straight bend with a short radius can be made by the
Guerin process, as shown in figure 2-27, or by press or
leaf brakes. The Guerin process is the most widely used
method for forming and shallow drawing, employing a
rubber pad as the female die, which bends the work to
the shape of the male die.
Magnesium alloys possess good casting
characteristics. Their properties compare favorably
with those of cast aluminum. In forging, hydraulic
presses are ordinarily used; although, under certain
conditions, forging can be accomplished in mechanical
presses or with drop hammers.
Magnesium embodies fire hazards of an
unpredictable nature. When in large sections, its high
thermal conductivity makes it difficult to ignite and
prevents its burning. It will not burn until the melting
point is reached, which is approximately 1,200F.
Figure 2-27.--Guerin process.
However, magnesium dust and fine chips are ignited
easily; precautions must be taken to avoid this if
possible. If they are ignited, you should extinguish
appreciate the importance of checking the specific
them immediately with an extinguishing powder such
technical publication. Structural repair of these
as powdered soapstone, clean, dry, unrusted cast iron
members, apparently similar in construction, will thus
chips, or graphite powder.
vary in their load-carrying design with different
aircraft.
CAUTION
Structural repair instructions, including tables of
interchangeability and substitution for ferrous and
Water or any standard liquid or foam
nonferrous metals and their specifications for all types
extinguisher causes magnesium to burn more rapidly
of aircraft used by the Navy, are normally prepared by
and may cause small explosions.
the contractor. Such instructions are usually contained
in the NA 02-XXX-3 manual covering structural repair
SUBSTITUTION AND
instructions for specific models of aircraft. Similar
INTERCHANGEABILITY OF AIRCRAFT
information is also contained in General Manual for
METALS
Structural Repair, NA 02-1A-1.
Aerospace Metals-General Data and Usage
In selecting interchangeable or substitute materials
Factors, NA 02-1A-9, provides precise data on specific
for the repair and maintenance of naval aircraft, it is
metals to assist in selection, usage, and processing for
important that you check the appropriate aeronautic
fabrication and repair. Always consult these
technical publications when specified materials are not
publications and the NA 02-XXX-3 aircraft manual for
in stock or not obtainable from another source. It is
the specific type of aircraft when confronted with a
impossible to determine if another material is as strong
problem concerning maintenance and repair involving
as the original by mere observation. There are four
substitution and interchangeability of aircraft structural
requirements that you must keep in mind in this
metals. Be sure you have the most recent issue of the
selection. The first and most important of these is
aeronautic technical publication.
maintaining the original strength of the structure. The
other three are maintaining contour or aerodynamic
Q2-28.
What metal property allows it to resist
smoothness, maintaining original weight, if possible, or
abrasion, penetration, cutting action, and
keeping added weight to a minimum, and maintaining
permanent distortion?
the original corrosive-resistant properties of the metal.
Q2-29.
What metal property enables a metal to return
Because different manufacturers design structural
to its original shape after an applied force has
members to meet various load requirements, you can
been removed?
2-33
