3. EL ENTORNO DE LOS CENTROS EDUCATIVOS Y EL APRENDIZAJE
3.1 Horas de clase
6.1 CONCLUSION
Structural health monitoring has its role to play most in present era. Primary motive of health monitoring is detecting and identifying the internal damage location and severity in order to restrain further damage or crack propagation. Piezoelectric impedance based monitoring process has great scope in engineering sector because it possesses features like high detection sensitivity, large bandwidth and easy integration.
In this study, plain-weave textile composites are utilized to demonstrate the capability of piezoelectric transducer. The elastic properties of the composite are determined using the fiber tow properties that are derived via the Concentric Cylinder Assemblage micromechanics model. Finite element modeling is done in commercial software ANSYS APDL to observe electrical admittance variation around natural frequency of the entire structure to investigate structure condition. Delamination was studied at first but results show very small shift in frequency of the same mode number for healthy and defective structures along with same magnitude of admittance. Fourth modal frequency for healthy and delaminated beam are 1654 and 1653.7 Hz. This small shift of 0.3 Hz of frequency shift makes delamination detection via impedance approach not feasible. So, investigation was shifted to detection of damage. Damage can be thought of as reduction of stiffness in the whole structure. Fair amount of shift in the modal frequency was observed with respect to damage level. Modal analysis results provide 944.54 Hz, 896.71 Hz and 846.07 Hz resonant frequencies for healthy, 10% and 20% damaged beam respectively which represent third modal frequency. Modal frequency of the structure decreased as well as admittance value lowered with damage increment within the body.
Pre-preg manufacturing method is carried out to fabricate composite panel from which samples are cut for testing according to ASTM standards. Panel is fabricated in such a way that enabled 45-degree fiber orientation with respect to the longitudinal axis of specimen. This strategy is taken to easily incorporate damage into the specimen via tensile test. 45-degree fiber orientation makes it easier to create damage compared to the longitudinally aligned fiber sample. Young’s modulus of our sample is found to be 12.6 GPa. This is very close to the modulus extracted from finite element modeling via using analytically derived material properties which is 11.6 GPa.
Piezo patch is embedded to the host body. Hammer test provides with the modal frequencies of the entire system. Clear amount of shift is observed for natural frequencies related to damaged specimen from healthy one. Then sine sweep voltage is applied to actuate the transducer. It provided voltage drop across the resistor that denoted the coupling effect of the patch with the host structure. Electrical admittance thus impedance plot expressed response to body deformation actuated by the piezoelectric transducer. Admittance changes are viewed between healthy and damaged structures. Results from finite element modeling and experimentation both provide distinctive shift of modal frequencies for damaged beam from healthy specimen. Therefore, piezoelectric impedance/admittance technique is efficient in detecting damage or degradation within composite structure.
6.2 FUTURE SCOPE
Structural health monitoring is currently in the developing stages that requires more research before practical implementation can be done on a regular basis. Our research shows promising aspects for electrical impedance or admittance based health monitoring of composite structures. Internal damage that cannot be identified by visual inspection can be brought to attention via this admittance based technique. Finite element model and experimentation both provided distinctive amount of shift in modal frequencies for damaged specimen from healthy condition. Thus, damage detection is performed successfully within the composite structure. But there lies a good deal of research scope to enhance damage detection method. Identification of damage location and severity can be research field of interest for the future. This will assist to pinpoint the damage location as well as damage intensity which will contribute in speeding up the repair and reduce related cost.
Further research may be carried out to check on various composite materials as each composite has its unique properties and usage area. Various composites are being developed and made available for industry. Aerospace, automobiles, sports equipment etc. possess a significant utilization of composite materials. These areas have issues of human safety as well as entertainment. Therefore, structural health monitoring of various composite structures is of prime importance.
BIBLIOGRAPHY
[1] Giurgiutiu, V., 2005, “Tuned Lamb wave excitation and detection with piezoelectric wafer active sensors for structural health monitoring”, Journal of Intelligent Material Systems and Structures, V16, 291-305.
[2] Wang, X., Lu, Y. and Tang, J., 2008, “Damage detection using piezoelectric transducers and the Lamb wave approach: I. System analysis”, Smart Materials and Structures, V17, 025033. [3] Wandowski, T., Malinowski,P. and Ostachowicz, W.M., 2011, “Damage detection with concentrated configurations of piezoelectric transducers”, Smart Materials and Structures, V20, 025002.
[4] Yu, L. and Giurgiutiu, V., 2012, “Piezoelectric wafer active sensors in lamb wave-based structural health monitoring”, Journal of the Minerals, Metals & Materials Society, V64, 814-822. [5] Yoon, H.S., Jung, D. and Kim, J.H., 2012, “Lamb wave generation and detection using piezoceramic stack transducers for structural health monitoring applications”, Smart Materials and Structures, V21, 055019.
[6] Koduru, J.P. and Rose, J.L., 2013, “Transducer arrays for omnidirectional guided wave mode control in plate like structures”, Smart Material and Structures, V22, 015010.
[7] Naidu, A. and Soh, C., 2004, “Identifying damage location with admittance signatures of smart piezo transducers”, Journal of Intelligent Material Systems and Structures, V15, 627-642.
[8] Jiang, L. J., Tang, J. and Wang, K. W., 2006, “An enhanced frequency-shift-based damage identification method using tunable piezoelectric transducer circuitry”, Smart Materials and Structures, V15, 799-808.
frequency shift information with tunable piezoelectric transducer circuitry”, Smart Material and Structures, V17, 065003.
[10] Giurgiutiu, V., 1999, “Experimental investigation of E/M impedance health monitoring for spot-welded structural points”, Journal of Intelligent Material Systems and Structures, V10, 802- 812.
[11] Park, S., Yun, C.B. and Inman, D.J., 2008, “Structural health monitoring using electro‐ mechanical impedance sensors”, Fatigue & Fracture of Engineering Materials & Structures, V31, 714-724.
[12] Wang, X. and Tang, J., 2010a, “Damage detection using piezoelectric admittance approach with inductive circuitry”, Journal of Intelligent Material Systems and Structures, V21, 667-676. [13] Madhav, A.V.G. and Kiong, S.C., 2010, “Application of electromechanical impedance technique for engineering structures: review and future issues”, Journal of Intelligent Material Systems and Structures, V21, 41-59.
[14] Zhou, W. and Zuo, L., 2012, “Sensitivity-enhanced admittance-based structure health monitoring using a higher-order resonant circuit”, Smart Materials and Structures, V21, 105023. [15] Annamdas, V.G. and Radhika, M.A., 2013, “Electromechanical impedance of piezoelectric transducers for monitoring metallic and non-metallic structures: A review of wired, wireless and energy-harvesting methods”, Journal of Intelligent Material Systems and Structures, V24, 1021- 1042.
[16] Park, G., Sohn, H., Farrar, C.R. and Inman, D. J., 2003, “Overview of piezoelectric impedance-based health monitoring and path forward”, The Shock and Vibration Digest, V35, 451-463.
of Piezoelectric Active-Sensors in Structural Health Monitoring”, Smart Material and Structures, V15, 1673-1683.
[18] Park, S., Ahmad, S., Yun, C. and Roh, Y., 2006, “Multiple Crack Detection of Concrete Structures Using Impedance-based Structural Health Monitoring Techniques”, Experimental Mechanics, V46, 609-618.
[19] Park, G., Cudney, H. and Inman, D., 2000, “Impedance-Based Health Monitoring of Civil Structural Components”, Journal of Infrastructure Systems, V6(4), 153-160.
[20] Shuai, Q., Zhou, K., Zhou, S. and Tang, J., 2017, “Fault Identification Using Piezoelectric Impedance Measurement and Model-Based Intelligent Inference with Pre-Screening”, Smart Materials and Structures, V26, 045007.
[21] Giurgiutiu, V. and Rogers, C., 1999, “Modeling of the Electro-Mechanical Impedance Response of a Damaged Composite Beam”, ASME Winter Annual Meeting, ASME Aerospace and Materials Divisions, Adaptive Structures and Materials Systems Symposium, AD-V 59, MD- V87, 39-46.
[22] Wang, X. and Tang, J., 2009, “Damage Identification Using Piezoelectric Impedance Approach and Spectral Element Method”, Journal of Intelligent Material Systems and Structures, V20, 907-921.
[23] Gresil, M., Yu, L., Giurgiutiu, V. and Sutton, M., 2012, “Predictive Modeling of Electromechanical Impedance Spectroscopy for Composite Materials”, Structural Health Monitoring 11, V 6, 671-683.
[24] Herakovich, C.T., 1998, “Mechanics of Fibrous Composites”, Wiley, New York.
[25] Hyer, M.W., Waas, A.M., 2002, “Micromechanics of Linear Elastic Continuous Fiber Composites”, Comprehensive Composite Materials, Pergamon, Oxford, 345-375.
[26] Christensen, R.M. and Lo, K.H., 1979, “Solutions for Effective Shear Properties in Three Phase Sphere and Cylinder Models”, J. Mech. Phys. Solids, V27, 315-330.
[27] Timoshenko, S. and Goodier, J.N., 1951, “Theory of Elasticity”, McGraw-Hill.
[28] Junior, C.D.M., Erturk, A. and Inman, D.J., 2009, “An Electromechanical Finite Element Model for Piezoelectric Energy Harvester Plates,” Journal of Sound and Vibration, V327, 9-25. [29] Zhou, K., Shuai, Q. and Tang, J., 2014, “Adaptive Damage Detection Using Tunable Piezoelectric Admittance Sensor and Intelligent Inference”, Proceedings of ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2014-7624. [30] Eshelby, J.D., 1957, “The Determination of the Elastic Field of an Ellipsoidal Inclusion and Related Problems”, Proc. R. Soc. A: Math. Phys. Eng. Sci. 241, 376-396.
[31] Eshelby, J.D., 1956, “Progressive Solid State Physics”, Academic Press, New York, 79-144. [32] Zhang, D. and Waas, A.M., 2014, “A Micromechanics Based Multiscale Model for Nonlinear Composites”, Acta Mech 225, 1391-1417.
[33] Quek, S.C., Waas, A.M., Shahwan, K.W. and Agaram, V., 2013, “Analysis of 2D Triaxial at Braided Textile Composites”, International Journal of Mechanical Sciences, Vol. 45, No. 6-7, 1077-1096.
APPENDIX
Figure A-1: Comparison of healthy and damaged specimen for first mode
0 10 20 30 40 50 60 -10 -5 0 5 10 15 20 25 30 0 50 100 150 200 250 300 350 400 450
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Comparison of Healthy and Damaged Specimen for 1st Modal
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Figure A-2: Comparison of healthy and damaged specimen for second and third modes 0 10 20 30 40 50 60 70 0 5 10 15 20 25 550 650 750 850 950 1050 1150 1250
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Comparison of Healthy and Damaged Specimen for 2nd and
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Figure A-3: Comparison of healthy and damaged specimen for fourth and fifth modes 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 2000 2200 2400 2600 2800 3000 3200