Laser shock peening method and device for bottom surface of tenon groove of aircraft blade

Abstract

A laser shock peening method and device for a bottom surface of a tenon groove of an aircraft blade. During the laser shock peening process, according to geometric characteristics of the bottom surface of a tenon groove, a circular facula of a laser beam is changed into a strip-shaped facula, at the same time as a flow-guiding injection device and a water pumping device are respectively arranged at two end surfaces of the bottom surface of the tenon groove to ensure the stability of a water confinement layer.

Claims

1. A laser shock peening method for a bottom surface of a tenon groove of an aircraft blade, the method comprising: changing a laser beam with a circular facula into a laser beam with a strip-shaped facula and high power density, so as to carry out laser shock peening for the bottom surface of a tenon groove that is covered by an absorbing layer, according to the geometric characteristics of the bottom of the tenon groove; wherein the laser beam with the strip-shaped facula has a width between 0.5 mm and 1 mm, a length between 7 mm and 14 mm, and pulses providing between 5 J and 12 J of energy per pulse with a pulse width between 10 ns and 30 ns; and utilizing a flow-guiding injection device and a water pumping device to control water flow parameters at a water inlet and a water outlet on the bottom of the tenon groove respectively, to create a water confinement layer having a thickness from 1 mm to 1.5 mm.

2. The method according to claim 1, further comprising forming material of the aircraft blade proximate the bottom surface of the tenon groove to have a residual compressive stress of at least 200 MPa.

3. The method according to claim 2, wherein translating the aircraft blade along a processing path relative to the laser beam with the strip-shaped facula comprises translating the blade in at least two mutually perpendicular directions, each perpendicular to a direction of the laser beam with the strip-shaped facula.

4. The method according to claim 1, further comprising translating the aircraft blade along a processing path relative to the laser beam with the strip-shaped facula.

5. The method according to claim 1, wherein utilizing a flow-guiding injection device and a water pumping device to control water flow parameters comprises forming a water confinement layer having a uniform and stable thickness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of an aircraft blade;

(2) FIG. 2 is a schematic diagram of plasma shielding;

(3) FIG. 3 is a schematic diagram of laser shock peening for the bottom surface of a tenon groove of an aircraft blade;

(4) FIG. 4 is a schematic diagram of the end surface of water outlet of an injection head;

(5) FIG. 5 is a schematic diagram of the end surface of water inlet of a water pumping header;

(6) FIG. 6 is a schematic diagram of the processing path of laser shock peening; and

(7) FIG. 7 is a schematic diagram of sampling points for residual stress testing of the bottom surface of a tenon groove.

(8) Among the figures: 1blade, 2bottom surface of tenon groove, 3tenon, 4plasma, 5laser, 11laser control unit, 12laser beam with a circular facula, 13light path conversion system, 14laser beam with a strip-shaped facula, 15blade, 16water pumping header, 17water pump, 18water trough, 19five-axis working platform, 20water pumping hose, 21third fixture, 22second fixture, 23first fixture, 24injection head, 25water supply hose, 26flow-guiding injection device, 27water tank, 30end surface of water outlet of injection head, 31end surface of water inlet of water pumping header, 32processing path, 41point A, 42point B, 43point C, 44point D, 45point E, 46point F;

(9) The height H1 of the water outlet is 1.5 mm, and the length L1 is 10 mm.

(10) The height H2 of the water outlet is 1.5 mm, and the length L2 is 10 mm.

DETAILED DESCRIPTION

(11) Hereunder, this disclosure will be further detailed with reference to the accompanying drawings.

(12) Embodiment 1

(13) During the surface peening for the bottom surface of the tenon groove of the aircraft blade 1 shown in FIG. 1, a laser shock peening device for the bottom surface of a tenon groove of an aircraft blade shown in FIG. 3 is utilized to avoid the plasma shielding effect shown in FIG. 2. The device comprises: a laser 10, a laser control unit 11, a light path conversion system 13, a five-axis working platform 19, a first fixture 23, a second fixture 22, a third fixture 21, a water tank 27, a flow-guiding injection device 26, a water supply hose 25, an injection head 24, a water pumping header 16, a water pumping hose 20, a water pump 17, and a water trough 18, wherein, the end surface of water outlet of injection head 24 and the end surface of water inlet of water pumping header 16 are shown in FIGS. 4 and 5, respectively.

(14) The first fixture 23, second fixture 22, and third fixture 21 are mounted on the five-axis working platform 19, and the second fixture 22 is disposed between the first fixture 23 and the third fixture 21, the injection head 24 is mounted on the top of the first fixture 23, and is connected to the flow-guiding injection device 26 via the water supply hose 25, and the water inlet tube of the flow-guiding injection device 26 is connected to the water tank 27, the water pumping header 16 is mounted on the top of the third fixture 21, and is connected to the water pump 17 via the water pumping hose 20, and the water outlet of the water pump 17 is connected to the water trough 18, the laser 10 is disposed right above the five-axis working platform 19, and the light path conversion system 13 is disposed between the laser 10 and the five-axis working platform 19.

(15) Embodiment 2

(16) The device can be used through the following steps: Apply a black paint or absorbing layer on the bottom surface 2 of a tenon groove of a blade, and then mount the blade 15 onto the second fixture 22 and keep the bottom surface 2 of the tenon groove in level state; Mount the injection head 24 onto the top of the first fixture 23 in a way that the end surface 30 of water outlet of the injection head 24 closely abuts one end surface of the bottom of the tenon groove, and the bottom surface of the water outlet of the injection head 24 is in the same plane as the bottom surface 2 of the tenon groove, and the two sides of the water outlet are at the outer side of the side surfaces of the bottom of the tenon groove; Connect the injection head 24 and flow-guiding injection device 26 with the water supply hose 25, and then connect the water inlet tube of the flow-guiding injection device 26 to the water tank 27; Mount the water pumping header 16 onto the top of the third fixture 21 in a way that the end surface 31 of water inlet of the water pumping header 16 closely abuts the other end surface of the bottom of the tenon groove, the bottom surface of water inlet of the water pumping header 16 is in the same plane as the bottom surface 2 of the tenon groove, and the two sides of the water inlet are at the outer side of the side surfaces of the bottom of the tenon groove; Connect the water pumping header 16 and water pump 17 with the water pumping hose 20, and then connect the water outlet tube of the water pump 17 to the water trough 18; Set the facula diameter to 3 mm, pulse energy to 5 J, and pulse width to 10 ns for the laser with the laser control unit; Change the laser beam 12 with a circular facula into a laser beam 14 with high-power density and a strip-shaped facula having a width of 0.5 mm and a length of 14 mm via the light path conversion system 13, and ensure the laser beam 14 with a strip-shaped facula is perpendicular to the horizontal plane and the focal spot of the laser beam 14 with a strip-shaped facula is on the bottom surface 2 of the tenon groove; Adjust the parameters of the flow-guiding injection device 26 and water pump 17, so that the water pressure is 0.1 MPa and both of the flow rates are 0.810.sup.5 m3/s, to create a uniform and stable water confinement layer having a thickness of 1 mm-2 mm on the bottom of the tenon groove; Switch on the laser 10 and start laser shock peening for the bottom surface 2 of the tenon groove, and complete the peening for the entire bottom surface 2 of the tenon groove by translating the five-axis working platform 19 along the processing path 32 shown in FIG. 6; After the processing, carry out a residual stress test at the points labeled in FIG. 7, to evaluate the effect of laser shock peening for the bottom surface of the tenon groove of the aircraft blade.
Embodiment 3

(17) Use the same method and steps as in Embodiment 2, but change the pulse energy to 6 J, pulse width to 20 ns, width of strip-shaped facula to 1 mm, length of strip-shaped facula to 7 mm, water pressure in the flow-guiding injection device 26 and water pump to 0.2 MPa, and flow rates to 1.510.sup.5m.sup.3/s.

(18) Embodiment 4

(19) Use the same method and steps as in Embodiment 2, but change the pulse energy to 12 J, pulse width to 30 ns, width of strip-shaped facula to 2 mm, length of strip-shaped facula to 3.5 mm, water pressure in the flow-guiding injection device 26 and water pump to 0.3 MPa, and flow rates to 2.010.sup.5 m.sup.3/s. As can be seen from Table 1, the method disclosed herein can effectively introduce 200 MPa or higher residual compressive stress into the bottom surface of the tenon groove of the aircraft blade, and thereby improve the service life of the aircraft blade.

(20) TABLE-US-00001 TABLE 1 Result of Residual Stress Test of the Bottom Surface of the Tenon Groove of the Aircraft Blade in the Embodiments Sample Residual Stress before Laser Shock Peening (MPa) (Material TC4) Point A Point B Point C Point D Point E Point F Embodiment 2 10 8 9 4 3 5 Embodiment 3 6 9 6 2 7 8 Embodiment 4 8 5 7 6 4 2 Sample Residual Stress after Laser Shock Peening (MPa) (Material TC4) Point A Point B Point C Point D Point E Point F Embodiment 2 286 267 278 304 312 320 Embodiment 3 346 352 349 397 406 414 Embodiment 4 432 443 436 482 495 510

(21) In Table 1: positive values represent tensile stress, while negative values represent compression stress.