A blade high-low cycle life improvement method based on surface reinforcement region identification

Abstract

The application provides a blade high-low cycle life improvement method based on surface strengthening area selection, and realizes the steps as follows: (1) carrying out blade static strength analysis to determine stress / strain distribution under the maximum working state; (2) carrying out blade vibration characteristic analysis and blade disc coupling vibration characteristic analysis to preliminarily determine blade dangerous positions under vibration; (3) designing feature simulation pieces for the blade dangerous positions, carrying out high-low cycle composite fatigue test under load to obtain composite fatigue life N CCF and the relationship between high-low cycle stress / strain (σ L , σ H , ε L , ε H ); (4) determining the highest stress level of the dangerous positions and the nearby positions according to the relationship between N CCF and the high-low cycle stress / strain (σ L , σ H , ε L , ε H ) and the target high-low cycle life; (5) determining the initial residual stress compensation value requirement based on the static strength analysis result and the target highest stress level; (6) determining the strengthening process according to the residual stress requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of material engineering, processing technology and material science, and particularly relates to a blade high-low cycle life improvement method based on surface strengthening area identification. BACKGROUND

[0002] The basic idea of blade fatigue life improvement is to prolong the number of fatigue stress cycles that the blade can withstand during actual operation, thereby prolonging its service life. This is very critical because aircraft engine blades work at high speed and in high temperature and pressure environments, and are subjected to extreme mechanical and thermal stresses, which can easily cause fatigue damage. In order to meet the safety requirements of some key and important metal components within the standard requirements, it is necessary to conduct in-depth research on the life improvement of these structural components.

[0003] Surface strengthening relies on technologies in multiple fields such as material science, engineering, and manufacturing technology. (1) Surface modification techniques, including technologies such as plasma spraying, electrochemical deposition, chemical vapor deposition, etc., are used to apply additional materials or coatings on the surface of the blade to improve its corrosion resistance, wear resistance, and high-temperature performance. (2) Heat treatment techniques, the blade may need to undergo special heat treatment processes to eliminate processing residual stress and improve its structure and performance, including strength, hardness, and fatigue resistance. (3) Surface mechanical strengthening, including shot peening, roller peening, laser shock peening, etc. The basic principle of surface mechanical strengthening is to introduce residual compressive stress and changes in microstructure near the surface by impact or extrusion, thereby improving the fatigue resistance of the material.

[0004] Laser shock peening is a new and effective surface treatment method to improve the surface performance of metal materials. Laser shock peening, as a new strengthening technology developed from traditional shot peening, uses a high-frequency, high-power, short-pulse laser beam to impact the surface of a workpiece with an absorbing layer through an intermediate confinement layer. Laser shock peening can significantly extend the high-low cycle fatigue life of cast and forged blades, with a more significant impact on the life of cast blades. Other related studies have measured the depth and magnitude of the residual compressive stress introduced by laser shock peening, with the depth of the residual compressive stress exceeding 1 mm, and the maximum surface residual compressive stress can reach more than 600 MPa under the action of multiple laser impacts.

[0005] For the reinforcement area selection, the existing various different techniques can achieve the effect of area screening: (1) Non-destructive testing techniques including ultrasonic testing, X-ray testing and magnetic particle testing, etc. are used to evaluate the hidden defects or problem areas in the blade material. Through the NDT technique, the specific area requiring surface reinforcement can be determined. (2) Numerical simulation and finite element analysis tools can be used to predict the stress distribution and stress concentration areas of the blade under different working conditions. This helps to determine where surface reinforcement needs to be carried out to improve the life. (3) Using high-resolution surface scanning and imaging techniques (such as scanning electron microscope or optical microscope) can detect and analyze the microstructure of the blade surface to determine the location of wear, corrosion or fatigue damage. SUMMARY

[0006] The technical problem solved by the present application: The present application aims at the existing deficiencies, in order to meet the application requirements of the real working load of the blade, the authenticity of the life prediction, the accuracy of the life improvement, etc. A high-low cycle life improvement method based on the identification of the optimized reinforcement area of the blade surface is provided.

[0007] The technical solution of the present application: A blade high-low cycle life improvement method based on the identification of the surface reinforcement area, the implementation steps of which are as follows:

[0008] (1) Blade static strength analysis: according to the actual load environment of the blade, the stress / strain distribution of the blade under the maximum working state is determined.

[0009] (2) Blade vibration characteristic analysis: according to the stress / strain distribution obtained in the previous step, the blade vibration characteristic analysis and the bladed disc coupled vibration characteristic analysis are carried out to determine the dangerous parts of the blade under vibration conditions.

[0010] (3) Blade simulation part design: according to the vibration characteristic analysis of the blade in the previous step, a characteristic simulation part is designed, and high-low cycle composite fatigue tests of the simulation part and the standard part are carried out to obtain the composite fatigue life N CCF and the relationship with high-low cycle stress / strain (σ L , σ H , ε L , ε H );

[0011] (4) Determine the highest stress level of the dangerous part: according to the relationship between N CCF and the high-low cycle stress / strain (σ L , σ H , ε L , ε H ) obtained in the previous step, as well as the actual high-low cycle life requirement, the highest stress level near the dangerous part is determined

[0012] (5) determining the initial residual stress compensation value, according to the highest stress level near the dangerous position determined in the last step and the static strength analysis result obtained in step (1), determining the initial residual stress requirement that needs to be compensated.

[0013] (6) determining the strengthening process, determining the strengthening process according to the residual stress requirement.

[0014] Compared with the prior art, the present application has the characteristics of simple operation, strong controllability, good compatibility, high efficiency, and can realize the actual load condition life improvement, and the specific performance is as follows:

[0015] (1) The present application is close to the engineering practice. The real load environment of the blade is under the combined load environment of high-frequency vibration load and low-frequency tensile load. The life improvement area selection determined by the S-N curve cannot truly reflect the actual load condition of the blade. The present application is closer to the engineering practice, can more accurately identify the dangerous position of the blade under the combined fatigue load, and can more accurately identify the real stress level. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the test flowchart of the present method;

[0017] Figure 2 is the high-low cycle fatigue stress-life curve and conventional stress-life curve diagram obtained by the present method. DETAILED DESCRIPTION

[0018] The present application will be further described below in combination with the drawings and embodiments.

[0019] The present application provides a blade high-low cycle life improvement method based on surface strengthening area identification, and the specific process is as shown in Figure 1 and Figure 2 .

[0020] (1) Blade static strength analysis, determining the dangerous position of the blade under the maximum working condition.

[0021] (2) Carrying out blade vibration characteristic analysis and bladed disc coupled vibration characteristic analysis, determining the dangerous frequency through Campbell diagram according to the actual clamping process and rotating speed of the blade, simulating and analyzing the blade vibration characteristics and bladed disc vibration characteristics. Calculate the structural strength of the blade under the dangerous frequency condition, find the stress concentration area and the maximum stress point, and determine the dangerous position.

[0022] (3) Through the development of the same material, the same forging process of the standard piece, the similar blade feature simulation piece of the blade dangerous part stress / strain distribution, the high-low cycle composite fatigue test, the life results under different high-low cycle stress conditions are obtained, since the existing S-N curve is the curve drawn based on the high cycle fatigue, there is difference with the real working state load condition of the blade, so the life results obtained from the high-low cycle composite fatigue test are used for correcting the S-N curve. Figure 2

[0023] (4) Determine the compensation residual stress, according to the test results of step (3), the difference between the stress amplitude of the dangerous part to be strengthened and the target stress amplitude is determined according to the actual demand, combined with the real load condition of the blade, the difference is the residual compressive stress to be compensated.

[0024] (5) Surface strengthening and verification, according to the residual compressive stress value to be compensated determined in step (4), different strengthening processes are selected to strengthen the surface of the blade.

[0025] The part of the present application not disclosed in detail belongs to the known technology in the art.

[0026] Although the above describes the illustrative specific embodiments of the present application, so as to make the skilled in the art understand the present application, it should be clear that the present application is not limited to the scope of the specific embodiments, for the ordinary skilled in the art, as long as various changes are within the spirit and scope of the present application limited and determined by the appended claims, all the inventions using the concept of the present application are included in the protection.​

Claims

1. A blade high-low cycle life improvement method based on surface-strengthened region identification, characterized in that, The implementation steps are as follows: (1) static strength analysis, according to the actual clamping mode of the blade and the actual working load environment of the blade, the stress and strain distribution of the blade under the maximum state is determined; (2) vibration modal analysis, according to the actual working condition of the blade, the vibration modal analysis of the blade and the coupled vibration modal analysis of the blade disc are carried out, and the real dangerous position of the blade under the vibration condition is determined; (3) Blade simulation piece design, according to the vibration characteristic analysis of the blade in step (2), carry out the design of blade characteristic simulation piece, conduct high-low cycle composite fatigue test of blade characteristic simulation piece and standard piece, and obtain the composite fatigue life N CCF Relationship with high-low cycle stress / strain (σ L , σ H , ε L , ε H ) (4) Determine the compensation residual stress, according to the actual life requirements and the combined fatigue life N obtained in step (3) CCF The relationship between high and low cycle stress / strain (σ L , σ H , ε L , ε H ) is determined to determine the residual stress value requirement to be compensated; (5) determining the surface strengthening process of the blade, according to the residual stress demand to be compensated, the surface strengthening process of the blade is determined; In step (3), the method designs a feature simulation piece based on the stress / strain distribution of the dangerous part of the blade according to the actual load environment of the blade. Meanwhile, high-low cycle fatigue tests of the blade standard piece and the simulation piece are carried out, and the composite fatigue life N CCF of the simulation piece is obtained Relationship with high-low cycle stress / strain In step (4), the method determines the value of the residual stress needed to compensate for the life requirement based on the high and low cycle stress / strain curves and the static strength analysis results obtained in step (1). ccf Composite fatigue life and high and low cycle stress / strain curves and static strength analysis results obtained in step (1) to determine the value of the residual stress needed to compensate for the life requirement; In step (5), the method can specifically guide the selection of the surface strengthening process according to the residual compressive stress value to be compensated, and the selected strengthening process can be closer to the actual demand.

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