WO2018120359A1

WO2018120359A1 - Method and device for follow-up-type laser shock peening treatment

Info

Publication number: WO2018120359A1
Application number: PCT/CN2017/073490
Authority: WO
Inventors: 张文武; 茹浩磊; 黄亿辉; 王斌
Original assignee: 宁波大艾激光科技有限公司; 中国科学院宁波材料技术与工程研究所
Priority date: 2016-12-30
Filing date: 2017-02-14
Publication date: 2018-07-05
Also published as: CN108262563B; CN108262563A

Abstract

Disclosed are a device and method for follow-up-type laser shocking peening with a coaxial laser and light, same using follow-up-type absorption belt conveying. By means of water of a certain pressure sprayed from a water spray device, an absorption belt is attached to a workpiece, and following the rotation of an electric motor, the absorption belt is conveyed while a laser shock peening treatment is carried out, thus, a laser shock peening treatment process for a surface of the workpiece can be completed. The device comprises a laser input unit, a focusing unit, a protection lens, a belt-conveying unit, and a spray head unit.

Description

Follow-up laser shock strengthening processing device and method

Technical field

The invention belongs to the field of material processing, and relates to a laser shock strengthening technology, in particular to a novel laser shock strengthening processing device.

Background technique

Laser Shocking Peening (LSP) is a pulsed laser impact material with high energy density and short pulse width. It generates plasma on the surface of the material, which generates a GPA-level shock wave to act on the surface of the material and propagate to the inside to make the surface of the material. Plastic deformation and dislocation structure occur in a certain area, forming residual compressive stress, thereby improving the fatigue strength and corrosion resistance of the part. At present, laser shock peening technology has been widely used in aviation, shipbuilding, mechanical engineering and other fields, especially for anti-fatigue treatment of aircraft engine blades.

As shown in FIGS. 1 and 2, the conventional laser shock absorbing processing apparatus includes a laser generating unit, an absorbing protective layer on the surface of the workpiece, and a constraining layer on the surface of the absorbing protective layer. The function of the constraining layer is to allow the laser energy to pass through and act on the absorbing protective layer while improving the shock wave coupling efficiency. At present, a solid material such as optical glass is generally used as a constraining layer, or a flexible material such as a water film is used as a transparent constraining layer. The main function of the absorbing protective layer is to protect the workpiece from laser burns and enhance the absorption of laser energy. At present, special black lacquer, flexible tape or metal foil of a certain thickness is generally used as an absorbing protective layer.

Conventional laser shock peening treatment uses side water spray to form a water film constraining layer which is seriously affected by the edge or convex structure, and it is difficult to form a stable constraining layer. At the same time, the conventional laser impact strengthening treatment usually adopts the form of metal foil, black tape or special black paint on the surface of the workpiece. The advantage of applying black lacquer is that it has good adhesion to various irregular curved surfaces. The disadvantage is that it needs to wait for drying after spraying, and then the restraining layer can be applied for impact strengthening treatment, and the production efficiency is low; if aluminum foil is used, The adhesion to chamfers and irregular surfaces is not good, which affects the quality of reinforcement. After the workpiece is processed, it is necessary to find a way to remove the black paint on the surface of the workpiece (see Figure 2a), the tape (see Figure 2b) or the foil (see Figure 2c). It is time-consuming and laborious, and it is difficult to achieve large-scale, high-efficiency production applications, hindering the industry. Process.

In addition, a water-soluble paint is used, and after the spray coating (pre-treatment), the impact strengthening treatment can be performed without drying, and after the treatment, the coating is removed using high-pressure water (post-treatment), and there are problems such as insufficient processing efficiency and water pollution. In summary, although the laser impact strengthening treatment process is outstanding, the current processing technology generally requires pre-processing, post-processing, multiple processing and personalized customization processes, which are inefficient and costly, so it is necessary to develop a more efficient process. Enhanced treatment process.

Summary of the invention

According to an aspect of the present application, a light-water coaxial follow-up laser shock tensor device is provided, which adopts a follow-up absorption belt conveying method, and a certain pressure of water is sprayed through a water spray device to absorb the absorption belt. Close to the workpiece, as the motor rotates, the laser impact strengthening process simultaneously conveys the absorption band, and the laser shock strengthening process for the workpiece surface can be completed. Since the absorption belt used in the invention is not attached to the surface of the workpiece, and the surface after processing is smooth and free from dirt, the laser shock strengthening treatment process can be completed without pre-treatment, and the problem of water film instability can be solved, and the efficiency can be high. Laser shock reinforced treatment is performed.

The device includes a protective mirror, a belt feeding unit and a nozzle unit;

The tape feeding unit includes a motor and an absorption belt, and the motor drives the absorption belt to move through a transmission mechanism, and the absorption belt passes through a water column ejected by the water spray unit.

Preferably, the follow-up laser shock peening device comprises a laser input unit and a focusing unit; one end of the laser input unit is connected and introduced to the light source, and the other end is connected to the focusing unit and the optical path is connected; the focusing unit The other end is connected to the water spray unit.

Preferably, the water spray unit comprises a protective lens, a water inlet nozzle and a spray head.

Preferably, the motor is a synchronous motor, and a step frequency of the synchronous motor is harmonized with an impact-enhanced working frequency of the follow-up laser shock peening device. Each time the device performs a laser pulse, the synchronous motor drives the absorption belt to move a distance or the belt continues to move at a high speed. The distance that the absorption belt moves by each impact can be determined by those skilled in the art according to the processing requirements of the workpiece to be processed and the laser spot size.

Preferably, the tape feeding unit comprises an absorption belt fixing structure fixedly connected to a water spray outlet of the water spray unit, and the absorption belt fixing structure fixes a moving direction of the absorption belt at The water column is sprayed out of the center of the water column. Further preferably, the absorption belt fixing structure is a part of the nozzle water outlet of the water spray unit. As a concrete reality According to the embodiment, the absorption belt fixing structure is an absorption belt restraining structure of the nozzle water outlet portion of the water spray unit. Further specifically, the absorption belt fixing structure is a gap forming structure of the two slits disposed opposite to the side wall of the nozzle outlet portion of the water spray unit. The absorption belt penetrates from one of the slits and passes through the water column ejected by the water spray unit and then passes out from the other slit.

Preferably, the nozzle water outlet end portion is provided with a protruding structure to form a fixing structure of the absorption belt in a position limiting manner; the absorption belt fixing structure fixes the moving direction of the absorption belt to the water spray unit. The center of the water column. Please refer to Figure 6.

The absorption belt can be selected from a smooth soft film strip which is dark in color, does not contain an adhesive layer, and is not easily broken.

Preferably, the absorbent tape has a thickness of from 0.01 mm to 0.5 mm of flexible film tape.

As a preferred embodiment, the absorbent strip has a thickness of 0.1 mm.

As an embodiment of the present application, the absorption band has an absorption rate of laser light of at least one of 10640 nm, 1064 nm, 800 nm, 532 nm, 517 nm, and 355 nm of not less than 95%.

As an embodiment of the present application, the absorption band has an absorption rate of laser light having a wavelength of 355 nm to 10640 nm of not less than 95%.

As an embodiment of the present application, the absorption band has an absorption rate of 95% to 99.99% for laser light of at least one of 10640 nm, 1064 nm, 800 nm, 532 nm, 517 nm, and 355 nm.

Preferably, the absorbent tape has a tensile strength greater than 30 N/cm.

Further preferably, the absorption band has a tensile strength ranging from 30 N/cm to 3000 N/cm.

Still more preferably, the absorbent tape has a tensile strength ranging from 30 N/cm to 300 N/cm and a thickness of from 0.01 mm to 0.5 mm.

Preferably, the surface of the absorbent belt is free of an adhesive layer.

Preferably, the transmission mechanism includes at least one delivery wheel and at least one tensioning wheel.

Further preferably, the delivery wheel or tensioner can be a fixed wheel, a moving wheel or other form of smooth structure.

Preferably, the focusing unit may be a knob mode, and the rotary motion is converted into an up-and-down linear motion by a bevel gear mechanism, a cam mechanism or the like, thereby ensuring precise fine adjustment of the focusing mirror.

Preferably, the impact head can be set thin and long without affecting the processing quality, and can be subjected to surface strengthening treatment at a concealed portion that cannot be reached by conventional laser impact processing.

Preferably, the water spray unit comprises a spray head, and the water outlet end side wall of the spray head has opposite slits or protrusions on both sides of the end to form an absorption belt limit fixing structure, and the absorption belt passes through one of the slits. And passing through the water column ejected by the water spray unit and passing through the other slit; the absorption belt fixing structure fixes the moving direction of the absorption belt to the center of the water column ejected by the water spray unit.

Preferably, the water spray unit comprises a spray head, and the water outlet end of the spray head is provided with a protruding structure to form a fixing structure of the absorption belt in a position limiting manner; the absorption belt fixing structure fixes the moving direction of the absorption belt In the center of the water column ejected by the water spray unit.

In the present application, the absorption belt fixing structure fixes the moving direction of the absorption belt to the center of the water column sprayed by the water spray unit, which means that the laser spot and the central axis of the coaxial water column can be directed to the absorption band. Central.

Preferably, the water spray unit comprises a protective lens, a water spray sleeve, a water inlet nozzle, and a spray head;

One end of the water spray sleeve is fixed with the protective lens and connected to the light exiting direction of the focusing mirror, and the other end of the water spray sleeve is connected with the spray head; the protective lens connects the water spray unit with The space of the focusing mirror is separated;

The water inlet pipe is disposed on a side wall of the water spray sleeve.

Preferably, the impact water spray has the following effects: (1) the absorption layer is closely attached to the surface of the workpiece by the water spray pressure; (2) can act as a constraining layer, can restrain the expansion of the plasma, and increase the peak value of the shock wave and the number of times of action; (3) It can remove dirt on the surface of the workpiece.

Further preferably, the distance from the water jet end face to the surface of the workpiece before impact machining should be greater than or equal to 0.1 mm. The flexible film is not broken by the increase of frictional resistance. Still more preferably, the distance from the impact spray end face to the surface of the workpiece before impact machining should be from 0.1 mm to 0.5 mm.

Preferably, the laser shock enhancement processing method has the following three methods:

(1) Laser impact head activity, surface processing of fixed workpieces;

(2) The laser impact head is fixed, and the workpiece is subjected to surface processing;

(3) Both the laser impact head and the workpiece are active.

According to an aspect of the present application, a light-water coaxial follow-up laser shock peening is provided The treatment method adopts a follow-up absorption belt conveying mode, and a certain pressure of water is sprayed through the water spraying device, and the absorption belt is closely attached to the workpiece. As the motor rotates, the laser impact strengthening treatment simultaneously conveys the absorption belt, that is, A laser shock reinforced process for the surface of the workpiece can be completed. Since the absorption belt used in the invention is not attached to the surface of the workpiece, and the surface after processing is smooth and free from dirt, the laser shock strengthening treatment process can be completed without pre-treatment, and the problem of water film instability can be solved, and the efficiency can be high. Laser shock reinforced treatment is performed. The method adopts the device described in any of the above, and the operation steps are as follows:

a) water enters the water spray unit to form a water chamber, and is sprayed from the bottom of the spray head of the water spray unit, and the absorption belt is in close contact with the surface of the workpiece under the impact pressure of the water column;

b) the laser beam is coaxially passed through the water chamber in the water spray unit and the water column sprayed from the spray head to the absorption belt which is close to the surface of the workpiece in step a), and is subjected to laser shock reinforcement;

c) the device moves relative to the workpiece to the next impact site, while the motor drives the absorption band to move beyond the laser spot, repeating the laser shock enhancement process of step b).

Preferably, the distance between the bottom of the nozzle of the device of step a) and the surface of the workpiece is greater than or equal to 0.1 mm.

Preferably, the laser beam in the step b) is a pulsed laser having a pulse width of less than 100 nanoseconds and a power density of more than 1 GW/cm ² .

Further preferably, the wavelength of the pulsed laser in the step b) is 10640 nm, 1064 nm, 800 nm, 532 nm, 517 nm and/or 355 nm.

Preferably, the manner in which the device moves relative to the workpiece in the step c) is selected from at least one of the following three ways:

(1) the device is active, the workpiece is fixed to achieve relative movement;

(2) the device is fixed, and the workpiece is moved to achieve relative movement;

(3) Both the device and the workpiece are movable to achieve relative movement.

The utility model has the beneficial effects that the provided photo-water coaxial follow-up laser shock tensing device adopts a follow-up smooth soft film strip, which can be subjected to impact treatment and side belting, and can complete the laser without cumbersome pre- and post-processing. The impact strengthening treatment process has the advantage of efficiently performing laser shock peening treatment, and can arbitrarily set the overlap ratio of the impact strengthening treatment of the workpiece in one motion.

DRAWINGS

Figure 1 is a schematic view of a conventional laser shock reinforced processing method.

Figure 2 is a flow chart of a conventional laser shock treatment process.

FIG. 3 is a schematic diagram of a follow-up laser shock strengthening treatment method in an embodiment of the present application.

4 is a flow chart of a follow-up laser shock treatment process in an embodiment of the present application.

FIG. 5 is a schematic view showing a state before the follow-up laser shock enhancement in an embodiment of the present application.

FIG. 6 is a schematic diagram of a follow-up laser shock strengthening process in an embodiment of the present application.

Figure 7 is a cross-sectional view showing an arrangement of a follower type of absorbent belt in an embodiment of the present application.

Figure 8 is a cross-sectional view showing an arrangement of a follower type of absorbent belt in an embodiment of the present application.

Figure 9 is a three-dimensional schematic view of an arrangement of a follower type of absorbent belt in an embodiment of the present application.

FIG. 10 is a schematic diagram of a follow-up laser shock enhanced moving mode in an embodiment of the present application.

Figure 11 is an embodiment of the present invention in which the absorption belt and the workpiece relative movement and impact overlap ratio.

detailed description

The present application is described in detail below with reference to the embodiments, but the application is not limited to the embodiments.

As shown in FIG. 3 to FIG. 8 , when the follow-up laser shock absorbing device of the present application is operated, the laser shock absorbing device passes a short laser pulse (pulse width of 50 nanoseconds) and a 532 nm pulse laser with a power density of ² GW/cm ² . A transparent constraining layer (this application is water) acts on the absorbent strip on the surface of the workpiece. The absorption band absorbs the laser energy and rapidly vaporizes to form a dense high-temperature, high-pressure plasma. The plasma expands rapidly and forms a shock wave. The shock wave intensity can reach several GPa (10 ⁹ Pa) levels, which is much higher than the yield of many workpiece materials. Strength; the shock wave passes through the absorption protective layer, acts on the surface of the workpiece and propagates to the inside of the workpiece, causing plastic deformation and residual compressive stress field of the workpiece, increasing dislocation density, grain refinement, and increasing hardness, thereby significantly improving the material. Anti-fatigue, anti-wear and anti-corrosion properties.

Specifically, when the follow-up laser shock peening apparatus of the present application operates, as shown in FIG. 3, the apparatus includes a protective mirror, a belt feeding unit, and a head unit. The water enters the water spray sleeve from the inlet pipe to form a water chamber, and is ejected from the outlet at the bottom of the water nozzle. The laser beam is irradiated on the focusing mirror via the optical path input module, and the beam is focused by the focusing mirror, and is coaxially directed to the water jet sleeve through the protective lens. The water chamber formed in the cylinder and the water column ejected from the nozzle are directed to the follower absorbing layer at the bottom.

Please continue to refer to Figure 3, the water spray unit includes a protective mirror, a water inlet nozzle and a spray head. The upper end of the nozzle is fixed with a protective mirror and is connected to the focusing unit, and the light exiting direction passes through the protective mirror, and the protective mirror separates the space of the upper optical path shown in FIG. 3 from the space of the lower water chamber portion. A water inlet pipe is provided on the side wall of the water spray for connecting the water source.

As shown in FIG. 5, the side wall of the nozzle end of the follow-up laser shock reinforced device of the present application has two slits disposed opposite to each other, forming an absorption belt fixing structure of the belt feeding unit, and an enlarged view is shown in FIGS. 7 and 8. In Fig. 7, the water outlet end of the nozzle is provided with a protruding structure to form a fixing structure of the absorption belt in a position limiting manner; and the absorption belt fixing structure fixes the moving direction of the absorption belt in the center of the water column ejected by the nozzle. In Figure 8, the absorption band penetrates from one of the slits at the two ends of the nozzle bottom and passes through the water column ejected from the nozzle and then passes out from the other slit, so that the absorption band can only move one-dimensional along the path defined by the slit, so the absorption band The fixed structure can keep the center of the water column sprayed from the nozzle at the time of the movement of the absorption belt, and the three-dimensional schematic view is shown in FIG.

Please refer to FIG. 5 , which is an initial state of the follow-up laser shock tensing device of the present application. After the input pulsed laser beam is focused by the focusing mirror, the protective lens is coaxially directed to the water chamber and the nozzle formed in the water spray sleeve. The ejected water column is directed to the follower absorbing layer at the bottom. The distance between the bottom of the nozzle and the surface of the workpiece is greater than or equal to 0.1 mm to avoid collision, and to avoid unnecessary pulling force caused by the absorption friction of the absorption belt, which may affect or even break the laser shock strengthening process. In the working state, when the nozzle is sprayed with water, the water pressure can adhere the absorption belt to the surface of the workpiece, as shown in Fig. 6.

The absorbent tape may be selected from the group consisting of aluminum foil tapes and other metal foil tapes, and may also be selected from darker organic polymer tapes, and may also be provided with a smoother soft film tape that is darker in color, has no adhesive layer, and is not easily broken. In the present application, a 0.1 mm black tape (non-adhesive layer) is selected as the absorption band, the absorption band tensile strength is 35 N/cm, the absorption rate to the 532 nm laser is greater than 98%, and the width of the absorption band does not exceed the outer diameter of the nozzle. It can pass through the gap on the nozzle (absorption belt fixing structure).

The laser shock strengthening operation steps of the follow-up laser shock tensing device of the present application are as follows:

a) water enters the water spray unit to form a water chamber, and the bottom of the spray head of the water spray unit is sprayed, and the absorption belt is in close contact with the surface of the workpiece under the impact pressure of the water column;

The stepping frequency of the synchronous motor is harmonized with the pulsed laser shock to strengthen the working frequency, and the pulse laser shock is applied once, and the synchronous motor pulls the absorption belt forward for a period of time to ensure continuous impact without breakdown, as shown in FIG. 4 .

As shown in FIG. 10, by adjusting the absorption band V _B and the workpiece V _W speed, it is possible to perform laser stroke strengthening processing (LSP) of an arbitrary overlap rate in one stroke, and it is possible to conveniently perform uniform or divergent LSP on the workpiece. For example, in the case where the impact frequency and the absorption band V _{B are} constant, the workpiece V _{W is} slowed down to increase the overlap ratio of the laser shock strengthening treatment, as shown in FIG. 11 , the impact regions of the top three rows of FIG. 11 are respectively The workpiece V _{W is} sequentially slowed down to meet the needs of different workpiece LSP overlap rates.

Figure 10 shows the way the device is fixed and the workpiece is moved to achieve relative movement. It is also possible to use device activity and the workpiece is fixed to achieve relative movement to obtain V _W . It is also possible to use both the device and the workpiece to achieve relative movement to obtain V _W .

In the specific embodiment of the present application, the thickness of the absorption band is selected from 0.01 mm and 0.5 mm, respectively, and the laser impact strengthening treatment is performed, and the laser impact strengthening effect on the workpiece can be achieved.

In the specific embodiment of the present application, pulsed lasers of 10640 nm, 1064 nm, 800 nm, 517 nm, and 355 nm are respectively selected for laser shock peening, and an effective laser shock strengthening effect on the workpiece can be achieved.

The technical solution of the present application reduces the parameter fluctuation caused by the application mode of the existing water confinement layer by means of light water coaxiality, and improves the stability and flexibility of the processing. Finally, the kinetic energy of the water is used to enhance the adhesion of the absorbing layer. Through the above three aspects, the effect of laser shock enhancement is improved, and the difficulty of implementing automation and factory production is reduced. The technical solution of the present application can achieve edge impact treatment and sidewalking by adopting a follow-up smooth color film layer with a darker color, no adhesive layer and no tearing, since the absorption layer is not attached to the surface of the workpiece. After treatment, the surface is smooth and free of dirt, so the laser shock strengthening process can be completed without pre-treatment.

The above description is only a few examples of the present application, and is not intended to limit the scope of the application. However, the present application is disclosed in the preferred embodiments, but is not intended to limit the application, any person skilled in the art, It is within the scope of the technical solution to make a slight change or modification with the technical content disclosed above, which is equivalent to the equivalent embodiment, without departing from the technical scope of the present application.

Claims

A light-water coaxial follow-up laser shock reinforced device, characterized in that the device comprises a protective mirror, a belt feeding unit and a water spraying unit;

The tape feeding unit includes a motor, a transmission mechanism and an absorption belt, and the motor drives the absorption belt to move through a transmission mechanism, and the absorption belt passes through a water column sprayed by the water spray unit.
The follow-up laser shock peening apparatus according to claim 1, wherein the motor is a synchronous motor, and a step frequency of the synchronous motor is consistent with an impact strengthening working frequency of the follow-up laser shock tensing device. .
The follow-up laser shock reinforced device according to claim 1, wherein the tape feeding unit comprises an absorbing belt fixing structure, and the absorbing belt fixing structure is fixedly connected to a water spray outlet of the head unit. The absorption belt fixing structure fixes the moving direction of the absorption belt to the center of the water column sprayed by the water spray module.
A follow-up laser shock peening apparatus according to claim 1, wherein said absorption belt has a thickness of from 0.01 mm to 0.5 mm.
The follow-up laser shock peening apparatus according to claim 1, wherein the absorption band has an absorption rate of at least 95% for laser light of at least one of 10640 nm, 1064 nm, 800 nm, 532 nm, 517 nm, and 355 nm. The absorption band tensile strength is greater than 30 N/cm.
The follow-up laser shock reinforced device according to claim 1, wherein the water spray unit comprises a spray head, and the water outlet end side wall of the spray head has two slits disposed opposite to form an absorption belt fixing structure; The absorption band passes through one of the slits and passes through the water column ejected by the water spray module, and then passes out from the other slit; the absorption band fixing structure fixes the moving direction of the absorption band to the water spray module The center of the water column that is ejected;

or

The water spray unit includes a spray head, and the water outlet end of the spray head is provided with a protruding structure to form a fixing structure of the absorption belt in a position limiting manner; the absorption belt fixing structure fixes the moving direction of the absorption belt to the The center of the water column sprayed by the water spray unit.
A light-water coaxial follow-up laser shock tensification processing method, characterized in that the follow-up laser shock reinforced device according to any one of claims 1 to 6 is used for laser shock reinforced operation The steps are as follows:

a) water enters the water spray unit to form a water chamber, and the bottom of the spray head of the water spray unit is sprayed, and the absorption belt is in close contact with the surface of the workpiece under the impact pressure of the water column;

b) the laser beam is coaxially passed through the water chamber in the water spray unit and the water column sprayed from the spray head to the absorption belt which is close to the surface of the workpiece in step a), and is subjected to laser shock reinforcement;

c) the device moves relative to the workpiece to the next impact site, while the motor drives the absorption band to move beyond the laser spot, repeating the laser shock enhancement process of step b).
The method of claim 7 wherein said step a) is at a distance of 0.1 mm from the bottom of said nozzle to said workpiece surface.
The method according to claim 7, wherein the laser beam in the step b) is a pulsed laser having a pulse width of less than 100 nanoseconds and a power density of more than 1 GW/cm 2 , and the wavelength of the pulsed laser is 10640 nm and 1064 nm. , 800 nm, 532 nm, 517 nm, and/or 355 nm.
The method of claim 7 wherein said means for moving relative to said workpiece in said step c) is selected from at least one of the following three ways:

(1) the device is active, the workpiece is fixed to achieve relative movement;

(2) the device is fixed, and the workpiece is moved to achieve relative movement;

(3) Both the device and the workpiece are movable to achieve relative movement.