A testing machine and method for evaluating the wear life of graphite sealing materials

Abstract

The present invention relates to the field of aeroengines, and specifically to a testing machine and method for evaluating the wear life of graphite sealing materials. A high-speed ring block wear testing machine and a PV accelerated test method are used to solve the problems existing in the prior art, such as insufficient sliding linear speed of the friction pair, inconsistency between the loading and lubrication methods and the actual working conditions, and a long evaluation cycle for the wear life of the graphite sealing material. The testing machine includes a rotating spindle, a rotating disk, a precision loading and feeding table, an oil circuit lubrication system, a data acquisition system, and a computer, etc. The PV value acceleration method is used to increase the load and linear speed during the test process to increase the PV value of the friction pair, thereby realizing an accelerated wear assessment of the wear life of the graphite sealing material to be tested. The testing machine can achieve the high linear speed, radial fixed loading, and oil lubrication state required for the graphite sealing pair. The test adopts the PV accelerated test method, which is particularly suitable for the accelerated assessment of the long life of sealing materials such as graphite, and can effectively shorten the time required for the life test, with economic benefits.

Description

Technical Field

[0001] The present invention relates to the field of aeroengines, and in particular to a testing machine and method for evaluating the wear life of graphite sealing materials. The testing machine and method are suitable for studying the friction and wear performance of graphite sealing materials under high-speed, oil-lubricated working conditions, and are particularly suitable for simulating the service conditions of graphite sealing devices in aeroengine gearboxes and accessories, and for accelerating the assessment and evaluation of the wear life of graphite sealing materials. Background Art

[0002] The continuous improvement of aircraft engine performance has not only led to the gradual deterioration of the service conditions of sealing devices, but also posed more severe challenges to leakage characteristics, friction and wear performance and long life requirements. At present, the graphite seals widely used in aircraft engine gearboxes and accessories have a relative speed between the metal dynamic ring and the graphite static ring of up to tens to hundreds of meters per second. The sealing surfaces are lubricated by oil mist spray or sputtering with a certain temperature. It is required that there is no leakage or leakage is tolerable, and the graphite sealing device is required to have the same life as the aircraft engine. Existing studies have shown that the strong frictional heat effect caused by high sliding linear speed has completely different effects on the temperature rise of the contact surface, the oxidation of the friction pair material and the friction and wear behavior under conventional low-speed tribological conditions. Therefore, it is necessary to carry out tribological behavior research on graphite sealing materials under the premise of simulating the high linear speed of graphite seals as much as possible to obtain meaningful results.

[0003] Due to the harsh working conditions, there is currently no standard testing machine for studying the friction and wear behavior of graphite sealing materials. Although some existing high-speed wear testing machines have a sliding linear speed of up to hundreds of meters per second, their main purpose is to simulate the tribological conditions of the sealing coating and the dual blades in the air path seal of an aircraft engine. Their main feature is intermittent contact under dry friction conditions, so they cannot simulate the oil mist sputtering lubrication conditions in the service of graphite seals; in addition, their loading method is displacement loading, and the normal load between the friction pairs is not a constant value, which is quite different from the fixed load between the friction pairs caused by the spring force or magnetic force loading in the graphite seal.

[0004] To have the same lifespan as aircraft engines means that the wear life of graphite sealing materials must reach several thousand or even tens of thousands of hours, which requires an accelerated test method that can accurately and quickly evaluate its wear life. Currently, there is no standard accelerated wear life assessment test method. In sealing research, although there is also the accelerated wear of the graphite sealing material to be tested by increasing the PV value of the friction pair (the product of contact stress and linear velocity), the relationship between the change in PV value and the effect of wear volume is not clear. Obviously, the above brings great difficulties to the evaluation of the long life of graphite sealing materials. In engineering, only the bench test assessment method can be adopted, which greatly increases the cost. At the same time, due to the many interference factors, it also brings certain difficulties to the analysis of the wear mechanism. Summary of the invention

[0005] The purpose of the present invention is to provide a testing machine and method for evaluating the wear life of graphite sealing materials, so as to solve the problems existing in the prior art, such as insufficient linear velocity of friction pair movement, inconsistency between lubrication state and loading mode and actual working conditions and inability to simulate the working conditions of aircraft engine gearbox and casing accessory sealing device, and lack of accelerated test method for evaluating the wear life of graphite sealing materials.

[0006] The technical solution of the present invention is:

[0007] A test machine for evaluating the wear life of graphite sealing materials, the test machine comprises a rotating spindle, a rotating disk, a precision loading and feeding table, an oil circuit lubrication system, a data acquisition system and a computer, and the specific structure is as follows: the rotating disk is installed on the rotating spindle as a rotating sample, a translation sample is installed on the precision loading and feeding table, the precision loading and feeding table is placed on one side of the rotating spindle, the translation sample and the rotating sample are arranged opposite to each other to form a pair of friction pairs, and an oil nozzle of the oil circuit lubrication system is arranged above the translation sample and the rotating sample; the input end of the data acquisition system is connected to the test system, the output end of the data acquisition system is connected to the input end of the computer, the output end of the computer is connected to the numerical control system through an actuator, and the numerical control system is respectively connected to the servo motor of the precision loading and feeding table, the spindle motor, and the oil pump of the oil circuit lubrication system.

[0008] The test machine for evaluating the wear life of graphite sealing materials has a test system comprising: a force sensor on a precision loading and feeding table, a thermocouple and a flow meter on an oil lubrication system, and a rotation speed sensor on a rotating spindle.

[0009] The testing machine for evaluating the wear life of graphite sealing materials is characterized in that a rotating disk is installed on a rotating main shaft between bearing brackets, two vertical supporting bearing seats are relatively parallelly arranged on the bearing brackets, the rotating main shaft horizontally passes through the bearings on the two supporting bearing seats, protective covers are arranged on both sides of the rotating disk, the rotating disk is installed on the rotating main shaft between the two supporting bearing seats, one end of the rotating main shaft is transmission-connected to the output end of the main shaft motor through a coupling, a speed sensor is installed on the other end of the rotating main shaft, and the rotating main shaft adopts an electric spindle direct drive mode.

[0010] The test machine for evaluating the wear life of graphite sealing materials has an oil circuit lubrication system including an oil storage tank, an agitator, a heater, a thermocouple, an oil pump, a flow meter, and an oil injector. A heater, agitator, a thermocouple, and an oil pump are arranged in the lower part of the oil storage tank, and the flow meter is arranged on the oil pipeline from the oil pump to the oil injector.

[0011] The test machine for evaluating the wear life of graphite sealing materials, the precision loading and feeding table includes a servo motor, a translational sample holder and a force sensor, a groove is provided on one side of the translational sample holder, the translational sample is installed in the groove, the top output end of the servo motor is connected to the bottom of the translational sample holder, the servo motor drives the translational sample to move left and right away from or close to the rotating disk through the translational sample holder, two force sensors are installed on the translational sample holder, and the force sensors correspond to the back and bottom surfaces of the translational sample respectively; the force sensor on the precision loading and feeding table transmits the obtained normal force information to the computer through the data acquisition system, and the computer realizes closed-loop control of the servo motor.

[0012] A method for evaluating the wear life of a graphite sealing material, using a PV value acceleration method, increases the PV value of a friction pair by increasing the load and line speed during the test, and realizes an accelerated wear assessment of the wear life of the graphite sealing material to be tested, comprising the following steps:

[0013] (a) According to the service conditions of the graphite sealing material to be tested, determine the initial test conditions, including the normal load F 0 , contact stress P 0 , sliding linear velocity V 0 , test temperature T 0 , lubrication status and wear life t l Corresponding limit wear amount W l , where the contact stress P 0 According to the line-surface contact form of Hertz contact, the normal load F 0 Calculated;

[0014] (b) Determine the initial test conditions and conduct t 0 After the long wear test (corresponding wear distance is S 0 ), and determine the specific wear rate W of the graphite sealing material to be tested based on the test results. r0 and wear mechanisms;

[0015] (c) While maintaining the test temperature T 0 Under the premise that the lubrication state is consistent with the initial condition, the normal load (contact stress) and / or the sliding line speed are increased respectively to determine the acceleration normal load F i (The corresponding contact stress is P i ), Accelerate the sliding linear velocity V i Next, proceed to 0 After a long wear test (corresponding wear distance is S i ), determine the specific wear rate W of the graphite sealing material to be tested under this condition ri and wear mechanisms, where the accelerating contact stress P i According to the line-surface contact form of Hertz contact, the acceleration normal load Fi Calculated;

[0016] (d) Determine the acceleration factor k i and accelerated wear test time t i ;

[0017] (e) Under the accelerating contact stress P i , Accelerate the sliding linear velocity V i , test temperature T 0 Under the condition that the lubrication state is consistent with the initial test conditions, t i After a long accelerated wear test, determine the wear amount W of the graphite sealing material to be tested i ;

[0018] (f) Compare W i With W l , to determine whether the graphite sealing material to be tested meets the life requirements.

[0019] The method for evaluating the wear life of graphite sealing materials, the initial wear test conditions in step (a), the test temperature T 0 It should be the same as the actual service condition, the limit wear amount W l It should be consistent with the actual service conditions or increase or decrease in proportion. The lubricating oil used should be consistent with the actual conditions, the flow rate should be consistent with the actual conditions or increase or decrease in proportion. The contact stress P 0 and sliding linear velocity V 0 should be the same as the actual service conditions, or ensure that the product of the two (P 0 V 0 ) is equal to the product of the actual working conditions.

[0020] The method for evaluating the wear life of graphite sealing materials, in step (b), the specific wear rate W r0 They are calculated by the following formulas:

[0021]

[0022]

[0023]

[0024] Where Δm is the wear mass (unit: mg), Δv is the wear volume (unit: mm 3 ), ΔL is the wear size (unit: mm), F 0 is the normal load (unit: N), S 0 is the wear distance (unit: m), W r0-1 , W r0-2 and W r0-3The physical meanings and units are: wear mass of the material to be tested under unit load and unit distance (unit: mg / (Nm)), wear volume of the material to be tested under unit load and unit distance (unit: mm 3 / (Nm)), wear size of the material to be tested under unit load and unit distance (unit: mm / (Nm)), according to actual needs, from W r0-1 , W r0-2 and W r0-3 Among them, select one of them as the required specific wear rate W r0 ;

[0025] In step (c), the specific wear rate W ri They are calculated by the following formulas:

[0026]

[0027]

[0028]

[0029] Where Δm is the wear mass (unit: mg), Δv is the wear volume (unit: mm 3 ), ΔL is the wear size (unit: mm), F 0 is the normal load (unit: N), S i is the wear distance (unit: m), W ri-1 , W ri-2 and W ri-3 The physical meaning and units are: wear mass per unit load per unit distance (unit: mg / (Nm)), wear volume per unit load per unit distance (unit: mm 3 / (Nm)), wear size per unit load per unit distance (unit: mm / (Nm)), according to actual needs, from W ri-1 , W ri-2 and W ri-3 Among them, select one of them as the required specific wear rate W ri ;

[0030] Compare the wear mechanisms under the initial test state in step (b) and the accelerated test state selected in step (c). If the wear mechanisms of the two are the same, proceed to step (d); otherwise, change the contact stress and sliding linear velocity and repeat step (c) until the wear mechanism under the selected accelerated state is the same as the initial state.

[0031] The method for evaluating the wear life of graphite sealing materials, in step (d), the acceleration factor k i , Accelerated wear test time t i , respectively calculated by the following formula:

[0032]

[0033]

[0034] In the formula, the acceleration coefficient k i is a dimensionless number, the initial specific wear rate W of the graphite sealing material to be tested r0 (Unit: mg / (Nm) or mm 3 / (Nm) or mm / (Nm)), the accelerated wear rate W of the graphite sealing material to be tested ri (Unit: W r0 The unit is consistent); Accelerated wear test time t i (Unit: h), wear life t l (Unit: h), Acceleration contact stress P i (Unit: MPa), accelerated sliding speed V i (Unit: m / s), contact stress P 0 (Unit: MPa), sliding line speed V 0 (Unit: m / s).

[0035] The method for evaluating the wear life of graphite sealing materials, in step (f), comparing W i With W l , when W i <W l When , it indicates that the wear amount W of the graphite sealing material to be tested is within the required service time. i Less than the limit wear amount W l , it is considered that the wear life of the graphite sealing material to be tested meets the requirements; otherwise, it does not meet the requirements.

[0036] The advantages and beneficial effects of the present invention are:

[0037] (1) The present invention can realize high-speed and stable rotation of the rotating disk of the test machine, and the rotation speed is adjustable in the range of 240 to 10,000 r / min. The radius of the rotating disk is 0.2 m. The two are matched, and the relative linear speed of the friction pair can reach 5 to 209 m / s, which can simulate the high linear speed working conditions of the graphite sealing device of the aircraft engine and meet the research and evaluation needs;

[0038] (2) The present invention adopts the method of directly driving the rotating spindle with the electric spindle, which has high motion reliability and avoids the complex structure of the pulley transmission;

[0039] (3) The present invention can adopt a heating method combining stirring with PID regulation, which can heat a volume of 1.25L of lubricating oil from room temperature to 200°C with a temperature control accuracy of ±1°C, and can simulate the high-temperature lubrication requirements of the graphite sealing device of an aircraft engine.

[0040] (4) The present invention adopts a closed-loop control of flow meter → data acquisition system → computer → actuator → oil pump to achieve quantitative control of the lubricating oil supply to the friction pair contact surface with an accuracy of ±6 ml / min.

[0041] (5) The present invention adopts a closed-loop control of force sensor → data acquisition system → computer → actuator → servo motor to achieve controlled loading between friction pair specimens with an accuracy of ±1N.

[0042] (6) The present invention adopts modular design, has a reasonable overall layout, a compact structure, and a relatively low cost, and is suitable for laboratory use.

[0043] (7) The present invention provides a method for calculating an acceleration coefficient k, through which the acceleration test time can be determined more accurately.

[0044] (8) The present invention provides a PV accelerated test method, which can effectively shorten the assessment time of the wear life of graphite sealing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a design principle block diagram of the high-speed ring block testing machine of the present invention.

[0046] Figure 2 It is a schematic diagram of the system structure of the high-speed ring block testing machine of the present invention.

[0047] Figure 3 It is a schematic diagram of the rotating disk, high-speed rotating spindle and traditional system structure of the high-speed ring block testing machine of the present invention.

[0048] Figure 4 It is a schematic diagram of the structure of the oil circuit lubrication system of the high-speed ring block testing machine of the present invention.

[0049] Figure 5 It is a schematic diagram of a translational specimen and a precision loading and feeding table of a high-speed ring block testing machine of the present invention.

[0050] Figure 6 It is a technical flow diagram of the PV acceleration method of the present invention.

[0051] In the figure, 1 is a rotating spindle; 2 is a rotating disk; 3 is a protective cover; 4 is a translational specimen; 5 is a precision loading feed table; 6 is an oil nozzle; 7 is a flow meter; 8 is an oil storage tank; 9 is a heater; 10 is a thermocouple; 11 is an agitator; 12 is a data acquisition system; 13 is a computer; 14 is an actuator; 15 is a numerical control system; 16 is a speed sensor; 17 is a coupling; 18 is a support bearing seat; 19 is an oil pump; 20 is a force sensor; 21 is a servo motor; 22 is a translational specimen holder; 23 is a bearing holder; 24 is a spindle motor. DETAILED DESCRIPTION

[0052] The present invention is further explained in detail below with reference to the accompanying drawings.

[0053] like Figure 1-Figure 6 As shown, the present invention provides a testing machine for evaluating the wear life of graphite sealing materials. The testing machine consists of a rotating spindle 1, a rotating disk 2, a precision loading and feeding table 5, an oil lubrication system (an oil spray nozzle 6, a flow meter 7, an oil storage tank 8, a heater 9, a thermocouple 10, and an agitator 11), a data acquisition system 12, and a computer 13. The input end of the data acquisition system 12 is connected to a testing system (such as a force sensor 20 of the precision loading and feeding table, a thermocouple 10 and a flow meter 7 of the oil lubrication system, and a rotation speed sensor 16 on the rotating spindle 1, etc.), and the output end of the data acquisition system 12 is connected to the input end of the computer 13. The output end of the computer 13 is connected to a numerical control system 15 through an actuator 14. The numerical control system 15 is respectively connected to a servo motor 21, a spindle motor 24, and an oil pump 19. Design principle of the control testing machine ( Figure 1 ), constitute the system structure ( Figure 2 ) and its components and structures ( Figure 3 , Figure 4 and Figure 5 ) are explained as follows:

[0054] like Figure 2 As shown, the rotating disk 2 is installed on the rotating spindle 1 as a rotating specimen, and a translational specimen 4 is installed on the precision loading and feeding table 5. The precision loading and feeding table 5 is placed on one side of the rotating spindle 1. The translational specimen 4 and the rotating disk 2 are arranged opposite to each other to form a pair of friction pairs. An oil spray nozzle 6 is provided above the translational specimen 4 and the rotating disk 2 to realize oil dripping / oil spraying lubrication on the contact surface between the translational specimen 4 and the rotating disk 2.

[0055] The rotating disk 2 can be made of different materials according to actual needs. The rotating disk 2 is installed on the rotating spindle 1 between the bearing brackets 23. A protective cover 3 is arranged outside the rotating disk 2. The rotating spindle 1 is directly driven by an electric spindle. When the rotating sample rubs against the translational sample 4 on the rotation radius, the translational sample 4 moves continuously, intermittently or in combination along the radial direction of the rotating disk under the drive of the servo motor 21 to ensure that the radial load between the rotating disk 2 and the translational sample 4 is the set value.

[0056] like Figure 3 As shown, two vertical supporting bearing seats 18 are relatively parallel and arranged on the bearing bracket 23, the rotating main shaft 1 is horizontally penetrated by the bearings on the two supporting bearing seats 18, protective covers 3 are arranged on both sides of the rotating disk 2, and the rotating disk 2 is installed on the rotating main shaft 1 between the two supporting bearing seats 18. One end of the rotating main shaft 1 is transmission-connected to the output end of the main shaft motor 24 through a coupling 17, and a speed sensor 16 is installed on the other end of the rotating main shaft 1.

[0057] like Figure 4 As shown, the oil circuit lubrication system includes an oil storage tank 8, an agitator 11, a heater 9, a thermocouple 10 (temperature control sensor), an oil pump 19, a flow meter 7, and an oil injector 6. The heater 9, the agitator 11, the thermocouple 10, and the oil pump 19 are arranged at the lower part of the oil storage tank 8. The flow meter 7 is arranged on the oil pipeline from the oil pump 19 to the oil injector 6. The heater 9 heats the lubricating oil. The agitator 11 stirs the lubricating oil in the oil storage tank 8 evenly. The thermocouple 10 intelligently adjusts the heating process. The oil pump 19 and the flow meter 7 transport the lubricating oil in the oil storage tank 8 to the oil injector 6 at a set flow rate to achieve quantitative lubrication of the contact surface.

[0058] like Figure 5 As shown, the precision loading and feeding stage 5 includes a servo motor 21, a translational sample holder 22 and a force sensor 20. A groove is provided on one side of the translational sample holder 22, and the translational sample 4 is installed in the groove. The top output end of the servo motor 21 is connected to the bottom of the translational sample holder 22. The servo motor 21 drives the translational sample 4 to move left and right away from or close to the rotating disk 2 through the translational sample holder 22. Two force sensors 20 are installed on the translational sample holder 22, and the force sensors 20 correspond to the back and bottom surfaces of the translational sample 4 respectively. The force sensor 20 on the precision loading and feeding stage 5 can transmit the normal force information obtained to the computer 13 through the data acquisition system, and the computer 13 can realize closed-loop control of the servo motor 21.

[0059] During operation, the rotating disk 2 mounted on the rotating spindle 1, as a rotating specimen, rotates at high speed under the drive of the rotating spindle 1 to obtain the linear velocity required for the test. The translational specimen 4 mounted on the precision loading feed table 5 moves radially toward the rotating disk 2 under the drive of the servo motor 21. The high-speed rotation of the rotating disk 2 and the translation of the translational specimen 4, the coupling of the two constitutes a friction pair. The oil spray nozzle 6 sprays lubricating oil of a given flow rate and temperature to the contact surface between the rotating disk 2 and the translational specimen 4 to achieve oil spraying or dripping lubrication. The friction pair performs continuous, intermittent or combined friction at the required linear velocity and radial load. The test system includes a thermocouple 10 for measuring temperature, a flowmeter 7 for measuring flow rate, a force sensor 20 for measuring force, and a speed sensor 16 for measuring speed. The data obtained by the test system is input into the computer 13 after passing through the high-speed data acquisition system 12. The computer 13 first stores the obtained data, compares it with the set parameters, and adjusts it through the actuator 14 so that the parameters meet the set values ​​and the test is continued or terminated.

[0060] Thermocouple 10 → data acquisition system 12 → computer 13 → actuator 14 → numerical control system 15 → heater 9, to achieve heating, measurement and temperature control of the lubricating oil.

[0061] Flow meter 7 → data acquisition system 12 → computer 13 → actuator 14 → numerical control system 15 → oil pump 19, to achieve the control of the splashing flow rate.

[0062] Force sensor 20 → data acquisition system 12 → computer 13 → actuator 14 → numerical control system 15 → servo motor 21, to achieve the set loading between the friction pairs.

[0063] The high-voltage control of the test machine is completed by the numerical control system 15, and the rotating disk 2 is safely protected by a protective cover 3. The entire test machine adopts automatic numerical control combined with computing data acquisition, recording and processing, and is designed with overload (voltage overload and current overload) protection capabilities and safety protection capabilities.

[0064] like Figure 1 , Figure 6 As shown, the accelerated wear test method for evaluating the wear life of graphite sealing materials of the present invention adopts the PV value acceleration method, and increases the PV value of the friction pair by increasing the load and linear speed during the test process, thereby realizing the accelerated wear assessment of the wear life of the graphite sealing material to be tested, and includes the following steps:

[0065] (a) According to the service conditions of the graphite sealing material to be tested, determine the initial test conditions, including the contact stress P 0 (Unit: MPa), sliding linear velocity V 0 (Unit: m / s), test temperature T 0 (Unit: °C), lubrication status and wear life t l (Unit: h) Corresponding limit wear amount W l (Unit: mg or mm 3 or mm).

[0066] The initial wear test conditions in step (a) are as follows: 0 It should be the same as the actual service condition, the limit wear amount W l It should be consistent with the actual service conditions or increase or decrease in proportion. The lubricating oil used should be consistent with the actual conditions, the flow rate should be consistent with the actual conditions or increase or decrease in proportion. The contact stress P 0 and sliding linear velocity V 0 should be the same as the actual service conditions, or ensure that the product of the two (P 0 V 0 ) is equal to the product of the actual working conditions.

[0067] (b) Determine the initial test conditions and conduct t 0 (Unit: h) After the wear test, the specific wear rate W of the graphite sealing material to be tested is determined based on the test results. r0 and wear mechanisms;

[0068] In step (b), the specific wear rate Wr0 They can be calculated by the following formulas:

[0069]

[0070]

[0071]

[0072] Where Δm is the wear mass (unit: mg), Δv is the wear volume (unit: mm 3 ), ΔL is the wear size (unit: mm), contact stress P 0 (Unit: MPa), S 0 is the wear distance (unit: m), W r0-1 , W r0-2 and W r0-3 The physical meaning and units are: wear mass per unit load per unit distance (unit: mg / (Nm)), wear volume per unit load per unit distance (unit: mm 3 / (Nm)), wear size under unit load and unit distance (unit: mm / (Nm)), can be calculated from W according to actual needs. r0-1 , W r0-2 and W r0-3 Among them, select one as the required specific wear rate Wr 0 .

[0073] (c) While maintaining the test temperature T 0 (Unit: °C) and the lubrication state are consistent with the initial conditions, the normal load (contact stress) and / or sliding linear velocity are increased respectively to determine the acceleration normal load F i (The corresponding contact stress is P i ), Accelerate the sliding linear velocity V i (Unit: m / s), t 0 After a wear test of a certain length of time (unit: h), determine the specific wear rate W of the graphite sealing material under this condition. ri and wear mechanisms;

[0074] In step (c), the specific wear rate W ri They can be calculated by the following formulas:

[0075]

[0076]

[0077]

[0078] Where Δm is the wear mass (unit: mg), Δv is the wear volume (unit: mm3 ), ΔL is the wear size (unit: mm), P i is the accelerating contact stress (unit: MPa), S i is the wear distance (unit: m), W ri-1 , W ri-2 and W ri-3 The physical meaning and units are: wear mass per unit load per unit distance (unit: mg / (Nm)), wear volume per unit load per unit distance (unit: mm 3 / (Nm)), wear size under unit load and unit distance (unit: mm / (Nm)), can be calculated from W according to actual needs. ri-1 , W ri-2 and W ri-3 Among them, select one as the required specific wear rate Wr i .

[0079] Compare the wear mechanisms under the initial test state in step (b) and the accelerated test state selected in step (c). If the wear mechanisms of the two are the same, proceed to step (d); otherwise, change the contact stress and sliding linear velocity and repeat step (c) until the wear mechanism under the selected accelerated state is the same as the initial state.

[0080] (d) Determine the acceleration factor k i and accelerated wear test time t i ;

[0081] In step (d), the acceleration factor k i , Accelerated wear test time t i , respectively calculated by the following formula:

[0082]

[0083]

[0084] In the formula, the acceleration coefficient k i is a dimensionless number, the initial specific wear rate W of the graphite sealing material to be tested r0 (Unit: mg / (Nm) or mm 3 / (Nm) or mm / (Nm)), the accelerated wear rate W of the graphite sealing material to be tested ri (Unit: W r0 Accelerated wear test time t i (Unit: h), wear life t l (Unit: h), Acceleration contact stress P i (Unit: MPa), accelerated sliding speed V i (Unit: m / s), contact stress P 0(Unit: MPa), sliding line speed V 0 (Unit: m / s).

[0085] (e) Under the accelerating contact stress P i (Unit: MPa), accelerated sliding linear velocity V i (Unit: m / s), test temperature T 0 (Unit: °C) and the lubrication state is consistent with the initial test conditions. i After the accelerated wear test lasts for a period of h, the wear amount W of the graphite sealing material to be tested is determined. i .

[0086] The limit wear amount W in steps (a) and (e) l and wear amount W i Including but not limited to: wear mass (unit: mg), wear volume (unit: mm 3 ), wear size (unit: mm), etc., the required W can be determined according to actual needs. l and W i .

[0087] (f) Compare W i (Unit: mg / (Nm) or mm 3 / (Nm) or mm / (Nm)) and W l (Unit: W r0 to determine whether the graphite sealing material to be tested meets the life requirements.

[0088] In step (f), W is compared i With W l , when W i <W l When , it indicates that the wear amount W of the graphite sealing material to be tested is within the required service time. i Less than the limit wear amount W l , it is considered that the wear life of the graphite sealing material to be tested meets the requirements; otherwise, it does not meet the requirements.

[0089] Example

[0090] In the accessories of a certain type of domestic turboprop engine, a graphite ring (impregnated with inorganic salt graphite) and a high-temperature alloy counterpart (GH4169) form a dynamic seal pair, in which the thickness of the graphite ring is about 2mm. The typical service conditions of this dynamic seal pair are: contact stress of 0.1-0.15MPa, relative linear velocity of 60.1m / s, oil mist splash lubrication between the seals, Pegasus II lubricant, and oil temperature of 60-65℃. The service life is required to be t l Not less than 3000h, that is, after running for 3000h, the total wear of the graphite ring (wear depth / thickness) h lLess than 2mm.

[0091] If the engineering assessment and verification is directly carried out through engine test, the cost is high, the cycle is long, and there are many interference factors. Therefore, the high-speed ring block tester and PV value accelerated test method of the present invention are used to carry out accelerated wear tests simulating the working conditions of the graphite seal pair (high speed, oil mist splash lubrication), obtain the wear degree of the graphite ring within a given time, and finally evaluate whether it meets the 3000-hour long life.

[0092] First, by comparing the working conditions of the dynamic seal pair with the technical indicators of the high-speed ring block wear tester of the present invention, it can be seen that the technical indicators can completely cover the service conditions of the graphite seal pair. Therefore, the wear life of the graphite seal can be accelerated by the high-speed ring block tester according to the accelerated test method of the present invention. The accelerated evaluation method is as follows:

[0093] Step a: Determine the initial test conditions. Including: Normal load F 0 =10N, the corresponding contact stress P o =0.1MPa, relative linear velocity v 0 =60m / s, oil mist splash lubrication (Pegasus II), oil temperature 60℃.

[0094] Step b: Under the initial test conditions determined in step a, perform 0 = 2h wear test, the corresponding wear range S 0 =43200m. Under this condition, the wear amount (dimensional change in thickness direction) of the graphite material to be tested is h 0 =1.2μm, specific wear rate W ro =h 0 / (F 0 ·S 0 )=2.78 10 -7 μm / (Nm), and the main wear mechanisms are ploughing and abrasion.

[0095] Step c: Determine the acceleration condition P i and v i Under the conditions, t 0 =2h wear test, the specific wear rate and wear mechanism of the graphite material to be tested. To this end, the accelerated test conditions are determined to include:

[0096] Normal load F i =125N, the corresponding contact stress P i =1MPa, relative phase velocity v i =60m / s, wear time t 0 =2h, corresponding grinding process S i=43200m, oil mist splash lubrication (Pegasus II), oil temperature 60℃.

[0097] Under this condition, the wear amount of the graphite material to be tested (the change in the thickness direction) is h i-0 =13.5μm, specific wear rate W ri =h i-0 / (F i ·S i )=2.5 10 -6 μm / (Nm).

[0098] Comparing the wear mechanisms of the graphite material under the initial test conditions and the accelerated test conditions, both are plowing and abrasion, indicating that the accelerated test conditions are appropriately selected and the next step (step d) can be carried out.

[0099] Step d: Calculate the acceleration factor ki and the accelerated test time t i .in:

[0100] k i =W ri / W ro =8.99

[0101]

[0102] Step e: Under the accelerated conditions determined in step c, perform t i = 33.37 hours of accelerated wear test. Determine the wear amount (dimensional change in thickness direction) of the graphite material to be tested at this time i-i =1651μm.

[0103] Step f: Compare h l With h i-i , obviously h i-i (1651μm) <h l (2000μm), indicating that the wear life of the graphite sheet material under test meets the design requirements.

[0104] In order to further verify the results of the accelerated consideration, the graphite dynamic seals of engines with service life of 500h, 1500h and 3000h were disassembled, and the results showed that the wear depths of the graphite rings were 421μm, 823μm and 1198μm respectively. Comparing the accelerated test results (1651μm) with the actual operation results (1198μm), it can be seen that the PV accelerated test method of the present invention can not only greatly shorten the time for the long-life assessment of graphite seals, but also has a high accuracy of the test results.

[0105] From the above, it can be seen that the present invention adopts a high-speed ring block wear tester and a PV accelerated test method to solve the problems existing in the prior art, such as insufficient sliding linear speed of the friction pair, inconsistency between the loading and lubrication methods and the actual working conditions, and long wear life evaluation cycle of graphite sealing materials. The test machine can achieve the high linear speed, radial fixed loading and oil lubrication state required for the graphite sealing pair. The test adopts the PV accelerated test method, which is particularly suitable for the accelerated assessment of the long life of sealing materials such as graphite, and can effectively shorten the time required for life testing, with economic benefits.

Claims

1. A method for evaluating the wear life of a graphite sealing material, characterized in that: The test machine for evaluating the wear life of graphite sealing materials includes a rotating spindle, a rotating disk, a precision loading and feeding table, an oil circuit lubrication system, a data acquisition system and a computer, and the specific structure is as follows: the rotating disk is installed on the rotating spindle as a rotating sample, and a translation sample is installed on the precision loading and feeding table, and the precision loading and feeding table is placed on one side of the rotating spindle. The translation sample and the rotating sample are arranged opposite to each other to form a pair of friction pairs, and an oil nozzle of the oil circuit lubrication system is arranged above the translation sample and the rotating sample; the input end of the data acquisition system is connected to the test system, the output end of the data acquisition system is connected to the input end of the computer, and the output end of the computer is connected to the numerical control system through an actuator, and the numerical control system is respectively connected to the servo motor of the precision loading and feeding table, the spindle motor, and the oil pump of the oil circuit lubrication system; The method for evaluating the wear life of graphite sealing materials adopts the PV value acceleration method, which increases the PV value of the friction pair by increasing the load and linear speed during the test, thereby realizing the accelerated wear assessment of the wear life of the graphite sealing material to be tested, and includes the following steps: (a) According to the service conditions of the graphite sealing material to be tested, determine the initial test conditions, including normal load F0, contact stress P0, sliding linear velocity V0, test temperature T0, lubrication state and wear life t l Corresponding limit wear amount W l , where the contact stress P0 is calculated from the normal load F0 according to the line-surface contact form of Hertzian contact; (b) Determine the initial test conditions, after the wear test for a time of t0, the corresponding wear distance is S0, and determine the specific wear rate W of the graphite sealing material to be tested based on the test results r0 and wear mechanisms; (c) Under the premise of keeping the test temperature T0 and lubrication state consistent with the initial conditions, increase the normal load and / or sliding linear velocity respectively to determine the acceleration normal load F i , the corresponding contact stress is P i , and the accelerated sliding linear velocity V i Under the condition of t0, after the wear test, the corresponding wear distance is S i , determine the specific wear rate W of the graphite sealing material under this condition ri and wear mechanisms, where the accelerating contact stress P i According to the line-surface contact form of Hertz contact, the acceleration normal load F i Calculated; (d) Determine the acceleration factor k i and accelerated wear test time t i ; (e) Under the accelerating contact stress P i , Accelerate the sliding linear velocity V i t test under the condition that the test temperature T0 and lubrication state are consistent with the initial test conditions. i After a long accelerated wear test, determine the wear amount W of the graphite sealing material to be tested i ; (f) Compare W i With W l , to determine whether the graphite sealing material to be tested meets the life requirements; In step (d), the acceleration factor k i , Accelerated wear test time t i , respectively calculated by the following formula: In the formula, the acceleration coefficient k i is a dimensionless number; the initial specific wear rate W of the graphite sealing material to be tested r0 , unit: mg / Nm or mm 3 / Nm or mm / Nm; Accelerated wear rate W of the graphite sealing material to be tested ri , unit: W r0 The units are consistent; Accelerated wear test time t i , unit: h; wear life t l , unit: h; accelerated contact stress P i , unit: MPa; Acceleration sliding line speed V i , unit: m / s; contact stress P0, unit: MPa; sliding linear velocity V0, unit: m / s.

2. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: The test system includes: a force sensor on the precision loading feed table, a thermocouple and a flow meter on the oil lubrication system, and a speed sensor on the rotating spindle.

3. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: The rotating disk is installed on the rotating main shaft between the bearing supports. Two vertical supporting bearing seats are relatively parallel and arranged on the bearing supports. The rotating main shaft horizontally passes through the bearings on the two supporting bearing seats. Protective covers are arranged on both sides of the rotating disk. The rotating disk is installed on the rotating main shaft between the two supporting bearing seats. One end of the rotating main shaft is connected to the output end of the main shaft motor through a coupling. A speed sensor is installed on the other end of the rotating main shaft. The rotating main shaft adopts the direct drive mode of the electric spindle.

4. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: The oil lubrication system includes an oil storage tank, an agitator, a heater, a thermocouple, an oil pump, a flow meter, and an oil injector. A heater, an agitator, a thermocouple, and an oil pump are arranged in the lower part of the oil storage tank, and the flow meter is arranged on the oil pipeline from the oil pump to the oil injector.

5. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: The precision loading and feeding table includes a servo motor, a translational sample holder and a force sensor. A groove is provided on one side of the translational sample holder, and the translational sample is installed in the groove. The top output end of the servo motor is connected to the bottom of the translational sample holder. The servo motor drives the translational sample to move left and right away from or close to the rotating disk through the translational sample holder. Two force sensors are installed on the translational sample holder, and the force sensors correspond to the back and bottom surfaces of the translational sample respectively. The force sensor on the precision loading and feeding table transmits the obtained normal force information to the computer through the data acquisition system, and the computer realizes closed-loop control of the servo motor.

6. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: The initial wear test conditions in step (a) are as follows: the test temperature T0 should be the same as the actual service condition, and the limit wear amount W l It should be consistent with the actual service conditions or increase or decrease in proportion, the lubricating oil used should be consistent with the actual situation, the flow rate should be consistent with the actual situation or increase or decrease in proportion, the contact stress P0 and sliding line speed V0 should be the same as the actual service conditions, or ensure that the product of the two P0V0 is equal to the product of the actual conditions.

7. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: In step (b), the specific wear rate W r0 They are calculated by the following formulas: Where, Δm is the wear mass, unit: mg; Δv is the wear volume, unit: mm 3 ; ΔL is the wear size, unit: mm; F0 is the normal load, unit: N; S0 is the wear distance or wear distance, unit: m; W r0-1 , W r0-2 and W r0-3 The physical meaning and units are: wear mass of the material to be tested under unit load and unit distance, unit: mg / Nm, wear volume of the material to be tested under unit load and unit distance, unit: mm 3 / Nm, wear size of the material to be tested under unit load and unit distance, unit: mm / Nm, according to actual needs, from W r0-1 , W r0-2 and W r0-3 Among them, select one of them as the required specific wear rate W r0 ; In step (c), the specific wear rate W ri They are calculated by the following formulas: Where, Δm is the wear mass, unit: mg; Δv is the wear volume, unit: mm 3 ; ΔL is the wear size, unit: mm; F0 is the normal load, unit: N; S i is the grinding distance or wear distance, unit: m; W ri-1 , W ri-2 and W ri-3 The physical meaning and units are: wear mass per unit load per unit distance, unit: mg / Nm, wear volume per unit load per unit distance, unit: mm 3 / Nm, wear size per unit load per unit distance, unit: mm / Nm, according to actual needs, from W ri-1 , W ri-2 and W ri-3 Among them, select one of them as the required specific wear rate W ri ; Compare the wear mechanisms under the initial test state in step (b) and the accelerated test state selected in step (c). If the wear mechanisms of the two are the same, proceed to step (d); otherwise, change the contact stress and sliding linear velocity and repeat step (c) until the wear mechanism under the selected accelerated state is the same as the initial state.

8. The method for evaluating the wear life of a graphite sealing material according to claim 1, characterized in that: In step (f), W is compared i With W l , when W i <W l When , it indicates that the wear amount W of the graphite sealing material to be tested is within the required service time. i Less than the limit wear amount W l , it is considered that the wear life of the graphite sealing material to be tested meets the requirements; otherwise, it does not meet the requirements.

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