CONTRACT(Sanitized)PRELIMINARY TECHNICAL REPORT ON ITEM 1. SUBMICRON MEASUREMENT ERROR ANALYSIS

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A002900020039-8
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 10
• Document Creation Date: December 28, 2016
• Document Release Date: August 30, 2005
• Sequence Number: 39
• Publication Date: November 9, 1964
• Content Type: REPORT

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November.-..9, 1964.
Contract
Preliminary. Technical Report
on
Item.1. Submicron Measurement Error Analysis.
Item 1 Work Statement: Evaluate the physical and
metallurgical properties of materials used in measuring
engine construction to determine comparative suitability
to submicron measuring. Materials to b2 considered are:'
Meehanite, steel, granite, aluminum, magnesium, and
glass.
Submitted by:
Declass Review by NGA:
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Task II. Item 1. Preliminary Technical Report.
The materials under study are:
1. Meehanite
2. Steel-
3. Granite
.4. Aluminum
5. Magnesium
6. Glass
The materials may be more precisely defined as follows:.
Meehanite. A high quality grey cast iron. The composition
.and properties are much more closely controlled than
common structural cast iron. Meehanite is available in
a variety of. grades and the properties vary widely with
grade.
Steel. Available in an enormous variety of alloys. For
our purposes a low carbon, wrought, structural steel is
,representative.'
Granite. Natural quarried granite is available in pink,
grey, and black. Black granite is reportedly the hardest,
,most uniform, and best quality so we have used it in the
evaluations.
Aluminum. Tooling plate is specially formulated and
a ricated for high stability and low residual stresses.
The cast type 300 is slightly better than wrought-type.
Therefore,~the properties of Alcoa type 300 cast aluminum
tool and jig plate have been used in the evaluation.
Magnesium. Dow Alloy AZ 31 B is specially fabricated in
tooling plate with high stability and low residual stresses.
Alloying elements are 1% zinc and 0.45% manganese.
.Glass. Fuzed quartz was selected as the glass best suited
to measuring engine applications.
The properties covered in detail in this preliminary
.report are:
1. Modulus of elasticity (stiffness).
2. Density (weight).
3. Ratio of stiffness to weight.
4. Thermal conductivity.
5. Thermal coefficient of linear expansion.
6. Thermal capacity.
7. Ratio of thermal expansion to thermal
capacity. . .4
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is
1. Modulus of Elasticity'(stiffness), E.
The modulus of elasticity is usually called Young's
modulus and is a measure of the inherent-stiffness of
a material in tension or compression, It is the amount
of force per unit area (stress in lbs/inch2) required
to affect a given deflection (strain in inches/inch).
Since strain is a dimensionless ratio, the units of the
modulus are in lbs/inch2.
Typical values are:
Steel 29.0 x 106psi
Meehanite (cast iron) 23.0 to 17.5 x 106psi-
Black Granite 13.6 to 8.4 x 106psi
Aluminum tooling plate 10.3 x 106psi
Magnesium tooling plate 6.5 x 106psi.
Fuzed quartz .4.4 x 10 psi
Steel is the stiffest of the common structural materials.
The stiffness of Meehanite cast iron is different for
the different grades but is consistent within a given
grade. Granite being a natural unrefined material, the
stiffness varies with the composition of the material as
quarried. .
2. Density weight), p
The lighter weight materials, are desirable for structure
in order to reduce the total weight of a machine and
to reduce deflections of individual members due to their.
own weight.
Typical values are:
Magnesium tooling plate
.064 lbs/in3
Fuzed quartz
.079 lbs/in3,I
Aluminum tooling plate
.101 lbs/in3
Black granite
.110 lbs/in3
Meehanite cast iron
.257 lbs/in
Steel
3
.283 lbs/in
3. Stiffness to Density Ratio, E/P"
Normally, the lighter weight materials also have a lower
stiffness modulus. Since it is desirable to have high
stiffness and low weight fora given structure, the
ratio of these two properties will give a figure of
merit for the material. The units of the ratio are:
Youngz's Modulus irr lbs/in2 = inches
Density in lbs in- .
Typical values of E/f' are:
-2-
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Steel
102
Aluminum tooling plate
102
Magnesium tooling plate
102
Black Granite
77
Meehanite cast iron
68
Fuzed quartz
56
x 1066 inches
x 106inches
x l06inches
to 123 x 106inches
to 89 x 106inches
x 10 inches
This interesting criterion shows that the design of a
rigid structure will have the same weight regardless of
whether steel, aluminum, or magnesium are selected for
their inherent properties. Designing for a maximum
stiffness-to-weight ratio, as required for most optical
structures, is entirely different than designing for a
maximum strength-to-weight ratio as is done in aircraft
structure. Note also that granite, Meehanite, and quartz:
are less desirable materials from the standpoint of
stiffness-to-weight ratio.
4. ? Thermal Conductivity, k.
The ability of a material to achieve a uniform temperature
distribution throughout its volume in a minimum time is
determined by its thermal conductivity. A high thermal
conductivity is desirable if distortions of a structure
due'to a change in environment temperature are to be.
minimized. The thermal conductivity in cgs units-is
the amount of heat in calories which is transmitted per
second through a plate one centimeter thick across an
area of one square centimeter when the temperature dif-
ference is one degree centigrade. The thermal conductivity
of pure copper, which is often used as a reference, is
approximately 1.0 in cgs units.
Typical values are:
Aluminum tooling plate
.25 to .30 cgs
Magnesium tooling plate
.18 cgs
Steel
.15 cgs
Meehanite cast iron
.14 cgs
Fuzed quartz
.03 cgs
Black Granite
.005 cgs
5. Thermal Coefficient of Linear Expansion.
The amount that a bar of material will expand linearly
under a specified temperature change is determined by the
thermal coefficient of linear expansion. The units are
expressed as strain in inches/inch per degree centigrade.
A low coefficient is desirable to maintain dimensional
stability of a structure as the temperature of the
structure varies.
-3-
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Typical values acre:
Fuzed quartz
0.5
x 10-6 in/in/oC
Black Granite
5.4
x 10 in/in/ C
Aluminum tooling plate
12.0
x 10_6 in/in/aC
Steel
12.0
x 10?6.in/in/oC
Meehanite cast iron
12.0
to 12.4
x 10_6 in/in/oC
Magnesium tooling plate
26.8
x 10 in/in/ C
Since granite and Meehanite have roughly half the thermal
coefficient of linear expansion of steel and aluminum
and less than one-quarter that of magnesium, they are
much more desirable in this respect for optical structures.
Fuzed quartz is most desirable of all by a factor of lO
and more.
6. Thermal Capacity.
The'amount of heat required to raise the temperature of
a unit mass of material one degree C. is determined by
its thermal capacity. The thermal capacity of water,
which is the standard, equals one. The units are in
calories per gram. This can be converted to BTU per
lb or watt-seconds per lb if desired. Heat capacity is
important when heat is being pumped into a structure.
for example, by a motor. or a lamp. For optical structures
it is desirable that the thermal capacity by high so
that it can absorb heat with a minimum of,temperature
rise.
Typical values are:
Magnesium tooling plate
Aluminum tooling plate
Fuzed quartz
Black Granite
Meehanite cast
Steel
0.246 cal/gram/ooC.
0.214 cal/gram/oC.
0.188 cal/gram/0C.
0.172 cal/gram/o C.
0.119 cal/gram/oC.
0.115 cal/gram/9Q.
7. Ratio of Thermal Coefficient of Linear Expansion
To Thermal Capacity.
The ratio of thermal. expansion to thermal capacity in-
dicates the amount of strain produced in a material by
the absorption of a unit amount of heat. The units are
strain in inches/inch divided by calories/gram which
equals gram/calories..
The ratio is a truer indication of desirability of a
material than either thermal expansion or thermal
capacity taken alone. A low ratio is desired so that .a
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maximum amount. of heat can-be absorbed with a minimum
of strain resulting in the structure.
Typical values per gram of material.are:
Fuzed'quartz 2.7 x 10-6 in/in/cal
Black Granite 31.4 x 10_6 in/in/cal
Aluminum tooling plate 56.0 x 10_6 in/in/cal
Meehanite cast iron 100.9 x 10_6 in/in/cal
Steel 104.2 x 10_6 in/in/cal
Magnesium tooling plate 109.0 x 10 in/in/cal
Quartz clearly has the best thermal properties while
'Meehanite, steel, and magnesium"are all about the same.
Black granite is about three times as thermally stable
and aluminum is about twice as thermally stable as the
other metals. Thus, the rankings of desirability have
changed compared to that obtained by considering only.
the-thermal expansion coefficient.
8. Other Properties.
The strength of the materials under study is not a major
consideration. In a structure designed for maximum
rigidity the stresses are low.
The ductility (or its inverse,.brittleness) of the materials
is important as related to manufacturing ease and rough
handling in use. Manufacturing ease will be discussed
.separately.
The damping characteristic of the materials is of con-
siderable importance in optical structures, but data are
essentially unavailable. A high damping factor is de-
sirable so that the material will absorb or attenuate
vibrations and prevent them from ringing through the
structure. Certain construction techniques can be used
to'provide a dead or well damped structure. Construction
techniques will be discussed separately at a later date.
One of the attributes claimed for magnesium, for granite,
and'for Meehanite is their high damping coefficients.
Steel, of course, rings like a bell. Since this charac-
terisitic is of importance, a further search will be
made for data., .
Corrosion resistance is also an important characteristic.
Quartz and granite do*not corrode under normal laboratory
conditions and require no protection. Aluminum also
requires no corrosion protection for measuring engine
application. Its oxide forms a hard, tough impervious.
coating. Steel and Meehanit.e corrode readily and con-
tinuously unless well protected by paint, oil, or grease..
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Magnesium is highly susceptible to corrosion and difficult..
to protect. Dow has developed special finishes and treat-'
ments.for corrosion protection of magnesium alloys. It
is almost impossible, however, to protect clean working
surfaces and the magnesium oxide is a"fine; white, loose
powder which can contaminate bearings and sliding surfaces.
Dimensional stability of the materials is of great importance
but data are almost non-existent. Quartz and granite have
excellent dimensional stability. For the metals, good
stress relief treatments are essential to achieve good
dimensional stability. Of the metals, cast iron is con-
sidered to have the best dimensional stability and
aluminum-jig plate next. The standing of steel and
magnesium tooling plate is undetermined. Further search
will be made for data on dimensional stability.
9. Fabrication.
uartz is a non-structural material because of its high
cost and extreme difficulty of fabrication. It can be
shaped only by casting, sawing, grinding, sand blasting,
or chipping. It can be joined only by clamping or fuzing.
It cannot be threaded, riveted, or bolted without special
precautions. It cannot be machined or welded.
Granite has all the same limitations and it cannot be
cast. Its cost is so low, however, that it is economic
to use it in large blocks as in surface plates.
Magnesium can be readily cast, machined, sawed, threaded,
riveted, and bolted. It is seldom welded and in machining
special safety precautions must be taken. Its cost is
higher than the other metals, and it is more expensive
to fabricate.
Meehanite can be cast, machined, and joined by all common
melds. Due to abrasive tool wear, machining is a
little slow and, therefore,- a bit expensive. The basic
castings, however, are inexpensive.
Aluminum can be cast, machined, and joined by all the
common methods. The material cost is more expensive
than steel or cast ironibut machining is fast and cheap.
Steel is the most common structural material and generally
the cheapest. It can be cast machined and joined by all
common. methods.
10. Summary.
For design of high stiffness to weight structures, as
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is required in most optical equipment, steel, aluminum,
magnesium and certain formulations of Meehanite are
equally efficient. The light weight advantage of mag-
nesium and, aluminum disappears when the modulus of
elasticity is taken into account (see column 3 of Summary
Tabulation). Magnesium is least desirable when-its
corrosion and cost are considered. Steel is most
desirable from its cost and ease of fabrication, but
aluminum has some advantage in its very high thermal
conductivity which tends to reduce thermal distortions.
When lamps and motors are involved, they act as localized
heat sources and pump heat into the structure causing
temperature gradients. Under such conditions, aluminum
is the most desirable structural material.
When the principal limitation is space, not weight,
steel is clearly the most desirable.
.For design which requires optical flatness and straight-
ness and nb thermal expansion, quartz is the most de
sirable. Granite is second but is not as good as
quartz by a factor of 10. The cost and availability of
quartz restricts its use unless the design can be arranged
to use only small sections. Aluminum is third but is
.not as good as granite by a factor of 2. Meehanite,'
steel, and magnesium are-all about the same, but are not
as good as aluminum by a factor of 2.
11. Additional Work.
Further data on damping, ductility, and dimensional
stability will be obtained and presented in a later
report. The numerical effect of material properties-!
on submicron.'measuring will be investigated and the
design approach necessary to.maximize the advantages
of the materials will be considered.
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Summary of Tabulation of Physical and Metallurgical Properties
of Six Materials Ranked in Order of Their Desirability
for a Submicron Measuring Machine .
1.
Modulus of
2.
Density
3.
Stiffness/Weight
4.
,thermal Conductivity
Elasticity
(Weight)
E/,.
(Stiffness)
E
106 psi
lbs/in.3
106 inches
cal/sec/cm/cm'/'c.
1.
Steel 29.0
1.
Magnesium .064
1.
Steel 102
1.
Aluminum .25 to .30
2.
Meehanite 23.0 to 17.5
2.
Quartz .079
1.
Aluminum 102,
2.
Magnesium .18
3.
Granite 13.6 to 8.4._
3.
Aluminum .101
1.
Magnesium 102
3.
Steel .15
4.
Aluminum 10:.3
4.-
Granite .110
1.
Granite 77 to 123.
4.
Meehanite .14
5.
Magnesium 6.5
5.
Meehanite .257
2.
Meehanite 68 to 89
5.
Quartz .03
6.
Quartz 4.4
6
Steel .283
3.
Quartz 56
6.
Granite .005
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Summary of'Tabulation of Physical and Metallurgical Properties
of Six Materials Ranked in Order of Their Desirability
for a Submicron Measuring:
chine
5.
Thermal Coefficient of
6.
Thermal Capacity
7.
Ratio Thermal
xpansion/
Linear Expansion
Thermal Capacit
y
10-6 in./in./?C
cal. /gram
10-6 in./i
1.
Quartz
0.5
1.
Magnesium
.246
1.
Quartz
2.7
2.
Granite
5.4
2.
Aluminum
.214
2.
Granite
1.4
3.
Aluminum
12.0
3.
Quartz
.188
3.
Aluminum 5
6.0
3.
Steel
12.0
4.
Granite
.172
4.
Meehanite 1(
0.9
Meehanite
12.0 to
12.4
5.
Meehanite
.119
5.
Steel 10
4.2
5-.
Magnesium
26.8
6.
Steel
.115
6.
Magnesium 10;
9.0
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