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.     

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.     

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 Probengröße auf die bruchmechanischen Eigenschaften von Sinterstahl

Influence of Specimen Size on the Fracture Mechanical Behaviour of Sintered Steel Fracture mechanics testing was carried out with small and big specimens using high-temperature sintered Fe-2%Cu-2.5%Ni-alloys in the densities of ρ = 7.1 and 7.4 g/cm³. These steels are often used in the manufacturing of PM-parts. Due to the different dismensions the crack propagation is for the bigger sizes faster than for the smaller sizes. Also the conditional fracture toughness of the big specimens is superiour to the toughness of the small specimens. But under consideration of a plain strain state for the big specimens and of a plain stress state for the small specimens valid fracture toughness values being independent from the specimen size can be calculated applying linear-elastic fracture mechanics. These results were obtained for both densities investigated. The increase of the density delivers principally better fracture mechanical data. Hereby the relation of strength data with the microstructure is also discussed.     

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.     

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 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.     

Der Einfluß der Haupt- und Seitenkerbung auf die Temperaturabhängigkeit der Kerbschlagarbeit

The effect of main notch and of side grooves on the temperature dependence of the absorbed energy in impact tests Charpy impact tests were performed on test pieces having different radii of curvature of base of main notch. Six series were sidegrooved and six series were without side grooves. The fracture mechanisms and the appearance of the fracture surfaces are discussed. It is shown that the common practice to assign lower shelf, transition range, and upper shelf in the absorbed energy-temperature curve to cleavage fracture, mixed fracture, and fibrous fracture is not always valid. Cleavage fracture may occur in the entire transition range and mixed fracture may take place in the upper shelf.     

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 Porosität auf die Schwingfestigkeit von Proben und Bauteilen aus Aluminiumdruckguss

Influence of Porosity on Fatigue Strength of Aluminium Die‐Cast Specimens and Components Aluminium die‐casting is widely used in the automotive industry. Brackets, engine blocks, wheels and suspension arms etc. are typical applications. Due to the gases contained in the melt, more or less spherical pores arise in the cast components during the cooling procedure, usually with a higher concentration in the middle. The distribution of the pores depends both on the casting condition and on the form of the components and is stochastic. In the past, the simple way is often chosen for the fatigue life estimation of aluminium die‐casting: The fatigue strengths of the material, e.g. in the form of S‐N curves, are determined by an unnotched specimen which are then used in the fatigue calculation. However, the application of these data to real components with notches leads in many cases to fatigue life estimations which are by far too conservative. In the present paper a simple geometrical model of pores is presented. Using this model, the notch stress caused by a pore can be estimated. The behaviour of pores in a real component with notches will be treated. It will be shown that the mentioned conservative nature of the fatigue life prediction and the apparent notch insensitivity of aluminium die‐casting can be explained by the facts that the stress distribution in a real component, contrary to an unnotched specimen, is inhomogeneous and that the porosity density on the surface is often low.     

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.     

Einfluß von Gasadsorbaten auf die Eigenschaften eines Glühkatoden- Ionisationsmanometers mit axialer Emission nach CHEN und SUEN

The influence of adsorbed gases on the pressure reading of the axial emission ionization gauge according to CHEN and SUEN [1] was investigated in the UHV pressure range. The anodes of the investigated gauges were made from molybdenum and platinum. After exposure to argon, nitrogen, oxygen and hydrogen the ion current versus time characteristic was determined during pumpdown. The pressure reading of the axial emission gauge was compared with the readings of a commercial Bayard-Alpert gauge and an extractor gauge. After exposure to oxygen the gauge with the Mo-anode showed the largest deviation of the pressure readings of the gauges, while the gauge with Pt-anode showed strong deviations after oxygen and hydrogen exposure.     

Über den Einfluß von Probendicke und -geometrie auf die Ermüdungsrißausbreitung und die Bruchzähigkeit von Polycarbonat

The Influence of Specimen-thickness and Geometry on Fatigue Crack Propagation and Facture Toughness of Polcarbonate This study deals with the influence of specimen-thickness and geometry of the fracture-behaviour of polycarbonate at room-temperature. With decreasing thickness, an increasing resistance against fatigue crack propagation and an increase of the fracture toughness under static loading conditions was observed. Additional J-integral-evalutions showed a good agreement with the values of the fracture toughness. Scanning electron microscopy studies of the facture surfaces showed the sequence of damage and te individual micromechanisms of fracture. Based on th latter, detailed informations were given for the interpretation of the mechanical properties as a function of specimen-geometry.     

Über den Einfluß der spezifischen Oberfläche dielektrischer Pulversubstanzen auf die elektrischen Eigenschaften siebgedruckter Kondensatoren

On the influence of the specific surface of powdered dielectric substances on the electrical properties of screen-printed capacitors . Experiments are described to determine the influence of the specific surface of powdered dielectric substances on the electrical properties of thick-film capacitors made from this powder. Optimum values may be obtained for surface capacitance and relative dielectric constant under grinding conditions by which a specific powder surface of 4–8 m²/g is achieved. This surface range corresponds to grain size distributions with median grain diameters from approx. 1 to 4 microns. Similar optimum values are found in literature for titanate ceramics of different composition, too. The grinding conditions are stated.     

Einfluß von last- und verformungsgesteuerten mehrachsigen Beanspruchungen auf die Anrißlebensdauer

Influence of load- and deformation-controlled multiaxial tests on fatigue life to crack initiation Generally, areas of components with notches or geometrical transitions are critical because of the resulting stress/strain concentrations. In these areas due to the stress-gradients and constraint local deformations are displacement controlled even if the material's yield stress is exceeded, as long as the deformations are below the structural yield point. Therefore, load controlled tests in the elasto-plastic region with unnotched specimens from ductile materials under combined axial loading and torsion are not suitable for the interpretation of component's behaviour because of uncontrolled local deformations. Thus, the influence of multiaxial stress/strain states on the fatigue behaviour of a component under elasto-plastic deformations can be determined reliably with unnotched specimens only by deformation controlled tests, if cyclic creep is not expected in critical areas.     

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.