Hydraulic system for metal surface nanocrystallization machining and control method thereof

Abstract

The invention belongs to the technical field of mechanical engineering, and particularly relates to a hydraulic system for metal surface nanocrystallization machining and a control method thereof, and the hydraulic system comprises a hydraulic power unit, a pressure adjusting unit, a single-action hydraulic cylinder, an energy accumulator, a force sensor, a machining tool bit, a PLC and a man-machine interaction unit. The hydraulic power unit provides a hydraulic oil source; the pressure regulating unit is used for stabilizing and regulating the pressure; a rodless cavity of the single-action hydraulic cylinder is connected with the pressure adjusting unit through a working pipeline, and the tail end of a piston rod is fixedly connected with the machining tool bit; the energy accumulator is connected to the working pipeline in parallel; the force sensor detects the acting force of the machining tool bit on the workpiece in real time and feeds back the acting force to the PLC; and the PLC calculates and adjusts the output pressure of the pressure adjusting unit in real time according to the deviation between the target acting force and the actual acting force. Load fluctuation caused by the shape, clamping and deformation of the workpiece can be automatically compensated, uniform and stable nanocrystallization machining is achieved, and the technological adaptability of machining quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of mechanical engineering technology, specifically a hydraulic system and its control method for nano-machining of metal surfaces. Background Technology

[0002] Currently, the main methods for surface nano-machining of shaft-type or plate-type metal workpieces are surface mechanical rolling (SMGT) and surface mechanical pressing (SMRT). SMGT and SMRT methods involve fixing a cutting tool on a machine tool holder and controlling the movement of the tool holder to drive the cutting head into the workpiece surface to a certain depth. Simultaneously, the movement of the workpiece causes relative displacement between the cutting head and the workpiece surface, resulting in plastic rheology in the surface metal and grain refinement. This forms a surface gradient nanostructure with gradually increasing grain size from the surface inwards, thereby improving the workpiece's surface strength, wear resistance, and other mechanical properties. The drawbacks of these methods are that they are limited by the mounting accuracy of the metal workpiece and the deflection deformation caused by stress during the surface nano-machining process. This uneven stress distribution across different parts of the workpiece leads to variations in the surface nano-machining effect in different areas, negatively impacting batch stability. Furthermore, conventional displacement control methods can only process regularly shaped workpieces such as round bars and plates; they cannot process irregular workpieces, such as elliptical bars and plates with undulating surfaces.

[0003] The patent with publication number CN105063340A proposes a hydraulic ultrasonic surface nano-processing device, which uses an oil pump and a hydraulic cylinder to provide processing pressure. Although it can set a processing pressure head to press a set constant force on the workpiece surface, it lacks further pressure adjustment and stabilization devices, as well as a real-time pressure feedback adjustment device, which makes the pressure adjustment have a certain lag and the pressure control accuracy is poor.

[0004] Existing surface nano-machining devices are difficult to output a constant pressure for surface nano-machining of metal workpieces due to unreasonable pressure regulation design and other reasons. Therefore, there is an urgent need to develop a new type of surface nano-machining system to achieve a constant and accurate output of processing pressure in real time, so as to obtain a uniform surface nano-machining effect on various workpieces. Summary of the Invention

[0005] The purpose of this invention is to provide a hydraulic system and its control method for nano-machining of metal surfaces, so as to achieve a constant and accurate output of machining pressure in real time during the nano-machining process, and to obtain a uniform surface nano-machining effect on various workpieces, thereby overcoming the shortcomings of the existing technology.

[0006] The technical solution adopted by the present invention to achieve the above objectives is: a hydraulic system for nano-machining of metal surfaces, comprising: a hydraulic power unit, a pressure regulating unit, a single-acting hydraulic cylinder, an accumulator, a force sensor, a machining head, a PLC controller, and a human-machine interaction unit;

[0007] A hydraulic power unit is used to provide a controllable hydraulic oil source;

[0008] The pressure regulating unit has its inlet pipe connected to the output end of the hydraulic power unit, and is used to stabilize and regulate the pressure of the input hydraulic oil.

[0009] A single-acting hydraulic cylinder, the rodless chamber of which is connected to the pressure output end of the pressure regulating unit through a working pipeline, and the end of its piston rod is used to fix the machining head;

[0010] The accumulator has its oil port connected in parallel to the working pipeline via a tee connector; it is used to store a portion of the oil when the system pressure increases instantaneously and to release the oil when the pressure decreases instantaneously, thereby effectively smoothing the pressure fluctuations in the working pipeline and providing a stable pressure environment for the single-acting hydraulic cylinder.

[0011] A force sensor is installed on the force transmission path of the piston rod to collect the force applied to the workpiece by the machining head in real time and generate a corresponding electrical signal.

[0012] The human-machine interface unit connects to the PLC controller and is used to set parameters and display system status;

[0013] The PLC controller has its signal input terminal connected to the force sensor to receive the applied force electrical signal, and its control output terminal connected to the pressure regulating unit.

[0014] The PLC controller is used to calculate and output adjustment commands to the pressure adjustment unit in real time based on the deviation between the preset target force value and the real-time collected force value, thereby dynamically adjusting the pressure of the working pipeline so that the machining head maintains a constant machining force on the workpiece.

[0015] The hydraulic power unit includes: a hydraulic oil tank, a drive motor, and a hydraulic pump;

[0016] The oil inlet of the hydraulic pump is connected to the hydraulic oil tank through an oil suction pipe; the oil outlet of the hydraulic pump is connected to the output end of the hydraulic power unit for outputting pressurized oil.

[0017] The drive motor is connected to the main shaft of the hydraulic pump to provide power;

[0018] The hydraulic pump is a constant pressure variable pump with a pressure feedback mechanism. When the system pressure reaches the set value, it can automatically reduce the output flow to reduce energy consumption and heat generation.

[0019] The pressure regulating unit includes, in sequence along the oil flow direction: an anti-backflow element, a working mode switching element, and a proportional pressure reducing valve;

[0020] The inlet of the anti-backflow element is connected to the output end of the hydraulic power unit, and its outlet is connected to the inlet of the working mode switching element.

[0021] The working mode switching element includes a working position and an unloading position, with the oil port of the working position connected to the inlet of the proportional pressure reducing valve; the outlet of the proportional pressure reducing valve constitutes the pressure output terminal of the pressure regulating unit.

[0022] The working mode switching element can switch the oil circuit under the control of the PLC controller, so that the pressure oil can be directed to the proportional pressure reducing valve or directly unloaded and returned to the oil tank.

[0023] The proportional pressure reducing valve is equipped with a pressure sensor to detect its outlet pressure value in real time and feed it back to the PLC controller, forming a secondary closed-loop monitoring of the outlet pressure.

[0024] The anti-backflow element is a one-way valve, and its installation direction is set to allow oil to flow only from the hydraulic power unit to the pressure regulating unit, so as to prevent oil backflow from impacting the hydraulic pump when the system pressure fluctuates or stops.

[0025] The working mode switching element is a two-position three-way solenoid directional valve. When it is energized, the oil circuit switches to the working position, and the oil circuit is connected to the proportional pressure reducing valve. When it is de-energized, the oil circuit switches to the unloading position, and the system pressure drops to the minimum.

[0026] The single-acting hydraulic cylinder is a piston-type hydraulic cylinder, with an oil inlet on its cylinder body that communicates with the rodless chamber; and a first connecting structure at the front end of its piston rod.

[0027] The force sensor is a cylindrical force sensor, with a second connection structure at one end that matches the first connection structure at the front end of the piston rod, and a third connection structure at the other end for mounting the machining head.

[0028] The first connecting structure and the second connecting structure, as well as the second connecting structure and the third connecting structure, are all rigidly connected with coaxiality to ensure the accurate transmission and measurement of force.

[0029] The first connecting structure is an axial center hole A opened on the end face of the piston rod;

[0030] The second connection structure is a cylindrical mounting handle protruding from one end of the force sensor, and the mounting handle is pressed into the central hole A by an interference fit.

[0031] The third connection structure is an axial center hole B opened at the other end of the force sensor.

[0032] The machining head has a cylindrical tool holder that mates with the central hole B; the tool holder is pressed into the central hole B with an interference fit; the entire machining head is fixed on the tool post of the machine tool by the cylinder body of a single-acting hydraulic cylinder and is driven by the machine tool to move relative to the workpiece.

[0033] The machining head is either a SMGT (Surface Mechanical Rolling) head or a SMRT (Surface Mechanical Rolling) head used for nano-machining of metal materials.

[0034] The front end of the machining head is a ball, and the ball is made of cemented carbide, ceramic, ruby ​​or diamond.

[0035] The PLC controller includes: a central processing unit, a digital input / output module, an analog input module, and an analog output module;

[0036] The analog input module is connected to the force sensor to collect analog force signals;

[0037] The analog output module is connected to the proportional pressure reducing valve in the pressure regulating unit to output a pressure control signal;

[0038] The PLC controller has a memory that periodically executes a PID control algorithm to achieve rapid and precise closed-loop adjustment of the processing force.

[0039] It also includes auxiliary function units;

[0040] The auxiliary functional unit includes: a radiator, an oil filtration module, and a system pressure monitoring module;

[0041] The radiator is connected in series in the system's oil return line;

[0042] The oil filtration module includes: an inlet filter installed at the oil inlet of the hydraulic pump and a return filter installed in the return oil pipeline;

[0043] The system pressure monitoring module is a pressure gauge, whose pressure measuring point is connected to the working pipeline for local display of the system working pressure.

[0044] A control method for a hydraulic system used in nano-machining of metal surfaces includes the following steps:

[0045] S1: System power-on initialization, set the target processing force F through the human-machine interface unit. m And the piston diameter D parameter of the single-acting hydraulic cylinder, and set the working mode switching element to the unloading position;

[0046] S2: Start the hydraulic power unit. After the system pressure stabilizes, switch the working mode switching element to the working position to allow the pressurized oil to enter the pressure regulating unit.

[0047] S3: Operate the machine tool drive single-acting hydraulic cylinder to make the machining head contact the workpiece and enter the machining process;

[0048] S4: During the processing, the force sensor collects the actual processing force F in real time at a predetermined sampling frequency. c And transmit it to the PLC controller;

[0049] S5: The PLC controller calculates the instantaneous force deviation ΔF = F in each control cycle. m -F c And according to the formula ΔP=4×ΔF / (π×D) 2 The force deviation ΔF is converted into the target pressure adjustment amount ΔP required for the rodless chamber of the single-acting hydraulic cylinder;

[0050] S6: The PLC controller reads the actual current outlet pressure P from the proportional pressure reducing valve in the pressure regulating unit. A Combined with the target pressure adjustment amount ΔP, and based on the preset pressure-control signal mapping function I... m =f(P) A (+ΔP), calculate the real-time control signal value I to be sent to the proportional pressure reducing valve. m ;

[0051] S7: The PLC controller will input the real-time control signal value I m The output is sent to the proportional pressure reducing valve, and its opening is adjusted to change the pressure in the working pipeline, thereby increasing the actual processing force F. c The processing force F applied to the target m convergence;

[0052] S8: Repeat steps S4 to S7 until the processing cycle ends;

[0053] S9: After processing is completed, first switch the working mode switching element to the unloading position, and then stop the hydraulic power unit.

[0054] The present invention has the following beneficial effects and advantages:

[0055] 1. This invention uses a force sensor to detect the actual force exerted by the machining head on the workpiece in real time, and a PLC controller quickly compares and calculates this force with a preset target value to form a closed-loop feedback. This control strategy can automatically compensate for load changes caused by irregular workpiece shape, clamping deviation, or material deformation during machining, ensuring minimal force fluctuations throughout the machining path (as shown in the embodiment, the hardness distribution is uniform), thereby obtaining a surface nano-layer with consistent depth and performance.

[0056] 2. This invention uses a proportional pressure reducing valve as the core pressure regulating element, which has a fast response speed and good control linearity. Combined with the accumulator's absorption of pressure pulsations in the working pipeline and the simplified circuit structure of the single-acting hydraulic cylinder, the system can quickly suppress pressure shocks and rapidly rebuild pressure balance during sudden load changes. This makes the system insensitive to external disturbances, with stable output pressure, providing a stable mechanical environment for the uniform refinement of nanocrystals.

[0057] 3. The hydraulic power unit of this invention uses a constant-pressure variable pump, which outputs the corresponding flow rate only when needed, avoiding energy loss caused by overflow of a fixed-displacement pump, resulting in significant energy savings. This force control system can be integrated with tool holders of different machine tools (such as lathes and milling machines). By changing different types of machining heads (such as SMGT or SMRT heads), nanoscale machining of shafts, plates, and even complex curved surfaces of metal workpieces can be performed, overcoming the technical limitations of traditional displacement control methods that have stringent requirements on workpiece shape.

[0058] 4. The hydraulic circuit components of this invention are simplified. The connection between the single-acting hydraulic cylinder, force sensor, and cutter head adopts a coaxial interference fit, which provides good rigidity and is easy to assemble and adjust. The system uses a PLC as the core controller, and the processing parameters can be easily set and switched through the human-machine interface unit to realize the automated operation and status monitoring of the processing process. This reduces the technical threshold for operators and helps to ensure the repeatability and consistency of processing quality. Attached Figure Description

[0059] Figure 1 A schematic diagram of the hydraulic system structure of Embodiment 1 of the present invention is shown;

[0060] Figure 2 A schematic diagram of the single-acting hydraulic cylinder structure of Embodiment 1 of the present invention is shown;

[0061] Figure 3 A schematic diagram of the force sensor structure according to Embodiment 1 of the present invention is shown;

[0062] Figure 4 A schematic diagram of the machining tool structure of Embodiment 1 of the present invention is shown;

[0063] Figure 5 The diagram shows the control principle of the PLC controller according to Embodiment 1 of the present invention;

[0064] Figure 6 A flowchart illustrating the steps of the control method of Embodiment 1 of the present invention is shown;

[0065] Figure 7 This shows a scanning electron microscope (SEM) image of a cross-section of a 316L austenitic stainless steel round bar sample from Embodiment 1 of the present invention.

[0066] Figure 8The surface hardness distribution of 316L austenitic stainless steel round bar samples in Example 1 and Comparative Example 1 is shown in comparison.

[0067] Figure 9 This shows a scanning electron microscope (SEM) image of a cross-section of a pure copper plate sample in Embodiment 2 of the present invention;

[0068] Figure 10 The surface hardness distribution of pure copper plate samples in Example 2 and Comparative Example 2 is shown in comparison.

[0069] Figure 11 This shows a scanning electron microscope (SEM) image of the cross-section of a Z5CND16-4 martensitic stainless steel elliptical bar sample from Example 3 of the present invention.

[0070] Figure 12 The surface hardness distribution of the Z5CND16-4 martensitic stainless steel elliptical bar sample in Example 3 of the present invention is shown.

[0071] Among them, 1 is the hydraulic oil tank; 2 is the electric motor; 3 is the hydraulic pump; 4 is the check valve; 5 is the two-position three-way solenoid directional valve; 6 is the proportional pressure reducing valve; 7 is the accumulator; 8 is the single-acting hydraulic cylinder; 801 is the oil inlet; 802 is the piston rod; 803 is the center hole A; 9 is the pressure gauge; 10 is the force sensor; 1001 is the mounting handle; 1002 is the sensor body; 1003 is the center hole B; 11 is the machining head; 1101 is the tool holder; 1102 is the ball cup; 1103 is the cutting ball; 12 is the PLC controller; 13 is the radiator; 14 is the return oil filter; 15 is the inlet oil filter; and 16 is the human-machine interface unit. Detailed Implementation

[0072] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0073] The system of this invention aims to achieve high-precision, real-time constant control of the force applied during machining through an integrated hydraulic and electronic control scheme. Its core consists of: a hydraulic power unit providing oil, which, after being stabilized and regulated by a pressure regulating unit, drives a single-acting hydraulic cylinder; the piston rod of this hydraulic cylinder is connected to the machining head via a force feedback unit; simultaneously, the system is equipped with an energy storage and pressure stabilizing unit to absorb pressure pulsations; a controller receives the force feedback signal and compares and calculates it with a set target value, thereby adjusting the output of the pressure regulating unit in real time, forming a closed-loop force control circuit; in addition, the system is also equipped with a human-machine interface unit for parameter setting and monitoring. The connection relationships, working principles, and preferred embodiments of the various components will be further elaborated below based on this technical framework.

[0074] Example 1:

[0075] like Figure 1As shown, Embodiment 1 of the present invention provides a hydraulic system for nano-machining of metal surfaces, including a hydraulic oil tank 1, an electric motor 2, a constant pressure variable pump 3, a check valve 4, a two-position three-way solenoid directional valve 5, a proportional pressure reducing valve 6, an accumulator 7, a single-acting hydraulic cylinder 8, a force sensor 10, a machining head 11, a PLC controller 12, and a human-machine interface unit 16. The specific structure is as follows:

[0076] The electric motor 2 drives the hydraulic pump 3 to operate, enabling the hydraulic pump 3 to supply pressure to the system. In this embodiment, the hydraulic pump 3 is a constant-pressure variable pump, which provides stable pressure to the system while only outputting the necessary flow, resulting in lower power loss and greater energy efficiency in the hydraulic system. Furthermore, the constant-pressure variable pump has a fast response, high pressure resistance, and impact resistance, with minimal pressure fluctuations during the movement of the hydraulic cylinder piston rod. The outlet of the hydraulic pump 3 is connected to the inlet of the check valve 4, which in turn is connected to the inlet of the two-position three-way solenoid directional valve 5. The check valve 4 prevents hydraulic oil from flowing back into the hydraulic pump 3 and causing damage. The working port of the two-position three-way solenoid directional valve 5 is connected to the inlet of the proportional pressure reducing valve 6, which in turn is connected to the inlet 801 on the rodless side of the single-acting hydraulic cylinder 8. The proportional pressure reducing valve 6 features high control precision, fast response speed, and strong anti-contamination capability. When the load on the hydraulic cylinder changes, it can quickly replenish or release pressure, maintaining a constant output pressure of the hydraulic cylinder. The piston rod 802 of the single-acting hydraulic cylinder 8 is coaxially connected to the machining head 11 via the force sensor 10. The single-acting hydraulic cylinder eliminates the hydraulic circuit on the rod-side, effectively avoiding the influence of hydraulic resistance on the piston rod movement and improving system response speed and pressure control accuracy. The accumulator 7 is connected between the proportional pressure reducing valve 6 and the single-acting hydraulic cylinder 8. When the hydraulic cylinder load changes, the accumulator 7 provides effective vibration buffering for the entire hydraulic circuit, reducing system pressure fluctuations and making the hydraulic cylinder output pressure more stable. The PLC controller 12 communicates with the proportional pressure reducing valve 6, the force sensor 10, the human-machine interface unit 16, and the two-position three-way solenoid directional valve 5. The force sensor 10 can feed back the actual output force of the hydraulic cylinder piston rod to the PLC controller 12 in real time. Based on this feedback, the PLC controller adjusts the working port pressure of the proportional pressure reducing valve 6 in real time via electrical signals, ensuring system response speed and pressure control accuracy, and achieving a constant and accurate output of machining pressure during surface nano-machining.

[0077] The hydraulic system also includes auxiliary functional units, including: a radiator 13, a return oil filter 14, and an inlet oil filter 15. The inlet of the radiator 13 is connected to the return oil port of the two-position three-way solenoid directional valve 5 and the return oil port of the proportional pressure reducing valve 6, for cooling the hydraulic oil in the system. The return oil filter 14 is connected between the outlet of the radiator 13 and the hydraulic oil tank 1, for filtering the hydraulic oil flowing back to the tank. The inlet oil filter 15 is connected between the inlet of the hydraulic pump 3 and the hydraulic oil tank 1, for filtering the hydraulic oil output to the constant pressure variable pump. This auxiliary functional unit also includes a pressure gauge 9, which is connected between the proportional pressure reducing valve 6 and the single-acting hydraulic cylinder 8, for displaying the pressure on the rodless side of the hydraulic cylinder.

[0078] like Figure 2 As shown, the piston rod 802 of the single-acting hydraulic cylinder 8 has a central hole A803 at its front end. Figure 3 As shown, the force sensor 10 consists of a cylindrical mounting handle 1001 aligned with the axis, a sensor body 1002, and a central hole B1003. During connection, the mounting handle 1001 is inserted into the central hole B1003 using an interference fit. Figure 4 As shown, the machining head 11 consists of a cylindrical tool holder 1101, a ball joint 1102, and a cutting ball 1103 aligned with the same axis. During connection, the tool holder 1101 is inserted into the central hole B1003 using an interference fit. This connection method satisfies the coaxial fastening connection of the hydraulic cylinder piston rod, force sensor, and machining head, giving the actuator good rigidity.

[0079] In this embodiment, the machining head 11 is a surface mechanically rolled SMGT head, and the cutting ball 1103 is a φ6mm ceramic ball. During operation, the single-acting hydraulic cylinder 8 is fixed on the machine tool holder (not shown in the figure). When machining the sample, the movement of the machine tool holder drives the single-acting hydraulic cylinder 8 to move, thereby driving the machining head 11 to perform surface nano-machining on the metal workpiece.

[0080] The proportional pressure reducing valve 6 has a built-in pressure sensor that can detect the actual pressure P at its working port in real time. A The data is fed back to the PLC controller 12 in real time. The PLC controller 12 includes: a central processing unit, a digital input / output module, an analog input module, and an analog output module; the analog input module is connected to the force sensor 10 to collect analog force signals; the analog output module is connected to the proportional pressure reducing valve 6 in the pressure regulating unit to output pressure control signals; the PLC controller 12 has a built-in memory that periodically executes a PID control algorithm to achieve rapid and precise closed-loop regulation of the processing force. The control principle of the PLC controller is as follows: Figure 5 As shown.

[0081] like Figure 6As shown, this embodiment also provides a control method for the above-mentioned hydraulic system, including the following steps:

[0082] S1: System power-on initialization, set the target processing force F through the human-machine interface unit 16. m And the piston diameter D parameter of the single-acting hydraulic cylinder 8, and place the two-position three-way solenoid directional valve 5 in the unloading position (left position).

[0083] S2: Start the hydraulic power unit. After the system pressure stabilizes, switch the two-position three-way solenoid valve 5 to the working position (right position) to allow the pressurized oil to enter the pressure regulating unit.

[0084] S3: Operate the machine tool to drive the single-acting hydraulic cylinder 8 to make the machining head 11 contact the workpiece and enter the machining process;

[0085] S4: During the processing, the force sensor 10 collects the actual processing force F in real time at a predetermined sampling frequency. c And transmit it to PLC controller 12;

[0086] S5: PLC controller 12 calculates the instantaneous force deviation ΔF = F in each control cycle. m -F c And according to the formula ΔP=4×ΔF / (π×D) 2 The force deviation ΔF is converted into the target pressure adjustment amount ΔP required for the rodless chamber of the single-acting hydraulic cylinder 8;

[0087] S6: PLC controller 12 reads the actual value P of the current outlet pressure from the proportional pressure reducing valve 6 in the pressure regulating unit. A Combined with the target pressure adjustment amount ΔP, and based on the preset pressure-control signal mapping function I... m =f(P) A +ΔP), calculate the real-time control signal value I that should be sent to the proportional pressure reducing valve 6. m ;

[0088] S7: The PLC controller 12 will transfer the real-time control signal value I m The output is sent to the proportional pressure reducing valve 6, and its opening is adjusted to change the pressure in the working pipeline, thereby increasing the actual processing force F. c The processing force F applied to the target m convergence;

[0089] S8: Repeat steps S4 to S7 until the processing cycle ends;

[0090] S9: After processing is completed, first switch the two-position three-way solenoid directional valve 5 to the unloading position (left position), and then stop the hydraulic power unit.

[0091] In this embodiment, a processing pressure of 140 kg was used to perform surface nano-machining on a φ15 mm rod-shaped sample of 316L austenitic stainless steel, resulting in a gradient nanostructure with gradually increasing grain size from the surface to the interior. Figure 7 As shown. The sample surface grain size reached 38 nm, the surface hardness increased from the original 190 HV to 450 HV, and the hardened layer depth reached 600 μm. Hardness measurements were performed at six evenly distributed points along the circumference of the sample's outer surface, and the results were compared. Figure 8 As shown, the results indicate that the hardness at six different locations on the circumference of the sample in this embodiment remained within the range of 450±10HV, and the hardness distribution was well uniform.

[0092] Example 2

[0093] In this embodiment, the machining head 11 is replaced with a surface mechanical rolling (SMRT) head, and the cutting ball 1103 is replaced with a φ8mm cemented carbide ball. Surface nano-machining is performed on a 100×100×5mm flat plate sample of pure copper. The machining pressure is set to 100kg, resulting in a gradient nanostructure where the grain size gradually increases from the surface to the interior. Figure 9 As shown. The sample surface grain size reached 45 nm, the surface hardness increased from the original 70 Hv to 130 Hv, and the hardened layer depth reached 800 μm. Surface hardness was measured at nine evenly distributed points in the planar area of ​​the sample, and the results were compared, as shown. Figure 10 As shown, the results indicate that the hardness at nine different locations of the sample in this embodiment remained within the range of 130±7HV, and the hardness distribution was well uniform.

[0094] Example 3

[0095] In this embodiment, the machining head 11 is replaced with a surface mechanical pressing (SMGT) head, and the cutting ball 1103 is replaced with an 8mm ruby ​​ball. Surface nano-machining is performed on a Z5CND16-4 martensitic stainless steel elliptical rod sample, with major and minor axes of 30mm and 20mm respectively. A machining pressure of 150kg is set, resulting in a gradient nanostructure where the grain size gradually increases from the surface to the interior. Figure 11 As shown. The sample surface grain size reached 32 nm, the surface hardness increased from the original 330 HV to 520 HV, and the hardened layer depth reached 500 μm. Hardness measurements were performed at eight evenly distributed points along the circumference of the sample's outer surface, and the results were compared. Figure 12 As shown, the results indicate that the hardness at eight different locations on the circumference of the sample in this embodiment remained within the range of 520±10 HV, demonstrating good uniformity in hardness distribution. Traditional displacement control methods cannot perform surface nano-machining on such irregular elliptical bars.

[0096] Comparative Example 1

[0097] This comparative example uses a traditional displacement control method to perform surface nano-machining on a φ15mm rod-shaped sample of 316L austenitic stainless steel with the same shape and material as in Example 1. The machining head is also a surface mechanical pressing (SMGT) head, and the cutting ball is a φ6mm ceramic ball. The indentation depth is set to 150μm, resulting in a surface gradient nanostructure similar to that of Example 1. Subsequently, surface hardness measurements were performed at six evenly distributed points along the circumference of the sample's outer surface, and the hardness results were compared. Figure 8 As shown, the results indicate that the hardness distribution of the comparative sample in the circumferential direction has large fluctuations, fluctuating between 420HV and 480HV, and the hardness uniformity is far lower than that of the sample obtained in Example 1.

[0098] Comparative Example 2

[0099] This comparative example uses a traditional displacement control method to perform surface nano-machining on a 100×100×5mm pure copper flat sample of the same shape and material as in Example 2. The machining head is also a surface mechanical rolling (SMRT) head, and the cutting ball is also a φ8mm cemented carbide ball. The reduction is set to 110μm, resulting in a surface gradient nanostructure similar to that of Example 2. Subsequently, surface hardness measurements were performed at nine evenly distributed points on the planar area of ​​the sample, and the results were compared. Figure 10 As shown, the results indicate that the hardness distribution in different regions of this comparative sample fluctuates significantly, ranging between 100HV and 160HV, and the hardness uniformity is far lower than that of the sample obtained in Example 2.

[0100] The above results demonstrate that the hydraulic system and control method for metal surface nano-machining of the present invention have good surface nano-machining effects on both shaft-type and plate-type workpieces. Compared with traditional displacement control methods, the system and method of the present invention have better processing stability and can obtain more uniform surface nano-machining effects on various workpieces.

[0101] This invention provides a hydraulic system and its control method for nano-machining of metal surfaces. By integrating hydraulic power, high-precision electro-hydraulic proportional pressure regulation, energy storage and pressure stabilization, real-time force feedback, and closed-loop control, a constant force output system with rapid response and precise control is constructed. This solution effectively solves the technical problems of uneven processing pressure and large differences in surface nano-machining effects caused by workpiece clamping errors, deformation, and other factors in traditional displacement control methods. It is particularly suitable for high-quality and uniform surface nano-machining of shafts, plates, and even irregularly shaped workpieces. The above description is only a preferred embodiment of this invention, but the scope of protection of this invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this invention, based on the technical solution and inventive concept of this invention, should be covered within the scope of protection of this invention.

[0102] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention, and the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. This is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0103] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A hydraulic system for nano-machining of metal surfaces, characterized in that, include: The hydraulic power unit, pressure regulating unit, single-acting hydraulic cylinder (8), accumulator (7), force sensor (10), machining head (11), PLC controller (12) and human-machine interaction unit (16); A hydraulic power unit is used to provide a controllable hydraulic oil source; The pressure regulating unit has its inlet pipe connected to the output end of the hydraulic power unit, and is used to stabilize and regulate the pressure of the input hydraulic oil. The single-acting hydraulic cylinder (8) has its rodless chamber connected to the pressure output end of the pressure regulating unit through the working pipeline, and the end of its piston rod (802) is used to fix the machining head (11). The accumulator (7) has its oil port connected in parallel to the working pipeline through a three-way connector; it is used to store some oil when the system pressure rises instantaneously and release oil when the pressure drops instantaneously, thereby effectively smoothing the pressure fluctuations in the working pipeline and providing a stable pressure environment for the single-acting hydraulic cylinder (8); Force sensor (10), which is set on the force transmission path of the piston rod (802), is used to collect the force applied to the workpiece by the machining head (11) in real time and generate the corresponding electrical signal; The human-machine interface unit (16) is connected to the PLC controller (12) and is used to set parameters and display system status; The PLC controller (12) has its signal input terminal connected to the force sensor (10) to receive the applied force electrical signal, and its control output terminal connected to the pressure regulating unit. The PLC controller (12) is used to calculate and output adjustment commands to the pressure adjustment unit in real time according to the deviation between the preset target force value and the real-time collected force value, so as to dynamically adjust the pressure of the working pipeline and make the processing head (11) maintain a constant processing force on the workpiece.

2. The hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, The hydraulic power unit includes: a hydraulic oil tank (1), a drive motor (2), and a hydraulic pump (3). The oil inlet of the hydraulic pump (3) is connected to the hydraulic oil tank (1) through the oil suction pipe; the oil outlet of the hydraulic pump (3) is connected to the output end of the hydraulic power unit for outputting pressurized oil. The drive motor (2) is connected to the main shaft of the hydraulic pump (3) to provide power; The hydraulic pump (3) is a constant pressure variable pump with a pressure feedback mechanism. When the system pressure reaches the set value, it can automatically reduce the output flow to reduce energy consumption and heat generation.

3. The hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, The pressure regulating unit includes, in sequence along the oil flow direction: an anti-backflow element, a working mode switching element, and a proportional pressure reducing valve (6). The inlet of the anti-backflow element is connected to the output end of the hydraulic power unit, and its outlet is connected to the inlet of the working mode switching element. The working mode switching element includes a working position and an unloading position, wherein the oil port of the working position is connected to the inlet of the proportional pressure reducing valve (6); the outlet of the proportional pressure reducing valve (6) constitutes the pressure output end of the pressure regulating unit. The working mode switching element can switch the oil circuit under the control of the PLC controller (12), so that the pressure oil can be directed to the proportional pressure reducing valve (6) or directly unloaded back to the oil tank (1). The proportional pressure reducing valve (6) is equipped with a pressure sensor, which is used to detect its outlet pressure value in real time and feed it back to the PLC controller (12) to form a secondary closed-loop monitoring of the outlet pressure.

4. A hydraulic system for nano-machining of metal surfaces according to claim 3, characterized in that, The anti-backflow element is a one-way valve (4), whose installation direction is set to allow oil to flow from the hydraulic power unit to the pressure regulating unit only, so as to prevent oil backflow from impacting the hydraulic pump (3) when the system pressure fluctuates or stops. The working mode switching element is a two-position three-way solenoid directional valve (5). When it is energized, the oil circuit switches to the working position, and the oil circuit is connected to the proportional pressure reducing valve (6). When it is de-energized, the oil circuit switches to the unloading position, and the system pressure drops to the minimum.

5. A hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, The single-acting hydraulic cylinder (8) is a piston-type hydraulic cylinder, and its cylinder body is provided with an oil inlet (801) that communicates with the rodless chamber; its piston rod (802) has a first connecting structure at its front end; The force sensor (10) is a cylindrical force sensor, with a second connection structure at one end that matches the first connection structure at the front end of the piston rod (802), and a third connection structure at the other end for mounting the machining head (11); The first connecting structure and the second connecting structure, as well as the second connecting structure and the third connecting structure, are all rigidly connected with coaxiality to ensure the accurate transmission and measurement of force.

6. A hydraulic system for nano-machining of metal surfaces according to claim 5, characterized in that, The first connection structure is an axial center hole A (803) opened on the end face of the piston rod (802); The second connection structure is a cylindrical mounting handle (1001) protruding from one end of the force sensor (10), and the mounting handle (1001) is pressed into the central hole A (803) in an interference fit manner; The third connection structure is an axial center hole B (1003) opened at the other end of the force sensor (10).

7. A hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, The machining head (11) has a cylindrical tool holder (1101) that mates with the center hole B (1003); the tool holder (1101) is pressed into the center hole B (1003) with an interference fit; the entire machining head (11) is fixed on the tool post of the machine tool by the cylinder body of the single-acting hydraulic cylinder (8), and is driven by the machine tool to move relative to the workpiece. The machining head (11) is a SMGT head for surface mechanical rolling or a SMRT head for surface mechanical rolling for nano-processing of metal materials. The front end of the machining head (11) is a cutting ball (1103), and the cutting ball (1103) is made of cemented carbide, ceramic, ruby ​​or diamond.

8. A hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, The PLC controller (12) includes: a central processing unit, a digital input / output module, an analog input module, and an analog output module; The analog input module is connected to the force sensor (10) to collect the simulated force signal; The analog output module is connected to the proportional pressure reducing valve (6) in the pressure regulating unit to output a pressure control signal; The PLC controller (12) has a memory that periodically executes a PID control algorithm to achieve rapid and precise closed-loop adjustment of the processing force.

9. A hydraulic system for nano-machining of metal surfaces according to claim 1, characterized in that, It also includes auxiliary function units; The auxiliary functional unit includes: a radiator (13), an oil filtration module and a system pressure monitoring module; The radiator (13) is connected in series in the system's return oil line; The oil filtration module includes: an inlet filter (15) installed at the oil inlet of the hydraulic pump (3) and a return filter (14) installed in the return oil pipeline. The system pressure monitoring module is a pressure gauge (9), whose pressure measuring point is connected to the working pipeline for local display of the system working pressure.

10. A control method for a hydraulic system for nano-machining of metal surfaces according to any one of claims 1-9, characterized in that, Includes the following steps: S1: System power-on initialization, set the target processing force F through the human-machine interaction unit (16). m And the piston diameter D parameter of the single-acting hydraulic cylinder (8), and the working mode switching element is placed in the unloading position; S2: Start the hydraulic power unit. After the system pressure stabilizes, switch the working mode switching element to the working position to allow the pressurized oil to enter the pressure regulating unit. S3: Operate the machine tool to drive the single-acting hydraulic cylinder (8) so that the machining head (11) contacts the workpiece and enters the machining process; S4: During the processing, the force sensor (10) collects the actual processing force F in real time at a predetermined sampling frequency. c And transmit it to the PLC controller (12); S5: The PLC controller (12) calculates the instantaneous force deviation ΔF = F in each control cycle. m -F c And according to the formula ΔP=4×ΔF / (π×D) 2 The force deviation ΔF is converted into the target pressure adjustment amount ΔP required for the rodless chamber of the single-acting hydraulic cylinder (8); S6: The PLC controller (12) reads the actual value P of the current outlet pressure from the proportional pressure reducing valve (6) in the pressure regulating unit. A Combined with the target pressure adjustment amount ΔP, and based on the preset pressure-control signal mapping function I... m =f(P) A +ΔP), calculate the real-time control signal value I that should be sent to the proportional pressure reducing valve (6). m ; S7: The PLC controller (12) will transfer the real-time control signal value I m The output is sent to the proportional pressure reducing valve (6), and its opening is adjusted to change the pressure in the working pipeline, thereby increasing the actual processing force F. c The processing force F applied to the target m convergence; S8: Repeat steps S4 to S7 until the processing cycle ends; S9: After processing is completed, first switch the working mode switching element to the unloading position, and then stop the hydraulic power unit.

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