**2. Measurement of surface profiles**

Surface irregularity of planar textiles can be identified by contact and contact-less techniques. For **contact measurements** the height variation (as thickness meter) or measurement of force needed for tracking the blade on the textile surface is applied (Ajayi, 1992, 1994; Militký Bajzík, 2001, 2004). **Contacts less measurements** are usually based on the image analysis of fabric surfaces (Militký Bleša, 2008). The subjective assessment of the fabrics roughness can be investigated as well (Stockbridge H.C. et. al, 1957).

KES for hand evaluation (Kawabata 1980) contains measuring device for registration the surface height variation (SHV) trace. This device (shown in the fig. 1) is a part of system KES produced by company KATO Tech.

Fig. 1. Device for measurement of fabric surface characteristics

The main part of this device is contactor (see. fig. 2) in the form of wire having diameter 0.5 mm. The contact force 10 g is used.

Fig. 2. KES contactor for measuring of surface roughness

This contactor touches on the sample under the standardized conditions. The up and down displacement of this contactor caused by surface roughness is transduced to the electric

 Description of approach for contact-less evaluation of surface relief (macro roughness). This approach is based on the image analysis of especially prepared fabric images. The simulated "teeth" profiles with variable height and thickness is used for identification of all kind of roughness parameters capability. These parameters are applied for

Surface irregularity of planar textiles can be identified by contact and contact-less techniques. For **contact measurements** the height variation (as thickness meter) or measurement of force needed for tracking the blade on the textile surface is applied (Ajayi, 1992, 1994; Militký Bajzík, 2001, 2004). **Contacts less measurements** are usually based on the image analysis of fabric surfaces (Militký Bleša, 2008). The subjective assessment of the

KES for hand evaluation (Kawabata 1980) contains measuring device for registration the surface height variation (SHV) trace. This device (shown in the fig. 1) is a part of system KES

The main part of this device is contactor (see. fig. 2) in the form of wire having diameter 0.5

This contactor touches on the sample under the standardized conditions. The up and down displacement of this contactor caused by surface roughness is transduced to the electric

characterization of some real patterned and non-patterned fabrics surface roughness.

fabrics roughness can be investigated as well (Stockbridge H.C. et. al, 1957).

Fig. 1. Device for measurement of fabric surface characteristics

Fig. 2. KES contactor for measuring of surface roughness

**2. Measurement of surface profiles** 

produced by company KATO Tech.

mm. The contact force 10 g is used.

signal by a linear transformer put at up ends of the contactor. The signal from the transducer is passed to the high pass digital filter having prescribed frequency response (wavelength being smaller than 1 mm). The sample is moved between 2 cm interval by a constant rate 0.1 cm/sec on a horizontal smooth steel plate with tension 20g/cm and SHV is registered on paper sheet. The SHV corresponds to the surface profile in selected direction (usually in the weft and warp directions are used for SHV creation).

The preprocessing of SHV traces, from images of paper sheet resulting form KES can be divided into the two phases.


First of all the low *<sup>L</sup>* and high *<sup>H</sup>* surface frequency bands have to be specified. These cutoff frequencies are related to the wavelength limits *l*L and *l*H i.e. *lL L* 2 / and *lH H* 2 / . The low pass cut-off is related to Nyquist criterion i.e. / 2 *Ll dp* and the high pass cut-off is dependent on the maximum intersecting wavelength. For non-regular SHV, *l L <sup>H</sup>* has to be selected. The results of digitalization and parasite object removing is set of "clean" heights *R(di)* of fabric in places *0 <d <L* (*L* is maximum investigated sample length and *i = 1…M* is number of places). The distance between places *dp = di+1 - di* is constant. For the case of Kawabata device L = 2 cm and *dp=2/(N-1)* cm.

For deeper evaluation of SHV from KES device the rough signal from transducer has been registered and digitalized by using of LABVIEW system (Militký, 2007). Result is output voltage *U(d)* in various distances *d* from origin of measurements. For calibration of this signal the mean value *E(U)* and variances *D(U)* were estimated. From KES apparatus the mean thickness *R* and corresponding standard deviation *SR* were obtained. The transformation form voltage *U(d)* to thickness *R(d)* was realized by means of relation

$$R(d) = \overline{R} + S\_R \left( \frac{\mathcal{U}(d) - E(d)}{\sqrt{D(d)}} \right) \tag{1}$$

The result of this treatment is raw thickness *R(d)* in various distances *d* from origin.

The technique of roughness evaluation will be demonstrated on the analysis of the surface trace SHV of twill fabric (see fig 3) in the machine direction.

Fig. 3. Twill fabric used for roughness evaluation

Woven Fabrics Surface Quantification 125

Sampling frequency 50 s-1 (length between samples d = 0.013 mm)

Fig. 6. Accessory for roughness evaluation by the tensile testing machine

Variation of thickness *R(di)* or loads *F(di)* can be generally assumed as combination of random fluctuations (uneven threads, spacing between yarns, non uniformity of production etc.) and periodic fluctuations caused by the repeated patterns (twill, cord, rib etc.) created by weft and warp yarns. For description of roughness the characteristics computed from *R(d)* or *F(d)* in places *0< d< T* (*T* is maximum investigated sample length and *M* is number of

Profile of textile surfaces at given position along machine direction can be obtained by the analysis of especially prepared fabric images. The system RCM (Militký Mazal, 2007) is composed from CCD camera, lighting system and special sample holder controlled by a

Output from measurements is sequence of loads *F(di).* 

places ) are used.

personal computer (Fig. 7).

Fig. 7. Details of RCM apparatus

The arrangement of this accessory to the tensile testing machine is shown in fig. 6.

Blade movement rate 0.6 mm/s

Investigated length T = 30 mm

The raw SHV trace of twill fabric is shown in the fig. 4.

Similar approach is based on the measurement of R(d) by Shirley step thickness meter with replacement of measuring head by blade (Militký Bajzík, 2001). The Shirley step thickness meter is shown in the fig. 5.

Fig. 5. The step thickness meter SDL M 034/1

The principle of profile roughness evaluation by the simple accessory to the tensile testing machine is registration of the force *F(d)* needed for tracking the blade on the textile surface (Militký Bajzík, 2004). Roughly speaking, the *F(d)* should be proportional to the *R(d)*. In reality, the *F(d)* profile is different due to small surface deformation caused by the tracked blade. Based on the complex testing the following working conditions have been selected:

Blade contact pressure 0.2 mN

KES trace

0 100 200 300 400

length L

Similar approach is based on the measurement of R(d) by Shirley step thickness meter with replacement of measuring head by blade (Militký Bajzík, 2001). The Shirley step thickness

The principle of profile roughness evaluation by the simple accessory to the tensile testing machine is registration of the force *F(d)* needed for tracking the blade on the textile surface (Militký Bajzík, 2004). Roughly speaking, the *F(d)* should be proportional to the *R(d)*. In reality, the *F(d)* profile is different due to small surface deformation caused by the tracked blade. Based on the complex testing the following working conditions have been selected:

The raw SHV trace of twill fabric is shown in the fig. 4.


meter is shown in the fig. 5.

Fig. 4. SHV trace from LABVIEW

Fig. 5. The step thickness meter SDL M 034/1

Blade contact pressure 0.2 mN



height

0

0.05

0.1

Blade movement rate 0.6 mm/s Sampling frequency 50 s-1 (length between samples d = 0.013 mm) Investigated length T = 30 mm

The arrangement of this accessory to the tensile testing machine is shown in fig. 6.

Fig. 6. Accessory for roughness evaluation by the tensile testing machine

Output from measurements is sequence of loads *F(di).* 

Variation of thickness *R(di)* or loads *F(di)* can be generally assumed as combination of random fluctuations (uneven threads, spacing between yarns, non uniformity of production etc.) and periodic fluctuations caused by the repeated patterns (twill, cord, rib etc.) created by weft and warp yarns. For description of roughness the characteristics computed from *R(d)* or *F(d)* in places *0< d< T* (*T* is maximum investigated sample length and *M* is number of places ) are used.

Profile of textile surfaces at given position along machine direction can be obtained by the analysis of especially prepared fabric images. The system RCM (Militký Mazal, 2007) is composed from CCD camera, lighting system and special sample holder controlled by a personal computer (Fig. 7).

Fig. 7. Details of RCM apparatus

Woven Fabrics Surface Quantification 127

Output of data pre-treatment phase is array of slices i.e. array of vectors *Rj(i)* where index i corresponds to the position in jth slice. From this array it is simple to reconstruct whole

Above described devices are based on the measurements of surface height variation (SHV) or force needed for tracking blade across of surface in given direction. The analysis of surface images in two dimensions is based on the different principles (Militký Klička,

There exists a vast number of empirical profile or surface roughness characteristics suitable often in very special situations (Quinn Hannan, 2001; Zhang & Gopalakrishnan, 1996). Some of them are closely connected with characteristics computed from fractal models as fractal dimension and topothesy (Davies, 1999). A set of parameters for profile and surface characterization are collected in (Militký Bajzík, 2003, Militký Mazal, 2007). Parameters for profile and surface characterization can be generally divided into the following groups: Statistical characteristics of surface profile distribution (variance, skewness, kurtosis) Spatial characteristics as autocorrelation or variogram (denoted in engineering as structural function). Analysis is here in fact based on the analysis of random field

 Characteristics of overall complexity based on random linear stationary processes, selfaffined processes, long-range dependencies and on the theory of chaotic dynamics or

General surface topography is usually broken down to the three components according to wavelength (or frequency). The long wavelength (low frequency) range variation is denoted as form. This form component is removed by using of polynomial models or models based on the form shape. The low wavelength (high frequency) range variation is denoted as roughness and medium wavelength range variation separates waviness. The most common way to separate roughness and waviness is spectral analysis. This analysis is based on the

> 2 / *d* .

surface relief (see. fig. 11).

Fig. 11. Reconstructed roughness surface

**3. Surface roughness** 

nonlinear time series.

2007). These methods are not discussed in this chapter.

moment characteristics of second order.

Spectral characteristics as power spectral density or Fourier analysis.

Fourier transformation from space domain *d* to the frequency domain

For good image creation the suitable lighting (laser from the top) and fabric arrangement (bend around sharp edge) were selected (see fig. 8).

Fig. 8. Details of lighting system

Result after image treatment is so called "slice" which is the roughness profile in the cross direction at selected position in machine direction (the line transect of the fabric surface). The system RCM offers reconstruction of surface roughness plane in two dimensions. For this purpose, the sample holder is step by step moved in controlled manner. From set of these profiles, it is possible to reconstruct the surface roughness plane (Militký Mazal, 2007).

A finished cord fabric with relatively good structural relief was selected for demonstration of relief creation system capability. The original fabric surface is shown in the fig. 9.

Fig. 9. Roughness profile in the cross direction of tested fabric

Individual relief slices were created by combination of threshold, set of morphological operations (erosion, dilatation) and Fourier smoothing to the 30 terms (Quinn Hannan, 2001). Result of these operations is vector of surface heights in cross direction at specified machine direction (see fig. 10).

$$
\gamma\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee} \square\_{\vee} \mathcal{P}\_{\vee}
$$

Fig. 10. Slice after morphological operations and cleaning

For good image creation the suitable lighting (laser from the top) and fabric arrangement

Result after image treatment is so called "slice" which is the roughness profile in the cross direction at selected position in machine direction (the line transect of the fabric surface). The system RCM offers reconstruction of surface roughness plane in two dimensions. For this purpose, the sample holder is step by step moved in controlled manner. From set of these profiles, it is possible to reconstruct the surface roughness plane (Militký Mazal,

A finished cord fabric with relatively good structural relief was selected for demonstration

Individual relief slices were created by combination of threshold, set of morphological operations (erosion, dilatation) and Fourier smoothing to the 30 terms (Quinn Hannan, 2001). Result of these operations is vector of surface heights in cross direction at specified

of relief creation system capability. The original fabric surface is shown in the fig. 9.

(bend around sharp edge) were selected (see fig. 8).

Fig. 9. Roughness profile in the cross direction of tested fabric

Fig. 10. Slice after morphological operations and cleaning

Fig. 8. Details of lighting system

machine direction (see fig. 10).

2007).

Output of data pre-treatment phase is array of slices i.e. array of vectors *Rj(i)* where index i corresponds to the position in jth slice. From this array it is simple to reconstruct whole surface relief (see. fig. 11).

Fig. 11. Reconstructed roughness surface

Above described devices are based on the measurements of surface height variation (SHV) or force needed for tracking blade across of surface in given direction. The analysis of surface images in two dimensions is based on the different principles (Militký Klička, 2007). These methods are not discussed in this chapter.
