Untersuchungen zur Anwendung der Bruchmechanik auf duktile Werkstoffe am Beispiel des Bruchverhaltens von weichmacherfreiem Polyvinylchlorid

Study on the Application of the Fracture Mechanics Concept to Ductile Materials–Fracture Behavior of Rigid PVC The fracture behavior of ductile materials cannot be treated by the methods of linear elastic fracture mechanics concept. For these materials the application of extended theories, which consider the non-linear stress-strain-relationship, is necessary. The test results being reported here have been obtained from rigid blue colored PVC. CT-specimens of different sizes were tested in tension at different loading rates. Above a certain strain level, the material shows crazing. This makes it possible to determine the plastic zone size. The relatively low Young's modulus originates in great deformations of the specimen. The deformation can therefore be measured with great accuracy. During the tests, a great number of quantities were registered. From these quantities the stress intensity factor, crack opening displacement, I-Integral and so on were calculated. The applicability of the results, in order to describe the fracture behavior of ductile materials, is being discussed.     

Anwendung wissenschaftlicher Methoden zur Erklärung der Pustelbildung bei der Duplexbeschichtung

The occurrence of defects like pustules in varnish finishings results in economic problems in the industrial practice of powder coating of galvanized steel parts. The mechanism for the formation of pustules was investigated in a set of scientific integrating methods and a general theory was developed. Metallographic microscopy with its analytic tools as well as wet chemistry research were applied, further glow discharge spectroscopy (GDOS) and mass spectrometry. With mass spectrometry the outgassings from a hot dip zinc probe were identified: it is mainly water with 82% by volume, followed by carbon dioxide (10%) and hydrogen (8%), which together are responsible for the formation of the pustules.     

Theoretische Grundlagen für die Anwendung der Bruchmechanik auf Faserverbundwerkstoffe

Theoretical Foundations for the Application of Fracture Mechanics to Fibre Reinforced Composites This work gives a survey of the theoretical problems arising from the application of fracture mechanical concepts to fibre-reinforced composite materials. A classification of existing models into macro- and micromechanical is proposed, the derivation of essential equations outlined and some graphical illustrations of the resulting formulae are shown.     

Die Bruchmechanik und ihre Anwendung auf Fragen der Bauteilzähigkeit

Linear Elastic Fracture Mechanics and its Application to Structural Components . The first part deals with some theoretical aspects of linear elastic fracture mechanics and their application to thick-walled structural components. One of the prerequisites are plane strain conditions in both the fracture mechanics specimens and in the structural components. The types of specimens, the experimental procedure for the investigation of stress intensity factors K_Ic and some difficulties in practice are discussed together with examples illustrating the application of fracture mechanics technology to heavy section pressure vessel components.     

Grundlagen der Bruchmechanik

Ohne Zusammenfassung     

Grundlagen der Bruchmechanik

Basis principles of fracture mechanics. Based upon the linearelastic equations for the stress field in a tension stressed body containing a crack and upon the energy condition for the unstable crack propagation the quantities stress intensity factor and crack extension force are derived. Taking into account the plastic zone combined with the crack propagation in real bodies the linear-elastic relations hold furthermore with a sufficient accuracy if the length of the plastic zone is small compared with the crack length (small scale yielding). Then the fracture toughness is a materials constant. The nonlinear extension of these equations for the partly plastic range exhibit that the critical crack opening stretch is likewise a materials constant up to a length of the plastic zone comparable with the crack length. In all these cases the fracture stress decreases with increasing crack length and has a value below about 0.7 times the yield stress under uniaxial tension (low stress fracture). Approaching to the fully plastic yielding these statements become invalid, the fracture stress is greater than the uniaxial yield stress and is independent of the crack length. To obtain a perceptible picture of these statements the numerical values of the quantities are presented for a pressure vessel steel and for a heat-treatable steel. —The principles of the fracture mechanics and of the COS-concept are described. In this connection the plastic instability of pressure gas pipelines are mentioned and furthermore it is discussed if it is necessary – at all – to examine the structural steels with the methods of the fracture mechanics.     

Quantitative Bewertung von Werkstoffinhomogenitäten auf der Basis der Bruchmechanik

Today it is impossible to quantitatively judge defects of welded joints, because a definite connection between defect and failurestress does not exist. Based on fracture mechanics a theoretical connection is produced between the portion of defects in a welded joint and the failurestress of such a welded component (plate or pipe). It Proved right that the failure-stress is dependent upon both the ratio K_c/σ* (K_c = fracture toughness; σ* = flow stress) and the component-size, whereas the allowable portion of defects rise with increasing K_c/σ* However, the allowable portion of defects decrease with increasing component-size.     

Anwendung der Beugungstheorie auf Rechnerisch Korrigierte Mikroskopobjektive zur Beurteilung der Restfehler

Die rechnerische Korrektion optischer Systeme nach den üblichen geometrisch-optischen Strahlendurchrechnungen erfährt eine für Mikroskop-Objektive sinnvolle Ergänzung durch ein beugungstheoretisches Berechnungsverfahren für die Helligkeitsverteilung im Bilde eines punktförmigen Selbstleuchters unter Berücksichtigung monochromatischer Bildfehler beliebiger Mischung, aber beschränkter Größe. Diese Helligkeitsverteilung wird als Grundlage zur Beurteilung der Abbildungsqualität angesehen. Das vorgestellte Verfahren wird an Mikroskop-Objektiven der Firma Ernst Leitz GmbH. Wetzlar demonstriert. Der Rechnungsgang eignet sich zur Programmierung für einen Rechenautomaten; es wird empfohlen, die Helligkeitsverteilung direkt vom Fernschreiber als Typenraster ausdrucken zu lassen.     

Fortschritte in der technischen Anwendung von Kunststoffverbundsystemen

Progresses in the application of plastic compound materials Plastics possess a number of various properties one cannot find in another material in this combination. Beyond that the desired properties can be reached by compounding several different materials. The best known example is the glass reinforced plastic. The arguments for the application of compound materials are very different: increase of strength and stiffness, cheaper injection moulded parts due to shorter cycle times, thinner wall-thicknesses and therefore less raw material consumption, lower distortion and thermal elongation for technical parts and excellent thermal insulation of the foams. Research on the topic of the bonding between the plastic and the carbon, glass and organic fibres led the way to an ever spreading field of the application of reinforced plastics.     

Methoden zur mechanischen Charakterisierung von modifizierten Implantatoberflächen in der Orthopädischen Chirurgie

Methods for the mechanical characterisation of modified implant surfaces in orthopaedic surgery Nowadays, on average approximately 10 % of all hip and knee endoprostheses have to be exchanged within the first 10 years. Implant revision is often necessary following aseptic or septic loosening. Hence, today implants for orthopaedic surgery are increasingly being coated for better osseointegration. Coatings have to be biocompatible and meet high mechanical requirements, whereby the adhesive strength and the abrasive wear resistance of the coatings take on a key role. This study presents different methods to asses these parameters experimentally using two innovative coatings (TiN, TiO2‐Cu) exemplary. The adhesive bonding strength of the coatings was investigated using different standardised methods, such as the arbour bending test, scratch test and the standard adhesive test. Wear resistance was determined after 1.5 million cycles in a special testing machine. The investigations showed for both coatings, TiN and TiO2‐Cu, good adhesive strength and wear resistance. The adhesive strength and wear resistance of bio‐active, wear reducing or anti‐allergenic surface coatings can be determined reliably using the above‐mentioned methods.     

Anwendung der Speckle-Photographie zur Sichtbarmachung und Messung von Strömungen mit veränderlicher Dichte

Ohne Zusammenfassung     

Methoden zur betriebsfesten Bauteilvorbemessung von innendruckbeaufschlagten Bauteilen aus hochfesten Eisengusswerkstoffen

In the present paper methods based on the related stress gradient χ* and the highly stressed material volume HBV_90% for the assessment of the structural durability of high‐strength ductile iron components are presented. Approximate solutions were formulated on the basis of extensive fatigue tests under constant amplitude loading using specimens from the alloys EN‐GJS‐500‐7, SiboDur 700‐10 and MADI. The estimated fatigue strengths were validated by tests with the so‐called “Pulsing Dummy Model Bodies”, samples with a bore intersection with an angle of 45° as critical area.     

Ultraschallverfahren zur Bestimmung der Anzahl von Einschlüssen in Materialproben — eine kritische Betrachtung empfohlener Methoden

Ultrasonic test procedure to determine the number of inclusions in material samples — a critical analysis of recommended methods. To judge the specific properties of metals one tries to determine the quantity and distribution of the non-metallic inclusions. But the microscopic procedures used so far are destructive and do further not refer to the volume, but rather to the surface of the micrograph sample. Contrary to these methods the inspection by ultrasound is non-destructive and wellsuited for the volumetric detection of inclusions. The possibilities of the ultrasonic pulse-echo-method for cleanliness rating are being checked. Based on the respective results there is a critical view on the ultrasonic test methods which have been recommended so far. Proposals will be made how to make the optimum use of the advantages of the ultrasonic inspection when determining the purity degree of a sample.     

Zur Anwendung der Methoden der elektrischen Netzwerksynthese für den optimalen Entwurf schwingungsfähiger Konstruktionen

Zusammenfassung Im Zuge der Leichtbauweise werden die technischen Konstruktionen immer schwingungsanf?lliger. Oft wird heute versucht, durch eine aktive Beeinflussung die Maschinen oder Bauteile ruhig zu halten. Diese Ma?nahmen kosten Hilfsenergie und sind von der technischen Realisierung her aufwendig. Hier wird eine systematische Methode für den optimalen Entwurf schwingungsf?higer Konstruktionen aufgezeigt, die sich an die Verfahren der elektrischen Netzwerksynthese anlehnt. Den Ausgangspunkt bildet eine sogenannte Zweipolfunktion, die ein passives Netzwerk aus Federn, Massen, D?mpfern und Hebeln beschreibt. Die Parameter der Zweipolfunktion werden so bestimmt, da? sich ein optimales dynamisches Verhalten ergibt. Mit den Methoden der Netzwerksynthese kann dann die Zweipolfunktion als mechanisches System realisiert werden. Durch die beschriebene Vorgehensweise kann die Auslegung passiver dynamischer Systeme erheblich verbessert werden.     

Beitrag zur Mechanik der Kaltumformung von Metallen

Ohne Zusammenfassung Schlu? der Aufsatzes aus Heft 6 (1971) S. 198/204.     

Einführung in die Grundlagen der Bruchmechanik

Introduction to Fracture Mechanics It is the purpose of this paper to familiarize the reader experienced in metallurgy with the basic principles of fracture mechanics. Starting with crystallographical fundamentals the main fracture mechanics parameters – K, G, COD, J – are derived and their physical meaning is interpreted, the range of application and the experimental techniques are also briefly described.