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National Advisory Committee for Aeronautics, Technical Notes - Bearing Strengths of Some Aluminum Alloy and Castings

Bearing tests were made of aluminum-alloy sand castings of l95-T1L
l95-T6, 220- -T1+, and 356-T6 to evaluate the bearing strength of these _ __ ”--
alloys and their relation to tensile properties. Comparisons between
tensile properties obtained from individually cast test bars and specimens
machined from the bearing—test slabs emphasize the fact that size and
form of casting my have a significant effect upon mechanical properties.
The bearing-strength characteristics of these aluminum castings with ,T
respect to edge distance and ratios of specimen width to pin diameter were
not significantly different from those which have been observed for the p _
common wrought-aluminum alloys. The ratios of bearing yield to tensile .__
yield strengths for the castings were about 20 percent higher than those _
for the wrought materials; the ratios of bearing ultimate to tensile -
ultimate strengths were about the same. Ratios of bearing to tensile _
strengths are proposed as a basis for the selection of allowable bearing
values for the design of aluminum—alloy sand. castings.

The bearing tests described in this report are the first to be
made in the Aluminum Research Laboratories on alminum-alloy sand
castings and constitute part of a general program of research covering
the determination of the mechanical properties of the light-weight
structural alloys of interest in aircraft design. Although bearing
strengths are probably not a very important factor in the design of
most aluminum-alloy sand castings, some data relating to this property
are needed.

Reference 1 lists three sand—cast aluminum alloys: 195, 220 ,
and 356. Values of ultimate bearing strength are given for the first
two, for an edge distance of twice the pin diameter, but no other
bearing data are given. These tests were undertaken to provide a more _ .
complete evaluation of the bearing—strength characteristics of these > __ ':
alloys The following tempers were investigated: 195-T4, l95-T6,
220- -Tl+, and. 356—T6.