Method for evaluating crease recovery of fabrics based on power function equation

Abstract

A method for evaluating crease recovery of fabrics based on power function equation. The steps are: (1) place the sample in the sample placement area; (2) pressure the overlapping part of the sample; (3) let the free part of the sample automatically restore and record the video image of the sample crease recovery by camera; (4) process the video image of the fabric crease recovery and calculating the recovery angle of each frame of video image; (5) repeat steps 1 to 4 to measure N samples of the same fabric; (6) obtain the dynamic process of fabric crease recovery angle change. This can reveal which type of fabric has better recovery property, when the existing methods have the similar results of recovery angle.

Claims

1. A method for evaluating crease recovery of fabrics based on power function equation wherein the following steps are comprised: step 1: pressure and time are set in the numerical control (NC) interface system; the sample is placed in the sample placement area; one part of the sample is fixed in the sample placement area; the other part of the sample bends and overlaps the fixed part; step 2: the pressurized cylinder controls the pressing block to push towards the sample placement area and pressurizes the overlapping part of the sample; step 3: when the pressure time set by the NC interface system is reached, the pressurized cylinder controls the movement of the pressing block away from the sample placement area, so that the free part of the sample can automatically recover, and the camera records the video image of the sample crease recovery; step 4: process the video image of fabric crease recovery and calculate the recovery angle of each frame of video image; step 5: repeat steps 1 to 4 to measure N samples of the same fabric and find the average recovery angle of N samples at the same recovery time; step 6: the dynamic process of fabric crease recovery angle change is acquired by image processing algorithm; the data of recovery angle in the recovery process are fitted into power function equation by non-linear curve fitting method:
f(t)=at.sup.b  (1) in the equation, t stands for time and f(t) represents recovery angle; the fitting function of the non-linear curve is shown in equation and the initial values of a and b are set to be 10 and 0.1 respectively,
min.sub.t∥f(t)−m.sub.t∥.sub.2.sup.2=min.sub.tΣ.sub.i(f(i)−m.sub.l).sup.2  (2) coefficients a and b in equation are obtained according to equation so that the minimum binary expression of equation is established; step 7: the first and second coefficients for evaluating the crease recovery properties of fabrics are extracted from equation; wherein, the first coefficient is a in equation is equal to the angle value of fabric crease recovery at the first unit time after the beginning of recovery, and the second coefficient is b in equation is equal to the ratio of instantaneous recovery speed at the end of the first unit time of recovery stage to the angle value of fabric crease recovery at the first unit time, and is defined as recovery index; the coefficient K is constructed by the values of coefficient a and b, and the crease recovery property of the fabric is evaluated thereby; $\begin{array}{cc}K=\frac{a}{b}& \left(3\right)\end{array}$ step 8, the average value K of sub-indexes K.sub.1, K.sub.2, K.sub.3 and K.sub.4 corresponding to the four folding modes of fabric samples are obtained; as a comprehensive evaluation index, it reflects the crease recovery property of the whole fabric, which is called the comprehensive index of fabric crease recovery.

2. The method for evaluating crease recovery of fabrics based on power function equation according to claim 1, wherein in step 8, the four folding modes include warp face-to-face folded, warp back-to-back folded, weft face-to-face folded and weft back-to-back folded.

3. The method for evaluating crease recovery of fabrics based on power function equation according to claim 1, a fabric crease recovery device is used in the method; the fabric crease recovery device comprises a numerical control interface system, a camera, a sample placement area, a pressing block and a pressurized cylinder; the NC interface system is connected with the pressurized cylinder and the camera to realize the precise adjustment of the pressurized time and pressure of the pressurized cylinder; the pressurized cylinder is connected with the pressing block, the pressing block is placed on the upper surface of the sample placement area, the sample placement area realizes the function of fixing the sample, and the camera is positioned right above the sample placement area; the camera collects video images of the sample crease recovery process and transmits them to the NC interface system.

Description

DESCRIPTION OF DRAWINGS

(1) The sole FIGURE is a schematic diagram of the present invention.

(2) In the FIGURE, 1 NC interface system; 2 camera; 3 sample placement areas; 4 pressing block; 5 pressurized cylinder.

DETAILED DESCRIPTION

(3) The present invention is described combining with the technical solution and the FIGURE.

(4) As shown in the FIGURE, the present invention presents a method for evaluating crease recovery of fabrics based on power function equation. The steps are as follows:

(5) Step 1: Pressure and time are set in the NC interface system. The sample is placed in the sample placement area 3 to form a bending and overlapping state. One part of the sample is fixed in the sample placement area 3. Open the tester.

(6) Step 2: Pressurized cylinder 5 controls the pressing block 4 to push toward sample placement area 3, and then pressurizes the sample.

(7) Step 3: When the pressure time set by the NC interface system is reached, the pressurized cylinder 5 controls the movement of the pressing block 4 away from the sample placement area 3, so that the free part of the sample can automatically recover. At the same time, the camera 2 records the video image of the sample crease recovery.

(8) Step 4: The computer processes the video image of fabric crease recovery, calculates the recovery angle of each video image frame, and realizes the full characterization of the change of fabric crease recovery angle.

(9) Step 5: The dynamic process of fabric crease recovery angle is obtained by image processing algorithm, and the data of fabric crease recovery angle is fitted to power function equation.
f(t)=at.sup.b  (2)

(10) In the equation, t is time, f(t) is the recovery angle.

(11) Step 6: Extract the index for evaluating fabric crease recovery performance from Equation (1). Wherein, index a represents the initial recovery angular displacement (the larger the a is, the faster the initial recovery is; the smaller the a is, the slower the initial recovery is). Index b represents the recovery exponent (the larger the b is, the longer the recovery process is; the smaller the b is, the shorter the recovery process is).

(12) Step 7: Calculate the sub-item index K of fabric crease recovery of each folding mode by coefficient a and b. The sub-item index of fabric crease recovery for four folding modes, i.e. warp face-to-face folded, warp back-to-back folded, weft face-to-face folded and weft back-to-back folded, can be used to find the average number and obtain the comprehensive index of fabric crease recovery.

(13) Ten kinds of fabrics were tested, and the fabric specifications are listed in Table 1.

(14) TABLE-US-00001 TABLE 1 Fabric parameters Yarn Yarn density/(numbers .Math. count/tex (10 cm ) .sup.−1) Fabric Material Weave Warp Weft Warp Weft A 100% Plain 14.6 15.8 555 568 Cotton B 100% 3/1     29.2 64.8 465 200 Cotton Twill

(15) The above fabrics were treated by four post-finishing processes as shown in Table 2. Including the fabric without post-finishing, there were totally 10 types of samples. The corresponding relationship between sample number and fabrics is shown in Table 3.

(16) TABLE-US-00002 TABLE 2 Post-finishing method No. Post-finishing method 1 Soft Finishing 2 6% Resin finishing (with softener) 3 12% Resin finishing (with softener) 4 18% Resin finishing (with softener)

(17) TABLE-US-00003 TABLE 3 Sample number Sample number Fabric type Post-finishing method 1# A No post-finishing 2# A Soft Finishing 3# A 6% Resin finishing (with softener) 4# A 12% Resin finishing (with softener) 5# A 18% Resin finishing (with softener) 6# B No post-finishing 7# B Soft Finishing 8# B 6% Resin finishing (with softener) 9# B 12% Resin finishing (with softener) 10#  B 18% Resin finishing (with softener)

(18) According to the method described above, the crease recovery properties of fabrics are tested and the results are listed in Table 4. Coefficient a and b are constants in the power function fitting equation of “time-average recovery angle”. R.sup.2 is the resolvable coefficient of goodness of fit. K is the sub-item index of fabric crease recovery, K is the composite index of fabric crease recovery. F.sub.t and F.sub.c are measured and calculated values at the 5th minute of the recovery stage respectively. ΔF is the difference between F.sub.t and F.sub.c. F.sub.jw is the evaluation index of the existing standard method (The sum of warp and weft crease recovery angles).

(19) TABLE-US-00004 TABLE 4 Test results Sample Folding number mode a b R.sup.2 K K F.sub.t/° F.sub.c/° ΔF/° F.sub.jw/° 1# Warp 46.8 0.0740 0.976 632.1 689.3 70.7 71.4 0.7 149.0 face-to-face Warp 46.5 0.0755 0.972 616.1 70.7 71.5 0.9 back-to-back Weft 51.2 0.0699 0.983 732.3 75.4 76.3 0.9 face-to-face Weft 54.7 0.0704 0.986 776.5 81.1 81.7 0.6 back-to-back 2# Warp 51.7 0.0759 0.974 680.8 850.3 78.7 79.7 0.9 173.0 face-to-face Warp 62.0 0.0622 0.978 995.6 87.3 88.4 1.1 back-to-back Weft 62.3 0.0694 0.989 898.4 91.7 92.6 0.8 face-to-face Weft 59.4 0.0719 0.964 826.3 88.2 89.6 1.4 back-to-back 3# Warp 92.5 0.0539 0.957 1718.1 1649.4 124.7 125.8 1.2 240.1 face-to-face Warp 91.0 0.0566 0.953 1608.3 124.3 125.6 1.3 back-to-back Weft 88.4 0.0521 0.966 1697.9 118.0 119.0 1.1 face-to-face Weft 84.3 0.0536 0.962 1573.2 113.1 114.4 1.3 back-to-back 4# Warp 97.6 0.0499 0.931 1956.1 2097.5 128.2 129.7 1.5 258.8 face-to-face Warp 102.6 0.0457 0.952 2246.3 131.9 133.1 1.2 back-to-back Weft 98.4 0.0479 0.971 2054.8 128.3 129.4 1.1 face-to-face Weft 99.9 0.0469 0.945 2132.9 129.2 130.5 1.3 back-to-back 5# Warp 109.1 0.0419 0.953 2601.2 2811.4 137.6 138.6 1.0 276.6 face-to-face Warp 113.7 0.0389 0.916 2923.9 140.7 141.9 1.2 back-to-back Weft 111.4 0.0391 0.951 2847.4 138.2 139.2 1.0 face-to-face Weft 110.5 0.0385 0.942 2873.0 136.6 137.6 1.1 back-to-back 6# Warp 35.0 0.0698 0.963 502.2 805.4 51.4 52.2 0.7 148.5 face-to-face Warp 53.1 0.0658 0.980 807.3 76.5 77.3 0.8 back-to-back Weft 66.3 0.0622 0.963 1066.0 93.4 94.6 1.2 face-to-face Weft 53.6 0.0634 0.938 846.2 75.7 77.0 1.2 back-to-back 7# Warp 36.2 0.1016 0.982 356.3 916. 7 63.8 64.6 0.8 181.3 face-to-face Warp 70.2 0.0665 0.980 1054.4 101.6 102.6 1.0 back-to-back Weft 85.9 0.0575 0.913 1494.1 117.6 119.2 1.6 face-to-face Weft 53.9 0.0707 0.961 761.9 79.6 80.7 1.1 back-to-back 8# Warp 59.5 0.0762 0.947 780.7 1370.1 90.3 91.8 1.5 223.2 face-to-face Warp 89.9 0.0573 0.971 1568.7 123.3 124.6 1.3 back-to-back Weft 98.5 0.0516 0.970 1911.2 130.9 132.2 1.4 face-to-face Weft 73.1 0.0599 0.945 1219.9 101.8 102.9 1.1 back-to-back 9# Warp 84.8 0.0508 0.903 1669.3 1987.6 112.2 113.3 1.1 244.4 face-to-face Warp 99.3 0.0464 0.957 2140.1 128.0 129.3 1.3 back-to-back Weft 109.0 0.0420 0.961 2594.4 137.1 138.5 1.4 face-to-face Weft 83.2 0.0538 0.946 1546.5 111.4 113.0 1.6 back-to-back 10#  Warp 93.3 0.0424 0.915 2199.9 3019.0 117.4 118.8 1.4 273.2 face-to-face Warp 121.3 0.0367 0.939 3300.7 148.2 149.5 1.4 back-to-back Weft 121.8 0.0380 0.971 3204.4 150.2 151.2 1.0 face-to-face Weft 109.4 0.0325 0.947 3371.1 130.6 131.7 1.1 back-to-back

(20) From the data in Table 4, it can be concluded that:

(21) (1) R.sup.2 of the fitting equation is larger than 0.9, which shows that the “time-average recovery angle” equation has a high fitting accuracy.

(22) (2) The new evaluation index K shows a positive correlation with F.sub.jw (r=0.94), which indicates that the proposed K value is feasible to characterize the crease recovery property of fabrics.

(23) (3) The new evaluation index K is more effective in judging the crease recovery property of fabrics. For example, the F.sub.jw values of Sample 1 # and Sample 6 # are 149.0° and 148.5° respectively, which are close with each other. It is difficult to judge the crease recovery properties of these two fabrics according to the existing method. But the new indexes K are 689.3 and 805.4 respectively, it is easy to distinguish that the crease recovery properties of Sample 6 # are better than that of Sample 1 #. Similarly, for Sample 5 # and Sample 10 #, F.sub.jw is 276.6° and 273.2° respectively, while the new index K is 2811.4 and 3019.0 respectively. It is easy to distinguish that the crease recovery performance of Sample 10 # is better than that of Sample 5 #.