Filters
Results 1 - 10 of 52
Results 1 - 10 of 52.
Search took: 0.031 seconds
| Sort by: date | relevance |
[en] The damage and rupture mechanisms of thin sheets of 2024 aluminum alloy (Al containing Cu, Mn, and Mg elements) are investigated. Two grades are studied: a standard alloy and a high damage tolerance alloy. The microstructure of each material is characterized to obtain the second phase volume content, the dimensions of particles and the initial void volume fraction. The largest particles consist of intermetallics. Mechanical tests are carried out on flat specimens including U-notched (with various notch radii), sharply V-notched and smooth tensile samples. Stable crack growth was studied using 'Kahn samples' and pre-cracked large center-cracked tension panels M(T). The macroscopic fracture surface of the different specimens is observed using scanning electron microscopy. Smooth and moderately notched samples exhibit a slant fracture surface, which has an angle of about 45 deg. with respect to the loading direction. With increasing notch severity, the fracture mode changes significantly. Failure initiates at the notch root in a small triangular region perpendicular to the loading direction. Outside this zone, slant fracture is observed. Microscopic observations show two failure micromechanisms. Primary voids are first initiated at intermetallic particles in both cases. In flat regions, i.e. near the notch root of severely notched samples, void growth is promoted and final rupture is caused by 'internal necking' between the large cavities. In slanted regions these voids tend to coalesce rapidly according to a 'void sheet mechanism' which leads to the formation of smaller secondary voids in the ligaments between the primary voids. These observations can be interpreted using finite element simulations. In particular, it is shown that crack growth occurs under plane strain conditions along the propagation direction
Journal
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing; ISSN 0921-5093; 
; CODEN MSAPE3; v. 380(1-2); p. 356-364
; CODEN MSAPE3; v. 380(1-2); p. 356-364
[en] In a French pressurized water reactor (PWR), most of the structural parts of the fuel assembly consist of zirconium alloys (ZIRCALOY-2). The mechanical behavior of ZIRCALOY-4 sheets is investigated at room temperature. The effect of hydride precipitation on the mechanical behavior and on the rupture mechanism is also studied, in the range from 200 to 1,200 wt ppm hydrogen and for different stress triaxialities. It is shown that the material exhibits a strong anisotropy die to its pronounced texture, and that its mechanical properties depend on the strain rate. Hydride precipitation appears to have no effect on the anisotropy or on the strain-rate sensitivity, in the range from 10-4 to 10-2 s-1. The main effect of hydrogen is the reduction of the ductility and of crack resistance. The ductile rupture mechanism is studied, focusing on the stage of damage nucleation by hydride fracture. Observations during scanning electron microscopy (SEM) in situ tests show that hydrides allow the transmission of slip, which occurs in ZIRCALOY-4 grains. Hydrides can also deform, together with surrounding zirconium matrix. Damage appears after a plastic-strain yield of about 14 to 25 pct. Fracture occurs first on intergranular hydrides. Fracture of transgranular hydrides is observed only prior to failure, for higher plastic strains
Journal
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science; ISSN 1073-5623; ; CODEN MMTAEB; v. 31(3); p. 679-690
; CODEN MMTAEB; v. 31(3); p. 679-690
[en] The spectrometer designed by ONERA and IASB (Belgium Space Aeronomy Institute) to measure atmospheric trace constituents was flown aboard Spacelab 1 during the 9 th mission of the American Space Shuttle from November 28 to December 8, 1983. After a brief summary of the history of the project related to Spacelab, the mechanical and thermal design of the spectrometer is described. Some methods, calculations and characteristic tests are detailed as examples. The behaviour of the experiment during the mission and the results of the post-flight tests are shortly analyzed in order to prepare the qualification for a reflight
[fr]
Le spectrometre realise par l'ONERA et l'IASB (Institut d'Aeronomie Spatiale de Belgique) pour mesurer les composants de l'atmosphere a ete embarque a bord du Spacelab et a vole au cours de la 9e mission de la navette spatiale americaine qui s'est deroulee du 28 novembre au 8 decembre 1983. Apres un bref rappel historique du deroulement du projet dans le cadre du Spacelab, les conceptions mecanique et thermique du spectrometre sont decrites et illustrees par la presentation de quelques methodes, calculs ou essais typiques. L'analyse du fonctionnement de l'appareil pendant la mission, l'examen de celui-ci apres le vol et les conditions a remplir pour un nouveau vol sont ensuite rapidement abordesJournal
[en] Coatings of ZrSi/Zr2Si on zirconium were prepared by deposition of silicon from monosilane on heated zirconium samples. The oxidation of these coatings by oxygen or water vapour follows the general rate law (Δm)sup(n) = kt (n approximately = 1.6). These kinetic results can be explained by the existence of two different silicide layers. At the lowest water vapour pressures, the kinetic behaviour is different; the formation of volatile SiO can account for this phenomenon. The experiments have shown the good corrosion resistance of this coating compared with that of pure zirconium. For example, in oxygen atmospheres the weight gains are about eight times less for silicides than for zirconium. (author)
Source
Holmes, D.R. (Central Electricity Research Labs., Leatherhead (UK). Materials Div.); Rahmel, A. (DECHEMA Deutsche Gesellschaft fuer Chemisches Apparatewesen e.V., Frankfurt am Main (Germany, F.R.)) (eds.); p. 387-398; ISBN 0-85334-784-0; ; 1978; p. 387-398; Applied Science Publishers; London; International conference of the European Federation of Corrosion's working party 'Corrosion by hot gases and combustion products'; Duesseldorf, West Germany; 17 - 18 May 1977
; 1978; p. 387-398; Applied Science Publishers; London; International conference of the European Federation of Corrosion's working party 'Corrosion by hot gases and combustion products'; Duesseldorf, West Germany; 17 - 18 May 1977
[en] Melting of 4He has been observed at 297 K and 115+-2 kilobars. This value is close to that derived from Simon's equation, extrapolated from 5 kilobar data. The diamond cell used is a new design and allows inert gases to be studied between 4 and 500 K up to 1 megabar
Journal
Journal de Physique. Lettres; ISSN 0302-072X; ; v. 40(13); p. L.307-L.308
; v. 40(13); p. L.307-L.308
| 1 | 2 | 3 | Next |