Easy installation [possible alternate] of PZTs on host structure

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Presenter : Venu Gopal Madhav ANNAMDAS, PhD

Co-Authors:

RADHIKA Madhav Annamdas, JNTU, India YANG Yaowen, NTU, Singapore

SPIE 2009

1

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Outline •Introduction to EMI •Permanent bonding •Temporary bonding •Design of portable beam •Comparison of signatures obtained from both.

• Damage assessment • RMSD evaluation •Conclusions

3

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

PZT based Electromechanical Impedance (EMI) principle in SHM PZT: surface bonded or embedded + Electric field along direction 3 Structure

PZT

2 3 1

Zďƒ 1 / Admittance (Y)

ďƒ&#x;Finally obtain it

PZT: measures resistance of structure to vibrations

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

PZT based Electromechanical Impedance (EMI) principle in SHM Z (EMI) ďƒ 1 / Admittance (Y) {Y = Conductance + j (Susceptance)}

Healthy Structure

Y H = G H + j BH

Damaged Structure YD = GD + j BD

Comparison mechanism

3

There are several other factors that might affect the EM admittance signatures of a structure as given below.

1.

Humidity, moisture and temperature of the surroundings, acid or alkaline attack, can lead to deterioration of the PZT material.

2.

The presence of magnetic or electrical fields within the vicinity of the PZTs might also affect the electrical properties of the PZTs. 3.

Induced stresses due to static and dynamic loadings could also alter the signatures of the PZTs 4.

Moreover ageing problem will affect the signatures when PZTs are permanently bonded on the host structure

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

•If signatures are acquired from permanently bonded PZT over a certain period of time from the same structure • if there are any changes in the signature can be due to the damage in the structure or either the factors mentioned above.

ANY ALTERNATE? •it is better to take away the PZT after the signatures are acquired and then re install on the same location at later stage when a next signature acquisition is required.

•If any changes are observed in signatures, then obviously it indicates the problem in host structure.

5

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Experimental Setup Multiplexer

Specimen

Impedance Analyzer

PZT 6‌‌

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Experimental details ďƒ 3 PZTs were bonded on lower side of a beam

7

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Experimental details

8

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Experimental details

baselines 9

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Configuration

PZTs

Baseline

1

Individual Signatures

P1, P2, P3, P4, P5 P6

6

2

Grouped Signatures (Parallel excitation)

P1,P2

6

P2, P3 P1, P3 P4,P5 P5, P6 P4, P6

3

Collective Signatures (Parallel excitation)

P1, P2, P3

2

P4, P5, P6 10

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Comparison of admittance signature from uniplexing and multiplexing process a) Individual PZTs P1 and P4 b) Grouped PZTs (P1, P3) and (P4, P6) c) Collective PZTs (P1, P2, P3) and (P4, P5, P6)

exp 11

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Comparison of signatures for individual PZTs (a) PZT -P1 (b) PZT- P4.

12

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Comparison of signatures for the grouped PZTs (a) [P1, P3] (b) [P4, P6].

13

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Comparison of 1st, 5th and 10th damage from the collective PZTs (P1, P2, P3 and P4, P5, P6).

14

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique Root Mean Square Deviation (RMSD) index.

i=N

RMSD(%) =

∑ (w i =1

i

i=N

2

− ui )

2 u ∑ i

x100

i =1

15

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique

Comparison of RMSD index for 1st, 5th and 10th damage states

16

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique CONCLUSION •Single PZT interaction or multiple PZT interactions are effective in dealing with damages.

• instead of traditionally bonding the PZTs on the host structure, a way of using a portal beam as interface between the actual structure to be monitored and PZTs was presented.

•The study shows that, the portable beam with 3 PZTs bonded on it, can effectively indicate the presence of damages.

•In addition, the study also had quantified the damages in terms of RMSD index.

The temporarily bonded PZTs indicate that they are effective in predicting damages.

Replacement of PZT [if permanently bonded, highly difficult]

17

Easy installation method of piezoceramic (PZT) transducers for health monitoring of structures using electro-mechanical impedance technique CONCLUSION •Thus, there may not be necessary in future to always permanently attach PZTs to the host structure. But instead, the PZTs can be bonded on some metal structure, and this metal structure can be easily fixed to host structure to be monitored.

•Once the signatures are acquired, the portable structure can be easily removed.

[DEPENDS ON HOW FLEXIBLE THE PORTABLE STRUCTURE IS ] •The appearance of the structure need not be disturbed. At the same time the quality of the monitoring method need not be compromised.

•Due to the limited sensing range of a single PZT, multiple surface-bonded PZTs are necessary in determining the overall structural integrity of any practical applications.

•Both uniplexing and multiplexing are needed, which were investigated in the present study.

LIMITATION No real time monitoring Engineering skills are required to replace portable structure back on host if required 17