A projectile-type ultrasonic impact strengthening device for a circular test rod and a method of using the same

Abstract

The present invention belongs to the part surface treatment technology, and relates to a projectile-type ultrasonic impact strengthening device for a circular test rod and a method for using the device. The device comprises a bottom plate (1), a horn (2), an ultrasonic vibration source (3), a projectile cavity (4), a circular test rod with one tooth (5), a circular test rod with two teeth (6), a test rod rotating mechanism (7) and a projectile (8); the present invention first wraps and seals the working section of the circular test rod in the projectile cavity groove, and increases the impact force and number of the projectile on the surface of the circular test rod along the length direction through the shape and size of the projectile cavity, and matches the appropriate projectile size and number, thereby improving the uniformity of the strengthening effect along the length direction. The round rod is rotated in the circumferential direction by the test rod rotating mechanism, thereby increasing the impact force and number of the projectile on the circumferential direction, thereby improving the uniformity of the strengthening effect on the entire surface.

Description

Technical Field

[0001] The invention belongs to the part surface treatment technology and relates to a projectile type ultrasonic impact strengthening device for a round test rod and a use method thereof. Background Art

[0002] As a new type of surface strengthening technology, shot-type ultrasonic impact strengthening has multiple advantages such as high energy, high efficiency and no pollution. Ultrasonic impact strengthening uses an ultrasonic source to amplify the amplitude of the ultrasonic source through a variable amplitude rod, and drives the projectile to perform high-speed, Brownian motion to achieve impact on the surface of metal parts, forming a surface residual compressive stress layer and a microstructure strengthening layer on the surface of the part, thereby improving the fatigue resistance of the part. When developing the mortise and tenon ultrasonic impact strengthening process, in order to characterize the influence of different process parameters on fatigue performance, a circular fatigue test bar is required for simulation research. However, due to the large curvature and variable cross-section of the outer surface of the circular test bar, when the number of projectiles is small, it is difficult to obtain a uniform and consistent strengthening effect on the surface of the test bar along the length and circumferential directions. Traditional shot peening uses a method of high-pressure gas driven projectiles + fixed spray guns + round rod rotation, but the number of projectiles used in this method is huge, the shot peening intensity generated by the high-pressure gas driven projectiles is also limited, and it is difficult to imitate the effect of mortise and tenon ultrasonic impact strengthening. Patent CN113736986A discloses a multi-axis moving ultrasonic impact strengthening precision machining platform. The ultrasonic impact method used in this method is a striker type, and the number of strikers is single, which cannot achieve the simulation strengthening of the mortise and tenon ultrasonic impact strengthening. Patent CN113736969A discloses a dual-purpose ultrasonic shot peening strengthening device for round rods and flat test pieces, and patent CN112680579A discloses a round rod test piece ultrasonic shot peening strengthening device. The shot peening chambers of the above two devices are relatively simple in shape, and the trajectory of the projectile in them is significantly different from the trajectory in the real mortise and tenon, and it is impossible to simulate the strengthening effect of the mortise and tenon tooth parts. Summary of the invention

[0003] The present invention proposes a projectile-type ultrasonic impact strengthening device for a circular test rod and a method for using the device, the purpose of which is to simulate the motion trajectory of a projectile in a mortise and tenon cavity, and use a rotating round rod test rod to simulate the state of the tenon teeth of the mortise and tenon after being hit by a projectile, and to test the fatigue life or limit after surface treatment, evaluate the ultrasonic impact strengthening effect, and provide support for the optimization of the ultrasonic shot peening process for the mortise and tenon of a turbine disc.

[0004] The technical solution of the present invention is:

[0005] A projectile-type ultrasonic impact strengthening device for a circular test rod, comprising a base plate 1, an horn 2, an ultrasonic vibration source 3, a projectile-shaped cavity 4, a one-tooth circular test rod 5, a two-tooth circular test rod 6, a test rod rotating mechanism 7 and a projectile 8; a square through hole is provided in the center of the base plate 1, a tool head at the upper end of the horn 2 is inserted into the through hole, the tool head is square, coaxial with the through hole, and is clearance-matched; the lower end of the horn 2 is connected to the ultrasonic vibration source 3 by a thread; the projectile-shaped cavity 4 is a rectangular parallelepiped structure, consisting of a wall plate 401, a mortise-and-tenon inner cavity 402, a bottom square hole 403, two right side one-tooth circular holes 404, two left side one-tooth circular holes 405, two right side two-tooth circular holes 406, two left side two-tooth circular holes 407 and a fixed base 408; the shape of the bottom square hole 403 is the same as the side length of the through hole in the center of the base plate 1; the right side one-tooth circular hole 404, the left side one-tooth circular hole 405, the right side two-tooth circular hole 406, the left side two-tooth circular hole 407 and a fixed base 408; the shape of the bottom square hole 403 is the same as the side length of the through hole in the center of the base plate 1; 05 is on the same plane of the upper part of the projectile cavity 4, the two-tooth circular hole 406 on the right side and the two-tooth circular hole 407 on the left side are on the same plane of the lower part of the projectile cavity 4, and the upper surface of the bottom plate 1 is connected and fixed to the fixed base 408; two one-tooth circular test rods 5 are distributed in parallel in the one-tooth circular hole 404 on the right side and the one-tooth circular hole 405 on the left side of the upper part of the projectile cavity 4, and two two-tooth circular test rods 6 are distributed in parallel in the two-tooth circular hole 406 on the right side and the two-tooth circular hole 407 on the left side of the lower part of the projectile cavity 4; the one-tooth circular test rod 5 and the two-tooth circular test rod 6 are divided into a middle working section and clamping sections at both ends, the right end clamping section is respectively in clearance fit with the one-tooth circular hole 404 on the right side and the two-tooth circular hole 406 on the right side, and the left end clamping section passes through the one-tooth circular hole 405 on the left side and the two-tooth circular hole 407 on the left side and is connected to the right end of the test rod rotating mechanism 7, and a spherical projectile 8 is placed in the projectile cavity 4. The side length of the tool head is 0.05-0.5 mm smaller than the side length of the through hole.

[0006] The side length of the tool head is 0.05-0.5 mm smaller than the side length of the through hole.

[0007] The size of the tongue-and-groove inner cavity 402 of the projectile-shaped cavity 4 is 1 to 10 times the size of the tongue-and-groove of the turbine disk.

[0008] There are two fixed bases 408 , each having a bolt hole in the middle. The upper surface of the base plate 1 is fixed to the fixed base 408 by bolt connection.

[0009] The one-tooth circular test rod 5 and the two-tooth circular test rod 6 are dog-bone shaped with a thin middle and thick ends, with a total length of not less than [a+2e+(10-20)] mm, and are divided into a middle working section and clamping sections at both ends.

[0010] The projectile 8 has a diameter of Φ0.5-2 mm and is made of cast steel shot or ceramic shot.

[0011] The diameter of the working section of the one-tooth circular test rod 5 and the two-tooth circular test rod 6 is 1-10 mm smaller than the diameter of the clamping section, and the length of the working section is not greater than the side length of the bottom square hole 403 .

[0012] The length of the inner cavity 402 is a=40~50mm, the width is 10~30mm, and the height is b=12~28mm; the side length of the square hole 403 at the bottom is c=20~25mm; the diameters of the one-tooth circular hole 404 on the right side, the one-tooth circular hole 405 on the left side, the two-tooth circular hole 406 on the right side, and the two-tooth circular hole 407 on the left side are d=4~10mm, and the thickness of the wall panel is e=2~4mm; the number of projectiles N=10~100.

[0013] A method for using a projectile-type ultrasonic impact strengthening device for a circular test bar,

[0014] 1) According to the fatigue resistance requirements of the one-tooth circular test rod 5 and the two-tooth circular test rod 6, a projectile with a diameter of n is selected;

[0015] 2) Place the projectile into the projectile cavity 4 through the circular hole on the side;

[0016] 3) Insert the one-tooth circular test rod 5 from the one-tooth circular hole 404 on the right side and pass through the one-tooth circular hole 405 on the right side, insert the two-tooth circular test rod 6 from the two-tooth circular hole 406 on the right side and pass through the two-tooth circular hole 407 on the left side, and insert them into the right end of the test rod rotating mechanism 7;

[0017] 4) Turn on the power of the test rod rotating mechanism 7, and the one-tooth circular test rod 5 rotates along the axis at a speed of v turns / minute;

[0018] 5) Turn on the power of the ultrasonic vibration source 3, and the horn 2 drives the projectile to move, and the projectile performs high-speed Brownian motion in the projectile cavity 4, and hits the surface of the one-tooth circular test rod 5 and the two-tooth circular test rod 6. When the time t=20-120s is reached, turn off the power of the ultrasonic vibration source 3 and the power of the test rod rotating mechanism 7 in turn;

[0019] 6) Take out the one-tooth circular test rod 5 and the two-tooth circular test rod 6, test the high-temperature rotational bending fatigue life or limit, and compare them with the untreated test rods to evaluate the ultrasonic impact strengthening effect.

[0020] The rotation speed v of the one-tooth circular test rod 5 and the two-tooth circular test rod 6 is 1 to 100 revolutions per minute; the time t is 10 to 600 seconds; and the diameter of the projectile t is 0.6 to 2 mm.

[0021] The advantages of the present invention are:

[0022] (1) By designing a projectile cavity that is consistent with the shape of the mortise, the movement of the projectile in the mortise is simulated. At the same time, the size of the projectile cavity is increased, and a circular test rod is placed on the force-bearing surface of the mortise to simulate the effect of the force-bearing surface being hit by the projectile, thereby evaluating the ultrasonic impact strengthening effect and providing a basis for using a circular test rod to evaluate the anti-fatigue effect.

[0023] (2) By increasing the size of the projectile cavity, the side length of the tool head is made roughly the same as the working section length of the circular test rod, simulating the movement of the projectile in the mortise and tenon groove. By matching the appropriate projectile size and quantity, the impact force and frequency of the projectile on the surface of the circular test rod along the length direction are increased, thereby improving the uniformity of the strengthening effect along the length direction.

[0024] (3) The circular test rod rotating mechanism is used to rotate the circular rod in the circumferential direction, thereby increasing the impact force and frequency of the projectile in the circumferential direction and improving the uniformity of the strengthening effect on the entire surface.

[0025] (4) This method consumes only a small amount of shot (10 to 100), which is far less than traditional shot peening, resulting in lower processing costs, less dust, and less noise.

[0026] (5) Since the ultrasonic frequency is as high as 20-25 kHz and the resonance frequency of the horn is as high as 18-21 kHz, the surface strengthening processing efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the whole device

[0028] Figure 2 Dimensional diagram of the projectile cavity

[0029] Figure 3 Side view of the projectile cavity DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings:

[0031] like Figure 1 - Figure 3As shown, a projectile-type ultrasonic impact strengthening device for a circular test rod comprises a base plate 1, a horn 2, an ultrasonic vibration source 3, a projectile cavity 4, a circular test rod with one tooth 5, a circular test rod with two teeth 6, a test rod rotating mechanism 7 and a projectile 8; there is a square through hole in the center of the base plate 1, and a tool head at the upper end of the horn 2 is inserted into the through hole. The tool head is square and coaxial with the through hole, and is clearance-fitted; the lower end of the horn 2 is connected to the ultrasonic vibration source 3 by a thread; the projectile cavity 4 is long The square structure is composed of a wall plate 401, a tongue-and-groove inner cavity 402, a bottom square hole 403, two right side one-tooth circular holes 404, two left side one-tooth circular holes 405, two right side two-tooth circular holes 406, two left side two-tooth circular holes 407 and a fixed base 408; the shape of the bottom square hole 403 is the same as the side length of the through hole in the center of the bottom plate 1; the right side one-tooth circular hole 404 and the left side one-tooth circular hole 405 are on the same plane of the upper part of the projectile cavity 4, and the right side The two-tooth circular hole 406 and the two-tooth circular hole 407 on the left side are on the same plane at the bottom of the projectile cavity 4, and the upper surface of the bottom plate 1 is connected and fixed to the fixed base 408; two one-tooth circular test rods 5 are parallelly distributed in the one-tooth circular hole 404 on the right side and the one-tooth circular hole 405 on the left side of the upper part of the projectile cavity 4, and two two-tooth circular test rods 6 are parallelly distributed in the two-tooth circular hole 406 on the right side and the two-tooth circular hole 407 on the left side of the lower part of the projectile cavity 4; the one-tooth circular test rod 5 and the two-tooth circular The test rod 6 is divided into a middle working section and clamping sections at both ends. The right end clamping section is respectively matched with the right side one tooth circular hole 404 and the right side two tooth circular hole 406 in a clearance manner. The left end clamping section passes through the left side one tooth circular hole 405 and the left side two tooth circular hole 407 and is connected to the right end of the test rod rotating mechanism 7. The spherical projectile 8 is placed in the projectile cavity 4. The projectile 8 has a diameter of Φ0.5-2mm and is made of cast steel shot or ceramic shot. The number of projectiles N = 10-100. The side length of the tool head at the upper end of the horn 2 is 0.05-0.5mm smaller than the side length of the through hole.

[0032] There are two fixed bases 408 , each having a bolt hole in the middle. The upper surface of the base plate 1 is fixed to the fixed base 408 by bolt connection.

[0033] The one-tooth circular test rod 5 and the two-tooth circular test rod 6 are dog-bone shaped with a thin middle and thick ends, with a total length of not less than [a+2e+(10-20)] mm, and are divided into a middle working section and clamping sections at both ends.

[0034] The diameter of the working section of the one-tooth circular test rod 5 and the two-tooth circular test rod 6 is 1-10 mm smaller than the diameter of the clamping section, and the length of the working section is not greater than the side length of the bottom square hole 403 .

[0035] The size of the mortise and tenon type inner cavity 402 is 1 to 10 times the size of the mortise and tenon of the turbine disc, with a length of a = 40 to 50 mm, a width of 10 to 30 mm, and a height of b = 12 to 28 mm; the side length of the bottom square hole 403 is c = 20 to 25 mm; the diameters of the one-tooth circular hole 404 on the right side, the one-tooth circular hole 405 on the left side, the two-tooth circular hole 406 on the right side, and the two-tooth circular hole 407 on the left side are d = 4 to 10 mm, and the thickness of the wall panel is e = 2 to 4 mm.

[0036] A method for using a projectile-type ultrasonic impact strengthening device for a round test bar,

[0037] 1) According to the fatigue resistance requirements of the one-tooth circular test rod 5 and the two-tooth circular test rod 6, a projectile with a diameter of n is selected;

[0038] 2) Place the projectile into the projectile cavity 4 through the circular hole on the side;

[0039] 3) Insert the one-tooth circular test rod 5 from the one-tooth circular hole 404 on the right side and pass it out from the one-tooth circular hole 405 on the left side. Insert the two-tooth circular test rod 6 from the two-tooth circular hole 406 on the right side and pass it out from the two-tooth circular hole 407 on the left side. Insert them into the right end of the test rod rotating mechanism 7.

[0040] 4) Turn on the power of the test rod rotating mechanism 7, and the one-tooth circular test rod 5 rotates along the axis at a speed of v turns / minute;

[0041] 5) Turn on the power of the ultrasonic vibration source 3, and the horn 2 drives the projectile to move, and the projectile performs high-speed Brownian motion in the projectile cavity 4, and hits the surface of the one-tooth circular test rod 5 and the two-tooth circular test rod 6. When the time t=20-120s is reached, turn off the power of the ultrasonic vibration source 3 and the power of the test rod rotating mechanism 7 in turn;

[0042] 6) Take out the one-tooth circular test rod 5 and the two-tooth circular test rod 6, test the high-temperature rotational bending fatigue life or limit, and compare them with the untreated test rods to evaluate the ultrasonic impact strengthening effect.

[0043] The working principle of the present invention is:

[0044] Ultrasonic waves have the advantages of high frequency, high energy, and high power density, and are one of the ideal power sources for high-energy surface strengthening. In order to achieve the surface deformation strengthening of the mortise and tenon, the use of projectile-type ultrasonic impact strengthening can overcome the problem of structural interference and is an effective way to strengthen the surface of the mortise and tenon. However, in the process of process screening, in order to assess different process parameters, the present invention uses an ultrasonic source to excite the motion of the hard projectile in the cavity, so that the projectile moves at high speed and irregularly. First, the working section of the circular test rod is wrapped and enclosed in the projectile cavity groove. By reasonably designing the shape and size of the projectile cavity, and matching the appropriate projectile size and quantity, the impact force and number of the projectile on the surface of the circular test rod along the length direction are increased, and the uniformity of the strengthening effect along the length direction is improved. The round rod is rotated circumferentially by the test rod rotating mechanism, the impact force and number of the projectile in the circumferential direction are increased, and the uniformity of the strengthening effect of the entire surface is improved. Therefore, it is ensured that the strengthening effect of the circular test rod surface is uniform. And the fatigue life or limit after surface treatment is tested, the ultrasonic impact strengthening effect is evaluated, and support is provided for the optimization of the ultrasonic shot peening process of the turbine disc mortise and tenon.

[0045] Embodiment 1:

[0046] The side length of the tool head = 19.5mm, which is 0.05mm smaller than the side length of the through hole (20mm). The length of the inner cavity 402 is a = 50mm, the width is w = 30mm, and the height is b = 20mm; the shape of the square hole 403 at the bottom is a square, with a side length of c = 20mm, which is the same as the side length of the through hole in the center of the bottom 1. The diameters of the one-tooth circular hole 404 on the right side, the one-tooth circular hole 405 on the left side, the two-tooth circular hole 406 on the right side, and the two-tooth circular hole 407 on the left side are all d = 6mm, and are symmetrically distributed on the two sides of the projectile cavity 4. The center of the one-tooth circular hole 404 on the right side and the one-tooth circular hole 405 on the left side are both g = 15mm from the bottom surface of the projectile cavity 4, and the center of the two-tooth circular hole 406 on the right side and the two-tooth circular hole 407 on the left side are both f = 9mm; the one-tooth circular test rod 5 and the two-tooth circular test rod 6 are divided into a middle working section and clamping sections at both ends, with a total length of 74mm, of which the diameter of the working section is 5.75mm, the diameter of the clamping section is 3.75mm smaller, and the length of the working section is 20mm; the clamping sections are respectively clearance-matched with the one-tooth circular hole 404 on the right side, the one-tooth circular hole 405 on the left side, the two-tooth circular hole 406 on the right side, and the two-tooth circular hole 407 on the left side, and the clearance is 0.1mm. The left ends of the one-tooth circular test rod 5 and the two-tooth circular test rod 6 are connected to the right end of the test rod rotating mechanism 7, and the rotation speed is 100 rpm. Spherical projectiles 8 are placed in the projectile cavity 4, the number is 100, the diameter is 2mm, and the material is ceramic shot. The size of the projectile cavity 4 is 1 times the size of the mortise and tenon of the real turbine disc.

[0047] (1) According to the fatigue resistance requirements of the one-tooth circular test rod 5 and the two-tooth circular test rod 6, a projectile with a diameter of 2 mm is selected.

[0048] (2) Place the projectile into the projectile cavity 4 through the circular hole on the side.

[0049] (3) Insert the one-tooth circular test rod 5 from the one-tooth circular hole 404 on the right side and pass it out from the one-tooth circular hole 405 on the left side. Insert the two-tooth circular test rod 6 from the two-tooth circular hole 406 on the right side and pass it out from the two-tooth circular hole 407 on the left side. Insert both into the right end of the test rod rotating mechanism 7.

[0050] (4) Turn on the power of the test rod rotating mechanism 7, and the circular test rod 5 rotates along the axis at a speed of v turns / minute.

[0051] (5) Turn on the power of the ultrasonic vibration source 3, and the amplitude transformer 2 drives the projectile to move, and the projectile performs high-speed Brownian motion in the projectile cavity 4, and hits the surface of the one-tooth circular test rod 5 and the two-tooth circular test rod 6. When the time t=20s is reached, turn off the power of the ultrasonic vibration source 3 and the power of the test rod rotating mechanism 7 in turn.

[0052] (6) The one-tooth circular test bar 5 and the two-tooth circular test bar 6 were extracted to test the high-temperature rotational bending fatigue life or limit at 600°C, and compared with the untreated test bars to evaluate the ultrasonic impact strengthening effect.

[0053] Example 2

[0054] Spherical shots 8 are placed in the shot cavity 4. The number of the shots is 10. The diameter of the shots is 1 mm and the shot is made of cast steel shot.

[0055] (1) According to the fatigue resistance requirements of the circular test rod, a projectile with a diameter of n = 1 mm is selected.

[0056] (2) Place the projectile into the projectile cavity 4 through the circular hole on the side.

[0057] (3) Insert the one-tooth circular test rod 5 from the one-tooth circular hole 404 on the right side and pass it out from the one-tooth circular hole 405 on the left side. Insert the two-tooth circular test rod 6 from the two-tooth circular hole 406 on the right side and pass it out from the two-tooth circular hole 407 on the left side. Insert both into the right end of the test rod rotating mechanism 7.

[0058] (4) Turn on the power of the test rod rotating mechanism 7, and the circular test rod rotates along the axis at a speed of 1 revolution per minute.

[0059] (5) Turn on the power of the ultrasonic vibration source 3, and the amplitude transformer 2 drives the projectile to move, and the projectile performs high-speed Brownian motion in the projectile cavity 4, and hits the surface of the one-tooth circular test rod 5 and the two-tooth circular test rod 6. When the time t=600s is reached, turn off the power of the ultrasonic vibration source 3 and the power of the test rod rotating mechanism 7 in turn.

Claims

1. A projectile-type ultrasonic impact strengthening device for a circular test bar, characterized in that: The invention comprises a bottom plate (1), a horn (2), an ultrasonic vibration source (3), a projectile-shaped cavity (4), a one-tooth circular test rod (5), a two-tooth circular test rod (6), a test rod rotating mechanism (7) and a projectile (8); a square through hole is provided in the center of the bottom plate (1); a tool head at the upper end of the horn (2) is inserted into the through hole; the tool head is square and coaxial with the through hole and is clearance-matched; the lower end of the horn (2) is connected to the ultrasonic vibration source (3) by a thread; the projectile-shaped cavity (4) is a rectangular parallelepiped structure, comprising a wall plate (401), a tongue-and-groove inner cavity (402), a bottom square hole (403), two right side one-tooth circular holes (404), and two left side The bottom plate (1) is composed of a one-tooth circular hole (405) on the side, two two-tooth circular holes (406) on the right side, two two-tooth circular holes (407) on the left side, and a fixed base (408); the shape of the bottom square hole (403) is the same as the side length of the through hole in the center of the bottom plate (1); the one-tooth circular hole (404) on the right side and the one-tooth circular hole (405) on the left side are on the same plane at the upper part of the projectile cavity (4), the two-tooth circular holes (406) on the right side and the two-tooth circular holes (407) on the left side are on the same plane at the lower part of the projectile cavity (4), and the upper surface of the bottom plate (1) is connected and fixed to the fixed base (408); two one-tooth circular test rods (5) are distributed in parallel in the projectile cavity (4) In the one-tooth circular hole (404) on the right side and the one-tooth circular hole (405) on the left side, two two-tooth circular test rods (6) are parallelly distributed in the two-tooth circular hole (406) on the right side and the two-tooth circular hole (407) on the left side of the projectile cavity (4); the one-tooth circular test rod (5) and the two-tooth circular test rod (6) are divided into a middle working section and clamping sections at both ends, the right end clamping section is respectively clearance-matched with the one-tooth circular hole (404) on the right side and the two-tooth circular hole (406) on the right side, and the left end clamping section passes through the one-tooth circular hole (405) on the left side and the two-tooth circular hole (407) on the left side and is connected to the right end of the test rod rotating mechanism (7), the projectile cavity (4) a spherical projectile (8) is placed inside; the size of the tenon-groove inner cavity (402) of the projectile cavity (4) is 1 to 10 times the size of the tenon groove of the turbine disc; the length of the inner cavity (402) is a=40 to 50 mm, the width is 10 to 30 mm, and the height is b=12 to 28 mm; the side length of the square hole (403) at the bottom is c=20 to 25 mm; the diameters of the right side one-tooth circular hole (404), the left side one-tooth circular hole (405), the right side two-tooth circular hole (406) and the left side two-tooth circular hole (407) are d=4 to 10 mm, and the thickness of the wall plate is e=2 to 4 mm; the number of projectiles N=10 to 100.

2. The projectile-type ultrasonic impact strengthening device for a round test bar as claimed in claim 1, characterized in that: The side length of the tool head is 0.05-0.5 mm smaller than the side length of the through hole.

3. The projectile-type ultrasonic impact strengthening device for a round test bar as claimed in claim 1, characterized in that: There are two fixed bases (408) with bolt holes in the middle. The upper surface of the bottom plate (1) is fixed to the fixed base (408) by bolt connection.

4. The projectile-type ultrasonic impact strengthening device for a round test bar according to claim 1, characterized in that: The one-tooth circular test rod (5) and the two-tooth circular test rod (6) are dog-bone shaped, thin in the middle and thick at both ends, with a total length of not less than [a+2e+(10-20)] mm, and are divided into a working section in the middle and clamping sections at both ends.

5. The projectile-type ultrasonic impact strengthening device for a round test bar as claimed in claim 1, characterized in that: The projectile (8) has a diameter of Φ0.5-2 mm and is made of cast steel shot or ceramic shot.

6. The projectile-type ultrasonic impact strengthening device for a round test bar as claimed in claim 1, characterized in that: The diameter of the working section of the one-tooth circular test rod (5) and the two-tooth circular test rod (6) is 1 to 10 mm smaller than the diameter of the clamping section, and the length of the working section is not greater than the side length of the bottom square hole (403).

7. A method for using a round test bar projectile ultrasonic impact strengthening device according to any one of claims 1 to 6, characterized in that: 1) According to the fatigue resistance requirements of the one-tooth circular test bar (5) and the two-tooth circular test bar (6), a projectile with a diameter of n is selected; 2) Place the projectile into the projectile cavity (4) through the circular hole on the side; 3) inserting a one-tooth circular test rod (5) from the one-tooth circular hole (404) on the right side and passing it out from the one-tooth circular hole (405) on the left side, inserting a two-tooth circular test rod (6) from the two-tooth circular hole (406) on the right side and passing it out from the two-tooth circular hole (407) on the left side, and inserting them into the right end of the test rod rotating mechanism (7); 4) Turn on the power of the test rod rotating mechanism (7), and the one-tooth circular test rod (5) rotates along the axis at a speed of v turns / minute; 5) Turn on the power of the ultrasonic vibration source (3), and the horn (2) drives the projectile to move, so that the projectile performs high-speed Brownian motion in the projectile cavity (4) and strikes the surfaces of the one-tooth circular test rod (5) and the two-tooth circular test rod (6). When the time t=20~120s is reached, turn off the power of the ultrasonic vibration source (3) and the power of the test rod rotating mechanism (7) in turn; 6) A one-tooth circular test bar (5) and a two-tooth circular test bar (6) are extracted to test the high-temperature rotational bending fatigue life or limit, and compared with the untreated test bars to evaluate the ultrasonic impact strengthening effect.

8. The method for using the projectile-type ultrasonic impact strengthening device for a round test bar according to claim 7, characterized in that: The rotation speed v of the one-tooth circular test rod (5) and the two-tooth circular test rod (6) is 1 to 100 revolutions per minute; the time t is 10 to 600 seconds; and the diameter of the projectile t is 0.6 to 2 mm.

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