Structural integrity verification of polycarbonate type personal identity documents/Polikarbonatiniu asmens tapatybes dokumentu strukturinio vientisumo patikra.
Greicius, S. ; Daniulaitis, V. ; Vasiliauskas, R. 等
1. Introduction
As Lithuania has joined the Schengen area and due to the fact that
it has external borders of the area, officers of the State Border Guard
Service must take great responsibility in allowing or not allowing
individuals to enter not only to their own country, but the whole
Schengen area as well. Rapid globalization and integration processes
lead to a growing number of persons crossing the borders. In particular,
the flows of individuals crossing the borders increase in the events of
emergencies and moving across the borders is a common problem of all the
institutions involved in border control activities. Therefore, reliable
authenticity assessment of personal identity documents is a prerequisite
for normal existence of a human in the infrastructure of modern society.
According Schengen Borders Code [1] "all persons shall undergo
a minimum check in order to establish their identities on the basis of
production or presentation of their travel documents. Such a minimum
check shall consist of a rapid and straightforward verification, where
appropriate by using technical devices and by checking, in the relevant
databases, information exclusively on stolen, misappropriated, lost and
invalidated documents, of the validity of the document authorizing the
legimate holder to cross the border and of the presence of signs of
falsification or counterfeiting".
The officers, who inspect travel documents of persons crossing the
borders, should be familiar with the procedures of manufacture, issuance
and application of the documents as well as anti-counterfeiting
techniques. In practice, a number of methods are used for protection of
personal identity documents against counterfeiting and a number of
methods of assessing their authenticity are applied. For protection of
the documents can be applied different means--rainbow press (three color
protection grids, microtexts and other), special paint (optically
variable, shining under UV or infrared illumination, having magnetic,
electrical conductive, temperature sensitive or chemical properties or
other), special printing methods (intaglio printing, letterpress,
metallographic, laser printing, etc.), the paper of specific quality and
with distinctive features (watermarks, filaments, shining or nonshining
under the appropriate illumination, etc), new materials (polymers,
teslin, multilayer polycarbonate structures and other).
In order to ensure smooth movement of persons, document checking
procedures are to be reduced significantly in time. Usually for
inspection of the document (validity assessment, visa) only a few
minutes are allocated. In case of suspicion on the authenticity of the
document, it is inspected not only visually, but using technical devices
as well. With the evolution of manufacturing technologies of travel
documents, and materials used for the manufacture, as a very important
factor becomes the development and application of new devices and new
methods which allow to verify the document's authenticity.
In order to ensure smooth movement of persons crossing the borders
personal travel documents of European Union countries and majority of
the countries of the world are being developed taking into account the
requirements of EU and recommendations of the International Civil
Aviation Organization (ICAO). Also they should comply the requirements
of standard ISO/IEC 7810:1995 for ID--3 cards and the requirements
defined in the document Doc9303 of the International Civil Aviation
Organization (ICAO) as well as in COUNCIL REGULATION (EC) No 2252/2004
of 13 December 2004 on standards for security features and biometrics in
passports and travel documents issued by Member States [2]. The main
requirements to data sheet of the document (the main object of
counterfeit) are set on its thickness (it should not exceed 0.9 mm) and
on the material from which it is manufactured (nowadays the most
frequently a multilayer structure made of polycarbonate foil and other
synthetic materials is used). Typical structure of a document sheet
which is composed of several layers of polycarbonate foil Makrofol ID
6-2 laserable, Makrofol ID 4-4 white [3], manufactured by the German
company Bayer Material Science AG and a layer of synthetic material is
presented in Fig. 1.
Attention should be paid to the fact that the structure as
presented is just typical (recommended) structure. In the countries that
currently apply multilayer structures for their travel documents (USA,
majority of European countries, the countries of South-East Asia,
Central and South America, Africa) the data sheets are manufactured from
different number of polycarbonate foil layers each of which has
different thickness integrating these layers with a layer of teslin
(synthetic material based on silicon oxide)--as presented in Fig. 2.
Statistical analysis of the results on authenticity assessment of
personal identity documents reveals that data sheets most frequently are
damaged (with the aim to counterfeit) by mechanical means in the zone of
photo. After damaging of the data sheet in case of counterfeit and
putting efforts to restore its initial state, always residual
technological defects remain (joining of polycarbonate foil layers and
teslin layer by fusion or applying gluing materials and other). In Fig.
3 an example of the data sheet which was mechanically damaged with the
sequent efforts to restore its primary state is presented.
For authenticity assessment of the travel documents various methods
of nondestructive control can be applied. They are based on different
principles and differ by sophistication level of the hardware and
software applied [4-6]. As the methods applied, the methods of visual
inspection, laser, ultrasonic, acoustic emission, vibration methods,
mechanical loading, thermo graphic, thermal emission and other methods
can be applied [7, 8].
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Taking into account specific features of the data sheet
manufacturing technology (fusion of the layers and/or gluing), the
present research is based on the assumed hypothesis--after mechanical
damaging of the document's structure with the following attempts to
restore its primary state the existence of residual mechanically damaged
zones (air bubbles--gaps, lack or excess of gluing material, melting of
the layers) should have an influence on physical and mechanical
properties of the structure [9-12]. The change of such properties could
serve as the background for authenticity assessment of the document
under inspection. In order to prove the hypothesis experimental research
and simulation of the structure behavior applying thermo graphic and
thermal emission methods was performed.
2. Experimantal research
With the aim to make analysis of the influence of technological
defects in the data sheet (delaminating of polycarbonate foil and teslin
layer, locally damaged zones, inserts of non proper material) on thermal
properties (e.g. thermal conductivity) experimental research of heat
flux transfer in the direction of the sheet thickness was performed. An
assumption that heat conductivity is different in structurally healthy
and damaged zones would suggest not uniform temperature field on a
surface of the sheet if its opposite surface is affected by a uniform
across all the surface area heat flux.
Experimental research was performed using the test rig, the
structure of which is presented in Fig. 4. As it is seen, thermo graphic
camera A20 (FLIR Systems, Inc., USA) was used to capture the image of
temperature fields on the sheet's side and numerical values of
temperatures at analyzed points were recorded by infrared thermometer
Testo 845 (TESTO, Inc., USA). Experimentation was carried out according
the following procedure: One side of the analyzed document was affected
for 120 seconds by a locally applied heat flux (diameter of the heat
flux zone approximately equals to 10 mm) which was generated by a heat
source of infrared radiation. Simultaneously surface temperature
dynamics (change in time) on the opposite side of the document was
recorded by infrared thermometer Testo. Then the heat source was removed
allowing the structure to cool recording the surface temperature for 250
s from start point of the test. Together temperature isosurfaces of the
relatively big area of the document's sheet covering the heat flux
affected local zone were captured by thermo graphic camera A20 at
different instances of time. Such testing procedures were performed with
structurally healthy and mechanically damaged document sheets. Next,
onto one side of the document sheet uniformly distributed over all the
surface area heat flux was applied. Practically this was executed by
bringing into touch contact with the sheet's surface a uniformly
heated massive body. In the later testing case temperature isosurfaces
were captured by thermo graphic camera A20 as well. Structurally healthy
and mechanically damaged document sheets were tested. It is worth paying
attention that in case of mechanically damaged sheets temperature
isosurfaces indicate not uniform temperature field on the surface.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
Results of the experimental research are given in Figs. 5 and 6. In
Fig. 6 examples of temperature change curves, characteristic for
structurally healthy and mechanically damaged documents in case when
ambient temperature was equal to 20.5 [degrees]C, the document was
affected by locally applied heat flux for 120 s and then allowed to cool
to ambient temperature, are presented. Fig. 5 presents the captured
image of thermal field on the surface of mechanically damaged document
when on its opposite side was locally applied source of infrared
radiation. In this case non even distribution of temperature field can
be distinguished.
The results of temperature measurement reveal that under identical
conditions of external heating, temperature values and their change
dynamics at different points of the surface differ what suggest
different parameters of thermal conductivity at these zones.
3. Theoretical analysis
Taking into account the results of performed experimantal research
and with the aim to get a model describing teperature dynamics, a
theoretical calculation scheme of thermal energy transfer was built as
shown in Fig 7.
[FIGURE 7 OMITTED]
The numbers in it represent the equations for the solution of heat
exchange problem as follows.
On all side surfaces and in the top surface the boundary
condition--heat flux
-n(-k[nabla]T) = [q.sub.0] + h([T.sub.inf] - T) (1)
The condition of heat flux balance in all subdomains
[rho][C.sub.p] [[partial derivative]T/[partial derivative]t] +
[nabla](-k[nabla]T) = 0 (2)
On the bottom surface which is heat affected the boundary
condition-temperature
T = [T.sub.0] (3)
[FIGURE 8 OMITTED]
On common surfaces of subdomains the boundary condition--continuity
[-n.sub.u]([-k.sub.u][nabla][T.sub.u])[-n.sub.d]([-k.sub.d]
[nabla][T.sub.d]) = 0 (4)
where k is thermal conductivity, [k.sub.u] and [k.sub.d] are
out-of-plane thermal conductivity, upside and downside at the subdomains
boundaries W/(mK); [rho] is density, kg/[m.sup.3]; n is normal vector to
a surface; [n.sub.u], [n.sub.d] are normal vectors to the boundaries of
subdomains , upside and downside; [q.sub.0] is a inward heat flux,
W/[m.sup.2]; [C.sub.p] is heat capacity at constant pressure, J/(kgK); h
is heat transfer coefficient, W/([m.sup.2]K); [T.sub.inf] is external
temperature, K; [T.sub.0] is surface temperature, K; [T.sub.u],
[T.sub.d] are out-of-plane temperature, upside and downside on the
boundaries surfaces; T is temperature K; [nabla] is temperature
gradient, t is time, s.
The following physical properties of materials and the parameters
were used:
--Polycarbonate: k = 0.2 W/(mK); [C.sub.p] = 1200 J/(kgK); [rho] =
1200 kg/[m.sup.3];
--[Air.bar] k = 0.25 W/(mK); [C.sub.p] = 1015 J/(kgK); [rho] = 1.2
kg/[m.sup.3];
--[Teslin.bar] nondamaged: k = 33 W/(mK); [C.sub.p] = 550 J/(kgK);
[rho] = 1805 kg/[m.sup.3];
--[Teslin.bar] damaged: k = 0.017 W/(mK); [C.sub.p] = 600 J/(kgK);
[rho] = 1700 kg/[m.sup.3];
--[q.sub.0] = 0 W/[m.sup.2], h = 20 W/([m.sup.2]K), [T.sub.inf] -
293.6 K.
For the solution of the problem of heat exchange FEM model
implementing the presented calculation scheme was constructed using
COMSOL Multiphysics system.
Physical properties of polycarbonate and air were taken from
material data basis of the COMSOL Multiphysics system. Thermal
properties of the damaged and nondamaged teslin layer were determined
using the data obtained at experimental research presented above.
Transient process analogous to the one obtained by experimentation was
modeled--at the distance of 0.0005 m from the bottom plane centre of
multilayer data sheet at the circular shaped area with the radius of
0.005 m 1000 W/m2 inward heat flux was applied for the 120 s duration.
Then it was removed and the data sheet was allowed to cool. The obtained
results are presented in Fig. 8.
In order to analyze sensitivity of the model in detecting the
defects, several defects, different in their geometry, dimensions and
location place were introduced into the data sheet.
Simulation procedure using such data sheet is analogous like in
previous experiment. Heating of the bottom surface of the data sheet was
simulated by applying to it a uniform field of temperature of 27
[degrees]C and constant in time at the distance of 0.0005 m from the
surface. Temperature of the top surface of the sheet stabilizes after
transient process of 130 s duration. The process is presented in Fig. 9.
[FIGURE 9 OMITTED]
The simulation results in Fig. 9 indicate 0.5[degrees]C surface
temperature difference of mechanically damaged and nondamaged data sheet
structure. Such difference is sufficient to be registered by modern
thermo vision cameras. The transient processes of surface temperature
were recorded at the zones A, B and [OMEGA] (Fig. 7). Temperature field
of the top polycarbonate layer of the data sheet is presented in Fig.
10. At the zones with mechanically damaged teslin layer temperatures are
lower than in the zones of nondamaged structure of the data sheet. The
reason is the change of thermal properties of teslin. Even the damaged
zones of small dimensions can be distinguished, i.e. a circle of the
diameter 0.001 m is clearly visible.
[FIGURE 10 OMITTED]
Temperature distribution on the top of the data sheet's
polycarbonate layer across the section as indicated by the line in Fig.
10 is presented in Fig. 11.
From these simulation results (Fig. 11) temperature decrease on the
top of the data sheet due to mechanical damage of teslin layer can be
clearly seen.
[FIGURE 11 OMITTED]
Temperature field can be presented in the form of temperature
isosurface as given in Fig. 12.
[FIGURE 12 OMITTED]
4. Coclusions
1. The nature of mechanical damage of multilayer structure of
travel documents (polycarbonate-teslin) suggests a hypothesis of the
change of its physical properties in the damaged zones what serves as a
background for the development of effective methods of counterfeiting
detection.
2. Experimental research of the process of heat exchange through
the thickness of the documents data sheet proved the damaged zones to
have different values of thermal parameters compared to the ones of
structurally healthy zones of the data sheet.
3. A mathematical model of the heat exchange process and its
realization by FEM model in COMSOL Multiphysics system were developed
and thermal conductivity parameter of damaged and nondamaged teslin
layer was identified from the results of experimental research. The
simulation results of the process under identical heating and boundary
conditions as during experimentation were found out to be in agreement
with the experimental research results. This proves the model's
validity.
4. Simulation of heat exchange process when the bottom surface of
the data sheet was heated resulted in temperature differences on the top
surface of the sheet at damaged and nondamaged zones sufficient for
detecting with modern thermo vision cameras (0.5[degrees]C). Taking into
account short duration of the process and reasonable heating
temperatures ([T.sub.0] [approximately equal to] 27[degrees]C) it can be
concluded that analysis of temperature fields during heat transfer
through the sheet' s thickness can be used as a method for
structural integrity verification of the data sheet of a travel
document.
Received April 27, 2011
Accepted April 05, 2012
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S. Greicius, Mykolas Romeris University, Kaunas Faculty of Public
Security, V. Putvinskio 70, 44211 Kaunas, Lithuania, E-mail:
[email protected]
V. Daniulaitis, Kaunas University of Technology, Studentu g. 50,
51368 Kaunas, Lithuania, E-mail:
[email protected]
R. Vasiliauskas, Mykolas Romeris University, Kaunas Faculty of
Public Security, V. Putvinskio 70, 44211 Kaunas, Lithuania, E-mail:
[email protected]
K. Pilkauskas, Kaunas University of Technology, Mickeviciaus 37,
44244 Kaunas, Lithuania, E-mail:
[email protected]
V. Jurenas, Kaunas University of Technology, Mechatronics Center
for Research, Kestucio str. 27, 44312 Kaunas, Lithuania, E-mail:
[email protected]
http://dx.doi.org/ 10.5755/j01.mech.18.2.1570