Adjustable longitudinal-torsional combined vibration ultrasonic fatigue test horn and test method

Abstract

An adjustable ultrasonic fatigue test horn for longitudinal-torsional combined vibration and a test method thereof are disclosed. The horn's structural features include: a circular concave surface is provided in the middle of the rectangular side plane of the upper circumference of the horn, which is bolted to a rail pressure plate; a central locking bolt passes through the central through-hole of a torsion adjustment body and the rail pressure plate and is threadedly connected to the central screw hole of the circular concave surface; angle fixing members with L-shaped steps, smaller on the outside and larger on the inside, are provided on the inner surfaces of both sides of the torsion adjustment body; the angle fixing members cooperate with the steps on the circumference of the rail pressure plate; and the angle locking bolts pass from the inside to the outside through the angle fixing members and the torsion adjustment body before being connected to the angle locking nuts. Using this horn for ultrasonic fatigue testing, the torsional vibration amplitude can be freely adjusted to obtain the harmonic response and fatigue life of the specimen under different longitudinal-torsional combined vibration conditions. This provides a more accurate and reliable test basis for the fatigue resistance design, fatigue mechanism research, and life prediction of high-speed and aged mechanical components under longitudinal-torsional combined vibration conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue testing, in particular to the technical field of ultrasonic fatigue testing. Background Art

[0002] Fatigue failure occurs when a material, under cyclical, repetitive mechanical stress and strain, forms stress concentration points at one or more locations (such as sharp ends, notches, or inclusions), gradually causing localized, permanent cumulative damage, which can lead to cracks or sudden, complete fracture, causing material failure. Statistics show that 90% of engineering component failures are caused by fatigue failure, and mechanical component failures can lead to serious accidents, such as airplane crashes and traffic accidents. To prevent these incidents, fatigue testing of materials is essential during mechanical design and manufacturing.

[0003] The number of cyclic loads that conventional mechanical components bear during their service life is less than 10 7 Therefore, when the number of cyclic loading of the specimen exceeds 10 7 If the specimen is not damaged, it can be considered that the specimen has infinite fatigue life. Therefore, fatigue testing can be completed using a conventional hydraulic fatigue testing machine.

[0004] However, as modern machinery develops towards high speed and aging, many mechanical and engineering components, such as vehicle internal combustion engines, aviation turbine blades and generator components, can withstand repeated loads up to 10 times. 9 ~10 12 A turbine generator running at 3000r / min will experience 10 10 A 20Hz conventional oil pressure fatigue testing machine is used to perform fatigue tests on the specimens. If the stress cycle loading reaches 10 9 It takes up to 1.6 years to complete a stress cycle, which makes it difficult for conventional hydraulic fatigue testing machines to complete fatigue tests on high-speed, aging machinery and engineering components.

[0005] Ultrasonic fatigue testing machines that have appeared in recent years use a working (resonance) frequency of 20kHz and can complete 10 9This is a fatigue test that can test a stress cycle; it has been widely used in fatigue tests of high-speed, aging machinery and engineering components. Its components are: a computer is connected to an ultrasonic generator, which is in turn electrically connected to a piezoelectric converter. The piezoelectric converter is mounted on top of a horn, and one end of the test piece is connected to the lower end of the horn. The test method and principle are as follows: first, the test piece, amplitude, and frequency that meet the resonance conditions are designed through calculation; then, the computer controls the ultrasonic generator to generate an ultrasonic alternating (20KHz) electrical signal with the system's resonance frequency; then, the piezoelectric converter converts the ultrasonic electrical signal into an ultrasonic (high-frequency) longitudinal vibration with the system's resonance frequency; finally, the horn amplifies the longitudinal vibration from the piezoelectric converter, and the amplified ultrasonic longitudinal vibration is finally transmitted to the test piece, thereby achieving the purpose of the fatigue test.

[0006] However, existing ultrasonic fatigue testing machines utilize simple longitudinal resonant waves to apply longitudinal loads to the specimen material. However, many high-speed, aging mechanical components, such as aircraft engine blades and turbines in turbine generators, are subject not only to longitudinal (axial) vibration loads but also circumferential torsional loads under actual operating conditions. Fatigue testing on these specimens subjected to combined longitudinal-torsional vibration using existing ultrasonic fatigue testing machines does not conform to actual operating conditions, resulting in inaccurate test data and unable to provide an accurate and reliable test basis for the fatigue-resistant design, manufacturing, and maintenance of high-speed, aging mechanical components. Summary of the Invention

[0007] The first invention object of the present invention is to provide an adjustable ultrasonic fatigue test amplitude transformer for longitudinal-torsional composite vibration. The ultrasonic fatigue test is carried out using the amplitude transformer, which can not only test the fatigue life of the specimen under longitudinal high-frequency and low-amplitude loads, but also test the fatigue life of the specimen under longitudinal and torsional composite vibration loads; and the torsional vibration amplitude of the longitudinal-torsional composite vibration can be freely adjusted to conveniently obtain the harmonic response and fatigue life of the specimen under different longitudinal-torsional composite vibrations; thereby providing a more accurate and reliable test basis for the anti-fatigue design, fatigue mechanism research and fatigue life prediction of high-speed and old mechanical components under longitudinal-torsional composite vibration conditions.

[0008] The technical solution adopted by the present invention to achieve its first invention purpose is an adjustable longitudinal-torsional composite vibration ultrasonic fatigue test amplitude rod, including an upper large cylindrical main rod, a lower small cylindrical clamp, the top surface of the large cylindrical main rod is provided with a threaded hole connected to the piezoelectric transducer of the ultrasonic fatigue testing machine, and the lower end surface of the small cylindrical clamp is provided with a threaded hole connected to the sample to be tested. It is characterized in that: the middle part of the large cylindrical main rod is equipped with a long strip of torsion adjustment body with adjustable inclination angle on the side surface in the circumferential direction.

[0009] Furthermore, the specific installation structure of the torsion adjustment body on the side of the large cylindrical main rod is:

[0010] The middle part of the large cylindrical main rod is cut into four identical rectangular side planes in the circumferential direction, the middle part of the rectangular side plane is provided with a circular concave surface, the center of the circular concave surface is provided with a central screw hole, and three symmetrical pressure plate locking screw holes are evenly provided on the outer periphery of the central screw hole;

[0011] A track pressure plate is installed in the circular concave surface of the large cylindrical main rod. The specific installation structure is: the hexagonal countersunk bolt of the pressure plate passes through the side hole of the track pressure plate and is threadedly connected with the locking screw hole of the pressure plate; and the circumferential surface of the track pressure plate is in the shape of a step with a larger outer side and a smaller inner side;

[0012] The outer surface of the track pressure plate is installed with a torsion regulating body, and the specific structure of the installation is: the central locking bolt passes through the central through hole of the torsion regulating body and the central through hole of the track pressure plate and is threadedly connected with the central screw hole of the circular concave surface;

[0013] An angle fixing piece for fixing the angle of the torsion adjusting body is provided on the inner surfaces of both sides of the torsion adjusting body; the shape of the angle fixing piece is an L-shaped step with a small outside and a large inside, and the L-shaped step of the angle fixing piece with a small outside and a large inside cooperates with the step with a large outside and a small inside on the circumference of the rail pressure plate; and the angle locking bolt passes through the angle locking hole of the angle fixing piece and the angle locking hole of the torsion adjusting body from the inside to the outside, and is connected to the angle locking nut;

[0014] Furthermore, the outer surfaces of both sides of the torsion adjusting body of the present invention are provided with grooves, and the angle locking nuts are located in the grooves.

[0015] Furthermore: the circular concave surface of the present invention is marked with a rotation angle, with the horizontal being 0°.

[0016] The second invention object of the present invention is to provide a method for ultrasonic fatigue testing of longitudinal-torsional composite vibration using the above-mentioned adjustable longitudinal-torsional composite vibration ultrasonic fatigue test horn. This method can not only test the fatigue life of the specimen under longitudinal high-frequency low-amplitude loads, but also test the fatigue life of the specimen under longitudinal and torsional composite vibration loads; the torsional amplitude of the longitudinal-torsional composite vibration can be freely adjusted to conveniently obtain the harmonic response and fatigue life of the specimen under different longitudinal-torsional composite vibration conditions; thus, it provides a more accurate and reliable test basis for the fatigue resistance design, fatigue mechanism research, and fatigue life prediction of high-speed and old mechanical components under longitudinal-torsional composite vibration conditions.

[0017] The technical solution adopted by the present invention to achieve its second invention object is a method for conducting an ultrasonic fatigue test under longitudinal-torsional composite vibration using the above-mentioned adjustable longitudinal-torsional composite vibration ultrasonic fatigue test horn, the operation of which is as follows:

[0018] A. Connect and fix the connecting bolts on the piezoelectric transducer of the ultrasonic fatigue testing machine to the threaded hole on the top surface of the large cylindrical main rod of the horn; and screw the test sample into the threaded hole on the lower end surface of the small cylindrical fixture at the bottom of the horn;

[0019] B. Loosen the center locking bolt and angle locking nut, rotate the torsion adjusting body and angle fixing piece along the circumference of the track pressure plate to adjust the tilt angle of the torsion adjusting body to the set angle, and then tighten the center locking bolt and angle locking nut to keep the torsion adjusting body at the set tilt angle;

[0020] C. Turn on the ultrasonic fatigue testing machine, control the ultrasonic generator through a computer to generate an ultrasonic electrical signal of a set frequency and amplitude, and convert it into a vertical longitudinal ultrasonic vibration signal by a piezoelectric converter, driving the horn to perform longitudinal ultrasonic vibration; while the horn is vibrating longitudinally ultrasonically, the long, inclined torsion regulating body is subjected to air resistance, and the air resistance generates a circumferential component of force on the inclined torsion regulating body, causing the horn to vibrate torsionally; the longitudinal vibration and the torsional vibration are superimposed, and the horn amplifies the output longitudinal-torsional composite vibration, causing the test sample to generate longitudinal-torsional composite ultrasonic vibration of the set frequency and amplitude;

[0021] While the test sample is generating longitudinal-torsional composite ultrasonic vibration, the vibration of the test sample is measured and recorded using a high-speed optical displacement meter and an oscilloscope to obtain the harmonic response data of the test sample under longitudinal-torsional composite vibration of the set frequency and amplitude; the test is stopped until the set number of vibrations is reached.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. By loosening and tightening the center locking bolt and the angle locking nut, and adjusting the circumferential position of the angle fixing part on the track pressure plate, the inclination angle of the torsion adjustment body of the horn can be adjusted.

[0024] When the torsion adjuster's tilt angle is zero, air resistance directly impacts the torsion adjuster, generating no circumferential force component. Consequently, the torsion adjuster and horn generate no torsional vibration, and the test piece experiences only a purely longitudinal vibration load. At this point, ultrasonic fatigue testing under standard longitudinal vibration can be performed to determine the fatigue life of the test piece under this load.

[0025] When the torsion control body's tilt angle is non-zero, air resistance acts obliquely on the torsion control body, generating a circumferential force component on the torsion control body. This causes torsional vibrations in the torsion control body and the horn. This generates a combined longitudinal-torsional vibration on the test piece. At this point, ultrasonic fatigue testing under this combined longitudinal-torsional vibration can be performed to determine the fatigue life of the test piece under this combined longitudinal-torsional vibration.

[0026] Second, there's no need to replace the torsion adjuster, let alone the horn. Simply loosen and tighten the center locking bolt and angle locking nut to freely adjust the torsional vibration amplitude (longitudinal-torsional vibration ratio) of the longitudinal-torsional composite vibration. This allows for simple, efficient, convenient, and rapid longitudinal-torsional composite vibration ultrasonic fatigue testing of varying torsional vibration amplitudes on the same torsion adjuster. This also avoids potential errors associated with replacing the torsion adjuster or horn, improving test comparability and reliability.

[0027] In summary, the present invention can not only test the fatigue life of the specimen under high-frequency and low-amplitude longitudinal loads, but also test the fatigue life of the specimen under longitudinal and torsional composite vibration loads; and the torsional vibration amplitude of the longitudinal-torsional composite vibration can be freely adjusted to conveniently obtain the harmonic response and fatigue life of the specimen under different longitudinal-torsional composite vibrations; thereby providing a more accurate and reliable test basis for the anti-fatigue design, fatigue mechanism research and fatigue life prediction of high-speed and old mechanical components under longitudinal-torsional composite vibration conditions.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the main structure of an embodiment of the present invention when the torsion adjustment body and the track pressure plate are not installed.

[0030] Figure 2 This is a schematic diagram of the main structure of an embodiment of the present invention (in the figure, the inclination angle of the torsion adjusting body on the front rectangular side plane is 45 degrees, the inclination angle of the torsion adjusting body on the left rectangular side plane is 0 degrees, and the inclination angle of the torsion adjusting body on the right rectangular side plane is 90 degrees).

[0031] Figure 3 for Figure 2 A magnified view of the part in center A.

[0032] Figure 4 Graphs showing the longitudinal amplitude ratio and torsional vibration amplitude obtained from ultrasonic fatigue tests conducted at different tilt angles of the torsion adjustment body using an embodiment of the present invention. DETAILED DESCRIPTION

[0033] Example

[0034] Figure 1-2 A specific embodiment of the present invention is shown as follows: an adjustable longitudinal-torsional composite vibration ultrasonic fatigue test horn, comprising an upper large cylindrical main rod 1, a lower small cylindrical fixture 4, a top surface of the large cylindrical main rod 1 having a threaded hole connected to the piezoelectric transducer of the ultrasonic fatigue testing machine, and a lower end surface of the small cylindrical fixture 4 having a threaded hole connected to the test sample 5, characterized in that:

[0035] A long strip-shaped torsion regulating body 2 with an adjustable tilt angle is installed on the side surface in the circumferential direction of the middle part of the large cylindrical main rod 1.

[0036] The specific installation structure of the torsion regulating body 2 on the side of the large cylindrical main rod 1 in this example is:

[0037] The middle part of the large cylindrical main rod 1 is cut into four identical rectangular side planes 1a in the circumferential direction. A circular concave surface 1b is provided in the middle of the rectangular side plane 1a. A central screw hole 1c is provided in the center of the circular concave surface 1b. Three symmetrical pressure plate locking screw holes 1d are evenly provided on the outer periphery of the central screw hole 1c.

[0038] Figure 2 、 Figure 3 As shown, a track pressure plate 3 is installed in the circular concave surface 1b of the large cylindrical main rod 1. The specific installation structure is: the hexagonal countersunk bolt 3d of the pressure plate passes through the side hole of the track pressure plate 3 and is threadedly connected to the pressure plate locking screw hole 1d; and the circumferential surface of the track pressure plate 3 is a step with a larger outer side and a smaller inner side;

[0039] The outer surface of the track pressure plate 3 is installed with a torsion regulating body 2, and the specific structure of the installation is: the central locking bolt 2c passes through the central through hole of the torsion regulating body 2 and the central through hole of the track pressure plate 3 and is threadedly connected with the central screw hole 1c of the circular concave surface 1b;

[0040] Figure 2 、 Figure 3 As shown, the inner surfaces of both sides of the torsion adjusting body 2 are provided with angle fixing members 2b for fixing the angle of the torsion adjusting body 2; the shape of the angle fixing member 2b is an L-shaped step with a small outside and a large inside, and the L-shaped step of the angle fixing member 2b with a small outside and a large inside cooperates with the step with a large outside and a small inside on the circumference of the rail pressure plate 3; and the angle locking bolt 2a passes through the angle locking hole of the angle fixing member 2b and the angle locking hole of the torsion adjusting body 2 from the inside to the outside, and is connected with the angle locking nut 2f;

[0041] Figure 3 As shown, grooves 2g are formed on the outer surfaces of both sides of the torsion adjusting body 2 in this example, and the angle locking nuts 2f are located in the grooves 2g.

[0042] The circular concave surface 1b in this example is marked with a rotation angle, with the horizontal being 0°.

[0043] A method for conducting an ultrasonic fatigue test under longitudinal-torsional composite vibration using the adjustable longitudinal-torsional composite vibration ultrasonic fatigue test horn of this example comprises the following operations:

[0044] A. Connect and fix the connecting bolts on the piezoelectric transducer of the ultrasonic fatigue testing machine to the threaded holes on the top surface of the large cylindrical main rod 1 of the horn; and screw the test sample 3 into the threaded holes on the lower end surface of the small cylindrical fixture 4 at the lower part of the horn;

[0045] B. Loosen the center locking bolt 2c and the angle locking nut 2f to adjust the tilt angle of the four torsion adjustment bodies 2 to the set angle, and then tighten the center locking bolt 2c and the angle locking nut 2f to keep the torsion adjustment body 2 at the set tilt angle;

[0046] C. Turn on the ultrasonic fatigue testing machine, control the ultrasonic generator through the computer to generate an ultrasonic electrical signal of a set frequency and amplitude, and convert it into a vertical longitudinal ultrasonic vibration signal by the piezoelectric converter, driving the horn to perform longitudinal ultrasonic vibration; while the horn is vibrating longitudinally ultrasonically, the long, inclined torsion regulating body 2 is subjected to air resistance, and the air resistance generates a circumferential component of force on the inclined torsion regulating body 2, causing the horn to vibrate torsionally; the longitudinal vibration and the torsional vibration are superimposed, and the horn amplifies the output longitudinal-torsional composite vibration, causing the test sample 3 to generate longitudinal-torsional composite ultrasonic vibration of the set frequency and amplitude;

[0047] While the test sample 3 is generating longitudinal-torsional composite ultrasonic vibration, the vibration of the test sample 3 is measured and recorded using a high-speed optical displacement meter and an oscilloscope to obtain the harmonic response data of the test sample 3 under the longitudinal-torsional composite vibration of the set frequency and amplitude; the test is stopped until the set number of vibrations is reached.

[0048] Figure 2 In the figure, the inclination angles of the torsion adjusting body 2 on each rectangular side plane are different in order to more clearly show the structure and connection relationship of the torsion adjusting body 2, the rail pressure plate 3 and the angle fixing member 2b; in fact, in the same test, the inclination angles of the torsion adjusting body 2 are usually the same.

[0049] Obviously, the inside and outside in this application are based on the axis of the horn, that is, the area close to the axis of the horn is the inside, and the area far from the axis of the horn is the outside.

[0050] The horn of this example was subjected to ultrasonic fatigue tests under a series of longitudinal-torsion composite vibrations with the torsion regulating body 2 tilted at angles of 10° to 80°. Figure 4 Amplitude diagram of the longitudinal amplitude ratio and torsional vibration amplitude of the torsional adjustment body at different tilt angles. Figure 4It shows that the longitudinal amplitude ratio at different inclination angles in the series of tests is approximately 1 (the longitudinal amplitude ratio is the ratio of the longitudinal amplitude at this inclination angle to the average longitudinal amplitude of the series of tests at different inclination angles); while the torsional vibration amplitude in the series of tests ranges from 0.01° to 0.19°: when the inclination angle of the torsional adjustment body is between 10° and 30°, the torsional vibration amplitude is low, about 0.01°; at a inclination angle of 40°, the torsional vibration amplitude climbs to 0.05°; at a inclination angle of 50° to 60°, the torsional vibration amplitude is the highest, about 0.19°; at a inclination angle of 70°, it drops to 0.15°, and finally to 0.05°.

Claims

1. An adjustable longitudinal-torsional composite vibration ultrasonic fatigue test horn, comprising an upper large cylindrical main rod (1) and a lower small cylindrical fixture (4), wherein the top surface of the large cylindrical main rod (1) is provided with a threaded hole for connecting to a piezoelectric transducer of an ultrasonic fatigue testing machine, and the lower end surface of the small cylindrical fixture (4) is provided with a threaded hole for connecting to a sample to be tested (5), characterized in that: A long strip-shaped torsion regulating body (2) with an adjustable tilt angle is installed on the side surface in the circumferential direction of the middle portion of the large cylindrical main rod (1); The specific installation structure of the torsion regulating body (2) on the side of the large cylindrical main rod (1) is: The middle portion of the large cylindrical main rod (1) is cut into four identical rectangular side planes (1a) in the circumferential direction, a circular concave surface (1b) is provided in the middle portion of the rectangular side plane (1a), a central screw hole (1c) is provided in the center of the circular concave surface (1b), and three symmetrical pressure plate locking screw holes (1d) are evenly provided on the outer periphery of the central screw hole (1c); A track pressure plate (3) is installed in the circular concave surface (1b) of the large cylindrical main rod (1), and the specific installation structure is: the hexagonal countersunk head bolt (3d) of the pressure plate passes through the side hole of the track pressure plate (3) and is threadedly connected to the pressure plate locking screw hole (1d); and the circumferential surface shape of the track pressure plate (3) is a step with a larger outer side and a smaller inner side; The outer surface of the track pressure plate (3) is mounted with a torsion regulating body (2), and the specific mounting structure thereof is as follows: a central locking bolt (2c) passes through the central through hole of the torsion regulating body (2) and the central through hole of the track pressure plate (3) and is threadedly connected with the central screw hole (1c) of the circular concave surface (1b); Angle fixing members (2b) for fixing the angle of the torsion adjusting body (2) are provided on the inner surfaces of both sides of the torsion adjusting body (2); the shape of the angle fixing member (2b) is an L-shaped step with a small outside and a large inside, and the L-shaped step with a small outside and a large inside of the angle fixing member (2b) cooperates with the step with a large outside and a small inside of the circumference of the track pressure plate (3); and the angle locking bolt (2a) passes through the angle locking hole of the angle fixing member (2b) and the angle locking hole of the torsion adjusting body (2) from the inside to the outside, and is then connected with the angle locking nut (2f); Grooves (2g) are formed on the outer surfaces of both sides of the torsion regulating body (2), and the angle locking nuts (2f) are located in the grooves (2g); The circular concave surface (1b) is marked with a rotation angle, with the horizontal angle being 0°.

2. A method for conducting an ultrasonic fatigue test under longitudinal-torsional combined vibration using the adjustable longitudinal-torsional combined vibration ultrasonic fatigue test horn according to claim 1, wherein the method comprises: A. Connect and fix the connecting bolts on the piezoelectric transducer of the ultrasonic fatigue testing machine to the threaded hole on the top surface of the large cylindrical main rod (1) of the amplitude transformer; and screw the test sample (5) to the threaded hole on the lower end surface of the small cylindrical fixture (4) at the lower part of the amplitude transformer; B. Loosen the center locking bolt (2c) and the angle locking nut (2f) to adjust the tilt angle of the four torsion adjustment bodies (2) to the set angle, and then tighten the center locking bolt (2c) and the angle locking nut (2f) to keep the torsion adjustment body (2) at the set tilt angle; C. Turn on the ultrasonic fatigue testing machine, and control the ultrasonic generator through the computer to generate an ultrasonic electrical signal of set frequency and amplitude, which is converted into a vertical longitudinal ultrasonic vibration signal by the piezoelectric converter, driving the amplitude transformer to perform longitudinal ultrasonic vibration; while the amplitude transformer is vibrating longitudinally ultrasonically, the long inclined torsion regulating body (2) is subjected to air resistance, and the air resistance generates a circumferential component force on the inclined torsion regulating body (2), causing the amplitude transformer to vibrate torsionally; the longitudinal vibration and the torsion vibration are superimposed, and the amplitude transformer amplifies and outputs a longitudinal-torsion composite vibration, causing the test sample (5) to generate a longitudinal-torsion composite ultrasonic vibration of set frequency and amplitude; While the test sample (5) generates longitudinal-torsional composite ultrasonic vibration, the vibration of the test sample (5) is tested and recorded by a high-speed optical displacement meter and an oscilloscope to obtain harmonic response data of the test sample (5) under longitudinal-torsional composite vibration of a set frequency and amplitude; the test is stopped until the set number of vibrations is reached.

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