**6. Reliability of monitored engineering systems**

The reliability of any designed engineering system is a major concern. Due to the uncertainty inherent in several types of loads and the randomness in material properties, complete safety is not possible to attain. There is always a certain probability of failure that is associated with any designed engineering system. It is only important to ensure that such probability of failure is acceptable in terms of the nature of application at hand. Furthermore, it is important to be able to evaluate such probability and thus relate that to the reliability of any designed system.

The integration of structural health monitoring, within an engineering system, is expected to enhance its reliability. It is important to consider the reliability, of such system, in two main levels, the first is the reliability of the structural health monitoring system itself and the second is the reliability of the monitored engineering system as a whole, including the health monitoring enhancement. There is not enough research activity in the area of reliability of structural health monitoring systems and their impact on the reliability of monitored systems. This requires a targeted research effort in this area which would support the practical implementation of such systems, especially when dealing with the conservation of historic cultural heritage.

## **7. Summary**

*Advances in Structural Health Monitoring*

**3. Smart structural health monitoring**

**4. Conservation of historic cultural heritage**

would be inconsistent with current practices.

would ensure the safety of the historic structure.

**5. Advanced damage assessment techniques**

and optimum system, smart in the sense that the system can detect damaged components, independently, and can propose recommendations to safeguard against any potential failures; reliable in the sense that such early detection of damage and the resulting recommendations of preventive maintenance activities would directly improve the reliability of engineering systems; and finally, optimum in the sense that such integrated smart systems would result in designs that ultimately would

Structural health monitoring has gained an increased interest and research activity over the past two decades. By definition structural health monitoring comprises four main tasks, namely, damage identification, damage localization, damage severity evaluation, and structural system life expectancy prognosis. All current research activities are concentrating on the first two tasks, i.e., damage identification and localization. The continuous developments and evolutions in the applications of smart materials and technologies lend themselves to ample applica-

Smart structural health monitoring systems are the ones that employ smart materials in designing their sensor networks and/or smart technologies in designing their diagnostic and inference systems. In light of the broad definition of sustainable design, presented earlier, such a smart health monitoring system, when integrated with any given structural system, would result in a sustainable engineer-

Historic cultural heritage structures formulate the collective identity of a nation. It is the responsibility of current generations to ensure their safety and integrity in order to be safely maintained for future generations. This includes any conservation and/or retrofitting activities that might be required. It is expected that such structures would pose a unique challenge in that regard due to their age and the extreme environmental conditions they faced over the years. Another significant challenge is the materials used in their construction and the structural systems which in general

The introduction of structural health monitoring, as a conservation tool for such structures, is a state-of-the-art concept that would address most of the identified challenges, presented above. Structural health monitoring systems could be designed to integrate with such historic structures, thus, providing real-time monitoring mechanisms that can detect any damages, as they develop. Such early identification would ensure the timely introduction of maintenance activities that

Damage identification is the major function of any structural health monitoring system. There is a wide range of damage assessment methods and techniques that have been employed in the published health monitoring applications. With the development of smart materials and advanced technologies, new damage assessment techniques are introduced every day. Some of these techniques could

require less materials, less maintenance, and less failure occurrences.

tions in the development of smart structural health monitoring systems.

**2**

ing system.

The previously presented concepts are some of the new advancements in the design of structural health monitoring systems. It is envisaged that such advancements would lead to smart structural health monitoring that would result in sustainable engineering systems. Sustainability is considered an important objective in today's engineering design that is realized due to the current state of climate change and global warming, which are hugely aggravated by industrial and construction activities. It is intended through the chapters of this book to present demonstrations of and applications for such new advancements in order to encourage further research and implementation of such advanced techniques and technologies in structural health monitoring.

*Advances in Structural Health Monitoring*

Chapter 2

Abstract

the system.

1. Introduction

5

engine health management

Yoann Hebrard

Structural Health Monitoring

Providing the best availability of aircrafts is a key driver in aeronautics industry.

Based on nondestructive testing (NDT) technologies, systems known as structural health monitoring (SHM) make it possible to anticipate the deteriorations of a structure to avoid accidents. Associated with statistical processing systems, they also make it possible to optimize product life while reducing maintenance costs. The technologies of structural health monitoring, or SHM, meet the requirement of maintaining the quality of products over time. Their main objective is to ensure the health of structures, extend their life, anticipate their failures, and enhance their performance. The SHM is therefore for the industry part of a strategy link to

The SHM approach is indeed both a set of processes and a control strategy [1–3].

It consists of monitoring continuously or at regular intervals the integrity of a structure by detecting cracks or alterations, such as delamination of composite materials. The proposed solutions generally include sensor networks, for example,

piezoelectric or optical fiber type, coupled to signal processing systems.

Monitoring system able to detect signs of failure before they happen, thanks to sensors and diagnosis/prognosis algorithms, is key for improving aircraft operability. Since a suspension system is connecting the engine to the aircraft, after hard landing, aircraft companies need to know if the suspension system is safe or could have been damaged. This chapter presents an autonomous wireless load sensing recorder development that will enable maintenance operators to make a relevant diagnosis of the suspension system by measuring the load level seen after a hard landing by connecting a portable device near the embedded sensor system. The sensor integrates energy harvesting and RFID communication modules that have been developed for this application. Data acquisition is performed by an embedded microcontroller connected to sensors. The paper is firstly dedicated to the different energy sources available in the project application (engine pods). The second part gives a presentation of the various devices developed for converting ambient energy into electric power and SHM system. The last part presents real measurement of ambient energy level from real tests in comparison to the energy needed to power

from Sensing to Processing

Keywords: SHM, wireless sensor, RFID, energy harvesting,

economical, commercial, and safety drivers.
