Ultrasonic horn converting longitudinal vibration into torsional vibration, apparatus and test method

Abstract

This invention discloses an ultrasonic amplitude transformer, device, and testing method for converting longitudinal vibration into torsional vibration, relating to the field of high-cycle and ultra-high-cycle fatigue performance and durability testing of materials. The ultrasonic amplitude transformer of this invention includes a first ultrasonic amplitude transformer and a second ultrasonic amplitude transformer made of solid materials of different densities. One end of the first ultrasonic amplitude transformer and one end of the second ultrasonic amplitude transformer are connected by interlocking, and the connection has at least two pairs of interlocking surfaces. Each pair of interlocking surfaces includes at least one interlocking inclined surface. The axial torsional vibration of the ultrasonic amplitude transformer is excited by utilizing the physical property that longitudinal vibration waves are reflected as transverse waves at the interlocking inclined surfaces of materials of different densities. No additional ultrasonic torsional transducer is required. The conversion of longitudinal vibration into torsional vibration can be achieved with a simple structural design, which can reduce the size of the entire torsional fatigue testing equipment and reduce costs.

Description

Technical Field

[0001] This invention relates to the field of high-cycle and ultra-high-cycle fatigue performance and durability testing of materials. Specifically, it relates to an ultrasonic amplitude transformer, equipment, and testing method for converting longitudinal vibration into torsional vibration. Background Technology

[0002] Fatigue is the damage and failure of materials and mechanical structures under cyclic loading. This type of fatigue failure is sudden and catastrophic, often leading to serious accidents and significant economic losses. To avoid such accidents, fatigue testing of materials is necessary before the design and manufacture of mechanical structures.

[0003] In traditional material fatigue testing, 10 7 The number of cycles is considered the safe lifespan, and the corresponding stress level is called the fatigue limit. This view holds that the material has a fatigue limit of 10 cycles. 7 It will not fail after the specified number of cycles. If a traditional 100Hz fatigue testing machine is used, 10 cycles can be completed in 27.8 hours. 7 Weekly testing. Therefore, traditional fatigue testing machines can meet the material fatigue testing needs from this perspective.

[0004] However, as the requirements for service life and reliability of high-end equipment such as automobiles, trains, and airplanes continue to increase, the service cycles of torsion-bearing components such as wheel axles, power take-off shafts, and drive rods in these devices have exceeded 10. 7 Cycles. Taking the axle of a high-speed train as an example, the axle material has a cycle count of 10 during its service life. 9 Torsional fatigue of this magnitude falls under the category of ultra-high cycle fatigue. Ultra-high cycle fatigue research considers materials to experience torsion fatigue at 10 cycles. 7 Failure can still occur after 10 cycles, breaking the traditional fatigue limit of 10. 7 The concept of cycle count as safe lifespan is important. However, research on ultra-high cycle fatigue of materials subjected to torsion has been limited by the testing efficiency of traditional torsional fatigue testing machines. For example, when the operating frequency of the torsional fatigue testing machine is 100Hz, to complete 10 cycles on a test specimen... 9 The fatigue test requires continuous operation for 116 days.

[0005] The ultrasonic fatigue testing machine operates at frequencies up to 20kHz, completing the aforementioned test in just 14 hours. Furthermore, ultrasonic fatigue testing utilizes the resonance principle, a typical low-energy-consumption operating mode. Therefore, the total energy consumption of the ultrasonic fatigue testing machine throughout the entire testing cycle is minimal. This high efficiency and low energy consumption advantage has gradually made it the mainstream equipment for conducting ultra-high cycle fatigue tests. The ultrasonic fatigue testing machine mainly consists of an ultrasonic signal generator, an ultrasonic transducer, an ultrasonic connector, and an ultrasonic amplitude transformer. The ultrasonic signal generator produces an electrical signal with a set amplitude and fixed frequency. This signal is then converted into mechanical vibration of the same frequency by the ultrasonic transducer. This mechanical vibration is then amplified in two stages by the ultrasonic connector and ultrasonic amplitude transformer, driving the test sample to vibrate. Ultimately, cyclic high stress is generated inside the test sample.

[0006] There are two main types of ultrasonic fatigue testing machines used for torsional fatigue testing: direct and indirect. Direct torsional ultrasonic fatigue testing machines use a torsional transducer to directly output torsional excitation. Indirect torsional ultrasonic fatigue testing machines use an ultrasonic torsional transducer to convert the longitudinal vibration output by the ultrasonic transducer into torsional vibration, which is then applied to the torsional fatigue specimen (Application of ultrasonic fatigue technology in very-high-cycle fatigue testing of aviation gas turbine engine blade materials: A review, SCIENCE CHINA-Technological Sciences, 2024, p1332-1335, https: / / doi.org / 10.1007 / s11431-023-2556-1). However, the torsional transducers used in the former are not common in the ultrasonic field and no standard models are available, requiring customization. This not only increases the cost of the testing machine but also reduces its reliability. The torsional ultrasonic transducer in the latter type converts longitudinal vibration to torsional vibration through a mechanical connection, which makes the mechanical connection prone to damage due to reciprocating friction.

[0007] In summary, there is an urgent need to propose a new ultrasonic fatigue loading scheme that converts the longitudinal vibration output of common ultrasonic transducers into torsional vibration, in order to overcome the shortcomings of high cost and low reliability in existing schemes and promote the development of torsional ultrasonic fatigue testing technology. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides an ultrasonic amplitude transformer, equipment and test method for converting longitudinal vibration into torsional vibration. The longitudinal vibration of the ultrasonic amplitude transformer can be converted into torsional vibration by adopting a simple structural design.

[0009] The specific solution of the present invention is as follows: The first aspect of the present invention provides an ultrasonic amplitude transformer that converts longitudinal vibration into torsional vibration, comprising a first ultrasonic amplitude transformer and a second ultrasonic amplitude transformer. The first ultrasonic amplitude transformer and the second ultrasonic amplitude transformer are made of solid materials of different densities. One end of the first ultrasonic amplitude transformer and one end of the second ultrasonic amplitude transformer are connected by interlocking with each other, and the connection has at least two pairs of interlocking surfaces. Each pair of interlocking surfaces includes at least one interlocking inclined surface. The axial torsional vibration of the ultrasonic amplitude transformer is excited by utilizing the physical property that longitudinal vibration waves are reflected as transverse waves at the interlocking inclined surfaces of materials of different densities.

[0010] Furthermore, each pair of mating surfaces includes a mating ramp and a mating elevation, and there is a gap at the vertical interface of the mating elevations of the first ultrasonic amplitude transformer and the second ultrasonic amplitude transformer.

[0011] Furthermore, both the first and second ultrasonic amplitude transformers are rotating bodies and are rotationally symmetrical about their respective central axes.

[0012] Furthermore, the angle between the fitting inclined plane and the radial plane is 30° to 60°.

[0013] Furthermore, the end of the second ultrasonic amplitude transformer away from the first ultrasonic amplitude transformer is the amplitude transformer section, and the cross-sectional shape of the amplitude transformer section is circular arc, conical, catenary, or exponential.

[0014] Furthermore, all the mating ramps of the first and second ultrasonic amplitude transformers have the same direction of rotation.

[0015] A second aspect of the present invention provides a device for converting longitudinal vibration into torsional vibration, comprising an ultrasonic amplitude transformer as described in the first aspect for converting longitudinal vibration into torsional vibration, and further comprising an ultrasonic signal generator, an ultrasonic transducer, and an ultrasonic connector. One end of a first ultrasonic amplitude transformer is connected to the ultrasonic connector, the ultrasonic connector is connected to the ultrasonic transducer, the ultrasonic transducer is connected to the ultrasonic signal generator, and one end of a second ultrasonic amplitude transformer is connected to the sample to be tested.

[0016] Furthermore, it also includes a double-ended stud, wherein the core of the first ultrasonic amplitude transformer has a through hole, and the core of the second ultrasonic amplitude transformer and the ultrasonic connector has a threaded countersunk hole. One end of the double-ended stud passes through the through hole of the first ultrasonic amplitude transformer and is connected to the threaded countersunk hole of the second ultrasonic amplitude transformer, and the other end is connected to the threaded countersunk hole of the ultrasonic connector.

[0017] A third aspect of the present invention provides a test method for ultrasonic fatigue testing using a device as described in the second aspect that converts longitudinal vibration into torsional vibration, wherein the torsional ultrasonic fatigue test is performed using a single longitudinal vibration excitation, and includes the following steps: Step 1: Secure the test sample to the second ultrasonic amplitude transformer; Step 2: Turn on the equipment. The computer controls the ultrasonic signal generator to generate an excitation electrical signal with a fixed frequency and amplitude. This electrical signal is converted into longitudinal mechanical vibration of the same frequency by the ultrasonic transducer. The amplitude of the longitudinal mechanical vibration is amplified by the ultrasonic connector and then used as a single longitudinal vibration excitation to act on the ultrasonic amplitude transformer. The ultrasonic amplitude transformer converts this longitudinal vibration into torsional vibration of the same frequency and drives the test sample to twist, so as to load the test sample with a torsional vibration load of a set frequency and amplitude. Step 3: Record the number of vibration cycles of the test sample until the set number of loading cycles is reached or the test sample breaks, at which point the test stops.

[0018] Furthermore, the test sample is an hourglass-shaped ultrasonic fatigue specimen.

[0019] The beneficial effects of this invention are as follows: The ultrasonic amplitude transformer proposed in this invention utilizes the physical property that longitudinal waves generate reflected transverse waves at the interlocking inclined surfaces of two heterogeneous solids to excite circumferential torsional vibrations in the amplitude transformer. When the excited torsional vibrations are close to or the same as the resonant frequency of the ultrasonic amplitude transformer, torsional resonance is generated. The amplitude of this torsional resonance is amplified by the amplitude transformer section and then applied to the test sample. There is no need to add an additional ultrasonic torsional transducer to convert the longitudinal vibration output by the ultrasonic transducer into torsional vibration. The conversion of longitudinal vibration into torsional vibration can be achieved with a simple structural design, which can reduce the size of the entire torsional fatigue testing equipment, reduce costs, and improve reliability. The ultrasonic amplitude transformer of the present invention also has a gap structure at the end of the interlocking surface of the two heterogeneous media, which avoids the propagation of the excitation longitudinal wave through the vertical contact surface of the interlocking surface to the sample end, and ultimately ensures that a pure torsional fatigue load is applied to the test sample. The device of the present invention, which converts longitudinal vibration into torsional vibration, is suitable for high-cycle and ultra-high-cycle torsional fatigue performance and durability testing of materials, with high testing efficiency and low energy consumption. The ultrasonic fatigue testing method proposed in this invention uses the ultrasonic amplitude transformer of this invention to carry out torsional ultrasonic fatigue testing under single longitudinal vibration excitation. It is simple to operate and highly reliable. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of wave propagation at the interface between two heterogeneous solid media.

[0021] Figure 2 This is a schematic diagram of the ultrasonic amplitude transformer of the present invention.

[0022] Figure 3 This is a cross-sectional view of the ultrasonic amplitude transformer of the present invention.

[0023] Figure 4 This is an exploded view of the ultrasonic amplitude transformer of the present invention from the first perspective.

[0024] Figure 5 This is an exploded view of the ultrasonic amplitude transformer of the present invention from a second perspective.

[0025] Figure 6 This is a schematic diagram of the structure of the device of the present invention that converts longitudinal vibration into torsional vibration.

[0026] Figure 7 This is a schematic diagram showing the dimensions of the ultrasonic amplitude transformer of the present invention.

[0027] Figure 8 This is a schematic diagram of the modal analysis of the ultrasonic amplitude transformer bar in this invention using finite element analysis.

[0028] Figure 9 This is a schematic diagram of the harmonic response analysis of the ultrasonic amplitude transformer finite element analysis of the present invention.

[0029] The reference numerals in the accompanying drawings of this invention are as follows: 101. First ultrasonic amplitude transformer; 102. Second ultrasonic amplitude transformer; 110. Cavity; 2. Ultrasonic connector; 3. Ultrasonic transducer; 4. Test sample. Detailed Implementation

[0030] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0031] Example 1: Please refer to Figures 2 to 5 This embodiment discloses an ultrasonic amplitude transformer that converts longitudinal vibration into torsional vibration, including a first ultrasonic amplitude transformer 101 and a second ultrasonic amplitude transformer 102. The first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 are made of metal materials with different densities.

[0032] One end of the first ultrasonic amplitude transformer 101 and one end of the second ultrasonic amplitude transformer 102 are connected by mutual interlocking, and the connection has at least two pairs of interlocking surfaces. Each pair of interlocking surfaces includes at least one interlocking inclined surface. The axial torsional vibration of the ultrasonic amplitude transformer is excited by utilizing the physical property that longitudinal vibration waves are reflected as transverse waves at the interlocking inclined surfaces of materials with different densities. All interlocking inclined surfaces of the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 have the same direction of rotation. Specifically, in this embodiment, the connection between the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 has four pairs of interlocking surfaces, which are uniformly arranged along the circumferential direction. Each pair of interlocking surfaces includes an interlocking inclined surface and an interlocking vertical surface. The depression or protrusion formed by the interlocking inclined surface and the interlocking vertical surface of the first ultrasonic amplitude transformer 101 is embedded into the protrusion or depression formed by the interlocking inclined surface and the interlocking vertical surface of the second ultrasonic amplitude transformer 102, thereby realizing the interlocking of the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102.

[0033] After the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 are engaged, the engagement inclined surface of the first ultrasonic amplitude transformer 101 is in contact with the engagement inclined surface of the second ultrasonic amplitude transformer 102, and the engagement vertical surface of the first ultrasonic amplitude transformer 101 is in contact with the engagement vertical surface of the second ultrasonic amplitude transformer 102. Please refer to [link / reference]. Figure 1 Based on the theory of sound wave propagation and reflection, when a longitudinal wave is incident from one solid medium to another heterogeneous solid medium at a certain incident angle, reflected longitudinal and transverse waves, as well as refracted longitudinal and transverse waves, will be generated at the interface. When a longitudinal wave is incident perpendicularly from one solid medium to another heterogeneous solid medium, a longitudinal wave will be formed inside the latter. Therefore, in this embodiment, after the longitudinal vibration wave is incident from the first ultrasonic amplitude transformer 101, since the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 are made of materials with different densities, the longitudinal wave will be reflected when passing through the interlocking inclined surface of the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 to form a reflected transverse wave, thereby converting the longitudinal vibration into torsional vibration. Meanwhile, longitudinal vibration waves will be transmitted directly into the interior of the second ultrasonic amplitude transformer 102 through the interlocking surfaces of the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102. To avoid the transmission of such longitudinal waves, a gap is provided at the vertical interface of the interlocking surfaces of the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102. That is, a cavity 110 is formed between the protrusion of the first ultrasonic amplitude transformer 101 and the recess of the second ultrasonic amplitude transformer 102 to block the transmission of longitudinal waves, thereby ensuring that the ultrasonic amplitude transformer achieves pure torque output.

[0034] Both the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 are bodies of revolution and are rotationally symmetrical about their respective central axes. All mating surfaces of the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102 are arranged radially along the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102. The mating inclined surface of the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102 forms a certain angle θ with the radial plane of the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102, preferably 30° to 60°. The interior of the mating inclined surface and the mating surface extends to the axis of the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102, and the exterior of the mating inclined surface and the mating surface extends to the cylindrical surface of the first ultrasonic amplitude transformer 101 or the second ultrasonic amplitude transformer 102.

[0035] The end of the second ultrasonic amplitude transformer 102 furthest from the first ultrasonic amplitude transformer 101 is the amplitude section, and the cross-sectional shape of the amplitude section can be circular, conical, catenary, or exponential. The amplitude section amplifies the ultrasonic vibration and transmits it to the test sample 4.

[0036] In summary, the ultrasonic amplitude transformer of the present invention utilizes the physical property that longitudinal waves generate reflected transverse waves at the interlocking inclined surface of two heterogeneous solids to excite circumferential torsional vibration in the ultrasonic amplitude transformer. When the excited torsional vibration is close to or the same as the resonance frequency of the ultrasonic amplitude transformer, torsional resonance is generated. The amplitude of the torsional resonance is amplified by the amplitude transformer section and then applied to the test sample 4.

[0037] Please see Figure 6 This embodiment also provides a device for converting longitudinal vibration into torsional vibration. The device is used for torsional fatigue testing. The device includes the ultrasonic amplitude transformer described above for converting longitudinal vibration into torsional vibration, and also includes an ultrasonic signal generator, an ultrasonic transducer 3, and an ultrasonic connector 2.

[0038] A double-ended stud connects the first ultrasonic amplitude transformer 101 and the second ultrasonic amplitude transformer 102 to the ultrasonic connector 2. The double-ended stud has the same helix direction as the mating bevel. Specifically, the core of the first ultrasonic amplitude transformer 101 has a through hole, and the cores of the second ultrasonic amplitude transformer 102 and the ultrasonic connector 2 have threaded countersunk holes. One end of the double-ended stud passes downward through the through hole of the first ultrasonic amplitude transformer 101 and connects to the threaded countersunk hole of the second ultrasonic amplitude transformer 102. The other end connects to the threaded countersunk hole of the ultrasonic connector 2, thus fixing the ultrasonic amplitude transformer to the ultrasonic connector 2. The other end of the ultrasonic connector 2 is fixed to the ultrasonic transducer 3, which is connected to the ultrasonic signal generator. One end of the second ultrasonic amplitude transformer 102 is connected to the test specimen 4. The test specimen 4 is preferably an hourglass-shaped ultrasonic fatigue specimen. Using an hourglass-shaped ultrasonic fatigue specimen allows for obtaining the maximum torsional stress at the smallest cross-section in the middle, enabling accurate ultrasonic fatigue test data.

[0039] The device of the present invention, which converts longitudinal vibration into torsional vibration, is suitable for high-cycle and ultra-high-cycle torsional fatigue performance and durability testing of materials, with high testing efficiency and low energy consumption.

[0040] The test method for torsional fatigue testing using the aforementioned equipment that converts longitudinal vibration into torsional vibration includes the following steps: Step 1: Fix the test sample 4 to the second ultrasonic amplitude transformer 102; Step 2: Turn on the equipment and use the computer to control the ultrasonic signal generator to generate an excitation electrical signal with a fixed frequency and amplitude. This electrical signal is converted into longitudinal mechanical vibration of the same frequency by the ultrasonic transducer 3. The amplitude of the longitudinal mechanical vibration is amplified by the ultrasonic connector 2 and then used as a single longitudinal vibration excitation to act on the ultrasonic amplitude transformer. The ultrasonic amplitude transformer converts this longitudinal vibration into torsional vibration of the same frequency and drives the test sample 4 to twist, thereby loading the test sample 4 with a torsional vibration load of a set frequency and amplitude. Step 3: Record the number of vibration cycles of the test sample 4 until the set number of loading cycles is reached or the test sample 4 breaks, at which point the test stops.

[0041] Example 2: This example is a specific application example, which provides more specific parameters of the ultrasonic amplitude transformer and calculates the resonance length of the ultrasonic amplitude transformer through simulation.

[0042] In this embodiment, the first ultrasonic amplitude transformer 101 is made of TC4 titanium alloy with a density of elastic modulus Poisson's ratio .

[0043] The second ultrasonic amplitude transformer 102 is made of 7075-T6 aluminum alloy with a density of elastic modulus Poisson's ratio .

[0044] Please see Figure 7 The diameter of the large end of the ultrasonic amplitude transformer The diameter of the small end Incline angle The length of the first ultrasonic amplitude transformer 101 fitting surface The length of the fitting surface of the second ultrasonic amplitude transformer 102 The distance between the root of the mating surface of the first ultrasonic amplitude transformer 101 and the end face of the first ultrasonic amplitude transformer 101 The distance between the root of the mating surface of the second ultrasonic amplitude transformer 102 and the end face of the second ultrasonic amplitude transformer 102 The length of the large end after fitting. The length of the amplitude section .

[0045] From the formula for calculating the resonant length The length of the small end of the ultrasonic amplitude transformer was calculated. (i.e., the resonant length).

[0046] in, , , , .

[0047] Let be the propagation velocity of torsional vibration in the amplitude range. It is angular frequency. To the torsional vibration frequency, This is the shear modulus.

[0048] The coefficient of sectional contraction in the hyperbolic cosine function. In actual engineering Often greater than ,Right now , .

[0049] In summary, the resonant length was calculated. This data is the result of simulation calculations; the actual data may be affected by factors such as machining accuracy.

[0050] To simplify the frequency determination process, double-ended studs are neglected. Modal analysis is performed using finite element simulation software, and the results are as follows. Figure 8 As shown, the natural frequency corresponding to the torsional vibration mode of the ultrasonic amplitude transformer of the present invention is... The response end is a pure torsional output.

[0051] Then, harmonic response analysis is performed using finite element method software. A single longitudinal vibration excitation (5000N) is applied to the ultrasonic amplitude transformer, such as... Figure 9 As shown, the ultrasonic amplitude transformer acts on the left end, converting this longitudinal vibration excitation into torsional vibration of the same frequency. The response end outputs torsional vibration, proving that the ultrasonic amplitude transformer of the present invention can convert longitudinal vibration into torsional vibration.

[0052] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An ultrasonic amplitude transformer that converts longitudinal vibration into torsional vibration, characterized in that, It includes a first ultrasonic amplitude transformer (101) and a second ultrasonic amplitude transformer (102). The first ultrasonic amplitude transformer (101) and the second ultrasonic amplitude transformer (102) are made of solid materials of different densities. One end of the first ultrasonic amplitude transformer (101) and one end of the second ultrasonic amplitude transformer (102) are connected by interlocking with each other and the connection has at least two pairs of interlocking surfaces. Each pair of interlocking surfaces includes at least one interlocking inclined surface. The axial torsional vibration of the ultrasonic amplitude transformer is excited by utilizing the physical property that longitudinal vibration waves are reflected as transverse waves at the interlocking inclined surfaces of materials of different densities.

2. The ultrasonic amplitude transformer for converting longitudinal vibration into torsional vibration according to claim 1, characterized in that, Each pair of mating surfaces includes a mating ramp and a mating elevation, with a gap at the vertical interface of the mating elevations of the first ultrasonic amplitude transformer (101) and the second ultrasonic amplitude transformer (102).

3. The ultrasonic amplitude transformer for converting longitudinal vibration into torsional vibration according to claim 1, characterized in that, Both the first ultrasonic amplitude transformer (101) and the second ultrasonic amplitude transformer (102) are rotating bodies and are rotationally symmetrical about their respective central axes.

4. The ultrasonic amplitude transformer for converting longitudinal vibration into torsional vibration according to claim 1, characterized in that, The angle between the fitting inclined plane and the radial plane is 30° to 60°.

5. The ultrasonic amplitude transformer for converting longitudinal vibration into torsional vibration according to claim 1, characterized in that, The end of the second ultrasonic amplitude transformer (102) away from the first ultrasonic amplitude transformer (101) is the amplitude section, and the cross-sectional shape of the amplitude section is arc-shaped, conical, catenary-shaped or exponential.

6. The ultrasonic amplitude transformer for converting longitudinal vibration into torsional vibration according to claim 1, characterized in that, All the mating ramps of the first ultrasonic amplitude transformer (101) and the second ultrasonic amplitude transformer (102) have the same direction of rotation.

7. A device for converting longitudinal vibration into torsional vibration, characterized in that, The ultrasonic amplitude transformer, which converts longitudinal vibration into torsional vibration as described in any one of claims 1 to 6, further includes an ultrasonic signal generator, an ultrasonic transducer (3), and an ultrasonic connector (2). One end of the first ultrasonic amplitude transformer (101) is connected to the ultrasonic connector (2), the ultrasonic connector (2) is connected to the ultrasonic transducer (3), the ultrasonic transducer (3) is connected to the ultrasonic signal generator, and one end of the second ultrasonic amplitude transformer (102) is connected to the test sample (4).

8. The device for converting longitudinal vibration into torsional vibration according to claim 7, characterized in that, It also includes a double-ended stud. The core of the first ultrasonic amplitude transformer (101) has a through hole, and the core of the second ultrasonic amplitude transformer (102) and the ultrasonic connector (2) has a threaded countersunk hole. One end of the double-ended stud passes through the through hole of the first ultrasonic amplitude transformer (101) and is connected to the threaded countersunk hole of the second ultrasonic amplitude transformer (102). The other end is connected to the threaded countersunk hole of the ultrasonic connector (2).

9. A test method for ultrasonic fatigue testing using the device as described in claim 7 that converts longitudinal vibration into torsional vibration, characterized in that, Torsional ultrasonic fatigue testing using a single longitudinal vibration excitation includes the following steps: Step 1: Fix the test sample (4) to the second ultrasonic amplitude transformer (102); Step 2: Turn on the equipment and use the computer to control the ultrasonic signal generator to generate an excitation electrical signal with a fixed frequency and amplitude. The electrical signal is converted into longitudinal mechanical vibration of the same frequency by the ultrasonic transducer (3). The amplitude of the longitudinal mechanical vibration is amplified by the ultrasonic connector (2) and then used as a single longitudinal vibration excitation to act on the ultrasonic amplitude transformer. The ultrasonic amplitude transformer converts this longitudinal vibration into torsional vibration of the same frequency and drives the test sample (4) to twist, so as to load the test sample (4) with a torsional vibration load of a set frequency and amplitude. Step 3: Record the vibration cycles of the test sample (4) until the set number of loading cycles is reached or the test sample (4) breaks, at which point the test stops.

10. The test method for ultrasonic fatigue testing of a device that converts longitudinal vibration into torsional vibration according to claim 9, characterized in that, The test sample (4) is an hourglass-shaped ultrasonic fatigue specimen.

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