Ultrahigh-cycle fatigue life prediction method for hydraulic pump cylinder body of bimetal combined process

Abstract

The invention belongs to the technical field of aviation electromechanics, and particularly relates to a method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder body through a bimetal combination process. Analyzing the key position where the hydraulic pump cylinder body is prone to fatigue faults, and determining the stress condition of the key position of the hydraulic pump cylinder body; according to the geometric parameters of the key position of the hydraulic pump cylinder body, designing a test piece of an ultra-high cycle fatigue test; according to the stress form of the key position and the load-stress ratio condition, an ultra-high cycle fatigue test of the test piece is carried out; obtaining a stress-life relationship of the bimetal bonding process test piece; and predicting the service life of the hydraulic pump cylinder body structure according to the allowable safety coefficient of the hydraulic pump cylinder body structure and the stress of the key position of the structure. According to the invention, the fatigue performance verification test of the bimetallic bonding process of the hydraulic plunger pump cylinder body can be rapidly realized, and the ultrahigh-cycle fatigue strength and fatigue life evaluation of the structure in a high-temperature service environment can be realized.

Description

Technical Field

[0001] This invention belongs to the field of aviation electromechanical technology, specifically relating to an ultra-high cycle fatigue test and fatigue life prediction method for a bimetallic bonding process of an aviation hydraulic plunger pump cylinder. Background Technology

[0002] As the most core and technically challenging component of a hydraulic system, the piston pump faces increasingly stringent requirements regarding its lifespan and reliability. The lifespan of an aviation hydraulic piston pump is determined by multiple factors, among which the performance of the three key friction pairs (piston pair, slipper pair, and flow distribution pair) is a decisive factor. Currently, piston pump friction pairs commonly employ a copper-steel bimetallic bonding process to ensure structural strength and wear resistance. Their lifespan is determined by the two materials and their bonding characteristics. Past failure analyses show that fatigue crack initiation typically occurs at the bimetallic bonding layer.

[0003] Domestically produced large-displacement engine drive pumps operate at speeds exceeding 3500 r / min, while small-displacement electric pumps can even reach speeds exceeding 10000 r / min. To meet the requirement of an 8000-hour service life, the cylinder block will undergo at least... The alternating load is a typical ultra-high cycle fatigue problem. The cylinder block, as a key component in a piston pump, is related to the piston assembly and distribution assembly, and bears complex loads. However, for the relatively large and complex structure of a hydraulic piston pump cylinder block, fatigue testing technology is quite difficult. Furthermore, during the design phase, the cylinder block has not yet been manufactured, making actual fatigue testing impossible. From an economic perspective, verifying… The fatigue life of a piston pump cylinder requires conventional fatigue testing equipment to conduct tests over several months or even years, and the cost is considerable. Therefore, there is an urgent need for a simple and effective method to predict the fatigue life of a piston pump cylinder for the optimization of structural design and manufacturing processes. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the background technology described above. This invention proposes a method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process. This method can quickly verify the fatigue performance of the bimetallic bonding process of the hydraulic plunger pump cylinder block and evaluate the ultra-high cycle fatigue strength and fatigue life of the structure under high-temperature service conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process, the method comprising the following steps: Step S1: Analyze the key locations in the hydraulic pump cylinder that are prone to fatigue failure, and determine the stress conditions at the key locations in the hydraulic pump cylinder. Step S2: Design the test specimen for ultra-high cycle fatigue test based on the key position geometric parameters of the hydraulic pump cylinder. Step S3: Based on the stress form at key locations and the load-stress ratio, conduct ultra-high cycle fatigue tests on the test specimens; obtain the stress-life relationship of the bimetallic bonded test specimens. Step S4: Based on the allowable safety factor of the hydraulic pump cylinder structure and the stress magnitude at key structural locations, predict the service life of the hydraulic pump cylinder structure.

[0006] Furthermore, in step S1, based on the previous cylinder block failure analysis of the aviation hydraulic plunger pump, the cylinder block flow distribution window is selected as the key analysis area; based on finite element analysis, the stress distribution of the bimetallic bonding layer in this key area is analyzed in detail, and different rotation angles are extracted. Maximum stress on the steel layer at the bimetallic joint and minimum stress Used to determine the load ratio in ultrasonic fatigue testing ;in, .

[0007] Furthermore, step S2 of the design process includes: designing an ultra-high cycle fatigue test piece based on the key geometric features of the waist hole to ensure the geometric similarity between the test piece and the waist hole structure; adjusting the length and width dimensions of the test piece based on the finite element method to meet the resonance requirements of the ultrasonic fatigue test at 20kHz, while ensuring the key geometric feature conditions; and strictly processing the test piece according to the aerospace hydraulic plunger pump processing technology (e.g., surface roughness Ra, fillet size) to ensure the consistency of the manufacturing process that may affect fatigue performance.

[0008] Furthermore, key geometric features include radius. Copper layer thickness , waist hole spacing wait.

[0009] Furthermore, the specific acquisition process in step S3 is as follows: based on the operating environment temperature and load conditions of the aviation hydraulic plunger pump, fatigue tests are conducted using high-temperature ultrasonic fatigue testing equipment to obtain the service environment temperature. T The stress ratio is R Ultra-high cycle fatigue stress-life data at stress levels 3-5. For each stress level, 4-5 specimens are tested, and the stress is... This indicates the magnitude of stress on the steel matrix; analysis of ultra-high cycle fatigue test data. Based on the characteristics, stress-life curves for bimetallic bonding processes were established.

[0010] Furthermore, a high-temperature ultrasonic fatigue test was conducted on the cylinder block steel material at a loading frequency of 20 kHz within the range of room temperature to 125 ± 10 °C. to High-temperature and ultra-high-cycle fatigue test under cyclic loading.

[0011] Furthermore, the high-temperature ultrasonic fatigue test method utilizes a high-frequency induction heating device to heat the specimen and uses an infrared thermometer to monitor the temperature of the middle section of the specimen in real time, ultimately achieving rapid fatigue loading under high-temperature conditions.

[0012] Further, the prediction process in step S4 is as follows: Based on the stress magnitude of the cylinder block structure simulated by the model, the ultra-high cyclic fatigue strength of the cylinder block is checked, considering the number of dangerous parts in the plunger pump distribution pair and the survival rate requirements, according to... The theoretical ultra-high cycle fatigue life of the curve calculation structure.

[0013] Furthermore, based on simulation analysis methods, the maximum stress at the critical point of the distribution sub-cylinder block waist hole under service conditions was obtained. And taking into account the allowable safety factor , obtain structural stress ; to structural stress Substituting the ultra-high cycle fatigue stress-life curve of the cylinder block structure into the curve yields the safe fatigue life of the cylinder block structure. .

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: The method for evaluating the ultra-high cycle fatigue strength and fatigue life of the bimetallic bonding process of the cylinder block of the aviation hydraulic plunger pump provided by this invention can realize the prediction and evaluation of the ultra-high cycle fatigue strength and fatigue life of the cylinder block structure under actual working conditions. It provides more accurate data support for the fatigue strength and life analysis and optimization design of the cylinder block under ultra-high cycle fatigue load, and provides a basis for the safe operation of the ultra-long service life of the aviation hydraulic plunger pump cylinder block.

[0015] The technical solution of this invention utilizes experimental methods to obtain test data points on the ultra-high cycle fatigue performance of the bimetallic bonding process on the end face of the distribution sub-cylinder, and then considers various factors. The solution proposed in this invention is easy to implement in engineering and requires relatively low costs. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the ultra-high cycle fatigue test and life assessment method for the bimetallic bonding process of the piston pump rotor end face of a 21MPa pressure type II hydraulic system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of an ultra-high frequency structure test piece based on a plunger pump rotor structure design according to an embodiment of the present invention; Figure 3 The stress-life curve of the bimetallic bonding process of the distribution rotor of the aviation hydraulic plunger pump in an embodiment of the present invention is shown. Detailed Implementation

[0017] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific design details are set forth in the following detailed description to provide a more complete understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setup and method set forth below, but covers any improvements, substitutions, and modifications to the structures, methods, and devices without departing from the spirit of the invention. In the drawings and the following description, any parts not exhaustively described are considered to be common knowledge or conventional practices in the art.

[0018] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] See appendix Figures 1-3 , Figure 1 This is a flowchart illustrating the ultra-high cycle fatigue test and life assessment method for the bimetallic bonding process of the piston pump cylinder end face of a 21MPa pressure type II hydraulic system according to an embodiment of the present invention. The ultra-high cycle fatigue test and life assessment method includes: Step S1: Based on the obtained stress variation of the key points on the cylinder block structure with the rotation angle, the maximum stress is determined. and minimum stress , Specifically, each rotation of the cylinder of an aviation hydraulic piston pump involves one oil intake and discharge cycle, resulting in one cycle of fatigue loading. Therefore, over an 8000-hour service life, the ultra-high cycle fatigue loading can reach [amount missing]. In this study, the alternating stress of the ultra-high cycle fatigue cycle of the cylinder block of an aviation hydraulic plunger pump was calculated using existing three-dimensional finite element analysis methods.

[0020] Based on engineering experience, uniaxial equivalent stress is calculated according to certain strength theories. Generally, the first strength theory (maximum principal stress criterion) is used to determine the maximum stress at the high-temperature hazard point. Minimum stress at high temperature danger points In this embodiment, the maximum stress of the structure under its own weight is calculated under rated load operating conditions. and minimum stress Those skilled in the art will know that the maximum stress at the critical point is calculated using the first strength theory. and the minimum stress at the danger point The method will not be repeated here.

[0021] Step S2: Based on the previous fault analysis, analyze the key parts of the flow distribution pair for fatigue damage, namely the cylinder block flow distribution window (hereinafter referred to as the waist hole), based on the key geometric features of the waist hole (radius). Copper layer thickness , waist hole spacing (etc.) To design ultra-high cycle fatigue test specimens, the geometric similarity between the test specimens and the waist hole structure is ensured. Under the premise of ensuring key geometric characteristics, the length, width, and steel layer thickness of the test specimens are adjusted based on the finite element method to meet the resonance condition requirements of 20kHz for ultrasonic fatigue testing, and the processing dimensions of the test specimens are determined. Based on the processing dimensions of the test specimens, the test specimens are processed strictly according to the processing technology of aviation hydraulic plunger pumps to ensure the consistency of the process that will affect the fatigue performance during manufacturing.

[0022] Step S3: Obtain the ultra-high cycle fatigue (SN) curve of the cylinder block structure. The SN curve of the cylinder block structure is the basis for predicting its fatigue life and for fatigue-resistant design. The best method to obtain the SN curve is to conduct experiments on a full-size cylinder block structure. However, for large components like cylinder blocks, fatigue testing is technically challenging, and during the design phase, the actual cylinder block structure has not yet been manufactured, making actual experiments impossible. Therefore, in this embodiment, an experimental method is used to obtain SN data points of the ultra-high cycle fatigue using a bimetallic bonding process that retains key geometric features. Then, considering various factors and after correction, the SN curve of the cylinder block structure is obtained.

[0023] Specifically, the ultra-high cyclic fatigue SN data points of the cylinder block steel material were tested. ,in, This refers to the ultra-high cyclic fatigue strength data of cylinder block steel. This data represents the ultra-high cycle fatigue life of cylinder block steel. High-temperature ultrasonic fatigue testing was conducted using a loading frequency of 20 kHz, performing tests on the cylinder block steel within the temperature range of room temperature to 125 ± 10℃. to High-temperature and ultra-high-cycle fatigue testing under cyclic loading was conducted. The high-temperature ultrasonic fatigue testing method utilizes a high-frequency induction heating device to heat the specimen, and an infrared thermometer to monitor the temperature of the middle section of the specimen in real time, ultimately achieving rapid fatigue loading under high-temperature conditions. In this embodiment, ultra-high-cycle fatigue SN data points were tested on the cylinder block steel material, with stress intervals less than 20 MPa, and at least 5 data points were obtained for each stress test, thus obtaining the ultra-high-cycle fatigue SN data points for the cylinder block steel material.

[0024] The ultra-high cycle fatigue (SN) data points of the bimetallic bonding process of the cylinder block obtained from experimental tests can represent the fatigue performance of the actual cylinder block structure to a certain extent. There is no need to further consider the influence of the cylinder block geometry and surface finish on its ultra-high cycle fatigue strength.

[0025] For data points Fitting is performed to obtain the ultra-high cyclic fatigue (SN) curve of the cylinder block structure. Specifically, the Basquin formula can be used for fitting. Those skilled in the art know how to use the Basquin formula to fit data points, and will not be elaborated here.

[0026] Step S4: Determine the allowable safety factor of the cylinder block based on the stress amplitude obtained from the actual stable operation of the aviation hydraulic piston pump. The randomness of fatigue strength and fatigue life is caused by the uncertainty of two major categories of basic random variables: the inhomogeneity of the material's microstructure and the randomness of external loads. The dispersion of fatigue life in ultra-high cycle fatigue is generally much greater than that in low cycle fatigue. The allowable safety factor can also be calculated using reliability theory. In engineering, empirical coefficients are used to ensure the safety and effectiveness of the cylinder block design. The allowable safety factor of the cylinder block structure is based on... It is confirmed that, among them, The allowable safety factor for the cylinder block structure. For the strength safety factor, This is the stress safety factor.

[0027] (c) Uncertainties in material properties can be addressed through… Fitting a 95% survival rate curve to eliminate the influence is acceptable. If a 50% survival rate is adopted, it can be taken as follows: ; (d) When both load and stress are very precise, When load and stress are inaccurate and there are impact and high-stress loads, .

[0028] In this embodiment, based on the SN curve with a survival rate of 95%, and considering partial impact and high stress load conditions, the allowable safety factor is... A value of 1.2 to 1.5 is acceptable.

[0029] In other words, the calculated safety factor must be greater than the allowable safety factor to meet the requirements for ultra-high cycle fatigue strength of the cylinder block structure.

[0030] Step S5: Calculate the ultra-high cycle fatigue life of the cylinder block structure. Specifically, based on... To obtain the safety stress of the cylinder block structure, among which, The safety stress of the cylinder block structure is used as the basis for incorporating the safety stress of the cylinder block structure into the ultra-high cycle fatigue stress. Curve acquisition This refers to the ultra-high cyclic fatigue life of the cylinder block structure. If the calculated safety factor is greater than the allowable safety factor and the safe fatigue life of the cylinder block structure... If the requirements are met, the cylinder block structure can be manufactured according to the existing design; otherwise, the cylinder block structure should be redesigned or a better-performing process should be selected, taking into account the safe fatigue life and ultra-high cycle fatigue life loss of the cylinder block structure.

[0031] The ultra-high cycle fatigue test and fatigue life prediction method for bimetallic bonding process provided by this invention can achieve a stress ratio of [value missing] for aviation hydraulic pumps under high temperature conditions. The quantitative assessment of ultra-high cycle fatigue strength and fatigue life provides more accurate data support for the fatigue strength and life analysis and optimization design of hydraulic plunger pump distribution pairs under ultra-high cycle fatigue loads, and provides a basis for the safe operation of ultra-long service life of aviation hydraulic plunger pump cylinder blocks.

[0032] Ultra-high cycle fatigue testing of bimetallic bonding process at the end face of the piston pump distribution sub-cylinder bore The curves include: Ultra-high cycle fatigue stress-life data points of the copper-steel bonding process of the test cylinder block ,in This refers to the ultra-high cyclic fatigue strength data of the cylinder block steel material. This refers to fatigue life data for ultra-high cycle fatigue. Data points based on Basquin's formula Fitting is performed to obtain the ultra-high cycle fatigue stress-life curve of the cylinder block structure.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process, characterized in that, The method includes the following steps: Step S1: Analyze the key locations in the hydraulic pump cylinder that are prone to fatigue failure, and determine the stress conditions at the key locations in the hydraulic pump cylinder. Step S2: Design the test specimen for ultra-high cycle fatigue test based on the key position geometric parameters of the hydraulic pump cylinder. Step S3: Based on the stress form at key locations and the load-stress ratio, conduct ultra-high cycle fatigue tests on the test specimens; obtain the stress-life relationship of the bimetallic bonded test specimens. Step S4: Based on the allowable safety factor of the hydraulic pump cylinder structure and the stress magnitude at key structural locations, predict the service life of the hydraulic pump cylinder structure.

2. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 1, characterized in that, In step S1, based on the previous cylinder block failure analysis of the aviation hydraulic plunger pump, the cylinder block flow distribution window is selected as the key analysis area; based on finite element analysis, the stress distribution of the bimetallic bonding layer in this key area is analyzed in detail, and different rotation angles are extracted. Maximum stress on the steel layer at the bimetallic joint and minimum stress Used to determine the load ratio in ultrasonic fatigue testing ;in, .

3. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 2, characterized in that, Step S2 of the design process includes: designing an ultra-high cycle fatigue test piece based on the key geometric features of the waist hole to ensure the geometric similarity between the test piece and the waist hole structure; adjusting the length and width dimensions of the test piece based on the finite element method to meet the resonance requirements of the ultrasonic fatigue test at 20kHz, while ensuring the key geometric feature conditions; and strictly processing the test piece according to the processing technology of aviation hydraulic plunger pumps to ensure the consistency of the manufacturing process that may affect the fatigue performance.

4. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 3, characterized in that, Key geometric features include radius Copper layer thickness , waist hole spacing .

5. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 3, characterized in that, The specific acquisition process in step S3 is as follows: Based on the operating environment temperature and load conditions of the aviation hydraulic plunger pump, fatigue tests are conducted using high-temperature ultrasonic fatigue testing equipment to obtain the service environment temperature. T The stress ratio is R Ultra-high cycle fatigue stress-life data at stress levels 3-5. For each stress level, 4-5 specimens are tested, and the stress is... This indicates the magnitude of stress on the steel matrix; analysis of ultra-high cycle fatigue test data. Based on the characteristics, stress-life curves for bimetallic bonding processes were established.

6. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 5, characterized in that, High-temperature ultrasonic fatigue testing was conducted on cylinder block steel materials at a loading frequency of 20 kHz within the range of room temperature to 125 ± 10 °C. to High-temperature and ultra-high-cycle fatigue test under cyclic loading.

7. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 5, characterized in that, The high-temperature ultrasonic fatigue test method uses a high-frequency induction heating device to heat the specimen and uses an infrared thermometer to monitor the temperature of the middle section of the specimen in real time, ultimately achieving rapid fatigue loading under high-temperature conditions.

8. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 5, characterized in that, The prediction process in step S4 is as follows: Based on the stress magnitude of the cylinder block structure simulated by the model, the ultra-high cyclic fatigue strength of the cylinder block is checked, considering the number of dangerous parts in the plunger pump distribution pair and the survival rate requirements. The theoretical ultra-high cycle fatigue life of the curve calculation structure.

9. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 8, characterized in that, The maximum stress at the critical point of the distribution sub-cylinder block waist hole under service conditions was obtained based on simulation analysis. And taking into account the allowable safety factor , obtain structural stress ; to structural stress Substituting the ultra-high cycle fatigue stress-life curve of the cylinder block structure into the curve yields the safe fatigue life of the cylinder block structure. .

10. The method for predicting the ultra-high cycle fatigue life of a hydraulic pump cylinder block using a bimetallic bonding process as described in claim 8, characterized in that, Empirical coefficients are used to ensure the safety and effectiveness of the cylinder block design; the allowable safety factor for the cylinder block structure is based on... It is confirmed that, among them, The allowable safety factor for the cylinder block structure. For the strength safety factor, This is the stress safety factor; (a) Material property uncertainties can be addressed through… Fitting a 95% survival rate curve to eliminate the influence is acceptable. If a 50% survival rate is adopted, it can be taken as follows: ; (b) When both load and stress are very precise, When load and stress are inaccurate and there are impact and high-stress loads, .

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