A strain force detection device based on 3D printing and a measurement method thereof

Abstract

This invention provides a strain detection device and measurement method based on 3D printing, solving the problems of poor adaptability to complex environments and high cost of demodulation equipment in existing fiber optic grating sensing technology. The device includes a 3D-printed mold, a single-mode fiber (SMF), and an optical frequency domain reflectance (OFDR) system. The 3D-printed mold is generated by an automatic printing module according to the shape of the external container of the liquid medium. The single-mode fiber is simultaneously implanted during printing and adaptively fitted. The OFDR system is connected to the fiber to monitor phase shift changes and analyze strain distribution. The detection method mainly includes: placing the adaptive mold into the liquid medium, connecting the OFDR to monitor the strain signal, stress causing phase shift and interference patterns in the fiber, and determining the strain distribution through Fourier transform analysis. The technical solution of this invention can effectively improve the fit between the fiber and the detection environment and the detection accuracy, reduce costs, and is suitable for strain detection in liquid media.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic strain testing, and specifically relates to a strain testing device and its measurement method based on 3D printing. Background Technology

[0002] In industrial mechanical agitation, mechanical energy acts on piezoelectric minerals, stimulating the piezoelectric effect in the materials, generating electrons and forming a weak current. This process plays a crucial role in Earth's biogeochemical cycles and is even considered a potential form of endogenous energy in flowing aquatic environments, possessing significant scientific importance and application prospects. However, a key technological bottleneck in this field lies in the effective measurement of piezoelectric current. Whether at the laboratory simulation scale or during industrial reactor operation, directly and accurately quantifying the current intensity generated by the piezoelectric effect driven by water flow energy is extremely difficult.

[0003] Existing methods for detecting the piezoelectric properties of water flow mainly include: resistance strain gauge method, fiber optic grating sensing method, piezoelectric sensor method, capacitive sensing technology, and ultrasonic testing method. Fiber optic grating sensing technology has advantages such as corrosion resistance, electromagnetic interference resistance, and distributed measurement, and has rapidly emerged in the field of strain force detection in various liquid media in recent years. However, existing fiber optic testing methods for mechanical piezoelectric properties have poor adaptability and are difficult to adapt to the variable water flow environment in laboratories or in the field. The variable structure of experimental devices, dynamic changes in water flow, and the distribution of mineral particles, especially at low concentrations under natural conditions, all significantly interfere with the measurement process. Furthermore, signal stability and sensitivity are insufficient. Under the aforementioned complex and disturbed conditions, the electrical signals obtained by traditional methods are easily interfered with and have poor stability, making accurate detection difficult. Especially under low flow rates or low mineral concentrations, the signal-to-noise ratio is low, and the reliability of the measurement results is insufficient. Under conditions of pH, temperature and mechanical stirring force changes, the grating system is easily damaged, making it difficult to perform accurate and long-term detection. Existing processes cannot balance sensitivity and durability. In addition, high-precision detection currently mainly relies on equipment such as tunable lasers and spectrometers, which cost tens of thousands of US dollars, limiting the application in low-cost scenarios.

[0004] To address the aforementioned issues, there is an urgent need to develop a strain testing device and method that can adapt to complex environments, integrate seamlessly with the environment, and is stable, accurate, and cost-effective.

[0005] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The main objective of this invention is to overcome the deficiencies in the above-mentioned background technology and provide a strain detection device and its measurement method based on 3D printing, so as to realize the strain detection of liquid media that can adaptively conform to the shape of complex containers with high precision and high stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A strain detection device based on 3D printing, comprising:

[0009] 3D printed molds are adaptive molds generated by 3D printing based on the shape of the external container of a liquid medium.

[0010] Single-mode fiber (SMF) is simultaneously implanted into the 3D printing mold during the printing process;

[0011] An optical frequency domain reflector (OFDR) system is connected to the single-mode optical fiber;

[0012] The single-mode optical fiber is adaptively bonded and laid out in the 3D printed mold, and the optical frequency domain reflectance (OFDR) system analyzes the strain distribution by monitoring the phase shift change of the optical fiber.

[0013] Furthermore, the 3D printed mold uses photocurable acrylate combined with a micro-droplet spraying system to embed the single-mode optical fiber into the mold.

[0014] Furthermore, the composition of the photocurable acrylate by mass percentage includes: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

[0015] Furthermore, the core and cladding of the single-mode optical fiber are made of high-purity silica, the coating is made of polyurethane, and the sheath is made of polyethylene.

[0016] Furthermore, the device is suitable for liquid media with physical properties ranging from pH 4.0 to 9.5 and temperatures from -20°C to 80°C.

[0017] Furthermore, the monitoring and sensing range of the single-mode optical fiber is 2 to 2.895 meters.

[0018] Furthermore, the device can detect stress generated by laminar flow (<1 m / s) and turbulent flow (<0.5 m / s) of liquid media.

[0019] A strain detection method using the aforementioned device includes the following steps:

[0020] S1: Place the external container of the liquid medium being measured into the 3D printing module, and simultaneously implant the single-mode optical fiber into the printing mold to generate an adaptive mold that fits the shape of the liquid medium container.

[0021] S2: Place the adaptive mold from step S1 into the external container containing the liquid medium, and connect one end of the single-mode fiber to the optical frequency domain reflectometer system to monitor the strain signal within the sensing range.

[0022] S3: Applying stress to the optical fiber causes changes in its length and refractive index, resulting in a phase shift and interference patterns between light reflected from different positions along the fiber.

[0023] S4: Analyze the interference signal obtained in step S3 using Fourier transform, determine the phase shift, and then determine the strain distribution along the optical fiber.

[0024] Furthermore, in step S1, the 3D printing uses photocurable acrylate in conjunction with a microdroplet spraying system to embed the single-mode optical fiber into the mold. The photocurable acrylate comprises, by mass percentage: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

[0025] Furthermore, in step S4, the interference signal is processed by Fourier transform to extract the phase shift, and the strain distribution is derived based on the rate of change of the phase shift with the sensing distance, wherein the strain, as a function of position, is determined by the partial differential relationship between the phase shift and the distance.

[0026] The present invention has the following beneficial effects:

[0027] This invention addresses the bottlenecks of existing fiber Bragg grating (FBG) sensing technology, such as poor adaptability to complex environments, insufficient interface bonding strength, and high demodulation equipment costs. It provides a 3D-printed strain detection device and its measurement method, which can adapt to complex environments, is highly integrated with the detection scenario, and combines detection stability, accuracy, and cost-effectiveness. This invention employs an integrated design of customized structure and sensing collaboration: a 3D-printed mold, single-mode fiber (SMF), and optical frequency domain reflectance (OFDR) system are the core components. The 3D-printed module customizes an adaptive mold according to the shape of the external container of the liquid medium, while the single-mode fiber is simultaneously implanted into the mold. This achieves a high degree of fit between the fiber and the detection scenario from the structural source, breaking the limitation of traditional fixed fiber optic sensing deployments that are difficult to adapt to complex containers. Combined with the technical logic of connecting the fiber to the OFDR system to monitor strain signals, it can directly correlate strain distribution through changes in fiber phase shift, allowing the detection process to deeply match the medium morphology and stress transmission path. This improves detection accuracy and provides a structural foundation for stable sensing in complex environments.

[0028] Furthermore, by using photocurable acrylate in conjunction with a microdroplet spraying system to embed single-mode optical fibers into the mold, the synergistic effect of silane coupling agent (KH-550) and fumed silica (Aerosil R812) significantly improves the interfacial bonding force between the fluid container and the optical fiber. This invention effectively solves the traditional problem of easy fiber peeling under strain conditions, further consolidating the advantages of the basic solution in terms of structural fit and testing stability, and laying a key foundation for realizing the technological value.

[0029] The significant advantages of this invention lie in its breakthrough over the limitations of traditional fiber optic sensing technology: on the one hand, it provides a new research paradigm for long-term stable sensing under multi-physics coupling environments such as strain-temperature-chemical corrosion; on the other hand, the phase shift analysis method based on the OFDR system can achieve high-precision reconstruction of strain distribution along the fiber, providing a reliable experimental means for studying the spatial distribution characteristics of strain in liquid media and promoting the technological research progress in related fields.

[0030] In practical applications, the advantages of this invention become even more apparent: the adaptive mold formed by 3D printing can accurately fit the shape of the external container of the liquid medium, allowing the single-mode fiber to be deployed in a highly compatible manner with the detection scenario, significantly improving the accuracy of strain detection; its applicable range covers a wide physical property range of liquid media with pH 4.0-9.5 and temperature -20℃-80℃, and it can effectively detect stress generated under laminar flow <1m / s and turbulent flow <0.5m / s conditions, making it widely applicable to industrial stirring stress detection in environmental engineering, petrochemical and other fields. Meanwhile, the low-cost 3D printing process avoids the high investment required for traditional high-precision demodulation equipment (costing tens of thousands of US dollars), significantly lowering the application threshold; and the high-purity silica core and cladding, polyurethane coating, and polyethylene corrosion-resistant sheath design of the single-mode fiber further ensure long-term reliable detection of the device in multi-medium liquids, comprehensively enhancing its practical value and promotion potential.

[0031] This invention can accurately and stably measure strain in a variety of fluid media, and is especially suitable for flow conditions with a wide pH range and large shear force variations. In addition, the scene adaptability provided by 3D printing technology effectively meets the urgent need for strain detection in current water body and reactor engineering, and shows extremely high practical application value.

[0032] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a strain detection device according to an embodiment of the present invention.

[0034] Figure 2 This is a flowchart illustrating the overall process of strain detection method according to an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the measurement results according to an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the measurement results according to another embodiment of the present invention. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0038] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for fixing, coupling, or communication.

[0039] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] This invention aims to address the problems of insufficient adaptability to complex environments, high cost of demodulation equipment, and weak bonding strength between flexible substrates and optical fibers in existing fiber optic sensing technologies. It proposes a strain detection device and measurement method based on 3D printing. The device uses a 3D printing module to generate an adaptive mold that fits the shape of the external container of the liquid medium and simultaneously embeds a single-mode optical fiber. This is combined with an optical frequency domain reflectance (OFDR) system to monitor and analyze strain distribution. Thus, it improves detection accuracy through structural fit, reduces costs through 3D printing, adapts to a wide range of liquid media and flow conditions, and ensures long-term stable detection.

[0042] like Figure 1 As shown, this embodiment of the invention provides a strain detection device based on 3D printing, including a 3D printed mold 1, a single-mode fiber (SMF) 2, and an optical frequency domain reflectance (OFDR) system 3. The 3D printed mold 1 is an adaptive mold 3D printed according to the shape of an outer container 4 of a liquid medium. The single-mode fiber 2 is simultaneously implanted into the 3D printed mold 1 during the printing process. The optical frequency domain reflectance (OFDR) system 3 is connected to the single-mode fiber 2. The single-mode fiber 2 is adaptively fitted and arranged within the 3D printed mold, and the optical frequency domain reflectance (OFDR) system 3 analyzes the strain distribution by monitoring the phase shift changes of the fiber.

[0043] In some embodiments, the 3D printed mold uses photocurable acrylate combined with a microdroplet spraying system to embed single-mode optical fibers into the mold.

[0044] In some embodiments, the composition of the photocurable acrylate by mass percentage includes: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

[0045] In some embodiments, the core and cladding of the single-mode optical fiber are made of high-purity silica, the coating is made of polyurethane, and the sheath is made of polyethylene.

[0046] In some embodiments, the device is suitable for liquid media with physical properties ranging from pH 4.0 to 9.5 and temperatures from -20°C to 80°C.

[0047] In some embodiments, the monitoring and sensing range of the single-mode optical fiber is 2 to 2.895 meters.

[0048] In some embodiments, the device can detect stress generated by laminar flow (<1 m / s) and turbulent flow (<0.5 m / s) of liquid media.

[0049] See Figure 1 and Figure 2 The present invention also provides a strain detection method using the device, comprising the following steps:

[0050] Step S1: Place the outer container 4 of the liquid medium to be measured into the 3D printing module, and simultaneously implant the single-mode optical fiber 2 into the printing mold to print an adaptive mold (3D printing mold 1) that fits the shape of the outer container of the liquid medium; the adaptive mold can be cylindrical.

[0051] Step S2: Place the adaptive mold (3D printed mold 1) from step S1 into the external container 4 containing the liquid medium, and connect one end of the single-mode fiber 2 to the optical frequency domain reflectance OFDR system 3 to monitor the strain signal within the sensing range.

[0052] Step S3: Apply stress to the optical fiber to change its length and refractive index, resulting in a phase shift and interference patterns between the light reflected from different positions along the optical fiber.

[0053] Step S4: Analyze the interference signal obtained in step S3 using Fourier transform, determine the phase shift, and then determine the strain distribution along the optical fiber.

[0054] In some embodiments, the 3D printing in step S1 uses photocurable acrylate in conjunction with a microdroplet spraying system to embed single-mode optical fiber and mold. The composition of the photocurable acrylate by mass percentage includes: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

[0055] In some embodiments, in step S4, the interference signal is processed by Fourier transform to extract the phase shift, and the strain distribution is derived based on the rate of change of the phase shift with the sensing distance, wherein the strain as a function of position is determined by the partial differential relationship between the phase shift and the distance.

[0056] The strain detection device and measurement method proposed in this invention take a 3D-printed adaptive mold, a synchronously implanted single-mode optical fiber, and an optical frequency domain reflectance (OFDR) system as the core architecture. By accurately fitting the shape of the external container of the liquid medium through 3D printing, a high degree of fit between the optical fiber and the detection scene is achieved, solving the problem of poor adaptability of traditional fixed fiber optic sensing deployment. At the same time, the OFDR system is used to monitor the phase shift and interference signal under optical fiber stress, and the strain distribution is analyzed by Fourier transform, ensuring the reliability and accuracy of the detection principle. In a preferred embodiment, a photocurable acrylate (containing 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, combined with 3-5% TPO-L, 2-3% ITX and other initiators, as well as fumed silica and silane coupling agent KH-550) is used in conjunction with a microdroplet spraying system to significantly improve the interfacial bonding between the optical fiber and the mold, preventing fiber stripping under strain. The single-mode optical fiber adopts a high-purity silica core and corrosion-resistant sheath design, which is suitable for a wide media range of pH 4.0-9.5 and -20℃-80℃, as well as stress detection requirements for laminar flow <1m / s and turbulent flow <0.5m / s. Moreover, the 3D printing process avoids the high cost of traditional high-precision demodulation equipment, significantly improving the stability, applicability and promotion potential of the device.

[0057] The following further describes specific embodiments and experimental verifications of the present invention.

[0058] A strain detection device based on 3D printing includes: a 3D printed mold, a single-mode fiber (SMF), and an optical frequency domain reflectometer (OFDR) system. The measurement method involves placing the external container of the liquid medium to be measured into an automatic printing module, and simultaneously embedding the SMF into the printing mold to generate an adaptive mold that conforms to the external shape of the liquid medium. Then, one end of the SMF is connected to the OFDR system to monitor the strain signal within the sensing range. When stress is applied to the fiber, its length and refractive index change, resulting in a phase shift. Interference patterns are generated between the light reflected from different positions along the fiber. This device achieves adaptive bonding and placement of the fiber in key parts of a complex curved liquid container through a customized 3D printed structure (experimental results are shown in [link to experimental results]). Figure 3 , Figure 4 This invention can accurately and stably measure strain in a variety of fluid media, and is suitable for strain detection under flow conditions with a wide pH range and large shear force variations. The combination with 3D printing technology can adapt to various scenarios, providing a good solution for the urgent need for strain detection in water bodies and reactor engineering.

[0059] A strain detection method based on 3D printing technology includes the following steps:

[0060] Step S1: Place the outer container of the liquid medium to be measured into the automatic printing module, and simultaneously implant the single-mode fiber (SMF) into the printing mold to generate an adaptive mold that fits the external shape of the liquid medium.

[0061] In one embodiment, a 3D-printed strain detection device includes a 3D-printed mold, a single-mode fiber (SMF), and an optical frequency domain reflectance (OFDR) system.

[0062] In one embodiment, in step S1, 3D printing uses photocurable acrylate combined with a microdroplet spraying system to achieve the embedding of single-mode optical fiber and mold.

[0063] In one embodiment, the base material of the photocurable acrylate combined with the microdroplet spraying system is 50-70% polyurethane acrylate (low viscosity type) and 20-35% hydroxyethyl acrylate, 3-5% TPO-L (long-wave ultraviolet initiator, compatible with printing light source) and 2-3% ITX (sensitizer, to accelerate deep curing), 5-10% fumed silica (Aerosil R812, anti-sagging) and 1-3% silane coupling agent (KH-550, to enhance the bonding force with optical fiber).

[0064] In one embodiment, the core and cladding of the single-mode fiber (SMF) in step S1 are made of high-purity (>90%) silica, the coating is made of polyurethane, and the sheath is made of polyethylene.

[0065] Step S2: Place the mold from step S1 into the liquid medium and connect one end of the single-mode fiber to the optical frequency domain reflectometer (OFDR) system to monitor the strain signal within the sensing range.

[0066] In one embodiment, the physical properties of the liquid medium in step S2 are in the range of pH 4.0-9.5 and temperature -20℃-80℃.

[0067] In one embodiment, the liquid matrix in step S2 includes, but is not limited to, water-based liquids.

[0068] In one embodiment, the single-mode fiber in step S2 monitors strain signals within a range of 2 to 2.895 meters.

[0069] Step S3: Apply stress to the single-mode fiber in step S2. The length and refractive index of the fiber will change, resulting in a phase shift. Interference patterns will be generated between the light reflected from the fiber at different positions.

[0070] In one embodiment, the stress generated by laminar flow (<1 m / s) and turbulent flow (<0.5 m / s) of the liquid medium in step S3 can be detected.

[0071] Step S4: Analyze the interference signal obtained in step S3 using Fourier transform, determine the phase shift, and then determine the strain distribution along the optical fiber.

[0072] In one embodiment, the formula for plotting the strain σ(z) as a function of position in step S4 is as follows:

[0073]

[0074] Where z represents the distance along the sensing fiber. This indicates phase shift. By reconstructing the shape of the sensing fiber during OFDR testing, distance-strain data is converted into position-strain information, thereby obtaining the strain variation distribution.

[0075] Through technological innovation, this invention achieves low-cost, multi-scenario, and high-fit detection of strain gauges.

[0076] A photocurable acrylate is prepared using a base material consisting of 50-70% low-viscosity polyurethane acrylate and 20-35% hydroxyethyl acrylate, with 3-5% TPO-L (long-wave ultraviolet initiator, compatible with the printing light source) and 2-3% ITX (sensitizer, to accelerate deep curing), 5-10% fumed silica (Aerosil R812, to prevent sagging), and 1-3% silane coupling agent (KH-550, to enhance the bonding force with the optical fiber). This is combined with a microdroplet spraying system to embed single-mode optical fibers into the mold. The above-mentioned proportions offer advantages such as compatibility with the printing light source, accelerated deep curing, and enhanced bonding force between the mold and the optical fiber. The 3D printed mold and the selected materials can achieve strain testing in liquid media with physical properties ranging from pH 4.0 to 9.5 and temperatures from -20℃ to 80℃. Pre-acquisition of the external shape of the liquid medium and simultaneous optical fiber deployment via photopolymerization coupled with microdroplet spraying ensure a high degree of fit between the measuring mold and the liquid medium, guaranteeing the accuracy and precision of the measurement. Simultaneous monitoring by the OFDR system reduces data loss and ensures real-time reconstruction of phase shift to fiber strain. Designed around adaptive characteristics, from 3D material selection and optical fiber deployment to simultaneous monitoring, this system comprehensively enables low-cost, multi-scenario, and high-fit testing of strain gauges.

[0077] Experimental Example 1

[0078] A 300ml beaker containing 100ml of water at pH 7.0 and temperature 30℃ is placed into an automatic printing module. A base material of 60% polyurethane acrylate and 20% hydroxyethyl acrylate is combined with a photoinitiator of 5% TPO-L (long-wave ultraviolet initiator) and 3% ITX (sensitizer). Simultaneously, 10% fumed silica (Aerosil R812) and 2% silane coupling agent (KH-550) are sprayed to create a cylindrical mold with grooves and optical fibers (groove diameter: 1.5 mm, cylinder dimensions: height 90 mm, diameter 70 mm).

[0079] The mold was placed in a 300ml beaker containing 100ml of water and placed on a magnetic stirrer set to 200rpm to change the water flow rate. One end of a single-mode optical fiber was connected to an optical frequency domain reflectometer (OFDR) system to monitor the strain signal within a sensing range of 2 to 2.895 meters. The OFDR system analyzer has a spatial resolution of 2 millimeters. In OFDR, light waves emitted from a tunable laser source propagate through a single-mode optical fiber. When stress is applied to the fiber, its length and refractive index change, resulting in a phase shift. Interference patterns are generated between the light reflected from different positions along the fiber. By analyzing the interference signal using Fourier transform, the phase shift can be determined, and thus the strain distribution along the fiber can be determined. See [link to relevant documentation]. Figure 3 .

[0080] Experiment Example 2

[0081] A 200ml beaker containing 80ml of water at pH 4.5 and temperature 60℃ is placed into an automatic printing module. A base material of 70% polyurethane acrylate and 30% hydroxyethyl acrylate is combined with a photoinitiator of 5% TPO-L (long-wave ultraviolet initiator) and 2% ITX (sensitizer). Simultaneously, 8% fumed silica (Aerosil R812) and 3% silane coupling agent (KH-550) are sprayed to create a cylindrical mold with grooves and optical fibers (groove diameter: 1.4 mm, cylinder dimensions: height 60 mm, diameter 60 mm).

[0082] The mold was placed in a 200ml beaker containing 80ml of water and placed on a magnetic stirrer set to 600rpm to change the water flow rate. One end of a single-mode optical fiber was connected to an optical frequency domain reflectometer (OFDR) system to monitor the strain signal within a sensing range of 2 to 2.895 meters. The OFDR system used had a spatial resolution of 2 millimeters. In an OFDR, light waves emitted from a tunable laser source propagate through a single-mode optical fiber. When stress is applied to the fiber, its length and refractive index change, resulting in a phase shift. Interference patterns are generated between the light reflected from different positions along the fiber. By analyzing the interference signal using Fourier transform, the phase shift can be determined, and thus the strain distribution along the fiber can be determined. See [link to relevant documentation]. Figure 4 .

[0083] In summary, this invention proposes a strain detection device and its measurement method based on 3D printing. The core of the device consists of a 3D printed mold, a single-mode fiber (SMF), and an optical frequency domain reflectance (OFDR) system. The 3D printed mold generates an adaptive structure based on the shape of the external container of the liquid medium through an automatic printing module. The single-mode fiber is simultaneously implanted during the printing process to achieve a close fit with the detection scene. The measurement method involves placing the adaptive mold into the liquid medium and connecting the single-mode fiber to the OFDR system to monitor the strain signal within the sensing range. The strain distribution along the fiber is determined by analyzing the interference signal through Fourier transform, utilizing the phase shift and interference pattern generated by the changes in fiber length and refractive index under stress.

[0084] This invention specifically addresses the problems of existing fiber Bragg grating sensing technologies, such as insufficient cross-sensitivity and adaptability to complex environments, high demodulation system costs, and insufficient bonding strength between flexible substrates and optical fibers. The core of the invention is based on a 3D-printed adaptive mold combined with optical fiber strain detection. Its key features include the ability to adjust the fiber placement points according to the external shape of the liquid medium, enhancing bonding strength and adhesion, while maintaining low cost and wide applicability. This invention, combining 3D printing and optical fiber sensing, has significant value in the integrated innovation of sensing technologies. For example, the adaptive mold design improves the accuracy of strain distribution detection in complex environments, and the printing material formulation enhances interfacial bonding, solving the problem of unstable measurement under changing conditions. It provides a new method for strain detection under multi-physics coupling.

[0085] In practical applications, 3D printing technology reduces costs and is more suitable for low-cost scenarios compared to traditional high-precision demodulation equipment (costing tens of thousands of US dollars). It is applicable to a wide range of liquid media (pH 4.0-9.5, -20℃-80℃, laminar flow <1m / s, turbulent flow <0.5m / s), covering marine environmental engineering and petrochemical fields. The highly adaptable fit design improves detection accuracy, and the binder spraying enhances long-term reliability, solving the problem that traditional strain testing equipment cannot balance sensitivity and durability.

[0086] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A strain detection device based on 3D printing, characterized in that, include: The external container holds the liquid medium containing the strain to be measured; The 3D printed mold is an adaptive mold 3D printed according to the shape of the inner cavity of the outer container. The 3D printed mold adapts to the shape of the inner cavity of the outer container and fits into the outer container. Single-mode fiber (SMF) is simultaneously implanted into the 3D printing mold during the printing process, and its adaptive fit and layout within the 3D printing mold are adapted to the shape of the inner cavity of the external container. An optical frequency domain reflector (OFDR) system is connected to the single-mode optical fiber; The single-mode optical fiber, through its adaptation and bonding with the 3D printed mold and the external container, receives the deformation stress caused by the liquid medium acting on the external container and generates a phase shift. The optical frequency domain reflectance (OFDR) system analyzes the strain distribution by monitoring the phase shift change of the optical fiber.

2. The apparatus according to claim 1, characterized in that, The 3D printed mold uses photocurable acrylate combined with a microdroplet spraying system to embed single-mode optical fiber into the mold.

3. The apparatus according to claim 2, characterized in that, The composition of the photocurable acrylate by mass percentage includes: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

4. The apparatus according to claim 1, characterized in that, The core and cladding of the single-mode optical fiber are made of high-purity silica, the coating is made of polyurethane, and the sheath is made of polyethylene.

5. The apparatus according to claim 1, characterized in that, The device is suitable for liquid media with physical properties ranging from pH 4.0 to 9.5 and temperatures from -20°C to 80°C.

6. The apparatus according to claim 1, characterized in that, The monitoring and sensing range of the single-mode optical fiber is 2 to 2.895 meters.

7. The apparatus according to claim 1, characterized in that, The device can detect stress generated by laminar flow (<1 m / s) and turbulent flow (<0.5 m / s) of liquid media.

8. A strain force detection method using the apparatus according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Place the external container of the liquid medium being measured into the 3D printing module, and simultaneously implant the single-mode optical fiber into the printing mold to generate an adaptive mold that fits the shape of the liquid medium container. S2: Place the adaptive mold from step S1 into the external container containing the liquid medium, and connect one end of the single-mode fiber to the optical frequency domain reflectometer system to monitor the strain signal within the sensing range. S3: Applying stress to the optical fiber causes changes in its length and refractive index, resulting in a phase shift and interference patterns between light reflected from different positions along the fiber. S4: Analyze the interference signal obtained in step S3 using Fourier transform, determine the phase shift, and then determine the strain distribution along the optical fiber.

9. The method according to claim 8, characterized in that, In step S1, the 3D printing uses photocurable acrylate in conjunction with a microdroplet spraying system to embed single-mode optical fiber into the mold. The photocurable acrylate is composed of the following components by mass percentage: 50-70% polyurethane acrylate and 20-35% hydroxyethyl acrylate as the base material, 3-5% TPO-L and 2-3% ITX as the photoinitiator, and 5-10% fumed silica and 1-3% silane coupling agent as the additives.

10. The method according to claim 8, characterized in that, In step S4, the interference signal is processed by Fourier transform to extract the phase shift, and the strain distribution is derived based on the rate of change of the phase shift with the sensing distance. The strain, as a function of position, is determined by the partial differential relationship between the phase shift and the distance.

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