Ultrasonic assisted punch vibration powder two-way compression molding device and method

Abstract

The application discloses an ultrasonic-assisted punch die vibration powder bidirectional pressing forming device and method, which comprises a first punch assembly, a die body, a second punch assembly, a driving device and a density detection device. The first punch assembly comprises a first punch, a first cavity die sleeve, a first ultrasonic generator and a first driving plate. The second punch assembly comprises a second punch, a second cavity die sleeve, a second ultrasonic generator and a second driving plate. The density detection device is used for detecting the green density of the powder in the cavity. The driving force of the driving device acts on the first driving plate and the second driving plate respectively, and drives the first punch and the second punch to move. In the moving process, the first ultrasonic generator and the second ultrasonic generator vibrate and drive the first punch and the second punch to vibrate. The tip angle, vibration frequency, vibration amplitude, moving speed and displacement of the first punch and the second punch are adjusted according to the green density, so that the compaction density and uniformity are improved.

Description

Technical Field

[0001] This invention relates to the field of powder material pressing and molding technology, and in particular to an ultrasonic-assisted punch vibration bidirectional powder pressing and molding device and method. Background Technology

[0002] Powder compression molding technology is a new molding process technology that uses powder as raw material and processes such as filling and compression to prepare metal materials, composite materials and various types of products. It has been widely used in fields such as engineering machinery, automobiles, new energy, aerospace, and medical, and has been a research hotspot in the academic and engineering communities in recent years.

[0003] However, during the powder compression molding process, the internal friction between powder materials and the wall friction between powder and the wall surface hinder the transmission of internal forces in the powder bed, which in turn hinders the rearrangement of particles during the compression process. This leads to particle segregation in different height directions (punch movement direction) and different radial directions (perpendicular to the punch movement direction), resulting in uneven density distribution inside the compact. Ultimately, this leads to problems such as uneven internal stress distribution, easy cracking, and poor mechanical properties in the molded specimen. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of uneven density distribution in existing powder pressing processes, and to provide an ultrasonic-assisted punch vibration bidirectional powder pressing device and method, so as to reduce internal friction and wall friction of particles during pressing, improve particle rearrangement during powder pressing, reduce particle segregation, and ultimately improve the densification and mechanical properties of the specimen.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] An ultrasonic-assisted punch vibration bidirectional powder compression molding device includes a first punch assembly, a mold body, a second punch assembly, a driving device, and a density detection device. The first punch assembly includes a first punch, a first cavity mold sleeve, a first ultrasonic generator, and a first driving plate. The first driving plate and the first punch are respectively installed at the top and bottom of the first cavity mold sleeve. The first ultrasonic generator is installed inside the first cavity mold sleeve and connected to the first punch. The second punch assembly includes a second punch, a second cavity mold sleeve, a second ultrasonic generator, and a second driving plate. The second driving plate and the second punch are respectively installed at the top and bottom of the second cavity mold sleeve. The second ultrasonic generator is installed inside the second cavity mold sleeve. The first punch assembly and the second punch assembly are connected to the mold body. The first punch assembly and the second punch assembly are respectively installed at both ends of the mold body. The mold body, the first punch and the second punch form a cavity. The cavity is used to place powder. The density detection device is used to detect the compact density of the powder in the cavity. The driving force of the driving device acts on the first driving plate and the second driving plate respectively, and drives the first punch and the second punch to move. During the movement of the first punch and the second punch, the first ultrasonic generator and the second ultrasonic generator perform ultrasonic vibration and drive the first punch and the second punch to vibrate. The included angle of the tips of the first punch and the second punch, the vibration frequency, the vibration amplitude, the moving speed and the displacement are adjusted according to the compact density.

[0007] Preferably, a buffer device is used to flexibly connect the first punch and the first cavity mold sleeve, as well as the second punch and the second cavity mold sleeve.

[0008] Preferably, the device also includes a mounting base, which is fixedly mounted on the first punch and the second punch, and the first ultrasonic generator and the second ultrasonic generator are fixedly mounted on the mounting base.

[0009] Preferably, the mounting base is made of plastic or ceramic material.

[0010] Preferably, the first and second ultrasonic generators are equipped with grounding devices.

[0011] Preferably, the mold body is a cylindrical structure, and the first punch assembly and the second punch assembly are respectively installed at both ends of the cylindrical structure.

[0012] Preferably, the density detection device includes a near-infrared high-speed imaging system, which includes a detection device installed inside the side wall of the cylindrical structure.

[0013] Preferably, the tip angle of the first and second punches is adjusted by rolling rollers on both sides, and the tip angle ranges from 90 degrees. 0 <α≤180 0 .

[0014] Preferably, the driving device includes a hydraulic press, and the output shaft of the hydraulic press is connected to the first driving plate and the second driving plate respectively.

[0015] An ultrasonic-assisted punch vibration powder bidirectional pressing molding method, employing the aforementioned ultrasonic-assisted punch vibration powder bidirectional pressing molding device, includes the following steps:

[0016] 1) Move the first punch assembly to the first position above the mold body, and move the second punch assembly to the second position inside the mold body to place the powder into the cavity;

[0017] 2) The drive unit is activated to drive the first punch assembly and the second punch assembly to move relative to each other until the powder compact is pressed to the specified thickness. The first punch assembly and the second punch assembly then come to a stop and hold the pressure. During the movement of the first punch assembly and the second punch assembly, the density detection device is activated to detect the density of the powder compact in the cavity. The first ultrasonic generator and the second ultrasonic generator are activated to perform ultrasonic vibration and drive the first punch and the second punch to vibrate. The included angle between the tips of the first punch and the second punch, the vibration frequency, the vibration amplitude, the moving speed, and the displacement are adjusted according to the compact density, as shown in the following formulas:

[0018]

[0019]

[0020] Where V1 and V2 are the moving speeds of the first punch and the second punch, respectively. Let v1 be the density of the pressed blank, and v2 be the functional relationship between the moving speed of the first punch and the second punch and the density of the pressed blank, respectively.

[0021]

[0022]

[0023] Wherein, S1 and S2 are the displacements of the first punch and the second punch, respectively, and s1 and s2 are the functional relationships between the displacements of the first punch and the second punch and the density of the blank.

[0024]

[0025]

[0026]

[0027]

[0028] Where A1, A2, A0, F1, and F2 represent the vibration amplitude of the first ultrasonic generator, the vibration amplitude of the second ultrasonic generator, the maximum vibration amplitude, the vibration frequency of the first ultrasonic generator, and the vibration frequency of the second ultrasonic generator, respectively; f1 and f2 are the functional relationships between the vibration frequencies of the first and second punches and the compact density, respectively; and t is time.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention uses a first punch and a second punch with a pointed corner to press the powder. This structure can further increase the radial force on the powder, resist the internal friction between particles, and promote the particles to move towards the wall, thereby reducing radial particle segregation.

[0031] (2) The present invention provides ultrasonic vibration to the first and second punches, which can reduce the internal friction of particles and the wall friction between particles and the wall, improve the movement and rearrangement of particles, thereby improving the internal density uniformity of the compact and improving the molding quality and mechanical properties of the specimen.

[0032] (3) In the field of powder material compression molding, the present invention can better achieve more compact and highly uniform molded specimens under relatively mild compression process conditions. Attached Figure Description

[0033] The accompanying drawings are included to provide a further understanding of the embodiments, and these drawings are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description.

[0034] Figure 1 This is a schematic diagram of an ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0035] Figure 2 This is a schematic diagram of the first punch assembly or the second punch assembly of the ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0036] Figure 3 This is a schematic diagram illustrating the loading principle of an ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0037] Figure 4 This is a schematic diagram illustrating the principle of tip angle adjustment for the first and second punches in the ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0038] Figure 5This is a schematic diagram illustrating the principle of adjusting the moving speed and displacement of the first and second punch assemblies in the ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0039] Figure 6 The diagram illustrates the working principle of the first and second ultrasonic generators in the ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to an embodiment of this application.

[0040] Reference numerals: 1. First punch assembly; 2. Mold body; 3. First ultrasonic generator; 4. First punch; 5. Second punch assembly; 6. First drive plate; 7. First cavity mold sleeve; 8. Buffer device; 9. Mounting base; 10. Density detection device. Detailed Implementation

[0041] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] refer to Figure 1 and Figure 2This invention provides an ultrasonic-assisted punch vibration bidirectional powder pressing and molding device, comprising a first punch assembly 1, a mold body 2, a second punch assembly 5, a driving device, and a density detection device 10. The first punch assembly 1 includes a first punch 4, a first cavity mold sleeve 7, a first ultrasonic generator 3, a first driving plate 6, and a mounting base 9. The first driving plate 6 and the first punch 4 are respectively installed at the top and bottom of the first cavity mold sleeve 7. The first cavity mold sleeve 7 is hollow inside. The first ultrasonic generator 3 is installed inside the first cavity mold sleeve 7 and rigidly connected to the first punch 4 via the mounting base 9. The second punch assembly 5 includes a second punch, a second cavity mold sleeve, a second ultrasonic generator, a second driving plate, and a mounting base 9. The second driving plate and the second punch are respectively installed at the top and bottom of the second cavity mold sleeve. The second cavity mold sleeve is hollow inside. The second ultrasonic generator is installed inside the second cavity mold sleeve and rigidly connected to the second punch via the mounting base 9. Specifically, the mounting base 9 is fixedly mounted on the first punch 4 and the second punch, and the first ultrasonic generator 3 and the second ultrasonic generator are fixedly mounted on the mounting base 9. The mounting base 9 is made of insulating plastic or ceramic material. A buffer device 8 flexibly connects the first punch 4 to the first cavity mold sleeve 7 and the second punch to the second cavity mold sleeve. The first punch assembly 1 and the second punch assembly 5 are respectively mounted at both ends of the mold body 2, and the mold body 2, the first punch 4, and the second punch form a cavity for placing powder. A density detection device 10 is used to detect the compact density of the powder in the cavity. The driving force of the driving device acts on the first drive plate 6 and the second drive plate, respectively, and drives the first punch 4 and the second punch to move. Specifically, the driving device includes a hydraulic press, and the output shaft of the hydraulic press is connected to the first drive plate 6 and the second drive plate, respectively. The mold body 2 is mounted and fixed on the machine base through flanges and positioning holes.

[0044] During the movement of the first punch 4 and the second punch, the first ultrasonic generator 3 and the second ultrasonic generator perform ultrasonic vibration, driving the first punch 4 and the second punch to vibrate. The movement process of the first punch assembly 1 and the second punch assembly 5 is as follows: the driving force of the driving device acts directly on the first driving plate 6 and the second driving plate. The first driving plate 6 transmits the force and displacement to the first punch 4 through the first cavity mold sleeve 7 and the buffer pad. The second driving plate transmits the force and displacement to the first punch 4 through the second cavity mold sleeve and the buffer device 8, thereby completing the pressing process. The vibration process is as follows: when the first driving plate 6 starts to move, the first ultrasonic generator 3 is activated. The first ultrasonic generator 3 transmits the vibration signal to the first punch 4 through the mounting base 9, causing the first punch 4 to resonate. When the second driving plate starts to move, the second ultrasonic generator is activated. The second ultrasonic generator transmits the vibration signal to the second punch through the mounting base 9, causing the second punch to resonate. The buffer device 8 specifically adopts a buffer pad, which can transmit force and displacement. When the resonant motion generated by the first ultrasonic generator 3 driving the first punch 4 is transmitted to the buffer pad, it is fully absorbed and cannot be transmitted to the first cavity mold sleeve 7. Similarly, when the resonant motion generated by the second ultrasonic generator driving the second punch is transmitted to the buffer pad, it is fully absorbed and cannot be transmitted to the second cavity mold sleeve.

[0045] Furthermore, the included angle, vibration frequency, vibration amplitude, moving speed, and displacement of the first punch 4 and the second punch are adjusted online according to the distribution of the billet density. The included angle, vibration frequency, moving speed of the first punch assembly 1 and the second punch assembly 5, and pressing displacement of the first punch 4 and the second punch are different. The adjustment of speed and displacement depends on the billet density distribution monitored online by the density detection device 10. The density detection device 10 includes a near-infrared high-speed imaging system, which includes a detection device installed inside the side wall of the cylindrical structure. The included angle of the first punch 4 and the second punch is adjusted by rolling rollers on both sides, with the included angle ranging from 90°. 0 <α≤180 0 The second ultrasonic generator outputs ultrasonic waves only when the second punch begins to move (or when the hydraulic press pressure increases) and the speed is stable.

[0046] In a specific embodiment, the first ultrasonic generator 3 and the second ultrasonic generator are equipped with grounding devices. Specifically, the metal casings of the first ultrasonic generator 3 and the second ultrasonic generator are electrostatically grounded to ensure electrical safety.

[0047] In a specific embodiment, the mold body 2 is a cylindrical structure, with the first punch assembly 1 and the second punch assembly 5 respectively installed at both ends of the cylindrical structure. Powder is loaded into the cavity from one end of the cylindrical structure, while the other end is blocked by the second punch assembly 5. After the powder is loaded, the first punch assembly 1 and the second punch assembly 5 move relative to each other from both ends of the cylindrical structure, pressing the powder into a blank. The powder filling method is not limited. Before filling, the first punch assembly 1 is removed from the mold body 2 or raised to a specified height, while the second punch assembly 5 remains in a specified position within the cavity of the mold body 2. After the powder filling is completed, the first punch assembly 1 is moved horizontally to directly above the powder within the cavity of the mold body 2. Then, the driving device for the first punch assembly 1 and the second punch assembly 5—a hydraulic press—is simultaneously activated, and the hydraulic press pressure is set, causing the first punch assembly 1 and the second punch assembly 5 to move relative to each other to complete the powder pressing. (Reference) Figure 3 During the pressing process, the particles inside the cavity are subjected to vibration. At the same time, the first punch 4 exerts an inclined downward pressure on the particles, and the second punch exerts an inclined upward pressure on the particles. This reduces the friction of the particles while increasing the pressure that promotes the movement of the particles, thereby maximizing the rearrangement of the particles, reducing particle segregation, and improving the uniformity and compactness of the density distribution.

[0048] In a specific embodiment, the present application also proposes an ultrasonic-assisted punch vibration powder bidirectional pressing molding method, which uses the above-mentioned ultrasonic-assisted punch vibration powder bidirectional pressing molding device and includes the following steps:

[0049] 1) Move the first punch assembly 1 to the first position above the mold body 2, and move the second punch assembly 5 to the second position inside the mold body 2 to place the powder in the cavity.

[0050] 2) The drive unit is activated to drive the first punch assembly 1 and the second punch assembly 5 to move relative to each other until the powder compact is pressed to the specified thickness. The first punch assembly 1 and the second punch assembly 5 then come to a stop and hold the pressure. During the movement of the first punch assembly 1 and the second punch assembly 5, the density detection device 10 is activated to detect the density of the powder compact in the cavity. The first ultrasonic generator 3 and the second ultrasonic generator are activated to perform ultrasonic vibration and drive the first punch 4 and the second punch to vibrate. The included angle between the tips of the first punch 4 and the second punch, the vibration frequency, the moving speed, and the displacement are adjusted according to the compact density, as shown in the following formula:

[0051]

[0052]

[0053] Wherein, V1 and V2 are the moving speeds of the first punch 4 and the second punch, respectively. Let v1 and v2 be the density of the pressed blank, and v1 and v2 be the functional relationships between the moving speed of the first punch 4 and the second punch and the density of the pressed blank, respectively.

[0054]

[0055]

[0056] Wherein, S1 and S2 are the displacements of the first punch 4 and the second punch, respectively, and s1 and s2 are the functional relationships between the displacements of the first punch 4 and the second punch and the density of the pressed blank, respectively.

[0057]

[0058]

[0059]

[0060]

[0061] Wherein, A1, A2, A0, F1, and F2 represent the vibration amplitude of the first ultrasonic generator 3, the vibration amplitude of the second ultrasonic generator, the maximum vibration amplitude, the vibration frequency of the first ultrasonic generator 3, and the vibration frequency of the second ultrasonic generator, respectively; f1 and f2 are the functional relationships between the vibration frequencies of the first punch 4 and the second punch and the compact density, respectively; and t is time.

[0062] For details, please refer to Figure 4 During the pressing process, the rollers on both sides of the first punch 4 and the second punch roll, causing the included angle between their tips to be at α. min ~α max Adjustable within range, 90 0 <α≤180 0 And the value can be any value.

[0063] refer to Figure 5 The time interval from 0 to t1 is when the first punch assembly 1 moves from directly above the mold body 2 to the cavity entrance position after the powder filling is completed; the time interval from t1 to t2 is the pressing process; the time interval from t2 to t3 is the holding pressure stage; V1, V2, S1, and S2 represent the movement speed of the first punch assembly 1, the movement speed of the second punch assembly, the displacement of the first punch assembly 1, and the displacement of the second punch assembly, respectively. The value represents the uniformity of the compact density, calculated using a near-infrared imaging system and related data processing system. s0 represents the total pressing stroke, determined after compaction: s0 = s3 - s2 + s1. s3 and s2 correspond to the initial displacement of the first punch assembly 1 during the pressing process and the final displacement during the holding phase, respectively, while s1 corresponds to the final position of the second punch assembly during the holding phase. The movement velocities V1 and V2 of the first and second punch assemblies during the pressing process are related to the uniformity of the compact density. Relatedly, the side with poor uniformity needs to increase the movement speed of the corresponding punch assembly.

[0064] refer to Figure 6 The vibration frequencies f1 and f2 of the first and second ultrasonic generators depend on the uniformity index of the compact density obtained by the near-infrared imaging system. The side with poor uniformity needs to have its corresponding ultrasonic generator vibration frequency increased.

[0065] The drive unit is activated, and under its drive, the first punch assembly 1 and the second punch assembly 5 move relative to each other and compress the powder to complete the pressing. At the start of pressing, the first ultrasonic generator 3 and the second ultrasonic generator are activated, and the first punch 4 and the second punch resonate. The powder inside the cavity is vibrated and moves towards the two sides of the cavity boundary. The near-infrared imaging system is activated to detect the uniformity of the compact density distribution in real time. During the pressing process, the vibration frequency, the first punch 4, the included angle of the tip of the first punch 4, and the pressing speed are adjusted in real time according to the compact density distribution characteristics. On the one hand, the ultrasonic waves excite the first punch 4 and the second punch to resonate, and the resonance waves cause internal disturbances in the powder, reducing the friction between powder particles and between the powder and the wall surface, and enhancing particle rearrangement during the pressing process. On the other hand, the first punch 4 and the second punch adopt a "convex" structure design, which promotes the movement of the powder towards the two sides of the cavity boundary, improves the powder density near the cavity boundary, and improves the compaction density and its uniformity.

[0066] The specific embodiments of this application have been described above, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An ultrasonic-assisted punch vibration bidirectional powder pressing and molding device, characterized in that, The system includes a first punch assembly, a mold body, a second punch assembly, a drive device, and a density detection device. The first punch assembly includes a first punch, a first cavity mold sleeve, a first ultrasonic generator, and a first drive plate. The first drive plate and the first punch are respectively installed at the top and bottom of the first cavity mold sleeve. The first ultrasonic generator is installed inside the first cavity mold sleeve and connected to the first punch. The second punch assembly includes a second punch, a second cavity mold sleeve, a second ultrasonic generator, and a second drive plate. The second drive plate and the second punch are respectively installed at the top and bottom of the second cavity mold sleeve. The second ultrasonic generator is installed inside the second cavity mold sleeve and connected to the second punch. The first punch assembly and the second punch assembly are respectively installed in the mold body. The mold has two ends, and the mold body, the first punch, and the second punch form a cavity. The cavity is used to hold powder. The density detection device is used to detect the compact density of the powder in the cavity. The driving force of the driving device acts on the first driving plate and the second driving plate respectively, driving the first punch and the second punch to move. During the movement of the first punch and the second punch, the first ultrasonic generator and the second ultrasonic generator perform ultrasonic vibration and drive the first punch and the second punch to vibrate. The included angle of the tips of the first punch and the second punch, the vibration frequency, the vibration amplitude, the moving speed, and the displacement are adjusted according to the compact density. The included angle of the tips of the first punch and the second punch is adjusted by rolling rollers on both sides. The range of the included angle is... .

2. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 1, characterized in that, The first punch and the first cavity mold sleeve, as well as the second punch and the second cavity mold sleeve, are flexibly connected by a buffer device.

3. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 1, characterized in that, It also includes a mounting base, which is fixedly mounted on the first punch and the second punch, and the first ultrasonic generator and the second ultrasonic generator are fixedly mounted on the mounting base.

4. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 3, characterized in that, The mounting base is made of plastic or ceramic material.

5. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 1, characterized in that, The first and second ultrasonic generators are equipped with grounding devices.

6. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 1, characterized in that, The mold body is a cylindrical structure, and the first punch assembly and the second punch assembly are respectively installed at both ends of the cylindrical structure.

7. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 6, characterized in that, The density detection device includes a near-infrared high-speed imaging system, which includes a detection device installed inside the side wall of the cylindrical structure.

8. The ultrasonic-assisted punch vibration powder bidirectional pressing and forming device according to claim 1, characterized in that, The driving device includes a hydraulic press, and the output shaft of the hydraulic press is connected to the first driving plate and the second driving plate respectively.

9. A method for bidirectional pressing and molding of powder using an ultrasonic-assisted punch, characterized in that... The ultrasonic-assisted punch vibration powder bidirectional pressing molding device according to any one of claims 1-8 includes the following steps: 1) Move the first punch assembly to a first position above the mold body, and move the second punch assembly to a second position inside the mold body to place the powder into the cavity; 2) The drive device is activated to drive the first punch assembly and the second punch assembly to move relative to each other until the powder compact is pressed to the specified thickness. The first punch assembly and the second punch assembly then remain stationary and maintain pressure. During the movement of the first punch assembly and the second punch assembly, the density detection device is activated to detect the density of the powder compact in the cavity. The first ultrasonic generator and the second ultrasonic generator are activated to perform ultrasonic vibration and drive the first punch and the second punch to vibrate. The included angle between the tips of the first punch and the second punch, the vibration frequency, the vibration amplitude, the moving speed, and the displacement are adjusted according to the compact density, as shown in the following formula: ； ； in, and These are the moving speeds of the first punch and the second punch, respectively. The density of the pressed billet, and These are the functional relationships between the moving speeds of the first punch and the second punch, respectively, and the density of the pressed blank. ； ； in, and These are the displacements of the first punch and the second punch, respectively. and These are the functional relationships between the displacements of the first punch and the second punch, respectively, and the density of the pressed blank. ； ； ； ； in, , , , , These represent the vibration amplitude of the first ultrasonic generator, the vibration amplitude of the second ultrasonic generator, the maximum vibration amplitude, the vibration frequency of the first ultrasonic generator, and the vibration frequency of the second ultrasonic generator, respectively. and , respectively, represent the functional relationship between the vibration frequencies of the first punch and the second punch and the density of the blank, where t is time.

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