A test device and method for testing thermal mechanical fatigue of a piston in real time

Abstract

The application provides a test device and method for testing thermal mechanical fatigue of a piston in real time, and relates to the technical field of pistons of internal combustion engines. The test device and method for testing thermal mechanical fatigue of the piston in real time are suitable for testing the thermal mechanical fatigue life of the top surface of the piston of a small and medium-sized gasoline engine, a diesel engine and a natural gas engine. Laser heating, oil control and a temperature measuring instrument are used to keep the top surface of the piston at a set temperature, so as to simulate the temperature load caused by high temperature generated by gas combustion of the internal combustion engine. The top surface of the piston is in contact with a baffle to apply a set pressure to the top surface of the piston, so as to simulate the mechanical load caused by gas pressure of the internal combustion engine. In this way, the piston in different thermal and mechanical coupling loading conditions can be accurately and efficiently simulated. A camera and an image acquisition unit are used to monitor the generation and expansion state of cracks on the top surface of the piston in real time, so as to test the thermal mechanical fatigue life of the top surface of the piston and provide a design criterion for optimization and improvement of the piston.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine piston technology, and more specifically to a test apparatus and method for real-time testing of piston thermomechanical fatigue. Background Technology

[0002] The piston is a core component of an internal combustion engine, significantly impacting its reliability and durability. During engine operation, the piston is subjected not only to the high temperatures generated by combustion gases but also to constantly changing gas pressures, creating a very harsh working environment. The piston crown, especially the throat area of ​​the combustion chamber, is highly susceptible to thermomechanical fatigue, leading to cracking failure, which has become one of the main piston failure modes. Currently, piston fatigue life is typically assessed using methods such as engine bench testing and piston fatigue simulation testing. While engine bench testing is time-consuming and costly, piston fatigue simulation testing offers advantages such as ease of operation, high efficiency, and low cost, gradually becoming the preferred solution for piston fatigue testing.

[0003] Current piston fatigue simulation test benches can only perform thermal load simulations and not mechanical load simulations. Some use high-temperature gas to apply thermal and mechanical coupled loads, which requires a high degree of sealing of the device, has a long test preparation time, is difficult to control during the test, and makes it difficult to achieve the pressure of combustion gas explosion during actual engine operation when using high-temperature gas for pressurization. Others use induction coil heating and local pressurization of the piston to perform thermal and mechanical coupled loading, but the piston's heating and pressure conditions are significantly different from the real state. Summary of the Invention

[0004] The purpose of this invention is to provide a test device and method for real-time testing of piston thermomechanical fatigue, simulating pistons under different thermo-mechanical coupling loading conditions, so as to test the thermomechanical fatigue life of the piston top surface.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A test device for real-time testing of piston thermomechanical fatigue includes a cylinder liner, a piston, a piston drive mechanism, a heating chamber, a cooling chamber, a laser emitter, an oil injection cooling mechanism, a camera, a mechanical load loading control unit, a laser heating control unit, an oil injection cooling control unit, a thermometer, an image acquisition unit, and a main control unit.

[0007] The piston is slidably fitted inside the cylinder liner, and the piston drive mechanism is connected to the piston for transmission. The piston drive mechanism drives the piston to perform linear reciprocating motion along the cylinder liner.

[0008] The upper port of the cylinder liner is connected to the heating chamber, and the lower port of the cylinder liner is connected to the cooling chamber;

[0009] The bottom of the heating chamber is provided with a baffle, and the portion of the baffle corresponding to the upper port is made of transparent material;

[0010] The laser emitter is installed in the heating chamber. The laser beam emitted by the laser emitter passes through the portion of the baffle corresponding to the upper port and continues to irradiate the top surface of the piston.

[0011] The cooling chamber contains engine oil, and the oil injection cooling mechanism cools the engine oil and sprays it onto the piston.

[0012] The camera's camera end faces the portion of the baffle corresponding to the upper port;

[0013] The control end of the piston drive mechanism is connected to the mechanical load loading control unit via a signal cable, and the mechanical load loading control unit is connected to the main control unit via a signal cable.

[0014] The control terminal of the laser emitter is connected to the laser heating control unit via a signal cable, and the laser heating control unit is connected to the main control unit via a signal cable.

[0015] The control terminal of the fuel injection cooling mechanism is connected to the fuel injection cooling control unit via a signal cable, and the fuel injection cooling control unit is connected to the main control unit via a signal cable.

[0016] The thermometer is used to sense the temperature of the piston top sidewall, and the thermometer is connected to the main control unit via a signal cable;

[0017] The camera is connected to the image acquisition unit via a signal cable, and the image acquisition unit is connected to the main control unit via a signal cable.

[0018] Preferably, the piston drive mechanism is configured as a hydraulic cylinder, and the telescopic rod end of the hydraulic cylinder is connected to the piston pin seat via a piston pin.

[0019] Preferably, the outer contour of the baffle on one side of the cylinder liner matches the shape of the piston top surface.

[0020] Preferably, it also includes a beam splitter disposed in the heating chamber, wherein the laser beam emitted by the laser emitter first passes through the beam splitter to change direction before passing through the portion of the baffle corresponding to the upper port.

[0021] Preferably, the oil injection cooling mechanism includes an oil pump, a fuel injector, an oil cooler, and a thermocouple. The oil pump's inlet is connected to the oil in the cooling chamber, and the oil pump's outlet is connected to the fuel injector via an oil outlet pipe. The oil cooler is installed on the oil outlet pipe. The thermocouple's sensing end is located in the oil. The oil injection cooling control unit is connected to the control end of the oil pump, the control end of the oil cooler, and the thermocouple via signal cables.

[0022] Preferably, a window is opened on the side of the cylinder liner within the piston's sliding stroke range, and the sensing end of the temperature measuring instrument faces the window.

[0023] Preferably, the portion of the baffle corresponding to the upper port is made of quartz glass.

[0024] Preferably, the mechanical load loading control unit, laser heating control unit, oil spraying cooling control unit, image acquisition unit, and main control unit are all configured as computers.

[0025] Preferably, the camera is a CCD camera.

[0026] A test method for real-time testing of piston thermomechanical fatigue, using the aforementioned test apparatus for real-time testing of piston thermomechanical fatigue, includes the following steps:

[0027] Step 1: The main control unit adjusts the laser emitter to emit laser beams with different pulse intensities via the laser heating control unit. The temperature of the piston top sidewall is sensed by the thermometer and uploaded to the main control unit. The main control unit processes the data to obtain the "relationship curve between laser beam pulse intensity and piston top surface temperature".

[0028] Step 2: The main control unit adjusts the laser emitter to emit a laser beam with a set pulse intensity according to the "relationship curve between laser beam pulse intensity and piston top surface temperature" through the laser heating control unit to heat the piston top surface. The main control unit triggers the oil injection cooling mechanism through the oil injection cooling control unit to cool the oil and spray it onto the piston, keeping the piston top surface at the set temperature.

[0029] Simultaneously, the temperature of the piston top sidewall is sensed by a thermometer and uploaded to the main control unit to verify the temperature of the piston top surface;

[0030] At the same time, the piston drive mechanism is triggered by the main control unit through the mechanical load loading control unit, which drives the piston to move linearly and reciprocally along the cylinder liner. When the piston moves to the upper end of the cylinder liner, the piston top surface contacts the baffle and applies a set pressure to the piston top surface.

[0031] Meanwhile, the camera captures real-time images of the piston top surface to record whether cracks appear on the piston top surface, the time when cracks appear, and the state of crack propagation.

[0032] Step 3: Stop when the piston completes the set number of reciprocating motions along the cylinder liner.

[0033] The beneficial technical effects of this invention are:

[0034] The present invention provides a test apparatus and method for real-time testing of piston thermomechanical fatigue, applicable to the thermomechanical fatigue life testing of piston crown surfaces in small and medium-sized gasoline engines, diesel engines, and natural gas engines. It employs laser heating, oil control, and a thermometer to maintain the piston crown surface at a set temperature, simulating the temperature load caused by the high temperature generated by combustion in an internal combustion engine. A set pressure is applied to the piston crown surface by contacting a baffle, simulating the mechanical load caused by the pressure of combustion gases in an internal combustion engine. This accurately and efficiently simulates the piston under different thermo-mechanical coupling loading conditions. A camera and image acquisition unit are used to monitor the generation and propagation of cracks on the piston crown surface in real time, thereby testing the thermomechanical fatigue life of the piston crown surface and providing design guidelines for piston optimization and improvement. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the test device for real-time testing of piston thermomechanical fatigue according to an embodiment of the present invention;

[0036] Figure 2 This is a control flowchart of the test method for real-time testing of piston thermomechanical fatigue according to an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Certain embodiments of the invention will be described more fully below with reference to the accompanying drawings, and some, but not all, of these embodiments will be shown. In fact, various embodiments of the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the invention to meet applicable legal requirements.

[0038] In the description of this invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In this embodiment of the invention, a test apparatus and method for real-time testing of piston thermomechanical fatigue are provided. Please refer to [reference needed]. Figure 1 , Figure 2 As shown.

[0040] A testing device for real-time testing of piston thermomechanical fatigue includes a cylinder liner 4, a piston 5, a piston drive mechanism 14, a heating chamber 1, a cooling chamber 8, a laser emitter 9, an oil injection cooling mechanism, a camera 10, a mechanical load loading control unit 19, a laser heating control unit 18, an oil injection cooling control unit 20, a thermometer 22, an image acquisition unit 17, and a main control unit 21. The mechanical load loading control unit 19, the laser heating control unit 18, the oil injection cooling control unit 20, the image acquisition unit 17, and the main control unit 21 are all configured as computers.

[0041] A piston 5 slides within the cylinder liner 4. A piston drive mechanism 14 is connected to the piston 5, driving the piston 5 to reciprocate linearly along the cylinder liner 4. The piston drive mechanism 14 is a hydraulic cylinder, with its extension rod end connected to the piston 5's pin seat via a piston pin 6. The extension rod end of the hydraulic cylinder extends and retracts relative to the cylinder body end, driving the piston 5 to reciprocate linearly along the cylinder liner 4.

[0042] The upper port of cylinder liner 4 is connected to the lower port of heating chamber 1, and the lower port of cylinder liner 4 is connected to the upper port of cooling chamber 7. Both heating chamber 1 and cooling chamber 7 are cylindrical structures, and their outer surfaces are covered with insulation layers.

[0043] A baffle 3 is mounted on the bottom of the heating chamber 1 via a fixing block 2. The portion of the baffle 3 corresponding to the upper port is made of transparent material. The entire baffle 3 is made of quartz glass.

[0044] The outer contour of the baffle 3 on one side (lower side) of the cylinder liner 4 matches the shape of the top surface of the piston 5. In this way, when the top surface of the piston 5 contacts the baffle 3, the baffle 3 and the top surface of the piston 5 are in close contact.

[0045] When the extension rod end of the hydraulic cylinder extends relative to the cylinder body end, the top surface of the piston 5 contacts the baffle 3 to apply pressure to the top surface of the piston 5.

[0046] The control end of the piston drive mechanism 14 (hydraulic cylinder) is an electro-hydraulic servo hydraulic station. The electro-hydraulic servo hydraulic station is connected to the mechanical load loading control unit 19 via a signal cable. The mechanical load loading control unit 19 is connected to the main control unit 21 via a signal cable. The main control unit 21 controls the electro-hydraulic servo hydraulic station through the mechanical load loading control unit 19 to provide hydraulic oil with a set pressure to the hydraulic cylinder. The main control unit 21 also limits the piston 5 so that the top surface of the piston 5 contacts the baffle 3 to apply a set pressure to the top surface of the piston 5.

[0047] A laser emitter 9 and a beam splitter 11 are installed inside the heating chamber 1. The laser beam emitted by the laser emitter 9 is first redirected by the beam splitter 11, and then passes through the portion of the baffle 3 corresponding to the upper port, where the laser beam continues to irradiate the top surface of the piston 5. The beam splitter 11 is used to split the input laser beam into reflected light and transmitted light, so that the reflected light is directed toward the top surface of the piston 5, preventing the high-power, high-heat laser beam from directly hitting the top surface of the piston 5 and burning it.

[0048] The control terminal of the laser emitter 9 is connected to the laser heating control unit 18 via a signal cable, and the laser heating control unit 18 is connected to the main control unit 21 via a signal cable. The main control unit 21 adjusts the pulse intensity of the laser beam emitted by the laser emitter 9 through the laser heating control unit 18, thereby adjusting the heating energy of the laser beam.

[0049] The cooling chamber 7 contains engine oil 8, and the oil injection cooling mechanism cools the engine oil 8 and sprays it onto the piston 5.

[0050] The oil injection cooling mechanism includes an oil pump 16, a fuel injector 12, an oil cooler 13, and a thermocouple 15. The oil inlet of the oil pump 16 is connected to the oil 8 in the cooling chamber 7, and the oil outlet of the oil pump 16 is connected to the fuel injector 12 via an oil outlet pipe. The oil cooler 13 is installed on the oil outlet pipe, and the sensing end of the thermocouple 15 is located in the oil 8. The oil injection cooling control unit 20 is connected to the control terminals of the oil pump 16, the oil cooler 13, and the thermocouple 15 via signal cables. The oil injection cooling control unit 20 is also connected to the main control unit 21 via a signal cable.

[0051] The oil injection cooling control unit 20 regulates the flow rate of oil pump 16 to the oil outlet line, thereby regulating the flow rate of oil injected by the injector 12 into the piston 5. The oil injection cooling control unit 20 also regulates the cooling effect of the oil cooler 13 on the oil flowing through the oil outlet line. Thermocouple 15 senses the temperature of the oil 8 in the cooling chamber 7 in real time and transmits this information to the oil injection cooling control unit 20. Thus, the main control unit 21, through the oil injection cooling control unit 20, injects oil at a set flow rate and temperature into the piston 5 to achieve precise and quantitative cooling of the piston 5.

[0052] The thermometer 22 is used to sense the temperature of the top sidewall of the piston 5. The thermometer 22 is connected to the main control unit 21 via a signal cable. The thermometer 22 senses the temperature of the top sidewall of the piston 5 and uploads it to the main control unit 21.

[0053] In this design, a window is opened on the side of the cylinder liner 4 within the sliding stroke range of the piston 5, and the sensing end of the thermometer 22 faces the window to sense the temperature of the top sidewall of the piston 5. It should be noted that the temperature of the top sidewall of the piston 5 is basically the same as the temperature of the upper part of the top surface of the piston 5.

[0054] Camera 10 is installed inside heating chamber 1. Camera 10 is a CCD camera, with its camera end facing the upper port of baffle 3. Camera 10 captures images of the top surface of piston 5 through baffle 3. Camera 10 is connected to image acquisition unit 17 via a signal cable, and image acquisition unit 17 is connected to main control unit 21 via a signal cable. The images of the top surface of piston 5 captured by camera 10 in real time are acquired by image acquisition unit 17 and uploaded to main control unit 21 for image processing to record whether cracks have formed on the top surface of piston 5, the time of crack formation, and the crack propagation state.

[0055] A test method for real-time testing of piston thermomechanical fatigue, using the test apparatus for real-time testing of piston thermomechanical fatigue described in this embodiment, includes the following steps:

[0056] Step 1: The main control unit 21 adjusts the laser emitter 9 to emit laser beams with different pulse intensities via the laser heating control unit 18. The temperature of the top side wall of the piston 5 is sensed by the thermometer 22 and uploaded to the main control unit 21. The main control unit 21 processes the data to obtain the "relationship curve between laser beam pulse intensity and piston 5 top surface temperature".

[0057] Step 2: The main control unit 21 adjusts the laser emitter 9 to emit a laser beam with a set pulse intensity according to the "relationship curve between laser beam pulse intensity and piston 5 top surface temperature" via the laser heating control unit 18 to heat the top surface of piston 5. The main control unit 21 triggers the oil injection cooling mechanism via the oil injection cooling control unit to cool the oil 8 and spray it onto piston 5, keeping the top surface of piston 5 at the set temperature.

[0058] At the same time, the temperature of the top side wall of the piston 5 is sensed by the temperature measuring instrument 22 and uploaded to the main control unit 21 to verify the temperature of the top surface of the piston 5;

[0059] At the same time, the main control unit 21 triggers the piston drive mechanism 14 through the mechanical load loading control unit 19 to drive the piston 5 to move linearly back and forth along the cylinder liner 4. When the piston 5 moves to the upper end of the cylinder liner 4, the top surface of the piston 5 contacts the baffle 3 and applies a set pressure to the top surface of the piston 5.

[0060] At the same time, the camera 10 captures real-time images of the top surface of the piston 5 to record whether cracks are generated on the top surface of the piston 5, the time when cracks are generated, and the state of crack propagation.

[0061] Step 3: Stop when the piston 5 completes the set number of reciprocating motions along the cylinder liner 4.

[0062] in,

[0063] In step 2, the mechanical load (the set pressure applied to the top surface of piston 5) and the temperature load (the top surface of piston 5 being kept at a set temperature) are phase-matched so that when the temperature of the top surface of piston 5 reaches its maximum, the stress on the top surface of piston 5 simultaneously reaches its maximum value, and when the temperature reaches its minimum, the stress simultaneously reaches its minimum value. The mechanical load and temperature load immediately switch after reaching their maximum values. After multiple cycles, the occurrence of cracks on the top surface of piston 5, the time of crack initiation, and the state of crack propagation are recorded in real time, and the number of cycles is recorded.

[0064] Alternatively, in step 2, the phase matching of the mechanical load and temperature load on the top surface of piston 5 is adjusted so that when the temperature of the top surface of piston 5 reaches its highest value, the stress on the top surface of piston 5 simultaneously reaches its maximum value, and when the temperature reaches its lowest value, the stress simultaneously reaches its minimum value. After the mechanical load and temperature load reach their maximum values, they are held for a certain period of time before being switched. After multiple cycles, the occurrence of cracks on the top surface of piston 5, the time of crack initiation, and the state of crack propagation are recorded in real time, and the number of cycles is recorded.

[0065] The present invention has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the experimental apparatus and method for real-time testing of piston thermomechanical fatigue of the present invention. The experimental apparatus and method for real-time testing of piston thermomechanical fatigue of the present invention are applicable to the thermomechanical fatigue life test of the piston top surface of small and medium-sized gasoline engines, diesel engines, and natural gas engines; laser heating, oil control, and a thermometer are used to maintain the piston top surface at a set temperature to simulate the temperature load caused by the high temperature generated by the combustion of internal combustion engine gas; the piston top surface is in contact with the baffle 3 to apply a set pressure to the piston top surface to simulate the mechanical load caused by the internal combustion engine gas pressure; thus, the piston is accurately and efficiently simulated under different thermo-mechanical coupling loading conditions; a camera 10 and an image acquisition unit 17 are used to monitor the generation and propagation of cracks on the piston top surface in real time to test the thermomechanical fatigue life of the piston top surface, providing design criteria for piston optimization and improvement.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. 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.

Claims

1. A testing device for real-time testing of piston thermomechanical fatigue, characterized in that: It includes cylinder liners, pistons, piston drive mechanisms, heating chambers, cooling chambers, laser emitters, oil injection and cooling mechanisms, cameras, mechanical load loading control units, laser heating control units, oil injection and cooling control units, temperature measuring instruments, image acquisition units, and main control units; The piston is slidably fitted inside the cylinder liner, and the piston drive mechanism is connected to the piston for transmission. The piston drive mechanism drives the piston to perform linear reciprocating motion along the cylinder liner. The upper port of the cylinder liner is connected to the heating chamber, and the lower port of the cylinder liner is connected to the cooling chamber; The bottom of the heating chamber is provided with a baffle, and the portion of the baffle corresponding to the upper port is made of transparent material; The laser emitter is installed in the heating chamber. The laser beam emitted by the laser emitter passes through the portion of the baffle corresponding to the upper port and continues to irradiate the top surface of the piston. The cooling chamber contains engine oil, and the oil injection cooling mechanism cools the engine oil and sprays it onto the piston. The camera's camera end faces the portion of the baffle corresponding to the upper port; The control end of the piston drive mechanism is connected to the mechanical load loading control unit via a signal cable, and the mechanical load loading control unit is connected to the main control unit via a signal cable. The control terminal of the laser emitter is connected to the laser heating control unit via a signal cable, and the laser heating control unit is connected to the main control unit via a signal cable. The control terminal of the fuel injection cooling mechanism is connected to the fuel injection cooling control unit via a signal cable, and the fuel injection cooling control unit is connected to the main control unit via a signal cable. The thermometer is used to sense the temperature of the piston top sidewall, and the thermometer is connected to the main control unit via a signal cable; The camera is connected to the image acquisition unit via a signal cable, and the image acquisition unit is connected to the main control unit via a signal cable.

2. The test apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The piston drive mechanism is configured as a hydraulic cylinder, and the telescopic rod end of the hydraulic cylinder is connected to the piston pin seat via a piston pin.

3. The test apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The outer contour of the baffle located on one side of the cylinder liner matches the shape of the piston top surface.

4. The test apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: It also includes a beam splitter set in the heating chamber, and the laser beam emitted by the laser emitter first passes through the beam splitter to change direction before passing through the portion of the baffle corresponding to the upper port.

5. The testing apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The oil injection cooling mechanism includes an oil pump, a fuel injector, an oil cooler, and a thermocouple. The oil pump's inlet is connected to the oil in the cooling chamber, and the oil pump's outlet is connected to the fuel injector via an outlet pipe. The oil cooler is installed on the outlet pipe. The thermocouple's sensing end is located in the oil. The oil injection cooling control unit is connected to the control end of the oil pump, the control end of the oil cooler, and the thermocouple via signal cables.

6. The testing apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: A window is opened on the side of the cylinder liner within the piston's sliding stroke range, and the sensing end of the temperature measuring instrument faces the window.

7. The test apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The portion of the baffle corresponding to the upper port is made of quartz glass.

8. The test apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The mechanical load loading control unit, laser heating control unit, oil spraying cooling control unit, image acquisition unit, and main control unit are all configured as computers.

9. The testing apparatus for real-time testing of piston thermomechanical fatigue according to claim 1, characterized in that: The camera is a CCD camera.

10. A method for real-time testing of piston thermomechanical fatigue, using the testing apparatus for real-time testing of piston thermomechanical fatigue as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: The main control unit adjusts the laser emitter to emit laser beams with different pulse intensities via the laser heating control unit. The temperature of the piston top sidewall is sensed by the thermometer and uploaded to the main control unit. The main control unit processes the data to obtain the "relationship curve between laser beam pulse intensity and piston top surface temperature". Step 2: The main control unit adjusts the laser emitter to emit a laser beam with a set pulse intensity according to the "relationship curve between laser beam pulse intensity and piston top surface temperature" through the laser heating control unit to heat the piston top surface. The main control unit triggers the oil injection cooling mechanism through the oil injection cooling control unit to cool the oil and spray it onto the piston, keeping the piston top surface at the set temperature. Simultaneously, the temperature of the piston top sidewall is sensed by a thermometer and uploaded to the main control unit to verify the temperature of the piston top surface; At the same time, the piston drive mechanism is triggered by the main control unit through the mechanical load loading control unit, which drives the piston to move linearly and reciprocally along the cylinder liner. When the piston moves to the upper end of the cylinder liner, the piston top surface contacts the baffle and applies a set pressure to the piston top surface. Meanwhile, the camera captures real-time images of the piston top surface to record whether cracks appear on the piston top surface, the time when cracks appear, and the state of crack propagation. Step 3: Stop when the piston completes the set number of reciprocating motions along the cylinder liner.

Images