NVH Presentation

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“NVH ANALYSIS IN AUTOMOBILES”:

“NVH ANALYSIS IN AUTOMOBILES” Presented by Solase Rushikesh Mtech Automobile Engg.

NOISE:

NOISE Noise is a audible sound generated in vehicle or any other system including engine, driveline, tire contact patch and road surface, brakes, clutches, gearbox , cooling fan etc. It can be measured

VIBRATIONS:

VIBRATIONS They are very low frequency energy propagations through a medium They are produced in the driveline and The medium of vibration can be any part of a vehicle. They can be measured and controlled .

HARSHNESS:

HARSHNESS Harshness is a combination of NOISE and VIBRATIONS which creates an uncomfortable feeling in occupants of that vehicle. They just can be felt and can be “JURY” evaluated

WHAT IS NVH :

WHAT IS NVH Noise, vibration, and harshness (NVH) , also known as noise and vibration (N&V) , is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks.

NVH Types:

NVH Types Interior NVH deals with noise and vibration experienced by the occupants of the cabin, while Exterior NVH is largely concerned with the noise radiated by the vehicle, and includes drive-by noise testing

NVH SOURCES:

NVH SOURCES They including the engine, driveline, tire contact patch and road surface, brakes, wind. Noise from cooling fans, alternator, and other engine accessories is also fairly common

PowerPoint Presentation:

Transfer Path Analysis

Why NVH is necessary?:

Why NVH is necessary? Noise Pollution Customer Awareness Of Vehicle Ride Comfort Marketability Trend Towards Higher Power And Smaller Size Power trains. Sound Quality Design Optimization Consistency In Production

NVH Classification:

NVH Classification By Noise Type By Vehicle Systems Vehicle Components

By NOISE Type:

By NOISE Type Road NVH Wind Noise Powertrain /Driveline NVH Squeak /Rattle

By VEHICLE Systems:

By VEHICLE Systems Body NVH Chassis NVH

By VEHICLE Components :

By VEHICLE Components Climate Control System Wipers Seat Motors Switches

NVH Analysis:

NVH Analysis Noise contributions from various systems #Fan and Radiator Assembly –10% # Drive Line –14% # Engine -21% # Intake System-14% # Exhaust System –32% # Structural Components- 10% # Miscelleneous-3%

Actual Testing Of PASS BY NOISE of a VEHICLE :

Actual Testing Of PASS BY NOISE of a VEHICLE

Instruments Needed:

Instruments Needed Sensors * microphone * hydrophones * accelerometers Data Acquisition Devices * analog-to-digital converters (ADCs), * anti-aliasing filters * signal conditioning

ACOUSTICS :

ACOUSTICS Acoustics is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound (all mechanical waves in gases, liquids, and solids). The word "acoustic" is derived from the Greek word ακουστικός ( akoustikos ), meaning "of or for hearing, ready to hear"

Solutions For Improving Noise:

Solutions For Improving Noise R educing the source strength, as in making a noise source quieter with a muffler, or improving the balance of a rotating mechanism; Interrupting the noise or vibration path, with barriers A bsorption of the noise or vibration energy, as for example with foam noise absorbers

PowerPoint Presentation:

Acoustic treatments on car body

VIBRATIONS :

VIBRATIONS Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.

Types of vibration :

Types of vibration Free vibration Forced vibration

Vibration Characteristics :

Vibration Characteristics The main characteristics of vibrations are: Ride Comfort Shake Shimmy Brake Shudder

Ride Comfort:

Ride Comfort When un sprung components start to resonate with sprung components. Pitching Rolling Bouncing

Shake:

Shake Vibrations felt in the steering wheel, seat, or floor. Two types of shake are: Vertical Lateral Generally has a frequency between 10 to 30 Hz.

Possible Causes of a Shake:

Possible Causes of a Shake Roughness of the road Tire imbalance Non-uniform tires Bent or out or roundness of wheels Driveline Engine

Shimmy:

Shimmy Vibration that causes the steering wheel to oscillate. Typically has a frequency between 5 and 15 Hz. The two main types of shimmy are: Low speed shimmy High speed shimmy

Main Causes of a Shimmy:

Main Causes of a Shimmy Roughness of road Tire Imbalance Non-uniform tires Bent or out of roundness of the wheel

Brake Shudder:

Brake Shudder Causes the instrument panel, steering wheel, and sometimes the entire body to vibrate vertically and back and forth. Peaks at 40 to 50 mph and has a frequency of 5 to 30 Hz. The major sources of shudder are: Brake rotor run out Non-uniform thickness

PowerPoint Presentation:

Certain operating conditions can greatly affect these vibrations: Extended periods where the vehicle is not in operation. Brake disc surface irregularities caused by foreign substances (saltwater, antifreeze, etc) Deformation of brake drum cause by poor installation.

Harshness:

Harshness Many customers use the word “harshness” to describe ride comfort concerns. Occurs when a vehicle vibrates when moving across road joints, projections, depressions or stepped paved road surfaces. Typically has a vibration of 30 to 60 Hz.

Vibration testing :

Vibration testing Vibration testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker

Vibration Isolation:

Vibration Isolation Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations # Passive isolation #Active isolation # Subframe isolation

Vehicle Ride Comfort :

Vehicle Ride Comfort Ride comfort in a vehicle is a subjective perception normally Associated with level of comfort experienced during traveling in a vehicle. Perceived ride is cumulative effect of many factors In the vibration spectrum, Ride - 0 -25 Hz Noise - 25Hz - 20KHz Ride is a tactile and visual vibrations .

Applications :

Applications NVH test equipment are used for various applications such as: Engine noise vibration testing Acoustic performance testing Sound power testing Pass by noise testing Telephone testing Environmental noise measurements and noise field mapping Structural dynamics and vibration testing Occupational health and safety

PowerPoint Presentation:

VEHICLE NVH ASSESSMENT Benchmarking & Target setting Pass-by Noise Measurement Interior NVH Assessment Subjective Evaluation Noise & Vibration Mapping Identification of Prominent Noise Sources Effectiveness of Engine & Body Mounts Effectiveness of Silencer & Intake system Effectiveness of Acoustic Treatment Set Vehicle Targets based on data available with ARAI or repeat exercises on identified Benchmark Vehicles Set Targets for Noise Reduction on Individual Systems

Videos:

Videos

ADVANTAGES:

ADVANTAGES Most comfortable ride Least fatigue More workability of the occupants

Some common examples where NVH Analysis is applied. :

Some common examples where NVH Analysis is applied . VOLVO Busses & Trucks

PowerPoint Presentation:

Mahindra SCORPIO

Tata SAFARI:

Tata SAFARI

Conclusions:

Conclusions The need to improve product quality and differentiate from the competition, concerns about human health and safety combined with stringent regulations, create a viable market for NVH .

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