Daniel Schmidt

Development of a Door Surround Structure with Integrated Structural Health Monitoring System

Structural health monitoring (SHM) based on Lamb waves, a type of ultrasonic guided waves, is a promising method for in-service inspection of composite structures. Lamb waves can be excited and received using a network of actuators and sensors, which are permanently attached to the structure. By analysing the sensor signals, different kinds of structural defects can be detected and located through the interaction of the Lamb waves. This paper presents the development and manufacturing of a full-scale composite fuselage panel with a door surround structure and integrated SHM system. The SHM system consists of piezoceramic sensor arrays, which are integrated into the composite manufacturing process in the form of semi-finished parts. With this approach, the manufacturing steps and costs can be reduced.

Virtual Sensors for SHM using Isogeometric Piezoelectric Finite Elements

Purpose – A design of sensor networks for structural health monitoring (SHM) with guided waves poses a hard challenge. Therefore different approaches are possible. A known one is the usage of probability of detection (POD) criteria. Here, areas of potential impact sensitivity are calculated for every sensor which leads to a POD. The number of sensors is increased until a demanded POD is reached. However, these calculations are usually based on finite element methods and underlie different assumptions and approximations which can cause different inaccuracies. These limitations are avoided by using an experimental data basis for virtual sensors in this paper. The paper aims to discuss these issues. Design/methodology/approach – An air-coupled ultrasound scanning technique is used for guided wave investigations. Recorded displacements of a structure surface are used as stimulation of virtual sensors which can be designed by software and positioned within available data field. For the calculation of sensor si...

Structural Health Monitoring Based on Guided Waves

Structural Health Monitoring (SHM) based on ultrasonic guided waves, so-called Lamb waves, is a promising method for in-service inspection of composite structures without time consuming scanning like conventional ultrasonic techniques. Lamb waves are able to propagate over large distances and can be easily excited and received by a network of piezoelectric actuators and sensors. In principle different kinds of structural defects can be detected and located by analyzing the sensor signals. The chapter describes recent research activities at DLR on Structural Health Monitoring. The research are focused on the visualisation of Lamb wave propagation fields based on air-coupled ultrasonic technique, the simulation of virtual sensors, mode selective actuators as well as manufacturing of actuator and sensor networks. Additionally, the chapter present the development of a SHM system for impact detection in a helicopter tailboom (Eurocopter—EC 135).

Characterization of mode selective actuator and sensor systems for Lamb wave excitation

Structural Health Monitoring (SHM) based on Lamb waves, a type of ultrasonic guided waves, is a promising technique for in-service inspection of composite structures. This study presents the development of mode selective actuator and sensor systems based on interdigital transducer (IDT) design. Various parameters such as wavelengths, number and apodization of electrodes as well as eigenfrequencies of the transducer are characterized. Therefore, an analytical model based on the theory of surface acoustic wave (SAW) filters is investigated in order to evaluate the acoustic response of the transducer. Furthermore, experimental tests on composite plates are performed.