Method for predicting cold and warm contact feeling of weft-knitted fabric

Abstract

The invention discloses a method for predicting the contact cold and warm feeling of a weft-knitted fabric, and the method comprises the steps: determining a plurality of data points of a coil center curve based on the form of the weft-knitted fabric; drawing a coil center curve according to the type value points, and obtaining a coil model; constructing a weft-knitted fabric model by using the plurality of coil models; obtaining an assembly body model according to the thermal detection plate, the air layer, the weft-knitted fabric model and the constant-temperature heating plate; the method comprises the following steps: defining attributes of an assembly body model, and carrying out iterative operation of transient heat conduction on the assembly body model; when the heat transfer of the air and the weft-knitted fabric is balanced, obtaining the instantaneous current density of each part of the weft-knitted fabric model; and selecting the maximum instantaneous current density as the contact cool feeling coefficient of the detected weft-knitted fabric. Measurement of the contact cool feeling coefficient is completed by constructing the simulation model of the weft-knitted fabric, and the problems that the debugging time is long and the cost of a testing instrument is high during existing contact cool feeling coefficient testing are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of clothing, and in particular relates to a method for predicting the contact cold and warm sensation of a weft knitted fabric. Background Art

[0002] The heat transfer of fabrics is an important research direction for clothing comfort. The test process of the contact cold and warm feeling of fabrics (contact coolness coefficient) is an instantaneous heat transfer, and the characterization index is Qmax. Qmax directly determines the cold and hot feeling of the human body when it comes into contact with clothing, and is an important factor affecting the comfort of clothing. On the one hand, with the increasing significance of the global greenhouse effect, the summer temperature has repeatedly hit new highs in recent years, so the development of cool fabrics has received more and more attention. If the contact cold feeling of fabrics can be predicted in advance, it can guide the development of cool fabrics and improve the comfort of clothing. On the other hand, in seasons with lower temperatures such as autumn and winter, close-fitting underwear is required to have a good sense of warmth. If the contact warmth of fabrics can be predicted in advance, it can guide the development of thermal underwear fabrics and improve the comfort of wearing. Since the contact cold and warm feeling is generally used to evaluate close-fitting fabrics, and weft knitted fabrics are soft and comfortable, they are suitable for close-fitting fabrics, so it is very necessary to predict the contact cold and warm feeling of weft knitted fabrics. Although the contact cold and warm feeling of weft knitted fabrics can be predicted by the test instrument KES-FB7; however, the debugging time is long during the test and the instrument cost is high. Summary of the invention

[0003] The purpose of the invention is to provide a method for predicting the contact cold and warm feeling of weft knitted fabrics, so as to guide the development of skin-friendly cool fabrics in summer and the development of thermal underwear fabrics in autumn and winter.

[0004] In a first aspect, the present invention provides a method for predicting the touch cold and warm sensation of a weft knitted fabric, comprising the following steps: Step 1: based on the shape of the weft knitted fabric, determine multiple type value points of the coil center curve; draw the coil center curve according to the type value points, and obtain a coil model; and construct a weft knitted fabric model using the multiple coil models; Step 2, obtaining an assembly model; the assembly model includes an air layer and a heat detection plate, a weft knitted fabric model, and a constant temperature heating plate stacked in sequence; the air layer completely covers the weft knitted fabric model; Step 3: Define the properties of the assembly model; Step 4: perform iterative calculation of transient heat conduction on the assembly model; when the heat transfer between air and weft knitted fabric is balanced, obtain the transient flow density of each part of the weft knitted fabric model; select the maximum transient flow density as the contact coolness coefficient of the measured weft knitted fabric.

[0005] Preferably, in the step 2, the thickness of the air layer is consistent with the thickness of the weft knitted fabric model.

[0006] As a preferred method, the method for determining the type value points is as follows: construct three concentric rings O1, O2 and O3 of equal size and mutually circumscribed outer circles; select the first section of the coil column, the first section of the sinker arc, the needle knitting arc, the second section of the sinker arc, and the second section of the coil column on the inner rings of the concentric rings O1, O2 and O3 that match the shape of the coil center curve; take the free endpoints of the two sections of the sinker arc, the connection points of each adjacent section on the coil structure, and the midpoint of the needle knitting arc as seven type value points P1 to P7 arranged in sequence; take the midpoint and two end points of the needle knitting arc as type value points P1, P2, and P3 respectively; take the connection points of the coil column and the sinker arc as type value points P4 and P5 respectively; take the free endpoints of the two sections of the sinker arc as type value points P6 and P7 respectively. Calculate the coordinates of each type value point according to the loop height h, loop distance w, yarn radius and thickness D of the measured weft knitted fabric.

[0007] Preferably, the loop height h is the difference between the vertical coordinates of the shape value points P2 and P4; the loop distance w is the difference between the horizontal coordinates of the shape value points P6 and P7; the yarn radius is the difference between the inner circle radius r2 and the outer circle radius r1; the thickness D is four times the vertical axis coordinates of the shape value points P1 and P6; the shape value points P2, P4, and P6 are mirror-symmetrical with the shape value points P3, P5, and P7, respectively.

[0008] Preferably, the method for drawing the coil center curve is as follows: using a cubic non-uniform rational B-spline curve, accumulating chord lengths at the nodes and parameterizing them to solve the problem of uneven chord lengths, the formula for obtaining the node vector is: Among them, u i+2 for u i+3 is the node vector; p i and p j is the control point; m is the degree of the curve; j = 0,...,n; n+1 is the number of control points, n=m+2; The k-order expression of the spline curve is: Where P(u) is the position vector on the curve; u is the node vector; w i is the weight factor; N i, k (u) is the i-th k-order canonical B-spline basis function; k is the curve power.

[0009] The shape value points obtained in step 1 are used as control points in the non-uniform rational B-spline curve, and the shape of the curve is controlled by using the weight distribution between the vertices of the curve to draw the coil center curve.

[0010] Preferably, in step three, the properties of the assembly model include heat transfer coefficient, thermal conductivity, density and specific heat capacity.

[0011] Preferably, if the measured weft knitted fabric is a pure textile fabric, the thermal conductivity, density and specific heat capacity of the measured weft knitted fabric are directly obtained; if the measured weft knitted fabric is a blended fabric, the thermal conductivity, density and specific heat capacity of the measured weft knitted fabric are calculated using the weighted average method.

[0012] Preferably, after defining the properties of the assembly model, meshing is performed on the assembly model.

[0013] In a second aspect, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the memory stores the computer program; and the processor executes the above-mentioned method for predicting the touch warmth and coldness of weft-knitted fabrics.

[0014] In a third aspect, the present invention provides a readable storage medium storing a computer program; when the computer program is executed by a processor, it is used to implement the above-mentioned method for predicting the touch warmth and coldness of weft-knitted fabrics.

[0015] The present invention has the following beneficial effects: 1. The present invention uses simulation technology to measure the contact coolness coefficient. There is no need to perform spinning, weaving, and performance testing of weft knitted fabrics. The contact coolness coefficient of the fabric can be predicted based on the basic properties of the material, thereby solving the problems of long debugging time and high cost of testing instruments in existing contact coolness coefficient testing.

[0016] 2. The present invention constructs a model of the measured weft knitted fabric according to the designed coil center curve, and improves the accuracy of measuring the contact cool coefficient of the measured weft knitted fabric by assembling the weft knitted fabric model and defining different properties of the measured textile material; at the same time, the present invention can provide guidance for the development of cool fabrics in summer and thermal underwear fabrics in autumn and winter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the measurement position of the type value point of the present invention.

[0018] Figure 2 Schematic diagram of the center curve of the coil in the present invention; wherein (a) is a front view of the center curve of the coil; and (b) is a side view of the center curve of the coil.

[0019] Figure 3 Schematic diagram of the coil model in the present invention; wherein (a) is a schematic diagram of the center curve of the coil model; and (b) is a schematic diagram of the coil unit.

[0020] Figure 4 Schematic diagram of a weft knitted fabric model in the present invention; wherein (a) is a front schematic diagram of the weft knitted fabric model; and (b) is a back schematic diagram of the weft knitted fabric model.

[0021] Figure 5 It is a schematic diagram of the air-fabric-constant temperature heating plate assembly in the present invention.

[0022] Figure 6 It is a schematic diagram of the assembly model in the present invention.

[0023] Figure 7 Schematic diagram of mesh division of the assembly model in the present invention.

[0024] Figure 8 Schematic diagram of the temperature distribution of the air layer in the present invention.

[0025] Fig. 9 It is a schematic diagram of the simulation results of the contact cooling coefficient in the present invention.

[0026] Fig.10 Schematic diagram for comparing the measured and simulated values ​​of thermal resistance and Crowe value of nylon knitted fabric; wherein, (a) is a schematic diagram for comparing thermal resistance; (b) is a schematic diagram for comparing Crowe value.

[0027] Fig.11 Schematic diagram comparing the measured and simulated values ​​of the contact cooling coefficient and heat transfer coefficient of nylon knitted fabric; wherein, (a) is a schematic diagram for comparing the contact cooling coefficient; and (b) is a schematic diagram for comparing the heat transfer coefficient. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] A method for predicting the touch cold and warm sensation of a weft knitted fabric comprises the following steps: Step 1: Build a model of the weft knitted fabric to be tested 1-1. Determine the type value points of weft knitted fabrics like Figure 1 and Figure 2As shown, three concentric circular rings of equal size and mutually circumscribed outer circles are constructed, and a three-dimensional rectangular coordinate system is established with the outer common tangent of the outer circles O2 and O3 of the concentric circular rings away from the outer circle O1 as the x-axis and the straight line passing through the center O1 and perpendicular to the x-axis as the y-axis. Select the first section of the sinker arc, the first section of the circle column, the needle-knitted arc, the second section of the circle column, and the second section of the sinker arc on the inner rings of the concentric rings O1, O2, and O3; connect the first section of the sinker arc, the first section of the circle column, the needle-knitted arc, the second section of the circle column, and the second section of the sinker arc in sequence to form the center curve of the coil; take the free endpoints of the two sections of the sinker arc, the connection points of the adjacent sections on the inner ring, and the midpoint of the needle-knitted arc as seven shape value points P1-P7 arranged in sequence: the midpoint and two end points of the needle-knitted arc are taken as shape value points P1, P2, and P3 respectively; the connection points of the circle column and the sinker arc are taken as shape value points P4 and P5 respectively; the free endpoints of the two sections of the sinker arc are taken as shape value points P6 and P7 respectively. The type value points P2, P4, P6 are mirror-symmetric with the type value points P3, P5, P7. The coordinates of the type value points P1, P2, P4, P6 are expressed as:

[0030] (1) (2) (3) (4) Among them, r1 is the outer circle radius; r2 is the inner circle radius; r is the coil cross-sectional distance; α is the angle formed by the line segment O1O2 and the y-axis; β is the angle formed by the line segment O1P2 and the x-axis.

[0031] The difference between the ordinates of the type value points P2 and P4 is taken as the loop height h of the coil, the difference between the abscissas of the type value points P6 and P7 is taken as the loop distance w of the coil, the difference between the inner radius r2 and the outer radius r1 is taken as the yarn radius (d / 2), and 4 times the coil cross-sectional distance r is taken as the thickness D. Use a stereo microscope to photograph the measured weft knitted fabric and use AI drawing software for image processing. Perform 10 measurements and take the average value to obtain the loop height h, loop distance w, yarn radius (d / 2) and thickness D of the measured weft knitted fabric, and calculate the coordinates of each type value point.

[0032] 1-2. Draw the center curve of the coil According to the interpolation requirements of the endpoints, the k+1 nodes are taken and the cubic NURBS curve (non-uniform rational B-spline curve) is used, that is, k is 3, and the node accumulation chord length parameterization solves the problem of uneven chord length. The expression for obtaining the node vector is: (5) in, and is the node vector; p i and p j is the control point; m is the degree of the curve; j = 0,...,n; n+1 is the number of control points, n=m+k-1=m+2.

[0033] The NURBS curve is selected to draw the center curve of the coil because it can flexibly control the arc length shape and make the curve path in the model close to the actual curve direction. The k-order mathematical expression of the spline curve is: (6) Where P(u) is the position vector on the curve; u is the node vector; w i (≥ 0) is the weight factor; N i, k (u) is the i-th k-order canonical B-spline basis function; k is the curve power.

[0034] The shape points obtained in step 1 are used as control points in the NURBS curve, and the shape of the curve is controlled by using the weight distribution between the vertices of the curve.

[0035] The coordinates of the control points are obtained by combining equations (4) and (6), and the coordinates are substituted into the Solid Works software to draw the points and obtain the center curve of the coil. The yarn is regarded as a single-strand untwisted structure, and the yarn diameter is modeled with a circle. After setting the yarn diameter, the center curve model is contour scanned to obtain a single coil model, such as Figure 3 shown.

[0036] 1-3.Building fabric model like Figure 4 As shown, since the knitted fabric is made of coils connected in the transverse direction and strung in the longitudinal direction, the constructed coil model is copied and arranged in the transverse and longitudinal directions to obtain a weft knitted fabric model. The model size in the figure is 0.1 cm×0.1 cm.

[0037] Step 2: Assemble the model In the existing method, when using the KES-FB7 contact temperature and temperature tester to test actual fabrics, the fabric must first be placed on a sample carrier containing a constant temperature heating plate. When the T-Box component containing a heat detection plate reaches the experimental temperature, it is quickly placed on the fabric to measure the maximum instantaneous heat flux density (Qmax) passing through the fabric. This test process mainly relies on heat transfer between the constant temperature heating plate and the heat detection plate, and the heat detection plate is placed above the fabric.

[0038] So if Figure 5 and Figure 6As shown in the figure, when assembling the model, the weft knitted fabric model is assembled above the constant temperature heating plate; since the upper surface and four sides of the weft knitted fabric model placed on the constant temperature heating plate are always affected by the natural convection of air before and after heat transfer, the air layer (the air component existing around the weft knitted fabric model) has an effect on the heat transfer of the fabric. The weft knitted fabric model and the air layer are assembled to simulate the effect of air convection on the heat transfer of the fabric; assuming that the simulation model only considers the fluid heat transfer within the fabric domain (weft knitted fabric model), the thickness of the air layer should be consistent with the thickness of the fabric. After assembling the air layer, assemble the heat detection plate above the weft knitted fabric model to obtain the assembly model.

[0039] Step 3: Define the properties of the assembly model Define each property in the assembly model. Since the weft knitted fabric model is a collection of fibers, air and water, its thermal conductivity is affected by the three factors. When creating heat transfer analysis conditions, the combined effect of the fabric itself and the fluid should be considered. In the heat transfer process of the constant temperature heating plate-fabric-heat detection plate, heat transfer mainly occurs in three ways: conduction, radiation and convection. Heat conduction is the thermal movement of an object under the action of temperature difference. Thermal conductivity reflects the thermal conductivity of the fabric. Thermal conductivity is the heat transfer coefficient K, and its expression is:

[0040] (7) Where K is the heat transfer coefficient, in W / m 2 ℃; R is the thermal resistance of the fabric, in m 2 ℃ / W; ∆T is the heat transfer time, in seconds; A is the fabric surface area, in cm 2 ; q is the heat flux density, unit is W / ℃.

[0041] The expression of heat flux q is: (8) Among them, λ f is the thermal conductivity, in W / m·℃; t is the fabric temperature, in ℃; n is the normal direction of the contact surface.

[0042] Thermal radiation is the process of electromagnetic wave energy transfer. The total amount of thermal radiation energy emitted by the fabric per unit time can be calculated by the Stefan-Boltzmann law. The expression of the radiation heat flux density q2 is: (9) Where q2 is the radiation heat flux density, in W / m 2 ; ε is the emissivity, which ranges from 0 to 1; δ is the blackbody radiation constant, which is 5.67×10 -8 W / m 2 ·K 4; t1 is the temperature of the heat detection plate, in °C; t2 is the temperature of the constant temperature heating plate, in °C.

[0043] In this embodiment, the temperature of the thermal detection plate is 30 °C, the temperature of the constant temperature heating plate is 20 °C, and the emissivity ε is 1. Substituting into equation (9) the radiation heat flux q2 is approximately 0.0367 W / m 2 , this value is small, so the effect of thermal radiation is ignored in this embodiment.

[0044] The convection cycle is formed by the rising and sinking movement of air and moisture, so that the heat transfer in the fluid is called thermal convection. The expression of the convection heat flux density q3 is: (10) Where q3 is the heat flux density of convection, in W / m 2 ; h is the surface heat transfer coefficient, unit is W / m 2 ·℃;t f is the fabric surface temperature, in °C; t b is the fluid temperature in °C.

[0045] In this embodiment, the heat transfer performance of the weft knitted fabric is tested in a standard atmospheric environment with a temperature of (20±2)°C and a relative humidity of (65±5)%, and the properties of the two fluids, air and water, are set to default values, that is, the thermal conductivity of air and water are 0.0267 W / m·°C and 0.697 W / m·°C, respectively, and the density is 1.205 g / cm 3 , 1 g / cm 3 , and the specific heat capacities are 0.717 J / g·℃ and 4.18 J / g·℃ respectively.

[0046] Since this embodiment is carried out in a constant temperature and humidity environment, no forced convection occurs with the outside world, so only the natural convection phenomenon between the tested weft knitted fabric and the air is considered. In the heat exchange process of the constant temperature heating plate-fabric-heat detection plate, the front side of the tested weft knitted fabric transfers heat to the outside environment by natural convection heat exchange. In summary, this embodiment only considers the heat conduction and heat convection of the tested weft knitted fabric.

[0047] The constant temperature heating plate and the heat detection plate have the same properties except for temperature. Both the constant temperature heating plate and the heat detection plate are made of copper, and the range of their thermal conductivity is 400~413 W / m·℃. In this embodiment, the middle value of 406.5 W / m·℃ is taken, the density is 8.92 g / cm3, and the specific heat capacity is 0.386 J / g·℃.

[0048] If the measured weft knitted fabric is a pure fabric, the thermal conductivity, density and specific heat capacity of the corresponding fabric are directly obtained; if the measured weft knitted fabric is a blended fabric, the properties of the blended fabric are obtained by weighted average method. In this embodiment, two fiber blends are used as the measured weft knitted fabric, and the method for obtaining various properties thereof is as follows:

[0049] (1) Thermal conductivity λ of blended fabrics f The expression is: (11) Among them, λ f is the thermal conductivity of blended fabrics, in W / m·℃; p is the thermal conductivity of fiber 1 in the blended fabric; s Thermal conductivity of fiber 2 in blended fabric; γ is the proportion of fiber 1.

[0050] (2) Density ρ of blended fabric f The expression is: (12) Among them, ρ f is the density of the blended fabric, in g / cm 3 ρ p is the density of fiber 1 in the blended fabric; ρ s is the density of fiber 2 in the blended fabric.

[0051] (3) Specific heat capacity c of blended fabric f The expression is: (13) Among them, c f is the specific heat capacity of blended fabrics, in J / g·℃; c p is the specific heat capacity of fiber 1 in the blended fabric; c s is the specific heat capacity of fiber 2 in the blended fabric.

[0052] Step 4: Mesh Division like Figure 7 As shown in the figure, after assigning the properties of the constant temperature heating plate, weft knitted fabric and thermal detection plate in turn, the grid size is set. The grid size directly affects the calculation accuracy and speed. During the simulation process, after many attempts, when the grid of the weft knitted fabric is set to 0.05 mm, the number of grid units is 399785, the number of nodes is 1099377, the coil surface units are uniform, and the simulation quality is good. Because the heat source components of the constant temperature heating plate and the thermal detection plate are the same, they are set to the same size of grid, and their maximum unit size is 0.2 mm.

[0053] Step 5: Simulate heat transfer After meshing, set a time step of 3s, and perform iterative calculations of transient heat conduction in ANSYS workbench (co-simulation environment). Since heat transfer occurs when there is a temperature difference between the fabric system and the external environment, the heat transfer coefficient K and the convection heat flux density q3 are set during the heat transfer process; the fabric is regarded as a cyclic organization with the same micro-element repeatedly stacked, and the energy change inside the coil follows the following equation:

[0054] (14) Where, T is time, unit is s; τ is the temperature of the microelement, unit is ℃; x, y, z are spatial coordinates; Φ is the internal heat source per unit volume per unit time.

[0055] When the heat transfer between air and weft knitted fabric is balanced, obtain the cloud diagram of the temperature change of the air layer on the surface of the weft knitted fabric, such as Figure 8 As shown in the figure, it can be seen that the temperature of the air layer presents a gradient change in the longitudinal direction. The fluctuation of the isothermal surface is affected by the anisotropy of the weft knitted fabric and fluid factors such as air and moisture, resulting in a decreasing trend of the temperature in the thickness direction of the fabric.

[0056] In heat transfer, heat is transferred from the constant temperature heating plate to the fabric along the thickness direction of the fabric and radiated to the surroundings, so that the part of the fabric in direct contact with the constant temperature heating plate is first affected by heat and diffuses along the axial direction of the fabric, and finally the contact coolness coefficient (maximum instantaneous current density) of the sample is obtained, such as Fig. 9 As shown in the figure, the maximum instantaneous current density is 0.18372 W / cm 2 ; The greater the contact coolness coefficient, the cooler the contact coolness of the knitted fabric. Fig. 9 In the figure, since the circle column part floats on the surface of the fabric and is in direct contact with the constant temperature heating plate, the heat flux (instantaneous flow density) flowing through this area per unit area is large and is red-orange; while the needle-knitted arc or sinking arc is pressed under the circle column and does not directly contact the constant temperature heating plate with higher temperature, so the heat flux per unit area is small and is blue-green.

[0057] Step 4: Model Validation 4-1. 9 pieces of nylon / spandex cool weft knitted fabrics of different specifications were selected, the yarn linear density was 40D, and the fabric specifications were shown in Table 1. The thermal performance parameters (contact coolness coefficient and heat transfer coefficient) of the selected 9 pieces of weft knitted fabrics were measured using the present invention and the traditional method respectively.

[0058] Table 1 Fabric specifications Sample No. Element <![CDATA[Wales per 5 cm (number of courses) -1 )]]> <![CDATA[Warp density / (number of coils · (5 cm) -1 )]]> Thickness / mm <![CDATA[Grammage / (g·m -2 )]]> <![CDATA[1 # ]]> 92% nylon 8% spandex 125 201 0.36 170 <![CDATA[2 # ]]> 90% nylon 10% spandex 92 183 0.35 155 <![CDATA[3 # ]]> 88% nylon 12% spandex 130 187 0.36 165 <![CDATA[4 # ]]> 87% nylon 13% spandex 108 221 0.34 160 <![CDATA[5 # ]]> 86% nylon 14% spandex 129 195 0.37 170 <![CDATA[6 # ]]> 85% nylon 15% spandex 131 217 0.34 175 <![CDATA[7 # ]]> 82% nylon 18% spandex 95 171 0.33 150 <![CDATA[8 # ]]> 80% nylon 20% spandex 132 271 0.40 180 <![CDATA[9 # ]]> 72% nylon 28% spandex 123 192 0.36 160 4-2. In the modeling process, the characteristic parameter values ​​of each weft plain knitted fabric are shown in Table 2 below; the basic property parameters are as follows: the thermal conductivity of nylon ranges from 0.244 W / m·℃ to 0.337 W / m·℃, with the middle value of 0.2905 W / m·℃; the thermal conductivity of spandex is 0.042 W / m·℃. The density of nylon is 1.14 g / cm 3 ; The spandex density ranges from 1.0 to 1.3 g / cm 3 , taking the middle value of 1.2 g / cm. The specific heat capacity of nylon is 2.05 J / g·℃; the specific heat capacity of spandex ranges from 1.5 to 1.6 J / g·℃, taking the middle value of 1.55 J / g·℃. After the modeling is completed, the thermal performance parameters of the weft knitted fabric are measured.

[0059] Table 2 Characteristic parameter values Sample No. d / mm w / mm h / mm r / μm <![CDATA[r1 / μm]]> <![CDATA[r2 / μm]]> α / (°) β / (°) <![CDATA[1 # ]]> 0.170 0.415 0.341 90.0 201.8 116.8 27.4 13.2 <![CDATA[2 # ]]> 0.169 0.493 0.238 87.5 229.7 145.2 30.7 13.1 <![CDATA[3 # ]]> 0.165 0.384 0.289 90.0 219.5 136.9 16.7 3.9 <![CDATA[4 # ]]> 0.166 0.499 0.277 85.0 243.0 160.0 16.8 2.8 <![CDATA[5 # ]]> 0.159 0.408 0.308 92.5 190.6 111.1 23.3 4.8 <![CDATA[6 # ]]> 0.160 0.446 0.238 85.0 210.4 130.4 25.8 9.5 <![CDATA[7 # ]]> 0.168 0.366 0.398 82.5 247.7 163.9 63.4 9.6 <![CDATA[8 # ]]> 0.164 0.378 0.258 97.5 176.0 109.0 33.1 15.9 <![CDATA[9 # ]]> 0.170 0.464 0.361 90.0 187.8 102.8 26.6 17.7 Referring to GB / T 35263-2017 “Testing and evaluating the instantaneous coolness of textiles upon contact”, the KES-F7 contact warm and cold feeling tester was used to test the contact coolness coefficient (Qmax) of the fabric. Referring to GB / T 35762-2017 “Test method for thermal transfer performance of textiles - flat plate method”, the YG606D textile thermal insulation instrument was used to test the heat transfer coefficient, thermal resistance and Crowe value of the fabric. The measured contact coolness coefficient, heat transfer coefficient, thermal resistance and Crowe value are shown in Table 3.

[0060] Table 3 Measured thermal performance parameters Sample No. Element <![CDATA[Cool touch coefficient / (W·cm 2 )]]> <![CDATA[Heat transfer coefficient / (W / m 2 ·°C)]]> <![CDATA[Thermal resistance / (m 2 ·℃·W -1 )]]> Clo value / clo <![CDATA[1 # ]]> 92% nylon 8% spandex 0.186 891.3 0.0011 0.0072 <![CDATA[2 # ]]> 90% nylon 10% spandex 0.184 760.9 0.0013 0.0085 <![CDATA[3 # ]]> 88% nylon 12% spandex 0.181 522.7 0.0019 0.0124 <![CDATA[4 # ]]> 87% nylon 13% spandex 0.180 594.9 0.0017 0.0108 <![CDATA[5 # ]]> 86% nylon 14% spandex 0.179 465.9 0.0021 0.0138 <![CDATA[6 # ]]> 85% nylon 15% spandex 0.177 251.5 0.0040 0.0256 <![CDATA[7 # ]]> 82% nylon 18% spandex 0.176 233.5 0.0043 0.0276 <![CDATA[8 # ]]> 80% nylon 20% spandex 0.172 226.6 0.0044 0.0285 <![CDATA[9 # ]]> 72% nylon 28% spandex 0.166 110.8 0.0090 0.0582 The measured and simulated results of thermal resistance and Crowe value of 9 pieces of cool nylon knitted fabrics are shown in Fig.10 As shown. Fig.10 It can be seen that with the increase of nylon fiber content, the measured and simulated values ​​of thermal resistance and Crowe value show a decreasing trend, and the average error between the simulated value and the measured value is about 5%. Fig.11 As shown, it can be seen that when the thickness is basically the same, as the nylon content decreases, that is, the spandex content increases, the contact coolness coefficient of the fabric gradually decreases. This is because nylon is a cool material, while spandex is a non-cool material. The average errors between the simulated values ​​and the measured values ​​of the contact coolness coefficient and the heat transfer coefficient are 2.4% and 4.8%, respectively. In summary, the present invention uses simulation technology to obtain the contact coolness coefficient and heat transfer coefficient of the fabric, and the error is small, indicating that the method has good feasibility.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. That is, all equivalent changes and revisions made according to the content of the patent application scope of the present invention are within the technical scope of the present invention.

Claims

1. A method for predicting the touch warmth and coldness of a weft knitted fabric, characterized in that: The following steps are involved: Step 1: based on the shape of the weft knitted fabric, determine multiple type value points of the coil center curve; draw the coil center curve according to the type value points, and obtain a coil model; and construct a weft knitted fabric model using the multiple coil models; Step 2, obtaining an assembly model; the assembly model includes an air layer and a heat detection plate, a weft knitted fabric model, and a constant temperature heating plate stacked in sequence; the air layer completely covers the weft knitted fabric model; Step 3: Define the properties of the assembly model; Step 4: perform iterative calculation of transient heat conduction on the assembly model; when the heat transfer between air and weft knitted fabric is balanced, obtain the transient flow density of each part of the weft knitted fabric model; The maximum instantaneous current density is selected as the contact coolness coefficient of the tested weft knitted fabric.

2. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 1, characterized in that: In the step 2, the thickness of the air layer is consistent with the thickness of the weft knitted fabric model.

3. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 1, characterized in that: The method for determining the type value points is as follows: construct three concentric circular rings O1, O2 and O3 of equal size and mutually circumscribed outer circles; select the first section of the coil column, the first section of the sinker arc, the needle knitting arc, the second section of the sinker arc, and the second section of the coil column of the coil structure that matches the shape of the coil center curve on the inner rings of the concentric circular rings O1, O2 and O3; take the free end points of the two sections of the sinker arc, the connection points of each adjacent section on the coil structure, and the midpoint of the needle knitting arc as seven type value points P1-P7 arranged in sequence; calculate the coordinates of each type value point according to the loop height h, loop distance w, yarn radius and thickness D of the measured weft knitted fabric.

4. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 3, characterized in that: The loop height h is the difference between the vertical coordinates of the shape value points P2 and P4; the loop distance w is the difference between the horizontal coordinates of the shape value points P6 and P7; the yarn radius is the difference between the inner circle radius r2 and the outer circle radius r1; the thickness D is four times the vertical axis coordinates of the shape value points P1 and P6; The type value points P2, P4, and P6 are mirror-symmetrical to the type value points P3, P5, and P7 respectively.

5. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 1, characterized in that: The method for drawing the coil center curve is as follows: using a cubic non-uniform rational B-spline curve, parameterizing the node accumulation chord length to solve the problem of uneven chord length, and the formula for obtaining the node vector is: Among them, u i+2 for u i+3 is the node vector; p i and p j is the control point; m is the degree of the curve; j = 0,...,n; n+1 is the number of control points, n=m+2; The k-order expression of the spline curve is: Where P(u) is the position vector on the curve; u is the node vector; w i is the weight factor; N i, k (u) is the i-th k-order canonical B-spline basis function; k is the power of the curve; The shape value points obtained in step 1 are used as control points in the non-uniform rational B-spline curve, and the shape of the curve is controlled by using the weight distribution between the vertices of the curve to draw the coil center curve.

6. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 1, characterized in that: In the step three, the properties of the assembly model include heat transfer coefficient, thermal conductivity, density and specific heat capacity.

7. A method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 6, characterized in that: If the measured weft knitted fabric is a pure textile fabric, the thermal conductivity, density and specific heat capacity of the measured weft knitted fabric are directly obtained; if the measured weft knitted fabric is a blended fabric, the thermal conductivity, density and specific heat capacity of the measured weft knitted fabric are calculated using the weighted average method.

8. The method for predicting the contact cold and warm sensation of a weft knitted fabric according to claim 1, characterized in that: After defining the properties of the assembly model, mesh the assembly model.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: The memory stores a computer program; the processor executes a method for predicting the touch warmth and coldness of a weft knitted fabric as described in any one of claims 1 to 8.

10. A readable storage medium storing a computer program; characterized in that: When the computer program is executed by a processor, it is used to implement a method for predicting the touch warmth and coldness of a weft knitted fabric as described in any one of claims 1 to 8.

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