In order to reduce the CO2-emissions and to increase the energy efficiency, the operating temperatures of power plants will be increased up to 720°C. This demands for novel high-performance steels in the piping systems. Higher temperatures lead to a higher risk of damage and have a direct impact on the structure stability and the deposition structure. Adequately trusted results for the prediction of the residual service life of those high strength steels are not available so far. To overcome these problems the implementation of an online monitoring system in addition to periodic testing is needed. RWE operates the lignite power plant Neurath. All test and research activities have to be checked regarding their safety and have to be coordinated with the business operation of the plant. An extra bypass was established for this research and made the investigations independent from the power plant operating. In order to protect the actuators and sensors from the heat radiated from the pipe, waveguides were welded to the bypass. The data was evaluated regarding their dependencies on the environmental influences like temperature and correction algorithms were developed. Furthermore, damages were introduced into the pipe with diameters of 8 mm to 10 mm and successfully detected by the acoustic method.
Structural health monitoring systems are increasingly used for comprehensive fatigue tests and surveillance of large scale
structures. In this paper we describe the development and validation of a wireless system for SHM application based on
The system is based on a wireless sensor network and focuses especially on low power measurement, signal processing
and communication. The sensor nodes were realized by compact, sensor near signal processing structures containing
components for analog preprocessing of acoustic signals, their digitization and network communication. The core
component is a digital microprocessor ARM Cortex-M3 von STMicroelectronics, which performs the basic algorithms
necessary for data acquisition synchronization and filtering.
The system provides network discovery and multi-hop and self-healing mechanisms. If the distance between two
communicating devices is too big for direct radio transmission, packets are routed over intermediate devices
The system represents a low-power and low-cost active structural health monitoring solution. As a first application, the
system was installed on a CFRP structure.
To operate wind turbines safely and efficiently, condition monitoring for the main components are of increasing
importance. Especially the lack of access to offshore installations increases inspection and maintenance costs.
The current work at Fraunhofer IZFP Dresden in the field of monitoring of wind turbines is focused on the development
of a condition monitoring system for rotor blades.
A special focus lies on the application of optical technologies for communication and power supply. It is not possible to
introduce electrical conductors into the rotor blade since it might cause tremendous damages by lightning.
The monitoring concept is based on a combination of low frequency integral vibration monitoring and acoustic
monitoring techniques in the frequency range between 10 and 100 kHz using guided waves. A joint application of
acousto ultrasonics and acoustic emission techniques will be presented. Challenges and solutions of such a field test like
sensor application, data handling and gathering as well as temperature variation are described.
The constant growth of air traffic leads to increasing demands for the aircraft industry to manufacture airplanes
more economically and to ensure a higher level of efficiency, ecology and safety. During the last years important
improvements for fuselage structures have been achieved by application of new construction principles,
employment of sophisticated and/or alternative materials, and by improved manufacturing processes. In
particular the intensified application of fibre-reinforced plastics components is in the focus of current discussions
The main goal of an ongoing national project is to improve the existing ultrasonic test technology in such a way
that it is optimally suited for the examination of CFRP multilayer structures. The B-Scan and C-Scan results are
then used for the visualization of individual layers and the complete layer set-up.
First results of the project revealed that with carefully selected transducers and frequencies it is possible to detect defects and irregularities in the layer structure like delaminations, fibre cracking, ondulations, missing layers etc. and even to visualize the fibre orientations in the individual layers.
Conventionally, modal monitoring of Wind Turbine Rotor Blades is primarily based on the evaluation of
eigenfrequencies. Beyond this, combining a sensor network with the Operational Modal Analysis (OMA)
method, mode shape and parallely a local component are utilized here. In addition it is expected that the
damping, which is also determined by the OMA method, will give a lead on damage development at the rotor
already at an early stage. Modal monitoring by means of measurement is combined with FEM simulation and
with the comparison of results obtained from measurement and simulation. Moreover, this will establish a
connection between the engineer and the design data of a rotor blade, which also are based on FEM analyzes.
A further significant increase regarding error resolution is possible by combining the global modal methods with
locally sensitive monitoring methods, based on guided elastic waves. These assume plate-like structures through
which elastic waves propagate in the low-frequency ultrasonic range (10 - 100 kHz) in certain modes. These
different wave modes interact distinctively with inner structural damages such as web fractures and
delaminations. It is differentiated between piezoelectrically excited waves (acousto ultrasonics), and waves
produced by energy released at fractures, delamination etc. (acoustic emission). Applying a moderate number of
sensors, the combination of both methods can allow an effective monitoring of the global structure.
The paper presents guided elastic waves and their identification and damage interaction in a CFRP plate. After the
excitation of a fiber transducer, different elastic waves emerge in a plate. By using specially developed 3D laser
scanning software it was possible to specify the different wave modes. These wave modes have been described
concerning their propagating velocities and different motion components. The interaction of different wave modes with
introduced impact damage (7J) is shown. In some experiments, it was proven that impact locations can be derived from
the detected Lamb waves. This work is continued to develop structural health monitoring systems (SHM) for selected
aircraft components (e. g. stringer elements, panels).