APPENDIX A

MATERIAL PROPERTIES FOR DESIGN

To estimate the masses of components for alternate configurations, nominal design values for a variety of physical properties must be assumed for the materials involved. Only a few "standard" metal alloys are shown in Table 4-4, chosen to give good weldability, corrosion resistance, and forming properties. A more careful specification of specific alloy percentages for structural components in a final design is expected to reduce the actual structural mass somewhat from that derived from this conservative approach. For particular applications where, for example, cyclic stress reversal may induce fatigue, high temperatures cause creep, or low temperatures cause brittleness, special materials must be used.

TABLE 4-4 (gif format)

Table 4-4.- MATERIAL PROPERTIES OF SOME METAL ALLOYS

	Tensil strength								Conductivity
Metal types	Ultimate MPa	Yield MPa	Working MPa	Brinell hardness number	Density G, 10^3 kg/m^3	Modulus E, MPa	Poisson ratio	Coefficient of expansion 10^-6 X C^-1 (degrees)	Electric 10^-6 X ohm-m^-1	Thermal W/m degrees C
Aluminum (150 Degrees C) i) Pure (99.5 percent)	83	41	28	30	2.70	70,000	1/3	24	36	230
ii) Heat treated alloy: Al 12 Si 0.5 Mg	303	248	165	95	2.65	76,000	1/3	19	21	157
iii) Cold form wire or plate	455	352	234	140	2.65	76,000	1/3	20	31	163
Titanium i)Heat treated alloy: Ti 5 Al 2.5 Sn	620	517	345	105	4.54	110,000	1/3	10	-	22
Cold formed wire or plate	1030	931	620	110	4.54	110,000	1/3	9	-	23
i) Magnesium Heat treated castings: Mg 8.5 Al	138	83	55	48	1.8	43,000	0.35	27	7	93
ii)Thin plate or wire Mg 3 Al 0.5 Mn 0.1 Zn	207	152	110	52	1.8	43,000	.35	25	8	81
Steel i) Wrought iron	352	207	138	70	7.8	207,000	.3	12	9	93
ii) Rolled - heat treated	538	352	234	120	7.8	200,000	.3	12	8	81
iii) Cold drawn	1380	1240	830	200	7.8	200,000	.3	12	8	81

A safety factor of 1.5 is applied to the yield stress to give safe working values. This corresponds to the standard for large civil engineering structures combining dead- and live-load factors. In all large structures the material is proof-tested before use, so that, in reality, the end result of processing and fabrication is not a dubious variable but can be a controlled parameter. At least one good machine for static and dynamic testing of the strength of materials must be included in the laboratory equipment brought from Earth to the colony site.

The strength properties of ceramic-type materials and "soil" if (table 4-5) are low, and experimental results from any pilot study for processing lunar ores should help define them more precisely. While it should also be possible to grow long glass fibers having great structural strength, such materials are not assumed for construction of the first colony.

TABLE 4-5 (gif format)

TABLE 4-5.- MATERIAL PROPERTIES OF SOME CERAMICS AND SOILS

	Flexural working stress MPa
	Untempered	Tempered	Brinell hardness number	Density G, 10^3 kg/m^3	Poisson ratio,	Coefficient of expansion 10^-6 C^-1degrees	Thermal conductivity, W/m C (degrees)
Ceramics i) Silica glass	3.4	6.9	400	2.2	0.18	80	15
ii)Window sheet	8.3	16.5	500	2.45	.23	850	.9
Rock i)Fused	3.4		200	2.8	.15	-	-
ii)Soil (dry)	-		-	1.4	.1	-	-
iii)Soil (60 percent moisture)	-		-	1.68	.5	-	-

a Compressive strength is about 10 times greater.

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