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.     

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.     

Über den Einfluß der Probengeometrie auf die Rißausbreitungsgeschwindigkeit bei Spannungsrißkorrosionsversuchen

The influence of specimen geometry on stress corrosion cracking rates The fracture mechanics characterization of stress corrosion cracking phenomena established the quantitative relation between the stress field around the crack front and the stress corrosion cracking rates. In order to apply the results successfully in structural design, the influence of specimen geometry and test conditions have to be eliminated or minimized. Great experimental efforts are applied worldwide to develop such a testing procedure. The following work is directed to some of the effects resulting from specimen geometry, such as the numerical equations used to obtain the stress-intensity factors, the specimen thickness and crack length.     

Ermittlung der Fließortkurven anisotroper Werkstoffe durch harmonische Analyse

The Determination of Yield Loci of Anisotropic Materials by Harmonic Analysis The method of harmonic analysis for periodic phenomenons is applied to the representation of yield loci described in [2]. This method allows the calculation of yield loci determined by static and kinematic data obtained with plane stress state.     

Ermittlung von Umformeigenspannungen in Tiefziehnäpfen durch Neutronenbeugung

Determination of deformation-induced residual stresses in deep-drawn cups through neutron diffraction Deformation-induced residual stresses in cups of CuZn sheet produced by deep-drawing and similar forming processes were determined by means of neutron diffraction. The experimental procedure is described. Test results were compared with those of X-ray diffraction and mechanical methods whereby only neutron diffraction enables to determine the distribution of residual stresses in sheet thickness direction.     

Einfluß der Unterbrechergeometrie auf die Arbeitsübertragung und den Wirkungsgrad von Seitenkanalverdichtern

Zusammenfassung Zur Trennung von Druck- und Saugseite des Seitenkanals ist ein Unterbrecher erforderlich, der das direkte überstr?men des verdichteten Gases verhindert. Der Unterbrecher bewirkt aber nicht nur die Abdichtung, sondern er beeinflu?t auch wesentlich den Expansionsvorgang des überstr?menden Unterbrechermassestromes und damit wiederum den Verdichtungsvorgang im Seitenkanal. Um den Einflu? der Unterbrechergeometrie auf diese Vorg?nge zu ermitteln, wurden unterschiedliche Unterbrechermodule in einem Seitenkanalverdichter bei Druck- und Vakuumbetrieb untersucht. Der Umfangswinkel des Unterbrechers und die Oberfl?chengeometrie beeinflussen den Expansionsvorgang und den polytropen Kupplungswirkungsgrad unterschiedlich im Bereich von η=0,41 bis 0,49. Damit ist aufgezeigt, da? eine Optimierung des Unterbrechers notwendig ist, um m?glichst adiabate Zustands?nderungen im Seitenkanalverdichter zu erreichen. Der relative Unterbrecherwinkel soll für Schaufelzahlen von 40 bis 60 α_U/2π=0,115 bis 0,135 betragen.     

Einfluß von Überlasten auf die Ausbreitung von Ermüdungsrissen in der Aluminiumlegierung 7075 T 7351

Influence of overloads on the propagation of fatigue cracks in the aluminium alloy 7075 T 7351 For realistic lifetime predictions the crack propagation behaviour under variable amplitude spectrum loads has to be known. In this work the influence of single overloads on the fatigue crack propagation in the alloy 7075 T 7351 was investigated at a constant loading level (K_max and ΔK = const.). The experiments showed, that a single overload causes a short crack acceleration followed by a pronounced deceleration of the crack propagation rate. After this deceleration at higher overloads a zone where the crack propagation rate is slightly increased (lost retardation) was observed. It has been shown, that the minimum crack propagation rate as well as the length of the influenced region depends on the height of the overload. The observed crack acceleration, the deceleration as well as the lost retardation can be explained by internal stresses caused by those overloads which have to be added to the external stresses.     

Über die Verfahren des Aufschweißens von Kontaktbelägen auf ihre Träger

Electrical resistance welding — properties and functions . The article describes the five different welding systems which are based on the princip of the electrical resistance welding and states their properties and functions. Good welding has pushed aside the traditional riveting and is now an indispensable aid for the production of electrical contacts. The advantages and disadvantages of each process are also displayed. The knowledge of these factors makes it possible to choose the right way of production for each case.     

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.     

Der Einfluß von Festigkeit und Druckeigenspannungen auf die Wechselfestigkeit von Stählen bei höheren Temperaturen

Influence of Hardness and Comprehensive Residual Stresses on the Fatigue Limit of Steels under Elevated Temperatures The room temperature fatigue behaviour under alternating stresses of bcc steels is characterized by two stationary states existing below two different reversed stress limits: Below the one no crack initiation occurs, below the other no crack propagation can be found even after an unlimited number of stress cycles. The fatigue endurance of unnotched parts is determined by the crack initiation conditions that can be improved by higher hardness of the material. The fatigue strength of notched parts under reversed stresses is decidently determined by the minimum stress required to propagate a crack; this stress can be raised by compressive residual stresses. – At elevated temperatures these two stationary states are not further existent and there are no alternating stress amplitudes that can be endured either without crack initiation or without crack propagation to fracture. Both influencing parameters hardness and compressive residual stresses are dependend on the temperature, this can be explained by Snoek's and by Cottrell's mechanisms and with the temperature depending release of residual stresses corresponding to the temperature sensitive yield point.     

Über die Eignung der Wechselbiegemaschine „WEBI”︁ zur Ermittlung von Ermüdungskennwerten

On Alternating Bending Machine WEBI's Suitability for Determination of Fatigue Characteristics Already in 1966, experimental investigations revealed that the flat bending torsion testing machine ?FLATO”? (Schenck, Darmstadt) doesn't keep constant its torsional moment amplitude in case of specimen's fatigue softening or hardening, respectively. Thus. conclusions concerning the material's fatigue characteristics drawn from such experimental results might therefore be seriously false. Furthermore, also the alternating bending testing machine ?WEBI”? (Schenck, Darmstadt) shows an equivalent behaviour concerning its bending moment amplitude. For this reason. the main findings of a comprehensive experimental study carried out on WEBI with an unalloyed steel C 45 (0.45 mass perccnl C) in different heat treatment conditions are reported in this paper.     

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 von unterschiedlichen Erwärmungen auf die Festigkeit und die elektrische Leitfähigkeit einer ausgehärteten AlCu2MgNi-Legierung

Influence of Various Heating of Age Hardened AlCu2MgNi, Alloy on Mechanical Strength and Electrical Conductivity In-service or unintended heating above certain temperatures and periods affect the mechanical properties of age hardened aluminum alloys. Non destructive evalution of strength reduction is very difficult especially in the case of minor heat damage. The effect and assessment of various heating on tensile strength, hardness and electrical conductivity of an airplane wheel rim is investigated.     

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.     

Ermittlung von Spannungsintensitätsfaktoren aus Isochromaten mittels einer Vielparameter-Vielpunkt-Methode

Determination of Stress Intensity Factors from Isochromatics by means of a Multiparameter-Multipoint-Method A multi-parameter-multiple-point method (VPVP-method) for determination of mode-1 stress intensity factors from isochromatic fringe patterns has been developed and tested in connection with practical examples. In particular the stress field behaviour in compact-tension specimens is thoroughly investigated where variable numbers of series coefficients in the stress field expansion and a variety of data-point combinations featuring remoted and close field influences has been utilized. Cracks approaching free specimen boundaries have been given special attention.