Evaluation and comparison of estimated wave elastic modulus of concrete, using embedded and surface bonded PZT sensor/actuator systems

Transcription

1 Evaluation and comparison of estimated wave elastic modulus of concrete, using embedded and surface bonded PZT sensor/actuator systems Presented by: Ayumi Manawadu, Ph.D. student Zhidong Zhou, Ph.D. student Pizhong Qiao, Professor

2 US infrastructure in poor shape Image Source: Google images ASCE score for bridges in US: C+ 4 in every 10 bridges are 50 years or older Many bridges are approaching the end of their design life Condition assessment and continuous monitoring is important Non Destructive test methods available are expensive, inaccurate, or difficult to implement Right now there is no effective technology! Approach : use of ultrasonic wave based sensor systems 2

3 Objectives 3 To study and evaluate suitability of surface bonded sensor systems to determine wave elastic modulus of concrete (E), with comparison to embedded sensor systems (over first 28 days after casting) To develop Finite Element models to verify the experimental results (for 28 th day results) To study the effect of orientation of embedded sensors in the estimation of E

4 Fundamentals of Piezoelectricity: Piezoelectricity (direct effect) Development of an electric potential across boundaries when a mechanical stress (pressure) is applied (1880, Curie brothers). Converse effect also exists. Image Source: Google images 4

5 Fundamentals of Piezoelectricity: Piezoelectricity contd. 5 S jk = d ijk E i + s E ijkl T kl (1) S jk : Strain [6x1] E i : Applied electrical field vector (volt/m) [3x1] T kl : Stress (N/m 2 ) [6x1] d ijk : Piezoelectric constants (Coulomb/N or m/volt) E s ijkl : Compliance matrix (m 2 /N) Source: Sirohi & Chopra, 2000), (Jordan & Ounaies, 2001)

6 Fundamentals of Piezoelectricity: Examples of piezoelectric material 6 Natural Biological Synthetic ceramics Polymers Sucrose (table sugar) Dry Bones Lead zirconate titanate - PZT (Pb[ZrxTi1 x]o 3 with 0 x 1) Quartz Tendon Barium titanate (BaTiO3) Polyvinylidene fluoride (PVDF): Rochelle salt Silk Potassium niobate (KNbO3) Topaz Enamel Sodium tungstate (Na2WO3) Berlinite DNA Bismuth ferrite (BiFeO3)

7 Experimental Program: Outline Concrete beam: 16 x4 x3 Smart Aggregate (SA) r=9.5mm, t=19.05mm B#1: SA 0⁰ to beam longitudinal axis B#2: SA 45⁰ to beam longitudinal axis Smart Aggregate (SA) r=5mm, t=0.4mm PZT B#3: SA 90⁰ to beam longitudinal axis Surface Bonded PZT (in all three beams above) 7

8 Experimental Program: Procedure Prepare SA Coat PZT with Epoxy Encase in cement mortar Wrap copper coils Cure SA Embed SA and bond PZT Embed SA at 0⁰, 45⁰, 90⁰ orientations (to longitudinal Axis) Surface bond PZT with epoxy Cure Testing Sensor response over first 28 days Time of Flight of 1 st shear wave package Smart Aggregates : Song et.al (2008) 8

9 Experimental Program: Setup 9 Power Amplifier Arbitrary waveform generator Dual Channel Filter Oscilloscope

10 Experimental Program: Fundamentals of wave propagation Image Source: Google images 10

11 Signals captured by SA (mv) Experimental Program: Determination of Time of Flight (ToF) ToF First Shear wave package Time (s)

12 Amplitude Experimental Program: Procedure to determine Wave Elastic Modulus (E) 100kHz 3.5 cycles Hanning windowed sine wave C s = l TOF (2) C s = E d 2(1+ν)ρ (3) 0.0 C R = ν 1+ν E d 2(1+ν)ρ (4) Time (x10-5 s) 1 TOF C s (or C R ) 1 E f t = 0.5(1 cos( 2πt )) sin(2πt ) 0 < t < s 0 t > s (5) C s Shear wave velocity, C R Rayleigh wave velocity, ToF Time of flight 12

13 Finite Element Model Abaqus : Modelling of Smart Aggregate (SA) Part Element Mesh PZT linear piezoelectric brick 1 mm Mortar casing 8 node linear brick full integration 2.5 mm PZT: d 33 =320 pm/v, d 31 =-140 pm/v, E 33 =73 GPa, E 11 =86 GPa, ρ=7.9 g/cm 3 Constraints: Surface based ties: PZT-casing (master surface: PZT) Coupling: Electric potential of PZT - master nodes Step : static general Boundary conditions PZT top : Apply Linear Electric potential PZT bottom : Electric Potential 0V Smart module bottom surface : Fixed Undeform Deform 13

14 Finite Element Model Abaqus : Results from static/general analysis of SA u1,u2 disp. (x10 9 m) u3 disp. (x 10 6 m) Electric Potential -25 Electric Potential (V) U Electric Potential (V) 14

15 Finite Element Model Abaqus : Analysis (concrete beam+ SA) 15 Concrete beam : Element : C3D8 full integration Mesh : 2.5 mm (at least 2.67 mm for accurate results) Assumed: E= 20GPa, ν=0.2, ρ=2400 kg/m 3 Step : Dynamic, implicit (time period: 3e-4 s, increment size 1e-6s) Field and History Output : EPOT, U Boundary conditions : Smart cement module was modelled as before Sinusoidal Excitation signal applied as before Concrete beam free boundary conditions

16 Finite Element Model Abaqus : Analysis (beam+ SA/PZT)- displacement contours 16 Embedded SA at 0⁰ Embedded SA at 45⁰ Embedded SA at 90⁰ Surface bonded PZT patches

17 Finite Element Model Abaqus : Relevant response signals from FE Analysis Amplitude u3 (x10-12 m) Amplitude u3 (x10-12 m) 8 Embedded SA First shear wave package Time (s) Surface bonded PZT patches Rayleigh wave package Time (s) 17

18 ToF (µs) Change in experimental ToF of first shear wave package on 28 th day : embedded PZT patches Experimental_Embedded Numerical_embedded Theoretical_embedded Beam Number Note : E= 18GPa is assumed for the FE model. Maximum difference between; experimental results is 2.99%, experimental and numerical results is 8.96%.

19 ToF (µs) Change in experimental ToF of Rayleigh wave package on 28 th day : surface bonded PZT patches B#1 B#2 B#3 Numerical Theoretical Note : E= 18GPa is assumed for the FE model. Maximum difference between experimental results is 1.85% 19

20 Wave Modulus of Elasticity, E (GPa) Change in experimental dynamic elastic modulus with hydration : embedded & surface bonded PZT patches 20 B#1_surf B#2_surf B#3_surf B#1_embed B#2_embed B#3_embed y = x y = x y = x y = 16.04x y = x y = x No. of days since casting

21 Wave Modulus of Elasticity, E (GPa) Comparison of experimental wave elastic modulus of embedded & surface bonded PZT patches at 28 th day Surface Bonded (exp) Embedded (exp) B#1 B#2 B#3 FEM/Theo Note : E= 18GPa was initially assumed for the FE model. Maximum difference between surface bonded and embedded PZTs is 10.47% 21

22 Summary of findings and Conclusions 22 Estimated wave modulus of elasticity (E), through surface bonded sensors is larger than the embedded sensors Estimated E from the two systems are in good agreement with each other (with a maximum difference of 10.47%) Orientation of sensors has an impact on the clarity of wave packets, but no significant effect on the estimated E (maximum difference: Proposed finite element models are in good agreement with theoretical and experimental results

23 Future research 23 Identify the effectiveness of using surface bonded sensors to determine elastic material properties of concrete/polymer concrete in the presence of Cracks Freeze/thaw attacks Changes in beam dimensions compared to embedded PZT sensor systems Study the effectiveness of using surface bonded sensors in detection of various damages, over embedded sensor systems Build a portable device for damage detection and material property assessment of large scale civil infrastructure

24 Thank You! 24

25 Questions? 25