1. Materials selection - properties

2. Materials selection - properties

3. Materials selection - properties

4. Materials selection - environment

5. Bicycle frames

6. Bicycle frames

7. Bicycle frames – hot piercing for seamless tubing

8. Bicycle frames – cold drawing of seamless tubing
Cold drawing – need high formability
––> extensive work-hardening

9. Bicycle frames

10. Bicycle frames

11. Bicycle frames – common materials used
density modulus
Plain carbon steel 7.8 gm/cc 200GPa
Cr-Mo steel
6061–T
Ti-3Al-2.5V
Polymer composite
yield yield/density
Plain carbon steel 240 MPa 30
Cr-Mo steel
6061–T
Ti-3Al-2.5V

12. A little bit more on Ti and its alloys
Ti is polymorphic: -Ti (hcp) ––> -Ti(A2) at 882°C
Ti mostly alloyed with Al, V
Remember - & -Fe w/ chromium, & nickel
Various elements have different solubilities in - & -Ti

13. A little bit more on Ti and its alloys
Ti-3Al-2.5V is an "- alloy"
Enuf -stabilizer (V) added so that a little  phase can exist at room temp
&  phase solution strengthened by Al & V
 alloys are stronger than those containing only  or  phase

14. Joining techniques
Conventional arc welding
Tungsten inert gas (TIG) welding
Brazing
Adhesive bonding

15. Joining techniques
Plain carbon steel frame – TIG welded
Tubing is strengthened by drawing operation –
but softened near weld
Use butted tubing for strengthening HAZ region

16. Cr-Mo steel frame – TIG welded
Joining techniques
Cr-Mo steel frame – TIG welded
But weld and HAZ harder than tubing – more rapid
cooling than that experienced by tubing – get Bainite
original tube