Remote Detection of Stage II to Stage IIICracking in Steel Bridge Girder Material                             M. Hossain  ...
Background   S         Safe area                          Nda/dN        unstable cracking                                c...
Background                                               Voltage, mV                                                      ...
ObjectiveBridge Prognostic System•   Self-Powered•   Wireless Sensor Network•   Structural Bridge Health PrognosisCurrent ...
Experimental Procedure            12.0 in                                            3.25 in                      R15I    ...
Data Filtering and Reducing Procedures1. Eliminate AE collected below 80% of peak load                                    ...
Data Filtering and Reducing Procedures                                                                      Counts2. Frict...
Data Filtering and Reducing Procedures4. Swansong Ⅱ filter to minimize mechanical noise                                   ...
Data Filtering and Reducing Procedures5. Evaluate quality of filtered AE data                                             ...
Results and Discussion1. Sparse dataset                                4                               3.5       Hit rate ...
Results and Discussion2. Determination of critical cracking level                                         400,000         ...
Results and Discussion2. Determination of critical cracking level                                         16,000,000      ...
Results and Discussion2. Determination of critical cracking level                         35,000                         3...
Results and Discussion2. Determination of critical cracking level                        600                              ...
Results and Discussion3. Prediction of fatigue life     Absolute energy of AE, U ∝ J(∆K), released energy due to crack gr...
Results and Discussion3. Prediction of fatigue life                                 2        crack growth rate, da/dN     ...
Results and Discussion3. Prediction of fatigue life                              70                              60       ...
Results and Discussion4. AE-detected cracking locations        crack path                                                 ...
Conclusions and PerspectiveSummary:   AE absolute energy can provide warning signs for critical cracking in    steel brid...
Acknowledgements   This work is performed under the support of the U.S. Department of    Commerce,       National    Inst...
Thanks for your time and attention
Annex1 Construction of a and dU/dN arrays for Fatigue Life Prediction   Array of a:          original a: ao            ...
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Remote detection of stage ii to stage iii cracking in steel bridge girder material

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  • In-service steel bridges are reaching their fatigue lives every year. Fatigue life is usually described as S-N curve. Here, S represents applied stress. N is the number of load cycles. For a given material and set of loading conditions, if the number of load cycles exceeds the fatigue life, crack will develop in the structure. Crack growth rate curve describes crack growth behavior. da/dN is crack growth rate. Delta K is stress intensity range. Crack growth has three stages: Stage I-low speed cracking near threshold, Stage II-stable cracking and Stage III-unstable cracking. Stage Ⅱ is of practical importance. The stage Ⅲ will result in catastrophic failure, so the critical cracking level is the transition point between stage Ⅱ and stage Ⅲ.The pictures come from an in-service and cracked steel bridge in South Carolina. There is a growing need for nondestructive testing techniques to evaluate the fatigue damage and predict remaining fatigue life.
  • Joint venture project. Imagine:if no accurate data interpretation, the acquired signals are useless no matter how excellent the techniques, the instruments are.Importance of current task
  • Joint venture project. Imagine:if no accurate data interpretation, the acquired signals are useless no matter how excellent the techniques, the instruments are.Importance of current task
  • It has been demonstrated that AE technique is able to detect cracking location, identify structural damage and predict fatigue life for steel bridge material.Perspective: Mechanism of AE corresponding to crack growing under varied loading conditions and in welded bridge elements
  • PAC: equipment setup and data acquisition
  • Remote detection of stage ii to stage iii cracking in steel bridge girder material

    1. 1. Remote Detection of Stage II to Stage IIICracking in Steel Bridge Girder Material M. Hossain ASNT 20th Annual Research Symposium & Spring Conference San Francisco, California 21-25 March, 2011This project is sponsored by the U.S. Department of Commerce, NIST-TIP (Cooperative Agreement Number 70NANB9H9007)
    2. 2. Background S Safe area Nda/dN unstable cracking critical cracking level Paris Law: stable cracking da/dN=C(∆K)m threshold K 2
    3. 3. Background Voltage, mV Time, μSAcoustic emission (AE) techniques: High sensitivity and reliability Capability of locating and quantifying active cracks 3
    4. 4. ObjectiveBridge Prognostic System• Self-Powered• Wireless Sensor Network• Structural Bridge Health PrognosisCurrent tasks• Understand mechanism of acoustic emission(AE) corresponding to crack growth behavior in the steel bridge material• Data interpretation to identify structural damage and deterioration• Modeling to assess the remaining fatigue life 4
    5. 5. Experimental Procedure 12.0 in 3.25 in R15I WDI 9.5 in 12.0 in AE-monitored fatigue tests: Compact tension (CT) specimens, made of A572G50 MTS 810 hydraulic machine Crack growth: clip gage, microscope and fiber light AE sensors: R15I 5, WDI 3 Sensor Highway II-Remote Asset Integrity Monitor 5
    6. 6. Data Filtering and Reducing Procedures1. Eliminate AE collected below 80% of peak load Yielding 2 4 Crack extension Pmax Y-stress Crack openingload Pmean Crack closure Grating 1 3 5 Pmin Reversed yielding time Y-strain Stress-strain behavior at crack tip in a load cycle 6
    7. 7. Data Filtering and Reducing Procedures Counts2. Friction emission tests to understand Peak Threshold characteristics of noise amplitude3. Pencil lead break tests to understand characteristics of genuine hits Rise time Duration 2 3 7
    8. 8. Data Filtering and Reducing Procedures4. Swansong Ⅱ filter to minimize mechanical noise 8
    9. 9. Data Filtering and Reducing Procedures5. Evaluate quality of filtered AE data 9
    10. 10. Results and Discussion1. Sparse dataset 4 3.5 Hit rate 3 2.5 Hit rate 2 10% increase of cyclic loads 1.5 1 0.5 0 0 5,000 10,000 15,000 20,000 Load cycles 10
    11. 11. Results and Discussion2. Determination of critical cracking level 400,000 350 Cumulative absolute energy Maximum stress intensity, MPa√m 350,000 Cumulative absolute energy, aJ 300 Maximum stress intensity 300,000 250 250,000 200 200,000 150 150,000 10% increase of cyclic loads 100 100,000 50,000 50 critical level 0 0 0 3,000 6,000 9,000 12,000 15,000 18,000 Load cycles 11
    12. 12. Results and Discussion2. Determination of critical cracking level 16,000,000 350 Cumulative signal strength Maximum stress intensity, Mpa√m Cumulative signal strength, V-T 14,000,000 300 Maximum stress intensity 12,000,000 250 10,000,000 200 8,000,000 150 6,000,000 10% increase of cyclic loads 100 4,000,000 2,000,000 50 critical level 0 0 0 3,000 6,000 9,000 12,000 15,000 18,000 Load cycles 12
    13. 13. Results and Discussion2. Determination of critical cracking level 35,000 30,000 Cumulative counts Cumulative counts 25,000 20,000 10% increase of cyclic loads 15,000 10,000 5,000 critical level 0 0 3,000 6,000 9,000 12,000 15,000 18,000 Load cycles 13
    14. 14. Results and Discussion2. Determination of critical cracking level 600 350 Cumulative hits Maximum stress intensity, MPa√m 500 300 Maximum stress intensity 250 Cumulative hits 400 200 300 150 10% increase of cyclic loads 200 100 100 50 critical level 0 0 0 3000 6000 9000 12000 15000 18000 Load cycles 14
    15. 15. Results and Discussion3. Prediction of fatigue life  Absolute energy of AE, U ∝ J(∆K), released energy due to crack growth dU/dN=B(∆K)p log(dU/dN)=plog(∆K)+log(B) Eq.(1)  Paris Law: da/dN=C(∆K)m; ∆K = ? da/dN=D(dU/dN)q Eq.(2)  Applies to Stage Ⅱcracking 15
    16. 16. Results and Discussion3. Prediction of fatigue life 2 crack growth rate, da/dN absolute energy rate, dU/dN 1 Linear (crack growth rate, da/dN) Linear (absolute energy rate, dU/dN) Log(da/dN), log(dU/dN) 0 -1 log(dU/dN) = 5.7489log(∆K) - 10.865 -2 -3 log(da/dN) = 3.8338log(∆K) - 9.9518 -4 1.75 1.8 1.85 1.9 1.95 2 2.05 Stress intensity range, log(∆K) 16
    17. 17. Results and Discussion3. Prediction of fatigue life 70 60 experimental crack Crack length, mm 50 predicted crack 40 30 20 10 0 0 10,000 20,000 30,000 40,000 Load cycles 17
    18. 18. Results and Discussion4. AE-detected cracking locations crack path 18
    19. 19. Conclusions and PerspectiveSummary: AE absolute energy can provide warning signs for critical cracking in steel bridge material. Absolute energy rate was found to most suitable feature. Specific material constants in terms of both AE and crack growth behavior should be evaluated. Robust data filtering techniques are required. The combination of a Swansong II filter with a waveform-based approach was found to be appropriate.Further work: Mechanism of AE corresponding to crack growth in welded bridge elements 19
    20. 20. Acknowledgements This work is performed under the support of the U.S. Department of Commerce, National Institute of Standards and Technology, Technology Innovation Program, Cooperative Agreement Number 70NANB9H9007. Special thanks to Jean-Louis Staudenmann. South Carolina DOT for providing access to bridges and related information for this project. Valery Godinez, Adrian Pollock, Miguel Gonzalez (Mistras); Brian Metrovich (Case Western Reserve Univ.); Fabio Matta (Univ. of South Carolina). 20
    21. 21. Thanks for your time and attention
    22. 22. Annex1 Construction of a and dU/dN arrays for Fatigue Life Prediction Array of a:  original a: ao  final a: o generally, Kmax=F∙S∙(π∙afinal)1/2 = KIC , where F=f(geometry), S- applied stress, KIC – fracture toughness o compact tension(CT) specimen-cantilever beam: Kmax=Fp∙P/(t∙b1/2) = KIC , where Fp =fp (av/b), av=(afinal-1+ afinal)/2, P-applied load, t-thickness, b-width CT SE o single edge(SE) specimen-freely supported beam: Kmax=F∙Sg∙(π∙afinal)1/2 = KIC, where F=f(av/b), Sg = 6M/(b2∙t), M-applied moment  a(i+1)=r∙ai , r ≈1.10, Array of dU/dN:  original dU/dN: (du/dN)o  final dU/dN: (dU/dN)final=B(∆KIC )p , ∆K= KIC∙(1-R), where B, p-material constants, R-load ratio  (dU/dN)(i+1) / (dU/dN)i = B(∆K(i+1) / (∆K )i ) p = B(r) p/2 , r ≈1.10 22

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