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.     

Effect of Multipor interior insulation on flanking sound transmission / Einfluss einer Innendämmung aus Multipor auf die flankierende Schallübertragung

In order to improve the energy efficiency of an existing building, it is necessary, among other things, to improve the thermal insulation provided by that building’s external walls. If the additional insulation required for this cannot be fitted on the outside, then it will need to be applied on the inside instead. To avoid the need for complex designs, insulating materials with a considerably reduced susceptibility to damage should be used, for example the mineral insulation panel Multipor. Xella Technologie‐ und Forschungsgesellschaft mbH has conducted a study in cooperation with Xella Deutschland GmbH to determine whether, and if so, how, Multipor affects structure‐borne sound transmission when used as interior insulation. The study, the results of which are presented in this article, involved testing flanking sound transmission in a laboratory at the Hochschule für Technik (HFT) in Stuttgart, Germany.     

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.     

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 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.     

Verfahren zur vollständigen Ermittlung der R‐Abhängigkeit des Rissausbreitungsverhaltens mit nur einer Probe

Procedure for the determination of the complete R‐dependency of the crack growth behaviour with only one specimen A new concept for fatigue crack propagation tests has been developed. Using a single specimen, it is possible to determine fatigue crack growth curves (da/dN ‐ ΔK) for every stress ratio between R = 0.9 and R = ‐1. Additionally, the new concept also provides threshold values for fatigue crack growth for different values of R and K_max. In combination with a continuous crack length measurement tool (such as the DC potential drop method) this testing procedure can be performed with minimal effort of personnel and time. The test procedure consists of a sequence of K_max‐constant tests with decreasing crack growth rates. As the applied K_max is increasing stepwise there should be no load history effects. According to the procedures described in the ASTM Standard E 647, the results using this new testing procedure fit very well to the da/dN ‐ ΔK curves generated with different specimens. The tests also fulfil all the requirements of ASTM Standard E 647.     

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.     

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.     

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.