Equipment For Fatigue Testing At Ultrasonic Frequencies In The Multiaxial Regime-Axial And Torsional Directions

Abstract

The present invention refers to an equipment that allows the performance of fatigue testing at ultrasonic frequencies in a multiaxial loading, more specifically biaxial. The equipment is formed by two components, the horn (1) and the specimen (5), which are coupled with each other. The horn (1) and the specimen (5) possess such geometry that their resonant frequency which, is relevant for the testing, is synchronized with the excitation frequency of the exciter, so that the whole equipment vibrates in free regime. Through its vibration mode, the horn (1) transforms the pure axial cyclic movement which it receives from the exciter into a mixed movement comprised of axial and torsional cyclic and in-phase movements. The specimen (5) possesses, synchronized at the same frequency, its first axial vibration mode and its third torsional vibration mode.

Claims

1. Equipment for multiaxial fatigue testing at ultrasonic frequencies using an axial ultrasonic exciter, characterized in that the said axial ultrasonic exciter is coupled to a horn. (1), containing a plurality of oblique slits (3) in the conical revolution surface, inclined at a certain angle with respect to the axis of the horn (1), being in turn coupled to a cylindrical shaped specimen (5) by means of mechanical joint, wherein the specimen (5) has an upper throat (7), a central throat (8) and a lower throat (9), thus the equipment operates in the resonant mode of the exciter, horn (1) and specimen (5).

2. Equipment for multiaxial fatigue testing, according to claim 1, characterized in that the horn (1) has dimensions dependent on the material from which the horn (1) is formed.

3. Equipment for multiaxial fatigue testing, according to claim 1, characterized, in that the specimen (5) has overall dimensions dependent on the material from which the specimen (5) is formed.

Description

Description of FIGURES

[0024] FIG. 1 shows the horn (1) formed, by a thread connection to the ultrasonic exciter, a contact surface (2) of the horn (1) with the exciter, a plurality of oblique slits (3) and a contact surface (4) of the horn (1) with the specimen (5).

[0025] FIG. 2 shows the specimen (5) formed by a contact surface (6) of the specimen (5) with the horn (1), an upper throat (7), a central throat (8) and a lower throat (9).

[0026] FIG. 3 shows the computational mode of vibration of the assembly formed by the horn (1) and the specimen (5) at the test frequency, where the black color is associated with the largest displacements and the white color is associated with the smallest displacements. It is also possible to identify the oblique slits (3) of the horn (1) and the upper throat (7), the central throat (8) and the lower throat (9) of the specimen (5).

[0027] FIG. 4 shows the torsional computational vibration mode of the specimen (5), where there is a vibration node in the upper throat (7), a vibration node in the central throat (8) and a vibration node in the lower throat (9). For this mode, the axial displacement is zero throughout the specimen (5).

[0028] FIG. 5 shows the axial computational vibration mode of the specimen (5), where there is a vibration node in the central throat (8). It is also possible to identify the upper throat (7) and the lower throat (9). For this mode, the rotational displacement is zero throughout the specimen (5).

[0029] FIG. 6 shows the side view of the assembly of the horn (1) with the specimen (5). It is possible to identify the contact surface (2) of the horn (1) with the ultrasonic exciter, the oblique slits (3), the contact surface (4) of the horn (1) with the specimen (5) and the contact, surface (6) of the specimen (5) with the horn (1), the specimen (5) and the upper throat (7), the central throat (8) and the lower throat (9) of the specimen (5).

[0030] FIG. 7 shows the equipment of the present invention, where the horn (1) and the specimen (5) are observed.

[0031] FIG. 8 shows the two temporal signals acquired by two vibrometers in the rotational measurements of the specimen (5).

[0032] FIG. 9 shows the three temporal signals acquired by the three-channel rosette strain gage installed in the central throat (8).

EXAMPLE

[0033] A prototype of the equipment described herein was constructed and tested, constituted by a horn (1) and a specimen (5). Preliminary results indicate that the specimen (5) has rotational behavior which is confirmed by the signals represented in FIG. 8. A three-channel rosette-type extensometer was installed in the central groove (8), whose temporal results, which confirm the existence of a multiaxial loading, are shown in FIG. 9.