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.     

Versagenskriterien für Kunststoffe. Teil II: Experimentelle Ergebnisse

Failure Criteria for Polymers, Part II: Experimental Results . Using the fracture criteria, which have been analytically derived in the first part of this paper, experimental results from literature and from own experiments are compared with calculated fracture loci for thermoplastic materials, thermosets, and glassfibre-reinforced plastics. It can be shown that the change of dimension of a plastic specimen under load is simulating a higher compressive strength in comparison to the tensile strength (m > 1). Different methods are indicated for evaluating biaxial loading tests. A comparison between the results theoretically and experimentally found marks the parabolic fracture criterion to be suitable. Resins reinforced with chopped strand mats satisfy the maximum stress theory. The fracture behavior of orthotropic materials is accurately described by the fracture criterion of Tsai and Wu and Goldenblat and Kopnov. If normal stresses act parallel to the axis of orthotropy, the fracture behavior of orthogonal isotropic materials can be calculated acc. to the maximum stress theory.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 2: Experimentelle Ergebnisse der Plasmavorbehandlung von Kunststoffolien

Plasma Pretreatement and Coating of Polymer Films. Part 2: Experimental Results of the Plasma Pretreatment of Polymer Films The food packaging industry demands cheap polymer films possessing a high barrier against permeation of gases, moisture and flavor. Candidates for the most successful materials fulfilling these requirements are vacuum web coated b iaxial o riented p olypropylene (BOPP) films containing a thin inorganic barrier layer. For a good adhesion of the barrier layer on the BOPP films, the polymer film must be pretreated. The industry uses the Corona atmosphere plasma. This work is separated in three parts. The first part describes the experimental setup and the properties of vacuum web coated layers on polymer films [1]. The next part contains the results of the systematic modification of po } ymer surface by atmosphere and low pressure plasmas. The influence of the surface properties on the final functionality of the coated films is given. In the last part, the discussion of the results of the first and second part reveals systematic relations between the production parameters of the high barrier films and their final functionality. These results firstly reveal the adhesion mechanism of the inorganic barrier layers of the polymer films and the necessary surface properties of the polymer films, in order to get cheap high barrier films by vacuum web coating.     

Werkstoffverhalten unter mehrachsiger schwingender Beanspruchung. Teil 2: Experimentelle Untersuchungen

Behaviour of Materials under Multiaxial Cyclic Loading . A great many structures and structural components are subject to multiaxial cyclic loading, e. g. the shafts. In the first part of the investigations several possible methods of calculation were discussed, by which the strength behaviour of metallic materials under multiaxial cyclic stress conditions can be described. They are, in the second part, critically compared with the results of a series of experimental investigations.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 3: Auswertung der experimentellen Ergebnisse und Diskussion

Plasma Pretreatment and Coating of Polymer Films. Part 3: Analysis of the Experimental Results and Discussion The food packaging industry demands cheap polymer films possessing a high barrier against permeation of gases, moisture and flavour. Candidates for the most successful materials fulfilling these requirements are vacuum web coated biaxial oriented polypropylene (BOPP) films containing a thin inorganic barrier layer. For a good adhesion of the barrier layer on the BOPP films, the polymer film must be pretreated. The industry uses the Corona atmosphere plasma. This work is separated in three parts. The first part describes the experimental setup and the properties of vacuum web coated layers on polymer films[1] The next part contains the results of the systematic modification of polymer surface by atmosphere and low pressure plasmas[2]. The influence of the surface properties on the final functionality of the coated films is given. In the last part, the discussion of the results of the first and second part reveals systematic relations between the production parameters of the high barrier films and their final functionality. These results firstly reveal the adhesion mechanism of the inorganic barrier layers of the polymer films and the necessary surface properties of the polymer films, in order to get cheap high barrier films by vacuum web coating.     

Bewertung von Schädigungserscheinungen in Thermoplasten mittels simultaner Messung der Spannungs-Dehnungs-Charakteristik und dielektrischer Kennfunktionen. Teil II: Interpretation der experimentellen Untersuchungen und deren Ergebnisse

Evaluation of damage effects in thermoplastics by means of simultaneous measurements of stress-strain characteristics and dielectric properties. Part II: Interpretation of the experimental investigations and the results In the first part the damage failure effects in amorphous thermoplastics due to mechanical loading was discussed. The present part describes the technique of measurements, the experimental results and the generally interpretation. A scientific interpretation on micromechanical basis will be given in Part III.     

R-Kurven von energiedissipativen Werkstoffen mit Schädigungszone Teil 2: Experimentelle Ermittlung von J-R Kurven

R-curves of energy dissipative materials Part 2: Experimental evaluation of J-R curves A hypothesis regarding the conversion of mechanical into thermal energies within the nonlocal damage region is formulated to model the fracture behaviour of energy dissipative materials with rising crack resistance characteristics. The material's capacity to develop nonlocal damage beyond blunting is assumed to decrease with the actual damage level. This decrease relates linearly with the remaining resources of the material in dissipating energy. The hypothesis, wich proposes a square root function for theoretical J-R curves, is verified by the regression analysis of experimental data regarding a European round robin test of different steels.     

Einkristalline Gasturbinenschaufeln aus Nickelbasis-Legierungen. Teil II: Wärmebehandlung und Eigenschaften

Single-Crystal Blades for Gas Turbines Part II: Heat Treatment and Properties The article gives an overview of current single-crystal technology used in fabricating highly stressed blades and vanes for gas turbines. After a short outline of the demands placed on gas turbine blades and the resulting necessity for improvement of nickel-base alloys, and following a short definition of the “technical” single-crystal, the principal of directional solidification with suitable methods of grain selection and the realizable solidification front morphologies were described in Part I. The usuable range of casting parameters for industrial production was fixed using the alloy SRR99 as an example. The major mictrostructural characteristics of single-crystal comoponents made of nickel-base alloys namely crystallographic orientation, microporosity, morphology of the γ′-hardening phase, dendritic segregation and residual eutectic were presented. After casting, the microstructure is not in a condition which yields optimum service properties. Therefore, heat treatment is necessary. Part II describes how, with appropriate heat treatment, residual eutectic can be dissolved, segregations homogenized and the morphologly of the γ′-phase optimized. Finally, the mechanical properties are discussed. The dominant influence of the crystallographic anisotropy on elastic and plastic properties are shown as well as the dependence of the creep behaviour on the morphology of the γ′-phase and the correlation between fatigue strength and microporosity.     

Fließbedingung für Thermoplaste. Teil II: Isotrope Fließbedingung

Yield criterion for thermoplastics. Part II: Isotropic Yield Criterion Using the plastic potential for anisotropic solids which have been investigated in the first part of this paper, a isotropic yield criterion is derived and compared with experimental results.     

Spanende Bearbeitung von Hartlegierungen – Drehen und Schleifen. Teil II: Drehen von Hartlegierungen

Metal Cutting of Hard Alloys – Turning and Grinding. Part II: Turning of Hard Alloys Turning tests were carried out on selected hard alloys on iron (FeCr12C2.1, FeCr13Nb9MoTiC2.3, FeCr14Mo5WVC4.2) and cobalt basis (CoCr29W5C1.3) in a cutting speed range of between v_c = m/min and 180 m/min. Polycrystalline cubic boron nitride (PCBN) turned out to be a suitable tool material. Subsequent examinations focused on evaluating the mechanisms of chip formation, cutting tool wear and surface integrity of the workpiece. During turning of hard alloys the formation of chips is primarily influenced by the ductility and fracture toughness of the work material. While a ductile matrix enables the formation of highly deformable chips, the chips stemming from martensitically hardened alloys show low deformation. As the cutting depth increases shear and segmented chips are chiefly produced. Type and arrangement of the hard phases play a significant role. Adhesion is the main wear mechanism impacting the cutting face of the tool. Particularly, strong adhesion effects will arise during the machining of the work hardening alloy on cobalt basis. A high cobalt content of the metallic bonding phase of the PCBN cutting tool appears to be a disadvantage with this type of work material. When machining alloys on iron basis adhesion is promoted by the mechanical linking of alloy-specific hard phases to the cutting material binder. Abrasion primarily acts on the flank. The hard carbides of the work material produce typical grooves in the cutting edge zone of the tool. The flank wear increases as the carbide content goes up. As the cutting speed rises the tool wear ascertained passes through a minimum. Whereas the formation of built-up cutting edges predominates at lower speeds, a thermal softening of the PCBN binder takes place and is dominating at high cutting speeds. The location of the wear minimum depends not only on the cutting temperature but also on the strain hardening capability of the metal matrix. Raising the cutting speed will cause the cutting force to continuously reduce. The highest cutting forces are found for the Co-based alloy. The passive forces develop in line with cutting tool wear and vary with content and hardness of the hard phases involved. The selected process parameters also affect the surface near zone. With low cutting speeds and process temperatures the surface is mainly stressed mechanically. Carbides break or detach from the surrounding matrix. If the cutting speed and process temperature are increased the eutectic carbides (M₇C₃) are deformed together with the metal matrix. Microhardness profiles are indicative of near-surface strain-hardened zones after cutting of the Co-based alloy. Fe-based matrices do not show hardness changes worth mentioning. Although there are no new hardened zones noticeable even at maximum cutting speed, the matrix is nevertheless influenced thermally so that residual stresses will develop in the machined surface layer. In the lower cutting speed range the surface quality is characterized by flakes and material squeezing (Co-based alloy) and by spalling (Fe-based alloy). Only if the cutting speed is raised, a minor roughness is detected due to a potential deformation of eutectic hard phases.     

Untersuchungen über das Strangpressen kubisch-flächenzentrierter Metalle. Teil II: Kraftbedarf und Kraftverteilung

Investigation of the extrudability of face-centred cubic metals Part II: During continuous extrusion at certain intervals dry oxides are discharged. This is explained with the aid of rheological investigations. If a shearing device according to DIN standard is used the results may show errors in a range of 70% and more. A new device is described which avoids this source of error. The shear strength of high purity aluminium was determined at various temperatures and rates of deformation. Investigations were conducted under similar conditions on the extrusion of aluminium and a relationship between shear strength and power requirement was established. On this basis the power requirement to extrude new alloys may be predicted by comparing the shear strength of this alloy with the shear strength of an alloy whose extrudability is known. Direct extrusion experiments under isothermal conditions were conducted in the reduction range R = 1.2–300. The linear relationship in double logarithmic scale exists only in the range of R = 4–40. Indirect extrusion experiments also showed a linear relationship below the reduction rate R = 4 in a logarithmic scale. It was found that during indirect extrusion a dead metal zone is also formed and this explains the divergence of the found pressure distribution from the theoretical values. The normal pressure of the container was measured at a number of points at various temperatures and reduction rates. In the range of 150°–170°C peculiar unsteadiness occured. Normal pressure on the change of the velocity of extrusion was investigated with the aid of a stepped-down die and a strong dependence was found. A device was developed to compare the plasticity of cubic face centered metals, and it was found that the maximum plasticity is reached at 90% of the melting point in degrees absolute. Efficiency investigations during extrusion showed that the power consumption required to overcome the radial shear in continuous extrusion is 60% to 77%, whereas the power required to overcome the total shear in extrusion in a piston driven press is 94% to 87%. Extrusions inside a calorimeter showed, on the basis of mechanothermodynamic conversion, that 85% to 94% of the power was used for the deformation of the metal.     

Beschreibung des Kriechverhaltens von Gasturbinenwerkstoffen. Teil II: Kriechgleichung für die Werkstoffsorte IN-738 LC

Creep Behaviour of Gas Turbine Materials part II. Creep Equation for Alloy IN-738 LC On alloy IN-738 LC, an extensive creep data collection is evaluated to obtain mean creep curves. On these curves a creep equation optimized for an individual test material is fitted to express the mean creep behaviour of alloy IN-738 LC.     

Einfluss des sauerstoffpartialdruckes bei der Cd-, Se- und CdSe-Schichtbildung II. Experimentelle bestätigung an Cd-, Se- und CdSe-Schichten

Cd, Se and CdSe deposition has been carried out at various partial oxygen pressures and the results have been compared with theoretical predictions. The influence of O₂ during the formation of layers of various oxidation properties has been analysed.     

Wirkung von Oberflächenschutzmaßnahmen auf hochwarmfeste Gasturbinenwerkstoffe. Teil II: Beeinflussung des Gefüges

Influence of Coating on the Properties of Heat Resistant Gas Turbine Alloys. Part 2. Microstructures Differences in the creep behaviour of some Ni base alloys were interpreted by a metallographic examination of broken specimens of a creep rupture test. If the fructure of uncoated specimens is intiated by an oxidation from the surface, by coating the time until rupture is elongated. If the fracture of uncoated specimens is unsensitive to an oxidation fro the surface, there is no influence of a coating except on melt of the alloy IN-792 coated with RT 22. Improvements or deteriorations in creep resistance of coated specimens compared with uncoated mainly are caused by the heat treatments during or after coating. Different casting techniques influence the orientation of dendrites and size, position and arrangement of pores wich partly have a decisive influence on the creep behaviour. Differences in creep limits up to a factor of 2 in time in general could not be interpreted by the metallographic observations used.     

Untersuchungen Zum Temperaturwechselverhalten von Gußeisen - Teil II: Werkstoffwissenschaftliche und metallphysikalische Interpretation

Test examing the temperature shift behaviour of cast iron - Part II: Interpretation according to materials science and metallphysics The first part of this article discusses the most important influences on temperature shock behaviour of cast iron materials and experimental results of the examinations. The presented second article offers an interpretation of theoretical as well as practical examination results according to materials scientific views. A method will be presented determining the lifetime of thermal shock stressed components using activation-energy-stress diagrams and statisticall significant regression-relationships.