FR2944600A1 - Parallelepiped shaped fatigue test specimen developing method for determining fatigue behavior of material, involves determining final geometry and final inclination angle of fatigue test specimen when desired biaxiality ratio is attained - Google Patents
Parallelepiped shaped fatigue test specimen developing method for determining fatigue behavior of material, involves determining final geometry and final inclination angle of fatigue test specimen when desired biaxiality ratio is attained Download PDFInfo
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- FR2944600A1 FR2944600A1 FR0952517A FR0952517A FR2944600A1 FR 2944600 A1 FR2944600 A1 FR 2944600A1 FR 0952517 A FR0952517 A FR 0952517A FR 0952517 A FR0952517 A FR 0952517A FR 2944600 A1 FR2944600 A1 FR 2944600A1
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- ratio
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- biaxiality
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- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000009661 fatigue test Methods 0.000 title claims abstract description 14
- 238000012360 testing method Methods 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 2
- 238000013100 final test Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0073—Fatigue
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/0202—Control of the test
- G01N2203/0212—Theories, calculations
- G01N2203/0216—Finite elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0254—Biaxial, the forces being applied along two normal axes of the specimen
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0258—Non axial, i.e. the forces not being applied along an axis of symmetry of the specimen
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
Description
Domaine de l'invention La présente invention se rapporte au domaine des essais de fatigue et elle concerne plus particulièrement un procédé d'élaboration d'une éprouvette pour de tels essais permettant de solliciter en fatigue la matière dont elle est faite avec un état de contrainte multiaxiale et un rapport de contrainte différent de l'unité. FIELD OF THE INVENTION The present invention relates to the field of fatigue tests and more particularly relates to a method for producing a specimen for such tests that makes it possible to stress the material of which it is made with a state of stress. multiaxial and a stress ratio different from the unit.
Art antérieur L'étude des comportements des matériaux en fatigue est un domaine d'activité ancien qui pour des raisons de coût met en oeuvre des machines de fatigue essentiellement de type uni-axiale. Il existe aussi des machines plus complexes mettant en oeuvre des éprouvettes spécifiques permettant de réaliser des essais multiaxiaux. Toutefois, ces machines sont fort peu répandues et très onéreuses. Aussi, il a donc été proposé dans la demande de brevet française N°2914420, un nouveau type d'éprouvette de fatigue permettant au moyen d'une simple machine de fatigue uni-axiale de créer des conditions d'une sollicitation bi-axiale au niveau de cette éprouvette. Malheureusement, de part sa structure figée, cette éprouvette présente l'inconvénient de ne permettre des essais de fatigue que pour un rapport de contrainte oy/ox égale à l'unité. PRIOR ART The study of the behavior of materials in fatigue is a field of old activity which for cost reasons uses fatigue machines essentially uni-axial type. There are also more complex machines using specific specimens to perform multiaxial tests. However, these machines are very sparse and very expensive. Also, it has been proposed in the French patent application No. 2914420, a new type of fatigue test piece allowing by means of a simple uni-axial fatigue machine to create conditions of a bi-axial stress at level of this test piece. Unfortunately, because of its fixed structure, this test has the disadvantage of only allowing fatigue tests for a stress ratio oy / ox equal to unity.
Objet et définition de l'invention L'objet de la présente invention est donc de proposer une solution qui permettre de s'affranchir de ce rapport unitaire et donc de permettre de réaliser des éprouvettes de fatigue dont le rapport de contrainte peut être prédéfini à la demande de son utilisateur. OBJECT AND DEFINITION OF THE INVENTION The object of the present invention is therefore to propose a solution that makes it possible to overcome this unitary ratio and therefore to make it possible to produce fatigue specimens whose stress ratio can be predefined to the request from its user.
Selon l'invention, il est proposé un procédé d'élaboration d'une éprouvette de fatigue de forme parallélépipédique dont la partie médiane est rétrécie de façon à créer deux bras se croisant au centre géométrique de l'éprouvette et inclinés chacun d'un même angle d'inclinaison nominal, procédé comportant les étapes suivantes : . définition d'une géométrie nominale d'éprouvette et paramétrage de cette géométrie nominale en trois dimensions, . génération d'un maillage par un calcul d'éléments finis à partir de la géométrie définie préalablement, . détermination d'un rapport de biaxialité audit centre géométrique, . tant qu'un rapport de bixaialité souhaité n'est pas atteint, incrémentation dudit angle d'inclinaison et génération d'un nouveau maillage, . une fois ledit rapport de biaxialité souhaité atteint détermination d'une géométrie finale d'éprouvette et d'un angle d'inclinaison final. De préférence, ledit angle d'inclinaison nominal est égal à 30° et ledit angle d'inclinaison final est supérieur à 30° et inférieur ou égal à 45°. Avantageusement, ladite incrémentation est effectuée par pas de 0,05°. According to the invention, there is provided a method for producing a parallelepiped-shaped fatigue test specimen whose median portion is narrowed so as to create two arms crossing at the geometrical center of the test-tube and inclined each one of the same nominal inclination angle, the method comprising the following steps: definition of a nominal specimen geometry and parameterization of this nominal geometry in three dimensions,. generating a mesh by finite element calculation from the previously defined geometry,. determining a biaxiality ratio at said geometric center,. as long as a desired bixaiality ratio is not achieved, incrementing said tilt angle and generating a new mesh,. once said desired biaxiality ratio reaches a final test piece geometry and a final tilt angle. Preferably, said nominal angle of inclination is equal to 30 ° and said final inclination angle is greater than 30 ° and less than or equal to 45 °. Advantageously, said incrementation is performed in steps of 0.05 °.
L'invention concerne également une éprouvette de fatigue obtenue au moyen du procédé d'élaboration d'éprouvettes précité ainsi qu'un procédé de détermination du comportement d'un matériau à la fatigue selon deux axes de sollicitation, caractérisé en ce qu'il consiste à soumettre une telle éprouvette formée dudit matériau à une traction alternée uniaxiale de le sens de sa longueur. The invention also relates to a fatigue test piece obtained by means of the aforementioned test specimen preparation method and to a method for determining the behavior of a fatigue material according to two loading axes, characterized in that it consists of subjecting such a test piece formed of said material to uniaxial alternating traction in the direction of its length.
Brève description des dessins D'autres caractéristiques et avantages de la présente invention ressortiront mieux de la description suivante effectuée à titre indicatif et non limitatif en regard des dessins annexés sur lesquels : 3 la figure 1 montre les différentes étapes du procédé d'élaboration d'éprouvettes de fatigue selon l'invention, et les figures 2A et 2B illustrent deux exemples d'une éprouvette de fatigue obtenue par le procédé d'élaboration de la figure 1. BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will emerge more clearly from the following description given by way of non-limiting indication with reference to the appended drawings, in which: FIG. 1 shows the different steps of the production process of FIG. fatigue test pieces according to the invention, and FIGS. 2A and 2B illustrate two examples of a fatigue test piece obtained by the method of preparation of FIG.
Description d'un mode préférentiel de réalisation L'invention se propose de réaliser une éprouvette de fatigue de forme particulière qui mise en traction uni-axiale sur une machine de fatigue uni-axiale permet d'obtenir un champ de contrainte multiaxial aux propriétés souhaitées par son utilisateur. Plus particulièrement, il est proposé un procédé d'élaboration d'éprouvettes de fatigue qui permet d'obtenir sur ces éprouvettes un rapport de biaxialité R (contrainte minimale/contrainte maximale ou oy/ox) différent de 1. La figure 1 illustre les différentes étapes de ce procédé. La première étape 100 consiste à définir la géométrie nominale de l'éprouvette à réaliser. Celle-ci pourra par exemple être prise conforme à celle de la demande française décrite en préambule de la présente demande, c'est-à-dire en forme de plaquette parallélépipédique avec deux bras symétriques se croisant dans sa partie médiane en son centre géométrique. DESCRIPTION OF A PREFERRED EMBODIMENT The invention proposes to produce a fatigue test specimen of a particular shape that puts in uniaxial traction on a uni-axial fatigue machine makes it possible to obtain a multiaxial stress field with the properties desired by his user. More particularly, it is proposed a method for producing fatigue specimens which makes it possible to obtain on these specimens a biaxiality ratio R (minimum stress / maximum stress or oy / ox) different from 1. FIG. steps of this process. The first step 100 consists in defining the nominal geometry of the specimen to be produced. This may for example be taken in accordance with that of the French application described in the preamble of the present application, that is to say in the form of parallelepipedal plate with two symmetrical arms intersecting in its middle part in its geometric center.
L'inclinaison initiale ou nominale ao des deux bras de l'éprouvette est égale à 30%, ce qui correspond à un rapport de biaxialité égal à l'unité. Une fois cette géométrie nominale définie, elle fait l'objet dans une étape 102 d'un paramétrage 3D puis dans une étape 104 il lui est appliqué un calcul par éléments finis pour générer un maillage de l'éprouvette préalablement paramétrée. Il est alors procédé dans une étape suivante 104 au calcul du rapport de biaxialité R au centre géométrique de l'éprouvette, c'est-à-dire précisément au croisement de ces deux bras. Dans le cas de l'éprouvette nominale, ce rapport initial est égal à 1. Ensuite, selon le rapport de biaxialité souhaité par l'utilisateur Rvisé (résultat du test 108) et tant que le rapport visé n'est pas atteint, il est procédé dans une étape 110 à l'incrémentation de l'angle d'inclinaison des bras d'un angle Aa (de préférence égal à 0,05°) et il est fait retour à l'étape 104 pour un nouveau calcul par éléments finis sur la base de la nouvelle valeur de l'angle d'inclinaison. Lorsque le rapport visé est enfin atteint (réponse oui au test de l'étape 108), la boucle d'optimisation du calcul par éléments finis est arrêtée et dans une étape finale 112 la géométrie finale de l'éprouvette avec son angle d'inclinaison final afin est alors délivrée. Les figures 2A et 2B montrent deux exemples d'éprouvettes de fatigue obtenues avec le procédé décrit précédemment. Dans le premier exemple, l'angle final obtenu est de 41,25° correspondant à un rapport de biaxialité de 0,5 alors que dans le second exemple l'angle final obtenu est de 37,5° correspondant à un rapport de biaxialité de 0,8. Ainsi, avec le procédé selon l'invention, il est possible, de façon simple, d'obtenir tout rapport de biaxialité différent de l'unité. En pratique, il est possible d'obtenir une éprouvette ayant un angle d'inclinaison final de ses bras supérieur à 30° et inférieur ou égal à 45°. Une fois réalisée dans le matériau à tester, l'éprouvette selon l'invention peut être sollicitée par une traction alternée dans le sens de sa longueur de façon à créer une sollicitation de fatigue bi-axiale sur sa partie médiane, laquelle au bout d'un nombre de cycles à déterminer va entrainer des fissures puis une rupture du matériau nécessaire à la connaissance de son comportement en fatigue. The initial or nominal inclination ao of the two arms of the specimen is equal to 30%, which corresponds to a ratio of biaxiality equal to unity. Once this nominal geometry is defined, it is the subject in a step 102 of a 3D parameterization and in a step 104 it is applied a finite element calculation to generate a mesh of the specimen previously parameterized. It is then proceeded in a next step 104 to calculate the biaxiality ratio R at the geometric center of the specimen, that is to say precisely at the intersection of these two arms. In the case of the nominal specimen, this initial ratio is equal to 1. Then, according to the ratio of biaxiality desired by the user Rvisé (result of the test 108) and until the target report is reached, it is in a step 110 increments the angle of inclination of the arms by an angle Aa (preferably equal to 0.05 °) and is returned to step 104 for a new finite element calculation on the basis of the new value of the angle of inclination. When the target report is finally reached (yes response to the test in step 108), the finite element calculation optimization loop is stopped and in a final step 112 the final geometry of the specimen with its angle of inclination final order is then issued. Figures 2A and 2B show two examples of fatigue test pieces obtained with the method described above. In the first example, the final angle obtained is 41.25 ° corresponding to a biaxiality ratio of 0.5 while in the second example the final angle obtained is 37.5 ° corresponding to a biaxiality ratio of 0.8. Thus, with the method according to the invention, it is possible, in a simple way, to obtain any biaxiality ratio different from the unit. In practice, it is possible to obtain a test piece having a final angle of inclination of its arms greater than 30 ° and less than or equal to 45 °. Once made in the material to be tested, the test piece according to the invention can be biased by alternating traction in the direction of its length so as to create a bi-axial fatigue stress on its middle part, which at the end of a number of cycles to be determined will cause cracks and a breakage of the material necessary for knowledge of its fatigue behavior.
Claims (6)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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FR0952517A FR2944600B1 (en) | 2009-04-17 | 2009-04-17 | TRACTION-TRACTION BIAXIAL FACIAL TEST. |
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FR0952517A FR2944600B1 (en) | 2009-04-17 | 2009-04-17 | TRACTION-TRACTION BIAXIAL FACIAL TEST. |
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FR2944600A1 true FR2944600A1 (en) | 2010-10-22 |
FR2944600B1 FR2944600B1 (en) | 2011-06-03 |
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FR0952517A Active FR2944600B1 (en) | 2009-04-17 | 2009-04-17 | TRACTION-TRACTION BIAXIAL FACIAL TEST. |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR3070491A1 (en) * | 2017-08-24 | 2019-03-01 | Safran Aircraft Engines | CROSS-TEST TEST FOR BI-AXIAL MECHANICAL SOLICITATION TEST |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1239577A (en) * | 1968-06-15 | 1971-07-21 | ||
FR2823849A1 (en) * | 2001-04-23 | 2002-10-25 | Lorraine Inst Nat Polytech | Real-time control of tensile testing for ductile material undergoing plastic deformation, uses markers on material, which are observed using video cameras and non-linear interpolation is used with marker displacements to determine strain |
FR2914420A1 (en) * | 2007-03-27 | 2008-10-03 | Rech S De L Ecole Nationale Su | Fatigue test specimen for e.g. metallic material in e.g. laboratory, has plate machined in order to have median part in form of X or St Andrew cross with branches, where central part of cross includes bowls arranged on each of its sides |
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2009
- 2009-04-17 FR FR0952517A patent/FR2944600B1/en active Active
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1239577A (en) * | 1968-06-15 | 1971-07-21 | ||
FR2823849A1 (en) * | 2001-04-23 | 2002-10-25 | Lorraine Inst Nat Polytech | Real-time control of tensile testing for ductile material undergoing plastic deformation, uses markers on material, which are observed using video cameras and non-linear interpolation is used with marker displacements to determine strain |
FR2914420A1 (en) * | 2007-03-27 | 2008-10-03 | Rech S De L Ecole Nationale Su | Fatigue test specimen for e.g. metallic material in e.g. laboratory, has plate machined in order to have median part in form of X or St Andrew cross with branches, where central part of cross includes bowls arranged on each of its sides |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR3070491A1 (en) * | 2017-08-24 | 2019-03-01 | Safran Aircraft Engines | CROSS-TEST TEST FOR BI-AXIAL MECHANICAL SOLICITATION TEST |
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FR2944600B1 (en) | 2011-06-03 |
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