Eigenspannungsverteilung in zylindrischen Körpern. Auswirkung der angewendeten Berechnungsverfahren

Determining the Distribution of Residual Stresses in Cylindrical Solid Bodies by Employing Different Computation Methods There are two methods for the computation of residual stresses in cylindrical bodies. The methods in question are by G. Sachs and E. Krägeloh. The residual stresses are computed out off the determined stresses. The basis of the two methods are two different hypothesises with different assumed tension gradients and elongation gradients across the sample cross-section. The methods differentiated for homogeneous and inhomogeneous materials meet with their differential equation the balance conditions. The different methods employed show considerable differences in regard to circumferential tensions. This differences result particularly at the cylinder wall surface (outside). The tension differences grow with increasing cylinder wall thickness. The longitudinal tensions and radial tensions computed by the methods of G. Sachs and E. Krägeloh are nearly identical. It is much more important to know the tendency of the residual stress distribution in a given solid body than to know the absolute value of the residual tension conditions. It is to recommend, to employ the method developed by G. Sachs, because the computing expenditure is much less than the one necessary for the method of E. Krägeloh.     

Berechnung von Eigenspannungen in metallgespritzten rotationssymmetrischen Körpern

Computation of Residual Stresses in Metal-Sprayed Solid Bodies Presenting Rotation Symmetry Residual stresses are internal tensions in a workpiece without acting forces and moments on the solid body. The knowledge of the residual stresses can be very interesting because the superposition with tensions from forces and moments can produce a unfavorable state of stresses. Based on the reflektions for the computation of residual stresses in homogen materials the general equations for inhomogen materials and the equations for the special case of a solid body consisting of two layers are differentiated. A simple evaluation is shown. In a special case the solid body is taken as inhomogen, while the layers are homogen and isotropic. The equations are employed for metal-sprayed bodies and for all other laminated systems of two layers presenting rotation symmetry. There are press fits, shrink fits, clad steel a.s.o. Different hypothesis for computation the circumferential tension show two different solutions with two different results.     

Untersuchung der Reaktionsvorgänge zwischen gasförmigen und festen Metallen

Reaction of gaseous with solid metals . The reaction of gaseous zinc and cadmium with solid copper, silver, palladium and palladium silver alloys were investigated at various temperatures. Besides the cleanliness of the metal surfaces various other factors influence the zink tak up e. g. the shape of the surface. More than up to now it has to be kept in mind, that the zinc atoms spread as directed atomic beams. This results in possibilities of influencing the zinz up take.     

Über die Unvereinbarkeit der drei Keplerschen Gesetze mit der Aristotelischen Mechanik

Kepler's three laws are shown to be inconsistent with Aristotelian dynamics. In his “Epitome” Kepler came close to this difficulty. However, by an unfortunate analogy he failed to realize its significance.     

Beitrag zur Mechanik der Kaltumformung von Metallen

Ohne Zusammenfassung Schlu? der Aufsatzes aus Heft 6 (1971) S. 198/204.     

Einfluß der Herstellungsbedingungen von Doppel-V-Kerben an Prüfkörpern für den Schlagbiegeversuch nach DIN 53 753

Influence of the Manufacturing Process of Double V-Notches of the Test Specimens In connexion with DIN 53 753 ?Impact bending test on a test specimen with a hole-notch or double V-notch”? tests were carried out on test specimen whose notches had been manufactured by different procedures (by planing and by placing the notches into the injection mould). Four different thermoplastics – some of them short-glassfiber reinforced–were used. Proof was gained that all specimens with a notch radius of 0.5 mm will break and that hardly any differences between ?planed”? and ?injected”? notches will exist. With the possibility of selecting one particular radius it has become feasible to draw comparisons between the individual plastics as to their impact strengths. Microtome cuts, SEM-micrographs of the area of fracture and orientation measurements with the aid of a micropolariscope complete the investigations.     

Statische und dynamische Dauerfestigkeit von Aluminiumoxid-Sinterkörpern

Static and Dynamic Fatigue Strength of Sintered Alumina Ceramics The investigation have indicated that also high strength ceramic materials with practically no plasticity show similar “Wöhler-graphs” to plastically deformable materials such as steel, according to the measurements described here. Such “Wöhler” -like graphs apply to flexural, tensile and compressive strains as well as to the resistance against impact. After these results it can be concluded that a lower threshold exists for mechanical stresses below which the crack propagation comes to a stop. This leads to the conception of fatigue strength. The assumption of such a threshold value is not unopposed in theory however. It is therefore essential that more investigations be carried out over a longer period of time in order to answer this question finally.     

Mechanische Bearbeitung sprödharter Körper und Grenzflächenwechselwirkungen

The effect of surface adsorption on the machining of brittle materials In the present paper is shown the importance of interfacial phenomena in the machining (grinding, cutting) of brittle materials. Especially influenced are the rate of the abrasion, the cutting forces and the roughness of the surface.     

Eine Apparatur zur Desorptionsspektroskopie an porösen Festkörpern bei tiefen Temperaturen

A newly developed apparatus for Temperature Programmed Desorption spectroscopy (TPD) in the temperature range between 10 and 100 K is presented. It is provided for the investigation of porous solids especially for use in vacuum engineering, for instance activated charcoal and zeolithe. Favoured working regime is a linear temperature schedule with some parts of a Kelvin per minute, but all other schedules and a variation of the heating rate over the factor 10 are also available. The whole measuring process takes place automatically and under computer control – so a simultaneous registration of a large number of measured gases is possible.     

Im Körper gebrochene Knochenplatten — Schadenanalyse und Biomechanik

Osteotomy Plates which Failed in Vino — Failure Examination and Biomechanics. Two fractured bone plates, which were used in a subtrochanteric osteotomy, have been examinated. The fatigue failure and additional fracture-characteristics are easily to understand in regarding the stresses, acting in the plates. An evaluation shows, that such a plate should never bear any part of the body weight but should be used only for fracture-fixation.     

Herstellung von hochporösen,endkonturnahen Titan‐Formkörpern für biomedizinische Anwendungen

Near‐net‐shape manufacturing of highly porous titanium parts for biomedical applications The production of highly porous titanium parts is attractive for biomedical applications. Preferrentially, these parts are produced by powdermetallurgical means using suitable spacer materials. Porosities up to 75 % and well defined pore sizes in the range of 0.1 to 2.0 mm are achieved adjusting the amount and the particle size of the spacer material. Up to now, near‐net‐shape manufacturing of highly porous parts was hindered by the plastic deformation of the sintered network during machining leading to a partial or complete closing of the open porosity. A new manufacturing route is presented, where the shaping is already done in the unsintered state starting from pressed compacts. The stability of the compacts was found to be sufficient to machine the compacts without additional binders. The manufacturing route was successfully applied to the prototype of an acetabular cup. Additionally, some investigations are presented characterizing the highly porous titanium.     

Zur Anwendung desRitzschen Verfahrens auf polygenetische Probleme der Mechanik

Zusammenfassung Verschiedene Verfahren der Umformung und der Erg?nzung polygenetischer Aufgaben zu monogenetischen werden im Hinblick auf die anschlie?ende Anwendung des Ritzschen Verfahrens miteinander verglichen.