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Primer on Materials and Design for Stiffness

Primer on Materials and Design for Stiffness. TEC 316 Dr. Lou Reifschneider Many figures taken from “ Designing with Plastics by TICONA”. The Ideal Material. Endless and ready supply Cheap to refine and produce Energy efficient Strong, stiff, & dimensionally stable at all temperatures

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Primer on Materials and Design for Stiffness

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  1. Primer onMaterials and Design for Stiffness TEC 316 Dr. Lou Reifschneider Many figures taken from “Designing with Plastics by TICONA”

  2. The Ideal Material • Endless and ready supply • Cheap to refine and produce • Energy efficient • Strong, stiff, & dimensionally stable at all temperatures • Lightweight • Corrosion resistant • No harmful effects on the environment or people • Biodegradable - when appropriate • Numerous secondary uses

  3. Important Material Properties • Strength (tensile, compressive, flexural, shear, and torsional). • Resist deformation at elevated temperatures. • Fatigue resistance (repeated loading and unloading). • Toughness (resistance to impact). • Wear resistance (hardness). • Corrosion resistance (acids, oil, water, ..). • Electrical arc resistance (wiring). • Thermal insulation (where appropriate)

  4. Classification of Engineering Materials from Design for Manufacturability Handbook, 2nd Ed. by James G. Bralla

  5. Classification of Engineering Materials from Design for Manufacturability Handbook, 2nd Ed. by James G. Bralla

  6. Stress/Strain Behavior of Metals and Plastics Material Stiffness called Young’s Modulus, E Initial slope of Stress/Strain curve is E from Plastics for Engineers by Domininghaus, H.

  7. Beam Bending

  8. Beam during bending

  9. Common Constraints

  10. Important Beam Geometry: Moment of Inertia, written as I A beam 10” long, 1” wide and 1” tall has an I of “na” in above denotes the neutral axis.

  11. Moment of Inertia of 2 x 4 board 2 x 4 standing on 2” side has I Vertical 2x4 is 4 times stiffer than horizontal 2x4 2 x 4 standing on 4” side has I

  12. The stiffer something is, the less it deflects under a given load. • Material Stiffness ~ E • Geometric Stiffness ~ I • Flexural Rigidity ~ E x I

  13. Design made stiffer by • Increasing Modulus (E) by changing material. OR • Increasing I by making part thicker, wider, or moving material away from the bending axis.

  14. Want to stiffen this design. Stiffer, keeping original thickness of product. As stiff, BUT THICKER (much more material)

  15. Other ways to stiffen while keeping original thickness

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