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.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 1: Beschichtung von unbehandelten Kunststoffolien

Plasma Pretreatment and Coating of Polymer Films. Part 1: Coating of Non-treated 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 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. The next part contains the results of the systematic modification of polymer surfaces 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.     

Schallemissionsuntersuchungen an polymeren Verbundwerkstoffen. Teil II: Experimentelle Ergebnisse

Acoustic Emission Monitoring of Polymeric Composite Materials. Part II: Experimental results The technique of acoustic emission monitoring of polymeric composite materials is described. It is a high sensitive, quasi-nondestructive testing method that indicates the origin and the behaviour of flaws in such materials, when submitted to different load histories. In the usage of sophisticated signal-analysis-methods it is possible to distinguish between different types of failure mechanisms, such as fiber fracture, delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.     

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.     

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.     

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.     

Beschichtung von Kunststoffen im Bereich Ophthalmik und Laserschutz

For achieving the desired manyfold requirements many types of technologies are used in the field of coating ophthalmic plastic lenses. In addition to the chemical coating PVD-processes are widely used for AR and scratchresistance. In the meantime plasmapolymerisation is used, too. The desired performances in the field of laser-safety-goggles can be realized only with coatings. This paper describes the aims of coatings, the theory about the interference-optic and the used coating-technologies together with the needed testingroutines.     

Effekte der Indentergeometrie und innerer Materialpannungen auf die Ergebnisse von Kraft-Eindringtiefe-Messungen

Effects of indenter geometry and internal Stresses to the results of load-indentation measurements. Loadcindentation measurements were performed on hardened high speed steel, glass and TiN/steel coating-substrate composites with Vickers and Berkovich indenters. The coatings were deposited with selected parameter sets to produce different internal coating stresses. The evaluation of the load-indentation measurements was performed by energy related considerations of the deformation processes. Two material- and indenter-related specific energies are calculated which describe the extension of the energetic densification zone caused by the penetration of the indenter. The specific energy density of volume change could be related to the two types of indenters. The specific energy of area change has been related to internal stresses in the probed material.     

Vergleich der Ergebnisse von Betriebsfestigkeitsversuchen mit Hilfe der Relativ-Miner-Regel

Comparison of Service Spectrum Test Results with Aid of the Relative-Miner-Rule Some examples of using the Relative-Miner-Rule for comparison of different test results are given in the paper. The tests were performed with not identical aircraft loading spectra on different joints in different laboratories. A conversion of test results with aid of the Relative-Miner-Rule in comparable fatigue life parameters (e. g. Number of flights) for a common loading frequency distribution is possible, if S-N lines of the joints are experimentally established. A comparison of the fatigue life of riveted joints, pin-lug joints and notched specimens in the cases of TWIST and FALSTAFF was discussed. The comparison showed that the relative location of the corresponding endurance lines depends on the type of loading frequency distribution and on the magnitude of the largest loading cycles. The application areas of the Relative-Miner-Rule were analysed in detail from the viewpoint of the effect of loading spectrum modifications, material variations, type of component, specimen size and of calculation input data.     

Mit Hochfrequenz angeregte Niederdruckplasmen: Prinzipien und Strukturierung von Halbleitern. Teil I

In two parts, the generation of cold plasmas by capacitive and inductive coupling as well as by absorption of whistler waves is outlined. In the third part, it is shown how the knowledge of these mechanisms can be exploited for modifying the surfaces of semiconductors.     

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.     

Spanende Bearbeitung von Hartlegierungen – Drehen und Schleifen. Teil I: Gefüge und Eigenschaften von Hartlegierungen

Metal Cutting of Hard Alloys – Turning and Grinding. Part I: Structure and Properties of Hard Alloys Hard alloys count among the materials that contain hard phases. This involves primary and/or eutectic hard phases embedded in a metallic matrix. The characteristics of the individual microstructural constituents may be combined to form a material featuring excellent wear resistance and a high resistance to fracture. For that reason, the material can be widely used in all applications where the wear resistance to abrasion is essential. In the event low operating temperatures are involved the component costs to service life ratio speaks for hard alloys on Fe basis. Above 600 °C heat resistant Ni and Co matrices are to be given preference. Carbides and borides of the transition metals are specially suited as hard phases. They attach well to the surrounding matrix. Nowadays, alloys of the FeCrC system are primarily employed for economic reasons. As nickel-based material the NiCrSiB alloying system is frequently employed. Hard alloys on cobalt basis usually belong to the CoCrWC (stellite) system. In many fields of application components of this material group require a largearea metal cutting technique (eg for barrel extruders, crushing rollers, valve seats). However, problems may be encountered during machining due to the high hardness and excellent wear resistance of this material. The structural difference between hard phases and metallic matrix causes different reactions to stresses exerted during the machining process. Process-related changes of the microgeometric surface characteristics and the physical condition of the surface zone of a material are paraphrased by the term “surface integrity”. To create a basis for assessing the machining influence on the multiphase component surface layer, the first part of the paper discusses manufacturing techniques, constitution of the microstructure and main properties of the individual structural components.