Über die Fehlerauffindbarkeit als Hauptforderung an die zerstörungsfreie Werkstoffprüfung

About the Detection of Imperfections as a Main Task for Nondestructive Testing The inspection uncertainty is identified which is a measure of the difference between the size of imperfection that has a high probability of being passed and the size of imperfection that has a high probability of being rejected by an inspection. Reduction of the inspection uncertainty is the only means by which one can reduce inspection errors as the acceptance of defective material units and the rejection of sound material units. The discussion is presented within a framework that allows a quantitative evaluation of the quality of the material units that pass an inspection and a determin ation of the rejection rate. Analysis of the causes of inspection uncertainty is essential to efficient strategies for improving nondestructive inspection capabilities.     

Adaptive Werkstoffsysteme und ihre zerstörungsfreie Charakterisierung

Adaptive material systems and their non‐destructive characterisation Smart materials based on carbon fiber‐reinforced plastics with embedded piezoceramic sensors and actuators are expected to be a favorite composite for vibration damping and noise reduction. Due to the wide variety of physical properties of the components various damage mechanisms may reduce the sensing and actuating capabilities of the piezoceramic material. Comprehensive non‐destructive characterization and integral health monitoring help to optimize the structure and its manufacturing and are an essential prerequisite to ensure performance and availability of smart components during their life time.     

Anwendung der holografischen Interferometrie in der zerstörungsfreien Werkstoffprüfung

Usage of Holographic Interferometry for Non-Destructive Materials Testing . Holographic interferometry has meanwhile developed into a usable method for non-destructive materials testing, which permits even large-area components to be tested by using high-power lasers. Recording the fringe structures makes a subsequent detailed resolution evaluation possible. Appraisal of the video recordings makes the origin and change of the secondary interference fringes clearly recognizable and interpretable and thus substantiates very informatively the introduction of holographic interferometry for non-destructive materials testing.     

Lasertechnik in der zerstörungsfreien Werkstoffprüfung — ein neues holographisches Verfahren

Non-destructive Testing by Laser Measuring Techniques — A New Holographic Method . Holographic Non Destructive Testing is well suited for materials with a low elasticity modulus or bad heat conductivity, like rubber, metal-rubber-connections, adhesive connections, plastics, and fiber-reinforced plastics. The advantage of holographic testing lies in the fact that a near to true stress is possible. This stress occurs with only a fraction of the force necessary to damage the part. In many cases there is a relation between the holographic evidence and the breaking limit. By a new method the evaluation of the holograms is much more easier, because only objects with defects are showing deformation fringes.     

Schallemissionsuntersuchungen an polymeren Verbundwerkstoffen. Teil I: Das Schallemissionsmeßverfahren als quasi-zerstörungsfreie Werkstoffprüfung

Acoustic Emission Monitoring of Polymeric Composite Materials. Part I: The Technique of Acoustic Emission Monitoring The importance of nondestructive testing methods increases in material and structure production control techniques as well as in the practical, calculated usage of faulty structures. The technique of acoustic emission is a useful aid in monitoring complex structures in real time mode. In Part I the fundamental measuring technique of this testing method is discussed.     

Zur Problematik der zerstörungsfreien Materialprüfung

Problems of Non-Destructive Testing [NDT]. It is the main aim of NDT, to look for symptoms, being qualitatively reliable, and characteristics, being quantitatively evaluable, of voluminous flaws, discontinuities and other imperfections, and to do this without any damage of the workpiece. If defects or imperfections are detected, in addition to that, a statement about their actual importance and their avoidance in future must be given. In combination with that, conclusions about kind, conditions, and, consequently, about properties of processing and practical use of the inspected material must be drawn, either from the workpiece itself or from specially required specimens, but again without any damage, i. l. the specimens remaining applicable for other investigations. The real problems of nondestructive inspection of materials and components are — besides from reliable further development of inspection methods — the combination of test result with result of stress analysis, related to properties and stress of the inspected material. A systematical survey of possibilities of destructive and nondestructive materials testing may be helpful to find a solution of these problems.     

Ein umfassendes Gerätesystem für die zerstörungsfreie,elektromagnetische Werkstoffprüfung. — Einflüsse auf das Prüfverfahren sowie die Möglichkeiten der Störgrößen-Unterdrückung

Equipment for nondestructive electromagnetic Testing A system of eddy-curvent-appliances for non destructive testing is presented to the export; it is to adapt for different demands in buildingblock fashion. The mode of operation is discussed; the possibilities of defect-discrimination and suppression of interference are demonstrated.     

Zerstörungsfreie Prüfung von Tiefspaltschweißnähten mittels Durchstrahlung und Ultraschall

Non destructive testing of Narrow-Gap welded joints using radiographic and ultrasonic methods . The intensified demand for economical sources of electrical energy has led to nuclear power plants with increasingly larger pressure vessels, particularly for BWR and PWR installations. The wall thicknesses of these vessels now exceeds 200 mm. The fabrication of these heavy structural components to close construction tolerances has required the development of economic welding processes, which in general are fully mechanised. One such process which has been successfully applied to the joining of heavy sections is Narrow-Gap welding. Investigations on Narrow-Gap welded joints using conventional nondestructive testing methods, such as radiographic and ultrasonic methods, have revealed that weld defects in these weld seams can be readily determined since for this process, the possible zones of weld failures are clearly defined over a very small region. The assessment of the test results according to accepted standards for pressure vessel construction has revealed, that providing the welding conditions are carefully controlled, acceptable weld quality is ensured.     

Messunsicherheit in der Werkstoffprüfung

Measurement uncertainty in testing of materials For the testing of materials the respective uncertainty has to be indicated for each measured value. From the 1995 published GUM [1] 2000 the Uncert report for different measuring methods was developed and published as Code of Practice (COP) [2–4]. These are to be represented in connection with the procedures recommended in the standards and the practical implementation.     

Die Relativierung des Spannungsbegriffes in der zerstörenden Materialprüfung

Relativity of the notion “stress” in destructive materials testing. Later developments of certain important fields in destructive testing can be correlated with the modification undergone by the notion of stress in its practical application: In connection with highly elastical and plastical deformation this notion becomes more and more relative because of its dependence on the time scale of the test; in the field of random loading the idea of a maximum tolerable stress has to be replaced by the algorythmic handling of irregular loading histories; in fracture mechanics stress can no longer be considered independently and has to be linked to influences of local distortions. Both random fatigue and fracture mechanics can by no means be regarded as entirely solved problems. Some directions are discussed in which the answers to open questions might be found. Some consequences for the conception of new testing equipment are mentioned.     

Werkstoffprüfung von Hochleistungskeramik mit Zugproben

Mechanical testing of high-performance ceramics with tensile specimens Mechanical properties of engineering ceramics are often measured in bending. The principal limitations of these tests are discussed for linear-elastic and plastic material behaviour. From this the requirement of tensile tests is derived. For room temperature fatigue tests an optimized concept of gripping round specimens is presented. High temperature tests are performed with flat specimens allowing static and quasistatic experiments with continuous strain measurement up to ca. 1400 °C. For sintered silicon nitride tensile creep curves are reported and compared with results from bending tests.     

Probleme der zerstörenden Prüfung von Proben mit sehr geringer Verformung

Problems of Destructive Testing of Samples with Very Low Deformation In the case of materials with very low deformation at break, for example ceramics and graphite, the stiffness of the testing machine has to fulfill requirements which must be clearly defined and capable of being checked, in order to avoid errors in the test result. Besides sensitive test factors there are also some which remain constant regardless of the spring stiffness of the testing apparatus. The effect on the commonly used loading methods (v_o = constant; \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm F}\limits^. = {\rm constant} $\end{document}) is investigated. Possibilities for corrections are discussed an appropriate algorithms are given.     

Oberflächentastschnitte als Hilfsmittel der Werkstoffprüfung

Material Testing by Means of a Stylus-Type Roughness Tracing Instrument . Our experiments and a literature of survey show the various possibilities and limits of surface roughness measurements by means of the stylus-type roughness tracing method. Through direct or, by applying an imprint technology, through indirect surface tracing on materials such as metals, plastics including coatings and lacquers (duromers, plastomers, elastomers), wood, paper, asbestos sheets, textiles and coal a connection with the properties of the materials with respect to wear, sealing and contact, roughness of fracture surfaces, material testing, surface roughness of an injection mould, process and machining, corrosion, damage analysis, optical aspect, writing pressure curves, cracking etc. has been illustrated. Two examples from the medicine (dermal and dental medicine) underline the broad range of application possibilities. In many cases the stylus-type roughness tracing method is a secondary, however, generally very informative indirect testing method. Only in some cases it is in direct connection with a certain property of material such as the surface gas tightness of asbestos sheets. The limits of the stylus-type roughness tracing method are further determined by the method of measurement (stylus pressure, radius of stylus, curvature, stylus system).     

Der Beitrag der zerstörungsfreien Prüfung zur Zuverlässigkeit und Verfügbarkeit korrosionsgefährdeter Komponenten von Chemieanlagen

The part of Nondestructive Testing of Ensure Reliability and Availability of Components of the Chemical Process Industry under Corrosive Conditions Corrosion and wear failures very often are initialized or at a minimum influenced by faults in design, manufacturing and installation. If we reduce these faults, the result will be an increasing working life of the components. To solve this problem, we recommend the consequent use of NDT-techniques.     

Werkstoffprüfung mit der Schallemissionsanalyse (SEA)

Non-Destructive-Testing by Acoustic Emission . After the discussion of the physical principles and the experimental procedures of acoustic emission (a. e.) techniques, numerous examples of its applicability and capability are presented. These concern: plastic deformation of metals (ferrous- and non-ferrous-), crack-formation during heat treatment for stress-relief, crack-formation during cyclic loading, control of weld-processes, stress-corrosion cracks and finally microcrack formation in different fibre-reinforced composite materials. Advantages and disadvantages of a. e. are compared with those of other n. d. t.- methods.