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The reliability of wheel set axle testing is of high importance because small discontinuities caused during manufacturing or rock fall impacts during operation might cause growing cracks during the operation load cycles. While most of the axles are tested by automated UT-systems today, the basic education of railway NDT operators is still manual testing providing the basic understanding and skills for the operators. In Germany it is a common rule that NDT operators in the railway branch need to refresh their knowledge and skills every five years including a refresh examination. The testing results from these exercises and from a parallel round robin test have been sampled at the DGZfP Railway Education Centre in Wittenberge for a period of about 5 years. The results of the operators written in test record sheets were compared with the “true” test crack or notch position in the axles used for examination. In this way the testing results could be categorized into “hits” and “misses” and the “hits” were further evaluated due to correct position and adequate amplitude height. Considering some thousand indications documented by the operators during the refresh examination and comparing transition bow, shaft and seat it was a highlight to see that the operators reach their best detection rate in the transition bow of the wheel axle set while this is often the most difficult part concerning the UT-echoes. Fortunately this is due to their raised awareness in the transition bow region because this is the most dangerous region with respect to fracture mechanics.
For two selected axles the experimental set up of 45° and 70° inward and outward UT-testing were also simulated showing clearly the difficulties of the UT-echoes detection of some specific test defects.
Der einwandfreie Zustand der Radsätze von Schienenfahrzeugen ist von größter Bedeutung für den sicheren Betrieb. Die Radsatzwellen werden durch eine große Zahl von Lastwechseln individuell unterschiedlich beansprucht. Dabei spielen viele Einflüsse wie äußere statische und dynamische Lasten, innere Lasten aufgrund von Unwuchten und inneren Spannungen und Umweltbedingungen entscheidende Rollen. Eine regelmäßige Prüfung ist daher obligatorisch. BTD entwickelt im Rahmen eines MNPQ-Projektes in Kooperation mit der BAM eine Phased Array Technik zur automatisierten Prüfung von Radsatzwellen im eingebauten Zustand. Die schwierigen Ankoppelbedingungen aufgrund der begrenzten Zugänglichkeit, der komplexen Geometrie sowie Farbschichten und Schmutz auf der Radsatzwelle stellen hierbei große Herausforderungen dar. Zu deren Bewältigung werden neben optimierten Prüfköpfen, einer in die Wasservorlaufstrecke integrierten akustischen Linse und einer speziellen Ankoppeltechnik auch Signalverarbeitungsalgorithmen eingesetzt. Die Darstellung der Signalverarbeitung ist der Schwerpunkt dieses Beitrages. Mit Hilfe von Messdatensätzen präparierter Testwellen werden verschiedene Algorithmen erprobt und hinsichtlich der Stabilität, dem Verhalten bezüglich der Ankoppelschwankungen und veränderter Wellengeometrien und der Fähigkeit zur automatischen Unterscheidung von Fehler- und Formanzeigen bewertet. Letztlich wird die beste Lösung im entwickelten Prüfsystem eingesetzt.
Presentation on recent progress in ultrasinic testing and monitoring of concrete for massive structures. First, a new instrument (LAUS) for ultrasonic echo testing of thicknesses up to 5 m is shown. A new method to provide better images of the concrete interior, Reverse Mitem Migration (RTM)is presented. Second, the use of embedded ultrasonic transducers and data processing methods borrowed from seismology to detect subtle changes in concrete are documented.
The presentation will give an overview on non-destructive testing techniques being developed at the Federal Institute for Materials Research and Testing, Germany (BAM). This includes ultrasonic methods, ground penetration radar, Laser-Induced Breakdown Spectroscopy (LIBS), infrared thermography, pile testing, sensor technology and building scanner. A focus of the talk will be ultrasonic methods, which are well established in various aspects of concrete testing. They are used for imaging the interior geometry of constructions, estimation of concrete strength or monitoring lab investigations. However, so far the detection of distributed damages, especially in an early stage, has been almost impossible. The arrival of new technologies as embedded transducers and sensitive data processing techniques adopted from seismology has opened new field of work. Recent research has been focused to detect changes in concrete elements induced by stress, temperature, moisture or chemical attacks by permanent monitoring. Techniques as Coda Wave Interferometry can resolve changes in ultrasonic velocity in the order of 1*10-5. In addition, many researchers believe that the investigation of nonlinear effects can be used to characterize damages. The presentation will give a wrap up of ultrasonic techniques currently used in practice. This will include echo based methods as multi-channel/multi-offset imaging of structural elements using commercial and prototype devices. Imaging methods as SAFT and RTM will be shortly discussed. The focus will be on the emerging techniques used for monitoring. New types of sensors will be presented as well as the devices used in laboratory and field applications. Insight will be given on the various influence factors on ultrasonic signals and various ways of feature extraction and data processing. The results of lab experiments will be shown to demonstrate the detection of various kind of damages from mechanical load, ASR, corrosion to fatigue. The experiences with our first installations in real constructions (bridges, tunnel) will also be presented.
Concrete is known to be a very useful, flexible and durable construction material. However, due to excess load, fatigue, chemical processes, freeze-thaw or reinforcement corrosion concrete may suffer from degradation. If detected too late, repair is difficult and expensive.
The propagation of ultrasonic waves is influenced by changes in the properties and structure of the material, including, but not limited to, stress, temperature, moisture content and microcracking. Ultrasonic velocieties thus may serve as indicators for structural health. Traditional ultrasonic methods as transmission time of flight measurements are used since decades, but are not sensible enough to show subtle changes. Coda Wave Interferometry (CWI), originally developed in seismology to detect stress changes in the earth's crust uses the information in the late part of ultrasonic signals originating from multiple reflections and scattering. Since a few years it is used by several researchers for lab experiments on concrete.
Meanwhile specialized sensors to be embedded in concrete have been developed. We have conducted several lab and a few field experiments, which will be reported here. The capabilities and limitations of CWI are summarized.
Ultrasonic methods are well established in various aspects of concrete testing. They are used for imaging the interior geometry of constructions, estimation of concrete strength or monitoring lab investigations. However, so far the detection of distributed damages, especially in an early stage, has been almost impossible. The arrival of new technologies as embedded transducers and sensitive data processing techniques adopted from seismology has opened new field of work. Recent research has been focused to detect changes in concrete elements induced by stress, temperature, moisture or chemical attacks by permanent monitoring. Techniques as Coda Wave Interferometry can resolve changes in ultrasonic velocity in the order of 1*10-5. In addition, many researchers believe that the investigation of nonlinear effects can be used to characterize damages. The presentation will give a wrap up of ultrasonic techniques currently used in practice. This will include echo based methods as multi-channel/multi-offset imaging of structural elements using commercial and prototype devices. Imaging methods as SAFT and RTM will be shortly discussed. The focus will be on the emerging techniques used for monitoring. New types of sensors will be presented as well as the devices used in laboratory and field applications. Insight will be given on the various influence factors on ultrasonic signals and various ways of feature extraction and data processing. The results of lab experiments will be shown to demonstrate the detection of various kind of damages from mechanical load, ASR, corrosion to fatigue. The experiences with or first installations in real constructions (bridges, tunnel) will also be presented.
Ultrasonic methods are well established in various aspects of concrete testing. They are used for imaging the interior geometry of constructions, estimation of concrete strength or monitoring lab investigations. However, so far the detection of distributed damages, especially in an early stage, has been almost impossible. The arrival of new technologies as embedded transducers and sensitive data processing techniques adopted from seismology has opened new field of work. Recent research has been focused to detect changes in concrete elements induced by stress, temperature, moisture or chemical attacks by permanent monitoring. Techniques as Coda Wave Interferometry can resolve changes in ultrasonic velocity in the order of 1*10-5. In addition, many researchers believe that the investigation of nonlinear effects can be used to characterize damages.
The workshop will give a wrap up of ultrasonic techniques currently used in practice. This will include echo based methods as multi-channel/multi-offset imaging of structural elements using commercial and prototype devices. Imaging methods as SAFT and RTM will be shortly discussed.
The focus will be on the emerging techniques used for monitoring. New types of sensors will be presented as well as the devices used in laboratory and field applications. Insight will be given on the various influence factors on ultrasonic signals and various ways of feature extraction and data processing. The results of lab experiments will be shown to demonstrate the detection of various kind of damages from mechanical load, ASR, corrosion to fatigue. The experiences with or first installations in real constructions (bridges, tunnel) will also be presented.
The presentation will give an overview on non-destructive testing techniques being developed at the Federal Institute for Materials Research and Testing, Germany (BAM). This includes ultrasonic methods, ground penetration radar, Laser-Induced Breakdown Spectroscopy (LIBS), infrared thermography, pile testing, sensor technology and building scanner. A focus of the talk will be ultrasonic methods, which are well established in various aspects of concrete testing. They are used for imaging the interior geometry of constructions, estimation of concrete strength or monitoring lab investigations. However, so far the detection of distributed damages, especially in an early stage, has been almost impossible. The arrival of new technologies as embedded transducers and sensitive data processing techniques adopted from seismology has opened new field of work. Recent research has been focused to detect changes in concrete elements induced by stress, temperature, moisture or chemical attacks by permanent monitoring. Techniques as Coda Wave Interferometry can resolve changes in ultrasonic velocity in the order of 1*10-5. In addition, many researchers believe that the investigation of nonlinear effects can be used to characterize damages. The presentation will give a wrap up of ultrasonic techniques currently used in practice. This will include echo based methods as multi-channel/multi-offset imaging of structural elements using commercial and prototype devices. Imaging methods as SAFT and RTM will be shortly discussed. The focus will be on the emerging techniques used for monitoring. New types of sensors will be presented as well as the devices used in laboratory and field applications. Insight will be given on the various influence factors on ultrasonic signals and various ways of feature extraction and data processing. The results of lab experiments will be shown to demonstrate the detection of various kind of damages from mechanical load, ASR, corrosion to fatigue. The experiences with our first installations in real constructions (bridges, tunnel) will also be presented.
To increase inspection speed and inspection reliability the use of phased array system is a superior solution. Especially for shaft inspection phased array setups are commonly used. For hollow axle inspection typically a number conventional probes rotating through the axles drilling are applied, without demounting the axes and without dismantling the wheels and the brake discs.
A new approach using a cone type array operated in immersion technique will allows to increase inspection speed and reduce the mechanical effort of the inspection system by rotating the sound field for the circumferential scan electronically. Only a linear movement of the probe is necessary to move the phased array cone forward and backwards inside the drilling. By applying additional focal laws the beam can be inclined exactly and be focused in the plane vertical to the specimen axis to concentrate the sound in the zones close to the external surface of the railway axle.
The cone type phased array probe has been optimized to detect transversal flaws in and close to the outer surface of the hollow axle, whose surface lies in the radial-radial plane.
The prototype probe system and its performance will be presented.