CN103386753B

CN103386753B - The application of capacitance sensor in Polymer moulding

Info

Publication number: CN103386753B
Application number: CN201310326061.2A
Authority: CN
Inventors: 李海梅; 江玉龙; 陈金涛; 罗传东; 宋刚; 刘保臣; 王波; 杨永良; 张亚飞; 李瑞波
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2013-07-30
Filing date: 2013-07-30
Publication date: 2016-01-20
Anticipated expiration: 2033-07-30
Also published as: CN103386753A

Abstract

The invention relates to an application of a capacitive sensor in polymer molding, which comprises the following steps: fixing the capacitive sensor on the cavity wall or the inner wall of a die head, using a signal generator to generate an initial excitation signal for the capacitive sensor, and performing polymer Forming and processing, and detecting the output signal of the capacitance sensor, collecting the voltage signal at the output terminal of the lock-in amplifier, and converting the collected voltage signal into shear stress. By adopting the above application steps, not only the continuous and multi-period online measurement of shear stress can be realized during the polymer molding process, but also the specific value of each shear stress component can be obtained directly, thus effectively completing the measurement of the shear stress. The collection, analysis and calculation process of shear stress information provides an effective analysis means and method for stress research and molding quality control in plastic molding processing.

Description

Application of capacitive sensor in polymer molding process

技术领域technical field

本发明涉及一种电容传感器在聚合物成型加工中的应用。The invention relates to the application of a capacitance sensor in polymer molding processing.

背景技术Background technique

在成型加工中，由于成型参数控制不合适或者模具/产品设计问题等原因，注塑制品中往往或多或少会存在残余应力，从而显著影响注塑制品的外观形状和光学、力学、声学等物理性能，同时这也对注塑制品的使用寿命起着决定性的影响。现有的研究表明：注射成型过程引起的制品残余应力可分为流动残余应力和热残余应力，二者的关系至今仍没有清晰明确的结果；其中热残余应力可通过退火进行有效消除，但流动残余应力目前没有明确的处理方法。因此，在注塑成型过程中，对残余应力的量化便成了实现高品质注塑成型的要求。In the molding process, due to improper control of molding parameters or mold/product design problems, there are often residual stresses in injection molded products, which significantly affects the appearance, shape and optical, mechanical, acoustic and other physical properties of injection molded products. , At the same time, it also has a decisive impact on the service life of injection molded products. Existing studies have shown that the product residual stress caused by the injection molding process can be divided into flow residual stress and thermal residual stress. There is currently no clear treatment method for residual stress. Therefore, in the injection molding process, the quantification of residual stress has become a requirement to achieve high-quality injection molding.

目前，对于残余应力的测量主要停留在离线测量上。按照对注塑制品有无破坏性，离线测量大体可分为有损测量和无损测量两种。有损测量主要包含剥层法、钻孔法以及化学腐蚀法等方法，这几种方法方便易行，但带来了外加机械力，从而改变了成型过程中的结构状态。无损测量则主要包含了X射线法和双折射法，X射线法穿透深度小，主要用于测量表层残余应力，而双折射法主要用于测试透明制品的残余应力。并且上述方法都是离线测量方法，其测量结果只能说明脱模后注塑制品的最终应力情况，而并不能说明注塑制品在成型加工中的应力分布情况。At present, the measurement of residual stress mainly stays in offline measurement. According to whether it is destructive to injection molded products, offline measurement can be roughly divided into two types: destructive measurement and nondestructive measurement. Destructive measurement mainly includes methods such as peeling method, drilling method and chemical etching method. These methods are convenient and easy to implement, but they bring external mechanical force, thus changing the structural state during the forming process. Non-destructive measurement mainly includes X-ray method and birefringence method. The X-ray method has a small penetration depth and is mainly used to measure the residual stress of the surface layer, while the birefringence method is mainly used to test the residual stress of transparent products. Moreover, the above methods are all off-line measurement methods, and the measurement results can only explain the final stress of the injection molded product after demoulding, but cannot explain the stress distribution of the injection molded product during the molding process.

在公开号为CN102853951A的中国专利文献中，提供了一种高分子注塑加工残余应力的检测方法，它是将经过改性处理的导电纤维跟高分子材料一起注塑加工，同时在导电纤维的两端设置电极引出线，然后对注塑品进行热处理，通过测量热处理前后导电纤维的电阻，通过导电纤维电阻的变化转换出注塑制品相应的应力，从而能够准确测量注塑制品在加工过程中不同部位形成的残余应力。但是该方法必须在成型加工材料中加入导电纤维来测得注塑制品的残余应力，还不能提供一种可以直接在注塑成型过程中不通过加入其它辅助材料而直接测量残余应力的方法或装置，且该测量方法也是在制品制备后实现，属于离线测量方法。现有专利US2009/0249885A1，其主要考虑应力应变关系，仅仅应用于成型加工完成后的塑料制品，没有涉及到聚合物成型加工过程的在线测量，且其只能够得到应力之间的差值，而无法得到应力分量的具体量值。In the Chinese patent literature with the publication number CN102853951A, a detection method for the residual stress of polymer injection molding is provided. Set the electrode lead-out line, and then heat-treat the injection molded product. By measuring the resistance of the conductive fiber before and after heat treatment, the corresponding stress of the injection molded product can be converted through the change of the resistance of the conductive fiber, so that the residual formed in different parts of the injection molded product can be accurately measured. stress. However, this method must add conductive fibers to the molding processing material to measure the residual stress of the injection molded product, and cannot provide a method or device that can directly measure the residual stress without adding other auxiliary materials during the injection molding process, and This measurement method is also realized after the product is prepared, and belongs to the off-line measurement method. The existing patent US2009/0249885A1 mainly considers the relationship between stress and strain, and is only applied to plastic products after molding processing. It does not involve online measurement of the polymer molding process, and it can only obtain the difference between stresses. Specific magnitudes of the stress components cannot be obtained.

发明内容Contents of the invention

为克服以上现有技术的不足，本发明要解决的技术问题是提供一种电容传感器在聚合物成型加工中的应用，利用该电容传感器，不仅能在聚合物成型加工过程中实现对应力的连续、多周期的在线实时测量，而且还能够进一步直接得到测量位置处相关应力分量的具体量值。In order to overcome the above deficiencies in the prior art, the technical problem to be solved by the present invention is to provide an application of a capacitive sensor in the polymer molding process, using the capacitive sensor, not only can realize the continuous stress response in the polymer molding process , multi-period online real-time measurement, and can further directly obtain the specific value of the relevant stress component at the measurement position.

本发明的技术方案是：Technical scheme of the present invention is:

一种电容传感器在聚合物成型加工中的应用，包括以下步骤：An application of a capacitive sensor in polymer molding processing, comprising the following steps:

1）将电容传感器固定在聚合物成型模具型腔内或口模的内壁上，其中电容传感器包括绝缘基材、附着于绝缘基材上的导电电极以及分别与导电电极连接的第一电极线和第二电极线；1) Fix the capacitive sensor in the cavity of the polymer molding mold or on the inner wall of the die, wherein the capacitive sensor includes an insulating substrate, a conductive electrode attached to the insulating substrate, and a first electrode wire connected to the conductive electrode and the second electrode wire;

2）用信号发生器产生对所述电容传感器的初始激励信号，同时该信号传递至锁相放大器的参考输入端；2) A signal generator is used to generate an initial excitation signal for the capacitive sensor, and the signal is transmitted to the reference input terminal of the lock-in amplifier;

3）进行聚合物成型加工，聚合物熔体开始与电容传感器接触，电容传感器的电容及输出信号发生改变，对电容传感器的输出信号进行去噪处理，并且将去噪后的信号传递至锁相放大器的信号输入端；3) Carry out polymer molding processing, the polymer melt starts to contact with the capacitive sensor, the capacitance and output signal of the capacitive sensor change, the output signal of the capacitive sensor is denoised, and the denoised signal is transmitted to the phase lock The signal input terminal of the amplifier;

4）用信号记录仪采集锁相放大器输出端的电压信号；4) Use a signal recorder to collect the voltage signal at the output of the lock-in amplifier;

5）将采集到的电压信号转换成剪切应力，从而实现了在聚合物成型加工过程中对剪切应力的在线测量。5) The collected voltage signal is converted into shear stress, so as to realize the online measurement of shear stress during the polymer molding process.

上述电容传感器在聚合物成型加工中的应用，其中步骤5）中将电压信号转换成剪切应力的具体步骤为：In the application of the above-mentioned capacitive sensor in polymer molding processing, the specific steps of converting the voltage signal into shear stress in step 5) are:

5.1）对介电常数为ε的初始各向同性材料，得出电容传感器的电容为：5.1) For an initially isotropic material with a dielectric constant ε, the capacitance of a capacitive sensor is obtained as:

C_θ=C_O(ε+ε_S)C _θ =C _O (ε+ε _S )

5.2）当原始各向同性材料遭受变形时，上述介电常数ε采用一个二阶张量表示为5.2) When the original isotropic material is subjected to deformation, the above dielectric constant ε is expressed as a second-order tensor as

$ϵ ϵ = = [\begin{matrix} ϵ ϵ + + {k k}_{11} {s the s}_{xx xxx} + + {k k}_{22} {s the s}_{ll ll} & ϵ ϵ + + {k k}_{11} {s the s}_{xy xy} & ϵ ϵ + + {k k}_{11} {s the s}_{xz xz} \\ ϵ ϵ + + {k k}_{11} {s the s}_{xy xy} & ϵ ϵ + + {k k}_{11} {s the s}_{yy yy} + + {k k}_{22} {s the s}_{ll ll} & ϵ ϵ + + {k k}_{11} {s the s}_{yz yz} \\ ϵ ϵ + + {k k}_{11} {s the s}_{xz xz} & ϵ ϵ + + {k k}_{11} {s the s}_{yz yz} & ϵ ϵ + + {k k}_{11} {s the s}_{zz zz} + + {k k}_{22} {s the s}_{ll ll} \end{matrix}]$

5.3）取应力作为变量，并在小变形状态下，电容传感器的电容进一步表示为5.3) Taking the stress as a variable, and in the state of small deformation, the capacitance of the capacitive sensor is further expressed as

${C C}_{θ θ} = = {C C}_{00} (\begin{matrix} ϵ ϵ + + \frac{{λ λ}_{11} (({σ σ}_{xx xxx} {cos cos}^{22} θ θ + + {σ σ}_{yy yy} {sin sin}^{22} θ θ + + 22 {σ σ}_{xy xy} sin sin θ θ cos cos θ θ + + {σ σ}_{zz zz})) + + 22 {λ λ}_{22} {σ σ}_{ll ll}}{22} \\ + + \frac{{λ λ}_{11}^{22} [[(({σ σ}_{xx xxx} {σ σ}_{zz zz} - - {σ σ}_{xz xz}^{22})) {cos cos}^{22} θ θ + + (({σ σ}_{yy yy} {σ σ}_{zz zz} - - {σ σ}_{yz yz}^{22})) {sin sin}^{22} θ θ + + 22 (({σ σ}_{xy xy} {σ σ}_{zz zz} - - {σ σ}_{xz xz} {σ σ}_{yz yz})) cos cos θ θ sin sin θ θ]]}{22 ϵ ϵ} \\ + + \frac{{λ λ}_{11} {λ λ}_{22} {σ σ}_{ll ll} (({σ σ}_{xx xxx} {cos cos}^{22} θ θ + + {σ σ}_{yy yy} {sin sin}^{22} θ θ + + {22 σ σ}_{xy xy} cos cos θ θ sin sin θ θ + + {σ σ}_{zz zz})) + + {λ λ}_{22}^{22} {σ σ}_{ll ll}^{22}}{22 ϵ ϵ} + + {ϵ ϵ}_{s the s} \end{matrix})$

5.4）依据电容传感器的电容变化与输出信号变化之间的关系5.4) According to the relationship between the capacitance change of the capacitive sensor and the output signal change

$\frac{Δ Δ {V V}_{θ θ}}{{V V}_{00}} = = - - \frac{{C C}_{θ θ} - - {C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{s the s}))}{{C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{s the s}))}$

并结合步骤5.3），得到采集的电压信号与剪切应力之间的转换关系。Combined with step 5.3), the conversion relationship between the collected voltage signal and the shear stress is obtained.

上述电容传感器在聚合物成型加工中的应用，其中导电电极包括第一电极和第二电极，第一电极和第二电极位于同一平面内，且第一电极与第一电极线连接，第二电极与第二电极线连接，第一电极和第二电极分别包括多个均匀分散排布的电极条，并且第一电极的电极条与第二电极的电极条相互交错排列且互不连通。The application of the above capacitive sensor in polymer molding processing, wherein the conductive electrode includes a first electrode and a second electrode, the first electrode and the second electrode are located in the same plane, and the first electrode is connected to the first electrode line, and the second electrode Connected with the second electrode line, the first electrode and the second electrode respectively include a plurality of uniformly distributed electrode strips, and the electrode strips of the first electrode and the electrode strips of the second electrode are arranged alternately and are not connected to each other.

上述电容传感器在聚合物成型加工中的应用，其中在聚合物成型过程的在线测量中，采用电容传感器的数目与拟计算的应力变量数目对应，当电容传感器的数目为一个时，在测量时分别以不同的角度固定安装并多次测量，当电容传感器的数目为两个以上时，每个电容传感器分别以不同的角度固定安装。The application of the above-mentioned capacitive sensor in polymer molding process, wherein in the online measurement of the polymer molding process, the number of capacitive sensors used corresponds to the number of stress variables to be calculated. When the number of capacitive sensors is one, when measuring, respectively Fix and install at different angles and perform multiple measurements. When the number of capacitive sensors is more than two, each capacitive sensor is fixed and installed at different angles.

上述电容传感器在聚合物成型加工中的应用，其中在聚合物成型过程中，聚合物熔体与电容传感器接触后，输出的实时电压信号与成型加工生产过程对应。The application of the capacitive sensor in polymer molding process, wherein in the polymer molding process, after the polymer melt contacts with the capacitive sensor, the output real-time voltage signal corresponds to the molding process production process.

上述电容传感器在聚合物成型加工中的应用，当沿着电容传感器所在平面与传感器接触的聚合物熔体，进行剪切应力的测量分析量化时，对应电容传感器的数目为三个，每个电容传感器分别以不同的角度固定安装，且每个电容传感器的安装角度均位于0°-90°内。For the application of the above capacitive sensor in polymer molding, when the shear stress is measured, analyzed and quantified along the polymer melt in contact with the sensor along the plane where the capacitive sensor is located, the number of corresponding capacitive sensors is three, and each capacitive sensor The sensors are fixedly installed at different angles, and the installation angle of each capacitive sensor is within 0°-90°.

上述电容传感器在聚合物成型加工中的应用，当垂直于电容传感器所在平面与传感器接触的聚合物熔体，进行应力的测量分析量化时，对应电容传感器的数目为两个，每个电容传感器分别以不同的角度固定安装，且每个电容传感器的安装角度均位于0°-90°内。For the application of the above capacitive sensor in polymer molding processing, when the polymer melt in contact with the sensor is perpendicular to the plane where the capacitive sensor is located, when the stress is measured, analyzed and quantified, the number of corresponding capacitive sensors is two, and each capacitive sensor is respectively Fixed installation at different angles, and the installation angle of each capacitive sensor is within 0°-90°.

上述电容传感器在聚合物成型加工中的应用，其中第一电极的电极条与第二电极的电极条相互排列形成的平面形状为矩形或菱形，用于对具有平面结构的聚合物成型制品进行测量。The application of the capacitive sensor above in polymer molding processing, wherein the electrode strips of the first electrode and the electrode strips of the second electrode are arranged to form a plane shape that is rectangular or rhombus, and is used for measuring polymer molded products with a planar structure .

上述电容传感器在聚合物成型加工中的应用，其中第一电极的电极条与第二电极的电极条相互排列形成的平面形状为圆形、椭圆形或弧形，用于对采用中间进浇方式或者含有圆弧或圆形结构的聚合物成型制品进行测量。The application of the above capacitive sensor in polymer molding processing, wherein the electrode strips of the first electrode and the electrode strips of the second electrode are arranged to form a plane shape that is circular, elliptical or arc-shaped, and is used for using the intermediate pouring method Or polymer shaped articles containing arcs or circular structures are measured.

上述电容传感器在聚合物成型加工中的应用，其中绝缘基材为薄膜状或片状，绝缘基材的材料为聚酰胺，厚度为5-25μm，导电电极的材料为银、铜、金、铝、锌或铂，导电电极的厚度为20-35μm，并且导电电极通过粘合的方式附着于绝缘基材上，且剥离强度大于1N/mm；电极条的宽度与相互交错排列的电极条之间的间距的比例为1:1至1:3，电极条的长度与相互交错排列的电极条之间的间距的比例大于10:1。The application of the above capacitive sensor in polymer molding processing, wherein the insulating substrate is film or sheet, the material of the insulating substrate is polyamide, the thickness is 5-25μm, and the material of the conductive electrode is silver, copper, gold, aluminum , zinc or platinum, the thickness of the conductive electrode is 20-35μm, and the conductive electrode is attached to the insulating substrate by bonding, and the peel strength is greater than 1N/mm; The ratio of the distance between the electrode strips is 1:1 to 1:3, and the ratio of the length of the electrode strips to the distance between the electrode strips arranged in a staggered manner is greater than 10:1.

本发明的有益效果是：通过提供了上述电容传感器在聚合物成型加工中的应用方法，不仅在聚合物成型加工过程中实现了对应力的连续、多周期的在线测量，而且还能够进一步直接得到各个应力分量的具体量值，从而有效完成了对应力信息的采集、分析和计算过程，便于成型过程的质量控制，及成型加工过程中应力、成型加工机理方面的应用、研究。The beneficial effects of the present invention are: by providing the application method of the capacitive sensor in the polymer molding process, not only the continuous and multi-period online measurement of the stress is realized in the polymer molding process, but also can be further directly obtained The specific value of each stress component can effectively complete the collection, analysis and calculation process of stress information, facilitate the quality control of the forming process, and the application and research of stress and forming processing mechanism in the forming process.

附图说明Description of drawings

下面结合附图对本发明的具体实施方式作进一步详细的说明。The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

图1是电容传感器的安装结构示意图；Figure 1 is a schematic diagram of the installation structure of a capacitive sensor;

图2是常规注塑成型下的传感器安装及测试原理示意图；Figure 2 is a schematic diagram of sensor installation and testing principles under conventional injection molding;

图3是气辅成型下的传感器安装及测试原理示意图；Figure 3 is a schematic diagram of sensor installation and testing principles under gas-assisted molding;

图4是水辅成型（或夹芯注射成型）下的传感器安装及测试原理示意图；Figure 4 is a schematic diagram of sensor installation and testing principles under water-assisted molding (or sandwich injection molding);

图5是测量位置处应力单元示意图；Fig. 5 is a schematic diagram of the stress unit at the measurement position;

图6是电容传感器的矩形平面形状结构示意图；Fig. 6 is a schematic diagram of a rectangular planar shape structure of a capacitive sensor;

图7是电容传感器的菱形平面形状结构示意图；Fig. 7 is a schematic diagram of a rhombus planar shape structure of a capacitive sensor;

图8是电容传感器的圆形平面形状结构示意图；Fig. 8 is a schematic diagram of a circular planar shape structure of a capacitive sensor;

图9是电容传感器的第一种弧形平面形状结构示意图；Fig. 9 is a schematic diagram of the structure of the first arc-shaped planar shape of the capacitive sensor;

图10是电容传感器的第二种弧形平面形状结构示意图；Fig. 10 is a schematic diagram of the structure of the second arc-shaped planar shape of the capacitive sensor;

图11是电容传感器在不同安装角度下的示意图；Fig. 11 is a schematic diagram of a capacitive sensor at different installation angles;

图12是该应力测量装置在常规注射成型中的实例测试曲线图；Fig. 12 is an example test curve diagram of the stress measuring device in conventional injection molding;

图13是该应力测量装置在重复试验下的实例测试曲线图；Fig. 13 is an example test curve diagram of the stress measuring device under repeated tests;

图14是该装置在不同注塑工艺参数下的实测结果与模拟结果的对比曲线图。Fig. 14 is a graph comparing the measured results and simulated results of the device under different injection molding process parameters.

图中：第一电极1，第二电极2，第一电极线3，第二电极线4，电极条5，电容传感器6，注塑模具定模板7，注塑模具动模板8，注塑模具型腔9，型腔壁10，聚合物熔体11，气体12，水（或芯层熔体）13。In the figure: first electrode 1, second electrode 2, first electrode wire 3, second electrode wire 4, electrode strip 5, capacitive sensor 6, injection mold fixed template 7, injection mold movable template 8, injection mold cavity 9 , cavity wall 10, polymer melt 11, gas 12, water (or core melt) 13.

具体实施方式detailed description

如图1至图5所示，一种电容传感器在聚合物成型加工中的应用，包括以下步骤：As shown in Figures 1 to 5, an application of a capacitive sensor in polymer molding processing includes the following steps:

1）将至少一个电容传感器6固定在聚合物成型模具的内壁上，其中的电容传感器6包括绝缘基材、附着于绝缘基材上的导电电极以及分别与导电电极连接的第一电极线3和第二电极线4；1) Fix at least one capacitive sensor 6 on the inner wall of the polymer molding mold, wherein the capacitive sensor 6 includes an insulating substrate, a conductive electrode attached to the insulating substrate, and first electrode wires 3 and 1 respectively connected to the conductive electrodes. The second electrode wire 4;

2）用信号发生器产生对电容传感器6的初始激励信号，同时该信号传递至锁相放大器的参考输入端；2) Use a signal generator to generate an initial excitation signal for the capacitive sensor 6, and simultaneously transmit the signal to the reference input terminal of the lock-in amplifier;

3）进行聚合物成型加工，聚合物熔体11开始与电容传感器6接触，使电容传感器6的电容及输出信号发生变化，对电容传感器6的输出信号进行去噪处理，并且将去噪后的信号传递至锁相放大器的信号输入端；3) Carry out polymer molding processing, the polymer melt 11 starts to contact with the capacitive sensor 6, the capacitance and output signal of the capacitive sensor 6 are changed, the output signal of the capacitive sensor 6 is denoised, and the denoised The signal is transmitted to the signal input terminal of the lock-in amplifier;

5）将采集到的电压信号转换成应力，从而实现在聚合物成型加工过程中对应力的在线测量。5) Convert the collected voltage signal into stress, so as to realize the online measurement of stress during polymer molding process.

上述步骤5）中，将电压信号转换成应力的具体过程为：当电容传感器6固定在模具内壁上进行测量时，忽略模具的变形对其的影响。对于一种初始各向同性材料来说，它的介电常数为ε，则电容传感器6的电容为：In the above step 5), the specific process of converting the voltage signal into stress is: when the capacitive sensor 6 is fixed on the inner wall of the mold for measurement, the influence of the deformation of the mold on it is ignored. For an initial isotropic material, its dielectric constant is ε, then the capacitance of the capacitive sensor 6 is:

C_θ=C_O(ε+ε_S)(1)C _θ =C _O (ε+ε _S )(1)

上式中，C₀为真空中电极的电容，ε_S为传感器上电极依附的绝缘基材的介电常数，ε为聚合物材料的介电常数，C_θ为具有某安装角度θ的电容传感器6在与聚合物材料接触后电极之间的电容。In the above formula, C ₀ is the capacitance of the electrode in vacuum, ε _S is the dielectric constant of the insulating substrate on which the electrode is attached on the sensor, ε is the dielectric constant of the polymer material, and C _θ is the capacitive sensor with a certain installation angle θ 6 Capacitance between electrodes after contact with polymer material.

当电容传感器6与聚合物材料接触后，它的形变可用二阶张量表示：When the capacitive sensor 6 is in contact with the polymer material, its deformation can be represented by a second-order tensor:

$S S = = [\begin{matrix} {S S}_{xx xxx} & {S S}_{xy xy} & {S S}_{xz xz} \\ {S S}_{yx yx} & {S S}_{yy yy} & {S S}_{yz yz} \\ {S S}_{zx zx} & {S S}_{zy zy} & {S S}_{zz zz} \end{matrix}] - - - - - - ((22))$

当考虑材料的小变形，或对称性时，有S_xy=S_yx,S_xz=S_zx,S_yz=S_zy.这里s_ij可以是描述变形状态的一个任意的二阶张量。When considering the small deformation, or symmetry, of materials, S _xy =S _yx , S _xz =S _zx ,S _yz =S _zy . Here s _ij can be an arbitrary second-order tensor describing the deformation state.

如果选择应变或者应力作为状态变量，则变量s_ij可分别表示应变张量u或者应力张量σ。由应变-介电、应力-介电的关系，则此时的介电张量ε可表示成：If strain or stress is selected as the state variable, the variable s _ij can represent the strain tensor u or the stress tensor σ, respectively. According to the relationship between strain-dielectric and stress-dielectric, the dielectric tensor ε at this time can be expressed as:

$ϵ ϵ = = [\begin{matrix} ϵ ϵ + + {k k}_{11} {s the s}_{xx xxx} + + {k k}_{22} {s the s}_{ll ll} & ϵ ϵ + + {k k}_{11} {s the s}_{xy xy} & ϵ ϵ + + {k k}_{11} {s the s}_{xz xz} \\ ϵ ϵ + + {k k}_{11} {s the s}_{xy xy} & ϵ ϵ + + {k k}_{11} {s the s}_{yy yy} + + {k k}_{22} {s the s}_{ll ll} & ϵ ϵ + + {k k}_{11} {s the s}_{yz yz} \\ ϵ ϵ + + {k k}_{11} {s the s}_{xz xz} & ϵ ϵ + + {k k}_{11} {s the s}_{yz yz} & ϵ ϵ + + {k k}_{11} {s the s}_{zz zz} + + {k k}_{22} {s the s}_{ll ll} \end{matrix}] - - - - - - ((33))$

式中s_ll=s_xx+s_yy+s_zz，k₁、k₂表示应变-介电系数α₁、α₂，或者表示应力-介电系数λ₁、λ₂。In the formula, s _ll =s _xx +s _yy +s _zz , k ₁ and k ₂ represent strain-dielectric coefficients α ₁ and α ₂ , or stress-dielectric coefficients λ ₁ and λ ₂ .

把相应的介电张量（3）带入到上述公式(1),就可以求出在任意变形下的传感器电容的表达式Bringing the corresponding dielectric tensor (3) into the above formula (1), the expression of the sensor capacitance under any deformation can be obtained

${C C}_{θ θ} = = {C C}_{00} ((\sqrt{{ϵ ϵ}_{11} {ϵ ϵ}_{22}} + + {ϵ ϵ}_{S S})) - - - - - - ((44))$

其中，in,

${ϵ ϵ}_{11} {ϵ ϵ}_{22} = = {ϵ ϵ}^{22} + + {ϵk ϵk}_{11} (({s the s}_{xx xxx} {cos cos}^{22} θ θ + + {s the s}_{yy yy} {sin sin}^{22} θ θ + + 22 {s the s}_{xy xy} sin sin θ θ cos cos θ θ + + {s the s}_{zz zz})) + + 22 ϵ ϵ {k k}_{22} {s the s}_{ll ll}$

$+ + {k k}_{11}^{22} [[(({s the s}_{xx xxx} {s the s}_{zz zz} - - {s the s}_{xz xz}^{22})) {cos cos}^{22} θ θ + + (({s the s}_{yy yy} {s the s}_{zz zz} - - {s the s}_{yz yz}^{22})) {sin sin}^{22} θ θ + + 22 (({s the s}_{xy xy} {s the s}_{zz zz} - - {s the s}_{xz xz} {s the s}_{yz yz})) cos cos θ θ sin sin θ θ]] - - - - - - ((55))$

$+ + {k k}_{11} {k k}_{22} {s the s}_{ll ll} (({s the s}_{xx xxx} {cos cos}^{22} θ θ + + {s the s}_{yy yy} {sin sin}^{22} θ θ + + {22 s the s}_{xy xy} cos cos θ θ sin sin θ θ + + {s the s}_{zz zz})) + + {k k}_{22}^{22} {s the s}_{ll ll}^{22}$

在小变形状态下，上述公式可以用泰勒展开的数学近似公式来简化，则有In the state of small deformation, the above formula can be approximated by the mathematical approximation formula of Taylor expansion To simplify, there is

${C C}_{θ θ} = = {C C}_{00} (\begin{matrix} ϵ ϵ + + \frac{{k k}_{11} (({s the s}_{xx xxx} {cos cos}^{22} θ θ + + {s the s}_{yy yy} {sin sin}^{22} θ θ + + 22 {s the s}_{xy xy} sin sin θ θ cos cos θ θ + + {s the s}_{zz zz})) + + 22 {k k}_{22} {s the s}_{ll ll}}{22} \\ + + \frac{{k k}_{11}^{22} [[(({s the s}_{xx xxx} {s the s}_{zz zz} - - {s the s}_{xz xz}^{22})) {cos cos}^{22} θ θ + + (({s the s}_{yy yy} {s the s}_{zz zz} - - {s the s}_{yz yz}^{22})) {sin sin}^{22} θ θ + + 22 (({s the s}_{xy xy} {s the s}_{zz zz} - - {s the s}_{xz xz} {s the s}_{yz yz})) cos cos θ θ sin sin θ θ]]}{22 ϵ ϵ} \\ + + \frac{{k k}_{11} {k k}_{22} {s the s}_{ll ll} (({s the s}_{xx xxx} {cos cos}^{22} θ θ + + {s the s}_{yy yy} {sin sin}^{22} θ θ + + {22 s the s}_{xy xy} cos cos θ θ sin sin θ θ + + {s the s}_{zz zz})) + + {k k}_{22}^{22} {s the s}_{ll ll}^{22}}{22 ϵ ϵ} + + {ϵ ϵ}_{s the s} \end{matrix}) - - - - - - ((66))$

当以应力作为变量时，传感器的介电常数张量为When stress is used as a variable, the dielectric constant tensor of the sensor is

$ϵ ϵ = =$

$[\begin{matrix} ϵ ϵ + + {λ λ}_{11} {σ σ}_{xx xxx} + + {λ λ}_{22} {σ σ}_{ll ll} & {λ λ}_{11} {σ σ}_{xy xy} & {λ λ}_{11} {σ σ}_{xz xz} \\ {λ λ}_{11} {σ σ}_{xy xy} & ϵ ϵ + + {λ λ}_{11} {σ σ}_{yy yy} + + {λ λ}_{22} {σ σ}_{ll ll} & {λ λ}_{11} {σ σ}_{yz yz} \\ {λ λ}_{11} {σ σ}_{xz xz} & {λ λ}_{11} {σ σ}_{yz yz} & ϵ ϵ + + {λ λ}_{11} {σ σ}_{zz zz} + + {λ λ}_{22} {σ σ}_{1111} \end{matrix}] - - - - - - ((77))$

式中σ_ll=σ_xx+σ_yy+σ_zz，则传感器的电容为Where σ _ll =σ _xx +σ _yy +σ _zz , then the capacitance of the sensor is

${C C}_{θ θ} = = {C C}_{00} (\begin{matrix} ϵ ϵ + + \frac{{λ λ}_{11} (({σ σ}_{xx xxx} {cos cos}^{22} θ θ + + {σ σ}_{yy yy} {sin sin}^{22} θ θ + + 22 {σ σ}_{xy xy} sin sin θ θ cos cos θ θ + + {σ σ}_{zz zz})) + + 22 {λ λ}_{22} {σ σ}_{ll ll}}{22} \\ + + \frac{{λ λ}_{11}^{22} [[(({σ σ}_{xx xxx} {σ σ}_{zz zz} - - {σ σ}_{xz xz}^{22})) {cos cos}^{22} θ θ + + (({σ σ}_{yy yy} {σ σ}_{zz zz} - - {σ σ}_{yz yz}^{22})) {sin sin}^{22} θ θ + + 22 (({σ σ}_{xy xy} {σ σ}_{zz zz} - - {σ σ}_{xz xz} {σ σ}_{yz yz})) cos cos θ θ sin sin θ θ]]}{22 ϵ ϵ} \\ + + \frac{{λ λ}_{11} {λ λ}_{22} {σ σ}_{ll ll} (({σ σ}_{xx xxx} {cos cos}^{22} θ θ + + {σ σ}_{yy yy} {sin sin}^{22} θ θ + + {22 σ σ}_{xy xy} cos cos θ θ sin sin θ θ + + {σ σ}_{zz zz})) + + {λ λ}_{22}^{22} {σ σ}_{ll ll}^{22}}{22 ϵ ϵ} + + {ϵ ϵ}_{s the s} \end{matrix}) - - - - - - ((88))$

又由于And because of

$\frac{Δ Δ {V V}_{θ θ}}{{V V}_{00}} = = - - \frac{ΔC ΔC}{C C} = = - - \frac{{C C}_{θ θ} - - {C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{s the s}))}{{C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{s the s}))} - - - - - - ((99))$

其中，ΔV_θ=V_θ-V₀，V_O和V_θ分别表示电容传感器6在与聚合物接触前后电极之间的电压，这样结合上述公式（8）和公式（9），便可得出测试电压信号与应力之间的转换关系。Among them, ΔV _θ =V _θ -V ₀ , V _O and V _θ respectively represent the voltage between the electrodes of the capacitive sensor 6 before and after contact with the polymer, so combining the above formula (8) and formula (9), we can get Test the conversion relationship between voltage signal and stress.

作为一种优选，在上述电容传感器6中，其中的导电电极包括第一电极1和第二电极2，第一电极1和第二电极2位于同一平面内，且第一电极1与第一电极线3连接，第二电极2与第二电极线4连接，第一电极1和第二电极2分别包括多个均匀分散排布的电极条5，并且第一电极1的电极条与第二电极2的电极条相互交错排列且互不连通；为适应不同的成型制品结构或进浇方式，如图6至图10所示，该传感器还可以设计成其他多种样式和多种尺寸，如第一电极1的电极条与第二电极2的电极条相互排列形成的平面形状为矩形或菱形，此时可更适用于对具有平面结构的聚合物成型制品进行测量，上述平面形状还可以为圆形、椭圆形或弧形，此时更适用于对采用中间进浇方式或者含有圆弧或圆形结构的聚合物成型制品进行测量；在聚合物成型过程的在线测量中，可采用两个以上的电容传感器，且每个电容传感器分别以不同的角度固定安装。As a preference, in the above capacitive sensor 6, the conductive electrodes include the first electrode 1 and the second electrode 2, the first electrode 1 and the second electrode 2 are located in the same plane, and the first electrode 1 and the first electrode Line 3 is connected, the second electrode 2 is connected with the second electrode line 4, the first electrode 1 and the second electrode 2 respectively include a plurality of evenly distributed electrode strips 5, and the electrode strips of the first electrode 1 are connected with the second electrode The electrode strips of 2 are arranged alternately and are not connected to each other; in order to adapt to different molded product structures or pouring methods, as shown in Figure 6 to Figure 10, the sensor can also be designed into other styles and sizes, as shown in the first The electrode strips of the first electrode 1 and the electrode strips of the second electrode 2 are arranged to form a plane shape of a rectangle or a rhombus. At this time, it can be more suitable for measuring polymer molded products with a plane structure. The plane shape can also be a circle. Shape, ellipse or arc, at this time it is more suitable for the measurement of polymer molded products that adopt the middle pouring method or contain arc or circular structure; in the online measurement of the polymer molding process, more than two capacitive sensors, and each capacitive sensor is fixedly installed at different angles.

作为进一步优选，上述绝缘基材为薄膜状或片状，绝缘基材的材料为聚酰胺，厚度为5-25μm，导电电极的材料为银、铜、金、铝、锌或铂，导电电极的厚度为20-35μm，并且导电电极通过粘合的方式附着于绝缘基材上，且剥离强度大于1N/mm，而电极条的宽度与相互交错排列的电极条之间的间距的比例可为1:1至1:3，电极条的长度与相互交错排列的电极条之间的间距的比例可大于10:1。As a further preference, the above-mentioned insulating substrate is in the form of a film or a sheet, the material of the insulating substrate is polyamide, and the thickness is 5-25 μm, the material of the conductive electrode is silver, copper, gold, aluminum, zinc or platinum, and the material of the conductive electrode is The thickness is 20-35μm, and the conductive electrode is attached to the insulating substrate by means of adhesion, and the peel strength is greater than 1N/mm, and the ratio of the width of the electrode strips to the spacing between the electrode strips arranged in a staggered manner can be 1 :1 to 1:3, the ratio of the length of the electrode strips to the distance between the electrode strips arranged in a staggered manner may be greater than 10:1.

在聚合物成型过程的在线测量中，采用电容传感器的数目与拟计算的应力变量数目对应，当电容传感器的数目为一个时，在测量时分别以不同的角度固定安装并多次测量，当电容传感器的数目为两个以上时，每个电容传感器分别以不同的角度固定安装。沿着电容传感器所在平面与传感器接触的聚合物熔体，进行剪切应力的测量分析量化时，对应所述电容传感器的数目为三个，每个电容传感器分别以不同的角度固定安装，且每个电容传感器的安装角度均位于0°-90°内，例如上述三个电容传感器分别对应的安装角度可为0°、45°、90°，或者为0°、30°、90°，或者为0°、60°、90°。垂直于电容传感器所在平面与传感器接触的聚合物熔体，进行应力的测量分析量化时，对应所述电容传感器的数目为两个，每个电容传感器分别以不同的角度固定安装，且每个电容传感器的安装角度均位于0°-90°内，例如上述两个电容传感器分别对应的安装角度可为0°、90°，或者为40°、90°，或者为0°、40°。In the online measurement of the polymer molding process, the number of capacitive sensors corresponds to the number of stress variables to be calculated. When the number of capacitive sensors is one, they are fixed and installed at different angles during the measurement and measured multiple times. When the capacitive When the number of sensors is more than two, each capacitive sensor is fixedly installed at different angles. When measuring, analyzing and quantifying the shear stress of the polymer melt in contact with the sensor along the plane where the capacitive sensor is located, the number corresponding to the capacitive sensor is three, and each capacitive sensor is fixedly installed at a different angle, and each The installation angles of each capacitive sensor are within 0°-90°. For example, the installation angles corresponding to the above three capacitive sensors can be 0°, 45°, 90°, or 0°, 30°, 90°, or 0°, 60°, 90°. When measuring, analyzing and quantifying the stress of the polymer melt perpendicular to the plane where the capacitive sensor is in contact with the sensor, the number of corresponding capacitive sensors is two, and each capacitive sensor is fixedly installed at a different angle, and each capacitive The installation angles of the sensors are all within 0°-90°, for example, the installation angles corresponding to the above two capacitive sensors can be 0°, 90°, or 40°, 90°, or 0°, 40°.

为充分阐述本发明的具体实现过程，现以矩形平面形状的传感器（以下简称矩形传感器）为例，做进一步具体说明。In order to fully illustrate the specific implementation process of the present invention, a sensor with a rectangular planar shape (hereinafter referred to as a rectangular sensor) is taken as an example for further detailed description.

在本例中，所用方法同样适用于气体辅助注塑成型、水辅注射成型、夹芯注射成型、微孔发泡注射成型等。本例将用于聚合物成型加工的聚合物材料选为聚碳酸酯，牌号为110，厂商为台湾奇美CHIMEI，所加工的注塑制品为60mm×140mm×2mm的平板，注塑工艺参数如表1所示。In this example, the method used is equally applicable to gas-assisted injection molding, water-assisted injection molding, sandwich injection molding, microcellular foam injection molding, etc. In this example, the polymer material used for polymer molding processing is selected as polycarbonate, the grade is 110, and the manufacturer is Taiwan Chimei CHIMEI. The processed injection molding product is a flat plate of 60mm×140mm×2mm. The injection molding process parameters are shown in Table 1. Show.

表1注塑工艺参数Table 1 Injection molding process parameters

所选用的矩形传感器的所有电极条5具有相同的宽度和长度，且电极条5的宽度与相互交错排列的电极条5之间的间距的比例为1∶1，传感器上的绝缘基材的介电常数ε_s为3。4，聚合物材料的介电常数ε为3。All the electrode strips 5 of the selected rectangular sensor have the same width and length, and the ratio of the width of the electrode strips 5 to the spacing between the electrode strips 5 that are staggered is 1:1, and the insulating base material on the sensor has a The electrical constant ε _s is 3.4, and the dielectric constant ε of the polymer material is 3.

在对上述公式的具体应用过程中，可考虑在注射成型过程中，聚合物熔体在充填阶段，模具表面的聚合物熔体主要受到平面的剪切应力，沿着x、y、z轴方向的正应力，以及熔体重量引起的体应力作用。In the specific application of the above formula, it can be considered that during the injection molding process, the polymer melt on the surface of the mold is mainly subjected to plane shear stress during the filling stage of the polymer melt along the x, y, and z axes. The normal stress of , and the body stress effect caused by the melt weight.

当聚合物在一个很薄的型腔内流动时，通过合理简化，设σ_xy≈0；在粘性熔体的充填阶段，通过线路设计可使正应力差σ_xx-σ_yy忽略不计，即σ_xx-σ_yy≈0；考虑材料的小变形状态，即σ_zx=σ_xz，σ_zy=σ_yz。因此，我们可以通过提取传感器之间的电容差，即电压差值，就能计算出剪切应力σ_zx(σ_xz)、σ_zy(σ_yz)。When the polymer flows in a very thin cavity, through reasonable simplification, σ _xy ≈ 0; in the filling stage of viscous melt, the normal stress difference σ _xx -σ _yy can be neglected through circuit design, that is, σ _xx -σ _yy ≈0; consider the small deformation state of the material, that is, σ _zx =σ _xz , σ _zy =σ _yz . Therefore, we can calculate the shear stress σ _zx (σ _xz ), σ _zy (σ _yz ) by extracting the capacitance difference between the sensors, that is, the voltage difference.

如图11所示，本实施例中矩形传感器会用到三个角度，即分别选择与聚合物熔体成0°、45°和90°夹角（当然，也可选用其他组合下的角度，如0°、30°、90°，或者0°、60°、90°），这样通过采用三个矩形传感器，或一个传感器在相同位置上多次测量，并按要求分别设置传感器的黏贴角度，在同一工艺下可采集到不同角度传感器的实时信号。As shown in Figure 11, in this embodiment, the rectangular sensor will use three angles, that is, select angles of 0°, 45° and 90° with the polymer melt respectively (of course, angles under other combinations can also be used, Such as 0°, 30°, 90°, or 0°, 60°, 90°), so that by using three rectangular sensors, or one sensor to measure multiple times at the same position, and setting the sticking angle of the sensor respectively as required , Real-time signals of different angle sensors can be collected under the same process.

将传感器固定在注塑模具定模板7上，连接测试电路，开始测试，分别采集同一工艺下不同安装角度时的传感器信号。Fix the sensor on the fixed template 7 of the injection mold, connect the test circuit, start the test, and collect the sensor signals at different installation angles under the same process.

如图12所示，其是传感器在安装角度为90°时的测试曲线图，其中横坐标为注塑时间，纵坐标为测试电压值。图12中的测试曲线显示了一个完整的注塑周期，将该实时测试曲线与注塑机具体成型过程相对比，即可分析得知，图中的A点为注塑机开始合模，B点为聚合物熔体开始充填，C点为聚合物熔体开始接触传感器，D点为充填结束进入保压阶段，E点为浇口凝固，F点为注塑机开模。而且，如图13所示，在进一步的重复试验中，在上述同一工艺参数下，测试曲线保持了很好的曲线重复性，从而验证了测试过程及测试结果的有效性。As shown in Figure 12, it is a test graph of the sensor when the installation angle is 90°, where the abscissa is the injection molding time, and the ordinate is the test voltage value. The test curve in Figure 12 shows a complete injection molding cycle. By comparing the real-time test curve with the specific molding process of the injection molding machine, it can be analyzed that point A in the figure is when the injection molding machine starts to close the mold, and point B is polymerization The polymer melt starts to fill, point C is when the polymer melt starts to contact the sensor, point D is when filling ends and enters the pressure holding stage, point E is when the gate is solidified, and point F is when the injection molding machine opens the mold. Moreover, as shown in FIG. 13 , in further repeated tests, under the same process parameters above, the test curve maintained good curve repeatability, thereby verifying the validity of the test process and test results.

在本实施例中，在聚合物材料处于三种工艺条件下，采集用于进行应力计算的角度为0°、45°和90°时的传感器的电压差值，如表2所示。In this embodiment, when the polymer material is under three process conditions, the voltage difference values of sensors used for stress calculation are collected when the angles are 0°, 45° and 90°, as shown in Table 2.

表2PC不同工艺参数下充填过程中的电压差值Table 2PC voltage difference during filling process under different process parameters

应用公式（8）和公式（9）进一步计算出对应的剪切应力，结果如表3所示。Apply formula (8) and formula (9) to further calculate the corresponding shear stress, and the results are shown in Table 3.

表3PC不同工艺参数下充填过程中的剪切应力量化值Table 3PC Quantified value of shear stress during filling process under different process parameters

为进一步充分阐述应用上述公式来计算剪切应力的过程，特别选取两个传感器的角度分别为θ和θ+π/2，来进行以下推导，以作为对上述计算过程的一种示例演示。特别地，此时对应有In order to further fully explain the process of applying the above formula to calculate the shear stress, the angles of the two sensors are specially selected as θ and θ+π/2, and the following derivation is performed as an example demonstration of the above calculation process. In particular, at this time the corresponding

${C C}_{θ θ} - - {C C}_{θ θ + + \frac{π π}{22}} = = \frac{{C C}_{00} {λ λ}_{11}^{22} (({σ σ}_{yz yz}^{22} - - {σ σ}_{xz xz}^{22})) cos cos 22 θ θ}{22 ϵ ϵ} - - - - - - ((1010))$

又由于And because of

$\frac{Δ Δ {V V}_{θ θ}}{{V V}_{O o}} = = - - \frac{{C C}_{θ θ} - - {C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{S S}))}{{C C}_{00} ((ϵ ϵ + + {ϵ ϵ}_{S S}))}$

差分之后，可以得到After difference, we can get

$\frac{{ΔV ΔV}_{θ θ + + \frac{π π}{22}} - - {ΔV ΔV}_{θ θ}}{{V V}_{O o}} = = \frac{{C C}_{θ θ} - - {C C}_{θ θ + + \frac{π π}{22}}}{{C C}_{O o} ((ϵ ϵ + + {ϵ ϵ}_{S S}))} - - - - - - ((1111))$

将上述公式(11)代入公式(10)，即可得到σ_xz、σ_yz与ΔV之间的关系，即Substituting the above formula (11) into formula (10), the relationship between σ _xz , σ _yz and ΔV can be obtained, namely

${σ σ}_{yz yz}^{22} - - {σ σ}_{xz xz}^{22} = = \frac{22 ϵ ϵ ((ϵ ϵ + + {ϵ ϵ}_{S S}))}{{V V}_{O o} {λ λ}_{11}^{22} cos cos 22 θ θ} (({ΔV ΔV}_{θ θ + + \frac{π π}{z z}} - - {ΔV ΔV}_{θ θ})) - - - - - - ((1212))$

更进一步地，若考虑到在实验装置工艺参数的三种聚合物注塑速率下，聚合物熔体流过传感器片时，是沿着y方向流动的，假设xz方向上的剪切应力σ_xz为0，这样上述公式（12）便直接转化为Furthermore, if it is considered that under the three polymer injection rates of the process parameters of the experimental device, when the polymer melt flows through the sensor sheet, it flows along the y direction, assuming that the shear stress σ _xz in the xz direction is 0, so the above formula (12) can be directly transformed into

${σ σ}_{yz yz}^{22} = = \frac{22 ϵ ϵ ((ϵ ϵ + + {ϵ ϵ}_{S S}))}{{V V}_{O o} {λ λ}_{11}^{22} cos cos 22 θ θ} (({ΔV ΔV}_{θ θ + + \frac{π π}{22}} - - {ΔV ΔV}_{θ θ}))$

据此，在此种假设和简化情形下，只需依据两个角度下的传感器的测量结果，便可得出在yz方向上的剪切应力的具体量值。Accordingly, in this hypothetical and simplified situation, the specific magnitude of the shear stress in the yz direction can be obtained only based on the measurement results of the sensors at two angles.

通过上述计算，完成了在注塑成型过程对剪切应力进行在线测量的过程。为进一步验证实验结果的可靠性，通过数值模拟的方法对注塑制品剪切应力进行模拟，并与实验结果做了对比，如表4及图14所示。Through the above calculation, the process of online measurement of the shear stress during the injection molding process is completed. In order to further verify the reliability of the experimental results, the shear stress of injection molded products was simulated by numerical simulation, and compared with the experimental results, as shown in Table 4 and Figure 14.

表4不同注塑速率下的模拟应力与实测应力Table 4 Simulated stress and measured stress at different injection rates

对比分析可知，上述实测结果与模拟结果在同一数量级，并且随着注塑速率的增加，应力都有同样递增的趋势，这进一步验证了该传感器用于注塑成型过程中应力测量的有效性。Comparative analysis shows that the above measured results are in the same order of magnitude as the simulation results, and as the injection rate increases, the stress has the same increasing trend, which further verifies the effectiveness of the sensor for stress measurement in the injection molding process.

上面结合附图对本发明优选的具体实施方式和实施例作了详细说明，但是本发明并不限于上述实施方式和实施例，在本领域技术人员所具备的知识范围内，还可以在不脱离本发明构思的前提下做出各种变化。The preferred specific implementations and examples of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned implementations and examples. Various changes are made under the premise of the inventive concept.

Claims

1. Use of a capacitive sensor in polymer forming processes, characterized by the steps of:

1) fixing a capacitive sensor in a cavity of a polymer forming die or on the inner wall of a mouth die, wherein the capacitive sensor comprises an insulating base material, a conductive electrode attached to the insulating base material, and a first electrode wire and a second electrode wire which are respectively connected with the conductive electrode;

2) generating an initial excitation signal for the capacitive sensor with a signal generator, while the signal is transferred to a reference input of a lock-in amplifier;

3) performing polymer molding processing, enabling the polymer melt to start to contact with the capacitance sensor, changing the capacitance and output signals of the capacitance sensor, performing denoising processing on the output signals of the capacitance sensor, and transmitting the denoised signals to a signal input end of the phase-locked amplifier;

4) collecting a voltage signal at the output end of the phase-locked amplifier by using a signal recorder;

5) the method converts the collected voltage signal into the shear stress, thereby realizing the online measurement of the shear stress in the polymer forming and processing process, and the specific steps of converting the voltage signal into the shear stress are as follows:

5.1) for an initial isotropic material with a dielectric constant, the capacitance of the capacitive sensor is given by:

C_θ＝C₀(+_s)

5.2) when the original isotropic material undergoes deformation, the dielectric constant is expressed as a second order tensor

ϵ = [\begin{matrix} ϵ + k_{1} s_{x x} + k_{2} s_{l l} & ϵ + k_{1} s_{x y} & ϵ + k_{1} s_{x z} \\ ϵ + k_{1} s_{x y} & ϵ + k_{1} s_{y y} + k_{2} s_{l l} & ϵ + k_{1} s_{y z} \\ ϵ + k_{1} s_{x z} & ϵ + k_{1} s_{y z} & ϵ + k_{1} s_{z z} + k_{2} s_{l l} \end{matrix}]

5.3) taking stress as variable and under small deformation conditions, the capacitance of the capacitive sensor is further expressed as

C_{θ} = C_{0} (\begin{matrix} ϵ + \frac{λ_{1} (σ_{x x} \cos^{2} θ + σ_{y y} \sin^{2} θ + 2 σ_{x y} \sin θ \cos θ + σ_{z z}) + 2 λ_{2} σ_{l l}}{2} \\ + \frac{λ_{1}^{2} [(σ_{x x} σ_{z z} - σ_{x z}^{2}) \cos^{2} θ + (σ_{y y} σ_{z z} - σ_{y z}^{2}) \sin^{2} θ + 2 (σ_{x y} σ_{z z} - σ_{x z} σ_{y z}) \cos θ \sin θ]}{2 ϵ} \\ + \frac{λ_{1} λ_{2} σ_{l l} (σ_{x x} \cos^{2} θ + σ_{y y} \sin^{2} θ + 2 σ_{x y} \cos θ \sin θ + σ_{z z}) + λ_{2}^{2} σ_{l l}^{2}}{2 ϵ} + ϵ_{s} \end{matrix})

5.4) depending on the relationship between the change in capacitance of the capacitive sensor and the change in output signal

\frac{{ΔV}_{θ}}{V_{0}} = - \frac{C_{θ} - C_{0} (ϵ + ϵ_{s})}{C_{0} (ϵ + ϵ_{s})}

And combining the step 5.3) to obtain the conversion relation between the collected voltage signal and the shearing stress.

2. Use of the capacitive sensor of claim 1 in polymer molding processes wherein: the conductive electrodes comprise a first electrode and a second electrode, the first electrode and the second electrode are positioned in the same plane, the first electrode is connected with the first electrode wire, and the second electrode is connected with the second electrode wire; the first electrode and the second electrode respectively comprise a plurality of electrode strips which are uniformly distributed, and the electrode strips of the first electrode and the electrode strips of the second electrode are mutually staggered and are not communicated with each other.

3. Use of a capacitive sensor according to claim 2 in a polymer forming process wherein: in the on-line measurement of the polymer forming process, the number of the capacitance sensors is adopted to correspond to the number of the stress variables to be calculated, when the number of the capacitance sensors is one, the capacitance sensors are fixedly installed at different angles respectively and are used for measuring for multiple times, and when the number of the capacitance sensors is more than two, each capacitance sensor is fixedly installed at different angles respectively.

4. Use of a capacitive sensor according to claim 3 in a polymer forming process wherein: in the polymer forming process, after the polymer melt is contacted with the capacitance sensor, the output real-time voltage signal corresponds to the forming processing production process.

5. Use of a capacitive sensor according to claim 2 in a polymer forming process wherein: when measurement analysis and quantification of shear stress are carried out on the polymer melt which is in contact with the sensors along the plane where the capacitive sensors are located, the number of the corresponding capacitive sensors is three, each capacitive sensor is fixedly installed at different angles, and the installation angle of each capacitive sensor is within 0-90 degrees.

6. Use of a capacitive sensor according to claim 2 in a polymer forming process wherein: when the polymer melt which is vertical to the plane where the capacitance sensors are located and is in contact with the sensors is subjected to measurement, analysis and quantification of stress, the number of the corresponding capacitance sensors is two, each capacitance sensor is fixedly installed at different angles, and the installation angle of each capacitance sensor is within 0-90 degrees.

7. Use of a capacitive sensor according to any one of claims 3 to 6 in polymer moulding processes wherein: the electrode strips of the first electrode and the electrode strips of the second electrode are mutually arranged to form a rectangular or rhombic plane shape, and the plane shape is used for measuring a polymer molded product with a plane structure.

8. Use of a capacitive sensor according to any one of claims 3 to 6 in polymer moulding processes wherein: the planar shape formed by mutually arranging the electrode strips of the first electrode and the electrode strips of the second electrode is circular, oval or arc, and the electrode strips are used for measuring polymer molded products which adopt a middle pouring mode or contain arc or circular structures.

9. Use of a capacitive sensor according to claim 2 in a polymer forming process wherein: the insulating base material is in a film shape or a sheet shape, the insulating base material is polyamide, the thickness of the insulating base material is 5-25 mu m, the conductive electrode material is silver, copper, gold, aluminum, zinc or platinum, the thickness of the conductive electrode is 20-35 mu m, the conductive electrode is attached to the insulating base material in an adhesion mode, and the peel strength is more than 1N/mm; the ratio of the width of the electrode strips to the space between the electrode strips which are staggered with each other is 1:1 to 1:3, and the ratio of the length of the electrode strips to the space between the electrode strips which are staggered with each other is more than 10: 1.