1 / 38

NVH Category

NVH Category. NVH Characteristic Frequency (Hz) Steady State Frequency Response Ride < 5 Shake 5 - 40 Boom 20 - 100 Moan 100 - 150 Structural Borne Noise 150 – 500 Air Borne Noise > 500 Transient Response Harshness 20 - 100. Control by Damping. Control by Dynamic

torn
Download Presentation

NVH Category

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NVH Category NVH Characteristic Frequency (Hz) Steady State Frequency Response • Ride < 5 • Shake 5 - 40 • Boom 20 - 100 • Moan 100 - 150 • Structural Borne Noise 150 – 500 • Air Borne Noise > 500 Transient Response • Harshness 20 - 100

  2. Control by Damping Control by Dynamic Stiffness Control by Mass Isolation Region fn * fn Single Degree of Freedom

  3. Dynamic Stiffness Dynamic Stiffness: (K - m ω2) – j C ω K* = ---------------------------------- (K - m ω2)2 + (C ω)2 ω = 2* π*f f is the frequency Mass M Stiffness K Damping C

  4. Pure Tone • Sound at a single frequency • Sound Pressure • Objective measurement • dB • Logarithmic of sound pressure • dBA • A-Weighted to adjust for ear sensitivity

  5. Human Sensitivity • More constant across frequency range with velocity • Hearing range 20 – 2000 Hz • Depends on overall level • Sound at one frequency may mask by other frequencies • Depends on age, sex and other factors

  6. Acceleration SR = 5 SR = 6 Frequency Tactile ResponseSubjective-Objective

  7. Velocity SR = 5 SR = 6 Frequency Tactile ResponseSubjective-Objective (2)

  8. Sound Pressure Level and A Weighting

  9. NVH Classification • Operating Condition • Idle, Low Speed, Cruising, POT, WOT • Subjective Evaluation • Shake, Boom, Noise, Harshness • Objective Measurement • Sound Pressure, Acceleration • Frequency Range • Source • Powertrain, Road, Exhaust

  10. NVH Subjective Rating Most Targets No Sale

  11. NVH Objectives • Assess vehicle responses relative to design targets: • Tactile responses • Seat track • Steering column • Toe pan • Acoustic responses • Driver’s ear • Front Passenger’s ear • Rear passenger’s ear

  12. Shake • 5 – 40 Hz • Idle Shake • Isolated Road Shake • Rough Road Shake • Smooth Road Shake • Wheel/Tire Imbalance • Tire Force Variation

  13. Design For Shake • Body vertical, lateral bending and torsion modes • Front end bending and torsion modes • Front floor modes • Steering column modes • Seat modes • Avoid stickiness of the shock and CV joints that causes high force input and resonance in smooth road shake

  14. Design For Shake (2) • Mode separation and mode shape management of engine bounce, roll, pitch and yaw rigid body modes

  15. Boom • 20 - 100 Hz • Idle Boom • Isolated Road Boom • Rough Road Boom

  16. Body Design for Boom • 1st and 2nd fore-aft acoustic modes • Body 1st and 2nd order vertical bending • Front floor vertical bending • Dash panel fore-aft bending • Quarter panel bending • Fuel tank bounce • Spare tire tub bounce • Decklid, liftgate or lower back panel pumping

  17. Structural Borne Noise • 100 - 500 Hz • Powertrain Noise • Rough Road Noise • Gear Whine

  18. Design For Noise • Most of the vibration energy imparted to the vehicle is below 150 Hz. • Below 150 Hz: • Body structure is important for controlling noise and vibration • Lack of structure usually results in costly design and tooling changes • Above 150 Hz: • Can be resolved with relatively simple structure modifications, such as bead patterns, or damping treatments.

  19. Design For Noise (2) • Powertrain Bending Isolation • Powertrain Bracket Isolation

  20. Modal Chart CHASSIS/POWERTRAIN MODES Suspension Hop and Tramp Modes Ride Modes Suspension Longitudinal Modes Powertrain Modes Exhaust Modes 0 5 10 15 20 25 30 35 40 45 50 Hz BODY/ACOUSTIC MODES Body First Torsion (25Hz) Steering Column First Vertical Bending (29Hz) Body First Bending (22Hz) First F/A Acoustic Modes (48Hz) 0 5 10 15 20 25 30 35 40 45 50 Hz EXCITATION SOURCES Inherent Excitations (General Road Spectrum, Reciprocating Unbalance, Gas Torque, etc.) Process Variation Excitations (Engine, Driveline, Accessory, Wheel/Tire Unbalances) V8 Idle (500-550RPM) Hot Cold First Order Wheel/Tire Unbalance (5-75MPH) 0 5 10 15 20 25 30 35 40 45 50 Hz

  21. Body-in-White Targets • Static Stiffness • Bending • Torsion • Normal Modes • Vertical bending • Torsion • Lateral bending

  22. Trimmed Body Targets • Normal Modes • Vertical bending • Torsion • Lateral bending • Front end bending • Front end torsion

  23. Instrument Panel/Column Targets • Normal Modes • Vertical bending • Lateral bending

  24. Seat Targets • Normal Modes • On Bedplate • Fore aft • Lateral • In Vehicle • Fore aft • Lateral • Different row may have different target

  25. Idle Load

  26. Pbore mrecip arecip  h L   r Pcrank Idle Torque

  27. Pbore mrecip arecip  h L   r Pcrank Piston Displacement

  28. Pbore mrecip recip  h L   r Pcrank Trigonometric Derivatives

  29. Pbore mrecip arecip  h L   r Pcrank Piston Velocity

  30. Pbore mrecip arecip  h L   r Pcrank Piston Acceleration

  31. Smooth Road Shake

  32. Wheel/Tire Imbalance Definition • Simulation • Shake caused by the unbalanced inertia forces from the high speed rotation of the unbalanced wheel in vehicle cruising • Load • 1.0 oz-inch (Sensitivity) unbalanced force at the spindles • Both vertical and fore-aft loads with vertical load trailing fore-aft load by 90 degrees • Applications • Front wheel in-phase, Front wheel out-of-phase, Rear wheel in-phase and Rear wheel out-of-phase

  33. Wheel/Tire Imbalance Calculation • F = mr2 • F is imbalance Force (N) • m is imbalance mass (Mg) • r is imbalance radius (mm) •  is rotation speed (rad/sec) • F = 1.0 oz-in = 1.0 * 28.3 * 10-6 (Mg/oz) * 25.4 (mm/inch) * 4 * 2 * f2 = 0.0284 * f2 (N) • f is frequency (cycles/sec)

  34. Wheel/Tire ImbalanceSpeed Map • The wheel/tire speed map (frequency v.s. vehicle speed) is dependent on the wheel/tire size, the wheel/tire stiffness and the payload • V = 2 * π * Tire Effective Radius * Frequency • However, the Frequency/Vehicle Speed(MPH) is typically around 0.2 • Based on the above assumption, the frequency range of interest from 25 MPH to 125 MPH is • 5 Hz to 25 Hz

  35. Tire Force Variation Definition • Simulation • Shake caused by the variation of the radial stiffness of the tires • Load • 1.0 lbf (Sensitivity) variation force at the spindles • Vertical load only • Applications • Front wheel in-phase, Front wheel out-of-phase, Rear wheel in-phase and Rear wheel out-of-phase

  36. Tire Force VariationSpeed Map • The wheel/tire speed map (frequency v.s. vehicle speed) is dependent on the wheel/tire size, the wheel/tire stiffness and the payload • V = 2 * π * Tire Effective Radius * Frequency • However, the Frequency/Vehicle Speed(MPH) is typically around 0.2 • Based on the above assumption, the frequency ranges of interest from 25 MPH to 125 MPH are • First Order : 5 Hz to 25 Hz • Second Order : 10 Hz to 50 Hz

  37. Rough Road Noise

  38. Spatial PSD Road Profile • Spatial Frequency ( Cycles / mm) • Wave number • 1 / wavelength • PSD Amplitude (mm^2 / (cycles / mm)) • Power Regression Analysis (Y = 1.7872 * X-0.6729)

More Related