Jochen H. Kurz

New approaches for automatic threedimensional source localization of acoustic emissions – Applications to concrete specimens

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 1m 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.

Condition Assessment of Civil Infrastructure in Europe: Recent Developments and What Might Be Ahead

Infrastructure is subject to continuous aging. This has given life-cycle management of the infrastructure an increasing role. Therefore, reliable inspection and monitoring tools are in increasing demand. The paper provides a short overview of the major activities in this area in Europe, followed by a presentation of current projects in the field of civil engineering in which topics related to combinations of nondestructive testing (NDT) methods and modular control and data acquisition approaches are discussed. In this paper, the two major construction materials in civil engineering, steel and concrete, are discussed. Regarding reinforced as well as prestressed concrete, a combination of various NDT methods is often required, which allow reliable results for material characterization, flaw detection, and the determination of component-specific geometry parameters. Therefore, a multisensor measurement approach with a high degree of automation is required. Two recently developed measurement devices (OSSCAR and BetoScan) will be described. Regarding steel constructions, an example from the field of pipeline inspection is shown where the combination of NDT with fracture mechanical assessment is directly possible. Both fields deliver the required interfaces in which the fracture risk is evaluated in probabilistic terms. Therefore, this procedure can be used as a tool for inspection-based lifetime conceptions. The paper concludes with an outlook on future trends for degradation monitoring.

Nondestructive Characterization of and Defect Detection in Timber and Wood

In order to detect defects and to increase the lifetime of timber structures nondestructive methods are developed to monitor and assess their condition. Timber and wood can be characterized nondestructively and in many cases contactless with diverse methods. This paper gives a short overview on some nondestructive methods based on electromagnetic effects: microwave/radar, nuclear magnetic resonance and X-ray techniques. To monitor the stress condition of the joints in timber structures some other techniques like micromagnetic methods, acoustic resonance analysis and ultrasonic stress analysis are to be considered.

Micromagnetic and Ultrasound Methods to Determine and Monitor Stress of Steel Structures

AbstractPrestressed constructions have been extensively used since the 1950s for infrastructure and large-span constructions. During maintenance renovation and after events causing damages, it is often important to know the current stress on the prestressed steel elements of the structure, such as strands or cables. Limited access can often be provided. Then a nondestructive assessment of the current stress is possible. However, several points have to be taken into account before micromagnetic or ultrasound testing methods can be used for determining the current stress value. For both methods, the determination of quantitative values requires a prior calibration. Micromagnetic measurements were performed with the micromagnetic multiparameter microstructure and stress analysis approach developed by Fraunhofer IZFP. It has different sensitivities for microstructure and stress state, but disturbing influences related to microstructure, geometrical effects, temperature, etc. also have to be taken into account...

QUANTITATIVE INTEGRATION OF NDT WITH PROBABILISTIC FRACTURE MECHANICS FOR THE ASSESSMENT OF FRACTURE RISK IN PIPELINES

In the context of probabilistic paradigm of fracture risk assessment in structural components a computer simulation rationale is presented which has at the base the integration of Quantitative Non‐destructive Inspection and Probabilistic Fracture Mechanics. In this study the static failure under static loading is assessed in the format known as Failure Assessment Diagram (FAD). The fracture risk is evaluated in probabilistic terms. The superposed probabilistic pattern over the deterministic one is implemented via Monte‐Carlo sampling. The probabilistic fracture simulation yields a more informative analysis in terms of probability of failure. The ability to simulate the influence of the quality and reliability of non‐destructive inspection (NDI) is an important feature of this approach. It is achieved by integrating, algorithmically, probabilistic FAD analysis and the Probability of Detection (POD). The POD information can only be applied in a probabilistic analysis and leads to a refinement of the assessment. By this means, it can be ascertained the decrease of probability of failure when POD‐characterized NDI is applied. Therefore, this procedure can be used as a tool for inspection based life time conceptions. In this paper results of sensitivity analyses are presented with the aim to outline, in terms of non‐failure probabilities, the benefits of applying NDI, in various qualities, in comparison with the situation when NDI is lacking. A better substantiation is enabled of both the component reliability management and the costs‐effectiveness of NDI timing.In the context of probabilistic paradigm of fracture risk assessment in structural components a computer simulation rationale is presented which has at the base the integration of Quantitative Non‐destructive Inspection and Probabilistic Fracture Mechanics. In this study the static failure under static loading is assessed in the format known as Failure Assessment Diagram (FAD). The fracture risk is evaluated in probabilistic terms. The superposed probabilistic pattern over the deterministic one is implemented via Monte‐Carlo sampling. The probabilistic fracture simulation yields a more informative analysis in terms of probability of failure. The ability to simulate the influence of the quality and reliability of non‐destructive inspection (NDI) is an important feature of this approach. It is achieved by integrating, algorithmically, probabilistic FAD analysis and the Probability of Detection (POD). The POD information can only be applied in a probabilistic analysis and leads to a refinement of the assessm...

CONTROL AND DATA ACQUISITION OF AUTOMATED MULTI‐SENSOR SYSTEMS‐TWO EXAMPLES FROM CIVIL ENGINEERING

A combination of different non‐destructive test methods is often necessary to receive reliable results for material characterization, flaw detection and the determination of component specific geometry parameters. Regarding structures of concrete thickness measurements are combined with flaw detection. Furthermore, additional information about reinforcement and tendon ducts is needed. Therefore, a multi‐sensor measurement approach is required with a high degree of automation. Otherwise a time consuming succession of manual measurements has to be performed. A modular control and data acquisition approach will be described and the application to two different automated measurement devices will be shown. These are results from two collaborative projects dealing with the development of an automobile robot system and a highly flexible scanner system. These different applications are based on a similar kernel allowing the modular use of different contact and non‐contact sensors. Therefore, continuous and point measurement devices can be combined and multiple sensor combinations are possible. This measurement approach leads to results in form of point data and time series. Furthermore, the coordinates of each measurement can be device dependent. Therefore, a flexible analysis concept is needed. Since often only a combination of several methods will lead to significant results the fusion of the analyzed data must also be possible. Several aspects as well as limits and future trends concerning analysis and also flexible data storage will be discussed.A combination of different non‐destructive test methods is often necessary to receive reliable results for material characterization, flaw detection and the determination of component specific geometry parameters. Regarding structures of concrete thickness measurements are combined with flaw detection. Furthermore, additional information about reinforcement and tendon ducts is needed. Therefore, a multi‐sensor measurement approach is required with a high degree of automation. Otherwise a time consuming succession of manual measurements has to be performed. A modular control and data acquisition approach will be described and the application to two different automated measurement devices will be shown. These are results from two collaborative projects dealing with the development of an automobile robot system and a highly flexible scanner system. These different applications are based on a similar kernel allowing the modular use of different contact and non‐contact sensors. Therefore, continuous and point ...