Physical Property Analysis

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design

Physical Properties

A physical property is a property that can be observed or measured without changing the identity of the matter.

Examples of Physical Properties:

Volume Density Color

Surface Area Centroid Moment of Inertia

Mass Odor Temperature

Weight Viscosity Electric Charge

Boiling Point Melting PointAttraction to magnets

Physical Property Analysis

The size, volume, surface area, and other properties associated with a solid model are often part of the design constraints or solution criteria.The following are physical properties presented in typical solid modeling programs:

Volume Density Mass

Surface Area Center of Gravity Moment of Inertia

Product of Inertia Radii of Gyration Principal Axes

Principal Moments Length

Physical Properties

• We have already investigated density, volume, and mass/ weight

• Another important physical property is Surface Area

Surface Area• Surface area is the area of the

exterior surface of an object.• Surface area is important when

determining coatings and heat transfer of a part.

B

C

D

E

FA

Area A = 3 in. x 4 in. = 12 in.2

Area B = 4 in. x 8 in. = 32 in.2

Area C = 3 in. x 8 in. = 24 in.2

Area D = 4 in. x 8 in. = 32 in.2

Area E = 3 in. x 8 in. = 24 in.2

Area F = 3 in. x 4 in. = 12 in.2

Surface Area = 136 in.2

Surface Area• Another way to represent the

formula for surface area of a rectangular prism is given on the formula sheet

Surface Area

Surface Area = 2 [(8 in.)(4 in.) + (8 in.)(3 in.) + (4 in.)(3 in.)]

= 136 in.2

Formula Sheet

Additional Physical Properties

Center of Gravity

• A 3D point where the total weight of the body may be considered to be concentrated.

• The average location of an object.• If an object rotates when thrown it rotates

about its center of gravity.• An object can be balance on a sharp point

placed directly beneath its center of gravity

Centroid

• A 3D point defining the geometric center of a solid.

• Do not confuse centroid with the center of gravity.– The two only exist at the same 3D point when

the part has uniform geometry and density.

Principal Axes

• The lines of intersection created from three mutually perpendicular planes, with the three planes’ point of intersection at the centroid of the part.

The X, Y, and Z axes show the principal axes of the ellipsoid.

Physical Properties and 3D Solid Modeling

Physical Properties and 3D Solid Modeling

• 3D solid modeling software can display physical properties of modeled objects.

• In Browser right click on part name

• Choose iProperties

Physical Properties• 3D solid modeling software can display

physical properties of modeled objects

• In Browser right click on part name

• Choose iProperties• Choose Physical tab• Choose appropriate

material• Depress Update button• Physical properties are

displayed

Brodinski, K. G. (1989). Engineering materials properties and selection. Prentice Hall, Inc.: Englewood Cliffs, NJ.

Budinski, K. G. (1992). Engineering materials (4th Ed.). Prentice Hall, Inc.: Englewood Cliffs, NJ.

Gere, J. M., & Timoshenko, S. P. (1997). Mechanics of materials. PWS Publishing Company: Boston.

Lockhart, S. D., & Johnson, C. M. (1999). Engineering design communication: Conveying design through graphics (Preliminary Ed.). Addison Wesley Longman, Inc.: Reading, MA.

Madsen, D. A., Shumaker, T. M., Turpin, J. L., & Stark, C. (1994). Engineering design and drawing (2nd Ed.). Delmar Publishers Inc.: Albany.

Sources