Methods and applications of obtaining fabric mechanical parameters in 3D garment CAD

Abstract

This invention relates to a method and application for obtaining fabric mechanical parameters in 3D clothing CAD. The fabric mechanical parameters include the fabric's elongation at constant force, shear stiffness, areal density, and flexural stiffness. The values ​​of the fabric's elongation at constant force and shear stiffness were obtained through literature retrieval; the fabric's areal density was obtained through actual measurement; and the flexural stiffness was obtained through actual fabric drape measurement and fabric drape simulation. The fabric mechanical parameters in 3D clothing simulation are obtained using the method described above for obtaining fabric mechanical parameters in 3D clothing CAD. The parameters obtained by this method in 3D clothing CAD have clear physical meanings and can achieve accurate clothing simulation in 3D clothing simulation.

Description

Technical Field

[0001] This invention belongs to the field of clothing simulation technology, and relates to a method for obtaining fabric mechanical parameters in three-dimensional clothing CAD and its application. Background Technology

[0002] 3D garment simulation simulates the stitching of garment pieces onto a virtual human body surface, obtaining the shape of the garment hanging on the body. Using this technology in 3D garment CAD allows for the timely identification and modification of pattern problems through virtual garment evaluation, thereby accelerating the garment product design and development process and reducing costs in terms of manpower, materials, and other aspects. 3D garment simulation is considered a core technology of Industry 4.0, combining the Internet of Things and artificial intelligence, and is expected to lead industry trends.

[0003] Although computer graphics pioneered 3D clothing simulation, the goal of simulating character clothing in animation and games is to obtain shapes that resemble clothing. Furthermore, to achieve real-time dynamic changes in clothing, physical realism is often sacrificed. The shape of clothing on the body surface can be divided into two parts: the part in contact with the body and supported by the body, whose shape is primarily determined by the body surface; and the unsupported part, which hangs freely under its own weight, forming a free yet stable mechanical state. This part reflects different clothing styles and aesthetic characteristics, and its shape mainly depends on the mechanical properties of the fabric.

[0004] Unlike other continuous materials such as films and sheets, clothing is a fibrous aggregate formed by spinning and weaving fibers. Therefore, it possesses complexities such as discontinuity, nonlinearity, and viscoelasticity, making drape prediction extremely difficult. Unlike clothing simulations in animation and games, clothing simulation in CAD requires accurately simulating the shape differences caused by different fabrics. To obtain accurate fabric simulation, the fabric's mechanical model and mechanical parameters are crucial. While mechanical modeling technology is relatively mature, most CAD systems currently use particle models to describe the mechanical behavior of fabrics. Accurate input of fabric mechanical parameters is essential. These parameters are summarized in Table 1.

[0005] Table 1 Fabric mechanical parameters used in garment CAD

[0006]

[0007] Currently, the mechanical parameters used in 3D garment simulation in apparel CAD can be divided into two categories: virtual parameters obtained through simulated fabric drape testing and parameters obtained through actual measurement. Fabric drape is generally tested by measuring the shape formed when a circular piece of fabric is placed on a circular tray with a diameter half that of the fabric. Different fabrics will form different projected areas, numbers, and sizes of drape waves, thus reflecting different mechanical properties. Because drape testing is relatively simple and the equipment is relatively inexpensive, some CAD systems have established drape simulation models to simulate fabric drape testing. By adjusting the mechanical parameters, a shape similar to the actual drape test is obtained, and then these parameters are used as virtual mechanical parameters for the fabric in garment simulation.

[0008] Unlike the deformation of films or sheets, the drape of clothing fabrics is primarily caused by their own weight, resulting in a small load but significant deformation, especially bending, which falls under the category of small stress, large strain problems in elasticity. The textile industry has developed specialized mechanical property testing systems for fabric deformation in clothing, including the Kawabata Fabric Styler (KES-FB) from Japan and the FAST rapid fabric evaluation system from Australia. Another option is the Fabric Test Kit (FTK), which is used only in a few CAD systems.

[0009] Currently, the virtual mechanical parameters obtained through drape testing simulations can only be used for clothing simulation; the values ​​lack real physical meaning, and their accuracy for clothing simulation has not been fully confirmed. Furthermore, this method requires a specific fabric drape simulator, which is not necessarily included in CAD systems. For example, the Modaris 3D Fit 3D clothing simulation system from the French company Lectra only displays fabric drape simulation results in its fabric database, without including the fabric drape simulator. For any given fabric, it is necessary to find the closest matching fabric in the fabric library based on the fabric specifications (the drape effect of these fabrics differs significantly from reality). If none is found, the fabric must be sent to a company in France for testing and simulation to obtain its parameters—a lengthy and expensive process.

[0010] The KES-FB system is widely used in CAD systems due to its measurement principles and system accuracy. However, the problem is that the system consists of four devices and is expensive. Because these mechanical properties are not commercially available measurements, most testing institutions do not possess them; only a few universities and research institutions do. Therefore, the mechanical parameters of fabrics used in clothing design are not easy to obtain.

[0011] The FAST system is often used as a lower-cost alternative to the KES-FB system, and its parameters are also used in CAD systems; some CAD systems can even use parameters from these two systems for simulation. However, due to the limitations of its measurement principles and parameters, the accuracy of its parameters in clothing simulation remains to be verified.

[0012] In summary, current fabric mechanics parameters used in various apparel CAD systems include both virtual and measured parameters. Some virtual parameters are dimensionless, while others are similar to measured parameters. Measured parameters vary in units and numerical ranges due to different measurement systems. The complexity of textile material mechanics, the diversity of performance parameters, and the differences in testing systems can all lead to difficulties and even errors in inputting parameters during CAD use. Apparel CAD still urgently needs a simple method to provide mechanics parameters with clear physical meaning for accurate fabric simulation. Summary of the Invention

[0013] The purpose of this invention is to solve the problems existing in the prior art and to provide a method and application for obtaining fabric mechanical parameters in three-dimensional clothing CAD.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] Methods for obtaining fabric mechanical parameters in 3D clothing CAD, the fabric is woven fabric, and the fabric mechanical parameters are the fabric's elongation at constant force, the fabric's shear stiffness, the fabric's areal density and the fabric's bending stiffness.

[0016] The value of the constant force elongation of the fabric is any value within the interval [a,b], where a and b are the minimum and maximum values ​​of the elongation (EMT) of more than 312 kinds of woven fabrics with different fiber materials and structures collected through literature retrieval when the tensile stress is 500cN / cm, respectively.

[0017] The shear stiffness of the fabric is any value within the interval [c,d], where c and d are the minimum and maximum values ​​of the shear stiffness measured by the KES-FB Kawabata style instrument for more than 312 kinds of woven fabrics with different fiber materials and structures collected through literature retrieval.

[0018] The fabric's areal density is obtained through actual measurement;

[0019] The steps to obtain the bending stiffness value of the fabric are as follows:

[0020] (1) Conduct actual measurements of fabric drape to obtain the drape wave number formed by drape, and determine the corresponding range of bending stiffness values ​​based on the drape wave number.

[0021] The corresponding relationships between the suspension wave number and the range of bending stiffness values ​​are as follows: suspension wave number ≤ 4, bending stiffness ≥ 120 μN·m; suspension wave number = 5, 60 μN·m ≤ bending stiffness < 120 μN·m; suspension wave number = 6, 25 μN·m ≤ bending stiffness < 60 μN·m; suspension wave number = 7, 10 μN·m ≤ bending stiffness < 25 μN·m; suspension wave number = 8, 4 μN·m ≤ bending stiffness < 10 μN·m.

[0022] (2) Continuously select bending stiffness values ​​from the corresponding bending stiffness range, and combine them with the values ​​of the constant force elongation of the fabric, the values ​​of the shear stiffness of the fabric and the values ​​of the areal density of the fabric to simulate the fabric drape test until the deviation between the simulated drape coefficient and the measured drape coefficient (deviation = |measured drape coefficient - simulated drape coefficient| / measured drape coefficient × 100%) is less than 5%. The last selected bending stiffness value is the bending stiffness value of the fabric to be obtained.

[0023] As a preferred technical solution:

[0024] As described above, in the method for obtaining fabric mechanical parameters in 3D clothing CAD, in step (2), the bending stiffness values ​​selected from the corresponding bending stiffness range are arranged in order as an arithmetic progression with a tolerance of m. The minimum value of the arithmetic progression is the lower limit of the bending stiffness range. When the bending stiffness is ≥120μN·m, m=10. In other cases, m=(upper limit of the bending stiffness range - lower limit of the bending stiffness range)×10%.

[0025] It should be noted that when 60 μN·m ≤ bending stiffness < 120 μN·m, the upper limit of the range of bending stiffness values ​​is 120 μN·m; when 25 μN·m ≤ bending stiffness < 60 μN·m, the upper limit of the range of bending stiffness values ​​is 60 μN·m; when 10 μN·m ≤ bending stiffness < 25 μN·m, the upper limit of the range of bending stiffness values ​​is 25 μN·m; and when 4 μN·m ≤ bending stiffness < 10 μN·m, the upper limit of the range of bending stiffness values ​​is 10 μN·m.

[0026] If the termination condition is not met (i.e., the deviation between the simulated and measured sag coefficients is less than 5%), the value of m should be adjusted. Starting from the bending stiffness with the smallest deviation in sag coefficient, m can be set to half or even smaller than the original value (m is 1 / 4 of the original value) and simulation should be performed. If the termination condition is still not met after reducing the value of m, the two cases should be handled separately depending on whether the bending stiffness with the smallest deviation in sag coefficient is near the upper or lower limit of the value range. If it is close to the upper limit, the simulation should continue to be increased. If it is close to the lower limit, the simulation should be decreased.

[0027] As described above, in the method for obtaining fabric mechanical parameters in 3D clothing CAD, in step (2), the fabric drape test simulation is carried out in the CAD system according to the method specified in GB / T23329-2009 standard. Specifically, a circular sample with a diameter of 24cm is suspended on a horizontal circular clamping plate with a diameter of 12cm.

[0028] The present invention also provides a 3D clothing simulation method, which involves determining the clothing pattern (completed using a CAD system), the stitch definition (completed using a CAD system), and the mechanical parameters of the fabric, and then performing clothing simulation in CAD. The mechanical parameters of the fabric are obtained using the method for obtaining fabric mechanical parameters in 3D clothing CAD as described in any of the above claims.

[0029] As a preferred technical solution:

[0030] As described above, the 3D clothing simulation method of the present invention is more suitable for clothing simulation using the Modaris 3D Fit 3D CAD system from Lectra, France, because the fabric drape simulation and skirt simulation verification used in the method of the present invention are both completed using the Modaris 3D Fit 3D CAD system from Lectra, France.

[0031] Beneficial effects:

[0032] (1) For any fabric with unknown mechanical parameters, the time-consuming and expensive mechanical performance test can be avoided. Only a simple fabric drape test is required. Using this method, three-dimensional clothing CAD users can obtain the mechanical parameters of the fabric and achieve accurate clothing simulation.

[0033] (2) The fabric mechanical parameters obtained by this method are based on the measured values ​​of the KES-FB Kawabata style instrument. Compared with other dimensionless virtual mechanical parameters obtained by simulating fabric drape test, each parameter has a clear physical meaning. Attached Figure Description

[0034] Figure 1 For fabric drape simulation model;

[0035] Figure 2 This is a side view of the fabric drape simulation results;

[0036] Figure 3 This is a top view of the fabric drape simulation results;

[0037] Figure 4 This is a simulation diagram of the suspension when the suspension wave number is 8;

[0038] Figure 5 This is a simulation diagram of the suspension when the suspension wave number is 7;

[0039] Figure 6 This is a simulation diagram of the suspension when the suspension wave number is 6;

[0040] Figure 7 This is a simulation diagram of the suspension when the suspension wave number is 5;

[0041] Figure 8 This is a simulation diagram of the suspension when the suspension wave number is 4;

[0042] Figure 9 A drape test diagram for polyester crepe satin;

[0043] Figure 10 A simulation diagram of the drape of polyester crepe satin;

[0044] Figure 11 This is a drape test diagram for raw fabric.

[0045] Figure 12 This is a simulation diagram of the drape of the raw fabric.

[0046] Figure 13 Diagram showing the drape test of taffeta;

[0047] Figure 14 A simulation diagram of the drape of taffeta;

[0048] Figure 15 This is a drape test diagram for denim fabric.

[0049] Figure 16 This is a simulation diagram of the drape of denim fabric.

[0050] Figure 17 This is a sample image of a short skirt.

[0051] Figure 18 The image shows the actual skirt made of polyester crepe satin.

[0052] Figure 19 This is a simulated dress made of polyester crepe satin.

[0053] Figure 20 The image shows the actual skirt made of greige fabric.

[0054] Figure 21 This is a simulated dress made of greige fabric;

[0055] Figure 22 The image shows an actual dress made of taffeta fabric.

[0056] Figure 23 This is a simulated dress made of taffeta fabric.

[0057] Figure 24 This is an actual picture of a skirt made of denim.

[0058] Figure 25 This is a simulated dress made of denim fabric;

[0059] Figure 26 A schematic diagram showing the actual front width dimensions of the skirt;

[0060] Figure 27 A schematic diagram for simulating the front width dimension of a skirt;

[0061] Figure 28 This is a schematic diagram showing the actual side width dimensions of the skirt.

[0062] Figure 29 This is a schematic diagram for simulating the extraction of the width dimension of a skirt. Detailed Implementation

[0063] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0064] The purpose of this invention is to provide a method for obtaining fabric mechanical parameters in 3D clothing CAD for 3D clothing simulation. Specifically, it includes several aspects: obtaining the numerical range of measured fabric KES-FB parameters (i.e., fabric mechanical parameters); obtaining parameters that significantly affect drape simulation; and determining the values ​​of each mechanical parameter according to their degree of influence. The details are as follows:

[0065] (1) The range of measured KES-FB parameters was obtained through literature review;

[0066] Through literature retrieval, mechanical property parameters of 312 woven fabrics with different fiber materials and structures were collected using a KES-FB Kawabata styler. The numerical ranges of each parameter are summarized in Table 2.

[0067] Table 2 Range of measured fabric mechanical parameters

[0068]

[0069] (2) Obtain parameters that have a significant impact on the suspension simulation;

[0070] like Figures 1-3As shown, a fabric drape model was established to simulate fabric drape testing. Based on the value range of each parameter, a five-level orthogonal experiment was designed for these four parameters (as shown in Table 3), resulting in 25 data combinations. Fabric mechanical parameters of these combinations were used to simulate fabric drape testing, and the drape coefficient (the ratio of the projected area of ​​the draped sample to the projected area of ​​the undraped sample) was calculated. The fabric drape testing simulation was conducted in a CAD system according to the method specified in GB / T23329-2009 standard.

[0071] Univariate analysis using a general linear model in SPSS was used to analyze the effects of each parameter on the drape coefficient and drape wave number. The results are shown in Tables 4 and 5. It was found that the bending stiffness of the fabric has a significant effect on both the drape coefficient and the wave number, the areal density of the fabric has a significant effect on the drape coefficient but no significant effect on the drape wave number, while the constant force elongation and shear stiffness of the fabric have no significant effect.

[0072] Table 3. Factor Level Table for Orthogonal Experiment

[0073]

[0074] Table 4. Analysis results for univariate sag coefficient

[0075]

[0076] Table 5. Analysis results for univariate sag coefficient

[0077]

[0078] (3) Methods for determining the values ​​of each parameter;

[0079] The parameters are divided into non-significantly affecting parameters: fabric elongation at constant force and fabric shear stiffness; and significantly affecting parameters: fabric areal density and fabric bending stiffness.

[0080] Since the parameters of constant force elongation and shear stiffness of the fabric have no significant effect on the drape shape, the median value of the measured values ​​obtained from the literature can be taken: the constant force elongation of the fabric is 5.81%; the shear stiffness of the fabric is 0.98 N / m. Both can also be any other value within the range of measured values ​​obtained from the literature.

[0081] Since the areal density can be obtained by weighing, the areal density value of the fabric is obtained through actual measurement.

[0082] The steps to obtain the bending stiffness value of the fabric are as follows:

[0083] (I) Conduct actual measurements of fabric drape to obtain the drape wave number, and determine the corresponding range of bending stiffness values ​​based on the drape wave number; for example... Figures 4-8 As shown, by taking the weight (380g / m 2 ), medium (185g / m 2 ), light (10g / m 2 Using three different areal densities, and combining the values ​​of the fabric's elongation at constant force and shear stiffness, we conducted suspension simulations of bending stiffness from the minimum to the maximum value. We found that, independent of the areal density, the bending stiffness can be divided into five levels based on the suspension wavenumber.

[0084] Flexible type: Overhang wave number = 8, 4μN·m ≤ bending stiffness < 10μN·m;

[0085] Softer type: Overhang wave number = 7, 10 μN·m ≤ bending stiffness < 25 μN·m;

[0086] Standard type: Suspension wave number = 6, 25 μN·m ≤ bending stiffness < 60 μN·m;

[0087] Stiffer type: Overhang wave number = 5, 60 μN·m ≤ bending stiffness < 120 μN·m;

[0088] Stiff type: overhang wave number ≤ 4, bending stiffness ≥ 120 μN·m;

[0089] (II) Continuously select bending stiffness values ​​from the corresponding bending stiffness range, and combine them with the values ​​of the fabric's constant force elongation, shear stiffness, and areal density to simulate the fabric drape test until the deviation between the simulated drape coefficient and the measured drape coefficient is less than 5%. The last selected bending stiffness value is the desired bending stiffness value of the fabric. Among them, the bending stiffness values ​​selected from the corresponding bending stiffness range are arranged in an arithmetic progression with a tolerance of m in order of priority. The minimum value of the arithmetic progression is the lower limit of the bending stiffness range. When the bending stiffness is ≥120μN·m, m=10. In other cases, m=(upper limit of the bending stiffness range - lower limit of the bending stiffness range)×10%. The fabric drape test simulation is carried out in the CAD system according to the method specified in GB / T23329-2009 standard.

[0090] The 3D clothing simulation method involves determining the clothing pattern (completed using a CAD system), the seam definition (completed using a CAD system), and the fabric's mechanical parameters, and then performing clothing simulation in CAD. The fabric's mechanical parameters are obtained using the method described above for obtaining fabric mechanical parameters in 3D clothing CAD. The fabric drape simulation and skirt simulation verification used in this invention's method are both completed using the Modaris 3D Fit 3D CAD system from Lectra, France. Therefore, this invention's method is more suitable for clothing simulations performed using this system.

[0091] This invention selected four typical fabrics with different drape properties for drape testing and simulation. The fabric specifications are shown in Table 6, and the drape test results are as follows: Figure 9 , 11 As shown in Figures 13 and 15, the suspension simulation results are as follows: Figure 10 , 12 As shown in Figures 14 and 16, its mechanical parameters are obtained as shown in Table 7.

[0092] Because of their large hem, the flared skirt's drape is most affected by the fabric's mechanical properties, and it's often used to verify the accuracy of garment simulation. Four identical flared skirts were made from the four fabrics mentioned above, as shown in the sample. Figure 17 As shown, the result is as follows Figure 18 , 20 The actual skirts shown in Figures 22 and 24 were obtained through 3D garment simulation based on the fabric's mechanical parameters. Figure 19 , 21 The virtual dresses shown in Figures 23 and 25, and the front and side views of the actual dress and the virtual dress. Figure 3 Extracting the width from the height, as shown below. Figures 26-29 As shown in Table 8, the difference in width between the two corresponding widths is less than 5%, which proves that the method of the present invention can achieve accurate simulation of clothing.

[0093] Table 6 Specifications of Four Fabrics

[0094]

[0095] Table 7 Mechanical parameters of four fabrics

[0096]

[0097] Table 8 Comparison of width differences between real skirts and simulated skirts

[0098]

Claims

1. A method for obtaining fabric mechanical parameters in 3D clothing CAD, characterized in that, The fabric is a woven fabric, and the fabric's mechanical parameters are its elongation at constant force, shear stiffness, areal density, and bending stiffness. The value of the constant force elongation of the fabric is any value within the interval [a,b], where a and b are the minimum and maximum values ​​of the elongation when the tensile stress is 500cN / cm, respectively, for more than 312 kinds of woven fabrics with different fiber materials and structures collected through literature retrieval. The shear stiffness of the fabric is any value within the interval [c,d], where c and d are the minimum and maximum values ​​of the shear stiffness measured by the KES-FB Kawabata style instrument for more than 312 kinds of woven fabrics with different fiber materials and structures collected through literature retrieval. The fabric's areal density is obtained through actual measurement; The steps to obtain the bending stiffness value of the fabric are as follows: (1) Conduct actual measurements of fabric drape to obtain the drape wave number formed by drape, and determine the corresponding range of bending stiffness values ​​based on the drape wave number. The corresponding relationships between the suspension wave number and the range of bending stiffness values ​​are as follows: suspension wave number ≤ 4, bending stiffness ≥ 120 μN·m; suspension wave number = 5, 60 μN·m ≤ bending stiffness < 120 μN·m; suspension wave number = 6, 25 μN·m ≤ bending stiffness < 60 μN·m; suspension wave number = 7, 10 μN·m ≤ bending stiffness < 25 μN·m; suspension wave number = 8, 4 μN·m ≤ bending stiffness < 10 μN·m. (2) Continuously select bending stiffness values ​​from the corresponding bending stiffness range, and combine the values ​​of the constant force elongation of the fabric, the values ​​of the shear stiffness of the fabric and the values ​​of the areal density of the fabric to simulate the fabric drape test until the deviation between the simulated drape coefficient and the measured drape coefficient is less than 5%. The last selected bending stiffness value is the bending stiffness value of the fabric to be obtained.

2. The method for obtaining fabric mechanical parameters in three-dimensional clothing CAD according to claim 1, characterized in that, In step (2), the bending stiffness values ​​selected from the corresponding bending stiffness range are arranged in order as an arithmetic progression with a tolerance of m. The minimum value of the arithmetic progression is the lower limit of the bending stiffness range. When the bending stiffness is ≥120μN·m, m=10. In other cases, m=(upper limit of the bending stiffness range - lower limit of the bending stiffness range)×10%.

3. The method for obtaining fabric mechanical parameters in three-dimensional clothing CAD according to claim 1, characterized in that, In step (2), the fabric drape test simulation is carried out in the CAD system according to the method specified in GB / T23329-2009 standard. 4.3D garment simulation method, which involves determining the garment pattern, seam definition, and fabric mechanical parameters before performing garment simulation in CAD, characterized by: The mechanical parameters of the fabric are obtained using the method for obtaining fabric mechanical parameters in three-dimensional garment CAD as described in any one of claims 1 to 3.

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