The document discusses structural health monitoring (SHM) techniques, focusing on the use of smart materials like piezoelectric sensors for continuous monitoring and damage detection in structures. It describes various sensing methods, emphasizing the effectiveness of high frequency electro-mechanical impedance techniques utilizing piezoelectric materials for assessing structural integrity. Experimental studies demonstrate the sensitivity of these methods to structural damage, advocating for their application in enhancing safety and maintenance of engineering structures.

1. Presented By,
Dr. S. N. Khante
Associate Professor
and
Bhagyashri D. Sangai
APPLIED MECHANICS DEPARTMENT
GOVT. COLLEGE OF ENGINEERING
AMRAVATI
(An Autonomous Institute of Govt. of
Maharashtra)

2.  Combination of : Foundations, Basements, Columns, Beams,
Slabs etc.
 Damages are bound to occur due to:
 Mismanagement in construction,
 Lack of quality in control,
 Temperature conditions,
 Loading and aggressive environment etc.
 Damages such as surface cracks, holes, segregation, settlements
etc.
 Adversely affects the performance of the structure.
What is a Structure ?

3. Damages in Structure
Collapse of Bridge on
Mississippi River

4.  Structural health monitoring is the continuous monitoring of
structures using integrated or applied sensor.
 Aim at assuring structural integrity and periodic inspections to
detect damages resulting from fatigue, corrosion, excessive loads
impact , etc.
 Health monitoring by smart materials is one of the best possible
solution.
 Smart materials involve Piezo-electric materials, Optical Fibers,
Shape-Memory Alloys etc.
 The primary reasons to use smart materials in Structural Health
Monitoring (SHM) systems is due to the feasibility in host
structures; which can act as sensors and/or actuators to present the
health of a structure on continuous basis.
What is Structural Health Monitoring

5.  Structure
 Sensors
 Data acquisition systems
 Data transfer and storage mechanism
 Data management
 Data interpretation and diagnosis:
a)System Identification c)Structural condition assessment
b)Structural model update d)Prediction of remaining service life
SHM System's Elements

6.  In broad sense SHM methodologies can be classified as
Conventional technique and Techniques using smart materials.
 Conventional Techniques
 Global SHM technique
 Local SHM technique
 Global SHM technique
1. Global Dynamic Technique
2. Global Static Technique
 Local SHM technique
Techniques such as acoustic, ultrasonic,radiography, eddy
currents, thermal, magnetic field or electro-magnetic impedence,
etc.
Techniques in SHM

7.  Techniques Using “Smart” Materials
 Low frequency technique
 High frequency or Electro-Mechanical Impedance (EMI)
technique
 Low frequency technique
 Also known as vibration based methods as vibrations are given to
the host structure under consideration.
 PZT patch perform only the role of sensor and not an actuator.
 Less sensible to damages as there are noise problems.
 High frequency technique
 Also known as Electro-Mechanical Impedance (EMI) technique.
 PZT patch plays dual role as a sensor and as an actuator.
 More sensible to damages in the structures as there are no noise
nuisance

8.  Piezoelectricity means “Electricity from pressure”.
 Mechanical energy Electrical energy and vice versa.
 Can be applied as a Mechatronic Impedance Transducers (MIT)
 Piezoelectric ceramics (Lead Ziroconate Titanate, or in short,
PZT) and piezoelectric polymers (Polyvinylidene Fluoride, denoted
as PVDF) are commonly used.
Piezoelectric Patch
Piezoelectricity and Piezoelectric
Materials

9. Short film for Piezo Generator

10. Fig. : Modeling PZT-structure interaction
(a) A PZT patch bonded to structure under electric excitation
(b) Interaction model of PZT patch and host structure
Basics of EMI technique

11.  PZT patch is surface bonded or embedded inside the structures.
 When an alternating electric field is applied to the patch, it expands
and contracts dynamically in direction ‘1’. Hence, two end points
of the patch can be assumed to encounter equal impedance Z from
the host structure.
 The patch (length 2l, width w and thickness h) behaves as thin bar
undergoing axial vibration. The complex electro-mechanical
admittance Y of the coupled system is derived as
 Where, d31 is the piezoelectric strain coefficient of the PZT
material, ȲE is the complex Young’s modules under constant
electric field, (εɛ33)T is the complex electric permittivity at constant
stress, Za is mechanical impedance of the PZT patch, ω is angular
frequency and kl is the wave number.
Basics of EMI technique

12.  Piezoelectric material : Sensor and actuator application
 Specimen under consideration : 2 Reinforced Concrete beams
(100X100X500 mm) with M20 grade concrete and Fe 250 steel.
 Reinforcement provided was 2 x 6 dia at top and bottom along
with stirrups of diameter 6 dia @ 80 mm c/c.
 Experimental study was performed in two phases – Healthy and
various damaged conductance and susceptance signatures are taken
for each specimens.
 LCR meter with connecting fixture, and VEE PRO software for
data acquisition.
 Frequency range 100 kHz – 250 kHz
 Material
 PZT 5H sample, Co-axial cable and specimens.
 Epoxy adhesive Araldite.
Materials and Specimens

13. Photograph: PZT 5-H sample
Photograph: LCR meter with the connecting fixture.
Photograph: Co-axial cable

14.  Firstly, the PZT patch was soldered out through two electrodes
present on the patch, then this patch was bonded on to the surface
of specimen using a well-tested epoxy adhesive.
 In this case Araldite adhesive has been used as the sensible
frequency range of the PZT patch is high and the PZT patch had
dual roles i.e. sensor and actuator functions.
 Then, the soldered PZT patch was wired to Impedance Analyzer
through Connecting Fixture of LCR meter. Then the frequency was
swept through 100 kHz to 250 kHz i.e. the PZT patch transfers this
vibrations to the structure through adhesive bond layer.
 These vibrations are transferred to structures and reflected back
from the same PZT patch through waves, which will indicate the
health of the structure. The required parameters i.e. Conductance
(G) and Susceptance (B) are directly measured through LCR meter
for all the values of frequency.
Experimental set-up

15. Fig. : Assembly for Experimentation of EMI technique
 This data is transferred to personal computer by USB cable. The
data is processed and then the graphs of Conductance Vs
Frequency and Susceptance Vs Frequency are directly plotted in
VEE PRO 9.32 software. These graphs are said to be the
“Conductance Signature” or just a “signature” and “Susceptance
Signature” for that particular specimen.
 The VEE PRO 9.32 is Graphical programming language for test
and measurement applications.
Experimental Set-up

16.  Beam 1: Damage 1- crack 72 mm deep, Damage 2 – scraping 1
nearer to right support i.e. near PZT, Damage 3 – scraping 2 nearer
to left support i.e. some distance away from PZT. The cracks were
given by Universal Testing Machine (UTM) under flexure for all
beams.
Fig. : Integral beam 1 Fig. : Damaged beam 1
Specimen and Damage details

17.  Beam 2: The patch PZT-1 at 150 mm and PZT-2 at 450 mm from
right support. The damages introduced were, Damage 1- crack 1:
32 mm deep, Damage 2 – crack 2: 60 mm deep, Damage 3 –
scraping 1 nearer to right support i.e. near PZT 1, Damage 4 –
scraping 2 nearer to left support i.e. near PZT 2, Damage 5 –
scraping 3 between the two PZT’s.
Fig. : Healthy beam 2 Fig. : Damaged beam 2

18.  The PZT patch was subjected to frequency range of 100-250 kHz.
 For this beam, the two PZT patches were employed and the
responses were recorded for all the stages by impedance analyzer for
both the PZT’s.
 PZT patch 1 peaks are more prominent and also change in
signature with changes in damage level are categorically visible when
compared to PZT patch 2.
Results for Beam 1

19.  Response peaks for PZT1 are well defined even after
introduction of damages.
Results for Beam 2

20.  BEAM 1: The PZT is sensible for all the damages while, PZT2
being less sensible.
Positioning Study

22.  BEAM 2: It is clear from the results that both PZT1 and PZT2
follow the same pattern for all the damages, while PZT 1 results are
more effective because there are occurrences of peaks and little
vertical shifting of conductance values for the respective damages.
Positioning Study

23. It can be said from positioning study that, PZT patch plays an
important role in damage detection if it is placed nearer to damages

24.  Piezoelectric material (PZT 5H grade) being smart material is
sensible at high frequencies to damages occurring in the
structures. Hence EMI technique can be extensively accepted
for structural health monitoring systems in the form of sensor
and actuator.
 It can be concluded that, PZT patch is location sensitive as it
shows higher damage sensitivity when positioned near the
damage zone.
Conclusion

25.  Bhalla, S, Soh, C. (a) (2004), “High frequency piezoelectric
signatures for diagnosis of seismic blast induced structural
damages”, Journal of NDT and E, Vol. 37, pp. 23:33.
 Bhalla, S. and Soh, C. (b) (2004), “Structural Health Monitoring by
Piezo Impedance Transducers. I and II: Modeling and
Applications”, Journal of Aerospace Engineering, Vol.17, No. 4,
pp. 154:175.
 Annamdas, V., Yang, Y., Soh, C. (2010), “Impedance Based
Concrete Monitoring Using Embedded PZT Sensors”, International
Journal Of Civil And Structural Engineering, Volume 1, No 3,
2010 pp. 414:424.
 Shanker, R. (2009), An Integrated Approach For Structural Health
Monitoring, Indian Institute Of Technology, Delhi.
REFERENCES

26. Park, S., Inman, D., Lee, J., and Yun, C. (2009),
“Reference-Free Crack Detection Using Transfer
Impedances”, Journal of Sound and Vibration, Vol. 329,
pp. 2337:2348.
Kim, M., Kim, E., Yan, Y., Park, H., Sohn, H. (2011),
“Reference-Free Impedance-Based Crack Detection In
Plates, Journal Of Sound And Vibration”, Vol. 330, pp.
5949:5962.
Du, G., Kong, Q.,Timothy, L., and Song, G. (2013),
“Feasibility Study On Crack Detection of Pipelines Using
piezoceramic Transducers”, International Journal of
Distributed Sensor Networks, pp.1-7

27. THANK YOU...