Der Einfluß der Feuchteaufnahme auf die mechanischen Eigenschaften von Phenoplasten

The Effect of Moisture on the Mechanical Properties of Phenolic Moulded Materials In order to use thermosetting moulding material it is necessary to know how the mechanical properties are changed by absorption of water. Therefore, multiphase systems based on phenolic resin, with varying quantities of wood flour and/or powdered minerals as fillers, were examined. The relationship between moisture absorption and the change in Young's modulus, flexural strength and the strain of the outer fibre at fracture was determined. It could be shown that the increase in flexural strength as water absorption began is a result only of the swelling stress.     

Einfluß von Sauerstoffspuren auf die Eigenschaften von Wolfram-Schwermetallen

Influence of Oxygen Traces on the Properties of Tungsten Heavy Metals Investigation carried out with differently sintered W heavy metals showed that careful pre-reduction before liquid phase sintering is essential for obtaining satisfactory mechanical properties; otherwise oxide layers at the phase boundaries deteriorate the interface strength and thus cause premature fracture. Understandably, the water vapour content of the furnace atmosphere is of considerable importance. Appropriate sintering anticipated, even severely oxidized green compacts result in highly ductile heavy metals. Addition of scavengers, e.g. Cr or V, instead of the pre-reduction improves the interface strength, the mechanical properties however remain unsatisfactory.     

Einfluß der Korngröße auf mechanische Eigenschaften und den ungeschmierten reversierenden Gleitverschleiß von Al2O3-Keramik

Influence of grain size on mechanical properties and dry oscillating sliding wear of Al₂O₃-ceramics Specimens with average grain sizes varying between about 0.8 μm and 12 μm were produced by cold isostatic pressing of high purity Al₂O₃-powder followed by sintering between 1300°C and 1700°C. Hardness, Young's modulus, bending strength and fracture toughness were measured as a function of average grain sizes. Tribological tests were carried out on the different microstructures at normal laboratory air and room temperature by using a ring-on-block tribometer. Experimental results showed the dependence of mechanical properties on grain size, hardness and bending strength obeying a Hall-Petch type relation, approximately. Coefficient of friction was relatively independent of grain size under the test conditions used. However, wear intensity increased substantially if a critical grain size was surpassed. This was due to a change in mechanisms of material removal which was confirmed by scanning electron microscopical studies of the worn surfaces.     

Einfluß der Mahlbedingungen und der Qualität der Ausgangsprodukte auf die Eigenschaften von Al-C-Strangpreßprodukten

Influence of the Crinding Parameters and the Quality of the Starting Materials on the Properties of Extruded AIC Products Dispersion strengthened aluminium has been produced by grinding aluminium powder with carbon black in a high energy ball mill, heat treating of the milled powder and subsequented hot extrusion. Tensile strength, elongation, hardness and impact strength were determined. The influence of griding parameters, such as duration, speed of rotation of the rotation arm and the weight ratio of powder to milling balls on the mechanical properties of the extruded rods were investigated. Other important variables are the oxygen content of the aluminium powder, the quality of the carbon black and additions of control agents such as oil or water.     

Der Einfluß der Kohlenstoff-Diffusion auf die mechanisch-technologischen Eigenschaften von ferritisch-austenitischen Schweißverbindungen im Chemie-Betrieb

The effect of carbon diffusion on the mechanical properties of ferritic-austenitic weldments . Weldments between ferritic and austenitic steels indicate a diffusion of carbon from ferritic to austenitic partner as an influence of temperature stresses and due higher solubility of carbon in γ-iron in comparison to α-iron. Investigations on two characteristic weldments (German standard H II/1.4571 and H II/Ni) have been conducted in different annealed conditions to study the effect of carbon diffusion on the various mechanical properties. There is an observable impairement of the mechanical properties of the weldments. Increased hardness in the carburised zone causes cracking and tensile strength as well as notch toughness decrease in the decarburised area.     

Einfluß einer thermomechanischen Behandlung auf die mechanischen Eigenschaften der Ti6Al4V-Legierung

Influence of thermomechanical treatment on the mechanical properties of Ti6Al4V Thermomechanical treatments of Ti6Al4V including deformation just below the β-transus followed by water quenching and aging were shown to substantially improve the mechanical properties. Especially the fatigue strength was raised well beyond levels known from conventional processed material, for both room and elevated temperatures. The paper shows how other properties like tensile strength, ductility, fracture toughness, creep strength fatigue crack growth and stress corrosion cracking are affected.     

Einfluß der Mikrogefügeausbildung auf die technologischen Eigenschaften insbesondere die Schwingfestigkeit der Titanlegierung Ti 6 Al 4 V

Influence of Microstructure on Mechanical Properties, especially Fatigue Properties of Titanium Ti 6 Al 4 V Alloy Mechanical properties, fatigue behaviour and fracture toughness, as well as micro- and macrostructure in longitudinal and transverse direction of rolled 100 mm square bars and 88 mm thick plates of the Ti-6 Al-4 V titanium alloy were investigated after different heat treatments in the α + β-field at 700°C and 955°C, as well as in the β-field at 1010°C preferably with subsequent air cooling. Annealing at 700°C with the highest content of α-phase resulted in the highest strenght while heat treatments increasing the β-content lead to lower strength. Higher strenght values are reached by water quenching than by air cooling. Directionality of mechanical properties just as of notched stress rupture decrease at higher annealing temperatures and decreasing α-contents. Fracture toughness increases at rising β-content. The high cycle fatigue strength values determined in pulsating tension testing varied between 545 and 300 N/mm² depending on heat treatment, specimen position and mill product. Annealing at 700°C and high α-content led to higher values than heat treatment in the upper α + β-field with lower α-content. On the other hand, transformed Widmannstätten type structure with small primary grain size does not reduce the level of fatigue strength in comparison to annealing at 700°C. However β-annealing moves the transition from the decreasing to the horizontal part of the Woehler-Line of HCF strength to lower cycle numbers. Heat treatment and the resulting microstructure indicate, independently of product form und specimen position, the higher α-contents in equi-axed form to yield higher LCF strength than lower α-content in elongated transformation structures. Medium LCF values are obtained by β-annealing for Widmannstätten type structures and small grain size.     

Untersuchung der Einflüsse von Substratrauheit und Spritzpartikelgröße auf die Haftung thermisch gespritzter Schichten

About the influence of substrate roughness and spray particle size on the adhesion of thermal spray coatings The influence of substrate roughness and spray particle size on the adhesion of thermal spray coatings was researched systematically. In addition to established spray materials (Cr₂O₃, WCCo, NiCr) and spraying processes (atmospheric plasma spraying (APS), high velocity flame spraying (HVOF)) different substrate materials (steel, stainless steel, aluminum) were included in the research work as well.     

Beitrag zum Einfluß von Druckwasserstoff auf die mechanischen Eigenschaften von Stählen

Contribution to the Influence of Pressurized Hydrogen on the Mechanical Properties of Steels The investigation method of using hollow specimens in tensile tests to examinate steels for hydrogen service is described. Reduction of area after fracture, Z, resulting from these tensile tests with constant strain rates shows not only a significant but also a constant difference between hydrogen and nitrogen when being plotted versus strain rate. Therefore a newly introduced term named “Index of embrittlement” and characterized by the relation of Z with nitrogen and with hydrogen was found to be independent of strain rate. With strain rate ε = 10^?6 s^?1 chosen for a “critical” one because of lacking in a maximum index of embrittlement several European steels for hydrogen service were tested to find out their individual index of embrittlement. Assisted by light optical microscopy it was found that there is a special correlation between microstructure, index of embrittlement and tensile strength of a given steel grade.     

Einfluß der Belastungsfrequenz auf die Lebensdauer von Punktschweißverbindungen

The Effect of Different Test Frequencies on the Lifetime of Spot-Welded Joints In general lifetime prediction of welded joints is basing on S-N-curves where the influence of the variation of the S-N-curve is not taken into consideration. Moreover, it is not possible to specify the valid frequency range for the endurance limit of spot-welded joints. The test frequency defines the load velocity as a function of the phase relation of the strength. At the same time, the strength properties of the base material, the HAZ and the weld nugget are affected by load velocity. This means that the endurance limit of spot-welded joints is a function of the test frequency. This correlation was confirmed with tests on spot-welded deep-drawing sheets of R St 1403 (similar to AISI C 1008). In the report test results and the different fracture mechanisms are presented.     

Optimierung von Schwingfestigkeitseigenschaften beim Oberflächendrücken gekerbter Umlaufbiegeproben unter Berücksichtigung der Probengröße

Optimisation of Fatigue Properties by Surface-Rolling of Notched Specimens of Different Size The fatigue properties of notched specimens can be largely improved by surface-rolling. It is important to know the material strengthening in the rolling contact to improve the conditions of the surface-rolling process. A computer program is presented, which allows a determination of rolling pressures to any geometries of specimens. As a result of the fatigue investigations it is shown that surface-rolled notched specimens improve the fatigue limit above the fatigue strength of smooth specimens independed on the stress concentration. The improvement of endurance limit of notched specimens with non propagated cracks is based on the effect of constant compressive residual stresses.     

Einflußgrößen auf die Schweiß;kraft elektrischer Kontaktstücke in der Energietechnik

Parameters Influencing the Welding Force of Electric Contacts in Power Engineering . Main parameters influencing the accumulated frequency distribution of the welding force using bouncing contacts are: contact force, closing velocity, duration of bouncing, number of operations, testcurrent, phase displacement, frequency, moment of contact in relation to current zero at inductive load. The statistical distribution over a wide range of the values of the welding force is traced back on the relative position of the weldings on the surfaces of the contacts by means of a model. The influence of duration of bouncing, number of operations, contact force, opening velocity, value of test current and polarity on the welding force is described by accumulated frequency distribution plottings for various contact materials when making contact synchronous- and asynchronously.     

Einflußgrößen bei der Analyse von Schallemissionen

Factors Influencing Acoustic Emission Analysis . The interpretation of AE measurements requires careful consideration of the prevailing conditions, to ensure reproducable results. By the use of simulated signals in a small steel plate, an analysis of the effect of these various conditions, on the frequency and amplitude distribution of these signals, is possible. In this way the accuracy of location of emission sources can be improved.     

Einfluß der Oberflächenbeschaffenheit auf die Schwingfestigkeit von Aluminium-Druckguß

Effect of Surface Condition on Fatigue Strength of Die-Cast Aluminium Surface processing like milling or shot peening involves modifications of the surface and subsurface condition of a material that can be described by changes of the residual stresses, the hardness, and the surface roughness. Moreover, there is the possibility of introducing additional surface defects. In this paper the influence of these modifications on the fatigue behaviour of the aluminium die-casting alloy GD-AlSi8Cu3 is presented. S-N curves are determined for four surface conditions produced by milling, shot peening, and a combined treatment. The improvement of fatigue limit by shot peening is confirmed for this material. The additional effect of mean stresses is determined. Investigations of the fatigue fracture surfaces show that pores and pipes as well as surface defects induced by shot peening act as fatigue crack initiation sites.     

Größeneinfluß auf die Schwingfestigkeitseigenschaften von Schweißverbindungen

The size effect on the fatigue properties of weldments Constant amplitude fatigue tests (R = ? 1 and 0)have been carried out in order to investigate the influence of specimen size and manufacturing conditions on the high-cycle fatigue behaviour of large welded I-beams (web height 500 mm, total length 12 and 7 m respectively). The specimens contained transverse butt welds and longitudinal fillet welds, mainly produced by manual metal arc welding. The Δs?-concept, as proposed in international standards for fatigue related design is supported by the test results as far as transverse butt welds or longitudinal fillet welds in large sections are concerned. The HCF-behaviour of butt joints in large sections, welded under site conditions, are reasonably covered by Eurocode 3 category 90. EC 3-Category 100 does not conservatively cover the HCF-behaviour of longitudinal fillet joints in large sections.     

Einfluß der Korngröße auf Reibung und Gleitverschleiß von TZP?ZrO2-Keramik bei Festkörper- und Mischreibung

Effect of grain size on friction and wear of TZP? ZrO₂ ceramic in unlubricated and boundary lubricated sliding contact . Microstructures with systematically between 0.30 and 1.62 μm varying average grain sizes were produced by cold isostatically pressing and sintering of commercial 3 mol.% Y₂O₃ stabilized ZrO₂ powder. Hardness and fracture toughness of the different structures as well as the amount of tetragonal, cubic and monoclinic phases were measured. Wear tests were carried out on the different self-mated microstructures in unlubricated and oil or water lubricated unidirectional and unlubricated reciprocating sliding contact, respectively. Worn surfaces were systematically analysed using scanning electron microscopy. The experimental results showed a significant influence of the average grain size as well on mechanical properties such as hardness and fracture toughness as on tribological properties. Friction and wear are discussed in relation to grain size and phase stability of the microstructures and also as a function of the different tribosystems and lubricants used.     

Der Einfluß der Porosität auf einige Eigenschaften von Wolfram/Kupfer-Kontaktwerkstoffen

The Influence of Porosity on a Few Properties of Tungsten/Copper Contact Materials . An investigation has been carried out on the influence of the amount of residual porosity on the electrical and mechanical properties of infiltrated tungsten/copper materials. By means of adding different quantities of infiltrating metal materials with a tungsten content of approximately 70 wt.% containing between 0,2 and 30% pores were produced. The following properties were measured for the different material specimens: are erosion rate, electrical conductivity, Vickers hardness number, and notch impact toughness. The arc erosion rate is not noticeably increased by pore contents up to 4%, all the other properties, however, are influenced considerably even by the smallest amount of measurable residual porosity. Thus it has to be concluded that infiltration with a slightly smaller quantity of infiltrating metal than that necessary to attain a pore-free material – a technique used occasionally in order to avoid the necessity of finishing the infiltrated parts – will lead to changes in quality.     

Einfluß der Hartstoffkomponenten auf einige Eigenschaften von Hartmetallen unter besonderer Berücksichtigung neuerer Werkstoffentwicklungen

Influence of the Hard-material-components on some Properties of Hardmetals Respecting Especially Modern Developments of Working Materials . In the following paper some properties of hardconcerning the application are discussed. First of all the function of tungsten-carbide, of titanium-carbide and of tantalum-carbide in the conventional hardmetals are described, also pointing out the possibilities of linear-analytical structure-examination in connection with tool-life-tests Also the field of special working-materials with carbide phase used nowaday in the market besides conventional carbide-base hardmetals is reported briefly.     

Einfluß von unverformbaren Teilchen auf die Strangpresstexturen von Verbundwerkstoffen

Influence of undeformable particles on the extrusion texture of composite materials The influence of α-Al₂O₃ particles on the extrusion texture of Ni-, Cu or CuZn30-composites has been investigated, variing particle size and interparticles spacing. The rods show a 〈100〉-recrystallization texture, which decreases with greater values of the interparticle spacing. In the case of the addition-free Cu and CuZn30 a random orientation distribution of the crystals was found. These results are discussed in comparison with the results found on Al? Al₂O₃-composites.