Research On Fabric Crease Recovery Performance Based On Image Technology

Crease or wrinkle is the irreversible deformation of fabric caused by rubbing and extruding forces. Crease recovery is a dynamic process in which a folded fabric specimen continues to be unfolded by itself, and is often evaluated by angle changes between two folded fabric wings. However, the current standard methods and the measurement devices designed based on the standard methods can merely obtain the static angle at specific time, can not reflect the whole recovery process. In addition, the existing methods need tedious manual operations, are susceptible to human errors, and have poor repeatability.In allusion to the problems mentioned above, a fabric crease recovery test method based on image technology is proposed in this paper. The dynamic indexes for evaluating crease recovery property can be extracted from the recovery angle curve changed over time. The dynamic indexes were used to inspect anisotropy in the crease recovery property to realize the uniformization characterization for the fabric performance. And a viscoelasticity modeling of a creased fabric was presented to analyze the physical meaning of the dynamic indexes. The research contents and conclusions are as follows:(1) With the image technology, Hough transform and image registration methods are proposed to automatically measure the fabric crease recovery angle. In the Hough transform method, binary processing is implemented at first. Then the medial axis of the free wing is extracted from the binary image by thinning algorithm. Finally, the crease recovery angle of the specimen is calculated by Hough transform. In the image registration method, two consecutive frames in the same image sequence are used to calculate the angle difference between them. First, the previous frame is rotated around the crease. Then, the mutual information between a rotated frame and the next frame is measured. The maximum normalized mutual information can be worked out when the positions of the free wing in both the rotated frame and the other frame achieve a perfect match. The results of different methods show that the proposed two methods have a higher consistency to the manual method when the free wing is similar to a straight line, while the recovery angle measured by image registration method is more accurate when the free wing bends.(2) The dynamic fabric crease recovery system was built to evaluate the property. With the application of horizontal pneumatic presser device and video sequence acquisition device, the fixed wing of the specimen keeps in the same position in the whole testing process. Thus, it makes it possible to depict the entire recovery angles with the change of time. The fabrics provided by Cotton Incorporated were used to compare the test results of Shirley crease recovery tester and the dynamic crease recovery system. It is found that the recovery angles of the two tester at the 5th min of the recovery period are similar to each other. It is proved that the pressure of 5 N and the pressure time of 5 min are the appropriate parameters, and the standard deviation of the test results of recovery angle is satisfied the requirement of current standards. The designed system can achieve the function of the existing testers. What is more, the system is easy to operate, highly automated and stable. It can obtain the dynamic recovery trend, which could lay the foundation for the research of crease recovery property.(3) The dynamic evaluation indexes, including initial recovery rate, instant time, instant recovery angle, stable time, stable recovery angle and recovery ratio, can be extracted from the curve of recovery angle with the increase of time to quantify the fabric crease recovery property. The dynamic indexes were used to evaluate the recovery process of cotton fabrics. The result shows that the initial recovery rate was about 500 °/s. In the repeated creasing test, the indexes decreased rapidly first and then became stable with the increase of the number of the testing cycles. The results of the wool fabrics indicate that the initial recovery rate was about 1300 °/s. Compared with stable recovery angle, the recovery angle of wool fabrics recovered over 80% in the instant period. The crease recovery property of wool fabrics was better than that of cotton fabrics. The results of repeated creasing test of wool fabrics were similar to those of cotton fabrics.(4) The tendency of each dynamic crease recovery index with the change of orientation angle were studied by the test results of specimens with different sampling directions to propose the uniformization characterization for the assessment of fabric crease recovery property. Orientation angle is the angle measured counterclockwise from the direction of x axis to the crease direction. The experiment result reveals that the anisotropy of crease recovery does exist, the crease recovery angles of the specimens whose crease parallels to warp and weft direction(i.e. 0° and 90° orientation angle) have low values than those of the other orientation angles. To the fabrics whose yarn sizes of warp and weft are similar with each other, the diagonal direction(45°) was proven to be the optimal orientation angle for a plain fabric, while the two orthogonal directions, i.e. the twill direction and its perpendicular direction, were found to be more relevant for a twill fabric.(5) A modeling of a creased fabric is presented based on viscoelastic theory. It is used to illuminate that crease is formed by bending deformation and theoretically explain that the physical interpretation of initial recovery rate(one of the dynamic indexes) and the finial recovery angle(the recovery angle when the position of a free wing do not change). Then, comparing the test results of bending parameters measured by KES-FB2 Pure Bending Tester and crease recovery parameters obtained by dynamic system, it is demonstrated that the bending rigidity generally decrease as exponential at the beginning and then almost remain unchanged with the increase in initial recovery rate. And it verifies that the impact of bending property on crease recovery property.The dynamic fabric crease recovery system proposed in this paper realizes the integrated characterization of the movement of crease recovery process in the entire period. This system provides a high automation and accurate measurement approach for the deep study of fabric property. The dynamic indexes obtained from the system are conductive to master the influence factors and deformation mechanism of crease recovery property, and have the push function to the improvement of fabric wearability.