[en] Within a German PRCV-program at the Institut fuer Massivbau of the Technical University of Munich tests are made in order to provide the information necessary for an analytical modelling of thick concrete cylinders. In 1976 the series was started with 2 tests on large size unreinforced concrete rings (inner diameter 10.9 cm, outer diameter 36.5 cm resp. 62.5 cm, thickness 10 cm) under inside pressure. The loading was electronically controlled under the condition of a linear increase of the mean strain rate (0.0002/hour). This method provides detailed information on the deformation behavior during rupture of the specimen. The main strain was measured at the inner side of the ring by 8 inductive gages. To obtain the information necessary for a finite element analysis the specimen was subdivided by a triangular net for which all tangential strains have been measured by inductive gages, whereas all radial and diagonal strains have been measured using strain gages. Additionally the increase of the ring diameter has been recorded. (Auth.)
Source
Jaeger, T.A.; Boley, B.A. (eds.); International Association for Structural Mechanics in Reactor Technology; Commission of the European Communities, Brussels (Belgium); v. H p. H4/8 1-11; ISBN 0 444 85062 7; 
; 1977; v. H p. H4/8 1-11; North-Holland; Amsterdam, Netherlands; 4. international conference on structural mechanics in reactor technology; San Francisco, USA; 15 - 19 Aug 1977
; 1977; v. H p. H4/8 1-11; North-Holland; Amsterdam, Netherlands; 4. international conference on structural mechanics in reactor technology; San Francisco, USA; 15 - 19 Aug 1977
[en] This paper presents three tests on thick-walled concrete cylinders loaded by an interior pressure. The specimens were not reinforced. They had an inner diameter of 21.8 cm, an outer diameter of 73.0 and 125.0 cm and were 10 cm thick. Shrinkage effects were prevented as well as possible. The strains were measured by electric gages, which formed a triangular mesh on the upper face of the specimen. The increase of pressure was controlled by the condition of linear increase of the tangential strains at the inner perimeter of the ring. By this method it was possible to measure the strains even in the phase of failure. At the inner diameter strains about 0.5 per mill were measured without visible cracks. These strains were observed over a gage-length of 10 cm. Therefore, it can be assumed that at the cracking-point was an even higher strain. At the point where cracking occured, micro-cracking caused a decrease of strains and stresses in the neighbouring zones before the cracks were visible. The specimens failed after reaching the maximum load in a falling branch of the load. The failure occured suddenly by a primary crack and a secondary crack at the opposite side. The maximum inside pressure depended in a small range on the size of the cylinders. The results were analysed by available theories and compared with similar tests of Martin. The interpretation of the maximum load depends in a big range on the assumptions of the tensile strength of the concrete (axial tensile strength, bending tensile strength, tensile stresses after microcracking). Hereby exists a wide scale which complicates a definite statement. Further research must be done to examine the material law of concrete in the tensile range. Only by this way a definite solution for concrete cylinders with inside pressure is possible. (orig.)
[de]
Es wurde ueber drei Versuche an Betonringen mit Innendruckbeanspruchung berichtet. Die Ringe waren unbewehrt. Sie hatten einen Innendurchmesser von 21,8 cm, einen Aussendurchmesser von 73,0 bzw. 125,0 cm und waren 10 cm dick. Schwindeinfluesse konnten weitgehend ausgeschlossen werden. Die Verformungen wurden durch ein engmaschiges Netz von Messstrecken verfolgt. Die Belastung erfolgte automatisch so, dass die Dehnung am Innenrand linear mit der Zeit anstieg. Dadurch war auch in der Bruchphase noch eine lueckenlose Erfassung der Verformungen moeglich. Am Innenrand der Ringe wurden ohne sichtbare Rissbildung Dehnungen bis etwa 0,5 per mill gemessen. Diese Werte fand man ueber Messlaengen von etwa 10 cm. Man muss deshalb annehmen, dass oertlich noch erheblich groessere Dehnungswerte auftraten. Trotz des Fehlens sichtbarer Risse erfolgte sicher an den spaeteren Bruchstellen in der Endphase des Versuches eine Mikrorissbildung, die in den benachbarten Bereichen zu einem Dehnungs- bzw. Spannungsabfall fuehrte. Der Bruch erfolgte zum Teil erst im Bereich fallender Last. Die schlagartige Bildung eines durchgehenden Primaerrisses an einer Ringseite erzwang einen Sekundaerriss auf der gegenueberliegenden Seite. Die maximal erreichten Innendruecke waren nur wenig von den Ringabmessungen abhaengig. Es wurde versucht, die gefundenen Hoechstlasten anhand bekannter Theorien zu analysieren. Dabei wurden auch vergleichbare Versuche von Martin herangezogen. Die Deutung der erzielten Hoechstlasten ist in starkem Masse von den Annahmen ueber die Zugfestigkeit des Betons abhaengig (zentrische Zugfestigkeit, Biegezugfestigkeit, Zugspannungen nach Mikrorissbildung). Hier besteht ein relativ grosser Spielraum, der definitive Angaben schwierig macht. Die Werkstoffgesetze fuer zugbeanspruchten Beton muessten weiter studiert werden, da nur auf diesem Wege eine endgueltige Klaerung des Tragverhaltens von innendruckbeanspruchten Ringen herbeigefuehrt werden kann. (orig.)Source
Schriftenreihe des Deutschen Ausschusses fuer Stahlbeton; no. 299; 1978; 64 p; Deutscher Ausschuss fuer Stahlbeton; Berlin (Germany, F.R.); ISBN 3 433 00838 8; ; CONTRACT RK 21 I
; CONTRACT RK 21 I
[en] The interdiffusivity of Al and the transition metal solutes Ti, V, Cr, Mn, Fe, Nb, Mo, Ru, Ta, W, and Re in fcc Co is characterized at 1373 K, 1473 K and 1573 K by binary diffusion couples. The experimental results are complemented by first-principles calculations in combination with kinetic Monte Carlo simulations to investigate the diffusion of Re, W, Mo and Ta in fcc Co. The interdiffusion coefficients of alloying elements in fcc Co are generally smaller than in fcc Ni, but the correlation between interdiffusion coefficients and the atomic number of metal solutes is comparable in Co and Ni. With increasing atomic number and decreasing atomic radii the interdiffusion coefficients of the investigated elements, except for Mn and Fe, decrease strongly. The trends in the diffusivity determined by experiment and simulation are in excellent agreement. Re is the slowest diffusing element in fcc Co among the investigated elements. The electronic structure calculations indicate that this is caused by strong directional bonds between Re and neighboring Co atoms. The overall lower diffusivity of solute atoms in Co as compared to Ni suggests that diffusion controlled processes could be slower in Co-base superalloys.
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