Method and device for increasing laser-induced shock wave pressure

Patent metadata

Field	Value
Publication number	US-10745776-B2
Application number	US-201515752444-A
Country	US
Kind code	B2
Filing date	Sep 7, 2015
Priority date	Aug 13, 2015
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

A method and a device for increasing a laser induced shock wave pressure. According to the method, plasmas ( 21 ) are generated by impinging an aluminium foil ( 20 ) using lasers; a high-voltage pulse electrode ( 22 ) discharges to the plasmas ( 21 ) to induce and form a photoelectric combined energy field and then high-temperature plasmas ( 21 ) having the characteristics of an ultra-high density and an ultra-high speed expansion are induced and generated; a surface to be processed is impacted by the high-temperature plasmas ( 21 ) in a restrained state; the laser induced shock wave pressure is increased substantially; the surface of a high-strength material is reinforced, and the strength, hardness, abrasion resistance and anti-fatigue performances of the high-strength material are improved. The device comprises a laser, the electrode ( 22 ), a high-voltage power supply ( 4 ), a discharging medium ( 12 ), a moving platform, etc.

First claim

The invention claimed is:

1. A method for increasing laser-induced shock wave pressure, the method comprising:
using a laser to induce aluminum foil to generate plasma;
pulse electrodes discharging to the plasma to induce and form a photoelectric composite energy field, thereby inducing and generating the plasma, wherein the plasma is a high-temperature plasma; and
the plasma in a restrained state impacting a surface to be processed, increasing the laser induced shock wave pressure, strengthening the surface of high-strength materials and improving strength, hardness, abrasion resistance and anti-fatigue performances of high-strength materials,
wherein a voltage of the pulse electrodes is at least 400 Volts.

2. The method according to claim 1 , wherein the surface to be processed is a surface of a workpiece, and wherein the method further comprises:
A) the surface of the workpiece is affixed with the aluminum foil, and the laser is irradiated on a surface of the aluminum foil, the laser being a nanosecond pulse laser;
B) the aluminum foil absorbs laser energy to gasify and form gasified substances;
C) under action of the laser, the gasified substances ionize and generate a plasmoid with conductive characteristics;
D) the plasmoid continues to absorb the laser energy and expands, making an outer surface of the plasmoid rapidly expand outward;
E) after the outer surface of the plasmoid enters a discharge gap of the pulse electrodes, the pulse electrodes automatically discharge to automatically induce and form a photoelectric composite energy field and generate a high temperature;
F) under action of the high temperature, a plasma density of the plasma rapidly increases and explodes, thereby realizing expansion of the plasma; and
G) under constraint of a discharge medium, the plasma impacts the surface of the workpiece with a shock wave and produces a strengthening effect.

3. The method according to claim 2 , wherein the pulse electrodes comprise 2 to 6 symmetrical electrodes, and wherein the symmetrical electrodes are symmetrically arranged in a horizontal plane around a center of a light spot on the aluminum foil.

4. The method according to claim 2 , wherein a critical voltage of a power supply of the pulse electrodes is

U
0

=

E
r

·
D

=

E
r

⁡

(

L
1

-

Vt
0

)

=

E
r

⁡

(

L
1

-

Bt
0

⁢

E

τ
⁢

⁢

d
2

)

,

where E r is a critical electric field strength when the discharge medium is broken down, D is a distance between an outer surface of the plasma and the pulse electrodes when the discharge medium is broken down, L 1 is a distance between a discharge end of the pulse electrodes and a spot center on a surface of the aluminum foil, V is a speed of plasma expansion, t 0 is a time of the discharge medium being broken down, E is an energy of the laser, r is a pulse width of the laser, d is a diameter of a laser spot, and B is a constant obtained from experimental data.

5. The method according to claim 4 , wherein a spacing L 2 between the pulse electrodes is 0.8˜1.0R, and R is a diameter of the laser spot;
and wherein the distance L 1 between the discharge end of the pulse electrodes and the spot center on the surface of the aluminum foil is maintained in a range of 0.5R to 0.8R.

6. The method according to claim 4 , wherein a time distribution of the shock wave is adjusted by the time t 0 of the discharge medium being broken down, and the time t 0 of the discharge medium being broken down is adjusted by the distance L 1 between the discharge end of the pulse electrodes and the spot center on the surface of the aluminum foil, the time t 0 is calculated as

t
0

=

L
1

-
D

V

,

and a time distribution function of a pressure of the shock wave is

P
⁡

(
t

Assignees

• Univ Jiangsu

Inventors

• Zhou Jianzhong
• Meng Xiankai
• Huang Shu
• Sheng Jie
• Su Chun
• Zhou hongda
• Yang Xiangwei
• Chen Hansong

Classifications

• B23K26/122

  in a liquid, e.g. underwater · CPC title

• C21D10/00

  Modifying the physical properties by methods other than heat treatment or deformation · CPC title

• B23K26/348

  in combination with arc heating, e.g. tungsten inert gas [TIG], metal inert gas [MIG] or plasma welding · CPC title

• B23K26/356

  by shock processing · CPC title

• C21D10/005 Primary

  by laser shock processing · CPC title