Anti-fatigue controlled laser shot peening method and device therefor

A laser peening and anti-fatigue technology, which is applied in the direction of manufacturing tools, heat treatment process control, process efficiency improvement, etc., can solve the problems that have not yet been searched for controlled laser peening strengthening, and meet the strengthening requirements and improve work efficiency. Effect

Inactive Publication Date: 2008-10-01

JIANGSU UNIV

2 Cites 41 Cited by

AI-Extracted Technical Summary

Problems solved by technology

[0005] Research literature and related patents on controlled laser sh...

Method used

Control system is made up of computer control system (1), neodymium glass laser controller (2), machine tool controller (15), measurement feedback system, machine tool cont...

Abstract

The invention relates to a method and a device for intensifying controlled laser shot peening, first of all, a fatigue analysis model is established in a fatigue analysis software, distribution of residual stress in the accessories is optimized in light of the expectant fatigue life value after the intensification to obtain the distribution of residual stress which meets the demand; the distribution of residual stress is imported into a structural mechanics CAE analysis software to obtain by optimization laser shock wave pressure acting on the surface of a sheet metal and the shot peening track; after than a computer control system automatically selects the pulse parameter and a light beam changing device while the laser shot peening; the laser emits a high energy short pulse laser beam to be converted into the high amplitude shock wave pressure acting on the surface of the accessories after being subjected to an optical changing device and an optical mask; a measurement feedback system is used to online check the distribution situation of the stress and strain on the surface layer of the accessories in the laser shot peening, the special computer software module is utilized to perform error analysis and parameter correction, ensuring to generate the expectant distribution of residual stress on the surface layer of the accessories to meet the intensification demand of the anti-fatigue performance.

Application Domain

Heat treatment process controlProcess efficiency improvement

Technology Topic

Life valuePulse parameter +13

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Examples

Experimental program(1)

Example Embodiment

[0051] Example: Laser shot peening of 6061-T6 aviation aluminum alloy single center hole fatigue specimen

[0052] Because laser shot peening is especially suitable for processing fatigue parts with local stress concentration, such as machine parts with fatigue-prone notches, holes, and corners, and aluminum alloys are commonly used aerospace materials, 6061-T6 is selected in this example. The aviation aluminum alloy single center hole fatigue specimen is laser shot peened, and its shape and size are as follows Figure 4 As shown, the outer dimensions are machined first, and the center hole is subsequently bored to a diameter of 2mm. The experiment uses a PLA30050 fatigue tensile testing machine. Before laser shot peening of the parts, when the maximum load is 7KN, the minimum load is 0.7KN, the stress ratio is 0.1, and the test frequency is 13HZ, the fatigue life is 88000. It is required to increase the fatigue life by more than 150% by laser shot peening, that is, more than 120,000 times. Since the stress change after laser shot peening is mainly concentrated near the small hole with a diameter of 2 mm, in order to simplify the finite element analysis model, the area of 7.5 × 7.5 mm near the small hole in the test area is selected for fatigue performance and limited laser shot peening. meta-simulation, such as Figure 5 shown.

[0053] Firstly, the corresponding fatigue analysis model is established in the general fatigue analysis software, Image 6 Shown is the fatigue life cloud diagram of the specimen before laser shot peening, the white part in the figure is the area where fracture occurs first, from the fatigue life analysis result file (such as Figure 7 ), it can be seen that the fatigue life is 88381 times at this time. According to the expected fatigue life value after strengthening, the residual stress distribution in the part is optimized, and the residual stress distribution cloud map that meets the fatigue performance strengthening requirements is obtained, such as Figure 8 shown, Figure 9 For the fatigue analysis life cloud map corresponding to the optimized residual stress distribution, the white part in the figure is the area where fracture occurs first, from the fatigue life analysis result file (such as Figure 10 ), it can be seen that the fatigue life at this time is 127000 times, which meets the requirements of fatigue performance enhancement.

[0054] Will Figure 8 The optimized residual stress distribution shown is imported into the structural mechanics CAE analysis software to obtain the following Figure 11 The stress distribution cloud diagram shown, optimizes the laser shock wave pressure and shot peening trajectory acting on the surface of the metal sheet, such as Figure 12 shown;

[0055] According to formulas 1 and 2, the computer control system automatically selects the optimized laser blasting pulse energy, pulse width, pulse shape, number of blasting times and beam conversion device corresponding to the optimized laser shock wave pressure;

[0056] When the laser power density I 010 9 W/cm 2 When , the shock wave peak pressure generated by laser shock is expressed by the following formula:

[0057] P = ( γ + 1 2 γ ) 2 γ γ - 1 ρ 0 γ + 1 [ 2 ( γ 2 - 1 ) I 0 ρ 0 ] 2 3 - - - ( 1 )

[0058] where P is the shock wave peak pressure, ρ 0 is the initial gas density of the energy conversion gas, I 0 is the laser pulse power density, and γ is the adiabatic index of the plasma. I 0 can be expressed as

[0059] Simultaneous laser pulse power density

[0060] I 0 = αE τA - - - ( 2 )

[0061] where α is the absorption coefficient of the laser energy on the surface of the material, E is the laser pulse energy, τ is the laser pulse width, and A is the spot area. The relationship between the laser shock wave peak pressure and the laser pulse energy, pulse width, spot area and other parameters is established by formulas 1 and 2, so the computer control system can reasonably match the laser shot peening process parameters.

[0062] Use the computer to compile the NC processing program, control the light guide system and the trajectory of the worktable to carry out laser shot peening processing; a high-energy short-pulse laser beam emitted by the laser can be converted into several groups of pulses through the beam conversion device, and then pass through the optical mask. The pulse action method required for mode screening is irradiated on the energy converter on the surface of the workpiece, and the energy converter converts the absorbed laser energy into the corresponding shock wave pressure and acts on the surface of the metal part; the measurement feedback system is used to detect the parts during laser shot peening online. For the distribution of surface stress and strain, the stress-strain analysis module under the loading of special laser shock wave based on ABAQUS software platform (such as figure 2 ) to carry out error analysis and parameter correction, and adjust the laser shock wave pressure and the shot peening trajectory by the laser controller and the laser shot peening head to ensure that the expected residual stress distribution is generated on the surface of the part to achieve the enhancement of anti-fatigue performance requirements.

[0063] Figure 13-14 The morphology of the 6061-T6 aviation aluminum alloy single center hole fatigue specimen before and after laser shot peening is shown respectively. It can be seen from the figure that the action area of the shock wave pressure induced by the interaction between the pulsed laser beam and the material is larger than the diameter of the laser spot. , which is consistent with the simulation results.

[0064] The PLA30050 fatigue tensile testing machine was used for experimental verification. When using the parameters of the maximum load of 7KN, the minimum load of 0.7KN, the stress ratio of 0.1, and the test frequency of 13HZ, the fatigue life was 127130 times. The residual stress distribution in the sample meets the fatigue resistance enhancement requirements.

[0065] There are many more examples of laser shot peening for anti-fatigue manufacturing. Different laser shot peening trajectories and laser shock wave pressures can achieve different fatigue performance strengthening requirements. Only its technical solutions and some examples are described here.

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Improve work efficiency

Anti-fatigue controlled laser shot peening method and device therefor

AI-Extracted Technical Summary

Problems solved by technology

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Abstract

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Examples

Example Embodiment

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Description & Claims & Application Information

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