Ken Youssefi SJSU, ME dept. 1

Material Selection

Function

Material Shape

Process

Material selection and process cannot be separated from the shape and the function of the product, two way interaction.

Function dictates the choice of material and shape.

Process interacts with shape.

Process is influenced by material

Shape restricts the choice of material and process.

Ken Youssefi SJSU, ME dept. 2

Engineering Materials

Materials

Metals Plastics

Steel

Stainless steel

Die & tool steel

Cast iron

Ferrous Non-ferrous

Aluminum

Copper

Zinc

Titanium

Tungsten

Thermoplastics

Acrylic

Nylon

ABS

Polyethylene

Polycarbonate

PVC

Thermosets

Phenolic

Polymide

Epoxies

Polyester

Elastomers

Rubber

Polyurethane

Silicone

Ken Youssefi SJSU, ME dept. 3

Engineering Materials

Materials

Metals PlasticsCeramicsGlass

Carbides

Nitrides

Graphite

Diamond

Glasses

Glass ceramics

Composites

Reinforced plastics

Metal-Matrix

Ceramic-Matrix

Laminates

Ken Youssefi SJSU, ME dept. 4

Most Commonly Used MaterialsThe following 25 materials are the most commonly used materials in the design of mechanical products; in themselves they represent the broad range of other materials.

Steel and Cast Iron 

1. 1020 (plain carbon steel, hot-rolled or cold-drawn)2. 1040 (plain carbon steel, hot-rolled or cold-drawn)3. 4140 (heat-treated alloy steel, chromium-molybdenum)4. 4340 (heat-treated alloy steel, nickel-chromium-molybdenum)5. S30400 (stainless steel)6. S316 (stainless steel)7. O1 (tool steel) 8. ASTM20-60 (gray cast iron)

Ken Youssefi SJSU, ME dept. 5

Most Commonly Used Materials

Aluminum and Copper Alloys

9. 2024 (aluminum, O, T3, T4 or T6)10. 3003 (aluminum, H12 or H16)11. 6061 (aluminum, T6)12. 7075 (aluminum, T6)13. C268 (copper)

Other metals

14. Titanium 6-415. AZ63A (magnesium)

Ken Youssefi SJSU, ME dept. 6

Most Commonly Used Materials

Plastics

16. ABS17. Polycarbonate18. Nylon 6/619. Polypropylene20. Polystyrene

Ceramics

21. Alumina22. Graphite

Composite materials

23. Douglas fir24. Fiberglass25. Graphite/epoxy

Ken Youssefi SJSU, ME dept. 7

Application of Most Commonly Used MaterialsComponent Material

Ken Youssefi SJSU, ME dept. 8

Application of Most Commonly Used MaterialsComponent Material

Ken Youssefi SJSU, ME dept. 9

Application of Most Commonly Used Materials

Component Material

Ken Youssefi SJSU, ME dept. 10

Properties of Most Commonly Used Materials

Ultimate Strength in tension

Ken Youssefi SJSU, ME dept. 11

Properties of Most Commonly used Materials

Yield strength

Ken Youssefi SJSU, ME dept. 12

Properties of Most Commonly used Materials

Fatigue endurance limit (strength under cyclic loading)

Ken Youssefi SJSU, ME dept. 13

Properties of Most Commonly used Materials

Density

Ken Youssefi SJSU, ME dept. 14

Cost of Most Commonly used Materials

Ken Youssefi SJSU, ME dept. 15

Example – Materials for table legs

Luigi Tavolino, furniture designer, conceives of a lightweight table of daring simplicity: a flat sheet of toughened glass supported on slender, unbraced, cylindrical legs. The legs must be solid and as light as possible (to make the table easier to move). They must support the table top and whatever is placed upon it without buckling. What materials

could one recommend.

Ken Youssefi SJSU, ME dept. 16

Example – Materials for table legsThe Model

The leg is a slender column of density ρ and modulus E. The load P and its length l are determined by design (fixed). The radius r of the leg is a variable. We wish to minimize the mass m of the leg.

Objective function

Ken Youssefi SJSU, ME dept. 17

Example – Materials for table legs

The constraint is that the legs must support a design load without buckling.Euler’s buckling equation

The weight is minimized by selecting the subset of materials with the greatest value of the material index.

where I = π r4/4

Solving for the free variable , r, and substituting it into the equation for m gives,

Material properties

=

Ken Youssefi SJSU, ME dept. 18

Example – Materials for table legs

Solving the Euler’s formula for r, gives an equation for the thinnest leg which will not buckle:

Material properties

The thinnest leg is that made of the material with the largest value of the material index.

Two material indices,

To minimize the weight, both have to be maximize.

Ken Youssefi SJSU, ME dept. 19

Procedure for deriving material indices

Ken Youssefi SJSU, ME dept. 20

Modulus of Elasticity (E) vs. Density (ρ) Charts

Constant guidelines

Ken Youssefi SJSU, ME dept. 21

Modulus of Elasticity (E) vs. Density (ρ) Charts

Ken Youssefi SJSU, ME dept. 22

Modulus of Elasticity (E) vs. Density (ρ) Charts

Ken Youssefi SJSU, ME dept. 23

Ken Youssefi SJSU, ME dept. 24

Summary of materials for table legs