Strength of optical glass under conditions of axial compression
We studied optical glass types LK5, K8, TK3, TKII4 belonging to the group of crown glasses (containing lead oxide PbO < 3%), and FI, FI01, TFI01, TFI0 belonging to the group of flint glasses (containing lead oxide PbO > 3%).
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
1985
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nasplib_isofts_kiev_ua-123456789-1828702025-02-09T16:15:47Z Strength of optical glass under conditions of axial compression Прочность оптических стекол в условиях осевого сжатия Okhrimenko, G.M. Rodichev, Yu.M. Maslov, V.P. Scientific-technical section We studied optical glass types LK5, K8, TK3, TKII4 belonging to the group of crown glasses (containing lead oxide PbO < 3%), and FI, FI01, TFI01, TFI0 belonging to the group of flint glasses (containing lead oxide PbO > 3%). 1985 Article Strength of optical glass under conditions of axial compression / G.M. Okhrimenko, Yu.M. Rodichev, V.P. Maslov // Проблемы прочности. — 1985. — № 8. — С. 1125-1130. — Бібліогр.: 14 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/182870 539.411:620.173.24.666 en Проблемы прочности application/pdf Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Scientific-technical section Scientific-technical section Okhrimenko, G.M. Rodichev, Yu.M. Maslov, V.P. Strength of optical glass under conditions of axial compression Проблемы прочности |
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We studied optical glass types LK5, K8, TK3, TKII4 belonging to the group of crown glasses (containing lead oxide PbO < 3%), and FI, FI01, TFI01, TFI0 belonging to the group of flint glasses (containing lead oxide PbO > 3%). |
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Article |
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Okhrimenko, G.M. Rodichev, Yu.M. Maslov, V.P. |
| author_facet |
Okhrimenko, G.M. Rodichev, Yu.M. Maslov, V.P. |
| author_sort |
Okhrimenko, G.M. |
| title |
Strength of optical glass under conditions of axial compression |
| title_short |
Strength of optical glass under conditions of axial compression |
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Strength of optical glass under conditions of axial compression |
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Strength of optical glass under conditions of axial compression |
| title_full_unstemmed |
Strength of optical glass under conditions of axial compression |
| title_sort |
strength of optical glass under conditions of axial compression |
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Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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1985 |
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Strength of optical glass under conditions of axial compression / G.M. Okhrimenko, Yu.M. Rodichev, V.P. Maslov // Проблемы прочности. — 1985. — № 8. — С. 1125-1130. — Бібліогр.: 14 назв. — англ. |
| series |
Проблемы прочности |
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AT okhrimenkogm strengthofopticalglassunderconditionsofaxialcompression AT rodichevyum strengthofopticalglassunderconditionsofaxialcompression AT maslovvp strengthofopticalglassunderconditionsofaxialcompression AT okhrimenkogm pročnostʹoptičeskihstekolvusloviâhosevogosžatiâ AT rodichevyum pročnostʹoptičeskihstekolvusloviâhosevogosžatiâ AT maslovvp pročnostʹoptičeskihstekolvusloviâhosevogosžatiâ |
| first_indexed |
2025-11-27T21:47:09Z |
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2025-11-27T21:47:09Z |
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| fulltext |
STRF~qGTH OF OPTICAL GLASS UNDER CONDITIONS OF AXIAL COMPRESSION
G. M. Okhrimenko, Yu. M. Rodichev,
and V. P. Maslov
UDC 539.411:620.173.24.666
Glass and pyrocerams can be effectively used in structures operating under high exter-
nal pressure, as well as in other products of new technology subjected to compression. In
some cases it is indispensable to use transparent materials with good optical properties,
but so far only insufficient data are available on the structural strength of optical glass
and pyrocerams under compression [1-4], and this limits the possibilities of designing highly
stressed structural elements.
The object of the present work was to investigate the structural strength of different
kinds of optical glass under axial compression, with a view to the effect of the chemical
composition, the shape of the cross section, and the conditions of support of the specimens,
as well as the length of their storage after their production.
We studied optical glass types LK5, K8, TK3, TKII4 belonging to the group of crown
glasses (containing lead oxide PbO < 3%), and FI, FI01, TFI01, TFI0 belonging to the group
of flint glasses (containing lead oxide PbO > 3%). Information on the chemical composition,
specific weight, and some optical properties of the investigated types of glass is presented
in Table I.
Light crown glass (glass LK5) belongs to the five-component system R~0--B2Os--AI~O3--SiO2--F.
Crown glass K8 belongs to the system K20-Na~O-B~Os--Si02 containing a small amount (10-12%) of
oxides of bivalent metals PbO, BaO, ZnO, CaO, MgO. Heavy crown glass (TK3, TKII4) is based
on the ternary system BaO--B2Os--SiO~.
The basis of the second group of glass, flint glass (FI, FI01) and heavy flint glass
(TFI01, TFI0), is the system K2(>-PbO-SiO2. Flint glass contains up to 22% lead oxide, heavy
flint glass 1.5-2 times more.
Some data on the characteristics of strength and elasticity of optical glass and pyro-
cerams from the literature are presented in Table 2 from which it can be seen that in regard
to the principal mechanical characteristics (bending strength Ob, tensile strength ot,
modulus of elasticity E, Poisson ratio ~, and compressive strength on plane supports OCc)
the optical compositions are comparable with technical glass [i].
We point out that the last characteristic is usually determined in tests of cubic,
prismatic, or cylindrical specimens on smooth metal supports. As ultimate strength OCc we
adopted the ratio of the maximum load at the instant of exhaustion of the load-bearing
capacity to the initial cross-sectional area of the specimen.
The basic shortcomings of such a way of testing are that the specimen is not subjected
to uniform uniaxial compression but is exposed to the effect of high contact stresses. The
maximum level of these stresses applied to the edges of the bearing part of the specimen is
a multiple of the level of the mean compressive stresses.
Tests of technical glass and pyrocerams showed that destruction in the form of spalling
of the bearing edges and cracking of the specimens on account of longitudinal cracks begins
long before the limit load is attained. When the load is further increased, this process is
intensified and the area of the bearing sections of the specimen becomes smaller.
The results obtained in such tests are always considerably lower than in uniaxial com-
pression, they are characterized by large scatter (variation coefficient v up to 20-30% --
Table 2), and they cannot be used as objective indicators of the compressive strength of
glass and similar brittle materials [i, Ii].
Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Trans-
lated from Problemy Prochnosti, No. 8, pp. 77-82, August, 1985. Original article submitted
July Ii, 1983.
0039-2316/85/1708-1125509.50 �9 1986 Plenum Publishing Corporation 1125
TABLE i. Chemical Composition and Optical Characteristics of the Investigated Types
of Glass [5]
Type of
glass
LK
K
TK
F
TF
SIO,
72..74
60...79
34...66
67...74
57.-69
Content of principal components, %
B, Os
8..21
0...21
4...28
PbO
17_.22
23...40
RO
1...2
0...18
15...46
R,O
5...10
lO...19
0...9
6...7
2...8
Re,active
index m
<1,500"
1,500...I,540
1,555...I,665
1,600...I,640
1.640...I.900
Dispersion Specific
coefficient weight
v v,g/cmSr
67*
0,0075
67...55
64...50,5
35...39
3,5...22
*Under the line the mean dispersion is given.
%The specific weight of pyroceram SOII5M is equal to 2.48 g/cm 3.
2,14
2,42
3,22
3,51
4.66
TABLE 2. Characteristics of Strength and Elasticity of Optical Glass and Pyrocerams
from the Literature
Material OCc , MPa a b, MPa Or, MPa E.10-5. MPa ~t
Glass K8 [7. 8. 9]
Glass LK5 [10]
~yroceram ~ I ~ 4 1 3 , 4]
yroeeram
Pyroceram 11575 [2]
Pyroceram 'I00915 [P]
Pvroceram STL-I [6]
Pvroceram STL-2 [6]
Pvroceram STL-3 [6]
Pvroceram STL-4 [6]
238(29,8)*
1000--1200
930(22,2)
680--790
1290(18,0)
131%~],27)
799
652
69O
60 (6,7)
160
82 (14,3)
76
19,2 1" (25,6)
154 ~" (40,4)
104
ll6
IO0
l l 5
29 (31,5)
59, l (15,6)
*In parentheses is the sample variation coefficient.
%Obtained in completely reversed bending of plates.
0. 823
0,76
0.68--0,79
0.84
0.80
0,81
0,90
0,82
0.85
0,18
0,26
0,29
0,28
0.29
In the present work, the ultimate strength Occ was regarded as a nominal quantitative
characteristic expressing the ability of the material to resist the effect of high contact
loads. Such data may be useful in comparisons of the structural properties of various
brands of glass and pyrocerams, in particular, in the evaluation of their durability in
highly stressed joints of components made from heterogeneous materials in which the role of
contact stresses is very important.
However, identifying ultimate strength in contact loading with the ultimate strength
in uniaxlal compression, as is done by authors of technical and scientific literature on
the mechanical properties of glass and pyrocerams [6, i0, 12, 13], may lead to considerable
errors.
The strength of the investigated kinds of glass under uniaxlal compression was deter-
mined by a previously described method [ii, 14]: it involves gluing the end faces of
cylindrical specimens (diameter 10 mm, height 30 mm) into steel rings; it is thereby possible
to increase the load-bearlng capacity of the support sections by inducing triaxlal compres-
sion in the local zone to such an extent that fracture sets in and proceeds in the central
working part of the specimens alone, these parts being subjected to uniform unlaxlal com-
pression [i]. It was shown in [i, 2, 3, ii] that in this case the level of rupture stresses
Sc of technical and optical glass and of pyrocerams is 1.5-3 times higher than ~Cc, and the
variation coefficient (v = 5-10%) is comparable with the variation coefficient for metallic
structural materials.
The height of the microunevennesses of the working part of all tested specimens after
grinding with a diamond tool satisfied the condition Rz~l.25 Bm. The loading rate was 20-
30 MPa/sec.
The magnitude of Oc_ was determined with the aid of a fixture described in [3]. In this
case, the end faces of t~e specimens had a height of unevennesses not exceeding 0.63 um, and
under load they were in contact with supports of steel U8A which were heat-treated to a hard-
ness HRC 56-60.
Elements of structures made of optical glass may have sharp edges made in flat grinding.
Some features of this kind of diamond processing and the presence of sharp edges usually make
1126
270
C60
250
2~0
~30
~fO
201
900
/j' //
t , /
o,25
/ ! / o
i ///
,/// /i I
o / / ,
1200 1500 1800 21gO ~r,MPa
-08~
900 1200 1500 ~800
Fig. i. Empirical distribution functions of the
ultimate strengths in axial compression o c with
confidence intervals at the confidence level ~ =
95% of optical glass TKII4 (light dots) and KF
(dark dots). (Pj are accumulations of purity;
Zp is the quantile of normalized normal distri-
bution.)
the compressive strength of prismatic specimens of technical glass by 5-10% lower than the
strength of cylindrical specimens [i]. To take the mentioned effect into account in evaluat-
ing the structural strength, we did not test cylindrical specimens alone but also prismatic
specimens made from most of the investigated materials. The base of such a specimen had a
side I0 mm long, which was one third of its height. The height of the mlcrounevennesses was
the same as on cylindrical rods.
In the course of the tests we determlned the mathematical expectation ~c or ~ and the
confidence intervals for it ~cmln, ~cmax' The admissibility of normal distribution of the
ultimate strengths is shown on the example of glass TKII4 and glass K8 (Fig. I). An analogous
dependence was also found to apply to the other kinds of glasses, as well as to optical pyro-
ceram SOIISM in axial tension and compression [3].
To ensure the reliability of the obtained results, in determining the ultimate strength
o c we tested 30 specimens, and for ~Cc 20-25 specimens. The sample in loading prismatic
rods, and also of specimens of the second batch, was one-half to two-thirds smaller.
Most of the cylindrical specimens (first batch) were made and tested at the Institute
of the Strength of Materials, Academy of Sciences of the UkrSSR. The rest of the specimens
(second batch) were made under industrial conditions. Between production and the tests more
than three years elapsed. The object of testing these batches of specimens was to evaluate
the stability of the mechanical properties of optical materials in lengthy storage, and also
to determine the effect of traits of the production technology under laboratory and indus-
trial conditions on the experimental data.
The results of the investigations are presented in Tables 3-5 which also contain the
upper and lower confidence limits at a confidence level a = 95%.
It was established that the strength of optical glass in uniaxial compression is one-
third to one-half lower than the strength of hlgh-strength technical glass, e.g., glass 13v
(o c = 2200 MPa [i]). Moreover, the test results are characterized by lower stability. The
sample variation coefficient in the investigation of samples containing 30 specimens of op-
tical glass attains 10-15%, which is 50-100% more than with glass 13v or pyroceram STL-10.
This requires higher safety factors for strength in the design of highly stressed products
of the materials in question.
1127
TABLE 3. Strength of Optical Glass under Axial Compression
Brand of glass
LK5
First batch
Second batcb
K8
First batch
Second batch
TI<2~14
F101
First batch
Second batch
FI
TFI01
TFI0
Pyroceram SOllSM
First batch
Second batch
TABLE 4.
Glass
%, MPa
1210
1330
1395
1330
1410
1180
1050
850
1155
1000
2005 [3 I
2020
~ mtn.MPa Oc max, MPa v c , %
Size of sample
of specimens
)n
30
l1
30
11
30
30
12
I0
30
30
~atio of ult i-
Imate strengths
~_.E. ~of second ~'nd 10--3, m
[first batche~ of
specimens
56,6
62.2
54,9
51,6
43,7
33,6
29,9
24,2
24.8
21,5
1180
1270
1330
1250
1335
1140
99O
1~o
960
1950
1845
1240
1390
1460
1410
1485
1215
III0
1215
I035
206O
2190
6,8
7,0
12,2
8.6
14,2
8,7
9,0
13,3
lO, l
13,7
17.2
99
10
80,8
81.3
I , l
0.95
0.90
1.0
Strength in Uniaxial Compression ~Cu of Prismatic Specimens of Technical
Material
Glass LK5
Glass K8
Glass TK3
Glass F1
Glass F101
Pyroceram SOl15M
Oco . MPa
1660
1070
1210
860
1430
1620
~
MPa
1415
98O
1040
75O
1335
1475
n
Ctl
MPa max
1905
1160
1380
970
1525
1765
%,%
20,1
13.4
22.9
17.5
9.1
I0.6
H, pcs.
10
12
13
10
10
10
OC u
0 C
1.35
0.78
1.01
1.20
0,81
v u
I" C
2 96
I. 10
2,02
0.78
TABLE 5. Contact Strength GCc in Axial
Compression of Optical Glass by Plane
Metallic Supports
Characteristic
Oce , MPa
OCcmi n. MPa
Occma x. MPa
Vc, ~0
n, pCS.
OCc/O C
VC/VO c
565
5O5
625
930"
820
1040
22.3
20
0.46
1,6
22.0
20
0.4
1.6
545 [ 355 320
I
530 1340 254
560 1 37O 386
35,4 I 48'81 50
0.3 0.32
3.0 5.6 5
*Obtained on cubic specimens with edges
8 ~m long.
The results of the investigation (Table 3) showed that the ultimate strength of optical
glass depends on its chemical composition. Regardless of the chemical composition, better
characteristics (from 1200 to 1400 MPa) correspond to the crown glasses TKII4, K8, LK5. The
experimental data (Tables 2 and 3) and the literature data [i0] on the strength of glass
LK5 practically coincided. The lowest strength (from 800 to I000 MPa) is found in the lead-
containing compositions FI, TFI0. The strength of the investigated types of glass depends
on the specific weight of the material. When it is necessary to ensure minimum weight of
a structure, an important characteristic of the material is its specific strength, described
by the ratio Oc/Y. This parameter is equal to i15"I0 s m for pyroceram STL-10 and 88.10 s m
for glass 13v. For optical glass this parameter lies within the limits (21.5-56.6)'i0 s m
(Table 3), and it is functionally correlated with the specific weight by the dependence
shown in Fig. 2.
1128
~c 7-' 10"3' m
65
5 0 ~ Q
20
0- -1
e--2
~--~.
[3-6
A
3 ~, 1. ,o -~, N/rn 3
%i%
0.40
0.35
, /
0.30 ,,
1.00 1,25
S
[3--3
".5
[50 ~c IO-s, MPa
Fig. 2 FiR. 3
Fig. 2. Dependence of specific strength o c in axial compression
on the specific weight y for optical glasses LK5 (i), K8 (2),
TKII4 (3), FI (4), TFI01 (5), and TFIO (6).
Fig. 3. Dependence of the ratio of the mean level of rupture
stresses OCc in loading by smooth metallic supports to ultimate
strength o c on ultimate strength o c for optical pyroceram S0115M
(i), glass TKII4 (2), K8 (3), FI01 (4), and TFI0 (5).
When we compare the characteristics of strength of optical glass and pyroceram S0115M
(Table 3), we have to note that the strength of the latter is 1.5 times as high as the
strength of crown glasses, and in specific strength pyroceram S0115M is comparable to glass
13v (Oc/y = 81"103 m).
According to the data of Table 4, the strength in uniaxial compression of prismatic
specimens on an average for all tested materials is comparable with the strength of cylindri-
cal specimens. Howeger, with equal size of the tested batches (10-15 specimens) the scatter
of the experimental data on prismatic rods is 1.25 to 1.35 times greater than on cylindrical
specimens. This is apparently due to features of machining, possibly to methodological
deviations and to the shape itself of the specimens as a structural factor.
In view of the above, and also in view of the fact that for some glasses the test re-
suits obtained with prismatic specimens deviate considerably from the results obtained with
cylindrical specimens, not only in small batches but also with more representative samples,
it is best in evaluating the compressive strength of glass and pyrocerams to test cylindri-
cal specimens with equal height of the microunevennesses of the lateral surfaces [2].
The possibility of improving the reliability of determining the strength of materials
of the given class in uniaxial compression on cylindrical specimens was noted in tests of
samples of different size of glasses FI01, KS, LKb, and pyroceram S0115M. With a confidence
level a = 95%, the confidence limits for o c of the first and second batches practically over-
lap, and the largest difference in values of ~c does not exceed 10%.
Consequently, possible deviations in the technological regimes of machining cylindrical
specimens under laboratory and industrial conditions to the same height of microunevennesses,
and even lengthy storage (more than three years) of specimens under normal conditions, do not
have a noticeable effect on ultimate strength in uniaxial compression of glass and pyroceram.
The chemical composition has a noticeable effect, too, on the contact strength of opti-
cal glass in compression of specimens by plane supports (Table 5). On the whole we find the
same relations as those noted in the study of strength in uniaxial compression. Higher
values of ~c are found in crown glass TKII4 and K8. Thus, materials with high strength in C
unlaxial compression are also characterized by higher contact strength; this is also confirmed
by the data on pyroceram S0115M (Table 5).
It is important that, whereas in technical glass and pyrocerams ultimate strength in
contact compression by plane supports ~Cc amounts to approximately 50-65% of the value of
~ in glass K8 and TKII4 it does not exceed 40% of this 9alue, and in low-strength flint
glasses it goes down to 30% of o c. Yet for optical glass and pyroceram the ratio ~cc/~c
is correlated by a functional dependence with ultimate strength in axial compression which
may, in the first approximation, be approximated by a straight line (Fig. 3).
1129
It should be pointed out that in optical glass the relatively low level of contact
strength is combined with a considerable variation coefficient: from 22 to 50%. This
shows that the problem of devising high-strength joints of components that are reliable
in compression, when the components are made of optical glasses and heterogeneous materials,
is more complex than in elements of shells made of technical glass.
CONCLUSIONS
I. The strength of optical glass in uniaxial compression is one-third to one-half
lower than the strength of high-strength technical glass, e.g., glass 13v, the sample
variation coefficient is 50 to 100% larger, and therefore a higher safety factor is re-
quired in designing highly stressed components made of the given materials.
2. The strength of optical glass under axial compression, and also under loading of
specimens by smooth metallic supports, depends to a considerable extent on the chemical
composition, and in glasses containing lead oxide Pb02 it attains minimum values (800-
i000 MPa).
3. The strength of prismatic specimens of optical glass and of pyroceram does not
differ by more than 10% from the strength of cylindrical specimens, whereas the scatter of
experimental data for the former is 1.25 to 1.35 times higher than for the latter.
4. The ratio of the mean level of rupture stresses in compression of optical glass by
smooth metallic supports to their ultimate strength is correlated by a functional dependence
with the ultimate strength in axial compression which in the first approximation may be ap-
proximated by a straight line.
5. Strength in axial compression, and also the upper and lower confidence limits with
a confidence level a = 95%, are not substantially affected by peculiarities of the produc-
tion technology of cylindrical specimens under laboratory and industrial conditions as to
the equal height of microunevennesses or by storage of specimens after production under nor-
mal conditions for three years or more.
LITERATURE CITED
i. G. S. Pisarenko, K. K. Amel'yanovich, Yu. I. Kozub, et al., The Structural Strength of
Glass and Pyrocerams [in Russian], Naukova Dumka, Kiev (1979).
2. G. M. Okhrimenko, Yu. M. Rodichev, V. L. Stepchenko, and L. R. Gaevskaya, "The effect
of the state of the surface on the strength in axial compression and bending of optical
pyroceram S0115M," Opt.-Mekh. Promyshlennost', No. i, 22-26 (1982).
3. A. I. Busel', L. R. Gaevskaya, Yu. N. Evplov, et al., "The strength of pyroceram S0115M
and of its Joints on the basis of optical contact," Probl. Prochn., No. 3, 67-71 (1983).
4. V. A. Pushechnikov, V. P. Maslov, Yu. M. Rodichev, et al., "Selection of the parameters
for treating optical pyroceram according to the results of testing its strength under
conditions of bending," 0pt.-Mekh. Promyshlennost', No. 4, 37-40 (1978).
5. S. M. Kuznetsov and M. A. Okatov (eds.), Handbook for Technologists in Optics [in
Russian], Mashinostroenie, Leningrad (1983).
6. Catalog of Technical Pyrocerams [in Russian], Stroiizdat, Moscow (1969).
7. ~ V. Ivanov, "The effect of the state of stress on the strength of glass K8," Opt.-
Mekh. Promyshlennost', No. i, 72 (1978).
8. A. V. Ivanov, "Methods of determining the mechanical strength of optical materials,"
Opt.-Mekh. Promyshlennost', No. 3, 59-67 (1973).
9. F. K. Volynets, "Production methods, structure and physicochemlcal properties of opti-
cal ceramics," 0pt.-Mekh. Promyshlennost', No. 9, 48-61 (1973).
i0. M. V. Kas'yan and G. S. Minasyan, "The problem of cutting technical glass," in: Collec-
tion of Scientific Papers of the Erevan Polytechnic Institute, Aiastan, Erevan (1977),
pp. 3-11.
ii. G. S. Pisarenko, G. M. Okhrimenko, and Yu. M. Rodichev, "Selection of optimum conditions
of loading glass and pyrocerams in compressive tests," Probl. Prochn., No. 12, 3-10
(1974).
12. S. S. Solntsev and E. M. Morozov, Failure of Glass [in Russian], Mashinostroenie, Moscow
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