Title:

The Application of a Piezoelectric Actuator for Forming Surface Micro-Geometries (SMG’s).

By: Baharozan Mohid

Supervisor: Prof Raj Balendra

Introduction

Piezoelectric actuator was used for the construction of the tool-system in the creation of surface micro-geometries (smg’s) with a depth of 1 to 15 microns gives a promising results.

To produce such accurate smg’s, very accurate displacement and consistent performance of the piezoelectric actuator is require. Therefore, loss of performance after long-term operation should be taken into account.

Nevertheless

In the recent research

2. Conduct performance trials on different prescriptions of piezo-actuators

Introduction (cont…)

Research Objectives

Research AimTo define the decay characteristics of piezo-actuators in the view of design and develop the auto-compensation methodology

1. Design and develop test equipments for establishing the decay characteristics evaluations of piezo-actuators

What is Piezo-Actuator?

Fig. 1: Photograph of Piezo-Actuator manufactured by Noliac A/S

Piezo-Actuators Characteristic

Fig. 2: Graph of Displacement Vs. Force: Piezo-Actuator Characteristic

Dis

plac

emen

t [m

icro

ns]

Force [N]

Uo

Blocking Force

,

Fmax

U2

U1

3 U = 0V

External Spring Characteristic curve

Free Stroke

Uo > U1 > U2 > U3

Characteristic Decay Phenomenon of Piezo-Actuators

•Characteristic decay as a function of time is

usually called “degradation” or “ageing” .

•The term “fatigue” has been used by numerous researchers to describe the loss of performance of piezoelectric materials, which is

due to electrical or mechanical loading.

Definitions

Characteristic Decay Phenomenon of Piezo-Actuators (Cont.)

“Piezoelectric materials are commonly made from poled devices, which can

readily dipole by applying high electrical field, and mechanical stress”.

[Dr Markys G Cain, at. el (1998)].

Characteristic Decay Phenomenon of Piezo-Actuators (Cont.)

“The loss of performance of piezoelectric actuator is usually

logarithmic and manufacturers will quote the lost of performance in

terms of percentage loss per decade”.

[B. Andresen Noliac A/S, Kvistgaard, Denmerk)].

The Technique of Degradation Evaluation of Piezo-Actuator

• Measurement of Capacitance

• Measurement of Free Stroke

• Measurement of Blocking Force

• Force/Displacement Characterisation

Measurement Methodology

Fig. 3: Measurement flow of decay characteristics of Piezo-Actuators

Force/Displacement characteristic measurement

Capacitance Measurement

Long-Term Cyclic Test for specific number of cycles

Measurement Flow

Measurement Methodology (cont….)

Fig. 4: Test equipment setup for establishing the decay characteristics of Piezo-Ceramics

Test Equipment

Characteristic MeasurementMeasurement Methodology (cont…)

F = 24 N

Step 1Uo = 0V

Displacement [microns]

Force [N]

Force/Displacement Curve at Uo = 200V

F = 24 NF = 0 NF = 0 N

F

F = Blocking Force, Fmax

Step 2Uo = 0V

Step 3Uo = 200V

Step 4Uo = 200V

Step 5Uo = 200V

Force/Displacement Curve at Uo = 0V

∆Lo∆Lo

ΔL24

ΔL24

Point A

Point A’

Point B

Point B’

Point B’1

Blocking Force, Fmax

Note:∆Lo = Free Stroke [m]∆L24 = Compression of the Piezoelectric

Actuator due to F = 24N = F/kT [m]= 24/kT [m]

kT = Piezoelectric Actuator stiffness [N/m]

Fig. 5: The steps of characteristics measurement

Results Capacitance as a function of number of cycles

5 X 5 X 20mm3SCMAS/S1/A/005/0,020/200/025/01000 : 5 X 5 X 20mm3

(SML-05-28)

0

200

400

600

800

1000

0 7

14 21 28 35 42 49 56 63 70 77 84 91 98

105

Number of Cycles in Millions

Cap

acit

ance

[n

F]

Actuator 1

Actuator 2

Actuator 35 X 5 X 40mm3

SCMAS/S1/A/005/005/0,040/020/052/01000 : 5 X 5 X 40mm3

(SML-05-29)

0.00

0.50

1.00

1.50

2.00

0 7

14 21 28 35 42 49 56 63 70 77 84 91 98 105

Number of Cycles in Millions

Cap

acit

ance

[u

F]

Actuator 1

Actuator 2

Actuator 3

Results (cont…) Free Stroke as a function of number of cycles

(SML-05-28)

0

5

10

15

20

25

30

0 7 14

21

28

35

42

49

56

63

70

77

84

91

98

10

5

Number of Cycles in Millions

Fre

e S

tro

ke

[mic

ron

s]

Actuator 1

Actuator 2

Actuator 3

SCMAS/S1/A/005/0,020/200/025/01000 : 5 X 5 X 20mm3

(SML-05-29)

0

10

20

30

40

50

60

70

0 7

14

21

28

35

42

49

56

63

70 77

84

91

98

10

5

Number of Cycles in Millions

Fre

e S

tro

ke

[mic

ron

s]

Actuator 1

Actuator 2

Actuator 3

SCMAS/S1/A/005/005/0,040/020/052/01000 : 5 X 5 X 40mm3

Results (cont…) Blocking Force as a function of number of cycles

(SML-05-28)

0

200

400

600

800

10000 7

14 21 28 35 42 49 56 63 70 77 84 91 98

105

Number of Cycles in Millions

Blo

ckin

g F

orc

e [N

]Actuator 1

Actuator 2

Actuator 3

SCMAS/S1/A/005/0,020/200/025/01000 : 5 X 5 X 20mm3

(SML-05-29)

0

200

400

600

800

1000

0 7

14 21 28 35 42 49 56 63 70 77 84 91 98

105

Number of Cycles in Millions

Blo

ckin

g F

orc

e [N

]

Actuator 1

Actuator 2

Actuator 3

SCMAS/S1/A/005/005/0,040/020/052/01000 : 5 X 5 X 40mm3

Conclusion and Future Works

Base on the preliminary results, after applying 108 cycles of cyclic voltage of 200V (4kV/mm), the piezo-actuators maintained its excellent characteristics with no degradation (decay characteristic) of the free stroke, blocking force and capacitance

In order to observe the degradation trends, it is beneficial to evaluate the piezoelectric actuators under the higher mechanical load condition

end