Smart materials for vibration reduction

Smart Materials For Vibration Reduction

A seminar Report

Submitted by

DIANA ALKEFLAWI IN

MECHANICAL ENGINEERING

AT

ERCIYES UNIVERSITY

MECHANICAL ENGINEERING DEPARTMENTKAYSERI17/12/2015

Abstract

For active noise and vibration reduction tasks in smart-structures technology piezoelectric ceramics are first choice. They generate large forces, have fast response time, are commercially available as fibres, patches and stacks and allow integration into structural components.

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The purpose of this research is compare the vibration test results for a plate with and without smart damping. Also discusses the benefits of smart materials when added to existing damping materials in terms of vibration.

TABLE OF CONTENTS

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Page CHAPTER 1 : 1 . INTRODUCTION …………….……..…………….……….. …1

1.1 What is Smart Materials ?..............................................................................11.2 Traditional vs. Smart structure…………………..…………………………22.3 Classification of Smart Materials…………..…………………………… ..31.4 Smart Composites…………………………………………….…………….73.5 Smart Structures………………………………………………………….…81.6 Importance For Smart Structures…………………………..……………….104.7 Smart System For Engineering Applications……………….....…..………..111.8 Smart Structure Applications …..……………………………………..……12

CHAPTER 2 : 2.1 What is vibration?........................................................................................17

2.2 Terms Definitions…………………………………………….. ……..18 2.2.1 Shunt Circuit Design……………...………………………….....…18 2.2.2 Shunt Tuning…………….……………………………………...…19 2.2.3 Damped vs. Undamped Vibration…………………………………20 2.3 Vibration Benefits Of Smart Damping For Undamed Plates…………..…22 2.4 Benefits Of Smart Damping For Damped Structures………….……..…..25 2.5 Summary ………………………………………………………..……….34REFERENCES……………………… .………………………………………………35

CHAPTER ONE

1 .INTRODUCTION TO SMART MATERIALS1.1 WHAT IS SMART MATERIALS ?

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-Smart or intelligent materials are materials that have the

intrinsic and extrinsic capabilities, first, to respond to stimuli

and environmental changes, second, to activate their functions

according to these changes.*Stimulus —stress, strain, light, electric field, temperature ,

pressure,moisture, magnatic field.*Response —motion or change in optical properties,modulus,

surface tension, piezoelectricity etc.

1.2 Traditional vs . Smart structure

Traditional structures

•Designed for certain performance requirements eg. load, speed ,life span.

•Unable to modify its specifications if there is a change of environment.

Smart Structures

•Can accommodate unpredictable environments.

•Can meet exacting performance requirement.

•Offer more efficient solutions for a wide range of applications.

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1.3 Classification of Smart Materials

Actively Smart

They possess the capacity to modify their geometric or material

properties under the application of electric, thermal or magnetic

fields, thereby acquiring an inherent capacity to transduce energy.Piezoelectric

Magnetostrictive

Shape memory alloys

Electro-Rheological fluid, etc.

They can be used as force transducers and actuators.

3

Passively Smart

Those smart materials that are not active are called passively

smart materials. Although smart, they lack the inherent capability

to transduce energy.

Optic fibres

These materials can act as sensors but not as actuators or

transducers.

4

Fig: Common smart materials and associated stimulus response5

Type of SMART Material

Input Output

Piezoelectric Deformation Potential Difference

Electrostrictive Potential Difference Deformation

Magnetostrictive Magnetic Field Deformation

Thermoelectric Temperature Potential Difference

Shape Memory Alloys

Temperature Deformation

Photochromic Radiation Color Change

Thermochromics Temperature Color Change

6

1.4 Smart Composites

Combining two or more single smart materials to utilize the best

properties of their individual constituents is the objective of any

new smart composites.

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A smart structure is a system that incorporates particular functions of sensing and actuation to perform smart actions in an ingenious way.

The basic five components of a smart structure are Data Acquisition (tactile sensing): the aim of this component is to collect

the required raw data needed for an appropriate sensing and monitoring of the structure .

Data Transmission (sensory nerves): the purpose of this part is to forward the raw data to the local and/or central command and control units.

1.5 Smart Structures

Command and Control Unit (brain): the role of this unit is to manage and control the whole system by analyzing the data, reaching the appropriate conclusion, and determining the actions required.Data Instructions (motor nerves): the function of this part is to transmit the decisions and the associated instructions back to the members of the structure.Action Devices (muscles): the purpose of this part is to take action by starting the controlling devices/ units.

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1.6 Importance for Smart Structures

-Light weight -Warnings on problems that can encounter

-Preventative maintenance -Performance optimization

-Improved life cycle

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General Requirements and Expectations1 .High degree of reliability, efficiency and sustainability not only of the

structure but also of the whole system.2 .High security of the infrastructures particularly when subjected to

extreme and unconventional conditions.3 .Full integration of all the functions of the system.

4 .Continuous health and integrity monitoring.5 .Damage detection and self-recovery.

6 .Intelligent operational management system.Smart Technologies Prospects

1 .New sensing materials and devices.2 .New actuation materials and devices.

3 .New control devices and techniques.4 .Self-detection, self-diagnostic, self-corrective and self-controlled

functions of smart materials/systems.

1.7 SMART SYSTEM FOR ENGINEERING APPLICATIONS

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The scope of application of smart material includes solving engineering problems for creation of new products with unfeasible efficiency and

provides an opportunity that generate revenue .

1.8 Smart Structure Applications

1 -Aerospace - Damage detection

-Vibration control -Shape control

- Adaptive structures

2-Defence -Firing accuracy of weapons

-Vibration and noise reduction in submarines -Smart missiles use smart fins which can warp to appropriate

shapes

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3-Automotive -Passenger comfort (noise control in cabin)

-Vibration control (active engine mounts) -Health monitoring (smart sensors)

4-Industrial -Manufacturing (machine tool chatter

control) -Air conditioning and ventilation (noise

control) -Mining machinery (vibration control)

5-Medical Smart sensors Micro robotics Surgical tools

6-Civil Bridges Earthquake protection

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-Vibration reduction in sporting goods : a new generation of tennis rackets,

golf clubs, baseball bats and ski boards have been introduced to reduce

the vibration in these sporting goods, increasing the user’s comfort and

reducing injuries.

-Smart clothes

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Examples

Noise reduction in vehicles : filaments of piezoelectric

ceramic fibres are used to counter noise in vehicles,

neutralize shaking in helicopter rotor blades, or nullify or at

least decrease vibrations in air conditioner fans and auto-

mobile dashboards.

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CHAPTER TWO

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2.1 WHAT IS VIBRATION?

Scientific DefinitionAny motion that repeats itself after an internal of time.

Engineering DefinitionDeals with the relationship between forces and oscillatory motion of Mechanical systems.

A piezoelectric disk generates a voltage when deformed (change in

shape is greatly exaggerated

Shunt Circuit Design

The smart damping technique chosen for this study involved attaching piezoceramicdevices that are shunted with passive electrical circuits. When the panel vibrates, asillustrated in Figure below, the mechanical energy strains the piezoelectric material and thereby generates electrical energy .The shunted electrical impedance then dissipates this electrical energy. The components of these shunt circuits (resistors ,capacitors, and inductors) are chosen to produce an effective mechanical impedance at desired levels and frequencies.

2.2 Terms Definitions

Shunt Tuning Damped vs. Undamped Vibration

2.2.1 Shunt Circuit Design

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T- Stress by Plate on PZT Vi- PZT VoltageI - Circuit Current Rs- Shunt Resistance Ls- Shunt Inductance Zs-Equivalent Shunt Impedance

I

Vi

Shunting of Piezoelectric Materials

2.2.2 Shunt Tuning

Tuning the PZT resonant shunt circuits :

The first step is to determine the electrical resonant frequencies required to dissipate the mechanical energy.

The second step is to calculate the initial values for the variable resistors in the shunt circuit.

The final step is to fine-tune the resistors with testing in order to achieve optimal damping.

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Damped and undamped vibration refer to two different types of vibrations. The main difference between them is that undamped vibration refer to vibrations where energy of the vibrating object does not get dissipated to surroundings over time, whereas damped vibration refers to vibrations where the vibrating object loses its energy to the surroundings.

2.2.3 Damped vs. Undamped Vibration

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UNSHUNTED UNDAMPED

W/PZTs W/OPZTs

UNDAMPED TEST PLATES

SHUNTED DAMPED SHUNTED

DAMPED UNSHUNTED

W/ PZTs W/O PZTs

DAMPED

TEST PLATES

DAMPED TEST PLATE

Test Plate Configurations Used to Evaluate the Benefits of Smart Damping

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2.3 Vibration Benefits of Smart Damping

for Undamped PlatesOnce the smart damping plate was constructed, initial tests were performed on the shunted and unshunted plates. The shunt circuits were tuned to the resonant frequencies between 50 and 450 Hz for the unshunted plate. Figure (*1*) illustrates the effect of the tuned shunt circuits on the plate vibration response. Peaks 3, 4, and 5 were the most significantly reduced for the shunted plate.

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Frequency Response Functions

1

3 5

4

Unshunted Shunted

Pla

te A

ccel

/Fra

me

Acc

el, g

s/gs

Fig (*1*)

50 100 150 200 250 300 350 400 450

-110

010

110

210

23

(HZ)

Unshunted and Shunted Plate Vibration Response

13 5

4

Pla

te A

ccel

/Fra

me

Acc

el, g

s/gs

Fig (*2*)

(HZ)-110

010

110

210

50 100 150 200 250 300 350 400 450

Effect of Adding Smart Material to an Undamped Plate

Frequency Response Functions

UnshuntedUndamped

Peak Undamped (g/g)

Shunted PZT (g/g)

Reduction (%)

1) 101 Hz( 57.79 31.84 56.13) 147 Hz( 47.74 7.53 84.64) 235 Hz( 11.28 4.05 64.15) 245 Hz( 47.97 3.87 91.9

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The goal of the testing was to determine the total vibration reduction achieved by the application of smart damping. Table above presents the decreases in the peak accelerations that were obtained using the tuned shunts. The results indicate that the smart damping significantly reduced the four resonant peak vibrations, with the largest reductions

achieved for peaks 3 and 5 .

Table.1. Effect of Smart Damping on Peak Vibrations

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2.4 Benefits of Smart Damping for Damped Structures

This section investigates the added benefits of applying smart damping when used with conventional passive damping materials. The effect of adding smart

damping materials to a plate damped with: ·unbacked carpet,

·shoddy and unbacked carpet, and ·shoddy and 0.3 PSF backed carpet

25Figure (*3*) Passive Treatments Used with Smart Damping Materials

500mm

Shoddy Unbacked Carpet

0.3 PSFBacked Carpet

400 mm Fig(*3*)

The evaluation was based on comparing the vibrationmeasurements with and without smart damping for each of the above treatments. These treatments, as shown in Figure (*3*) were cut into 400 mm x 500 mm samples that were placed over the test plates. Each material is evaluated by measuring the plate vibrations similar to the undamped cases.

Shoddy is a foam pad made of interwoven fabric scraps that is placed under the carpeting in vehicles. The backed carpet has a layer of rubber melted onto the carpet toadd damping with mass loading. The grade of carpet is measured as pounds per square foot or PSF.

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As was expected, the damping treatments altered the frequency response of the plate which required the shunts to be retuned for each damping case. Once the shunt circuits were optimized, the three different treatments were tested for both the shunted plate and the undamped plate.

The augmenting vibration benefits of PZTs are presented first followed by the acoustic benefits.

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Vibration Benefits of Adding Smart Damping to Damped Structures

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It is evident in Figures below that the smart damping has the most effect on accelerations above 125 Hz. It is also noted that the PZTs add less additional damping as the amount of treatment increases and the vibrations decrease.

Another convenient method to assess the benefits of smart damping materials is to evaluate their broadband performance using a third-octave band analysis. For the vibration data, 1/3-octave values were determined for each center frequency.

Undamped

Decrease in Acceleration Using Smart Damping

Frequency, 1/3 Octave Bands

Dec

reas

e in

Acc

eler

atio

n, (d

B)

-8

-6

-4-202468

1012

63 80 100 125 200 250 315

No Treatment

160

U nbacked Carpet


63 80 100 125 160 200 250 315


-6

-4

-2

02

4

6

8

10

Dec

reas

e in

Acc

eler

atio

n, (d

B)

D e c r e a se in V i b ra tio n L e v e l s U sin g S m a r t D a m p i n g

F r e q u e n cy, ( 1 /3 O c t ave B a n d s )

Unbacked carpet

Shodd y + Unbacked Carpet



Dec

reas

e in

Acc

eler

atio

n, (d

B)

Shoddy + Unbacked Carpet

-4

-2

0

2

4

63 80 100 125 160 200 250 315

-3

-1

1

3

Shodd y + 0 .3PSF

Carpet


63 80 100 125 160 200 250 315


Dec

reas

e in

Acc

eler

atio

n, (d

B)

-3-1

-4

-2

0

2

F r e q u e n cy, 1 /3 O c t ave B a n d s

Shoddy + 0.3 PSF Carpet

-1

3

1

63 80 100 125 160 200 250 315

UNDAMPED PLATE 0.5 -1 8 -6 10 3 10 12

UNBACKED PLATE -4 -1 -2 -6 5 1.8 5 8

SHODDY+ UNBACKED

PLATE-2 -0.1 -3 0.1 1.2 1.6 1 4

SHODDY + 0.3 PSF PLATE

-1 1.5 -4 2 0.9 1 0.5 1

TYPES OF PLATES

Hz

The benefits of smart damping materials, specifically piezoceramics with shunt circuits, in reducing vibrations were addressed. Tests were conducted on a test plate with shunted PZTs. A comparison of the results with an undamped plate showed that the smart damping materials can significantly lower both the plate vibration for both narrowband and broadband frequencies .

2.5 Summary

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Akhras, G., “Advanced Composites for Smart Structures”, Proceedings, ICCM-12, 12th International Conference on Composite Materials, Paris5-9.

INTRODUCTION, CLASSIFICATION AND APPLICATIONS OF SMART MATERIALS: AN OVERVIEW American Journal of Applied Sciences 10 (8): 876-880, 2013 Susmita Kamila

An Experimental Evaluation of the Application of Smart Damping Materials for Reducing Structural Noise and Vibrations Kristina M. Jeric

International Journal of Mechanical and Industrial Engineering (IJMIE) ISSN No. 2231-6477, Vol-3, Iss-1, 2013

References

Ref. H.W. Hagood, and A von Flotow, “ Damping of Structural Vibrations with Piezoelectric Materials and Passive Electrical Networks,” Journal of Sound and Vibration

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Smart materials for active noise and vibration reductionH. P. Monner German Aerospace Center (DLR), Institute of Composite Structures and Adaptive Systems Lilienthalplatz 7, D-38108 Brunswick, Germany

Overview of Smart Materials Bishakh Bhattacharya & Nachiketa TiwariDepartment of Mechanical Engineering Indian Institute of Technology, Kanpur

SMART MATERIALS AND SMART SYSTEMS FOR THE FUTURE by Georges Akhras Canadian Military Journal Autumn 2000

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