A version of the support platform in Figure 2.25 is required for aerospace use,
ID: 2248269 • Letter: A
Question
A version of the support platform in Figure 2.25 is required for aerospace use, for which its electrical conductivity should be as high as possible combined with minimum weight. Assume that all the section thicknesses should have the same value, h, so that the part volume can be expressed approximately in the form
V C0h, where C0 is a constant. Using electrical resistivity, ( cm), and density, (g/cm3), determine the derived parameter which represents electrical current ow/weight. Use this parameter to compare different possible materials. Refer to materials handbooks for resistivity and density data, or use web material data- bases such as www.matweb.com. Since alloying elements can have a signi cant effect on electrical resistivity, compare only pure metals in this exercise as a start- ing point for the investigation of candidate alloys.
(Hint: Assume an applied voltage, v, and conductive paths up through the legs of width, w, and length, L are xed by the design. Also assume that the leg thickness h changes with the change of material to obtain the required level of conductivity. Write an expression for current ow, I, in terms of these parameters and the variable thickness, h. Use this with an approximate expression of part weight to obtain the required result.)
FIGURE 2.25 Electrical instrument support platform.Explanation / Answer
The pure metals are
metals resistivity
Aluminum 2.82×108
Copper 1.68×108
Chromium 12.5×108
Nickel 6.99×108
Niobium/Columbium 15.2×108
Iron 9.71×108
Magnesium 4.39×108
The geometrical classification of a part is concerned with the following characteristics:
The overall size
The basic shape
The accuracy and surface finish
The cross-section
Functionals features-projections, features
The given platform should be light weight and electrical conductivity is high.