A hydraulic cylinder bore and mating piece surface hardening method, apparatus, and medium

Abstract

The embodiment of the application discloses a hydraulic cylinder bore and a surface strengthening method, equipment and medium of a matching part, belongs to the technical field of ultrasonic rolling, and solves the problem that a single surface strengthening technology cannot meet the harsh working condition requirement in the prior art. Including, the hydraulic cylinder bore and the matching part are subjected to nitriding treatment, and data monitoring is performed on the nitriding process parameters and the nitriding layer quality parameters; the monitored parameters are analyzed, and the analysis results are synergistically adjusted based on the structural characteristics of the hydraulic cylinder bore and the matching part to obtain reference ultrasonic rolling process parameters; based on the reference ultrasonic rolling process parameters, the ultrasonic surface rolling equipment is controlled to perform surface strengthening treatment on the hydraulic cylinder bore and the matching part; and based on the surface strengthening treatment data, the reference ultrasonic rolling process parameters are feedback adjusted, so that the ultrasonic surface rolling equipment is controlled to construct a strengthening layer on the surface of the hydraulic cylinder bore and the matching part based on the feedback adjusted parameters.

Description

Technical Field

[0001] This application relates to the field of ultrasonic rolling technology, and in particular to a method, equipment and medium for surface strengthening of the inner bore and mating parts of a hydraulic cylinder. Background Technology

[0002] Hydraulic cylinders, as core actuating components in engineering machinery, heavy equipment, and hydraulic systems, endure severe stresses from high pressure, high-frequency reciprocating motion, and high wear loads on their inner bore and mating parts (such as plungers). Hydraulic cylinder bodies are mostly made of materials such as cast iron, and the hardness, wear resistance, and fatigue strength of their inner bore surface directly determine the reliability, service life, and working efficiency of the entire hydraulic system. Under complex working conditions, the inner bore surface of the cylinder is prone to wear failure, fatigue spalling, and loss of fitting precision, leading to hydraulic system leaks, reduced efficiency, and even equipment downtime, resulting in significant maintenance costs and economic losses.

[0003] To address the aforementioned issues, existing technologies typically employ surface strengthening processes to improve the service performance of hydraulic cylinder inner bores. Nitriding is a commonly used technique, which enhances surface hardness and wear resistance by forming a high-hardness nitride layer on the inner bore surface. However, while the nitride layer created by a single nitriding process achieves high hardness, it is also brittle and prone to micropores and other defects, making it susceptible to spalling under high-load impacts, thus becoming a crack initiation point and affecting fatigue strength. On the other hand, ultrasonic surface rolling, as an advanced surface modification method, combines ultrasonic energy with static rolling pressure to introduce intense plastic deformation and residual compressive stress into the material surface, effectively refining grains, reducing surface roughness, and improving fatigue resistance. However, ultrasonic rolling alone offers limited improvement in the deep hardness of the material, making it difficult to meet the stringent high wear resistance requirements of hydraulic cylinder inner bores.

[0004] To overcome the limitations of a single process, existing technologies have gradually adopted a simple sequential combination of nitriding and ultrasonic rolling for process composite. However, it is difficult to control the balance between nitriding and ultrasonic surface rolling processes in a simple combination, which can easily lead to the peeling off of the brittle nitriding layer due to over-processing or the inability to eliminate defects in the nitriding layer due to insufficient processing. Summary of the Invention

[0005] This application provides a surface strengthening method, equipment, and medium for the inner bore and mating parts of a hydraulic cylinder, which solves the following technical problem: In the prior art, a simple sequential combination of nitriding and ultrasonic rolling is used for process composite, but the simple combination makes it difficult to grasp the balance between nitriding and ultrasonic surface rolling processes, which can easily lead to the peeling off of the brittle nitriding layer due to over-processing or the inability to eliminate nitriding layer defects due to insufficient processing.

[0006] The embodiments of this application adopt the following technical solutions:

[0007] This application provides a method for surface strengthening of the inner bore and mating parts of a hydraulic cylinder. The method includes: performing nitriding treatment on the inner bore and mating parts of the hydraulic cylinder, and monitoring the nitriding process parameters and nitriding layer quality parameters; analyzing the monitored nitriding process parameters and nitriding layer quality parameters, and coordinating the analysis results based on the structural characteristics of the inner bore and mating parts of the hydraulic cylinder to obtain reference ultrasonic rolling process parameters; controlling an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder based on the reference ultrasonic rolling process parameters; collecting surface strengthening treatment data, and adjusting the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling device to construct a strengthening layer on the surface of the inner bore and mating parts of the hydraulic cylinder based on the adjusted parameters.

[0008] In one implementation of this application, the monitored nitriding process parameters and nitrided layer quality parameters are analyzed, and the analysis results are synergistically adjusted based on the structural characteristics of the hydraulic cylinder inner bore and mating parts to obtain reference ultrasonic rolling process parameters. Specifically, this includes: determining the nitrided layer quality grade based on a pre-set nitrided layer quality grade evaluation system, nitriding process parameters, and nitrided layer quality parameters; wherein the pre-set nitrided layer quality grade evaluation system includes at least one of nitrided layer defect density, nitrided layer hardness gradient distribution, and nitrided layer compound uniformity; determining the basic process parameters for ultrasonic rolling based on the nitrided layer quality grade in a pre-set parameter mapping table; dividing the hydraulic cylinder inner bore and mating parts into multiple functional areas based on the structural characteristics of the hydraulic cylinder inner bore and mating parts; wherein the structural characteristics include at least one of working condition characteristics and structural stress distribution; and adjusting the basic process parameters for ultrasonic rolling based on the characteristics of the functional areas to output reference ultrasonic rolling process parameters.

[0009] In one implementation of this application, the basic process parameters are adjusted based on the characteristics of the functional regions to output reference ultrasonic rolling process parameters. Specifically, this includes: determining a first compensation adjustment parameter corresponding to the basic process parameters of ultrasonic rolling based on the geometric structural features corresponding to each functional region; wherein the geometric structural features include at least one of wall thickness variation rate, surface complexity, and edge transition features; determining a second compensation adjustment parameter corresponding to the basic process parameters of ultrasonic rolling based on the differences in compound layer content and residual stress distribution state corresponding to each functional region after nitriding; dividing historical process data into multiple historical optimization clusters according to functional region type in a historical database; wherein each historical optimization cluster corresponds to an optimal parameter fusion scheme; determining the similarity between the current functional region to be processed and each historical optimization cluster; and dynamically adjusting the fusion weights of the first compensation parameter and the second compensation parameter based on the optimal parameter fusion scheme corresponding to the historical optimization cluster with the highest similarity to obtain the reference ultrasonic rolling process parameters.

[0010] In one implementation of this application, surface strengthening treatment data is collected, and reference ultrasonic rolling process parameters are adjusted based on the collected data. Specifically, this includes: during the ultrasonic rolling stage, real-time acquisition of feedback data during the rolling process; wherein the feedback data includes at least one of acoustic emission signal, surface temperature, and rolling force; when the acoustic emission signal indicates that the surface of the hydraulic cylinder inner bore and mating parts is in a preset plastic deformation stage and the surface temperature is maintained within a preset range, the current reference ultrasonic rolling process parameters are determined to be the optimal fusion parameters; if the acoustic emission signal indicates that the surface of the hydraulic cylinder inner bore and mating parts exhibits brittle fracture characteristics, the reference ultrasonic rolling process parameters are adjusted using a first feedback method; if the surface temperature of the hydraulic cylinder inner bore and mating parts is greater than a preset temperature range, the reference ultrasonic rolling process parameters are adjusted using a second feedback method.

[0011] In one implementation of this application, if the acoustic emission signal indicates that brittle fracture characteristics appear on the surface of the inner bore of the hydraulic cylinder and the mating parts, a first feedback adjustment will be made with reference to the ultrasonic rolling process parameters. Specifically, this includes: determining the signal state corresponding to the brittle fracture characteristics based on the acoustic emission signal; wherein the signal state includes at least one of the instantaneous value of the signal amplitude, the signal energy release rate, and the peak value of the power spectral density; determining the brittle fracture severity level corresponding to the ultrasonic rolling stage based on the frequency of the signal state corresponding to the brittle fracture characteristics; and reducing the rolling force and feed rate corresponding to the ultrasonic rolling process parameters by different percentages based on different brittle fracture severity levels.

[0012] In one implementation of this application, if the surface temperature of the hydraulic cylinder inner bore and mating parts is greater than a preset temperature range, a second feedback adjustment will be performed with reference to the ultrasonic rolling process parameters. Specifically, this includes: during the ultrasonic rolling process, calculating the real-time ratio of heat input power to heat dissipation power based on the temperature corresponding to the surface of the hydraulic cylinder inner bore and mating parts and the reference ultrasonic rolling process parameters; if the real-time ratio is greater than a preset ratio threshold and the temperature is greater than a preset temperature threshold, then it is determined that the surface temperature is overheated; based on the difference between the real-time ratio and the preset temperature threshold, reducing the rolling force corresponding to the reference ultrasonic rolling process parameters by different proportional values, and increasing the feed rate and ultrasonic amplitude by corresponding proportional values.

[0013] In one implementation of this application, after collecting surface strengthening treatment data and adjusting the reference ultrasonic rolling process parameters based on the collected data, the method further includes: saving the critical process parameters corresponding to the transition of the acoustic emission signal from the preset plastic deformation stage to the abnormal state during ultrasonic rolling, and constructing a safety boundary database; when responding to parameter control commands of the same functional area type in subsequent responses, using the safety boundary database as a constraint, optimization is performed based on the reference ultrasonic rolling process parameters to adjust the error between the process parameters and the safety boundary to a preset error range, so as to obtain an optimized parameter combination.

[0014] In one implementation of this application, controlling an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of a hydraulic cylinder specifically includes: after the rolling tool head of the ultrasonic rolling device contacts the surface of the inner bore and mating parts of the hydraulic cylinder, applying a first rolling force and a first feed rate for pre-processing in the initial section of the rolling path; when the amplitude fluctuation rate of the acoustic emission signal is detected to be less than a preset amplitude frequency threshold, switching to the strengthening rolling stage, applying a second rolling force and a second feed rate corresponding to the ultrasonic rolling process parameters; when the residual stress is within a preset target range, the strengthening rolling is completed, and a third rolling force and a third feed rate are applied for finishing rolling; wherein, the first rolling force is less than the third rolling force, and the third rolling force is less than the second rolling force, the third feed rate is less than the second feed rate, and the second feed rate is less than the first feed rate.

[0015] This application provides a surface strengthening device for the inner bore and mating parts of a hydraulic cylinder, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to: perform nitriding treatment on the inner bore and mating parts of the hydraulic cylinder, and monitor the nitriding process parameters and nitriding layer quality parameters corresponding to the nitrided layer; analyze the monitored nitriding process parameters and nitrided layer quality parameters, and coordinately adjust the analysis results based on the structural characteristics of the inner bore and mating parts of the hydraulic cylinder to obtain reference ultrasonic rolling process parameters; control an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder based on the reference ultrasonic rolling process parameters; collect surface strengthening treatment data, and perform feedback adjustment on the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling device to construct a strengthening layer on the surface of the inner bore and mating parts of the hydraulic cylinder based on the parameters after feedback adjustment.

[0016] This application provides a non-volatile computer storage medium storing computer-executable instructions. These instructions are configured to: perform nitriding treatment on the inner bore and mating parts of a hydraulic cylinder, and monitor the nitriding process parameters and nitriding layer quality parameters corresponding to the nitrided layer; analyze the monitored nitriding process parameters and nitriding layer quality parameters, and coordinately adjust the analysis results based on the structural characteristics of the inner bore and mating parts of the hydraulic cylinder to obtain reference ultrasonic rolling process parameters; control an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder based on the reference ultrasonic rolling process parameters; collect surface strengthening treatment data, and perform feedback adjustment on the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling device to construct a strengthening layer on the surface of the inner bore and mating parts of the hydraulic cylinder based on the parameters after feedback adjustment.

[0017] The above-mentioned technical solutions adopted in this application embodiment can achieve the following beneficial effects: This application embodiment, by synergistically processing nitriding and ultrasonic rolling, dynamically generates optimal rolling parameters based on the mapping between real-time quality data of the nitrided layer and the structural characteristics of the cylinder functional area. The nitriding process forms a nitrided layer in the inner hole of the cylinder, providing a foundation for wear resistance. Ultrasonic rolling causes plastic flow of the surface metal through high-frequency impact, filling the micropores of the nitrided layer, refining the grains, and introducing residual compressive stress, which significantly improves toughness while increasing surface hardness. Secondly, this application embodiment, by introducing a real-time feedback mechanism that integrates multi-source information such as acoustic emission, temperature, and force signals, can identify the processing state and adaptively adjust parameters, improving processing efficiency while ensuring the quality of the reinforced layer, and achieving a synergistic improvement in quality, efficiency, and reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0019] Figure 1 A flowchart illustrating a surface strengthening method for the inner bore and mating parts of a hydraulic cylinder provided in this application embodiment;

[0020] Figure 2 A comparison diagram of surface hardness before and after ultrasonic surface rolling treatment is provided for an embodiment of this application;

[0021] Figure 3 A comparison diagram of surface roughness before and after ultrasonic surface rolling treatment is provided for an embodiment of this application;

[0022] Figure 4 This is a schematic diagram of the surface strengthening device for the inner bore and mating parts of a hydraulic cylinder, provided as an embodiment of this application.

[0023] Figure label:

[0024] 200: Surface strengthening equipment for the inner bore and mating parts of a hydraulic cylinder; 201: Processor; 202: Memory. Detailed Implementation

[0025] This application provides a method, equipment, and medium for surface strengthening of the inner bore and mating parts of a hydraulic cylinder.

[0026] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0027] Figure 1 This is a flowchart illustrating a surface strengthening method for the inner bore and mating parts of a hydraulic cylinder, as provided in an embodiment of this application. Figure 1 As shown, the surface strengthening method for the inner bore and mating parts of the hydraulic cylinder includes the following steps:

[0028] Step 101: Nitride the inner bore and mating parts of the hydraulic cylinder, and monitor the nitriding process parameters and quality parameters of the nitrided layer.

[0029] In one implementation of this application, a hydraulic cylinder and its mating components (such as a plunger) are installed in a controlled atmosphere nitriding furnace, and basic parameters for the nitriding process are set. For example, the process parameters could be: the nitriding temperature controlled within the range of 520°C to 560°C, and the holding time set to 4 to 6 hours. During the nitriding process, temperature fluctuations at multiple points within the furnace are monitored and recorded in real time using thermocouples integrated into the furnace body. Simultaneously, changes in ammonia flow rate and atmosphere composition are monitored using a flow meter and a gas analyzer. These data are continuously collected and stored as basic nitriding process parameters.

[0030] After nitriding, once the workpiece has cooled to room temperature, at least nine measurement points are selected on the inner bore surface of the cylinder using a grid method to detect and record the thickness and uniformity of the nitrided layer. The hardness is also tested to obtain a hardness gradient curve, and the phase composition of the compound layer is analyzed using X-ray diffraction. The detected thickness, hardness gradient, compound phase content, and uniformity are used to construct the nitrided layer quality parameters.

[0031] Step 102: Analyze the monitored nitriding process parameters and nitrided layer quality parameters, and adjust the analysis results in a coordinated manner based on the structural characteristics of the hydraulic cylinder inner bore and mating parts to obtain reference ultrasonic rolling process parameters.

[0032] In one implementation of this application, the nitriding layer quality grade is determined based on a pre-set nitriding layer quality grade evaluation system, nitriding process parameters, and nitriding layer quality parameters. The pre-set nitriding layer quality grade evaluation system includes at least one of the following: nitriding layer defect density, nitriding layer hardness gradient distribution, and nitriding layer compound uniformity. Based on the nitriding layer quality grade, the basic process parameters for ultrasonic rolling are determined in a pre-set parameter mapping table. Based on the structural characteristics of the hydraulic cylinder inner bore and mating parts, the hydraulic cylinder inner bore and mating parts are divided into multiple functional regions. The structural characteristics include at least one of the following: working condition characteristics and structural stress distribution. Based on the characteristics of the functional regions, the basic process parameters for ultrasonic rolling are adjusted to output reference ultrasonic rolling process parameters.

[0033] Specifically, based on the test data obtained after nitriding, a pre-set nitriding layer quality grade evaluation system is applied for comprehensive quantitative assessment. Specifically, scanning electron microscope images of the sampling area are processed using image analysis software to calculate the number of micropores and the total crack length per unit area, yielding the defect density index. Data points tested along the depth direction using a microhardness tester are fitted with a hardness decay curve, and its slope is calculated as the hardness gradient coefficient. The compound phase content at different test points is analyzed using electron probe microanalysis or X-ray diffraction, and the ratio of its standard deviation to the average value is calculated as the compound homogeneity variation coefficient. The measured values ​​of these three key indicators are compared with preset grade threshold ranges, and a weighted average is used to finally output the nitriding layer quality grade.

[0034] Using the nitriding layer quality grade as input, a pre-defined parameter mapping table is queried. This mapping table is pre-established through extensive process experiments, and its structure is as follows: rows correspond to different quality grades, and columns correspond to key ultrasonic rolling parameters such as rolling pressure, feed rate, amplitude, and number of rolling passes. By querying this parameter mapping table, the basic process parameters for the overall quality of the current nitriding layer are output.

[0035] Furthermore, in this embodiment, the functional areas are finely divided using a three-dimensional CAD model of the hydraulic cylinder and actual working loads. Specifically, using finite element analysis software, rated working pressure and boundary conditions are applied to calculate the equivalent stress distribution cloud map of the cylinder's inner bore, and areas with a stress concentration factor Kt > 2.5 are identified as stress concentration zones. The pressure-velocity (PV) value distribution during the piston's reciprocating motion is calculated, and areas with PV values ​​consistently higher than a set threshold are classified as high-wear zones. Finally, the different functional areas of the cylinder's inner bore and mating parts are labeled.

[0036] Furthermore, based on the characteristics of the functional regions, the basic process parameters are adjusted to output reference ultrasonic rolling process parameters. This step includes determining the first compensation adjustment parameter corresponding to the basic process parameters of ultrasonic rolling based on the geometric structural features corresponding to each functional region; wherein, the geometric structural features include at least one of the following: wall thickness change rate, surface complexity, and edge transition features. Based on the differences in compound layer content and residual stress distribution state corresponding to each functional region after nitriding, the second compensation adjustment parameter corresponding to the basic process parameters of ultrasonic rolling is determined. In the historical database, historical process data is divided into multiple historical optimization clusters according to functional region type; wherein, each historical optimization cluster corresponds to an optimal parameter fusion scheme. The similarity between the current functional region to be processed and each historical optimization cluster is determined. Based on the optimal parameter fusion scheme corresponding to the historical optimization cluster with the highest similarity, the fusion weights of the first compensation parameter and the second compensation parameter are dynamically adjusted to obtain the reference ultrasonic rolling process parameters.

[0037] Specifically, for each functional area, corresponding geometric features are extracted from its 3D CAD model. The wall thickness variation rate of this area is calculated, i.e., the thickness gradient between adjacent mesh cells, and its surface complexity is evaluated using a surface curvature analysis algorithm, with the average and standard deviation of curvature as quantification indicators. For edge transition areas, the radius data of the transition arc is obtained to evaluate the edge transition characteristics. The obtained quantified geometric feature values ​​are compared with a first preset lookup table, which includes different quantified geometric feature values ​​and corresponding compensation coefficients. For example, for areas with a large wall thickness variation rate, a negative rolling pressure compensation coefficient (e.g., -10%) is output; for areas with high surface complexity, a feed rate compensation coefficient is output. Based on the parameter adjustment amount obtained from the lookup, the first compensation adjustment parameter is obtained.

[0038] The second compensation adjustment parameter is calculated based on the measured material properties data of the functional area after nitriding. If the compound layer content in the current area is higher than the average, a compensation instruction is generated to slightly reduce the rolling pressure to prevent the hard phase from peeling off. Simultaneously, based on the residual stress distribution in the area measured by an X-ray stress analyzer, if there is high tensile stress, a compensation instruction is generated to introduce compressive stress, increase the rolling pressure, or increase the number of rolling cycles. Furthermore, the specific adjustment parameters corresponding to different compensation instructions can be queried through a second preset lookup table. This table includes different material property data and the corresponding adjustment parameters for each material property data. The parameter adjustment amount calculated based on the nitrided layer material state to optimize surface performance is the second compensation adjustment parameter.

[0039] Furthermore, the historical database is accessed to filter out all successful processing case data similar to the current workpiece material and nitriding process. Using a clustering algorithm, the geometric and material feature vectors of the functional areas in each case are used as clustering features to divide these historical cases into several historical optimization clusters. Cases within each cluster are similar in geometric and material features, and the specific weighted fusion scheme of the first and second compensation parameters used in their processing is verified as optimal. The geometric and material feature vectors of the current functional area to be processed are combined into a comprehensive feature vector. The similarity between this vector and each historical optimization cluster is calculated. The historical optimization cluster with the highest similarity is selected as the best reference. The successful parameter fusion scheme corresponding to this cluster, i.e., the specific weighted ratio of the first and second compensation parameters, is used to weight and fuse the two calculated compensation adjustment parameters. The fusion result is then applied to the basic process parameters to finally generate reference ultrasonic rolling process parameters for this area. For example, the process parameters for ultrasonic surface rolling corresponding to the inner bore of a hydraulic cylinder can be: static pressure 300-600N, ultrasonic frequency 25-35kHz, ultrasonic amplitude 5-15μm, feed rate 0.05-0.15mm / r, rolling speed 800-1200mm / min, and rolling twice. The process parameters for the plunger component adapted to the inner bore of the hydraulic cylinder can be: static pressure 200-500N, ultrasonic frequency 25-35kHz, ultrasonic amplitude 3-12μm, feed rate 0.05-0.15mm / r, rolling speed 800-1200mm / min, and rolling twice.

[0040] Step 103: Based on the reference ultrasonic rolling process parameters, control the ultrasonic surface rolling equipment to perform surface strengthening treatment on the inner bore of the hydraulic cylinder and mating parts.

[0041] In one implementation of this application, the reference ultrasonic rolling process parameters and the three-dimensional digital model of the hydraulic cylinder body generated for each functional area are imported into a CNC programming system. This system automatically generates an optimized toolpath based on the geometric trajectory of the cylinder's inner bore, ensuring smooth processing at path turning points or functional area transitions to avoid sudden changes in speed or pressure. Subsequently, the generated CNC machining program is downloaded to the CNC system of the ultrasonic surface rolling equipment. The operator installs and calibrates a suitable rolling tool head, clamps the nitrided hydraulic cylinder workpiece onto the machine tool table or rotary center, and then slowly contacts the rolling tool head to a pre-set tool setting reference surface at the cylinder's inner bore port, setting this point as the Z-axis zero point. The X and Y-axis zero points are set in the same way, establishing a workpiece coordinate system and laying the foundation for subsequent precise automatic machining. The CNC program is started, and the equipment begins automatic machining according to the preset path and parameters.

[0042] Step 104: Collect surface strengthening treatment data, and adjust the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling equipment to build a strengthening layer on the surface of the hydraulic cylinder inner hole and mating parts based on the adjusted parameters.

[0043] In one implementation of this application, during the ultrasonic rolling stage, feedback data is collected in real time during the rolling process. The feedback data includes at least one of acoustic emission signal, surface temperature, and rolling force. When the acoustic emission signal indicates that the surface of the hydraulic cylinder inner bore and mating parts is in a preset plastic deformation stage and the surface temperature is maintained within a preset range, the current reference ultrasonic rolling process parameters are determined to be the optimal fusion parameters. If the acoustic emission signal indicates that the surface of the hydraulic cylinder inner bore and mating parts exhibits brittle fracture characteristics, the reference ultrasonic rolling process parameters are adjusted using a first feedback method. If the surface temperature of the hydraulic cylinder inner bore and mating parts exceeds a preset temperature range, the reference ultrasonic rolling process parameters are adjusted using a second feedback method.

[0044] Specifically, during ultrasonic rolling, a multi-sensor system integrated into the rolling tool head begins operation. Acoustic emission sensors capture elastic stress waves generated by material deformation and crack propagation in real time, converting them into electrical signals for transmission. Simultaneously, a non-contact infrared thermometer transmits the surface temperature in real time. A force sensor mounted on the shank of the rolling tool monitors changes in the normal rolling force in real time. Data acquisition software within the industrial control computer synchronizes these three signals, providing a real-time data stream for subsequent analysis.

[0045] Furthermore, this application embodiment performs time-domain and frequency-domain analysis on the acoustic emission signal. When the time-domain signal is continuous, the amplitude is stable within a preset amplitude range, such as 60-80 dB, and the frequency-domain energy is mainly concentrated in a preset frequency range, such as 100 kHz-200 kHz, it is determined to be in the ideal plastic deformation stage. Simultaneously, if the surface temperature is within a preset safe process window, for example, 150℃±20℃. When these two conditions are simultaneously met and maintained for a certain period, the currently executing reference ultrasonic rolling process parameters are determined to be the optimal fusion parameters, and a good status signal is sent to the operation interface. At the same time, the parameter combination is recorded as instantaneous data of a successful case in the historical database.

[0046] Furthermore, if the acoustic emission signal indicates brittle fracture characteristics on the surface of the hydraulic cylinder's inner bore and mating parts, a first feedback adjustment will be made based on the ultrasonic rolling process parameters. This process includes determining the signal state corresponding to the brittle fracture characteristics based on the acoustic emission signal; wherein the signal state includes at least one of the instantaneous value of the signal amplitude, the signal energy release rate, and the peak value of the power spectral density. Based on the frequency of the signal state corresponding to the brittle fracture characteristics, the severity level of brittle fracture corresponding to the ultrasonic rolling stage is determined. Based on different severity levels of brittle fracture, the rolling force and feed rate corresponding to the ultrasonic rolling process parameters are reduced by different percentages.

[0047] Specifically, after the acoustic emission sensor acquires the signal, it is analyzed to identify brittle fracture characteristics. First, the instantaneous amplitude of the signal is detected; when it exceeds 150% of the previous rolling average amplitude, it is marked as an event. Second, the energy release rate of the event is calculated, i.e., the square integral of the signal divided by the duration; when this value exceeds 200% of the average energy of a typical plastic deformation event, it is considered a high-energy event. Finally, a fast Fourier transform is performed on the signal to analyze its power spectral density. If a significant isolated peak appears in the high-frequency range of 300kHz to 400kHz, it is confirmed to have the spectral characteristics of brittle fracture. When an acoustic emission event simultaneously meets the three conditions of high amplitude, high energy release rate, and high-frequency peak, a brittle fracture characteristic event is finally confirmed. The brittle fracture characteristic events confirmed in step one are continuously monitored and recorded. The total number of brittle events occurring within a fixed time window (e.g., 60 seconds) is counted. The severity level of the brittle fracture is determined based on the event frequency. For example, fewer than 5 cycles are defined as slightly brittle, indicating only sporadic brittleness; between 5 and 15 cycles are defined as moderately brittle, indicating a significantly increased risk of brittleness; and between 15 and 15 cycles, or continuous brittle events, are defined as severely brittle, indicating the material is in a highly brittle state. Based on the severity level, a preset first feedback adjustment strategy is executed. For slightly brittle, the current rolling pressure parameter is reduced within a first rolling pressure ratio range, and the feed rate is reduced within a first rate ratio range; for moderately brittle, the current rolling pressure parameter is reduced within a second rolling pressure ratio range, and the feed rate is reduced within a second rate ratio range; for severely brittle, the current rolling pressure parameter is reduced within a third rolling pressure ratio range, and the feed rate is reduced within a third rate ratio range. For example, for slightly brittle, the current rolling pressure parameter is reduced by 10% to 15%, while the feed rate is reduced by 5% to 8%, with the aim of slightly reducing the load and giving the material more time to deform. For moderately brittle materials, reduce the rolling pressure by 20% to 25% and the feed rate by 10% to 15% to mitigate mechanical impact. For severely brittle materials, implement emergency intervention by drastically reducing the rolling pressure to 50% of its current value and the feed rate to 30%, and maintaining this low-parameter operation for at least 30 seconds to stabilize the material and prevent further defect propagation.

[0048] Furthermore, if the surface temperature of the hydraulic cylinder inner bore and mating parts exceeds a preset temperature range, a second feedback adjustment will be performed with reference to the ultrasonic rolling process parameters. This step includes calculating the real-time ratio of heat input power to heat dissipation power based on the corresponding temperatures of the hydraulic cylinder inner bore and mating parts surfaces and the reference ultrasonic rolling process parameters during the ultrasonic rolling process. If the real-time ratio exceeds a preset ratio threshold and the temperature exceeds a preset temperature threshold, then surface overheating is determined. Based on the difference between the real-time ratio and the preset temperature threshold, the rolling force corresponding to the reference ultrasonic rolling process parameters will be reduced by different proportional values, and the feed rate and ultrasonic amplitude will be increased by corresponding proportional values.

[0049] Specifically, during ultrasonic rolling, the instantaneous heat input power is calculated based on reference ultrasonic rolling process parameters such as current rolling pressure, feed rate, and ultrasonic power, combined with the material deformation work-heat conversion coefficient. Simultaneously, the heat dissipation power rate is estimated based on real-time surface temperature, ambient temperature, and the equivalent interfacial thermal resistance estimated from the nitrided layer quality parameters. Subsequently, the real-time ratio of heat input power to heat dissipation power rate is calculated. When the surface temperature exceeds a preset temperature threshold and the real-time ratio remains greater than a preset imbalance threshold, the current state is diagnosed as heat accumulation-type overheating, rather than a transient temperature fluctuation. Based on the severity of the diagnosed heat accumulation-type overheating (mild, moderate, or severe), specific parameter adjustments are calculated. In this embodiment, the severity of overheating is determined by two factors: the difference between the surface temperature exceeding the threshold and the difference between the heat imbalance ratio exceeding the threshold. These two differences are mapped to a preset adjustment coefficient table to determine the adjustment ratio for the reference ultrasonic rolling process parameters. For example, for mild overheating, the determined adjustment instructions are: reduce the rolling pressure by 10%, increase the feed rate by 15%, and increase the ultrasonic amplitude by 8%. For moderate or severe overheating, the adjustment range is increased proportionally, such as reducing the rolling pressure by 15%-25%, increasing the feed rate by 20%-35%, and increasing the ultrasonic amplitude by 10%-18%. This embodiment of the application reduces the mechanical deformation energy, which generates the most heat, by reducing the rolling pressure; shortens the local heating time by increasing the feed rate, utilizing the workpiece body as a heat sink; and enhances the activation efficiency of high-frequency vibration energy on the material surface by increasing the ultrasonic amplitude, partially replacing the role of mechanical work, thereby optimizing thermal management while maintaining a roughly constant total energy input.

[0050] In one implementation of this application, after collecting surface strengthening treatment data and adjusting the reference ultrasonic rolling process parameters based on the collected data, the method further includes saving the critical process parameters corresponding to the transition of the acoustic emission signal from a preset plastic deformation stage to an abnormal state during ultrasonic rolling, thus constructing a safety boundary database. In subsequent responses to parameter control commands of the same functional area type, the safety boundary database is used as a constraint to optimize the reference ultrasonic rolling process parameters, adjusting the error between the process parameters and the safety boundary to a preset error range to obtain an optimized parameter combination.

[0051] Specifically, during each ultrasonic rolling process, a data recording command is immediately triggered the moment the acoustic emission signal characteristics deviate from the stable, preset plastic deformation stage and an abnormal state first appears. This command records a complete set of process parameters being executed at that moment, along with the type of the current functional area and the type of the abnormal state, and stores them in a safety boundary database. Each record in this database represents a safety critical point for the process parameters of the corresponding functional area under specific conditions. When it is necessary to generate or adjust reference ultrasonic rolling process parameters for the same type of functional area, the safety boundary database is queried first. All historical critical parameter records matching the functional area identifier and material type are retrieved from this database, and statistical methods are used to determine the safety boundary range of each process parameter. Subsequently, starting with the initial reference process parameters, a parameter optimization algorithm is initiated under the premise of ensuring processing efficiency and constrained by the safety boundary. The goal of this algorithm is to proactively adjust the preset process parameters to maintain a preset safety margin with respect to the safety boundary, thereby generating an optimized parameter combination that is both efficient and far from abnormal risks.

[0052] In one implementation of this application, controlling an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of a hydraulic cylinder includes: after the rolling tool head of the ultrasonic rolling device contacts the surface of the inner bore and mating parts of the hydraulic cylinder, applying a first rolling force and a first feed rate for pre-processing in the initial section of the rolling path. When the amplitude fluctuation rate of the acoustic emission signal is detected to be less than a preset amplitude frequency threshold, switching to the strengthening rolling stage, applying a second rolling force and a second feed rate corresponding to the ultrasonic rolling process parameters. When the residual stress is within a preset target range, the strengthening rolling is completed, and a third rolling force and a third feed rate are applied for finishing rolling. The first rolling force is less than the third rolling force, and the third rolling force is less than the second rolling force; the third feed rate is less than the second feed rate, and the second feed rate is less than the first feed rate.

[0053] Specifically, in this embodiment, after the ultrasonic rolling tool head contacts the surface of the hydraulic cylinder inner bore and establishes initial pressure, the process enters the pretreatment stage. The CNC system controls the equipment to apply a first rolling force and a first feed rate at the beginning of the rolling path. The purpose of this stage is to quickly flatten the microscopic protrusions on the surface at a relatively high speed and low pressure, eliminate vibrations that may be caused by uneven initial contact, and achieve a stable contact state between the tool and the workpiece surface. During the pretreatment stage, the acoustic emission monitoring system continues to operate and calculates the amplitude fluctuation rate of the acoustic emission signal in real time. When the system detects that the amplitude fluctuation rate is lower than a preset amplitude fluctuation rate threshold, it determines that the surface has reached a stable state. The system immediately sends a command to the CNC system to switch the process parameters from the pretreatment stage to the enhanced rolling stage.

[0054] Furthermore, in the strengthening rolling stage, the CNC system executes the reference ultrasonic rolling process parameters, namely, applying a second rolling pressure and a second feed rate, and monitors the surface stress value in real time using a residual stress measuring instrument. When the monitored residual stress value reaches and stabilizes within the preset target range, it indicates that the main strengthening target has been achieved. Afterwards, the finishing rolling stage begins, in which a third rolling pressure and a third feed rate are applied. In this embodiment, the third rolling pressure is greater than the first rolling pressure but less than the second rolling pressure; the third feed rate is less than the second feed rate. The purpose is to smooth the surface layer, which has undergone severe plastic deformation, with moderate pressure, further reducing surface roughness, sealing microcracks that may have occurred in the main strengthening stage, and obtaining a smoother, denser final surface. After the finishing rolling covers the entire processing area, the equipment automatically retracts, and the entire strengthening process ends.

[0055] The ultrasonic surface rolling process in this embodiment does not change the material composition. Based on material preparation, it refines the grains through ultrasonic energy, constructing a gradient plastic deformation and hardening layer to improve the wear resistance and fatigue resistance of the component surface. The nitriding process proposed in this embodiment forms hard phases such as CrN and FeN in the cylinder body pores, providing a foundation for wear resistance; ultrasonic rolling causes plastic flow in the surface metal through high-frequency impact, filling the micropores of the nitrided layer, refining the grains, and introducing residual compressive stress, thus solving the problem of the nitrided layer being hard and brittle.

[0056] Figure 2 A comparison diagram of surface hardness before and after ultrasonic surface rolling treatment is provided for an embodiment of this application, such as... Figure 2 As shown in the figure, the horizontal axis represents the sample type, and the vertical axis represents the surface hardness. This figure demonstrates that, for different sample types, the surface hardness of the material subjected to ultrasonic surface rolling is higher than that of the untreated substrate. Figure 3 A surface roughness comparison diagram before and after ultrasonic surface rolling treatment is provided for an embodiment of this application, such as... Figure 3As shown in the figure, the horizontal axis represents the sample type, and the vertical axis represents the surface roughness. This figure demonstrates that, for different sample types, the surface roughness of the material subjected to ultrasonic surface rolling is lower than that of the untreated substrate.

[0057] Figure 4 This is a schematic diagram of a surface strengthening device for the inner bore and mating parts of a hydraulic cylinder, provided as an embodiment of this application. Figure 4 As shown, a surface strengthening device 200 for the inner bore and mating parts of a hydraulic cylinder includes: at least one processor 201; and a memory 202 communicatively connected to the at least one processor 201. The memory 202 stores instructions executable by the at least one processor 201, which, when executed, enable the at least one processor 201 to: perform nitriding treatment on the inner bore and mating parts of the hydraulic cylinder, and monitor the nitriding process parameters and nitriding layer quality parameters corresponding to the nitrided layer; analyze the monitored nitriding process parameters and nitrided layer quality parameters, and coordinately adjust the analysis results based on the structural characteristics of the inner bore and mating parts of the hydraulic cylinder to obtain reference ultrasonic rolling process parameters; control an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder based on the reference ultrasonic rolling process parameters; collect surface strengthening treatment data, and adjust the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling device to construct a strengthening layer on the surface of the inner bore and mating parts of the hydraulic cylinder based on the adjusted parameters.

[0058] This application provides a non-volatile computer storage medium storing computer-executable instructions. These instructions are configured to: perform nitriding treatment on the inner bore and mating parts of a hydraulic cylinder, and monitor the nitriding process parameters and nitriding layer quality parameters corresponding to the nitrided layer; analyze the monitored nitriding process parameters and nitriding layer quality parameters, and coordinately adjust the analysis results based on the structural characteristics of the inner bore and mating parts of the hydraulic cylinder to obtain reference ultrasonic rolling process parameters; control an ultrasonic surface rolling device to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder based on the reference ultrasonic rolling process parameters; collect surface strengthening treatment data, and perform feedback adjustment on the reference ultrasonic rolling process parameters based on the collected data, so as to control the ultrasonic surface rolling device to construct a strengthening layer on the surface of the inner bore and mating parts of the hydraulic cylinder based on the parameters after feedback adjustment.

[0059] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of apparatus, devices, and non-volatile computer storage media are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0060] The above descriptions are merely embodiments of this application and are not intended to limit the scope of this application. For those skilled in the art, various modifications and variations can be made to the embodiments of this application. These modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions in the embodiments of this application.

Claims

1. A method for surface strengthening of the inner bore and mating parts of a hydraulic cylinder, characterized in that, The method includes: Nitriding treatment is performed on the inner bore and mating parts of the hydraulic cylinder, and data monitoring is conducted on the nitriding process parameters and nitriding quality parameters corresponding to the nitriding layer. The monitored nitriding process parameters and nitrided layer quality parameters are analyzed, and the analysis results are collaboratively adjusted based on the structural characteristics of the hydraulic cylinder inner bore and mating parts to obtain reference ultrasonic rolling process parameters. Specifically, this includes: determining the nitrided layer quality grade based on a pre-set nitrided layer quality grade evaluation system, the nitriding process parameters, and the nitrided layer quality parameters; wherein the pre-set nitrided layer quality grade evaluation system includes at least one of nitrided layer defect density, nitrided layer hardness gradient distribution, and nitrided layer compound uniformity; determining the basic process parameters for ultrasonic rolling based on the nitrided layer quality grade in a pre-set parameter mapping table; dividing the hydraulic cylinder inner bore and mating parts into multiple functional regions based on the structural characteristics of the hydraulic cylinder inner bore and mating parts; wherein the structural characteristics include at least one of working condition characteristics and structural stress distribution; and adjusting the basic process parameters for ultrasonic rolling based on the characteristics of the functional regions to output the reference ultrasonic rolling process parameters. Based on the aforementioned reference ultrasonic rolling process parameters, the ultrasonic surface rolling equipment is controlled to perform surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder. Surface strengthening treatment data is collected, and the reference ultrasonic rolling process parameters are adjusted based on the collected data. The ultrasonic surface rolling equipment is then used to construct a strengthening layer on the surface of the inner bore of the hydraulic cylinder and the mating parts based on the adjusted parameters.

2. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 1, characterized in that, The adjustment of the basic process parameters based on the characteristics of the functional region to output the reference ultrasonic rolling process parameters specifically includes: Based on the geometric structural features corresponding to each functional area, the first compensation adjustment parameters corresponding to the basic process parameters of ultrasonic rolling are determined; wherein, the geometric structural features include at least one of the following: wall thickness change rate, surface complexity, and edge transition features; Based on the differences in compound layer content and residual stress distribution in each functional region after nitriding, the second compensation adjustment parameter corresponding to the basic process parameters of ultrasonic rolling is determined. In the historical database, historical process data is divided into multiple historical optimization clusters according to functional area type; each of the historical optimization clusters corresponds to the optimal parameter fusion scheme. Determine the similarity between the current functional region to be processed and each historical optimization cluster. Based on the optimal parameter fusion scheme corresponding to the historical optimization cluster with the highest similarity, dynamically adjust the fusion weights of the first compensating parameter and the second compensating parameter to obtain the reference ultrasonic rolling process parameters.

3. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 1, characterized in that, The process of collecting surface strengthening treatment data and adjusting the reference ultrasonic rolling process parameters based on the collected data specifically includes: During the ultrasonic rolling stage, feedback data is collected in real time during the rolling process; wherein, the feedback data includes at least one of acoustic emission signal, surface temperature and rolling force; When the acoustic emission signal indicates that the surface of the inner bore of the hydraulic cylinder and the mating parts is in a preset plastic deformation stage and the surface temperature is maintained within a preset range, the current reference ultrasonic rolling process parameters are determined to be the optimal fusion parameters. If the acoustic emission signal indicates that the surface of the inner bore of the hydraulic cylinder and the mating parts exhibits brittle fracture characteristics, then the reference ultrasonic rolling process parameters will be adjusted using a first feedback method. If the surface temperature of the inner bore of the hydraulic cylinder and the mating parts is greater than the preset temperature range, the reference ultrasonic rolling process parameters will be adjusted by a second feedback.

4. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 3, characterized in that, If the acoustic emission signal indicates that the surface of the inner bore of the hydraulic cylinder and the mating parts exhibits brittle fracture characteristics, the reference ultrasonic rolling process parameters will be adjusted using a first feedback method, specifically including: Based on the acoustic emission signal, the signal state corresponding to the brittle fracture characteristic is determined; wherein, the signal state includes at least one of the instantaneous value of signal amplitude, signal energy release rate, and peak power spectral density. Based on the frequency of the signal states corresponding to the brittle fracture characteristics, the severity level of brittle fracture corresponding to the ultrasonic rolling stage is determined. Based on the different severity levels of brittle fracture, the rolling force and feed rate corresponding to the reference ultrasonic rolling process parameters are reduced by different percentages.

5. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 3, characterized in that, If the surface temperature of the inner bore of the hydraulic cylinder and the mating parts is greater than the preset temperature range, the reference ultrasonic rolling process parameters will be adjusted using a second feedback method, specifically including: During the ultrasonic rolling process, the real-time ratio of heat input power to heat dissipation power is calculated based on the temperature of the inner bore of the hydraulic cylinder and the surface of the mating parts, as well as the reference ultrasonic rolling process parameters. If the real-time ratio is greater than a preset ratio threshold and the temperature is greater than a preset temperature threshold, then the surface temperature is determined to be overheated. Based on the difference between the real-time ratio and the preset temperature threshold, the rolling force corresponding to the reference ultrasonic rolling process parameters is reduced by different proportional values, and the feed rate and ultrasonic amplitude are increased by corresponding proportional values.

6. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 1, characterized in that, After collecting surface strengthening treatment data and adjusting the reference ultrasonic rolling process parameters based on the collected data, the method further includes: During ultrasonic rolling, the critical process parameters corresponding to the transition of acoustic emission signals from the preset plastic deformation stage to the abnormal state are saved to construct a safety boundary database. When responding to parameter control commands of the same functional area type in subsequent responses, the safety boundary database is used as a constraint condition, and optimization is performed based on the reference ultrasonic rolling process parameters to adjust the error between the process parameters and the safety boundary to a preset error range in order to obtain an optimized parameter combination.

7. The surface strengthening method for the inner bore and mating parts of a hydraulic cylinder according to claim 1, characterized in that, The controlled ultrasonic surface rolling equipment performs surface strengthening treatment on the inner bore and mating parts of the hydraulic cylinder, specifically including: After the rolling tool head of the ultrasonic surface rolling device comes into contact with the surface of the inner bore of the hydraulic cylinder and the mating parts, a first rolling force and a first feed rate are applied for pretreatment in the initial section of the rolling path; When the amplitude fluctuation rate of the acoustic emission signal is detected to be less than the preset amplitude frequency threshold, the process switches to the enhanced rolling stage and applies the second rolling force and the second feed rate corresponding to the reference ultrasonic rolling process parameters. When the residual stress is within the preset target range, the enhanced rolling is completed, and the third rolling force and the third feed rate are applied for finishing rolling. Wherein, the first rolling pressure is less than the third rolling pressure, and the third rolling pressure is less than the second rolling pressure; the third feed rate is less than the second feed rate, and the second feed rate is less than the first feed rate.

8. A surface strengthening device for the inner bore and mating parts of a hydraulic cylinder, characterized in that, The device includes a memory for storing computer program instructions and a processor for executing the program instructions, wherein when the computer program instructions are executed by the processor, the device is triggered to perform the method described in any one of claims 1-7.

9. A non-volatile computer storage medium storing computer-executable instructions, characterized in that, The computer-executable instructions are capable of performing the method described in any one of claims 1-7.

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