Untersuchungen zur Größenbestimmung von Korrosionsrissen bei der manuellen Ultraschallprüfung

Investigations to Determine the Size of Corrosion Cracks For determining the size of corrosion cracks with ultrasound a multifrequency test method is described. By applying this procedure corrosion cracks of a size smaller than 2 mm are correctly evaluated independent of their position and of the reflection factor. Examples are presented and discussed for some practical applications.     

Ultraschallprüfung an Faserverbundkunststoffen Grundlagen,Methoden der bildhaften Darstellung und Ergebnisse

Ultrasonic Testing of Composites Foundations, Methods of Imaging and Results Modern materials such as composites are more and more used for aircraft and space structures and in mechanical and automotive engineering. Therefore quality control of these materials is of increasing importance. The high resolution computer controlled ultrasonic testing technique in the frequency range of 1 to 100 MHz is able to inspect and to analyse even components with complex geometry. This report gives the foundations and clearly presents the possibilities of reports with A-, B-, C- and D-scans. For test pieces not only CFRP-specimens with a thickness range of 2 to 24 mm and with artificially inserted defects were used, but also devices of the mechanical engineering.     

Prüfung und Ausbesserung von Apparateemaillierungen

Testing and Repair of Glas enameled Apparatus The test-methods used for examination of the quality of glas enameled apparatus are described. In the second part of this article the procedures for repair of enameled coatings in the chemical industry are presented.     

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.     

Bruchmechanische Prüfung von Keramiken mit R-Kurvenverhalten

Fracture Testing of Ceramics with R-Curve Behaviour Significant improvements of the fracture toughness are striven for ceramic materials using micromechanical mechanisms of crack tip shielding. The application of Fine Ceramics to structures and engines is planed increasingly in expectancy of higher strength. The aim of the article is the verification of common brittle fracture tests employed for advanced ceramics. Theoretical aspects of the R-curve behaviour are analysed to feature reliably damage of materials. Stable crack growth and failure of standard specimens are assessed using theoretical simulations of experiments. The results are compared with real data. Suggestions are made to interpret properly measurements and to select appropriate specimen geometries for materials which show a distinctive R-curve behaviour.     

Verschleißprüfung und Verschleißverhalten von Hartmetallen

Wear testing and wear behaviour of cemented carbides Wear resistance is not a mater constant but a quantity of a system. For the judgement of a case of wear or for the choice of the suitable grade of cemented carbide it is necessary to investigate exactly the limiting conditions and the appearance of wear. The wear test can only be considered with exactly defined limiting conditions and only be compared with application of similar limiting conditions.     

Vorrichtung zur Prüfung von Feinblech unter Druckbeanspruchung

Jig for testing thin sheet under compression load The experimental determination of the stress strain relation of thin sheet under uniaxial compression load is difficult, because the specimen are thin‐walled. A jig for testing thin sheet under uniaxial compression load and reversed tension‐compression load as well is presented in this article. It is shown, that in the relevant cross section an uniaxial stress state is dominating, which is not effected by the devices for lateral support. This jig gives the possibility to determine material properties, which are important for the manufacturing process and for the design of thin‐walled building components and verify valid assumptions.     

Zeitstandprüfung von Polypropylen bei 120 °C

Long Term Creep Tests of Polypropylene at 120 °C The mechanism of damage in the pipe wall during the internal pressure creep test of polypropylene-pipes at a test temperature of 120° is described. The resulting consequences from the investigations relating to the test method are shown and a test station with automatic recording of the time of damage is presented. Further on solutions are explained to eliminate the security risks during the tests of big pipes. A practical performance is described. On the basis of the time-temperature-correlation of the long term behavior of polypropylene the mathematical basis to interpolate minimum requirements for quality control are presented.     

Einsatz von Heißleiter-Temperaturfühlern in der Werkstoffprüfung

Application of Semiconductor Temperature Sensors in Material Testing So called Negative Temperature Coefficient (NTC) resistors whose electrical conductivity increases rapidly with increasing temperature have arisen as a by-product of semi-conductor development. This change in electrical resistivity makes the NTC-resistor — also known as Thermistor — suitable for exact temperature measurement. Because of its high resolution and small dimensions, it can be successfully used where maximum accuracy is required and point measurement is necessary. Possible applications are in material testing etc.     

Anwendung und Prüfung von Kitten im Säureschutzbau

Application and Testing of Mortars for acid-proff Construction Acid-proof ceramic materials are used to protect the surface of chemical equipment, tanks and sections of plants and buildings. Bricks and tiles are bedded in resin-based or silicate mortars. The field of application of those mortars is described. Especially the following guideline gives rules for a uniform determination of mechanical and other physical data of mortars for acid-proof construction.     

Zur Prüfung der Weichlötbarkeit von metallischen Halbzeugen

Testing of soft-soldering properties of semi-manufactured metals . Suitable for carrying-out solderability tests of semimanufactured metals, especially of strips or sheets made of copper alloys, a simple apparatus has been developed, which permits the determination of the “critical immersion rate”, i.e. the immersion rate of a specimen with defined dimensions, at which a complete wetting with molten tin still occurs. The results obtained with this apparatus are reproducible and suitable for the assessment of the soft-soldering properties of materials to be soldered.     

Langzeitprüfung von Schweißverbindungen aus Polyethylen bei komplexer Beanspruchung

Long Term Testing of Welded Joints from HDPE under Complex Loading Test methods to determine the long term weld-factors for heated tool butt weldings, extrusion weldings and hot gas weldings are presented. Instead of tensile bars welded pipers are tested under internal pressure to abbreviate the test times. The results of long term creep tests with welded and unwelded PE-HD pipes under the influence of several fluids are also discussed.     

Berührungslose Prüfung von Kunststoffen mittels photothermischer Wärmewellenanalyse

Remote Testing of Polymers with Photothermal Analysis of Thermal Waves After an introduction to thermal waves a comparison is made of photoacoustic detection methods (gas cell, piezoceramic) and photothermal detection arrangements (front surface and rear surface methods). Previously only photoacoustic methods have been applied to polymer related problems, while the advantages of photothermal measurements – remote and nondestructive evaluation – have been demonstrated on metals. The experimental part of this paper presents first steps to apply photothermal analysis of thermal waves to some problems of polymers: thickness measurement of thin layers; on-surface and subsurface defects; delamination of bonding and coating curing reactions; glass fibre content; orientation of fibres and molecules; aging processes. The present results indicate that the method can be used for nondestructive remote quality assurance of thin layers and foils. Further development is required to apply the method to nondestructive testing of thick walled components.     

Druckversuch an Scheiben zur Prüfung der Wasserstoffversprödung von Metallen

Disc-Pressure-Testing of Hydrogen Embrittlement An apparatus for disc-pressure-tests is presented. The bursting pressure with helium and with hydrogen is measured versus the rate of pressure increase. Under hydrogen most metals show a distinct minimum of bursting pressure. Some explanations for this minimum are proposed. The maximum ratio of bursting pressures x = (P_He/H_H2)_max is taken as an indicator for hydrogen embrittlement. Steel similar to SAE 4137 (34 CrMo 4) is tested in several states (tempered, normalized, cold-rolled), as well as austenitic steel, various other metals (V, Nb, Ta, Mo) and some amorphous metals. The disc-pressure-test is shown to be easy and useful for determining hydrogen embrittlement. Even austenitic steel exhibits some embrittlement (x = 1.5). The strongest embrittlement occurred in amorphous metal Vitrovac 0040 with x = 9.8.     

Dichtheitsprüfung

Leakage Tests — Flexible packaging in food processing and pharmaceutical industry Extended storage life for food products or better protection against environmental influences increases the demand for more accurate leak detection methods. Flexible, and therefore more fragile packaging is even more complicated when it comes to the commonly required non destructive leak testing. The main focus when testing flexible packaging is on welded seams. They represent the weakest point in flexible packaging. Today, there are several leak detection methods used to perform tests on flexible packaging. The most common ones are waterbath, pressure/vacuum decay and tracer gas based leak detection. All of which have their strength and weaknesses wheras the desired reject leak rate is mostly influencig the decision process. To measure very small leaks (<10 μ oder 10^‐5 mbar l/s) or to enable very short test cycles, trace gas leak detection is the way to go. On top of high accuracy, tracer gas leak detection also allows the precise localization of the leak. Nevertheless, the mechanical stress applied to the flexible packaging due to the vacuum required for tracer gast testing is not an easy task to cope with.