Numéro
J. Phys. III France
Volume 7, Numéro 9, September 1997
Page(s) 1755 - 1755
DOI https://doi.org/10.1051/jp3:1997221
DOI: 10.1051/jp3:1997221
J. Phys. III France 7 (1997) 1755-1755

Étude expérimentale du comportement cyclique d'un acier du type 316 L sous chargement multiaxial complexe en traction-torsion-pressions interne et externe

L. Bocher and P. Delobelle

Laboratoire de Mécanique Appliquée R. Chaléat URA CNRS 04, UFR Sciences et Techniques, 24 rue de l'Epitaphe, 25030 Besançon, France

(Reçu le 3 décembre 1996, révisé le 10 avril 1997, accepté le 27 mai 1997)

Abstract
This paper is concerned with the experimental determination of the behaviour of a 316 L austenitic stainless steel at room temperature and under non proportional cyclic strainings in tension-torsion- internal and external pressures. The two or three sinusoïdal strains were applied both in and out-of-phase and the main investigations deal with the additional hardening due to multiaxiality of the loadings. Typical stabilized hysteresis loops are presented. With respect to the maximum additional hardening the different tests can be classified as follows : in phase tests, out-of-phase internal-external pressures tests, out-of-phase tension-torsion tests and finally tension-torsion-pressure with significant phase angles A device is presented which allows cyclic tests to be performed on tubes for loadings in tension-torsion-internal and external pressures. It is composed of a medium pressure chamber enclosing the gage length of the test specimen, directly fixed on the specimen and connected to two pressure regulators. The specimen is also fastened to the jaws of a hydraulic tensile-torsion machine through two extension rods. The entire device is controlled with the help of strain gauges set directly on the gage zone of the test specimen. Different tests have been performed at ambient temperature on an austenitic stainless steel which has the particularity of presenting a strong supplementary hardening connected to the non-radiality of the loadings. The influence of the phase shift parameters, namely the angles  $\delta$ and $\varphi$ ( $\delta$: tension-torsion, $\varphi$: tension-pressures) for two or three cyclic sinusoïdal components and for a total equivalent strain amplitude level imposed at 0.4% was studied. The ratios of the maximum strain amplitudes were respectively fixed at r2 = 1 and $r_1 = \pm 1$ ( r2: tension-torsion and r1: tension-pressures). These tests allowed both the hypotheses made in stress calculations and the whole of the experimental set up to be validated. They are very rich in informations and lead to classify the different types of loading, with two or three cyclic components, with respect to the observed supplementary hardening. This classification was established as follows: i) The in-phase tests with two or three components ( $\delta = \varphi = 0^\circ$); no supplementary hardening is observed. ii) The tension-pressure tests such as r1 = 1, $\varphi = 90^\circ$ and r1 = - 1, $\varphi = 60^\circ$, the hardening is slightly inferior to that of tension-torsion tests. iii) The tension-torsion tests such as r2 = 1 and $\delta = 90^\circ$, where a substantial additionnal hardening takes place. iv) The tension-torsion-pressure tests where the three components are strongly shifted, namely: r1 = r2 = 1, $\delta = 90^\circ$ and $\varphi = 60^\circ$, and r2 = 1, r1 = -1, $\delta = 41.4^\circ$ and $\varphi = 82.8^\circ$. The hardening is slightly superior to the one recorded in tension-torsion. A more thorough study is in preparation which considers all the possible combinations in tension-torsion-pressures, and will be performed on the same material. The early results tend to validate the observations presented in this article.

Résumé
Cette étude réside dans la détermination expérimentale du comportement à la température ambiante de l'acier inoxydable 316 L sous chargement cyclique non proportionnel en traction-torsion-pressions interne et externe. Les deux ou trois déformations sinusoïdales appliquées sont soit en phase, soit hors-phase et l'on étudie l'amplitude du durcissement supplémentaire en fonction du degré de multiaxialité. On présente quelques boucles stabilisées typiques. Par rapport au durcissement supplémentaire maximal, les différents essais peuvent être classés comme suit : essais en phase (pas de durcissement supplémentaire), essais de traction-pressions hors-phase, essais de traction-torsion hors phase et essais de traction-torsion-pressions avec déphasages conséquents.



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