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The size, weight, surface area, and otherproperties available from a solid modelare most often part of the design

.The following are mass property calculations available in

Volume Density MassSurface area Centroid Moment of Inertia

Principal Moments

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Volume is the amount of three-dimensionalspace t at an o ject ta es up.

Design engineers use this value to

determine the amount of material needed toproduce a part.

V = H x W x L

84

4V = 4 x 4 x 8

V = 128 in3

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Density is defined as mass per unit volume.

Densit is different for ever material and can

be found in a machinist handbook.

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Mass is the amount ofmatter in an ob ect or thequantity of the inertia ofthe object.

purchased by weight; tofind weight, we need the

.

Polypropylene has a =density of .035 lbs/in3

Using the volume from theMass = 128 in3 x .035 lbs/in3

previous example. (128 in3

) Mass = 4.48 lbs.

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Surface area is the squared

dimensions of the exteriorsurface.

Surface area is important when

determining coatings and heattransfer of a part.

B

B= 4in x 8in = 32 in2

C= 4in x 8in = 32 in2

C

D FA

D= 4in x 8in = 32 in2

E= 4in x 8in = 32 in2

E

B= 4in x 4in = 16 in2

A + B+ C + D+ E + F = 160 in2

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geometric center of a solid.

with the center of gravity.

The two onl exist at the

same 3D point when thepart has uniform geometryan ens y.

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An objects opposition toan axis.

This property is most often

use w en ca cu ating t edeflection of beams.

= 2

= Integral (Calculus)

I = Moments of Inertia

r = s ance o a po n s n anelement from the axis

= Densit of the material

dV= Division of the entire bodyinto small volume units.

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Is similar to moments of inertia only thatpro uc s o ner a are re a ve o wo axesinstead of one.

, ,symbol when defining products of inertia.

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9

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A dimension from the axis where all mass isconcentrate , an wi pro uce t e samemoment of inertia.

xkx=

M = Mass

I = Moments of inertia

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The lines of intersection created

perpendicular planes, with thethree lanes oint of intersection

at the centroid of the part.

The X, Y, and Z axes showthe principal axes of theellipsoid.

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Principal moments are themomen s o ner a re a e othe principal axes of the

.

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