An assembly pressure distribution real-time measurement system under extreme working conditions

Abstract

The application belongs to the technical field of mechanical assembly and sensing monitoring, and provides an assembly pressure distribution real-time measuring system under extreme working conditions. A flexible film sensor integrating multiple pressure measuring points and multiple temperature measuring points is provided; multiple pressure measuring points and multiple temperature measuring points are arranged in the working plane of the flexible film sensor according to certain rules and assembly requirements; the sensitive materials on the pressure measuring points and the temperature measuring points are resistive materials, the material resistance changes with pressure or temperature, and the pressure measuring points and the temperature measuring points use the same signal line network. The application measures the temperature and contact force change of the assembly part contact surface by using the flexible film sensor, is especially suitable for cold assembly, hot assembly and cold-hot assembly composite scenes, measures the contact force in the assembly process, records the change of the assembly contact force during the temperature recovery process of the part, and provides the information required for decision-making for component assembly and optimization.

Description

Technical Field

[0001] This invention relates to the field of mechanical assembly and sensing monitoring technology, and in particular to a real-time measurement system for assembly pressure distribution under extreme working conditions. Background Technology

[0002] In mechanical assembly, clearance fits, transition fits, and interference fits are commonly used. Interference fits often involve cold or hot assembly. The general process involves utilizing the dimensional changes caused by thermal expansion and contraction of the parts' materials, creating gaps in dimensions that cannot be properly fitted at room temperature. Once the parts return to their normal temperature, these gaps disappear, achieving an interference fit. During this process, the contact forces on the mating surfaces change due to temperature variations and altered contact conditions. Even with the same assembly process, components assembled using the same techniques may exhibit significant differences in contact force distribution, posing a constraint on assembly technology and requiring further verification of assembly reliability. Recording the changes in contact forces on the mating surfaces during cold and hot assembly, especially during the time-domain temperature recovery process, can provide crucial information for updating assembly technology and developing assembly solutions.

[0003] During equipment operation, abnormal vibrations, temperature changes, or overload conditions often lead to alterations in assembly pressure distribution or loosening at component assembly locations. In severe cases, this can alter the equipment's operating status or even cause failure. Currently, the main method is to periodically and manually inspect the connections of assembled components to ensure assembly pressure remains within the normal range. This method requires a considerable amount of time, especially in hard-to-reach areas, necessitating extended maintenance and inspection. Performing assembly pressure testing on critical assembly surfaces allows for real-time monitoring of the connection status, providing crucial information for equipment health monitoring.

[0004] Existing solutions are mainly divided into two types. One is to use theoretical calculation, that is, to calculate the shrinkage / expansion size of the part based on the material shrinkage rate, cooling / heating temperature and part size, and then calculate the contact force of the part. Since this method is based on theoretical calculation results, there are often differences between the results and the actual stress distribution on the contact surface.

[0005] The second method is to use pressure-sensitive paper to measure the contact force of the assembly surface. This method requires placing the pressure-sensitive paper on the assembly surface first, and then removing the pressure-sensitive paper after assembly to obtain the contact force and contact force distribution. Moreover, this method can only obtain the maximum value of the contact force of the assembly surface. The changes in contact force and contact force distribution during the part's temperature recovery process cannot be measured. When adjustments are needed to the bolts and other connections, this method will be more complicated.

[0006] A real-time assembly contact force measurement system displays the contact force of the assembly surfaces in real time during the assembly process and plots the contact force cloud map of the assembly surfaces in real time. This provides an effective reference for the establishment and improvement of assembly processes. More importantly, it reveals the changes in contact force during the temperature recovery process of cold assembly and hot assembly, providing information support for the exploration of cold / hot assembly processes. Summary of the Invention

[0007] To address the shortcomings of existing solutions, a real-time measurement system for assembly pressure distribution under extreme working conditions is designed to solve the current problems.

[0008] The technical solution of this invention is as follows: A real-time measurement system for assembly pressure distribution under extreme working conditions, comprising a flexible thin-film sensor integrating multiple pressure measuring points and multiple temperature measuring points; multiple pressure measuring points and multiple temperature measuring points are arranged in the working plane of the flexible thin-film sensor according to a certain pattern and assembly requirements; the sensitive materials on the pressure measuring points and temperature measuring points are all resistive materials, and the material resistance changes with pressure or temperature; the pressure measuring points and temperature measuring points use the same set of signal line networks; the voltage across the sensitive material or the current in the circuit is measured to calculate the material resistance; the pressure or temperature is calculated using a known pressure-resistance or temperature-resistance curve; the pressure measuring points and temperature measuring points can be interchanged; the signals collected by the flexible thin-film sensor are stored, uploaded, and displayed through a data acquisition device; based on the temperature data uploaded by the data acquisition device, the pressure data is compensated, and the pressure data is calculated, displayed, and plotted according to the pressure-resistance curve of the pressure measuring points; a time-domain curve of the pressure is plotted; and a cloud map of the contact force distribution on the assembly surface is plotted based on the location and pressure value of all pressure measuring points.

[0009] The signal line network includes m n-channel multiplexers; all pressure and temperature measuring points on the flexible thin-film sensor are divided into n measurement groups according to the wiring arrangement. Different measurement groups are controlled by a single set of n-channel multiplexers integrated within the data acquisition unit, where n = the number of measurement groups. The n-channel multiplexers control the connection and disconnection of each meridian in each measurement group to the analog interface. Time-division multiplexing or frequency-division multiplexing analog measurements are performed using m n-channel multiplexers. The same acquisition interface is used to measure the measuring points within multiple measurement groups, where m = the number of meridians in a single measurement group. The latitude lines within each measurement group are numbered from 0 to x according to their direction. Latitude lines with the same number in different measurement groups are connected to the same analog interface. The meridian lines in each measurement group are numbered from 0 to y. Meridians with the same number in different measurement groups are connected in parallel to the same analog output interface. The connection and disconnection of the measurement loops at each measuring point are controlled in a time-division manner using the n-channel multiplexers on the latitude lines, enabling sequential measurement of multiple measurement groups.

[0010] The flexible thin-film sensor is a thin sheet with a thickness of 50µm to 200µm and uniform thickness. Its thickness direction consists of multiple layers of polymer material substrate, sensing material at measurement points, and ultra-thin wires within the flexible thin-film sensor. In the contact area between the flexible thin-film sensor and the component assembly surface, the multiple layers of polymer material substrate are sealed with weather-resistant sealant. Based on the specific shape and curvature of the component assembly surface, and following the shortest path principle and the principle that the path is perpendicular to the curvature of the component assembly surface, all ultra-thin wires within the flexible thin-film sensor are encased in weather-resistant sealant. The weather-resistant sealant is applied in vertical strips following the curvature direction of the component assembly surface. The gaps between the strips serve as stress release areas and venting paths for the multiple layers of polymer material substrate. The vent is designed to be located at the outlet of the ultra-thin wires within the flexible thin-film sensor and is far from the low-temperature assembly components.

[0011] The polymer substrate of the flexible thin-film sensor is PTFE or PEEK, and weather-resistant adhesive is used between the multiple polymer substrates to fix the sensing material of the measuring point and the ultra-thin wires inside the flexible thin-film sensor.

[0012] The compensation process involves compensating the pressure measurement point signals based on the temperature measurement point signals. During signal acquisition, the temperature measurement point signals are collected periodically. Based on the pre-marked position coordinates of all temperature measurement points in the software and the real-time collected temperature values, the temperature distribution of the entire assembly surface is calculated and converted into coordinates. Similarly, the pre-marked position coordinates of the pressure measurement points in the software are mapped to the temperature distribution to obtain the specific temperature value of each pressure measurement point. The temperatures of all pressure measurement points are marked. In the next round of pressure signal calculation, the pressure curve at the corresponding temperature is used to fit each pressure measurement point.

[0013] The distribution of the pressure and temperature measuring points adopts a geometric topology, with at least 6 pressure and / or temperature measuring points evenly arranged around each bolt hole, and the distance between adjacent measuring points is less than or equal to 5 times the diameter of the measuring point.

[0014] The beneficial effects of this invention are as follows: This invention utilizes a flexible thin-film sensor to measure the temperature and contact force changes at the contact surfaces of assembled components. Compared to existing technologies, it requires fewer analog interfaces from the data acquisition unit without sacrificing acquisition accuracy, reducing the number by one-third to one-half. By setting up strip-shaped sealant and venting routes, the shear stress between the multiple substrates of the flexible thin-film sensor is released, resulting in good curvature fit between the flexible thin-film sensor and the assembly surface of the part, effectively preventing wrinkling of the thin-film sensor substrate. By specifically setting venting routes and vent positions, condensation and moisture are effectively prevented from entering the flexible thin-film sensor, reducing performance degradation caused by oxidation of the internal metal wires. It is particularly suitable for: 1. Scenarios involving cold assembly, hot assembly, and a combination of cold and hot assembly, measuring contact force during the assembly process and recording changes in assembly contact force as the temperature recovers, providing information needed for component assembly and optimization decisions; 2. Long-term installation on critical assembly surfaces of equipment to monitor assembly pressure at the assembly location, providing information needed for equipment health status analysis. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a flexible thin-film sensor and its wire interface;

[0016] Figure 2 This is a schematic diagram of a flexible thin-film sensor and an FPC data acquisition unit;

[0017] Figure 3 This is a partial structural diagram of the flexible thin-film sensor;

[0018] Figure 4 yes Figure 3 A magnified view of the area within the box;

[0019] Figure 5 This is an exploded view of the thickness direction of a portion of the flexible thin-film sensor structure;

[0020] Figure 6 This is an example of the installation of a flexible thin-film sensor in equipment;

[0021] Figure 7 This is a schematic diagram of the connection of the external data acquisition unit to the contact force measurement system.

[0022] Figure 8 This is a schematic diagram of the connection of an assembly contact force measurement system with an FPC data acquisition unit mounted on the sensor.

[0023] 0010 is the flexible thin-film sensor; 0011 is the analog interface; 0012 is the sensing material measurement point; 0013 is the latitude line; 0014 is the longitude line; 0015 is the vent; 0016 is the weather-resistant sealant; 0017 is the venting line; 0018 is the polymer material substrate; 0200 is the assembly part flange; 0300 is the interference fit position; 0400 is the FPC data acquisition unit installed on the polymer substrate of the flexible thin-film sensor; 0410 is the external data acquisition unit; 0500 is the computer with built-in signal processing software. Detailed Implementation

[0024] A real-time assembly pressure distribution measurement system under extreme operating conditions is provided. This system comprises a flexible thin-film sensor 0010 integrating multiple piezoresistive pressure sensors and multiple thermistor temperature sensors. A signal acquisition device for collecting signals from the flexible thin-film sensor and software for processing pressure and temperature signals are also included. This system measures interface contact pressure, particularly the assembly pressure distribution.

[0025] For example Figure 1 and Figure 6 In the illustrated embodiment, this embodiment is applied to the axial assembly of a cylindrical part. The assembly involves hot and cold assembly processes at the interference fit position 0300. The flexible thin-film sensor 0010 used has a total of 1920 sensitive material measuring points 0012, of which the innermost and outermost rings are temperature measuring points, and the remaining measuring points are pressure measuring points. All measuring points are divided into 12 measurement groups. Each measuring point has 16 meridians 0014 and 10 parallels 0013. The meridians and parallels of the 12 measurement groups are connected to the 16 analog inputs and 10 analog outputs of the same data acquisition unit. The data acquisition unit used has 16 12-channel multiplexers. The data acquisition unit controls all 12-channel multiplexers to open one channel at a time. This embodiment connects all 160 sensitive material measuring points (longitude 0014 and latitude 0013) of one measurement group to form a loop, enabling the analog interface 0011 of the data acquisition unit to perform time-division multiplexed voltage / current measurements. This allows for the calculation of the resistance values ​​of all 160 sensitive measuring points, and further calculations of the temperature / pressure values ​​for each point. The data acquisition unit cyclically controls all 12 multiplexers to activate different channels each time, thereby completing the pressure / temperature measurements and calculations for all sensitive material measuring points 0012 in the 12 measurement groups, achieving the goal of time-division multiplexing measurement of 1920 points. In this embodiment, 16 digital output interfaces and 26 analog interfaces are used to achieve time-division multiplexing measurement of 1920 points. Conventional methods require complex wire arrangements and at least 88 analog interfaces to achieve time-division multiplexing measurement of 1920 points.

[0026] The flexible thin-film sensor 0010 is a thin sheet with a thickness of 50-200 μm. In the thickness direction, it consists of a multi-layered polymer substrate 0018, a sensing material for measuring points, and ultra-thin wires within the flexible thin-film sensor. Its shape is as follows: Figure 1 As shown, it can be customized according to the shape of the assembly surface to be tested. The thin film substrate of the flexible thin film sensor 0010 is a material that is resistant to both high temperature and ultra-low temperature, such as PTFE and PEEK. Weather-resistant sealant 0016 is used to seal the multiple layers of substrate in the flexible thin film sensor 0010 in the area in contact with the assembly surface of the part.

[0027] Based on the specific shape, curvature, and wiring requirements of the measurement interface, multilayer thin-film materials often experience wrinkling of the inner layers due to differences in curvature between layers. Therefore, the optimal design for the sealant application between substrates is to apply the weather-resistant sealant in vertical strips following the curvature direction. The gaps between these strips serve as stress-relieving areas for the substrate and also act as venting lines 0017. This optimizes the wiring arrangement, venting lines 0017, and vent holes 0015 while preventing substrate bending and wrinkling. Furthermore, since the flexible thin-film sensor 0010 contains venting lines 0017, vent holes 0015 need to be designed to connect the internal air of the flexible thin-film sensor 0010 with the external air, further balancing the internal air pressure of the flexible thin-film sensor 0010. Since the flexible thin film sensor 0010 needs to come into contact with high-temperature and ultra-low-temperature components, this working condition often causes nearby gaseous water to condense and adhere to the surface of the components. Therefore, it is preferable to design the vent 0015 to the wiring outlet, that is, to be far away from the low-temperature assembly components, so as to avoid condensation water from seeping into the interior of the flexible thin film sensor 0010 and causing the wires to oxidize rapidly, resulting in performance degradation.

[0028] The designed software for pressure and temperature signal processing compensates for pressure measurement signals based on temperature measurement signals, calculates specific pressure values ​​based on pressure sensor signals, and plots a contact force distribution cloud map of the assembly surface based on the location and pressure values ​​of all pressure sensors, displays the pressure center, and performs bolt preload uniformity analysis. Specifically, during signal acquisition, temperature measurement signals are periodically acquired, and the temperature distribution of the entire assembly surface is calculated based on these signals. The temperatures of all pressure measurement points are marked, and in the subsequent round of pressure signal processing, the pressure curve at the corresponding temperature is used for each pressure measurement point to obtain a more accurate understanding of pressure distribution changes.

[0029] The flexible thin-film sensor 0010 features a high-density array of measuring points, preferably optimized according to a geometric topology, to achieve precise measurement of pressure distribution on the assembly plane. This allows for accurate measurement of the pressure distribution around the bolts and the assembly surface using a minimal number of measuring points, enabling precise plotting of the pressure changes over time on the assembly surface. Based on the heat dissipation characteristics of the assembled parts, temperature measuring points are evenly distributed in the areas of fastest and slowest temperature change. For example, the flange edge and center of the flange ring of the assembled part flange 0020 are the locations of fastest and slowest heat dissipation, respectively. By evenly distributing temperature measuring points around the edge and center, accurate temperature field cloud map calculations can be performed, providing accurate temperature compensation for the pressure measuring points.

[0030] The pressure and temperature measuring points integrated on the flexible thin-film sensor have various arrangement patterns. Figure 1 This is a schematic diagram of the sensor arrangement on the annular assembly surface. By changing the sensitive material at the measuring point during the fabrication of the flexible thin film sensor, the temperature sensor and pressure sensor can be arbitrarily replaced to suit different working conditions. Furthermore, flexible thin film sensors with different shapes and arrangement patterns can be customized according to the different shapes of the assembly surface.

[0031] All measuring points within the flexible thin-film sensor 0010 are divided into multiple measuring groups. Each measuring group uses a matrix arrangement, consisting of meridians 0014 and parallels 0013. Within each measuring group, a scanning strategy of synchronous parallels and asynchronous meridians is adopted (or vice versa). The number of meridians / parallels is the same within each measuring group. Meridians 0014 and parallels 0013 are arranged in combination to achieve the measurement of a large number of measuring points with fewer interfaces within each measuring group.

[0032] Different measurement groups are controlled by an integrated n-channel multiplexer (n = number of measurement groups). The n-channel multiplexer controls the connection and disconnection of each meridian 0014 in each measurement group with the analog input port. Using m n-channel multiplexers (m = number of meridians in a single measurement group), time-division multiplexing or frequency-division multiplexing analog measurements are performed, that is, the same set of acquisition interfaces is used to measure the measurement points in multiple measurement groups. The specific principle is as follows: the latitude lines 0013 in each measurement group are numbered from 0 to x according to their direction. Each latitude line 0013 with the same number is connected to the same analog input interface. Similarly, each meridian is numbered from 0 to y, and the meridians 0014 with the same number are connected in parallel to the same analog output interface. However, it is not necessary to use the n-channel multiplexer for control. The connection and disconnection of the measurement loop at the measurement point can be controlled by the n-channel multiplexer on the latitude line in a time-division manner, so that the measurement of each measurement group can be realized one by one.

[0033] The signal acquisition device can be configured as a standalone device using a conventional signal acquisition device 0410. This device can acquire signals from all integrated pressure and temperature sensors on the flexible thin-film sensor, converting analog signals into digital signals. The acquisition frequency is above 10Hz, and the signal resolution can reach 16-bit accuracy. The acquired signals can be stored, displayed, and transmitted via wired or wireless means. Preferably, the signal acquisition device hardware 0400 circuitry can be designed and printed on the flexible thin-film pressure sensor as a flexible printed circuit board (FPC). Utilizing the weather-resistant substrate of the flexible thin film and the printed circuitry, this design is suitable for applications with limited space, optimizing device wiring and layout.

[0034] The flexible thin-film sensor 0010 integrates multiple pressure and temperature measuring points. Signal line interfaces are led out from these points, and signal lines are used to electrically connect them to the signal acquisition unit. The signal acquisition unit collects the electrical signals returned by the pressure and temperature measuring points at a certain frequency, and stores, displays, and uploads these signals to the computer 0500. After uploading the collected electrical signals to the computer 0500, the software used for pressure and temperature signal processing analyzes the signals. After distinguishing between temperature and pressure signals, the temperature signals are first processed into temperature information, and a temperature distribution model is established for the entire flexible thin-film sensor based on the positions and temperature information of all temperature measuring points. Secondly, based on the temperature distribution model, all pressure measuring points are marked with temperature information according to their arrangement. Then, the pressure signal of each pressure measuring point is calculated based on the marked temperature information. Finally, a pressure cloud map is drawn according to the arrangement of all pressure measuring points, the pressure center is displayed, and bolt preload uniformity analysis is performed. This pressure cloud map is the assembly surface contact force cloud map.

Claims

1. A real-time measurement system for assembly pressure distribution under extreme working conditions, characterized in that, The real-time assembly pressure distribution measurement system under extreme working conditions is a flexible thin-film sensor integrating multiple pressure and temperature measuring points. Multiple pressure and temperature measuring points are arranged according to a certain pattern and assembly requirements within the working plane of the flexible thin-film sensor. The sensitive materials at both pressure and temperature measuring points are resistive materials, and their resistance changes with pressure or temperature. The pressure and temperature measuring points use the same signal line network. The voltage across the sensitive material or the current in the circuit is measured to calculate the material resistance. The pressure or temperature is calculated using a known pressure-resistance or temperature-resistance curve. The pressure and temperature measuring points are interchangeable. The signals collected by the flexible thin-film sensor are stored, uploaded, and displayed through a data acquisition unit. Based on the temperature data uploaded by the data acquisition unit, the pressure data is compensated, and the pressure data is calculated, displayed, and plotted as a time-domain curve of the pressure according to the pressure-resistance curve of the pressure measuring points. A cloud map of the contact force distribution on the assembly surface is plotted based on the location and pressure values ​​of all pressure measuring points. The signal line network includes m n-channel multiplexers; all pressure and temperature measuring points on the flexible thin-film sensor are divided into n measurement groups according to the wiring arrangement. Different measurement groups are controlled by a single set of n-channel multiplexers integrated in the data acquisition unit, where n = the number of measurement groups. The n-channel multiplexers control the connection and disconnection of each meridian in each measurement group with the analog interface. Time-division multiplexing or frequency-division multiplexing analog measurements are performed using m n-channel multiplexers. The same acquisition interface is used to measure the measuring points within multiple measurement groups, where m = the number of meridians in a single measurement group. The parallels within each measurement group are numbered from 0 to x according to their direction. Parallels with the same number in different measurement groups are connected to the same analog interface. The meridians in each measurement group are numbered from 0 to y. Parallels with the same number in different measurement groups are connected in parallel to the same analog output interface. The connection and disconnection of the measurement loops at each measuring point are controlled in a time-division manner using the n-channel multiplexers on the parallels, enabling sequential measurement of multiple measurement groups. The flexible thin-film sensor is a thin sheet with a thickness of 50µm to 200µm and uniform thickness. Its thickness direction consists of multiple layers of polymer material substrate, sensing material at measurement points, and ultra-thin wires within the flexible thin-film sensor. In the contact area between the flexible thin-film sensor and the component assembly surface, the multiple layers of polymer material substrate are sealed with weather-resistant sealant. Based on the specific shape and curvature of the component assembly surface, and following the principle of shortest path and path perpendicular to the curvature of the component assembly surface, all ultra-thin wires within the flexible thin-film sensor are encased in weather-resistant sealant. The weather-resistant sealant is applied in vertical strips following the curvature of the component assembly surface. The gaps between the strips serve as stress release areas and venting paths for the multiple layers of polymer material substrate. The vent is designed to be located at the outlet of the ultra-thin wires within the flexible thin-film sensor and is far from the low-temperature assembly components.

2. The real-time measurement system for assembly pressure distribution under extreme working conditions according to claim 1, characterized in that, The polymer substrate of the flexible thin-film sensor is PTFE or PEEK, and weather-resistant adhesive is used between the multiple polymer substrates to fix the sensing material of the measuring point and the ultra-thin wires inside the flexible thin-film sensor.

3. The real-time assembly pressure distribution measurement system under extreme working conditions according to claim 2, characterized in that, The compensation process involves compensating the pressure measurement point signals based on the temperature measurement point signals. During signal acquisition, the temperature measurement point signals are collected periodically. Based on the pre-calibrated position coordinates of all temperature measurement points and the real-time collected temperature values, the temperature distribution of the entire assembly surface is calculated and converted into coordinates. Similarly, the pre-calibrated pressure measurement point position coordinates are mapped to the temperature distribution to obtain the specific temperature value of each pressure measurement point. The temperatures of all pressure measurement points are marked. In the next round of pressure signal calculation, the pressure curve at the corresponding temperature is used to fit each pressure measurement point.

4. The real-time measurement system for assembly pressure distribution under extreme working conditions according to claim 3, characterized in that, The distribution of the pressure and temperature measuring points adopts a geometric topology, with at least 6 pressure and / or temperature measuring points evenly arranged around each bolt hole, and the distance between adjacent measuring points is less than or equal to 5 times the diameter of the measuring point.

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