CN112877515B

CN112877515B - Surface strengthening device and method for applying pulse current field to metal workpiece and assisting ultrasonic rolling

Info

Publication number: CN112877515B
Application number: CN202110047273.1A
Authority: CN
Inventors: 李宇罡; 王浩伟; 陈东; 耿继伟; 夏存娟; 汪明亮; 李险峰; 吴一; 马乃恒
Original assignee: Anhui Xiangbang Composite Material Ltd; Shanghai Jiaotong University
Current assignee: Anhui Xiangbang Composite Material Ltd; Shanghai Jiaotong University
Priority date: 2021-01-14
Filing date: 2021-01-14
Publication date: 2022-11-01
Anticipated expiration: 2041-01-14
Also published as: CN112877515A

Abstract

The invention provides a surface strengthening device and a surface strengthening method for applying a pulse current field to a metal workpiece and assisting ultrasonic rolling, wherein the metal workpiece is clamped between rotating output shafts of two spindle boxes, and the surface strengthening device is used for applying the pulse current field to the surface of the metal workpiece while applying the ultrasonic rolling to the surface of the metal workpiece, so that the surface residual compressive stress level and the peak residual compressive stress level of the metal material are higher, the residual compressive stress influence layer is deeper, and the fatigue performance of the metal material is further improved.

Description

Surface strengthening device and method for applying pulse current field to metal workpiece and assisting ultrasonic rolling

Technical Field

The invention relates to the field of metal surface mechanical strengthening, in particular to a surface strengthening device and a surface strengthening method for applying a pulse current field to a metal workpiece and assisting ultrasonic rolling.

Background

One of the most important factors affecting fatigue properties of metal materials is residual stress. The residual compressive stress can partially or even completely counteract the tensile external load, close the microcrack, inhibit the formation of a fatigue crack source, and delay the expansion of the fatigue crack, thereby improving the fatigue performance of the metal member. Ultrasonic rolling is an advanced mechanical surface strengthening method, and can generate a residual compressive stress field on the surface layer of a metal component to improve the fatigue performance of the metal component. Important indexes of the surface layer residual compressive stress field generated by ultrasonic rolling comprise the surface residual compressive stress level, the peak value residual compressive stress level and the depth of the layer affected by the residual compressive stress.

The existing ultrasonic rolling strengthening method has certain limitations, the level of the generated surface residual compressive stress and peak residual compressive stress is low, the influence layer of the residual compressive stress is shallow, and the fatigue performance of a metal material cannot be improved to the maximum extent, so that a more complete ultrasonic rolling surface strengthening method needs to be sought.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a surface strengthening device for applying a pulse current field to a metal workpiece and assisting ultrasonic rolling, wherein the metal workpiece is a cylindrical workpiece, and the surface strengthening device comprises:

the double-spindle synchronous rotation system comprises two spindle boxes which are symmetrically arranged and a synchronous motion base positioned between the two spindle boxes, output shafts of the two spindle boxes are connected with the same telescopic synchronous shaft through synchronous belts, clamping devices are respectively arranged at opposite ends of the two output shafts, and metal workpieces of which two ends are sleeved with insulating sleeves are fixed between the two clamping devices so as to be mutually insulated;

the ultrasonic rolling system is arranged on the synchronous motion base and is positioned on one side of the metal workpiece, the synchronous motion base is used for driving the ultrasonic rolling system to make feeding motion along the axial direction of the metal workpiece, and the ultrasonic rolling system comprises an ultrasonic rolling head which can be radially close to/far away from the metal workpiece;

the pulse current field loading device is arranged on the synchronous motion base and located on the other side of the metal workpiece, the pulse current field loading device is provided with an upper electrode and a lower electrode which are symmetrically arranged, the ends of the two electrodes are respectively and radially abutted against the upper side and the lower side of the outer diameter of the metal workpiece, the two electrodes and the ultrasonic rolling head are both located in the same circumferential plane with the axis of the metal workpiece as the center of a circle, pulse current is conducted to the metal workpiece through the two electrodes to reduce the resistance of ultrasonic rolling deformation, and the synchronous motion base is used for simultaneously driving the ultrasonic rolling system and the electrodes to perform axial feeding motion along the metal workpiece according to the set feeding speed and direction.

Furthermore, a main shaft servo motor for driving the telescopic synchronizing shaft to rotate is fixed on the first main spindle box.

Further, the strengthening device further comprises: the horizontal moving driving system is used for driving the first spindle box to horizontally move away from the second spindle box, the horizontal moving driving system is provided with a set of horizontal driving device connected with the first spindle box, the horizontal driving device comprises a hydraulic driving device and a piston rod, wherein an oil pressure valve is arranged on the hydraulic driving device, and the hydraulic driving device is connected with the first spindle box through the piston rod;

two headstock are all installed on the slide rail of lathe bed.

Further, the pulse current field loading device is provided with an arc-shaped support, the arc-shaped support is provided with an arc-shaped sliding groove, two insulating sliding sleeves are arranged on the arc-shaped sliding groove, and the two electrodes are respectively arranged on the two insulating sliding sleeves;

one end of each electrode penetrates through the insulating sliding sleeve and is in radial butt joint with the outer diameter of the metal workpiece, and the other end of each electrode is connected with a pulse power supply through an enameled wire.

Furthermore, a second base is installed on the synchronous motion base, and the arc-shaped support is installed on the second base through a connecting rod.

Further, the ultrasonic rolling head approaches/departs from the metal workpiece in a radial direction of the metal workpiece.

A method for strengthening the surface of a metal workpiece by using the device comprises the following steps:

s1, fixing two axial ends of a metal workpiece between two coaxial clamping devices, and sleeving insulating sleeves at the two axial ends of the metal workpiece to insulate the metal workpiece from the clamping devices;

s2, respectively and radially abutting the ends of two electrodes for loading a pulse current field against the upper side and the lower side of the outer diameter of the metal workpiece, and switching on a pulse power supply to apply the pulse current field to the metal workpiece;

s3, starting a double-spindle synchronous rotating system, enabling two clamping devices to rotate synchronously to drive the metal workpiece to rotate according to a set rotating speed and a set rotating direction, and enabling the synchronous movement base to operate to drive electrodes of the ultrasonic rolling system and the pulse current field loading device to move along the axial direction of the metal workpiece according to a set feeding speed and a set feeding direction;

s4, starting an ultrasonic rolling system, wherein an ultrasonic rolling head of the ultrasonic rolling system is close to the metal workpiece in the radial direction and continues to perform feeding motion along the axial direction of the metal workpiece, and ultrasonic rolling surface strengthening is performed on the rotating metal workpiece under the assistance of a pulse current field;

s5, after the ultrasonic rolling is finished, closing the double-main-shaft synchronous rotating system, stopping the rotation of the metal workpiece, stopping the feeding motion of the ultrasonic rolling system and the pulse current field loading device along the axial direction of the metal workpiece, and then enabling the ultrasonic rolling head to be radially far away from the metal workpiece;

s6, closing the pulse power supply, and stopping applying a pulse current field to the metal workpiece;

s7, loosening the two clamping devices and taking down the metal workpiece.

In some embodiments, the metal workpiece is clamped between the rotating output shafts of the two spindle boxes, and the strengthening device is used for applying a pulse current field to the surface of the metal workpiece while applying ultrasonic rolling to the surface of the metal workpiece, so that the surface residual compressive stress level and the peak residual compressive stress level of the metal material are higher, the residual compressive stress influence layer is deeper, and the fatigue performance of the metal material is further improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the embodiments or the prior art description will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings may be obtained according to these drawings without inventive labor.

FIG. 1a shows a schematic diagram of a surface enhancing apparatus for applying multiple physical fields to a metal workpiece and assisting ultrasonic rolling;

FIG. 1b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 1 a;

FIG. 2a shows a schematic view of an apparatus for applying an elastic stress field to a metal workpiece and assisting ultrasonic rolling;

FIG. 2b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 2 a;

FIG. 2c is a schematic view showing two ring-shaped clamps mounted on two headstock to clamp and fix two ends of a metal workpiece;

FIG. 3a shows a schematic view of an apparatus for applying a pulsed current field to a metal workpiece and assisting ultrasonic rolling;

FIG. 3b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 3 a;

FIG. 3c shows a schematic diagram of a pulsed electric current field loading device and an ultrasonic rolling system;

FIG. 4a shows a schematic view of an intensifying apparatus for applying a thermal field to a metal workpiece and assisting ultrasonic rolling;

FIG. 4b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 4 a;

FIG. 4c shows a schematic view of a thermal field loading device and ultrasonic rolling system;

FIG. 5a shows a schematic diagram of an apparatus for applying a pulsed electromagnetic field to a metal workpiece and assisting ultrasonic rolling;

FIG. 5b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 5 a;

FIG. 5c is a schematic diagram of a pulsed electromagnetic field loading device and ultrasonic rolling system;

FIG. 6a shows a schematic view of an apparatus for applying a deep cooling field to a metal workpiece and assisting ultrasonic rolling;

FIG. 6b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 6 a;

FIG. 6c shows a schematic diagram of a cryogenic field loading device and ultrasonic rolling system;

FIG. 7a shows a schematic diagram of an apparatus for applying an elastic stress field and a pulsed current field to a metal workpiece and assisting ultrasonic rolling;

FIG. 7b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 7 a;

FIG. 7c shows a schematic of an annular fixture for holding a metal fixture along with a pulsed electric current field loading device and an ultrasonic rolling system;

FIG. 8a shows a schematic view of an apparatus for applying elastic stress and thermal fields to a metal workpiece and assisting ultrasonic rolling;

FIG. 8b is a flow chart of a method for strengthening the surface of a metal workpiece based on the apparatus of FIG. 8 a;

FIG. 8c shows a schematic of a ring clamp for clamping a metal clamp, along with a thermal field loading device and ultrasonic rolling system;

FIG. 9a shows a schematic diagram of an apparatus for applying an elastic stress field and a pulsed electromagnetic field to a metal workpiece and assisting ultrasonic rolling;

FIG. 9b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 9 a;

FIG. 9c shows a schematic of a ring clamp for holding a metal clamp, together with a pulsed electromagnetic field loading device and an ultrasonic rolling system;

FIG. 10a shows a schematic view of an apparatus for applying elastic stress fields and cryogenic fields to a metal workpiece and assisting ultrasonic rolling;

FIG. 10b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 10 a;

FIG. 10c shows a schematic of an annular clamp for clamping a metal clamp, together with cryogenic field loading and ultrasonic rolling system;

FIG. 11a shows a schematic view of an apparatus for applying elastic stress, thermal and cryogenic fields to a metal workpiece and assisting ultrasonic rolling;

FIG. 11b shows a flow chart of a method for surface strengthening a metal workpiece based on the apparatus of FIG. 11 a;

FIG. 11c shows a schematic of an annular clamp for clamping a metal clamp along with cryogenic field loading, thermal field loading and ultrasonic rolling systems;

FIG. 12a shows an exploded view of an elastic stress field loading device for clamping two ends of a metal workpiece;

12b-1 through 12b-6 illustrate an installation process for securing a metal workpiece with an elastic stress field loading device;

FIG. 13a is a graph comparing the residual stress effect of a metal workpiece surface subjected to only ordinary ultrasonic rolling and elastic stress field assisted ultrasonic rolling;

FIG. 13b is a comparison graph of residual stress effects of only performing ordinary ultrasonic rolling and applying pulsed current field assisted ultrasonic rolling, and applying elastic stress field-pulsed current field assisted ultrasonic rolling on the surface of a metal workpiece;

FIG. 13c is a graph showing the residual stress effect of the metal workpiece surface subjected to only ordinary ultrasonic rolling and thermal field assisted ultrasonic rolling, elastic stress field-thermal field assisted ultrasonic rolling, and elastic stress field-thermal field-cryogenic field assisted ultrasonic rolling;

FIG. 13d is a graph showing the comparison of residual stress effects between the normal ultrasonic rolling and the pulsed electromagnetic field assisted ultrasonic rolling, and between the elastic stress field and the pulsed electromagnetic field assisted ultrasonic rolling;

fig. 13e is a comparison graph of residual stress effects of only performing ordinary ultrasonic rolling and applying cryogenic field to assist ultrasonic rolling, and applying elastic stress field-cryogenic field to assist ultrasonic rolling on the surface of the metal workpiece.

Detailed Description

In some embodiments, the following apparatuses and methods for reinforcing the surface of one or more metal materials by ultrasonic rolling assisted by a physical field are provided, so that the level of the surface residual compressive stress and the level of the peak residual compressive stress generated on the surface of the metal material are higher, the influence layer of the residual compressive stress is deeper, and the fatigue performance of the metal material is further improved.

Wherein in-situ TiB is selected₂The/2024 Al composite material takes a dumbbell-shaped round bar-shaped test piece recommended by the Metal Material force control constant amplitude axial fatigue test Standard (ASTME 466-15) as an example.

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. These are all within the scope of the present invention.

Example one

This embodiment is an application example corresponding to fig. 1a-1b, in which fig. 1a is a schematic view of a surface strengthening apparatus 1000, and fig. 1b is a flowchart illustrating a surface strengthening process performed on a metal workpiece by the surface strengthening apparatus 1000.

As shown in fig. 1a, a metal material physical field assisted ultrasonic rolling surface strengthening device 1000 is shown, which comprises a dual-spindle synchronous rotating system 1, an ultrasonic rolling system 2, a metal workpiece 3, a traverse driving system 4 and a physical field loading system 5.

The double-spindle synchronous rotating system 1 comprises a first spindle box 1-1, a second spindle box 1-2, a first spindle 1-3, a second spindle 1-4, a spindle servo motor 1-5, a spindle synchronous driving belt 1-6, a telescopic synchronous shaft 1-7, a first spindle synchronous driven belt 1-8, a second spindle synchronous driven belt 1-9, a lathe bed 1-10, a synchronous moving base 1-11, an ultrasonic rolling system base 1-12, a second base 1-13, a third base 1-14, a first clamping device 1-15 and a second clamping device 1-16.

Wherein, the main shaft servo motor 1-5 is positioned at the top of the first main shaft box 1-1. The main shaft servo motors 1-5 are connected with the telescopic synchronous shafts 1-7 through main shaft synchronous driving belts 1-6. The telescopic synchronous shafts 1-7 are respectively connected with the first main shafts 1-3 and the second main shafts 1-4 through first main shaft synchronous driven belts 1-8 and second main shaft synchronous driven belts 1-9. And a third base 1-14 is arranged at the top of the second spindle box 1-2. The first main shaft 1-3 and the second main shaft 1-4 are respectively arranged in the first main shaft box 1-1 and the second main shaft box 1-2; the first spindle box 1-1, the second spindle box 1-2 and the synchronous motion base 1-11 are respectively arranged on a slide rail of the machine body 1-10, and the synchronous motion base 1-11 can move along the slide rail of the machine body 1-10 under the drive of a lead screw. One end of the synchronous motion base 1-11 is provided with an ultrasonic rolling system base 1-12, and the other end is provided with a second base 1-13; the first clamping device 1-15 and the second clamping device 1-16 are respectively provided with a clamping jaw; the front end of the clamping jaw is provided with a boss clamping tooth; the first clamping means 1-15 and the second clamping means 1-16 are mounted on one side of the first spindle 1-3 and the second spindle 1-4, respectively, such that the jaws of the first clamping means 1-15 and the jaws of the second clamping means 1-16 face opposite and can clamp the metal workpiece 3.

Further, the ultrasonic rolling system 2 is mounted on the ultrasonic rolling system bases 1-12, and the ultrasonic rolling system bases 1-12 are mounted on the other side of the synchronously moving bases 1-11 opposite to the metal workpiece 3.

Further, the traverse drive system 4 includes a hydraulic drive device 4-1 and a piston rod 4-2. An oil pressure valve is arranged on the hydraulic driving device 4-1, and the hydraulic driving device 4-1 is connected with the first spindle box 1-1 through a piston rod 4-2, so that the hydraulic driving device 4-1 can drive the first spindle box 1-1 to move along a slide rail of the machine tool body 1-10.

Wherein physical field loading system 5 comprises one or more of a first physical field loading system 501, a second physical field loading system 502, and a third physical field loading system 503. Wherein the first physical field loading system 501 may comprise an elastic stress field system 501a. The first physical field loading system 501 may be regarded as a traverse driving system 4, and the traverse driving system 4 drives the first spindle box 1-1 to horizontally traverse away from the second spindle box 1-2 to draw the metal workpiece 3 according to a set stress level, so as to apply an elastic stress field to the metal workpiece 3. The second physical field loading system 502 can include one or more of a pulsed current field system 502a, a thermal field system 502b, a pulsed electromagnetic field system 502 c. Third physical site loading system 503 may include a cryogenic site system 503a.

Further, the second physical field loading system 502 and the third physical field loading system 503 may be installed on the second bases 1 to 13 or the third bases 1 to 14 singly, or installed on both the second bases 1 to 13 and the third bases 1 to 14 simultaneously, or installed on both the second bases 1 to 13 or the third bases 1 to 14 simultaneously and compactly, depending on the type.

As shown in fig. 1b, a metal material physical field assisted ultrasonic rolling surface strengthening method is shown, which sequentially comprises seven steps of clamping a workpiece, applying a physical field, applying rotation and feeding, ultrasonic rolling, stopping rotation and feeding, unloading the physical field and taking down the workpiece, and the sequence of the steps is adjusted according to different needs of a physical field system to obtain beneficial effects. The specific steps in this example are as follows:

s1, clamping a workpiece: the first clamping devices 1-15 and the second clamping devices 1-16 are screwed to clamp the two ends of the metal workpiece 3 through the clamping jaws.

S2, applying a physical field: starting the physical field loading system 5, applying physical fields including but not limited to the following to the metal workpiece 3: elastic stress field, pulse current field, thermal field, pulse electromagnetic field, and cryogenic field.

S3, rotation and feeding are applied: starting the double-spindle synchronous rotating system 1, setting a rotating speed, and driving a first spindle 1-3 and a first clamping device 1-15 and a second spindle 1-4 and a second clamping device 1-16 to synchronously rotate by a spindle servo motor 1-5 through a spindle synchronous driving belt 1-6, a telescopic synchronous shaft 1-7, a first spindle synchronous driven belt 1-8 and a second spindle synchronous driven belt 1-9, so as to drive the metal workpiece 3 to rotate according to the set rotating speed; the synchronous motion bases 1-11 operate to drive the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 arranged on the second bases 1-13 to axially feed along the metal workpiece 3 at a set feeding speed and direction.

S4, ultrasonic rolling: the ultrasonic rolling head of the ultrasonic rolling system 2 is close to the metal workpiece 3 in the radial direction and continues to perform feeding motion along the axial direction of the metal workpiece 3, and the ultrasonic rolling surface strengthening under the assistance of an elastic stress field is performed on the rotating metal workpiece 3, and the ultrasonic rolling surface strengthening under the assistance of a physical field is performed on the metal workpiece 3.

S5, stopping rotation and feeding: the double-spindle synchronous rotating system 1 is closed, the rotation of the metal workpiece 3 is stopped, the feeding motion of the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 installed on the second bases 1 to 13 along the axial direction of the metal workpiece 3 is stopped, and then the ultrasonic rolling head is radially far away from the metal workpiece 3.

S6, unloading the physical field: and after the ultrasonic rolling is finished, closing the physical field loading system 5 and stopping applying the physical field to the metal workpiece 3.

S7, taking down the workpiece: the first clamping means 1-15 and the second clamping means 1-16 are released, whereby the metal work piece 3 is removed.

In particular, depending on the physical field system, the application or unloading of the physical field before or after the ultrasonic rolling step can further increase the level of skin residual compressive stress and depth of layer produced by ultrasonic rolling, and is further illustrated in the examples below.

Example two

As shown in fig. 2a, another metal material physical field assisted ultrasonic rolling surface strengthening device 2000 is shown, wherein the physical field loading system 5 adopted is a first physical field loading system 501, and the first physical field loading system 501 is an elastic stress field system 501a. The elastic stress field system 501a comprises ring clamps, i.e. a first clamp 501a-1 and a second clamp 501a-2 in fig. 2a, which are fixed to two clamping devices, respectively. One end of the metal workpiece 3 can be inserted into and fixed at one end of the first clamp 501a-1, and the other end of the first clamp 501a-1 is provided with a cylindrical boss; the other end of the metal workpiece 3 can be inserted into and fixed to one end of the second jig 501a-2, and the other end of the second jig 501a-2 is provided with a cylindrical boss. The metal workpiece 3 is made of in-situ TiB₂The/2024 Al composite material is numbered as A-2.

As shown in fig. 2b, the surface strengthening method of the corresponding device 2000 is shown, which comprises seven steps of clamping the workpiece, applying the physical field, applying rotation and feeding, ultrasonic rolling, stopping rotation and feeding, unloading the physical field and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field is applying an elastic stress field, and the step of unloading the physical field is unloading the elastic stress field.

Particularly, the workpiece clamping step comprises: both ends of the metal workpiece 3 are inserted into one ends of the first and second clamps 501a-1 and 501a-2, respectively, and fixed, and then the other ends of the first and second clamps 501a-1 and 501a-2 are clamped by jaws of the first and second clamping devices 1-15 and 1-16, respectively, as shown in fig. 2 c. In particular, after clamping, the tooth surfaces of the boss latches of the jaws must be in good contact with the cylindrical surfaces of the first and second clamps 501a-1 and 501a-2 to ensure the coaxiality of the entire device; the inside vertical surfaces of the boss latches of the jaws must be brought into good contact with the inside vertical surfaces of the cylindrical bosses at the other ends of the first and second clamps 501a-1 and 501a-2 to ensure that the hydraulic load provided by the hydraulic drive 4-1 is accurately applied to the metal workpiece 3 via the piston rod 4-2, the first headstock 1-1, the first spindle 1-3, the first clamp 1-15, and the first clamp 501 a-1.

The step of applying the elastic stress field comprises the following steps: calculating the required oil pressure according to the cross sectional areas of the metal workpiece 3 and the piston rod 4-2 and the preset elastic stress, wherein the strength of the applied elastic stress field does not exceed the uniaxial tension proportion limit value of the material used for the metal workpiece 3; the hydraulic driving device 4-1 is started, oil pressure is adjusted through an oil pressure valve, the first spindle box 1-1, the first spindle 1-3 and the first clamping device 1-15 are driven by the piston rod 4-2 to transversely move along the slide rail of the lathe bed 1-10 in the direction far away from the second spindle box 1-2, and therefore a single-axis tensile elastic stress field with a preset size is applied to the metal workpiece 3.

The step of unloading the elastic stress field is as follows: and closing the hydraulic driving device 4-1, and removing the oil pressure in the transverse moving driving system 4 to enable the metal workpiece 3 to elastically recover.

In particular, the application of the elastic stress field before the ultrasonic rolling step and the unloading of the elastic stress field after the ultrasonic rolling step can induce elastic stress superposition and resultant force-resultant moment rebalancing in the metal workpiece 3, thereby further improving the level and depth of the surface layer residual compressive stress generated by the ultrasonic rolling.

In particular, the above-mentioned advantageous effects can be obtained only when the steps as shown in fig. 2b are sequentially performed.

In this embodiment, the parameters of each step are: firstly clamping a No. A-2 workpiece, then applying a 150MPa uniaxial tensile elastic stress field to the No. A-2 workpiece, then rotating the No. A-2 workpiece at a rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the No. A-2 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feed rate is 0.1mm/r, stopping the rotation and axial feed of the workpiece after the ultrasonic rolling is finished, unloading the uniaxial tensile elastic stress field, and finally taking down the workpiece.

EXAMPLE III

As shown in FIG. 3a, another metal material physical field assisted ultrasonic rolling surface strengthening device 3000 is shown, wherein the physical field loading system 5 adopted is a second physical field loading system 502, the second physical field loading system 502 is a pulsed electric current field system 502a, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-3.

As shown in fig. 3b, a surface strengthening method corresponding to the illustrated apparatus 3000 is shown, sequentially including seven steps of clamping a workpiece, applying a physical field, applying rotation and feed, ultrasonic rolling, stopping rotation and feed, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field is applying a pulsed current field and the step of unloading the physical field is unloading the pulsed current field.

Particularly, the workpiece clamping step comprises: insulating rubber sleeves are respectively sleeved at two ends of a metal workpiece 3, and then the first clamping devices 1-15 and the second clamping devices 1-16 are used for respectively clamping the two ends of the metal workpiece 3.

The step of applying the pulse current field comprises the following steps: adjusting the positions of the first electrode 502a-1 and the second electrode 502a-2 on the arc-shaped support 502a-3 to be in the same plane with the rolling head at the tip of the ultrasonic rolling system 2, so as to ensure that the rolling head is in an electric path between the electrodes, as shown in fig. 3 c; the first electrode 502a-1 and the second electrode 502a-2 are kept in good contact with the surface of the metal workpiece 3, then the power supply 502a-5 is started, the preset pulse current parameters are adjusted, and pulse current is supplied to the metal workpiece 3 through the lead 502a-4, the first electrode 502a-1 and the second electrode 502 a-2.

The metal material is an electric good conductor, and can generate a pulse Joule heating effect under the action of a pulse electric flow field, and the deformation resistance of the metal workpiece 3 in the ultrasonic rolling process can be effectively reduced by the heat activation and the thermal expansion caused by the pulse Joule heating effect. In addition, the skin effect generated by the high-frequency pulse current can increase the current density on the surface layer of the material, so that the joule heat effect is more concentrated on the surface of the material.

Particularly, the pulse current field is applied before the ultrasonic rolling step, and the pulse current field is unloaded after the ultrasonic rolling step, so that the plastic effect, the skin effect and the joule heating effect can be generated in the metal workpiece 3, the ultrasonic rolling deformation resistance is reduced, and the plastic flow characteristic of the surface layer material is improved, so that the level and the depth of the surface layer residual compressive stress generated by ultrasonic rolling are further improved.

The steps of unloading the pulse current field are as follows: the power supply 502a-5 is turned off and the pulse current to the metal workpiece 3 is stopped.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 3b are sequentially performed.

In this embodiment, the parameters of each step are: firstly clamping an A-3 workpiece, and then applying a pulse frequency of 20000Hz, a pulse width of 1 mu s, a duty ratio of 50 percent and a peak current density of 30A/mm to the A-3 workpiece²And finally, carrying out ultrasonic rolling surface strengthening on the A-3 workpiece under the conditions that a rolling head is a tungsten carbide hard alloy ball with the diameter of phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feed rate is 0.1mm/r, stopping the rotation and axial feed of the workpiece after the ultrasonic rolling is finished, unloading the pulse current field, and finally taking down the workpiece.

Example four

As shown in FIG. 4a, another metal material physical field assisted ultrasonic rolling surface strengthening device 4000 is shown, wherein a physical field plus is adoptedThe carrier system 5 is a second physical field loading system 502, the second physical field loading system 502 is a thermal field system 502b, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-4.

As shown in fig. 4b, a surface strengthening method corresponding to the illustrated apparatus 4000 is illustrated, which sequentially comprises seven steps of clamping a workpiece, applying a physical field, applying rotation and feeding, ultrasonically rolling, stopping rotation and feeding, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field is applying the thermal field, and the step of unloading the pulsed electric current field is unloading the thermal field.

In particular, the step of applying the thermal field is: the power supply 502b-1 is started, the output voltage and current of the controller 502b-3 are adjusted, and the heater 502b-4 is powered on through the bracket 502b-2 with the conducting wire inside to heat the metal workpiece 3, as shown in fig. 4 c; the temperature of the metal workpiece 3 is monitored in real time by the temperature monitor 502b-5 and the voltage and the current output by the controller 502b-3 are fed back and adjusted, so that the middle part of the metal workpiece 3 is heated to the preset temperature. Particularly, the temperature of the middle heating part of the metal workpiece 3 needs to be monitored in real time during the heating process and fed back to the feedback regulation controller 502b-3 to regulate and control the temperature of the heating part of the metal workpiece 3 to be maintained at a specified temperature in real time, and the heating temperature of the middle part of the metal workpiece 3 does not exceed the second phase precipitation temperature of the material used for the metal workpiece 3.

The steps of unloading the thermal field are as follows: the heater 502b-4 is turned off and the application of the thermal field to the metal workpiece 3 is stopped.

The step of taking down the workpiece is as follows: the first clamping means 1 to 15 and the second clamping means 1 to 16 are released to remove the metal workpiece 3, and then the metal workpiece 3 is left to stand to return its temperature to room temperature.

In particular, applying the thermal field before the ultrasonic rolling step and unloading the thermal field after the ultrasonic rolling step can induce thermal activation and thermal expansion in the metal workpiece 3, reduce the ultrasonic rolling deformation resistance, improve the plastic flow characteristics of the skin material, and further increase the level and depth of the skin residual compressive stress generated by the ultrasonic rolling.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 4b are sequentially performed.

In this embodiment, the parameters of each step are: firstly clamping an A-4 workpiece, then applying a thermal field to heat the workpiece to 150 ℃, then enabling the A-4 workpiece to rotate at a rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-4 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with the diameter of phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, and the axial feed rate is 0.1mm/r, stopping the rotation and the axial feed of the workpiece after the rolling is finished, unloading the thermal field to enable the temperature to be recovered to the room temperature, and finally taking down the workpiece.

EXAMPLE five

As shown in FIG. 5a, another metal material physical field assisted ultrasonic rolling surface strengthening device 5000 is shown, wherein the physical field loading system 5 adopted is a second physical field loading system 502, the second physical field loading system 502 is a pulsed electromagnetic field system 502c, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-5.

As shown in fig. 5b, the surface strengthening method corresponding to the illustrated apparatus 5000 is shown, which comprises seven steps of clamping the workpiece, applying a physical field, applying rotation and feeding, ultrasonic rolling, stopping rotation and feeding, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field is applying a pulsed electromagnetic field and the step of unloading the physical field is unloading the pulsed electromagnetic field.

In particular, the step of applying a pulsed electromagnetic field is: starting the controller 502c-4, adjusting to preset pulse electromagnetic parameters, and electrifying the induction coil 502c-1 connected to the bracket 502c-2 through the lead 502 c-3; a pulsed electromagnetic field is applied to the metal workpiece 3 by the induction coil 502 c-1. In particular, the induction coil 502c-1 should be composed of two coils arranged in parallel with a spacing equal to the coil radius, as shown in fig. 5c, so that the pulsed electromagnetic field is densely and uniformly distributed in the middle portion of the metal workpiece 3.

The step of unloading the pulsed magnetic field comprises the following steps: the controller 502c-4 is turned off and the application of the pulsed electromagnetic field to the metal workpiece 3 is stopped.

Particularly, the pulsed electromagnetic field is applied before the ultrasonic rolling step, and the pulsed electromagnetic field is unloaded after the ultrasonic rolling step, so that the magnetostrictive effect can be caused in the metal workpiece 3, the resistance to ultrasonic rolling deformation is reduced, and the plastic flow characteristic of the surface layer material is improved, thereby further improving the level and the depth of the residual compressive stress of the surface layer generated by the ultrasonic rolling.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 5b are sequentially performed.

In this embodiment, the parameters of each step are: firstly clamping an A-5 workpiece, then applying a pulse electromagnetic field with the pulse frequency of 200Hz, the pulse width of 5ms and the peak magnetic induction intensity of 3T to the A-5 workpiece, then rotating the A-5 workpiece at the rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-5 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with the diameter of 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feed rate is 0.1mm/r, the rotation and the axial feed of the workpiece are stopped after the rolling is finished, the pulse magnetic field is unloaded, and finally the workpiece is taken down.

EXAMPLE six

As shown in FIG. 6a, another metal material physical field assisted ultrasonic rolling surface strengthening device 6000 is shown, wherein the physical field loading system 5 adopted is a third physical field loading system 503, the third physical field loading system 503 is a cryogenic field system 503a, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-6.

As shown in fig. 6b, a surface strengthening method corresponding to the illustrated apparatus 6000 is shown, sequentially including seven steps of clamping a workpiece, applying rotation and feed, ultrasonic rolling, applying a physical field, stopping rotation and feed, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the sequence of the steps:

the step of applying the physical field is applying the deep cooling field, and the step of unloading the physical field is unloading the deep cooling field.

Particularly, the workpiece clamping step comprises: fixing two axial ends of the metal workpiece 3 between the two clamping devices, and enabling the metal workpiece 3 to be positioned on the spraying intersection line of the two groups of spray heads 503 a-1;

the step of applying the cryogenic field comprises the following steps: and starting the controller 503a-4, adjusting to the preset cryogenic medium ejection flow, and immediately ejecting the cryogenic medium to the metal workpiece 3 through the tank 503a-5, the guide pipe 503a-3 and the nozzle 503a-1 fixed on the bracket 503a-2 for a preset duration after the ultrasonic rolling is finished.

The step of unloading the deep cooling field comprises the following steps: the controller 503a-4 is turned off and the injection of the cryogenic medium to the metal workpiece 3 is stopped.

During ultrasonic rolling of metal materials, a large amount of heat is generated by friction between the surface of the material and a rolling head. After rolling, the metal workpiece 3 is quickly placed in a deep cooling medium atmosphere, and the workpiece can be quickly cooled. Because the temperature gradient of the surface layer of the metal workpiece 3 is higher than that of the inner part thereof, the rapid cooling process can obviously improve the level and the depth of the residual compressive stress of the surface layer of the metal workpiece 3.

In particular, a large temperature gradient of drop can be generated in the surface layer of the metal workpiece 3 by applying and unloading the cryogenic field sequentially after the ultrasonic rolling step, thereby further increasing the level and depth of the surface layer residual compressive stress generated by the ultrasonic rolling.

The step of taking down the workpiece is as follows: the metal workpiece 3 is taken down and left to stand, and the temperature is returned to room temperature.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 6b are sequentially performed.

In this embodiment, the parameters of each step are: firstly clamping an A-5 workpiece, then rotating the A-6 workpiece at a rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-6 workpiece under the rolling conditions that a rolling head is a tungsten carbide hard alloy ball with phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feed rate is 0.1mm/r, then spraying a cryogenic medium to the ultrasonically rolled workpiece at a flow rate of 1L/min for 5min, then unloading a cryogenic field, and finally taking down the workpiece to restore the temperature to the room temperature.

EXAMPLE seven

As shown in fig. 7a, another metal material physical field assisted ultrasonic rolling surface strengthening device 7000 is shown, wherein the physical field loading systems 5 adopted are a first physical field loading system 501 and a second physical field loading system 502, the first physical field loading system 501 is an elastic stress field system 501a, and the second physical field loading system 502 is a pulsed electric current field system 502a. The workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-7.

As shown in fig. 7b, a surface strengthening method corresponding to the illustrated apparatus 7000 is shown, sequentially seven steps of clamping the workpiece, applying the physical field, applying rotation and feed, ultrasonic rolling, stopping rotation and feed, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field comprises the steps of applying an elastic stress field and applying a pulse current field in sequence; and the step of unloading the physical field comprises the steps of unloading the pulse current field and unloading the elastic stress field in sequence.

In particular, the step of applying the elastic stress field is the same as the step of applying the elastic stress field in the surface strengthening method of the second embodiment;

the step of applying a pulsed current field is the same as the step of applying a pulsed current field in the surface strengthening method in the third embodiment;

the step of unloading the pulsed current field is the same as the step of unloading the pulsed current field in the surface strengthening method in the third embodiment;

the step of unloading the elastic stress field is the same as the step of unloading the elastic stress field in the surface strengthening method in the second embodiment.

Particularly, the workpiece clamping step comprises: that is, ring-shaped clamps 501a-1 and 501a-2 are respectively fixed to the two clamping devices, and then the metal workpiece 3 with the insulating sleeve at both ends is axially fixed between the two ring-shaped clamps, as shown in fig. 7 c.

As shown in fig. 7c, applying the pulse current field before the ultrasonic rolling step, and unloading the pulse current field after the ultrasonic rolling step can induce plastic effect, skin effect and joule heat effect in the metal workpiece 3, reduce the resistance to ultrasonic rolling deformation, and improve the plastic flow property of the surface material, thereby further improving the level and depth of the residual compressive stress of the surface layer generated by the ultrasonic rolling.

Particularly, the elastic stress field is applied before the step of applying the pulse electric current field, and the elastic stress field is unloaded after the step of unloading the pulse electric current field, so that elastic stress superposition and resultant force-resultant force moment rebalancing can be caused in the metal workpiece 3, and the level and the depth of the surface layer residual compressive stress generated by the pulse electric current field assisted ultrasonic rolling are further improved.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 7b are sequentially performed.

In one embodiment, the parameters of the steps are as follows: firstly clamping an A-7 workpiece, then applying a 150MPa elastic stress field to the A-7 workpiece, and then applying a pulse frequency of 20000Hz, a pulse width of 1 mu s, a duty ratio of 50% and a peak current density of 30A/mm to the A-7 workpiece²The pulse current field makes the A-7 workpiece rotate at the rotating speed of 200r/min, then ultrasonic rolling surface strengthening is carried out on the A-7 workpiece, the rolling condition is that the rolling head is a tungsten carbide hard alloy ball with phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feeding speed is 0.1mm/r, the workpiece rotation and axial feeding are stopped after the rolling is finished, then the pulse current field and the elastic stress field are sequentially unloaded, and finally the workpiece is taken down.

Example eight

As shown in fig. 8a, another metal material physical field assisted ultrasonic rolling surface strengthening device 8000 is shown, wherein the physical field loading systems 5 adopted are a first physical field loading system 501 and a second physical field loading system 502, the first physical field loading system 501 is an elastic stress field system 501a, and the second physical field loading system 502 is a thermal field system 502b. The workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-8.

As shown in fig. 8b, a surface strengthening method corresponding to the illustrated apparatus 8000 is illustrated, which sequentially includes seven steps of clamping a workpiece, applying a physical field, applying rotation and feed, ultrasonic rolling, stopping rotation and feed, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field comprises the steps of applying an elastic stress field and applying a thermal field in sequence; and the step of unloading the physical field comprises the steps of unloading the thermal field and unloading the elastic stress field in sequence.

the step of applying a thermal field is the same as that of the surface strengthening method in example four;

the step of unloading the thermal field is the same as the step of unloading the thermal field in the surface strengthening method in the fourth embodiment;

Particularly, the workpiece clamping step comprises: fixing annular clamps 501a-1 and 501a-2 on the two clamping devices respectively, enabling the metal workpiece 3 to pass through two groups of heating coil windings of a heater 502b-4, and then axially fixing the metal workpiece 3 between the two annular clamps;

as shown in fig. 8c, applying the thermal field before the ultrasonic rolling step and unloading the thermal field after the ultrasonic rolling step can induce heat activation and thermal expansion in the metal workpiece 3, reduce the resistance to ultrasonic rolling deformation, and improve the plastic flow characteristics of the skin material, thereby further increasing the level and depth of the skin residual compressive stress generated by the ultrasonic rolling.

In particular, the application of the elastic stress field before the step of applying the thermal field and the unloading of the elastic stress field after the step of unloading the thermal field can induce the superposition of the elastic stress and the rebalancing of the resultant force-resultant moment in the metal workpiece 3, thereby further improving the level and depth of the residual compressive stress of the surface layer generated by the thermal field assisted ultrasonic rolling.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 8b are sequentially performed.

In one embodiment, the parameters of the steps are as follows: firstly clamping an A-8 workpiece, then applying a 150MPa elastic stress field to the A-8 workpiece, then applying a thermal field to heat the workpiece to 150 ℃, then enabling the A-8 workpiece to rotate at a rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-8 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, and the axial feed rate is 0.1mm/r, stopping the rotation and axial feed of the workpiece after the rolling is finished, unloading the thermal field, restoring the temperature of the workpiece to the room temperature, then unloading the elastic stress field, and finally taking down the workpiece.

Example nine

As shown in FIG. 9a, another metal material physical field assisted ultrasonic rolling surface strengthening device 9000 is shown, wherein the physical field loading systems 5 adopted are a first physical field loading system 501 and a second physical field loading system 502, the first physical field loading system 501 is an elastic stress field system 501a, the second physical field loading system 502 is a pulsed electromagnetic field system 502c, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-9.

As shown in fig. 9b, a surface strengthening method corresponding to the illustrated apparatus 9000 is shown, sequentially for seven steps of clamping a workpiece, applying a physical field, applying rotation and feed, ultrasonic rolling, stopping rotation and feed, unloading the physical field, and removing the workpiece. The method is the same as the surface strengthening method in the first embodiment except for the following steps:

wherein the step of applying the physical field comprises the steps of applying an elastic stress field and applying a pulse electromagnetic field in sequence; and the step of unloading the physical field comprises the steps of unloading the pulse electromagnetic field and unloading the elastic stress field in sequence.

the step of applying a pulsed electromagnetic field is the same as the step of applying a pulsed electromagnetic field in the surface strengthening method in example five;

the step of unloading the elastic stress field is the same as the step of unloading the elastic stress field in the surface strengthening method in the second embodiment;

the step of unloading the pulsed electromagnetic field is the same as the step of unloading the pulsed electromagnetic field in the surface strengthening method of the fifth embodiment.

Particularly, the workpiece clamping step comprises: annular clamps 501a-1 and 501a-2 are fixed on the two clamping devices respectively, then the metal workpiece 3 axially passes through two groups of induction coils 502c-1 of the pulsed electromagnetic field loading device 502c, and two axial ends of the metal workpiece 3 are fixed between the two annular clamps;

as shown in fig. 9c, applying the pulsed electromagnetic field before the ultrasonic rolling step and unloading the pulsed electromagnetic field after the ultrasonic rolling step can induce a magnetostrictive effect in the metal workpiece 3, reduce the resistance to ultrasonic rolling deformation, and improve the plastic flow characteristics of the skin material, thereby further improving the level and depth of the residual compressive stress of the skin layer generated by the ultrasonic rolling.

Particularly, the elastic stress field is applied before the step of applying the pulse electromagnetic field, and the elastic stress field is unloaded after the step of unloading the pulse electromagnetic field, so that the elastic stress superposition and the resultant force-resultant force moment rebalancing can be caused in the metal workpiece 3, and the level and the depth of the surface layer residual compressive stress generated by the ultrasonic rolling assisted by the pulse electromagnetic field are further improved.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 9b are sequentially performed.

In one embodiment, the parameters of the steps are: firstly clamping an A-9 workpiece, then applying a 150MPa elastic stress field to the A-9 workpiece, then applying a pulse electromagnetic field with the pulse frequency of 200Hz, the pulse width of 5ms and the peak magnetic induction intensity of 3T to the A-9 workpiece, then enabling the A-9 workpiece to rotate at the rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-9 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with the diameter of 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, the axial feed rate is 0.1mm/r, stopping the rotation and the axial feed of the workpiece after the rolling is finished, then unloading the pulse electromagnetic field and the elastic stress field in sequence, and finally taking down the workpiece.

EXAMPLE ten

As shown in FIG. 10a, another metal material physical field assisted ultrasonic rolling surface strengthening device 10000 is shown, wherein the physical field loading system 5 adopted is a first physical field loading system 501 and a third physical field loading system 503, the first physical field loading system 501 is an elastic stress field system 501a, and the third physical field loading system 503 is a cryogenic field system 503a, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-10.

As shown in fig. 10b, the surface strengthening method corresponding to the illustrated apparatus 10000 is illustrated, which comprises nine steps of clamping a workpiece, applying a first physical field, applying rotation and feeding, ultrasonic rolling, applying a second physical field, unloading the second physical field, stopping rotation and feeding, unloading the first physical field, and removing the workpiece. The specific steps in this example are as follows:

s1, clamping a workpiece: both ends of the metal workpiece 3 are inserted into one ends of the first and second clamps 501a-1 and 501a-2, respectively, and fixed, and then the other ends of the first and second clamps 501a-1 and 501a-2 are clamped by jaws of the first and second clamping devices 1-15 and 1-16, respectively, as shown in fig. 2 c. In particular, after clamping, the tooth surfaces of the boss latches of the jaws must be in good contact with the cylindrical surfaces of the first and second clamps 501a-1 and 501a-2 to ensure the coaxiality of the entire device; the inner vertical surfaces of the boss latches of the jaws must be brought into good contact with the inner vertical surfaces of the cylindrical bosses at the other ends of the first and second clamps 501a-1 and 501a-2 to ensure that the hydraulic load provided by the hydraulic drive 4-1 is accurately applied to the metal workpiece 3 via the piston rod 4-2, the first headstock 1-1, the first spindle 1-3, the first clamping device 1-15, and the first clamp 501a-1, and the metal workpiece 3 is positioned on the spray intersection line of the two sets of spray heads 503 a-1.

S2, applying an elastic stress field: calculating the required oil pressure according to the cross sectional areas of the metal workpiece 3 and the piston rod 4-2 and the preset elastic stress, wherein the strength of the applied elastic stress field does not exceed the uniaxial tension proportion limit value of the material used for the metal workpiece 3; the hydraulic driving device 4-1 is started, oil pressure is adjusted through an oil pressure valve, the first spindle box 1-1, the first spindle 1-3 and the first clamping device 1-15 are driven by the piston rod 4-2 to transversely move along the slide rail of the lathe bed 1-10 in the direction far away from the second spindle box 1-2, and therefore a single-axis tensile elastic stress field with a preset size is applied to the metal workpiece 3.

S3, rotation and feeding are applied: starting the double-spindle synchronous rotating system 1, setting a rotating speed, and driving a first spindle 1-3 and a first clamping device 1-15 and a second spindle 1-4 and a second clamping device 1-16 to synchronously rotate by a spindle servo motor 1-5 through a spindle synchronous driving belt 1-6, a telescopic synchronous shaft 1-7, a first spindle synchronous driven belt 1-8 and a second spindle synchronous driven belt 1-9, so as to drive the metal workpiece 3 to rotate according to the set rotating speed; the synchronously moving bases 1-11 operate to drive the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 arranged on the second bases 1-13 to axially feed along the metal workpiece 3 at a set feeding speed and direction.

S4, ultrasonic rolling: the ultrasonic rolling head of the ultrasonic rolling system 2 is close to the metal workpiece 3 in the radial direction, and continues to perform feeding motion along the axial direction of the metal workpiece 3, so that ultrasonic rolling surface strengthening is performed on the rotating metal workpiece 3 under the assistance of an elastic stress field, and ultrasonic rolling surface strengthening is performed on the metal workpiece 3 under the assistance of a physical field.

S5, applying a cryogenic field: and starting the controller 503a-4, adjusting to a preset cryogenic medium spraying flow rate, immediately spraying cryogenic medium to the metal workpiece 3 through the tank body 503a-5, the guide pipe 503a-3 and the spray head 503a-1 fixed on the bracket 503a-2 after the ultrasonic rolling is finished, and lasting for a preset time.

S6, unloading the cryogenic cooling field: the controller 503a-4 is turned off and the injection of the cryogenic medium to the metal workpiece 3 is stopped.

S7, stopping rotation and feeding: the double-spindle synchronous rotating system 1 is closed, the rotation of the metal workpiece 3 is stopped, the feeding motion of the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 installed on the second bases 1 to 13 along the axial direction of the metal workpiece 3 is stopped, and then the ultrasonic rolling head is radially far away from the metal workpiece 3.

S8, unloading an elastic stress field: and closing the hydraulic driving device 4-1, and removing the oil pressure in the transverse moving driving system 4 to enable the metal workpiece 3 to elastically recover.

S9, taking down the workpiece: the first and second clamping devices 1 to 15 and 1 to 16 are released, whereby the metal workpiece 3 is removed and allowed to return to room temperature.

As shown in fig. 10c, the sequential application and unloading of the cryogenic field after the ultrasonic rolling step can generate a great temperature gradient drop on the surface layer of the metal workpiece 3, thereby further increasing the level and depth of the surface layer residual compressive stress generated by the ultrasonic rolling.

Particularly, an elastic stress field is applied before the ultrasonic rolling step, and the elastic stress field unloaded after the deep cooling field unloading step can cause elastic stress superposition and resultant force-resultant moment rebalancing in the metal workpiece 3, so that the level and the depth of the surface layer residual compressive stress generated by the deep cooling field assisted ultrasonic rolling are further improved.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 10b are sequentially performed.

In one embodiment, the parameters of the steps are as follows: firstly clamping an A-10 workpiece, then applying a 150MPa elastic stress field to the A-10 workpiece, then enabling the A-10 workpiece to rotate at a rotating speed of 200r/min, then carrying out ultrasonic rolling surface strengthening on the A-10 workpiece, wherein the rolling condition is that a rolling head is a tungsten carbide hard alloy ball with the diameter of phi 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, and the axial feed rate is 0.1mm/r, after the rolling is finished, the axial feed is stopped, then a cryogenic medium is sprayed to the ultrasonically rolled workpiece at the flow rate of 1L/min for 5min, then the deep cooling field is unloaded, the workpiece rotation is stopped, then the elastic stress field is unloaded, and finally the workpiece is taken down, so that the temperature of the workpiece is recovered to the room temperature.

EXAMPLE eleven

As shown in fig. 11a, another metal material physical field assisted ultrasonic rolling surface strengthening device 11000 is shown, wherein the physical field loading systems 5 adopted are a first physical field loading system 501, a second physical field loading system 502 and a third physical field loading system 503, the first physical field loading system 501 is an elastic stress field system 501a, the second physical field loading system 502 is a thermal field system 502b, the third physical field loading system 503 is a cryogenic field system 503a, and the workpiece material is in-situ TiB₂The/2024 Al composite material is numbered as A-11.

As shown in fig. 11b, a surface strengthening method corresponding to the device 11000 shown is shown with eleven steps in sequence for clamping the workpiece, applying the first physical field, applying the second physical field, applying the rotation and feed, ultrasonically rolling, unloading the second physical field, applying the third physical field, unloading the third physical field, stopping the rotation and feed, unloading the first physical field, and removing the workpiece. The specific steps in this example are as follows:

s1, clamping a workpiece: the metal workpiece 3 is passed through two sets of heating coil windings of the heater 502b-4, and both ends of the metal workpiece 3 are respectively passed through one ends of the first and second clamps 501a-1 and 501a-2 and fixed, and then the other ends of the first and second clamps 501a-1 and 501a-2 are respectively clamped by jaws of the first and second clamping devices 1-15 and 1-16, as shown in fig. 2 c. In particular, after clamping, the tooth surfaces of the boss latches of the jaws must be in good contact with the cylindrical surfaces of the first and second clamps 501a-1 and 501a-2 to ensure the coaxiality of the entire device; the inner vertical surfaces of the boss latch teeth of the clamping jaws must be in good contact with the inner vertical surfaces of the cylindrical bosses at the other ends of the first clamp 501a-1 and the second clamp 501a-2 to ensure that the hydraulic load provided by the hydraulic driving device 4-1 is accurately applied to the metal workpiece 3 through the piston rod 4-2, the first spindle box 1-1, the first spindle 1-3, the first clamping device 1-15 and the first clamp 501a-1, and the metal workpiece 3 is positioned on the spraying intersection line of the two groups of spray heads 503 a-1;

S3, applying a thermal field: the power supply 502b-1 is started, the output voltage and current of the controller 502b-3 are adjusted, and the heater 502b-4 is electrified through the bracket 502b-2 with a lead inside to heat the metal workpiece 3, as shown in fig. 4 c; the temperature of the metal workpiece 3 is monitored in real time by the temperature monitor 502b-5 and the voltage and the current output by the controller 502b-3 are fed back and adjusted, so that the middle part of the metal workpiece 3 is heated to the preset temperature. Particularly, the temperature of the middle heating part of the metal workpiece 3 needs to be monitored in real time during the heating process and fed back to the feedback regulation controller 502b-3 to regulate and control the temperature of the heating part of the metal workpiece 3 to be maintained at a specified temperature in real time, and the heating temperature of the middle part of the metal workpiece 3 does not exceed the second phase precipitation temperature of the material used for the metal workpiece 3.

S4, rotation and feeding are applied: starting the double-spindle synchronous rotating system 1, setting a rotating speed, and driving a first spindle 1-3 and a first clamping device 1-15 and a second spindle 1-4 and a second clamping device 1-16 to synchronously rotate by a spindle servo motor 1-5 through a spindle synchronous driving belt 1-6, a telescopic synchronous shaft 1-7, a first spindle synchronous driven belt 1-8 and a second spindle synchronous driven belt 1-9, so as to drive the metal workpiece 3 to rotate according to the set rotating speed; the synchronously moving bases 1-11 operate to drive the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 arranged on the second bases 1-13 to axially feed along the metal workpiece 3 at a set feeding speed and direction.

S5, ultrasonic rolling: the ultrasonic rolling head of the ultrasonic rolling system 2 is close to the metal workpiece 3 in the radial direction, and continues to perform feeding motion along the axial direction of the metal workpiece 3, so that ultrasonic rolling surface strengthening is performed on the rotating metal workpiece 3 under the assistance of an elastic stress field, and ultrasonic rolling surface strengthening is performed on the metal workpiece 3 under the assistance of a physical field.

S6, unloading the thermal field: the heater 502b-4 is turned off and the application of the thermal field to the metal workpiece 3 is stopped.

S7, applying a cryogenic field: and starting the controller 503a-4, adjusting to the preset cryogenic medium ejection flow, and immediately ejecting the cryogenic medium to the metal workpiece 3 through the tank 503a-5, the guide pipe 503a-3 and the nozzle 503a-1 fixed on the bracket 503a-2 for a preset duration after the ultrasonic rolling is finished.

S8, unloading the cryogenic cooling field: the controller 503a-4 is turned off and the injection of the cryogenic medium to the metal workpiece 3 is stopped.

S9, stopping rotation and feeding: the double-spindle synchronous rotating system 1 is closed, the rotation of the metal workpiece 3 is stopped, the feeding motion of the ultrasonic rolling system 2 and the second and/or third physical field loading devices 502 and 503 installed on the second bases 1 to 13 along the axial direction of the metal workpiece 3 is stopped, and then the ultrasonic rolling head is radially far away from the metal workpiece 3.

S10, unloading an elastic stress field: and closing the hydraulic driving device 4-1, and removing the oil pressure in the transverse moving driving system 4 to enable the metal workpiece 3 to elastically recover.

S11, taking down the workpiece: the first and second clamping devices 1 to 15 and 1 to 16 are released, whereby the metal workpiece 3 is removed and returned to room temperature. As shown in fig. 11c, applying the thermal field before the ultrasonic rolling step and unloading the thermal field after the ultrasonic rolling step can induce heat activation and thermal expansion in the metal workpiece 3, reduce the ultrasonic rolling deformation resistance, improve the plastic flow characteristics of the skin material, and further increase the level and depth of the skin residual compressive stress generated by the ultrasonic rolling.

In particular, the sequential application and unloading of the cryogenic field after the step of unloading the thermal field can generate a great temperature gradient drop on the surface layer of the metal workpiece 3, thereby further improving the level and depth of the surface layer residual compressive stress generated by the ultrasonic rolling with the assistance of the thermal field.

Particularly, the elastic stress field is applied before the step of applying the thermal field, and the elastic stress field unloaded after the step of unloading the cryogenic field can cause elastic stress superposition and resultant force-resultant moment rebalancing in the metal workpiece 3, so that the level and the depth of the surface layer residual compressive stress generated by the cryogenic field-thermal field coupling auxiliary ultrasonic rolling are further improved.

In particular, the above-described advantageous effects can be obtained only when the steps shown in fig. 11b are sequentially performed.

In one embodiment, the parameters of the steps are: clamping an A-11 workpiece, applying a 150MPa elastic stress field to the A-11 workpiece, applying a thermal field to heat the workpiece to 150 ℃, rotating the A-11 workpiece at a rotating speed of 200r/min, applying the thermal field to heat the workpiece to 150 ℃, performing ultrasonic rolling surface strengthening on the A-11 workpiece, wherein the rolling head is a tungsten carbide hard alloy ball with the diameter of 14mm, the static load pressure is 180N, the ultrasonic frequency is 28KHz, the ultrasonic amplitude is 10 mu m, and the axial feed rate is 0.1mm/r, stopping axial feed after rolling, unloading the thermal field, spraying a cryogenic medium to the ultrasonically rolled workpiece at the flow rate of 1L/min, continuing for 5min, unloading the deep cold field, stopping the rotation of the workpiece, unloading the elastic stress field, and finally taking down the workpiece to recover the temperature of the workpiece to room temperature.

Example twelve

This embodiment is substantially the same as the apparatus and the surface strengthening method described in the second embodiment, and particularly, in the step of clamping the workpiece in the surface strengthening method of the second embodiment, there are various ways of respectively penetrating and fixing both ends of the metal workpiece 3 into one end of the first clamp 501a-1 and one end of the second clamp 501a-2, such as screwing, snapping, and the like. In particular, another metal workpiece 3-a and another elastic stress field system 501a-a are provided on the basis of the apparatus 2000, and a new way of fixing the metal workpiece 3-a on the elastic stress field system 501a-a is shown in fig. 12 a.

Wherein, one end of the metal workpiece 3-a is provided with a single pin hole, and the other end is provided with two pin holes; the coaxiality of the metal workpiece within the full-length range of 3-a is less than or equal to 0.01.

The elastic stress field system 501a-a comprises a first clamp 501a-a-1, a second clamp 501a-a-2, a limiting block 501a-a-3, a first tensile force threaded pin 501a-a-4, a second tensile force threaded pin 501a-a-5, a limiting threaded pin 501a-a-6 and a nut 501a-a-7. The diameters of the hollow parts of the first clamp 501a-a-1 and the second clamp 501a-a-2 are in clearance fit with the diameters of the two ends of the metal workpiece 3-a, the maximum clearance is less than or equal to 0.05mm, and the minimum clearance is greater than or equal to 0mm; a group of pin holes are formed in the first clamp 501a-a-1, the positions of the pin holes correspond to a single pin hole at one end of the metal workpiece 3-a, the size of the pin holes is the same as that of the single pin hole at one end of the metal workpiece 3-a, a first tension threaded pin 501a-a-4 is inserted into the pin holes, the first tension threaded pin 501a-a-4 is in clearance fit with the pin holes, the maximum clearance is less than or equal to 0.05mm, and the minimum clearance is greater than or equal to 0mm; the stop block 501a-a-3 may be inserted into a groove on the second clamp 501 a-a-2; the whole body formed by the limiting block 501a-a-3 and the second clamp 501a-a-2 is provided with two groups of pin holes, wherein the first group of pin holes completely passes through the second clamp 501a-a-2, and the second group of pin holes respectively pass through the second clamp 501a-a-2 and the limiting block 501a-a-3; the positions of the two groups of pin holes respectively correspond to the two pin holes at the other end of the metal workpiece 3-a, and the sizes of the two groups of pin holes are the same as the sizes of the two pin holes at the other end of the metal workpiece 3-a; a second tension threaded pin 501a-a-5 is inserted into the first group of pin holes, the second tension threaded pin 501a-a-5 keeps clearance fit with the first group of pin holes, the maximum clearance is less than or equal to 0.05mm, and the minimum clearance is greater than or equal to 0mm; a limiting threaded pin 501a-a-6 is inserted into the second group of pin holes, the limiting threaded pin 501a-a-6 is in clearance fit with the second group of pin holes, the maximum clearance is less than or equal to 0.05mm, and the minimum clearance is greater than or equal to 0mm; nuts 501a-a-7 are screwed at the end parts of the first pulling force threaded pin 501a-a-4, the second pulling force threaded pin 501a-a-5 and the limiting threaded pin 501a-a-6 respectively.

Compared with the fixing modes such as threaded connection, buckle connection and the like, the new fixing mode of the metal workpiece 3-a on the elastic stress field system 501a-a can ensure that the whole body formed by the metal workpiece 3-a, the elastic stress field system 501a-a and the double-spindle synchronous rotating system 1 has better coaxiality; furthermore, the clamping and the dismounting of the metal workpiece 3-a can be simpler and more convenient, and the first spindle box 1-1 does not need to be moved back and forth through the transverse moving driving system 4; furthermore, the stability of the elastic stress field can be improved because the metal workpiece 3-a is in close contact with the small gaps in the hollow parts of the first clamp 501a-a-1 and the second clamp 501a-a-2, and the first tension threaded pin 501a-a-4, the second tension threaded pin 501a-a-5 and the limit threaded pin 501a-a-6 are in close contact with the small gaps in the pin holes of the first clamp 501a-a-1, the second clamp 501a-a-2 and the limit block 501 a-a-3.

Comparative example

For comparison, common ultrasonic rolling surface strengthening is carried out, and the used material and rolling conditions are completely consistent with those of the workpieces from A-2 to A-11, and the number of the workpieces is B-1. The distribution of residual stress on the surface layer of the workpiece in all the embodiments along the depth direction vertical to the surface of the material is measured by using an X-ray stress gauge, an electrolytic polishing machine and a high-precision laser displacement sensor. The electrolytic polishing machine is used for stripping the influence layer, the high-precision laser displacement sensor is used for measuring the depth of the stripped influence layer, and the X-ray stress meter is used for measuring the residual stress value of each influence layer. The residual stress measurements are shown in fig. 13a-13e, respectively.

The surface residual compressive stress level, the peak residual compressive stress level and the depth of the influence layer of the residual compressive stress of the physical field assisted ultrasonic rolling workpieces in the second to the eleventh embodiments are obviously higher than the indexes of the conventional ultrasonic rolling workpieces in the comparative embodiments. The measurement result shows that compared with the common ultrasonic rolling, the physical field auxiliary ultrasonic rolling can comprehensively improve the residual compressive stress level, the peak value residual compressive stress level and the residual compressive stress influence layer depth of the surface of the metal material, remarkably optimize the residual compressive stress distribution of the surface layer and effectively improve the fatigue performance of the workpiece.

In summary, the device and method for reinforcing the surface of the metal material by ultrasonic rolling assisted by the physical field provided in the embodiments of the present invention have the advantages of simple structure, low cost for use and maintenance, and convenient operation of the related methods, and have practical value in mechanical surface reinforcement and fatigue performance improvement of the metal material.

The above description is of the preferred embodiment of the invention. It is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments to equivalent variations, without departing from the spirit of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A surface enhancing apparatus for applying a pulsed current field to a metal workpiece and assisting ultrasonic rolling, the metal workpiece (3) being a cylindrical workpiece, the surface enhancing apparatus comprising:

the double-spindle synchronous rotating system (1) comprises two spindle boxes which are symmetrically arranged and a synchronous moving base (1-11) positioned between the two spindle boxes, output shafts of the two spindle boxes are connected with the same telescopic synchronous shaft (1-7) through a synchronous belt, clamping devices are respectively configured at the opposite ends of the two output shafts, and metal workpieces (3) of which the two ends are sleeved with insulating sleeves are fixed between the two clamping devices so as to enable the metal workpieces (3) to be mutually insulated from the clamping devices;

the ultrasonic rolling system (2) is arranged on the synchronous motion base (1-11) and is positioned on one side of the metal workpiece (3), the synchronous motion base (1-11) is used for driving the ultrasonic rolling system (2) to make feeding motion along the axial direction of the metal workpiece (3), and the ultrasonic rolling system (2) comprises an ultrasonic rolling head which can be radially close to/far away from the metal workpiece (3);

the device comprises a pulse current field loading device (502 a) which is arranged on a synchronous motion base (1-11) and is positioned on the other side of a metal workpiece (3), wherein the pulse current field loading device (502 a) is provided with an upper electrode and a lower electrode which are symmetrically arranged, the ends of the two electrodes are respectively and radially abutted against the upper side and the lower side of the outer diameter of the metal workpiece (3), the two electrodes and an ultrasonic rolling head are positioned in the same circumferential plane which takes the axis of the metal workpiece (3) as the center of a circle, pulse current is supplied to the metal workpiece (3) through the two electrodes to reduce the ultrasonic rolling deformation resistance, the synchronous motion base (1-11) is used for simultaneously driving an ultrasonic rolling system (2) and the electrodes to axially feed along the metal workpiece (3) according to a set feeding speed and direction, the pulse current field loading device (502 a) is provided with an arc-shaped support (502 a-3), the arc-shaped support (502 a-3) is provided with an arc-shaped sliding chute, two insulating sliding sleeves are arranged on the arc-shaped sliding chute, the two electrodes are respectively arranged on the two insulating sliding sleeves, one end of each electrode passes through the insulating sliding sleeve and is radially abutted against the outer diameter of the metal workpiece (3), and the other end of the metal workpiece is connected with a pulse power supply (502 a) through an enameled wire (5);

by applying the pulse current field before the ultrasonic rolling step and unloading the pulse current field after the ultrasonic rolling step, plastic effect, skin effect and Joule heat effect can be caused in the metal workpiece, the resistance to ultrasonic rolling deformation is reduced, and the plastic flow characteristic of the surface layer material is improved, so that the level and depth of the surface layer residual compressive stress generated by ultrasonic rolling are further improved.

2. A surface-enhancing apparatus as claimed in claim 1, wherein a spindle servo motor (1-5) for driving the telescopic synchronizing shafts (1-7) in rotation is fixed to the first headstock (1-1).

3. The surface enhancing apparatus of claim 1, wherein the enhancing apparatus further comprises: the horizontal moving driving system (4) is used for driving the first spindle box (1-1) to horizontally move away from the second spindle box (1-2), the horizontal moving driving system (4) is provided with a set of horizontal driving device connected with the first spindle box (1-1), the horizontal driving device comprises a hydraulic driving device (4-1) and a piston rod (4-2), an oil pressure valve is installed on the hydraulic driving device (4-1), and the hydraulic driving device (4-1) is connected with the first spindle box (1-1) through the piston rod (4-2);

the two main spindle boxes are both arranged on a slide rail of the lathe bed (1-10).

4. A surface enhancing apparatus as claimed in claim 1, wherein a second base (1-13) is mounted on the base (1-11) for synchronous motion, and the arc-shaped support (502 a-3) is mounted on the second base (1-13) by a link.

5. The surface-strengthening device of claim 1, wherein the ultrasonic rolling head is close to/away from the metal workpiece (3) in a radial direction of the metal workpiece (3).

6. A method for surface-strengthening a metal workpiece using the surface-strengthening apparatus of any one of claims 1 to 5, comprising the steps of:

s1, fixing two axial ends of a metal workpiece (3) between two coaxial clamping devices, and sleeving insulating sleeves at the two axial ends of the metal workpiece (3) to insulate the clamping devices from each other;

s2, respectively and radially abutting the ends of two electrodes for loading a pulse current field against the upper side and the lower side of the outer diameter of the metal workpiece (3), and switching on a pulse power supply to apply the pulse current field to the metal workpiece (3);

s3, starting the double-spindle synchronous rotating system (1), enabling the two clamping devices to rotate synchronously to drive the metal workpiece (3) to rotate according to a set rotating speed and a set rotating direction, and enabling the synchronous moving base (1-11) to operate to drive the electrodes of the ultrasonic rolling system (2) and the pulse current field loading device (502 a) to axially feed along the metal workpiece (3) according to a set feeding speed and a set feeding direction;

s4, starting the ultrasonic rolling system (2), wherein an ultrasonic rolling head of the ultrasonic rolling system (2) is close to the metal workpiece (3) in the radial direction, and continues to perform feeding motion along the axial direction of the metal workpiece (3) to perform ultrasonic rolling surface strengthening under the assistance of a pulse current field on the rotating metal workpiece (3);

s5, after the ultrasonic rolling is finished, closing the double-spindle synchronous rotating system (1), stopping the rotation of the metal workpiece (3), stopping the feeding motion of the ultrasonic rolling system (2) and the pulse current field loading device (502 a) along the axial direction of the metal workpiece (3), and then enabling the ultrasonic rolling head to be far away from the metal workpiece (3) in the radial direction;

s6, closing the pulse power supply, stopping applying the pulse current field to the metal workpiece (3), generating plastic effect, skin effect and Joule heat effect in the metal workpiece by applying the pulse current field before the ultrasonic rolling step and unloading the pulse current field after the ultrasonic rolling step, reducing the resistance of ultrasonic rolling deformation, and improving the plastic flow characteristic of the surface layer material, thereby further improving the level and depth of the surface layer residual compressive stress generated by the ultrasonic rolling;

s7, loosening the two clamping devices and taking down the metal workpiece (3).