Infrared-image-based method for monitoring internal stress of fiber during laying

Abstract

The present invention relates to an infrared-image-based method for monitoring the internal stress of fiber during laying. The method comprises the following process steps: 1) using a digital image correlation technique and an infrared thermal imaging technique to respectively measure the strain and temperature at the same point of a fiber ribbon, and constructing a stress-temperature prediction model; 2) during a fiber laying operation process, observing the imaging performed by an infrared camera during a cooling process of the fiber ribbon, and recording the temperature of the fiber ribbon in an infrared image, so as to obtain motion-trajectory-based temperature distribution reconstruction of the fiber ribbon; and 3) using a temperature distribution reconstruction map of the fiber ribbon in step 2), and combining same with the stress-temperature prediction model constructed in step 1) to obtain a stress distribution, so as to realize real-time monitoring of the internal stress of fiber during laying. In the present invention, by using an infrared thermal image, the situation of a real-time stress distribution of a fiber ribbon can be obtained efficiently and accurately, and on the basis of the obtained real-time stress distribution of the fiber ribbon, a better fiber ribbon laying effect can be obtained.

Description

A method for monitoring internal stress in fiber layup based on infrared images [Technical Field]

[0001] This invention relates to a stress monitoring method, specifically a fiber laying internal stress monitoring method based on infrared images, belonging to the field of stress detection technology. [Background Technology]

[0002] During the fiber placement process, factors such as placement speed, placement pressure, placement temperature, and die temperature can affect the mechanical properties and even deform the finished product. Therefore, real-time monitoring of stress during fiber placement is of great significance.

[0003] Current technologies for stress monitoring of fiber optic cable laying mainly employ ultrasonic monitoring or strain gauge monitoring. However, ultrasonic monitoring suffers from poor stability and is difficult to achieve accurate measurements; while strain gauges acquire data at low frequencies, cannot respond in real time, and are limited by temperature tolerance and cost.

[0004] Therefore, in order to solve the above problems, it is indeed necessary to provide an innovative fiber laying internal stress monitoring method based on infrared images to overcome the defects in the prior art. [Summary of the Invention]

[0005] To address the aforementioned problems, the present invention aims to provide a non-contact, rapid information acquisition, and real-time monitoring method for monitoring internal stress in fiber laying based on infrared images, thereby achieving better fiber ribbon laying results.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for monitoring internal stress in fiber laying based on infrared images, comprising the following process steps:

[0007] 1) Using digital image correlation technology and infrared thermal imaging technology, the strain and temperature at the same point of the fiber ribbon are measured respectively, and a stress-temperature prediction model is constructed;

[0008] 2) During the fiber laying process, observe the imaging of the infrared camera during the cooling process of the fiber ribbon, record the temperature of the fiber ribbon in the infrared image, and obtain the temperature distribution reconstruction of the fiber ribbon based on the motion trajectory.

[0009] 3) Using the fiber ribbon temperature distribution reconstruction map from step 2), combined with the stress-temperature prediction model constructed in step 1), the stress distribution is calculated to achieve real-time monitoring of the internal stress of fiber laying.

[0010] The fiber placement internal stress monitoring method based on infrared images of the present invention is further comprising: step 1) specifically comprising:

[0011] 1-1), Lay out the fiber ribbon completely and conduct experiments on individual fiber ribbons;

[0012] 1-2), Spray a speckled pattern onto the fiber ribbon;

[0013] 1-3) Turn on the heat source to heat the fiber ribbon;

[0014] 1-4) During the cooling process of the fiber ribbon, digital image correlation technology was used to measure the speckle pattern t1, t2...t at a certain point on the surface of the fiber ribbon. n Strain components at time t: x-axis strain ε1, y-axis strain ε2, z-axis strain ε3, shear strain γ 12 γ 13 γ 23 ;

[0015] The mechanical parameters of fiber composite materials include: x-axis elastic modulus E1; y-axis elastic modulus E2; z-axis elastic modulus E3; and three in-plane shear moduli G. 12 G 13 G 23 ; Main Poisson's ratio v 12 v 13 v 23 ;

[0016] For orthotropic fiber composites, stress calculations using the generalized Hooke's law yield the following result: {ε}1=[S]{σ}1

[0017] Where {σ}1={σ1,σ2,σ3,τ} 23 ,τ 13 ,τ 12} T ; {ε}1={ε1,ε2,ε3,γ 23 ,γ 13 ,γ 12 ,} T ;

[0018] Using equivalent stress σ P The stress at that point is represented as follows:

[0019] Calculate the speckle patterns t1, t2, ..., t at a certain point using the above formula. n Stress at time points; simultaneously, using infrared thermal imaging technology to measure speckle patterns at the same point at times t1, t2, ... t3. n Temperature at any moment;

[0020] 1-5) Based on the above stress-temperature relationship, a stress-temperature prediction model is constructed using the stress and temperature of the speckle at the same point on the fiber ribbon.

[0021] The fiber laying internal stress monitoring method based on infrared images of the present invention is further described as follows: In step 1-1), a DIC lens is set directly above the fiber ribbon; an infrared camera is set directly to the left of the DIC lens; and a heat source is set directly to the right of the DIC lens; the heat source is specifically a halogen heat source lamp.

[0022] The fiber placement internal stress monitoring method based on infrared images of the present invention is further described in step 2):

[0023] 2-1) A laser heater is placed directly in front of the pressure roller to heat and soften the fiber ribbon; an infrared camera is placed directly behind the pressure roller to record the temperature of the fiber ribbon in real time.

[0024] 2-2) When laying the fiber ribbon, first turn on the laser heater and infrared camera; start the fiber laying machine, the laser heater heats the fiber ribbon to soften it, and drives the elastic pressure roller to lay the fiber ribbon tightly on the mold; during the cooling process after the fiber ribbon is laid, record the image from the rear infrared camera and record the temperature of a certain point on the fiber ribbon.

[0025] 2-3) Based on the motion trajectory of the fiber layer and the temperature of a certain point on the fiber ribbon, the temperature distribution of the fiber ribbon based on the motion trajectory is reconstructed.

[0026] The fiber placement internal stress monitoring method based on infrared images of the present invention further comprises: step 2-3) is:

[0027] During the operation of the fiber spreader, the forward speed of the pressure roller is V0, and the coordinates of a certain point on the fiber ribbon at time t1 are (x1, y1). According to the formula: x = Vt

[0028] Get the points t1, t2, ..., t of the fiber ribbon. n Time coordinates (x1, y1), (x2, y2)......(x n y n The location distribution of the fiber ribbon is determined by obtaining the temperature information of the point from the infrared camera, and then the temperature distribution of the fiber ribbon is reconstructed based on the motion trajectory.

[0029] The fiber placement internal stress monitoring method based on infrared images of the present invention further includes: step 3) specifically includes:

[0030] 3-1) Using the temperature distribution reconstruction map of the fiber ribbon based on the motion trajectory obtained in step 2), the temperature distribution of any point on the fiber ribbon during the fiber laying process is obtained;

[0031] 3-2) Using the stress-temperature prediction model constructed in step 1), we can obtain different stress distributions at different temperatures;

[0032] 3-3) The temperature distribution during the fiber laying process is obtained by reconstructing the temperature distribution map of the fiber ribbon. Combined with the constructed stress-temperature prediction model, the stress distribution of the fiber ribbon can be calculated, and the stress of the entire fiber ribbon can be monitored in real time through infrared images.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The fiber laying internal stress monitoring method based on infrared images of the present invention can efficiently and accurately obtain the real-time stress distribution of fiber ribbons, and achieve better fiber ribbon laying effect based on the obtained real-time stress distribution of fiber ribbons.

[0035] 2. The fiber laying internal stress monitoring method based on infrared images of the present invention uses digital image correlation technology to analyze the deformation of the object surface, which can measure the strain field with high precision. The infrared camera can display the temperature distribution of the object surface in real time and provide intuitive thermal images to obtain temperature data.

[0036] 3. The fiber laying internal stress monitoring method based on infrared images of the present invention does not require the installation of sensors on the fiber laying equipment, which reduces the complexity of the equipment and improves its reliability and durability. [Attached Image Description]

[0037] Figure 1 is a schematic diagram of the apparatus used in step 1) of the present invention to conduct an experiment on a single fiber ribbon.

[0038] Figure 2 is a diagram of the stress-temperature prediction model constructed under different stresses (σ) in step 1) of the present invention.

[0039] Figure 3 is a schematic diagram of the operation of the filament laying machine in step 2) of the present invention.

[0040] Figure 4 is a schematic diagram of the principle of reconstructing temperature distribution based on motion trajectory in step 2) of the present invention.

[0041] Figure 5 is an infrared image taken in a real experiment according to the present invention.

[0042] Figure 6 is a graph showing the relationship between temperature and stress in a real experiment of this invention.

Detailed Implementation Methods

[0043] Please refer to Figures 1 to 6 in the specification, which illustrate a fiber placement internal stress monitoring method based on infrared images according to the present invention, comprising the following process steps:

[0044] Step 1) Using digital image correlation (DIC) and infrared thermal imaging techniques, the strain and temperature of the speckle 4 at the same point on the fiber ribbon 5 are measured to construct a stress-temperature prediction model.

[0045] Specifically, step 1) constructs a stress-temperature prediction model in the following manner.

[0046] 1-1) The fiber ribbon 5 is laid out completely, and the experiment is conducted on this individual fiber ribbon 5. Before the experiment, a DIC lens 2 is placed directly above the fiber ribbon 5. An infrared camera 1 is placed directly to the left of the DIC lens 2. A heat source 3 is placed directly to the right of the DIC lens 2, as shown in Figure 1 of the specification. In this embodiment, the heat source 3 is specifically a halogen heat source lamp.

[0047] 1-2), Spray the speckled pattern 4 onto the fiber ribbon 5.

[0048] 1-3), turn on the heat source 3 to heat the fiber ribbon 5.

[0049] 1-4), during the cooling process of the fiber ribbon, digital image correlation technology was used to measure the speckle pattern 4 at a certain point on the surface of the fiber ribbon at t1, t2...t. n Strain components at time t: x-axis strain ε1, y-axis strain ε2, z-axis strain ε3, shear strain γ 12 γ 13 γ 23 .

[0050] The mechanical parameters of fiber composite materials include: x-axis elastic modulus E1; y-axis elastic modulus E2; z-axis elastic modulus E3; and three in-plane shear moduli G. 12 G 13 G 23 ; Main Poisson's ratio v 12 v 13 v 23 These mechanical parameters can be found in material data handbooks.

[0051] For orthotropic fiber composites, stress calculations using the generalized Hooke's law yield the following result: {ε}1=[S]{σ}1

[0052] Among them, {σ}1={σ1,σ2,σ3,τ 23 ,τ 13 ,τ 12} T ;

[0053] Using equivalent stress σ P The stress at that point is represented as follows:

[0054] The above formula is used to calculate the speckle pattern 4 at a certain point at t1, t2, ..., t3. n Stress at time t1; simultaneously, using infrared thermal imaging technology to measure speckle 4 at the same point at t1, t2...tn The temperature of a moment.

[0055] 1-5) According to the thermoelastic mechanics theory, there is a relationship between stress and temperature; therefore, using the stress and temperature of the same spot 4 at the same point of the fiber ribbon 5, a stress-temperature prediction model is constructed, as shown in Figure 2 of the instruction manual.

[0056] Step 2) During the actual fiber laying process, observe the imaging of the infrared camera 1 during the cooling process of the fiber ribbon 5, record the temperature of the fiber ribbon 5 in the infrared image, and obtain the temperature distribution reconstruction of the fiber ribbon 5 based on the motion trajectory.

[0057] Specifically, step 2) reconstructs the temperature distribution of the fiber ribbon in the following manner.

[0058] 2-1) The laser heater 7 is positioned directly in front of the pressure roller 6 of the fiber layup machine to heat and soften the fiber ribbon 5. The infrared camera 1 is positioned directly behind the pressure roller 6 to record the temperature of the fiber ribbon 5 in real time, as shown in Figure 3 of the instruction manual.

[0059] 2-2) When laying the fiber ribbon 5, first turn on the laser heater 7 and the infrared camera 1; start the fiber laying machine, and the laser heater 7 heats the fiber ribbon 5 until it softens, driving the elastic pressure roller 6 to tightly lay the fiber ribbon 5 on the mold. During the cooling process after the fiber ribbon 5 is laid, record the image from the rear infrared camera 1 and record the temperature of a certain point 8 of the fiber ribbon 5.

[0060] 2-3) Based on the motion trajectory of the fiber placement machine and the temperature of a certain point 8 on the fiber ribbon 5, the temperature distribution reconstruction of the fiber ribbon 5 based on the motion trajectory is obtained. Specifically, during the operation of the fiber placement machine, the forward speed of the pressure roller 6 is V0, and the coordinates of a certain point 8 on the fiber ribbon 5 at time t1 are (x1, y1). According to the formula: x = Vt

[0061] We obtain the coordinates of point 8 on fiber ribbon 5 at t1, t2, ..., t3. n Time coordinates (x1, y1), (x2, y2)......(x n y n The location distribution of the fiber ribbon is determined by obtaining the temperature information of the point from the infrared camera 1, and then reconstructing the temperature distribution of the fiber ribbon based on its motion trajectory.

[0062] Step 3) Using the temperature distribution reconstruction map of the fiber ribbon from Step 2), combined with the stress-temperature prediction model constructed in Step 1), the stress distribution of the fiber ribbon is calculated, thereby realizing real-time monitoring of the stress of the entire fiber ribbon through infrared images.

[0063] Step 3) is implemented in the following manner:

[0064] 3-1) Using the temperature distribution reconstruction map of the fiber ribbon based on the motion trajectory obtained in step 2), the temperature distribution of any point on the fiber ribbon during the fiber laying process is obtained;

[0065] 3-2) Using the stress-temperature prediction model constructed in step 1), we can obtain different stress distributions at different temperatures;

[0066] 3-3) The temperature distribution during the fiber laying process is obtained by reconstructing the temperature distribution map of the fiber ribbon. Combined with the constructed stress-temperature prediction model, the stress distribution of the fiber ribbon can be calculated, and the stress of the entire fiber ribbon can be monitored in real time through infrared images.

[0067] Figure 5 shows an infrared image taken by an infrared camera during the fiber ribbon cooling process. The temperature of 30 points along the ribbon direction in the middle of the infrared image is recorded. The temperature value of each point is shown as the solid line in Figure 6. The calculated stress is shown as the dashed line in Figure 6.

[0068] The fiber layup internal stress monitoring method based on infrared images of this invention uses DIC technology to analyze the deformation of the object surface, which can measure the strain field with high precision. The infrared camera can display the temperature distribution of the object surface in real time, providing intuitive thermal images to obtain temperature data. Moreover, this invention eliminates the need to lay sensors on the fiber layup equipment, reducing the complexity of the equipment and improving its reliability and durability. Experiments show that the stress-temperature prediction model designed in this invention basically matches the actual data.

[0069] The above-described specific embodiments are merely preferred embodiments of this invention and are not intended to limit this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for monitoring internal stress in fiber laying based on infrared images, characterized in that: The process includes the following steps: 1) Using digital image correlation technology and infrared thermal imaging technology, the strain and temperature at the same point of the fiber ribbon are measured respectively, and a stress-temperature prediction model is constructed; 2) During the fiber laying process, observe the imaging of the infrared camera during the cooling process of the fiber ribbon, record the temperature of the fiber ribbon in the infrared image, and obtain the temperature distribution reconstruction of the fiber ribbon based on the motion trajectory. 3) Using the fiber ribbon temperature distribution reconstruction map from step 2), combined with the stress-temperature prediction model constructed in step 1), the stress distribution is calculated to achieve real-time monitoring of the internal stress of fiber laying.

2. The fiber laying internal stress monitoring method based on infrared images as described in claim 1, characterized in that: Step 1) specifically refers to: 1-1), Lay out the fiber ribbon completely and conduct experiments on individual fiber ribbons; 1-2), Spray a speckled pattern onto the fiber ribbon; 1-3) Turn on the heat source to heat the fiber ribbon; 1-4) During the cooling process of the fiber ribbon, digital image correlation technology was used to measure the speckle pattern t1, t2...t at a certain point on the surface of the fiber ribbon. n Strain components at time t: x-axis strain ε1, y-axis strain ε2, z-axis strain ε3, shear strain γ 12 γ 13 γ 23 ; The mechanical parameters of fiber composite materials include: x-axis elastic modulus E1; y-axis elastic modulus E2; z-axis elastic modulus E3; and three in-plane shear moduli G. 12 G 13 G 23 ; Main Poisson's ratio v 12 v 13 v 23 ; For orthotropic fiber composites, stress calculations using the generalized Hooke's law show that: {ε}1=[S]{σ}1 in {σ}1={σ1,σ2,σ3,τ 23 ,t 13 ,t 12 } T ; {e}1={e1,e2,e3,c 23 ,c 13 ,c 12 ,} T ; Using equivalent stress σ P The stress at that point is represented as follows: Calculate the speckle patterns t1, t2, ..., t at a certain point using the above formula. n Stress at time points; simultaneously, using infrared thermal imaging technology to measure speckle patterns at the same point at times t1, t2, ... t3. n Temperature at any moment; 1-5) Based on the above stress-temperature relationship, a stress-temperature prediction model is constructed using the stress and temperature of the speckle at the same point on the fiber ribbon.

3. The fiber laying internal stress monitoring method based on infrared images as described in claim 1, characterized in that: In step 1-1), a DIC lens is placed directly above the fiber ribbon; an infrared camera is placed directly to the left of the DIC lens; and a heat source is placed directly to the right of the DIC lens; the heat source is specifically a halogen heat source lamp.

4. The fiber laying internal stress monitoring method based on infrared images as described in claim 1, characterized in that: Step 2) specifically refers to: 2-1) A laser heater is placed directly in front of the pressure roller to heat and soften the fiber ribbon; an infrared camera is placed directly behind the pressure roller to record the temperature of the fiber ribbon in real time. 2-2) When laying the fiber ribbon, first turn on the laser heater and infrared camera switches; The fiber layup machine is started, and the laser heater heats the fiber ribbon to soften it, driving the elastic pressure roller to lay the fiber ribbon tightly on the mold; during the cooling process after the fiber ribbon is laid, the image from the rear infrared camera is recorded to record the temperature of a certain point on the fiber ribbon; 2-3) Based on the motion trajectory of the fiber layer and the temperature of a certain point on the fiber ribbon, the temperature distribution of the fiber ribbon based on the motion trajectory is reconstructed.

5. The fiber laying internal stress monitoring method based on infrared images as described in claim 4, characterized in that: Steps 2-3) are as follows: During the operation of the fiber spreader, the forward speed of the pressure roller is V0, and the coordinates of a certain point on the fiber ribbon at time t1 are (x1, y1). According to the formula: x = Vt Get the points t1, t2, ..., t of the fiber ribbon. n Time coordinates (x1, y1), (x2, y2)......(x n y n The location distribution of the fiber ribbon is determined by obtaining the temperature information of the point from the infrared camera, and then the temperature distribution of the fiber ribbon is reconstructed based on the motion trajectory.

6. The fiber laying internal stress monitoring method based on infrared images as described in claim 1, characterized in that: Step 3) specifically refers to: 3-1), using the temperature distribution reconstruction map of the fiber ribbon based on the motion trajectory obtained in step 2), The temperature distribution at any point on the fiber ribbon during the fiber laying process is obtained; 3-2) Using the stress-temperature prediction model constructed in step 1), we can obtain different stress distributions at different temperatures; 3-3) The temperature distribution during the fiber laying process is obtained by reconstructing the temperature distribution map of the fiber ribbon. Combined with the constructed stress-temperature prediction model, the stress distribution of the fiber ribbon can be calculated, and the stress of the entire fiber ribbon can be monitored in real time through infrared images.

Images