Method of carrying out a vibratory fatigue test of a mechanical part

1. A method of carrying out a vibratory fatigue test of a mechanical part having a fatigue endurance limit, said part comprising a repair extending partly on a first zone of said part,

said method comprising a preliminary test phase including:

selecting a loading mode of the part;

determining a cutting of the part defining a truncated part, the cutting of the part being defined so as to obtain a level of loading in the repaired zone equal to a maximum value of an abatement to be validated;

said method further including:

selecting a measuring device for the fine control of the fatigue test by the measurement of a stress applied to at least one point of the part;

determining a resonance frequency of the truncated part according to the selected loading mode;

implementing a loading according to the selected mode at a given level of the truncated part at the resonance frequency up to rupture of said part.

2. The method of carrying out a vibratory fatigue test according to claim 1 , wherein the cutting of the part is determined by a first calculation of a sensitivity of the truncated part, said sensitivity being substantially equal to the maximum value of the abatement.

3. The method of carrying out a vibratory fatigue test according to claim 2 , wherein the sensitivity value is comprised between 40 and 50% of the endurance limit of the part.

4. The method of carrying out a vibratory fatigue test of a part according to claim 2 , wherein the sensitivity during the test is determined by a set of sensors arranged on the truncated part enabling;

a first reading of at least one stress value in the first zone and;

a second reading of at least one stress value in a second zone of the part,

the ratio between the first reading and the second reading being compared to a ratio calculated at the same points of the truncated part by the finite element method.

5. The method of carrying out a vibratory fatigue test according to claim 1 , wherein

the part is a turbojet engine blade;

the first zone is the leading edge of the blade;

the repair comprises a repair part welded onto the first zone.

6. The method of carrying out a vibratory fatigue test according to claim 1 , wherein determining the cutting of the part comprises determining a cutting height and a cutting shape.

7. The method of carrying out a vibratory fatigue test of a part according to claim 6 , wherein the shape of the cutting is transversal in a plane perpendicular to the axis of the repair part,

8. The method of carrying out a vibratory fatigue test of a part according to claim 6 , wherein the loading mode is a bending mode applied to the part.

9. The method of carrying out a vibratory fatigue test of a part according to claim 1 , wherein the measurement device includes:

a first sensor in the first zone of the truncated part;

a second sensor in a second zone of the truncated part in which the fatigue stress value is substantially close to the maximum value.

a third sensor enabling the fine control of the test, said third sensor being arranged in a third zone where a gradient of the stresses is minimal during the loading of the part.

10. A method of carrying out a vibratory fatigue test of a mechanical part having a fatigue endurance limit, said part comprising a repair extending partly on a first zone of said part, said method comprising:

selecting a loading mode of the part;

determining a cutting of the part defining a truncated part, the cutting of the part being defined so as to obtain a level of loading in the repaired zone equal to a maximum value of an abatement to be validated;

determining a resonance frequency of the truncated part according to the selected loading mode;

loading the part according to the selected mode at a given level of the truncated part at the resonance frequency up to rupture of said part, and

measuring a stress applied to at least one point of the part.