Bearing lubrication contact area oil film pressure measuring method and system
By mixing nanoscale pressure-sensitive quantum dots with lubricating oil in the bearing lubrication contact area, and combining photoluminescence properties and spectral analysis, the problem of oil film pressure measurement in the bearing lubrication contact area has been solved, achieving high-precision, non-invasive pressure monitoring suitable for complex working conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2026-01-29
- Publication Date
- 2026-04-21
AI Technical Summary
Existing technologies struggle to achieve high-precision, real-time, and non-invasive oil film pressure measurement in the bearing lubrication contact area. Traditional methods are prone to disrupting oil film continuity or having low signal-to-noise ratios, making them difficult to apply to bearing lubrication systems.
A test solution is formed by mixing nanoscale pressure-sensitive quantum dots with lubricating oil. The photoluminescence properties of the quantum dots are used to form an oil film in the bearing lubrication contact area. Non-contact pressure measurement is achieved by laser irradiation and spectral analysis. The oil film pressure is obtained by comparing the photoluminescence spectral characteristics with the calibration curve.
It achieves highly accurate and practical measurement of oil film pressure in the bearing lubrication contact area. Quantum dots have no effect on oil film thickness, are non-invasive and highly stable, and are suitable for extreme working conditions.
Smart Images
Figure CN121898679A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of bearing dynamics lubrication technology, and in particular to a method and system for measuring oil film pressure in the lubrication contact area of a bearing. Background Technology
[0002] Fluid lubrication of bearings is widely used in aerospace, automotive, and other fields. It is of significant practical importance for reducing lubrication friction and heat dissipation, thereby maintaining the high-speed and stable operation of mechanical equipment and extending system life. The pressure of the fluid in the lubrication contact area inside the bearing is a crucial parameter reflecting the rheological behavior and frictional response of the bearing contact area, directly affecting the bearing's lubrication performance and service life. However, due to the micron-scale characteristics of the lubricating oil film, complex and dynamic operating conditions (such as high speed and heavy load), and technological bottlenecks in sensor integration, achieving high-precision, real-time, and non-invasive oil film pressure measurement remains a significant challenge. Therefore, accurately acquiring the hydrodynamic contact pressure in the bearing lubrication contact area on a spatial scale compatible with the contact size is crucial for analyzing friction during bearing lubrication and ensuring the high-speed operation of equipment.
[0003] However, due to the extreme service conditions of bearing lubrication contact areas, characterized by micrometer-level pressure and GPa-level pressure, reliable detection methods for bearing lubrication contact pressure testing are lacking. Current pressure information testing for bearing lubrication contacts remains in the numerical simulation stage, making it difficult to accurately reproduce the dynamic coupling effects of real-world conditions. This leads to discrepancies between measurement results and actual results. Furthermore, detection technologies used for monitoring pressure in traditional hydrodynamic contact areas are difficult to apply to bearing lubrication systems. For example, thin-film sensors are fabricated using the resistive sensitivity of pressure-sensitive materials and deposited on friction surfaces to monitor contact area pressure. However, the thickness of these sensors is not negligible compared to the thickness of the lubricating oil film in the bearing lubrication contact area, easily disrupting the continuity of the complete oil film and affecting the bearing lubrication state. In addition, the fragility of the sensor structure makes it susceptible to failure under high shear stress. In the field of non-contact testing technology, optical testing methods using Raman spectroscopy to measure pressure distribution achieve non-contact measurement of hydrodynamic contact area pressure while avoiding impact on fluid morphology and equipment structure. However, this technology has an extremely low signal-to-noise ratio, and the detected fluid must be a strong Raman scatterer, making its engineering application difficult in bearing lubrication systems. Therefore, overcoming the current challenge of monitoring microscale and extremely high pressure in bearing lubrication contact, and realizing a non-contact bearing lubrication contact area pressure detection technology with high accuracy and practicality has become the key to current research in the field of bearing lubrication. Summary of the Invention
[0004] Based on the shortcomings of the existing technology, the present invention provides a method and system for measuring oil film pressure in the bearing lubrication contact area, which solves the problem that traditional hydrodynamic contact area pressure monitoring detection technology is difficult to apply to bearing lubrication systems.
[0005] The present invention adopts the following technical solution: In a first aspect, the present invention provides a method for measuring oil film pressure in the lubrication contact area of a bearing, comprising the following steps: The selection of piezoresistive quantum dots is based on their basic photoluminescence properties and their affinity for lubricating oil. The selected pressure-sensitive quantum dots are mixed with lubricating oil solution in a set ratio to obtain a test solution; the test solution is calibrated to obtain the corresponding photoluminescence spectrum characteristics of the pressure-sensitive quantum dots—pressure calibration curve; The test solution is added as a lubricating fluid to the lubrication contact area of the bearing under test. The lubricating fluid forms an oil film during the operation of the bearing under test. Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are collected. The oil film pressure in the lubrication contact area of the bearing under test is obtained by comparing the photoluminescence spectrum characteristics of the oil film with the photoluminescence spectrum characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots.
[0006] Preferably, the calibration of the test solution to obtain the corresponding photoluminescence spectral characteristics-pressure calibration curve of the pressure-sensitive quantum dot specifically includes the following steps: A pressure is applied to the test solution using a pressure testing device; the pressure testing device employs a diamond anvil. The solution pressure under different loading pressures is obtained by a pressure sensor placed inside the pressure testing device; Using different locations in the test solution as measurement points, the photoluminescence spectrum of each measurement point was collected, and the corresponding photoluminescence spectral features were extracted to obtain multiple recording points; By fitting multiple recording points, the photoluminescence spectral characteristics of the pressure-sensitive quantum dot—pressure calibration curve—were obtained.
[0007] Preferably, the bearing housing and the inner ring of the bearing under test are both made of transparent material.
[0008] Preferably, the step of irradiating the center of the lubrication contact area oil film of the bearing under test with a laser under different operating conditions and collecting the photoluminescence spectral characteristics of the oil film specifically includes the following steps: A monitoring platform is constructed, which includes a laser, an incident optical fiber, a receiving optical fiber, a first probe, a second probe, a spectrometer, and a PC. The output of the laser is connected to the first probe via the incident optical fiber, and the second probe and the spectrometer are connected via the receiving optical fiber. Under different operating conditions, the laser emits a laser beam, which shines through the first probe onto the center of the oil film in the lubrication contact area of the bearing under test, exciting the pressure-sensitive quantum dots to produce fluorescence. The fluorescence of the pressure-sensitive quantum dots is collected by a second probe and transmitted to a spectrometer through a receiving optical fiber. The spectrometer analyzes the fluorescence to obtain the photoluminescence spectrum. The photoluminescence spectrum features are extracted on the PC to obtain the photoluminescence spectrum features.
[0009] Preferably, based on the obtained solution pressure and combined with the quantum dot structure and morphology characteristics, the optical properties of the quantum dots and the quantum dot-lubricant ratio are adjusted to obtain the set ratio.
[0010] Preferably, the basic photoluminescence characteristics include photoluminescence energy, photoluminescence intensity, fluorescence peak-to-peak wavelength, and maximum half-width at half-maximum.
[0011] In a second aspect, the present invention provides a bearing lubrication contact area oil film pressure measurement system, comprising: The selection module is used to select piezoresistive quantum dots based on their basic photoluminescence properties and their affinity for lubricating oil. The calibration module is used to mix the selected pressure-sensitive quantum dots with the lubricating oil solution in a set ratio to obtain a test solution; the test solution is calibrated to obtain the corresponding photoluminescence spectrum characteristics of the pressure-sensitive quantum dots—pressure calibration curve; The acquisition module is used to add the test solution as a lubricating fluid to the lubrication contact area of the bearing under test. The lubricating fluid forms an oil film during the operation of the bearing under test. Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are acquired. The comparison module is used to compare the photoluminescence spectral characteristics of the oil film with the photoluminescence spectral characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots to obtain the oil film pressure in the lubrication contact area of the bearing under test.
[0012] Compared with the prior art, the above-mentioned at least one technical solution adopted by the present invention can achieve the following beneficial effects: This invention mixes pressure-sensitive quantum dots with a lubricating oil solution in a predetermined ratio to obtain a test solution. Compared with traditional pressure measurement methods, the quantum dots are nanoscale, making their impact on the thickness of the bearing lubricating oil film negligible and non-invasive. The test solution is added as a lubricating fluid to the lubrication contact area of the bearing under test, where it forms an oil film during bearing operation. This invention utilizes a testing technique based on the photoluminescence properties of quantum dots to mix pressure-sensitive quantum dots with a lubricating oil solution. The quantum dots can achieve pressure variation measurement within the GPa range, which is compatible with the extreme pressure environment of the oil film in the bearing contact area.
[0013] Under different operating conditions, a laser is irradiated onto the center of the oil film in the lubrication contact area of the bearing under test, and the corresponding photoluminescence spectral characteristics of the oil film are collected. The photoluminescence spectral characteristics of the oil film are compared with the photoluminescence spectral characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots to obtain the oil film pressure in the lubrication contact area of the bearing under test. This invention, based on the linear fitting characteristic of the spectral characteristics of quantum dots to pressure, realizes non-contact real-time monitoring of the pressure in the hydrodynamic contact area, and has higher versatility and stability. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 This is a schematic diagram of the pressure calibration of the quantum dot sensor of the present invention; Figure 2 This is a schematic diagram of the system structure of the present invention; Figure 3 This is a schematic diagram illustrating the pressure monitoring principle of the present invention; Figure 4 This is a flowchart of a method for measuring oil film pressure in the bearing lubrication contact area according to the present invention.
[0016] In the diagram: 1-bearing housing, 2-inner ring, 3-oil film, 4-laser, 5-first probe, 6-incident fiber, 7-second probe, 8-receiving fiber, 9-spectrometer, 10-PC end. Detailed Implementation
[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] In recent years, testing technologies based on the photoluminescence properties of quantum dots (such as quantum dot temperature detection technology) have been verified and developed, proving the feasibility and great potential of applying quantum dots to microscale testing. Therefore, extending their application to pressure monitoring in the bearing lubrication contact area and utilizing the pressure optical sensitivity properties of specific quantum dots to achieve precise measurement of bearing lubrication fluid pressure has great research prospects and application potential.
[0019] Therefore, the purpose of this invention is to provide a method for measuring the oil film pressure in the lubrication contact area of a bearing using nanoscale quantum dots. Based on the nanoscale size of quantum dots and their photoluminescence sensitivity to pressure, this method can accurately and efficiently detect the lubrication film pressure in the hydrodynamic contact area of a bearing, offering advantages such as high versatility and non-contact operation. (Refer to...) Figure 4 This includes the following steps:
[0020] S1: Quantum dots are selected based on their basic photoluminescence properties and their affinity for lubricating oil.
[0021] Reference Figure 1 Based on the fundamental photoluminescence properties of nano-quantum dots (photoluminescence energy, photoluminescence intensity, fluorescence peak wavelength, maximum half-width at half-maximum, etc.), and considering the affinity of quantum dots for lubricating oil solvents, quantum dot materials are selected. Generally, oleophilic, universal quantum dots are chosen to ensure solubility in various lubricating oils. Specific pressure-sensitive quantum dots are selected as pressure sensors; these are quantum dots with high fluorescence intensity and good pressure sensitivity.
[0022] S2: Mix the selected pressure-sensitive quantum dots with the lubricating oil solution in a set ratio to obtain the test solution; calibrate the test solution to obtain the corresponding photoluminescence spectrum characteristics of the pressure-sensitive quantum dots—pressure calibration curve.
[0023] Preliminary preparation of quantum dot materials was completed: a quantum dot solution was prepared, and the quantum dots, acting as sensors, were mixed with bearing lubricating oil to form a quantum dot-lubricating oil test solution. Based on an optical-pressure testing platform, the quantum dot solution was calibrated under different pressures, yielding a quantum dot photoluminescence spectral characteristic-pressure calibration curve. Finally, based on the obtained quantum dot pressure information feedback, and combined with the quantum dot structure and morphology characteristics, the optical properties of the quantum dots and the quantum dot-lubricating oil ratio were adjusted to obtain an optimal quantum dot-lubricating oil hybrid design scheme for photoluminescence-pressure sensing effect.
[0024] Selected quantum dots were mixed in a lubricating oil solution at a predetermined ratio to form the quantum dot-lubricating oil calibration solution (test solution) for pressure calibration. A pressure testing device (diamond anvil) was used to apply pressure to the calibration solution placed inside the device. The solution pressure parameters were acquired using a pressure sensor located inside the device. Four different locations within the calibration solution were selected as measurement points, and the photoluminescence spectra at each measurement point were collected. The solution pressure parameters under different pressures and the corresponding quantum dot photoluminescence spectral characteristic parameters were recorded. Based on the obtained recording points, a photoluminescence spectral characteristic-pressure calibration curve of the quantum dots was obtained.
[0025] Under specific pressures, pressure-sensitive photoluminescence characteristic parameters (spectral characteristics) are extracted from the recorded photoluminescence spectra of quantum dots in the oil film as indicators for pressure calibration. Taking the average emission energy and peak wavelength of quantum dots as examples: the average emission energy of quantum dots recorded when the photoluminescence intensity of the quantum dot spectrum reaches its maximum value is used as the photoluminescence energy of the spectrum under different pressures to evaluate the average emission energy and the standard deviation around the average value. The formula for calculating the photoluminescence energy is:
[0026] ; in, λ λ is the peak wavelength of the photoluminescence intensity curve. h Let be Planck's constant. c It is the speed of light.
[0027] The wavelength coordinates corresponding to the highest point of the quantum dot fluorescence peak in the quantum dot photoluminescence spectrum are used as the peak wavelength parameter. By evaluating the shift distance of the quantum dot peak wavelength under different pressures, the pressure sensitivity of the quantum dot is determined. Based on this, the quantum dot photoluminescence parameter recording points under different pressures are fitted to obtain the quantum dot photoluminescence spectral characteristics—the pressure calibration curve.
[0028] S3: Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are collected.
[0029] A prepared quantum dot-lubricating oil solution is used as the lubricating fluid and added to the internal lubrication area of the moving bearing, thereby forming a quantum dot-doped fluid lubrication film, i.e., an oil film, in the lubrication contact area of the bearing. A laser is used as the excitation source, and the excitation light is irradiated to the center of the bearing lubrication contact area. The nano-quantum dots in the oil film in the contact area are excited and generate pressure-related fluorescence. This fluorescence is transmitted through an optical fiber, analyzed by a spectrometer, and sent to a PC. The specific pressure-sensitive photoluminescence spectral characteristics in the spectral information are calculated and compared with the quantum dot photoluminescence spectral characteristics-pressure calibration curve to obtain the pressure parameters of the bearing lubrication contact area at this time, realizing real-time measurement of the pressure of the lubricating fluid film in the bearing contact area.
[0030] In this test procedure, the bearing housing and the bearing inner ring should be transparent to ensure the smooth transmission of laser and quantum dot fluorescence between the transmission optical fiber and the oil film in the bearing lubrication contact area.
[0031] S31: Quantum Dot-Lubricating Film Formation: Reference Figure 2 The prepared quantum dot-lubricating oil mixture is added to the oil tank as a lubricating fluid. The lubricating oil is delivered to the bearing part for lubrication by the oil pump. The bearing is started and rotates with the bearing rotor 2, which drives the lubricating oil into the bearing lubrication contact area, forming a quantum dot-doped lubricating oil film 3 between the rotor 2 and the outer ring 1 of the bearing.
[0032] S32: Construction of the synchronous monitoring platform: Using laser 4 as the excitation source, one end of incident fiber 6 is connected to the first probe 5, and the other end is connected to laser 4. The first probe 5 is aligned with the center of the lubricating oil film in the bearing lubrication contact area. The excitation light is transmitted through the incident fiber 6 and the first probe 5 to the center of the oil film in the bearing contact area through the transparent outer ring 1 of the bearing, which excites the pressure-sensitive quantum dot sensor mixed in the oil film to achieve photoluminescence. The photoluminescence emitted by the quantum dots is collected by the second probe 7 and the receiving fiber 8 and transmitted to the spectrometer 9. The spectral information is transmitted to the PC terminal 10 through the spectrometer.
[0033] S33: Real-time pressure monitoring: By changing the bearing operating conditions, the oil film pressure in the bearing contact area is altered, and the spectral information acquired by PC10 at this time is analyzed, referring to... Figure 3 The corresponding quantum dot photoluminescence spectral characteristics (photoluminescence energy or peak wavelength) are extracted and compared with the quantum dot photoluminescence spectral characteristics-pressure calibration curve to obtain the oil film pressure in the bearing lubrication contact area at this time, thus realizing the real-time measurement of the oil film pressure in the bearing contact area.
[0034] S4: Compare the photoluminescence spectrum characteristics of the oil film with the photoluminescence spectrum characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dot to obtain the oil film pressure in the lubrication contact area of the bearing under test.
[0035] This invention utilizes the photoluminescence properties of pressure-sensitive quantum dots under different pressures. Based on the principle that the photoluminescence spectral characteristics of quantum dots are approximately linearly related to the lubricating oil film pressure, real-time measurement of the lubricating oil film pressure in the bearing contact area is achieved. The quantum dots selected in this invention should make the photoluminescence spectral characteristics-pressure calibration curve approximately linear within a specific pressure range.
[0036] Based on the same concept, the present invention also provides a bearing lubrication contact area oil film pressure measurement system, including a selection module, a calibration module, an acquisition module and a comparison module.
[0037] The selection module is used to select varistor quantum dots based on their basic photoluminescence properties and their affinity for lubricating oil.
[0038] The calibration module is used to mix the selected pressure-sensitive quantum dots with the lubricating oil solution in a set ratio to obtain a test solution; the test solution is calibrated to obtain the corresponding photoluminescence spectral characteristics of the pressure-sensitive quantum dots—pressure calibration curve.
[0039] The acquisition module is used to add the test solution as a lubricating fluid to the lubrication contact area of the bearing under test. The lubricating fluid forms an oil film during the operation of the bearing under test. Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are acquired.
[0040] The comparison module is used to compare the photoluminescence spectral characteristics of the oil film with the photoluminescence spectral characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots to obtain the oil film pressure in the lubrication contact area of the bearing under test.
[0041] 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.
[0042] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for measuring oil film pressure in the lubrication contact area of a bearing, characterized in that, Includes the following steps: The selection of piezoresistive quantum dots is based on their basic photoluminescence properties and their affinity for lubricating oil. The selected pressure-sensitive quantum dots are mixed with the lubricating oil solution in a set ratio to obtain the test solution; The test solution was calibrated to obtain the corresponding photoluminescence spectral characteristics of the pressure-sensitive quantum dots—pressure calibration curve; The test solution is added as a lubricating fluid to the lubrication contact area of the bearing under test. The lubricating fluid forms an oil film during the operation of the bearing under test. Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are collected. The oil film pressure in the lubrication contact area of the bearing under test is obtained by comparing the photoluminescence spectrum characteristics of the oil film with the photoluminescence spectrum characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots.
2. The method for measuring oil film pressure in the lubrication contact area of a bearing as described in claim 1, characterized in that, The calibration of the test solution to obtain the corresponding photoluminescence spectral characteristics—pressure calibration curve of the pressure-sensitive quantum dots specifically includes the following steps: A pressure is applied to the test solution using a pressure testing device; the pressure testing device employs a diamond anvil. The solution pressure under different loading pressures is obtained by a pressure sensor placed inside the pressure testing device; Using different locations in the test solution as measurement points, the photoluminescence spectrum of each measurement point was collected, and the corresponding photoluminescence spectral features were extracted to obtain multiple recording points; By fitting multiple recording points, the photoluminescence spectral characteristics of the pressure-sensitive quantum dot—pressure calibration curve—were obtained.
3. The method for measuring oil film pressure in the lubrication contact area of a bearing as described in claim 1, characterized in that, The bearing housing and inner ring of the bearing under test are both made of transparent material.
4. The method for measuring oil film pressure in the lubrication contact area of a bearing as described in claim 1, characterized in that, The process of irradiating the center of the lubrication contact area oil film of the bearing under test with a laser under different operating conditions and collecting the photoluminescence spectral characteristics of the oil film specifically includes the following steps: A monitoring platform is constructed, which includes a laser, an incident optical fiber, a receiving optical fiber, a first probe, a second probe, a spectrometer, and a PC. The output of the laser is connected to the first probe via the incident optical fiber, and the second probe and the spectrometer are connected via the receiving optical fiber. Under different operating conditions, the laser emits a laser beam, which shines through the first probe onto the center of the oil film in the lubrication contact area of the bearing under test, exciting the pressure-sensitive quantum dots to produce fluorescence. The fluorescence of the pressure-sensitive quantum dots is collected by a second probe and transmitted to a spectrometer through a receiving optical fiber. The spectrometer analyzes the fluorescence to obtain the photoluminescence spectrum. The photoluminescence spectrum features are extracted on the PC to obtain the photoluminescence spectrum features.
5. The method for measuring oil film pressure in the lubrication contact area of a bearing as described in claim 2, characterized in that, Based on the obtained solution pressure, combined with the quantum dot structure and morphology characteristics, the optical properties of the quantum dots and the quantum dot-lubricant ratio are adjusted to obtain the set ratio.
6. The method for measuring oil film pressure in the lubrication contact area of a bearing as described in claim 1, characterized in that, The basic photoluminescence characteristics include photoluminescence energy, photoluminescence intensity, fluorescence peak-to-peak wavelength, and maximum half-width at half-maximum.
7. A bearing lubrication contact area oil film pressure measurement system, characterized in that, include: The selection module is used to select piezoresistive quantum dots based on their basic photoluminescence properties and their affinity for lubricating oil. The calibration module is used to mix the selected pressure-sensitive quantum dots with the lubricating oil solution in a set ratio to obtain the test solution. The test solution was calibrated to obtain the corresponding photoluminescence spectral characteristics of the pressure-sensitive quantum dots—pressure calibration curve; The acquisition module is used to add the test solution as a lubricating fluid to the lubrication contact area of the bearing under test. The lubricating fluid forms an oil film during the operation of the bearing under test. Under different operating conditions, the laser is irradiated to the center of the oil film in the lubrication contact area of the bearing under test, and the photoluminescence spectral characteristics of the oil film are acquired. The comparison module is used to compare the photoluminescence spectral characteristics of the oil film with the photoluminescence spectral characteristics of the pressure-pressure calibration curve of the pressure-sensitive quantum dots to obtain the oil film pressure in the lubrication contact area of the bearing under test.