STRENGTH RESERVES IN USSR MACHINE CONSTRUCTION

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600350045-3
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 5
• Document Creation Date: December 22, 2016
• Document Release Date: August 19, 2011
• Sequence Number: 45
• Publication Date: October 2, 1950
• Content Type: REPORT

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CLASSIFICATION CONFIDENTIAL Vo~~~~~~ ~ ~~~
' CENTRAL INTELLIGENCE AGENCY REPORT
iNFORMA'i ION FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
COUNTRY USSR
SUBJECT Scientific ~ Minerals, metals
HOW
PUBLISHED Monthly pe. iodical
WHERE
PUBLISHED Moscow
DATE
PUBLISHED Mar 1948
LANGUAGE Russian
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SOURCE Vestnik Mashinostroyeniya, No 3, 1948,
STRENGTH RESERVES IN USSR MACHINE CONSTRUCTION
It has slready been pointed out (Vestnik Mashinostroytniya, No 11-12, 1943,
i,p 6?r16) that the technological processes of Jrschine building can provide an
increase in the strength indexes of machine construction materials and, conse-
quently, a fuller utilization of them.. It must be emphasized that the basic
means for further increase in the endurance of the product involves the use of
the .plastic deformation and internsl stresses which arise in slmost every tech-
nological procesu.
In the casting induE:.ry, not introducing any new alloys, the endurance of
cast products can be significantly increased by regulating the internal stresses
in them,
The most essential possibility of increasing the strength of steel by forg-
ing and rolling is the close control of finishing temperature for these opera-
tions Finishing them at relatively low temperatures in the range of Ara - Arl
or even lower can significantly increase the indexes not only of static strength
but of cyclic strength.
m,._ ..+__,.,.+ti, t.,a_a..oa ?f voi~~~ aPa__ma mar?P nut~mattc bv_ electric-arc weld-
~..~ .,,,.....o.... _..
ing under flux a_re incomparably higher than those of seams made by hand electric-
arc welding.
Cold working by cutting brings important changes into the surface layer of
the part which greatly influence the strength of the part as a whole. Therefore,
the establishment oY cutting parameters should be based, in:.an nu}nber of a:ase~,
not only on economic considerations but also on requirements applied to the part
from the viewpoint of its reliability.
Finally in heat treating, done to i~pa~rt definite strength characteristics
to the part, merely controlling the physicochemical and structural changes in
the metal frequently does not lead tc the desired results. The sul:cess of heat
STATE
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DATE OF
INFORMATION 1948
DATE DIST. ~ G~ 1950
SUPPLEMENT TO
REPORT NO.
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treatment of the part cannot be considered fully attained if only the neces-
sary structure is obtained in metals. It is necessary that this structure be
accompanied by optimum internal stresses. Only then will the maximum strength
cf the part be attained
However, technological possibilities for increasing the strength of ma-
chin= construction materials are not limited to these examples. Strength re-
sources in machine construction are =ignificantly greater in the fiel3 of tech-
nology as well ss in the construction field, Soae of these reserves will be
censi.dered below,
Strewth-at Hi~h_Te_mperatures
The problem of high-temperature strength is highly significant in machine
construction. The search for creep-resistant steels and slloys is being coa-
di.a.ed effecti~rely in all countries. At the same time, the strength possibili-
ties of recognized 'types of structural steel are not being fully utilized.
The graphic results of creep testing of molybdenum steel may be taken as
an example. On the ordinate axis were 3otted the stresses producing a one-:
percent deformation over a perio3 of 100,000 hours; abscissas represented tem-
perature Each o? the curves relates to a molybdenum steel xith a definite
grain size shown by the ASTM number (2 to 8) for each curve. !t is evident
that for each temperature they? is an optimum gain size which assures the best
creep resistance. Let us examine t?he creep resistance of a molybdenum steel
at a temperature of 540 degrees, which is of great? interest at the moment to
power-machine constructors. It is not difficult to see that a rat of. creep
of 10'"5 percent per hour can cruse a stress of 10 kilograms per square milli-
meter if the steel grin number is 3, and about 2 kilograms per square milli-
met~r if the grain nut.ber is 8_ It is clear that the first of these steels
f,No 3) can 'be used in turbine construe+. ion with working temperatures of 540
degrees, while the second would rot be good at the indicated temperature.
Metallurgists have not yet prepared a steel with a rigid grain-size specifi-
cation.. Consequently, machine constructors are not in a position to utilize
fully the strength properties of molybdenum steel at high temperatures. This
is definitely a strength reserve.
The rPSUlts of creep testing for three steels which have fairly similar
composi'ions were plotted on a graph. One of them was prepared in the acid
open-hearth furnace, the second was made by the basic open-hearth method, and
the third in the basic electric furnace. These results show that the method
of preparing the steel has a substantial influence on its creep resistance.
The best of them is the basic steel, especially the one made in the electric
furnace. However, this possibility also is not widely emplc?ed by metallurgists,
even though it offers a very significant strength reserve.
The relaxation o_? two types of steel was studied --.low carbon steel with
0.15 percent centigrade and medium carbon steel with 0.8 percent centigrade ~-
depending on the original structure. It must be noted that high relaxation
resietanr_e generally conditions high creep resistance. Therefore, these re-
sults of the relaxation tests have a much greater significance. They indi-
cate the great influence oP tiie original structure of the. steel on the re-
laxation process (and consequently on creep). It must be noted that the
least durable in the relaxation process is the sorbita structure, and the
most durable structure is~the lamellar pearlite. It is a well known fact
that steel with a.sorbitic structure is used most often for construction
parts, while steel with a Lamellar pearlite structure is rarely employed;
OONr'IUENTIAL
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CONFIOENTiAi
i-. e., the direct opposite of wha*, should be used. It appears also that a low-
carbon steel at high tempera+,uree is ,:~s*. resi^tant if it has large grains; at
lower temperatures, fine-?grained steel is preferred., These interesting facts
also reveal a strength reserve for machine construction.
Surface Stren~ztheni~f a Metal
Surface strengthening of a metal by carburization (cementation), nitrid-
ing, heating with high-frequency Curren+,s followed by rapid quenching (high-
frequency hardening), and cold hardening the surface by way of shot blasting
or roller burnishing, are widely known. However, the results obtained by these
operations are extremely varied. Therefore, it is natural that constructors,
unable to depend on the stability of these technological processes, design the
parts according to the lowest strength indexes. Such losses are very consider-
able.. By burnishing, the cyclic strength can be raised from 100 to 120 - 250
units.
The high-frequency process sometimes does not increase the cyclic strength
of the Hart and at other times raises it 100 percent and more as compared to
the initial state. Even established operations such as nitriding and cementa-
tion show a rather large variance in the results of strength determination.
Surh a variance is explained by operations which are not fully developed or by
inadequacies in the precision of technological operations.
~~he results of measuring the fatigue limits in the bending and twisting
of various materials after shot blasting show how little developed is the indi-
cated process, and how greatly the data for very similar types of steel vary
because of this. For example, in the case of two very similar steels, the in-
crease in the endurance of one is 27 percent while for the c~her it is 11 per-
cent. For other types, this difference is even greater.
From what has been said, it follows that the strength of the part can be
increased significantly by a more detailed development of the technological
processes and the development of more precise ways of conducting them.
The strength of the part, especially cyclic strength, is sometimes lowered
very much by construction factors? This is illustrated ay the data tabulated
below The tensile strength is taken as the 100-percent index. Depending on
the type of steel, the fatigue limit in bending is 55 to 75 percent of the ulti-
mate strength. The fatigue limits were established for smooth samples with a
comparatively small diameter (10-15 millimeters). The fatigue limits (endur-
ance) of the parts, prepared from the same types of steel, are indicated as
percentages of the ultimate tensile strength.
Fatigue Limit
(in ~, of ultimate tensile strength)
10.5
Diesel crankshaft (journal diameter 24.5: mm)
7.0
RR car axle with pressed wheel (d equals 190 mm;
12.2
Straight shaft with pressed hub (d equals 40 mm)
20.0
Straight shaft with spline-fixed hub (d equals 30 mm)
13.6
Gear wheel
9.0
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Fatigue Limit
(in ~ of ultimate tensile strength)
Threaded bolt (d equals 1 1~8 :in)
7.5
Bolt joir..t of ?wo No 20 I beams
6.8
Welded joint of two No 20 I beams
11.2
Riveted joint of plate
21.4
Welded joint of plate (cross sectional area F equals
24.0
2,660 sq u,m)
I+, is obvious just how great the losses in cyclic strength in the parts
are in comparison with the endurance of laboratory samples. The question
arises whether these losses are avoidable and whether they can be eliminated
or reduced. If they are unavoidable, then ways for their elimination need not
be sought; if they are avoidable, there is a strength reserve of significant
value .
The significant drop in the +.ndex of cyclic strength is explained by two
effects (e) the scale factor, and (b) stress concentration.
The scale factor has been studied, buc not to a degree commensurate with
its significance. However, there are two criteria which we can use. One of
them, Leyer"s, establishes a decrease in the fatigue limit almost b?r half with
an increase of the diameter of the part from 10 to 200 millimeters. The sec-
ond criterion, Peterson and Faul?gaber?s, limits this decrease by a maximum
of 20 percent.. Not dwelling here on the causes of tiie scale factor (they are
still very questionable), it must be noted that most constructers, as long as
a solution is not found, will use the lower curve (Leyeros) in their calcula-
tions as the more reliable one, whereas experimentally accumulated data a?e-
sporis more to the upper curve. Consequently, the difference in the ordinates
of both curves is a strength resource and it should be utilized as soon as
possible.
Stress concentration in t?he part can be eliminated in various ways. One
of these, which is very effective, infers that for a Hart with a form twat
" brings about stress concentration, a metal is used wi a high index of the
coefficent of sensitivity to notching
Y ~o-w
where E ie the modulus of elasticity,~w the cyclic toughness, and ~ w the
fatigue limit at tensicn=compression.
gtr?sa concentration can be lowered effectively by selecting material
with low sensitivity to notching (or with high cyclic touohnece). In prac-
tice, however, this is not done because cyclic toughness has been otudied
very little. The accumulation of data on the cyclic ?toughness of machine
construction materials will permit utilization of these very great strength
resources.
COt~F~D~-~ ~ ~~~
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Unsolved Problems of Metal Strength
To a great degree, the development of contemporary machine construction
is limite3 by unsolved problems of metal strength. Modern gas and steam tur-
bines, automobiles and aircraft engines, steam locomotives, elrctric locomo-
tives, and the like could be significantly improved if the constructors could
increase the allowable stress in improtant units.
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:ia-~n:za?d:: ~. ci~?.cht?:,.+ r:!;~,:,t?:u~t.nr?; -.ri;l stlrn?late thn development of new
alloys aith hight+r st,r.r=natl? t?~;ex!~::, Hn?aevera the 3evelopment of machine
design cannot be based only :,r. shy creation of new, more perfect alloys. It
is still necessary to combine the use of existing machine-construction mate-
rials with maximum efficiency.
The posslbilities roc mar.:nl.ne constructors are not limite3 by the exemples
cited. A thorough stu~~iy of the probllems of strength in all its ramifications
is the actual problem to b,' se.Lved and that will bring worthwhile results. Ma-
chine constructors should 1ea~~n to Qs+,ablish exactly the actual stresses in
the machine parts, and. quickly and reliably determine the actual stress dis-
tribution in the parts by r.?alculeting not only elastic deformations but plas-
tic deformations as well. Machine constructors ahotil.d develop new strength
:-baracteristics for metals whi.r.h would be more exactly reflected in the behav-
irr of the metals in service. They should know how to establish the change of
strength characteristics and stress distr'bution under operating conditions
which cause in the metal internal processes of a physicochemical nature. Ma-
~hine constructors shoulri be able to determine the influence of technological
processes on strec?~th indexeQ and to develop technological processes with rer
spee.t to increases in the strength i?!dexAS. These are some of most trgetrt-prob-
leme of mach-.ins construction. For example, the solution of the problems of
static strength (a complex stre.ssFd state, brittle tensile strength, etc.) will
permit ar, increNSe of the vrrki.nQ Ftresses by 30-50 percent. The solution of
a series of problems ^n cvc]ic r:nr1!trance will allow an increase of the desl,3n
stresses by 2~~3 or mc>.re times, s.nd in relation tc the relaxation and. creep of
metal. by 4w5 and more +..imes.
The tima for establisbinp?, vex?1ouQ strr..ngt.h characteristacs varies con-
side:rabl.y. The time to dot;=rmi.ne t.h> r_haracteristic of static strength amounts
to minutes (or tens qr };u~!dr~ds of minutes); the determination of fatigue strength
requires h!:ndreds of hours; and. fiir c.?eep and relaxation tests the time is ex??
pressed in thousands of hours. Consequently, factors which assure a great in?~
crease of design str~eses also require greater consumption of time to establish
they strength charsctei?istir_s.
;t
F'inall.y, ea:amiration cf *.?he relnt've extant of utilisation of the methods
fo.r thsting +,he strength of?mei:als r~?u?als a complete disproportionality. That
method of testing metals vhfr_h requires the longest period of time to establish
strength r_haracteriati.es an..d which promises the greatest increase in allowable
stresses has not y=.t received. proper attention. It is clear that here, also,
there are: very effect,ise endurance reserves, the use of which can affect favor-
ably t.hr'. develc.pme.nt of rrndFr+_! ma.r?.liine c:onstru:tion.
CQNFIA~~ r ~~~,
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