewall in range of interest 102 Hz 141 Hz 144 Hz Mode 1 58 Hz

12 STRUCTURAL CHARACTERIZATION Firewall Cowltop Transverse beam Roving hammer measurements: Components Assembly Steel Components Trim Package Components purchased from BMW dealer

13 PANEL CAE MODELING Scanned firewall components Passenger cabin FEM Firewall is spot-welded structure with full vehicle boundary conditions + Trim Firewall structure coupled with acoustic model

structure with full vehicle boundary conditions

14 PANEL CAE Structural response shows the model is successful for 40 Hz 300 Hz Acceleration on Firewall Central Location Measurements CAE model Vibro-acoustic CAE model catches the mid-range firewall contribution (80 Hz 200 Hz) Firewall Noise Contribution At Driver s Right Ear Test is under predicting due to small number of measurement locations on firewall TEST ASQ (limited set of points) CAE (full set of points)

contribution (80 Hz 200 Hz) Firewall Noise Contribution At Driver s Right Ear Test is under predicting

15 IDENTIFICATION OF DESIGN IMPROVEMENTS Sensitivity of acoustic model Use CAE model to identify structural weak points: Lower firewall Firewall region behind the beam Mode Contribution Analysis 102 Hz 141 Hz 144 Hz Element contribution analysis 130 Hz 118 Hz 130 Hz 118 Hz 144 Hz 144 Hz

Firewall region behind the beam Mode Contribution Analysis 102 Hz 141

16 PANEL MODIFICATIONS FOR NOISE REDUCTION 40+ modifications investigated Optimized design Modified transverse beam with new M-shape, reduced thickness, holes and Tailored Welded Blank 1.9mm Original:1.7mm Front 1.5mm Tailored Blank Back Beads 0.7mm (same as original)

M-shape, reduced thickness, holes and Tailored Welded Blank 1.

17 CRASHWORTHINESS Static analyses 2 load cases: front and side Original design Final design 5000N 5000N

18 MODIFIED PANEL INFLUENCE ON OVERALL VEHICLE NOISE db db Firewall contribution to sound Full vehicle sound pressure

19 PERFORMANCE IMPROVEMENT SUMMARY Original BMW1 Firewall Advanced Steel Solution TWB + Beads + M-Shaped Beam + Holes 0.7mm 0.7mm 1.7mm 1.5mm 1.9mm Panel + Beam 8.43 kg Damping sheets 0.40 kg Panel + Beam 8.19 kg Damping sheets 0 kg Weight reduction 0.64 kg (5.1%) Noise level 0.90 db (10 400Hz)

9mm Panel + Beam 8.43 kg Damping sheets 0.40 kg Panel + Beam 8.

20 CONCLUSIONS Hybrid Interior Noise Synthesis Efficient, simple and flexible Potential to be used at early design stages Short calculation time, allows a large number of iterations and indepth sensitivity analysis Elaborate steel designs are successful at Achieving better noise performance While improving the mass Not compromising crashworthiness 1 db improvement on firewall contribution of high end vehicle For even larger improvements Address NVH earlier in the design process

are successful at Achieving better noise performance While improving the mass Not compromising crashworthiness 1 db

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