NON-DESTRUCTIVE METHOD FOR CONTROLLING THE SURFACE DENSITY OF THIN FIBROUS MATERIALS (66-69)

66 Национальная ассоциация ученых (НАУ) # 57, 20 20
NON -DESTRUCTIVE METHOD FOR CO NTROLLING THE SURFACE DENSITY OF THIN
FIBROUS MATERIALS

Shlyakhtenko Pavel
Candidate of Physical and Mathematical Sciences, Doctor of
Technical Sciences, Profe ssor Emeritus, St. Petersburg State
University of Industrial Technology and Design, Russia

ABS TRACT
The optical method for contr olling the surface density of thin fiber -containing materials is cons idered.
Examples of such materials are semi -finished produ cts of spinning production, condenser paper,
proteinaceous sausage casing, optically transparen t composite materials, for example , aqueous solutions of
cellulose fibers used in the paper industry, o r industrial effluents of these enterprises containing opt ically
anisotropic light -transmitting fibers, and the like. .
The method consists in the fact t hat the object under investigation is illuminated through the polarizer with
plane polarized light, in which the plane of the light vector rotation is rotated by 45 degrees relative to the machine
direction of the material being studied. By the magnitude o f the measured luminous flux passi ng through the
analyzer, the optical plane of which is 90 degrees rot ated relative to the optical plane of the polarizer, the
concentration of fibers in the test material is judged.
A diagram of the device according to the method under discussion is given, and its performance has been
proved on samples of various fiber -containing materials.
Keywords : natural and chemical fibers; f ibrous and fiber containing materials; optical anisotropy;
interference of polarized light.

Introduction
In work [1] it is offe red and in work [2] an optical
method for controlling the su rface density of such
materials was described.
The method relates to non -destructive optical
methods for monitoring flat light -transmitting materials
containing fi bers.
Examples of such materials are semi -finished
products of a spinning type, condenser pap er, a white -
cured sausage casing, optically transparent composite
ma terials consisting of an isotropic matrix reinforced
with synthetic or natural fibers, for exam ple, aqueous
solutions of cellulo se fibers used in the paper industry,
or industrial effluent s of these enterprises containing
optically anisotropic light -transm itting fibers, and
similar materials.
Closest to the proposed method is a method of
controlling the physical parameters of movin g flat
fibrous materials [3]. The method consists in the fac t
that the test material is illuminated with a parallel beam
of ligh t perpendicular to its surface. Using the
photodetector, the entire light flux emitted by the
illuminated material in the direct ion of light incidence
is recorded, and this flux is compare d with the flux
recorded by the photodetector for a reference sample of
this material, and the surface density is judged by the
difference in the light streams. In the device according
to this met hod, the photodetector recorded the entire
luminous flux emi tted by the illuminated surface of the
material under study and the standard.
Results and discussion
The aim of the proposed method [1] is to increase
the accurac y of measurement. Figure 1 shows a
diagram illustrating its operation.


Figure 1. The device diagram explaining the method
of controlling the surface density of the material
О
О
Iвых ~Ф -ФS
S
9
1
2
4
7 8 α 3
5 6
10
R 11
О
О

Националь ная ассоциация ученых (НАУ) # 57, 20 20 67
Non -polarized light is incident by a parallel beam
on the pol arizer 1 and illuminates the test material with
light in which the electric vector E oscillates at an angle
α = 45 0 to the dire ction of drawing of the controlled
planar light -transmitting material 2. The material
studied contains fibers mainly oriented alo ng the
machine direction (drawing direction). Figure 1 shows,
for example, two types of light t ransmitting fibers 3, 4,
5.
Anis otropic fibers 3, 5 are oriented along ( 3) and
perpendicular (5) to the machine direction,
respectively. In these fibers, inciden t light excites two
light waves ("ordinary" ray and "extraordinary") of the
same intensity, whi ch interfere with th e output of the
light fiber in the general case of elliptical polarization.
Fiber 4 has a complex relief of geometry in
volume, i.e., many ir regular inhomogeneities on the
surface and in volume. The reflections and scattering of
light b y these inhomogeneit ies lead to the fact that the
light transmitted through this fiber is scattered and
depolarized.
Obviously, in this case, part of the light f rom the
fibers 3, 4, and 5 passes through the analyzer 6, set so
that its optical plane is perp endicular to the opt ical
plane o f the polarizer 1. At the same time, the light
transmitted through the isotropic filling of the material
under study is completel y blocked by the analyzer 6.
Thus, only light coming from the fiber cones
located in the illumi nated region of the test materia l,
which is then collected at the receiving area of the
photodetector 8, is incident on the lens 7.
The signal from the output of the linear
photodetector at low fiber concentrations in the
material, when the fibers do not obscure each other,
should be p roportional to the number of illuminated
fibers. This signal through the amplifier 9 and the key
10 is fed to a comparison circui t 11 , where it is
compared with a signal remembered by the circuit
when measured on a reference sample of the test
material wit h a known surface density (thickness, with
a constant width of the material).
Measurements on the reference sample are carried
ou t according to the above -described diagram on the
same device, when instead of the material bei ng
studied, the refe rence sample is placed, and the key is
transferred from the " R" position to the " S" position. In
this case, the signal from the photodetector 8,
proportional to the number of fibers in the illuminated
part of the reference sample (thick ness or surface
density), is fed through an amplifier 9 to the
corresponding input of the comparison circuit 11 ,
where it is stored.
The signal from the output o f the comparison
circuit, proportional to the difference of the light fluxes
Ф – ФS , indicates the deviation of the controlled
parameter of the material under study from the
reference value.
The proposed method is based on measuring the
concentration of f ibers in the material.
In the case of an increased concentration of fibers,
when they shade eac h other, the measured difference
signal is functionally related to the surface density of
the material. If the type of function is known, then the
desired value can be calculated. If unknown, then the
form of this function can be found experimentally
durin g control measurements on the ap propriate
number of samples of this material with independently
measured surface density values.
Figure 2 shows the dependences o f the voltage U
at the output of amplifier 9 (Figure 1) on the surface
density ơ for reindeer w ool comb (curve 1) and sheep
woo l (curve 2) at a wavelength of λ = 555 nm (comb
direction in samples oriented at an angle α = 45 0 to the
optical plane of the pol arizer).



From the course of the curves in this figure it can
be seen that the appearance of t he curves is the same
qualitatively. In the initial section (for thin samples),
the dependence is linear and increasing. After reach ing
a maximum, it is close to a linear dependence and
decreases.
The course of the dependences in these sections
can be appr oximated by the dependences from which
the desired value of σ from the measured value of the
voltage U can be calculated by the form ulas: for
reindeer wool at a low density σ = 60 U, for a high
density σ = 660 (0 , 18 - U); for sheep’s wool at low
Figure 2. Experimental dependences of the
measured signal on the surface density σ for
reindeer wool (1) and sheep’s (2)
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 σ, g/m2
U, mV
1
2

68 Национальная ассоциация ученых (НАУ) # 57, 20 20
density σ = 350 U, for high density σ = 600 (0.265 - U).
Moreover, the dimension of the resulting density is σ [g
/ m 2], the dimension is U [V ].
The quantitative differences in the course of
curves 1 and 2 in Fig. 2 are associated with d ifferences
in the color and d iameter (d) of the fibers (for the
studied reindeer core fibers d = 0.3 mm, for the fibers
in the sheep’s comb d ~ 0.01 mm).
To cont rol the surface density of the proteinaceous
sausage casing at the Belkozin plant (Luga), accor ding
to the considered method , an operating device was
assembled , a block diagram of which is shown in
Figure 3.


A light emitting d iode 1 was used as a light source,
emitting light whose wavelength lies in the region of
567 nm , the light from which is transmitted through
polaroid 2, the op tical plane of which is oriented at an
angle of 45 0 to the direction of drawing of the material
under study. The light emitted by the test material 3
through analyzer 4 crossed with the polari zer 2
(polaroid film) ente rs the photodetector 5, which
consists of solar photodiode batteries connected in
parallel and installed parallel to the surface of the test
material 3 immediately after the analyzer 4.
The signal from the photodetector 5 is fed to the
amplifier 6, passes through a phase detector 7,
connected to the reference frequency generator 8 and
the amplifier 9. A part of the light from the source 1
goes to the photodiode receiver 10 . The signal from the
photodetector 10 then goes to one of their inputs an
amplifier 11 , to the second input of which a sig nal
comes from a voltage divider 12 connected to a
reference frequency generator 8.
From the outp ut of amplifier 11 , the signal is
supplied to a phase detector 13 connected to 8, an
integrator 14 , and a chopper 15 cont rolled by a
generator 8. The amplifier 9 is connected to a key 16,
which can be connected either to the measuring input
of the comparis on circuit 17 (“R”) , or to the reference
input ("S").
The device operates as follows. The var iable
component of th e sig nal from the photodetector 5,
passing through the amplifier 6, enters the phase
detector 7, the reference signal of which is generated by
the reference frequency generator 8. The amplified and
detected signal from the photodetecto r 5 then goes to
the const ant voltage amplifier 9, the output voltage of
which characterizes the surface density of the
investigated fiber - sheet material 3.
To compensate for temperature instability and
temporary departure of the parameters of the emitte r 1,
the emitter is p owere d as follows. The signal from the
photodetector 10 (using a solar battery of the same type
as in the photodetector 5), which characteri zes the
radiation power, is compared with the reference signal
and amplified by a differential amplifier 11 . The
ref erenc e signal is obtained by attenuating the signal of
the reference frequency generator 8 in the voltage
divider 12 . From the output of the amplifier 11 , the
signal enters the phase detector 13, then is integrated
Figure 3. Block diagram of the device
18
S
16
R
14
- +
7
6 8
11
13
15
3
12
5 4
9 17
1
2
10

Националь ная ассоциация ученых (НАУ) # 57, 20 20 69
into 14 and through the chopper 15, contr olled by the
generator 8, is supplied to the emitter 1.
The electrical circuit of amplifiers operating on a
variable signal component, in co mbination with phase
detection, provides the necessary protection and
independence of readings from extraneous illum inati on
and intrinsic noise of highly sensitive amplifiers.
At the output of the comparison circuit 17 , the
signal measured on the test mate rial is compared with
the signal received and stored earlier in the
measurements when the key 16 is in position “S”, and
instead of the test material, a reference sample of the
same material known surface density. The mismatch
signal from the output of the circuit 17 can be used to
adjust in the circuit automatically adjust the surface
density to th e standard.
The photo sensi tive part of the circuit, together
with the emitter, is placed in a light -shielding casing 18
to protect photodetectors from irregular constant
flashes that change the recombination ability of pn
junctions, which is important when their power is
suffi cient .
Figure 4 shows the experimental dependence of
the measured signal at the output of amplifier 9 on the
surface density of the protein -sausage sausage casing,
measured by an independent method in a factory
laboratory by weighing o n an analytical balan ce.


The measurements were carried out according to
the method under consideration, both on individual
samples an d on samples obtained by adequately
superimposing (combining machine directions) the
samples on top of each other.
It can be seen that in the entire range of shells
manufactured by the «Bel -kozin» factory, whose
surface density varies up to 300 g / m2 for various
diameters, this dependence is linear.
Measurements showed that measurements of
surface density in th is range a re confidently recorded at
the level of 5% (P = 0.9) of the standard, which fully
satisfied the needs of the factory.
The measurements per formed on the prototype
[3], which were carried out on the same device, but
without a polarizer 2 and analyz er 4, gave an error in
measuring the surface density, significantly exceeding
the required tolerances for controlling the protein shell
in the requi red interval. In measurements, the
dependence of the signal on surface density was
extremely ir regular. For some sampl es of the sausage
casing, the deviation sign at the output of circuit 17 was
positive, for other samples of the same surface density
it wa s negative, especially when measuring the surface
density of up to 200 g / m 2 , which made the
measurements by the pro totype method completely
unsuitable in the most interesting factory range.

References
1. Patent RF № 2024011 G 01 N 21/86 Sposob
kontrolia poverhnostnoi plotnosti slabopogloshaycshih
voloknosodergaschih materialov / Shlyakhtenko
P.G., Zinoviev A.V. , Gilikova R.P. Opubl. 30.11.94.,
Бюл . № 22.
2. Pavel Shlyakhtenko Opticheskie methodi
kontrolia parametrov voloknosodergiaschih
materialov. Kontrol st rukturi tekstilnih materialov:
LAP LAMBERT Academic Publishing GmbH & Co.
KG. – 2012. – 347 s.
3. Patent RF № 1 483344 G01 N 21/86. Ustroistvo
dlia kontrolia fizicheskih paramerrov dviguchihsia
ploskih voloknistih svetopropuskayshih materialov /
Shlyakhtenko P .G.,Surikov O.M., Тruevtsev N.N. I dr.
Opubl . 30.05.89, Bul. № 20.


Figure 4. Experimental dependence U ( σ) for a
sausage casing
0
50
100
150
200
250
300
350
400
0 100 200 300 400 500
Поверх.плотность σ, g/m2
U, mV