Textile Hand: Comparison of Two Evaluation Methods

Transcription

1 ISSN MATERIALS SCIENCE (MEDŽIAGOTYRA). Vol. 11, No Textile Hand: Comparison of Two Evaluation Methods Diana GRINEVIČIŪTĖ, Virginija DAUKANTIENĖ, Matas GUTAUSKAS Faculty of Design and Technologies, Kaunas University of Technology, Studentų 56, LT Kaunas, Lithuania Received 26 August 24; accepted 3 December 24 The article presents new test results concerning objective and subjective hand evaluation of 25 textile fabrics (woven and knitted). Textile hand was assessed subjectively by hand-picked judges panel, which in the way of direct survey assessed the fabrics in respect to 1 properties (smoothness, softness, thickness, roughness, weight, hardness, elasticity, stiffness, warmth and pleasing to handle) suitable to characterize the fabric hand. Textile hand was evaluated objectively using KTU-Griff-Tester on the basis of 5 determined parameters. Comparative analysis was made between the results obtained by judges survey and the parameters determined experimentally by using the methods of mathematical statistics. The level of the judges agreement according to each fabric property was evaluated on the basis of Kendall s concordance coefficient. Correlation between the assessment of the separate judge and the assessment of the total judges was determined on the basis of Spearman s rank correlation coefficient. Experimental data were estimated similarly as in the case of subjectively obtained results. The obtained dependencies between the subjectively and objectively determined parameters, suitable for the textile hand characterization, are not linear therefore the correlation between the subjective and objective methods is tenuous and coincidental. Keywords: textile, mechanical properties, hand, evaluation methods. INTRODUCTION Traditionally, scientists working in the area of textile fabric engineering evaluate textile hand subjectively. On the basis of judges knowledge, experience and senses a priori trial models are constructed only for the quantitative evaluation of textile hand. This situation occurred in default of one opinion and simple reliable direct method suitable to evaluate textile hand. Textile hand usually was evaluated on the basis of separate values or the sum of the parameters of simply understandable fabric properties. The scientists, who earlier investigated textile hand, were stating that fabric properties mostly influencing textile hand are: fabric smoothness (28 %), softness (22 %), stiffness (8 %), roughness (7 %), thickness (5 %) and weight (5 %). Such fabric properties as warmth, hardness, elasticity, nap, creasing propensity, drape and 6 7 other properties less influencing the textile hand enter the residual part of 25 % [1]. Nowadays, the parameters of these properties are determined objectively using two wellknown fabric testing systems KES and FAST [2 4]. The research works presented in various countries over past years show that one of the most perspective methods for textile hand evaluation is the extraction of a disk shaped specimen through a ring shaped or a conic shaped hole [5 9]. Experiments are carried out with special devices named griff-tester [1 14]. The comparison of the results obtained by the survey of judge panels and the ones determined instrumentally with griff-tester hasn t been done yet. The comparative analysis of the results, obtained by different methods, is purposeful to start new investigations or to demonstrate the reliability of a new testing method. Supposedly, having the priori results together with the experimental ones, the number of experiments can be decreased. Corresponding author. Tel.: ; fax.: address: Diana.Grinevičiute@stud.ktu.lt (D. Grinevičiūtė) The aim of this research was to organize a special panel of judges having the skills and excellence to identify the fabrics in touch; to pick the set of fabric properties characterizing fabric hand in the best way; to investigate the most variety of textile fabrics; to analyze objects of investigations using the rank correlation method; to compare the results of this analysis with the results determined experimentally by using KTU-Griff-Tester [12, 13]. EXPERIMENTAL The judge panel was formed of 21 working persons. All of them having sight disorders worked in one specialized enterprise in Kaunas. Their job was coherent with the senses of touch and they were reading Braille well. Thus, fabrics were characterized only on the basis of the hand parameters used by the earlier researchers as the constituents of fabric hand excluding the influence of the visual impression. At the first stage of the investigations 1 hand properties (smoothness, softness, thickness, roughness, weight, hardness, elasticity, stiffness, warmth, pleasing to handle) were evaluated and at the second stage the 6 ones (smoothness, softness, stiffness, roughness, thickness and weight). The sets of the equal size specimens (1 cm 2 ) cut from the investigated fabrics were given to each judge, and each of them was asked to range specimens in accordance to its properties from the best to the worst. The expertise was carried out talking in the judge panel indefinitely in time. Each fabric property was characterized verbally before the subjective evaluation. After this the judges had to range the fabrics according to their smoothness, softness, thickness and etc. The set of the specimens cut from 25 different fabrics (Table 1) was divided into 3 s (13 5 7) according to the fabric type (suiting woven outwear woven knitted) to facilitate the evaluation of fabrics for the judges and to increase the reliability of the data. 57

2 Table 1. Fabric characteristics Woven fabric Fabric symbol Composition Density, cm 1 Weave Thickness (δ), Area density, mm g/m 2 A1 PA 38/27 (warp/weft) Plain A2 PES, cotton 34/17 (warp/weft) Plain A3 PA, acetate 49/23 (warp/weft) Combined A4 PA 6/36 (warp/weft) Twill A5 PES 22/19 (warp/weft) Compound double A6 PES 34/22 (warp/weft) Combined A7 Acetate 25/2 (warp/weft) Combined A8 Acetate 25/23 (warp/weft) Warp satin A9 PES, cotton 29/17 (warp/weft) Plain A1 Cotton 49/23 (warp/weft) Plain A11 Viscose 39/28 (warp/weft) Combined.3 77 A12 PA, acetate 46/22 (warp/weft) Plain.1 6 A13 Wool 18/15 (warp/weft) Twill G1 Wool, cotton, PES 16/14 (warp/weft) Twill G2 Wool, PES 14/13 (warp/weft) Twill G3 Wool, cotton 14/14 (warp/weft) Twill G4 Wool, cotton 16/14 (warp/weft) Twill Suiting Outwear Knitted fabric G5 Wool, cotton 17/16 (warp/weft) Plain T1 PA 1/17 (wale/course) Welf-knitted T2 PES 18/16 (wale/course) Rib pattern (1+1) T3 PA, acetate 19/13 (wale/course) Rib pattern (1+1) T4 PES, cotton 21/13 (wale/course) Rib pattern (2+2) T5 PA 23/16 (wale/course) Fancy pattern T6 Cotton 1/16 (wale/course) Terry fabric T7 PA 16/21 (wale/course) Fancy pattern The results obtained by the survey of the judges were estimated statistically. The level of the judges agreement according to each fabric property was evaluated on the basis of Kendall s coefficient of concordance W and the level of its significance χ 2. Correlation between the assessment of the separate judge and the assessment of the total judges panel was determined on the basis of Spearman s coefficients of rank correlation ρ [15]. Instrumental evaluation of the textile fabric properties was made using KTU-Griff-Tester (Fig. 1) according to earlier designed method [12, 16]. Fig. 1. Principal scheme of textile hand evaluation in pulling process The circular specimen with the radius R = 56.5 mm was pulled through the central hole the radius r. Radius of a circular hole of the lower plate r and the distance between the limiting plates h were chosen in respect to the thickness of tested fabric δ and taking into account the conditions of specimen jamming between the limiting plates. During testing the typical pulling curve H-P (extraction height pulling force) was registered and the 4 parameters: maximal pulling force P max, the tangent of the slope angle of H-P curve initial part tgα, the pulling work A and maximal deformation H max were determined from it. Specimen thickness δ that influenced the values of the parameters r and h was measured under different loads, the ratio 1 : 5. The change of measured fabric thickness was marked δ and together with above mentioned four parameters P max, tgα, A and H max had formed the complex hand rate Q. The value of complex hand rate Q was determined as the area of a polar chart. Five initial parameters (P max, tgα, A, H max, δ) and the sixth complex (Q) characterizing fabric hand, expressed by the specific measures and ranks, were compared to the corresponding results obtained by the survey of the judges. The sample size (the number of the specimens) was chosen so that the error didn t exceed 1 %. RESULTS AND DISCUSSION The initial results concerning the properties of the investigated fabrics obtained by the survey of the judges are presented in Table 2 and the parameters of the statistic estimation are presented in Table 3. The initial results have shown that the level of the judge agreement during the estimation of 1 fabric properties was sufficiently controversial. Analyzing the assessments of fabric softness, smoothness, thickness, weight and roughness it can be seen that the level of the judges agreement was high enough but such fabric properties as hardness, 58

3 elasticity, stiffness, warmth and pleasure to handle were assessed differently by different judges. The reason for the noticed difference could be the insufficient judge understanding of fabric properties. This reason was taken into account, and later only 6 properties were evaluated during the fabric subjective testing. The set of these properties is reliable to characterize textile hand as the influence of these properties combine 75 % of the complex hand parameter [1]. Comparing the test results of three different fabric s (Table 2) it was noticed that properties of outwear fabrics were assessed more similarly (W =.954) compared to the assessments assigned to the properties of suiting fabrics (W =.894). Supposedly, these peculiarities occurred because of the differences between the fabric thickness and the size of fabric s. The analysis of the results obtained by the judge survey (Table 3) has shown that fabric properties: smoothness and softness can be used as the most significant in the evaluation of fabric hand because coefficient ρ often obtained the reliable values of correlation (ρ >.8). The same results were obtained in earlier works by other researchers [1]. Analyzing the results of different fabric s according to the frequency of good values of the coefficient ρ (Table 3), it can be stated that the judges most similarly evaluated the properties of outwear fabrics. The agreement between the judges during the evaluation of knitted fabrics properties was lowest. The main reason of the lowest agreement between judges, evaluating a small (7) of knitted fabrics compared to a better agreement evaluating larger (13) of suiting fabrics, could be the specific deformation and surface properties of knitted fabrics. Table 2. The initial results obtained after the judges assessment expressed in ranks Instrumentally determined parameters, characterizing the behavior of 25 different fabrics extraction through the rounded hole, are presented in Table 4. The analysis of presented results has shown that differences between the same parameters in each of three fabric s are significant. The differences between the maximum and minimum values of the parameters are as follows: P max times; tgα times; A times; δ times; H max times and Q times. The intensity of changes of parameters shows that the complex rate Q is more evident if compared to the other parameters. According to the ranks, different parameters ranked differently. So, the search of one quantitative parameter can be done using two methods. Using the first method the ranks of 5 parameters can be summed and one total parameter, that indicates fabric position in the range in respect to the other fabrics, can be obtained. It must be noticed that such a total parameter could be used only to compare fabrics among themselves. The differences between the results obtained subjectively by the survey of the judges and the total parameter would be very slight. This was observed after the comparative analysis of the correlation between the results of subjective and objective evaluation (Table 5). The second method is based on the plotting of the circular chart, which contains 5 measured parameters, the sum of which compose one quantitative expression (complex rate Q), characterizing fabric hand. This complex rate is more reliable (if compared to the total parameter, determined using the ranks method) because it is based on the real measured values of the initial parameters, which arrange according to ranks not as the regular proportions, Fabric symbol Smoothness Softness Thickness Weight Stiffness Roughness Σ S A A A A A A A A A A A A A G G G G G T T T T T T T Σ rank sum of 6 properties; S the rank of Σ. 59

4 Table 3. The parameters of Spearman s rank correlation during the subjective evaluation of fabric properties Woven fabric Fabric type Suiting Outwear Knitted fabric Property Smoothness Softness Thickness Weight Stiffness Roughness ρ W χ 2 Smoothness Softness Thickness Weight Stiffness Roughness Smoothness Softness Thickness Weight Stiffness Roughness Smoothness Softness Thickness Weight Stiffness Roughness ρ the coefficient of Spearman s rank correlation; W the coefficient of Kendall concordance; χ 2 the level of Kendall s coefficient significance. Table 4. The results of the experimental evaluation of fabric properties Parameter changes, times Fabric symbol P max tgα A δ H max Q Rank sum N R --- R Ncm R % R mm R cm 2 R Σ R A * 4* A * 6* A * 8* A * 3* A * 1* A * 5* A * 13* A * 12* A * 7* A * 11* A * 2* A * 1* A * 9* G * 4* G * 2* G * 3* G * 1* G * 5* T T T T T T T Woven suiting Fabric Woven outwear Knitted R rank; * the parameters, not included in the complex rate Q. 6

5 but are expressed by complex mathematical functions (Fig. 2 and Fig. 3). The position of the parameters: P max, tgα, A, δ and H max in respect to the axes of the circular chart (clockwise or counterclockwise) must be the same during the calculation of the complex rate Q. The first three parameters (P max, tgα and A) indicate the strength of the fabric and the last two ( δ and H max ) the fabric deformation. During the calculation of the complex rate of a very stiff woven fabric the parameter H max can be excluded because of the dependence of its value on the parameters of the specimen R and the device r. When R = 56.5 mm and r = 1. mm, the value of the parameter H max is equal to about 52. mm for not extensible fabrics. It means that some errors, which can occur during the measurement of parameter H max, can make the influence on the parameter Q. The analysis of fabric hand on the basis of experimentally determined parameters has shown (Table 4) that the relationships between numerical values of the measured parameters (P max, tgα, A, H max ) and the ranks of them are not linear (except the parameter δ) (Fig. 2 and Fig. 3). According to the highest values of the correlation coefficient the relationships between the numerical values of the parameters and their ranks were described by the different mathematical equations: P max, tgα, A and Q y = a + bx 3, δ y = a + bx, and H max y = a + b / x. It must be noted that hand parameter Σ involving the sum of ranks of 4 (woven fabric) and 5 (knitted fabric) parameters in the case of the knitted fabrics was almost equal to the complex rate Q determined as the sum of the same parameters being in the circular chart (Table 4). In the case of woven fabrics the differences between the parameters Σ and Q are more evident though in the some cases they were equal. The comparative analysis of the results determined by the judge survey (Table 2 and Table 3) and experimentally determined results (Table 4) shows the significant differences between these two methods of hand evaluation. For example, in the case of knitted fabrics (Table 2) evaluation of the judges, the fabrics were ranged in such an order: T1 T3 T5 T2 T6 T7 T4, and in accordance with the instrumentally determined parameters Q or Σ (Table 4) in such an order: T3 T6 T1 T4 T5 T7 T2. After taking a glance at these ranges of fabrics it can be seen, that they are not similar. Hereby it can be stated that the subjective hand assessment did not demonstrate the reliable correlation with the objective hand evaluation. The exhaustive analysis of the subjective hand assessment and the objective hand evaluation has shown that hand parameter Σ (Table 2) faintly correlate with the hand parameter Q and the coefficient of correlation in the different fabric s is only.4267,.218, Thus, it can be stated that the correlation between the subjective hand assessment and objective hand evaluation did not exist in neither of the tested fabric s. The comparative analysis between the results of the earlier survey of the judges and the experimentally determined hand parameters [17] has also shown, that the separate criterions of the judge survey faintly correlate Table 5. The correlation between the results of subjective assessment and objective evaluation of textile hand Woven fabric Fabric Suiting Outwear Knitted fabric The criterion of the judge survey The criterion of instrumental method P max tgα A δ Q Smoothness Softness Thickness Weight Stiffness Roughness Rate involving the sum of parameters of the 6 above listed properties Smoothness Softness Thickness Weight Stiffness Roughness Rate involving the sum of parameters of the 6 above listed properties Smoothness Softness Thickness Weight Stiffness Roughness Rate involving the sum of parameters of the 6 above listed properties

6 Pmax, N a Pmax= R 3 r 2 =.9192 δ, % δ = R r 2 =.9483 a tgα b tgα= r 3 r 2 =.982 Hmax, mm Hmax= /R r 2 =.9539 b c Fig. 3. The dependencies between the hand parameters characterizing the fabric deformation and the ranks A, Ncm Q, cm d A= R 3 r 2 = Q= R 3 r 2 = Fig. 2. The dependencies between the main parameters of the hand experimental evaluation and the ranks with the experimentally determined parameters. This notwithstanding, the correlation between the sum of the 5 parameters determined by the judge survey and the experimentally determined parameters was stronger. It means that the chosen set of parameters for the judges survey is suitable to characterize textile hand determined by KTU-Griff-Tester. This is understandable because the one fabric property evaluated by handling the fabric is not completely suitable to characterize the complex mechanical parameter, as it is the textile hand. Other researchers have already written about this [1]. For this reason the sum of the properties more or less would be suitable for the evaluation of textile hand. When after six months the survey of the same judges with the same fabric specimens was repeated, it was noticed that the results of hand evaluation changed if compared to the earlier obtained results. After the first survey of the judges [17] the correlation between fabric subjective smoothness and instrumentally determined hand parameters was sufficiently high. But after the second one the correlations of the results of subjective assessment and instrumental measurements were low (Table 5). Although the fabric hand is concerned with the senses of touch, and the judges were the blind with clearly expressed skills of touch, still the subjective assessment results in both cases differed not only among themselves but they also differed from instrumentally measured ones. So, the problem of judges choosing and their training must be taken into account during the subjective assessment of fabric hand. According to the results obtained by KTU-Griff-Tester, evident differences between determined parameters of fabrics were obtained (except the parameter H max ). It shows that this instrumental device is sensitive, technically simple and sufficiently reliable for the characterization of the main fabric properties influencing the relative evaluation of the fabric hand, i.e. it enables not only to range the tested objects, but also to determine the differences between the fabrics. But in the case when the irrelative value of a fabric hand needs to be determined, KTU-Griff- Tester must be calibrated in respect to the specimen of the standard fabric. 62

7 CONCLUSIONS There is no proper correlation between textile hand evaluation methods subjective assessment and objective evaluation (based on the pulling of a rounded specimen through the central hole). The assessment of the fabric hand by the judge survey is not reliable, but it can be used for the tentative comparison of the different fabrics or methods. KTU-Griff-Tester is a simple, reliable instrumental device suitable to obtain the quantitative information about the fabric mechanical properties that characterize the fabric hand. The complex rate Q for the hand evaluation is presented. It characterizes the fabric properties that are concerned with the fabric smoothness, softness, roughness, thickness and flexibility. The irrelative hand value for the various fabrics can be determined after the calibration of KTU-Griff-Tester in respect to the specimen of the standard fabric. REFERENCES 1. Bishop, D. P. Fabrics: Sensory and Mechanical Properties Journal of the Textile Institute ISSN (3) 1996: pp Ganssauge, D., Lehmann, K. H., Angenadel, A. Wie Beeinflussen Typische Gewebemerkmale den Griff Einer Ware Melliand Textilberichte : s Frydrych, I. Objective Evaluation of Handle Textile Rewiew (Prz. Wlok.) : pp (in Polish). 4. Bereck, A., Dillbohner, S., Mitze, H., Weber, B., Riegel, D., Riegel, M., Pieper, J. M., Brakelmann, A. Eine neue, einfache Methode zur Messung der Weichnen textiler Flächengebilde. Teil 2. Einfluss der Ausrüstung auf die Gewebeweichheit Textilveredlung 32 (9/1) 1997: s Ellis, B. C., Garnsworthy, R. K. A Review of Techniques for the Assessment of Hand Textile Research Journal 4 198: pp Howorth, W. S., Oliver, P. H. The Application of Multiple Factor Analysis to the Assessment of fabric Handle Journal of the Textile Institute ISSN : pp. T54 T Grover, G., Sultan, M. A., Spivak, S. M. A Screening Technique for Fabric Handle Journal of the Textile Institute ISSN (23) 1993: pp Kim, O. J., Slaten, B. L. Objective Evaluation of Fabric Hand Textile Research Journal 69 (1) 1999: pp Henrich, L., Seidel, A., Rieder, O. Griffprüfung an Maschenwaren Maschen-Industrie : s Seidel, A. Griffbewertung von Strumpfwaren mit dem JTV Griff Tester Melliand Textilberichte ISSN : s Daukantienė, V., Gutauskas, M. Textile Hand: An Analysis of Knitted Fabric Behavior Materials Science (Medžiagotyra) ISSN (3) 22: pp Strazdienė, E., Papreckienė, L., Gutauskas, M. New Method for the Objective Evaluation of Technical Textile Behavior 6 th Dresden Textile Conference, 22 CD ROM Page 1 8 of 8, Strazdienė, E., Daukantienė, V., Gutauskas, M. Bagging of Thin Polymer Materials: Geometry, Resistance and Application Materials Science (Medžiagotyra) ISSN (3) 23: pp Daukantienė, V., Papreckienė, L., Gutauskas, M. Simulation and Application of Pulling Textile Fabric through a Central Hole Fibres and Textiles in Eastern Europe ISSN (2) 23: pp Kendall, M. G. Rank Correlation Methods. Moscow, Statistika, 1975: 216 p. (in Russian). 16. Martišiūtė, G., Gutauskas, M. A New Approach to Evaluation of Textile Fabric Handle Materials Science (Medžiagotyra) ISSN (3) 21: pp Grinevičiūtė, D., Gutauskas, M. An Introduction to Motivation of Textile Handle Assessment Method Gaminių technologijos ir dizainas (Design and Technology of Consumables), Kaunas: Technologija, 23: pp (in Lithuanian). 63