Fraunhofer Institute for Non-Destructive Testing
Dresden, Germany

The Fraunhofer Society is a German research organization with 67 institutes spread throughout Germany, each focusing on different fields of applied science . It employs around 23,000 people, mainly scientists and engineers, with an annual research budget of about €1.7 billion. Some basic funding for the Fraunhofer Society is provided by the state , but more than 70% of the funding is earned through contract work, either for government-sponsored projects or from industry.It is named after Joseph von Fraunhofer who, as a scientist, an engineer, and an entrepreneur, is said to have superbly exemplified the goals of the society.The organization has seven centers in the United States, under the name “Fraunhofer USA”, and three in Asia. In October 2010, Fraunhofer announced that it would open its first research center in South America.Fraunhofer UK Research Ltd was established along with the Fraunhofer Centre for Applied Photonics, in Glasgow, Scotland, in March 2012. Wikipedia.

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Waschkies T.,Karlsruhe Institute of Technology | Waschkies T.,Fraunhofer Institute for Non-Destructive Testing | Oberacker R.,Karlsruhe Institute of Technology | Hoffmann M.J.,Karlsruhe Institute of Technology
Acta Materialia | Year: 2011

Ice-templated structure formation of water-based suspensions was investigated from very slow (<1 μm s -1) to very fast (>100 μm s -1) solidification velocities by analysing the microstructural development in the frozen state and the green state. Maps for the microstructural development were established, showing transitions from planar to lamellar and lamellar to isotropic microstructure with dependence on particle size, solids content and solidification velocity. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Schubert L.,Fraunhofer Institute for Non-Destructive Testing
Structural Health Monitoring 2011: Condition-Based Maintenance and Intelligent Structures - Proceedings of the 8th International Workshop on Structural Health Monitoring | Year: 2011

This work investigates the interaction of guided waves with low-velocity impact damage in carbon fibre reinforced plastics (CFRP) which are widely used in aerospace applications. The interaction of guided-waves with impact induced damage was already shown [1-2], but the defect localization is quite difficult because of anisotropic material behavior [3]. An adapted synthetic aperture focusing technique (SAFT) was used for defect localization in such anisotropic materials. In order to utilize the technique for composite materials the wave velocities have to be known. The velocities of different wave modes in CFRPs vary with frequency, mode order and the propagation angle. They can be computed from the stiffness coefficients of the material solving equation of motion for anisotropic case [4] or by the conduction of pitch catch or laservibrometric measurements and the subsequent computation of the angle dependent propagation velocities. This paper shows examples for both the theoretical and experimental approach to obtain the lamb wave propagation velocities. In the experimental work, the velocity data obtained while using laservibrometric measurements are used by the localization algorithm. There for an anisotropic CFRP-plate was equipped with a network of distributed piezo disc transducers. Then a low velocity impact was introduced into the structure. The successful imaging of this damage will be demonstrated.

Frankenstein B.,Fraunhofer Institute for Non-Destructive Testing
Structural Health Monitoring 2011: Condition-Based Maintenance and Intelligent Structures - Proceedings of the 8th International Workshop on Structural Health Monitoring | Year: 2011

Lightning strike is one of the most frequently causes of defect for wind turbine rotor blades. Because of the tremendous magnetic inductions caused by lightning conductor current use of metallic wiring for communication and power supply is quite impossible. The work describes a monitoring system based on acoustic emission and acousto ultrasonic techniques combined with acceleration measurements for rotor blades. The sensors are distributed over the surface of the rotor blade and the Backbone for data transfer and power supply is realized by optical components. Monitoring techniques and technical realization of such a sensing network as well as first results of acoustic emission and acousto ultrasonic measurements in rotor blades will be presented. Challenges and solutions of such a monitoring system like sensor application, optical wiring, data collection and signal processing for the acoustic applications will be described.

Lieske U.,Fraunhofer Institute for Non-Destructive Testing
Proceedings of the 6th European Workshop - Structural Health Monitoring 2012, EWSHM 2012 | Year: 2012

For comprehensive fatigue tests and surveillance of large scale structures, a structural health monitoring system based on Lamb waves in kHz range was realized and tested. The system is based on a wireless sensor network and focuses especially on low power measurement, signal processing and communication. Thereby we met the challenge of synchronizing the wireless connected sensor nodes with sufficient accuracy. The sensor nodes were realized by compact, sensor near signal processing structures containing components for analog preprocessing of acoustic signals, their digitization, algorithms for data reduction 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. Each node in the sensor network can be used for Lamb wave excitation by an arbitrary waveform generator of about 40V peak-to-peak voltage. Four Sensor nodes where used to detect an artificial damage inside a CFRP plate.

Hiller J.,Technical University of Denmark | Maisl M.,Fraunhofer Institute for Non-Destructive Testing | Reindl L.M.,Albert Ludwigs University of Freiburg
Measurement Science and Technology | Year: 2012

This paper presents physical and metrological characterization measurements conducted for an industrial x-ray micro-computed tomography (CT) system. As is well known in CT metrology, many factors, e.g., in the scanning and reconstruction process, the image processing, and the 3D data evaluation, influence the dimensional measurement properties of the system as a whole. Therefore, it is important to know what leads to, and what are the consequences of, e.g., a geometrical misalignment of the scanner system, image unsharpness (blurring), or noise or image artefacts. In our study, the two main components of a CT scanner, i.e. the x-ray tube and the flat-panel detector, are characterized. The contrast and noise transfer property of the scanner is obtained using image-processing methods based on linear systems theory. A long-term temperature measurement in the scanner cabinet has been carried out. The dimensional measurement property has been quantified by using a calibrated ball-bar and uncertainty budgeting. Information about the performance of a CT scanner system in terms of contrast and noise transmission and sources of geometrical errors will help plan CT scans more efficiently. In particular, it will minimize the user's influence by a systematic line of action, taking into account the physical and technical limitations and influences on dimensional measurements. © 2012 IOP Publishing Ltd.

Szielasko K.,Fraunhofer Institute for Non-Destructive Testing | Mironenko I.,Saarland University
IEEE Transactions on Magnetics | Year: 2013

Micromagnetic materials characterization requires sensors which essentially consist of two critical elements: an electromagnet which introduces a well-defined magnetic field to the material, and a sensor system which detects the material's response to the applied magnetic field. The devices developed at Fraunhofer IZFP obtain a multiparametric 'magnetic fingerprint' with these sensors by means of several methods. The magnetic fingerprints of calibration samples are used as input for pattern recognition or regression analysis, thus allowing the prediction of mechanical-technological material characteristics (hardness, yield strength, etc.) or residual stress. This approach is called micromagnetic multiparameter microstructure and stress analysis (3MA). The long-term stability and reproducibility of the sensor and device characteristics are crucial for the reliability of the measured results. Therefore, the measuring hardware should follow a minimalistic approach. In this paper, we propose a way of simplifying the measuring hardware by multiple use of sensor elements, reducing the analog signal processing chain and transferring most signal processing tasks to the PC. © 1965-2012 IEEE.

Kurz J.H.,Fraunhofer Institute for Non-Destructive Testing
Ultrasonics | Year: 2015

The task of locating a source in space by measuring travel time differences of elastic or electromagnetic waves from the source to several sensors is evident in varying fields. The new concepts of automatic acoustic emission localization presented in this article are based on developments from geodesy and seismology. A detailed description of source location determination in space is given with the focus on acoustic emission data from concrete specimens. Direct and iterative solvers are compared. A concept based on direct solvers from geodesy extended by a statistical approach is described which allows a stable source location determination even for partly erroneous onset times. The developed approach is validated with acoustic emission data from a large specimen leading to travel paths up to 1 m and therefore to noisy data with errors in the determined onsets. The adaption of the algorithms from geodesy to the localization procedure of sources of elastic waves offers new possibilities concerning stability, automation and performance of localization results. Fracture processes can be assessed more accurately. © 2015 Elsevier B.V. All rights reserved.

Rosenkranz R.,Fraunhofer Institute for Non-Destructive Testing
Journal of Materials Science: Materials in Electronics | Year: 2011

The common Passive Voltage Contrast localization method in Focused Ion Beams and Scanning Electron Microscopes can be used for failure localization issues. These methods became widely accepted in the semiconductor failure analysis community. Nearly all labs make use of it. The Active Voltage Contrast method works with additional external voltages applied inside the chamber to certain structures at the sample surface and offers even more localization possibilities. A comprehensive overview over all phenomena related to Voltage Contrast generation is given and the multiple advantages, possibilities and limits of VC failure localization are systemized and discussed. © 2011 Springer Science+Business Media, LLC.

Lugin S.,Saarland University | Lugin S.,Fraunhofer Institute for Non-Destructive Testing
NDT and E International | Year: 2013

In this work a new approach/method for detection of hidden defects by lateral thermal flows is proposed. The method is based on propagation of the thermal wave in a lateral direction in the sample volume and observation of the surface thermal distribution. This approach allows to reveal the hidden defects/cracks which are not detectable by conventional thermal inspection methods. The experimental investigations were conducted on steel samples with the defects which do not satisfy the detection criteria empirically established for thermal methods. The defects were successfully revealed. The proposed technique has a high sensitivity to hidden structures and can be applied in industrial inspection procedures. © 2013 Elsevier Ltd.

Zschech E.,Fraunhofer Institute for Non-Destructive Testing
International Journal of Materials Research | Year: 2010

The scope of the Feature Articles of the special issue of Materials for Information Technology is to provide an overview of the existing status, developments, and research activities in the field of materials used for information technology (IT). The papers reflect the existing widespread interest in materials for IT and provide an insight into the directions in which new synthesis developments and special applications for these useful materials are expected to be used. The contents of the papers range from materials for field-effect transistors (FET) used in leading-edge silicon-based electronic products manufactured in complementary metal oxide semiconductor (CMOS) technology and materials for the nanoelectronics materials for data storage and for printed electronics. The papers also include topics on computer modeling and analytical techniques to characterize thin film structures.

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