SMART AERONAUTICAL STRUCTURES: Development and Experimental Validation of a

275 Pages·2014·12 MB·English

UNIVERSIDAD POLITÉCNICA DE MADRID
school of aerospace engineering
DOCTORAL THESIS
SMART AERONAUTICAL STRUCTURES: DEVELOPMENT AND
EXPERIMENTAL VALIDATION OF A STRUCTURAL HEALTH MONITORING
SYSTEM FOR DAMAGE DETECTION.
by
JULIÁN SIERRA-PÉREZ
mechanical engineer m sc ing
( . - .)
2014
January

SMART AERONAUTICAL STRUCTURES: DEVELOPMENT AND
EXPERIMENTAL VALIDATION OF A STRUCTURAL HEALTH
MONITORING SYSTEM FOR DAMAGE DETECTION.
by
julián sierra pérez
-
supervised by
professor dr alfredo güemes
.
dr luis e mujica
. .
Department of Aerospace Materials and Production
School of Aerospace Engineering
Universidad Politécnica de Madrid
2014
January
Julián Sierra-Pérez : SMARTAERONAUTICALSTRUCTURES:DevelopmentandExperimentalValida-
tion of a Structural Health Monitoring System for Damage Detection. © January 2014
To my beloved wife.

ABSTRACT
In many engineering fields, the integrity and reliability of the structures are extremely important
aspects. They are controlled by the adequate knowledge of existing damages. Typically, achiev-
ing the level of knowledge necessary to characterize the structural integrity involves the usage of
nondestructive testing techniques. These are often expensive and time consuming.
Nowadays, many industries look to increase the reliability of the structures used. By using lead-
ingedgetechniquesitispossibletomonitoringthesestructuresandinsomecases,detectincipient
damage that could trigger catastrophic failures. Unfortunately, as the complexity of the structures,
components and systems increases, the risk of damages and failures also increases. At the same
time, the detection of such failures and defects becomes more difficult.
In recent years, the aerospace industry has done great efforts to integrate the sensors within
the structures and, to develop algorithms for determining the structural integrity in real time.
The ‘philosophy’ has being called “Structural Health Monitoring” and these structures have been
called “smart structures”. These new types of structures integrate materials, sensors, actuators and
algorithms to detect, quantify and locate damage within itself.
A novel methodology for damage detection in structures is proposed. The methodology is based
on strain measurements and consists in the development of strain field pattern recognition tech-
niques. The aforementioned are based on PCA (Principal Component Analysis) and other dimen-
sional reduction techniques. The use of fiber Bragg gratings and distributed sensing as strain sen-
sors is proposed. The methodology have been validated by using laboratory scale tests and real
scale tests with complex structures. The effects of the variable load conditions were studied and
several experiments were performed for static and dynamic load conditions, demonstrating that
the methodology is robust under unknown load conditions.
RESUMEN
Enmuchasáreasdelaingeniería,laintegridadyconfiabilidaddelasestructurassonaspectosdeex-
trema importancia. Estos son controlados mediante el adecuado conocimiento de danos existentes.
Típicamente, alcanzar el nivel de conocimiento necesario que permita caracterizar la integridad
estructural implica el uso de técnicas de ensayos no destructivos. Estas técnicas son a menudo
costosas y consumen mucho tiempo.
En la actualidad, muchas industrias buscan incrementar la confiabilidad de las estructuras que
emplean. Mediante el uso de técnicas de última tecnología es posible monitorizar las estructuras
y en algunos casos, es factible detectar daños incipientes que pueden desencadenar en fallos catas-
tróficos. Desafortunadamente, a medida que la complejidad de las estructuras, los componentes
y sistemas incrementa, el riesgo de la aparición de daños y fallas también incrementa. Al mismo
tiempo, la detección de dichas fallas y defectos se torna más compleja.
En años recientes, la industria aeroespacial ha realizado grandes esfuerzos para integrar los
sensores dentro de las estructuras, además de desarrollar algoritmos que permitan determinar la
integridadestructuralentiemporeal.Estafilosofíahasidollamada“StructuralHealthMonitoring”
(o “Monitorización de Salud Estructural” en español) y este tipo de estructuras han recibido el
nombre de “Smart Structures” (o “Estructuras Inteligentes” en español). Este nuevo tipo de estruc-
vii
turas integran materiales, sensores, actuadores y algoritmos para detectar, cuantificar y localizar
daños dentro de ellas mismas.
Una novedosa metodología para detección de daños en estructuras se propone en este trabajo.
La metodología está basada en mediciones de deformación y consiste en desarrollar técnicas de re-
conocimiento de patrones en el campo de deformaciones. Estas últimas, basadas en PCA (Análisis
de Componentes Principales) y otras técnicas de reducción dimensional. Se propone el uso de Re-
des de difracción de Bragg y medidas distribuidas como sensores de deformación. La metodología
se validó mediante pruebas a escala de laboratorio y pruebas a escala real con estructuras comple-
jas. Los efectos de las condiciones de carga variables fueron estudiados y diversos experimentos
fueronrealizadosparacondicionesdecargaestáticasydinámicas,demostrandoquelametodología
es robusta ante condiciones de carga desconocidas.
viii
PUBLICATIONS
Some ideas and figures have appeared previously in the following publications:
book chapters
• A Güemes and J Sierra. New Trends in Structural Health Monitoring, chapter Fiber Optic
265 316 2013
Sensors, pages – . Springer, .
conferences
• J Sierra and A Güemes. Detección de daño en materiales compuestos mediante fibra óptica
(inspanish).InActasdelIXCongresoNacionaldeMaterialesCompuestos(inspanish),pages
631 636 2011
– . Girona, Spain,
• A Güemes, J Sierra, J Rodellar and L Mujica. A robust procedure for Damage detection from
4
strain measurements based on Principal Component Analysis. In th Asia-PAcific Workshop
2012
on Structural Health Monitoring. Melbourne, Australia,
• JSierraandAGüemes.Damagedetectionatanaluminumbeamfromdiscreteandcontinuous
9
strain measurements. In th Intenation Workshop on Structural Health Monitoring. Stanford,
2013
United States of America,
• J. Sierra, A Güemes, and M Gómez. Sensibilidad de las variaciones en el campo de defor-
maciones en función de la aparición de daños en palas de aerogeneradores fabricadas en
13
materiales compuestos. In X Congreso Nacional de Materiales Compuestos MATCOM .
2013
Algeciras, Spain,
8
• J. Sierra and A Güemes. Damage detection in aerostructures from strain mesurements. In th
2013 2013
International Aerospace Supply Fair AIRTEC . Frankfurt, Germany, .
• J Sierra, A Güemes, E del Olmo and J Pintado. A robust procedure for damage identification
inalatticespacecraftstructuralelementbymeanofstrainfieldpatternrecognitiontechniques.
16 2014
In th European Conference on Composite Materials. Sevilla, Spain,
• J Sierra, A Güemes and M Gómez. Strain measurements and damage detection in large com-
16
positestructuresbyfiberopticssensors.In thEuropeanConferenceonCompositeMaterials.
2014
Sevilla, Spain,
• J Sierra, M-A Torres, G Cabanes, A Güemes, L Mujica and C-P Fritzen. Damage detection in
metallic beams from dynamic strain measurements under different load cases by using auto-
7
maticclusteringandpatternrecognitiontechniques.In thEuropeanWorkshoponStructural
2014
Health Monitoring. Nante, France,
• J Sierra, M-A Torres, A Güemes, L Mujica and C-P Fritzen. Structural health monitoring
6
of wind turbine blades from distributed strain measurements. In th World Conference on
2014
Structural Control and Monitoring. Barcelona, Spain,
ix
• M-A Torres, J Sierra, G Cabanes, A Güemes and C-P Fritzen. A pattern recognition approach
7
for damage detection and temperature compensation in acousto-ultrasonics. In th European
2014
Workshop on Structural Health Monitoring. Nante, France,
• M-ATorres,JSierra,JRodellarandC-PFritzen.Arobustmultivariatedata-drivenmodelling
6
approach for damage detection under variable temperature conditions. In th World Confer-
2014
ence on Structural Control and Monitoring. Barcelona, Spain,
journal papers
• J Sierra, A Güemes, and L Mujica. Damage detection by using FBGs and strain field pattern
2225011 25020 2013
recognition techniques. Smart Materials and Structures, : – ,
• A Güemes, J Sierra, J Rodellar, and L Mujica. A robust procedure for damage detection
from strain measurements based on principal component analysis. Key Engineering Mate-
558128 138 2013
rials, : – , .
• J Sierra and A Güemes. Damage detection in aerostructures from strain measurements. Air-
2013
craft Engineering and Aerospace Technology,
• J Sierra, A Güemes, L Mujica, and M Ruiz. Damage detection in composite materials struc-
tures under variable loads conditions by using fiber Bragg gratings and principal component
analysis, involving new unfolding and scaling methods. Intelligent Materials Systems and
2013
Structures,
x