Driver Insert David Birsen Brooke Gladstone Huan Kiat Koh

Background Hardwoods used until 1990’s; Ti alloys popular in modern drivers Range from alpha (~90% Ti) to beta (~75% Ti) alloys USGA regulations as a result of new materials – Set maximum COR of in 1998 – Measure ball velocity and pre-impact club head velocity using Characteristic Time Test

Objective Minimize the mass by minimizing depth – Equation: Rationale: – Lighter clubs can be swung faster so ball travels farther – Minimizes cost – Maximizes COR

Constraints Oval cross-section Length of 90mm and height of 55mm COR ≤ 0.83 Cost ≤ $5.00 per part Recyclable Yield stress >> Stress at Impact High Young’s Modulus Processability: needs to be made in bulk

Material Indices Equation for Coefficient of Restitution (Johnson) 1 st Constraint: 2 nd Constraint:

CES Plot: Level 2

Material Options: Level 2 Options include: – Boron Carbide – Nickel – Nickel-based superalloys – Nickel-chromium alloys – Tin – Titanium alloys

Material Selection: Level 2 Material properties for shortlisted materials were tabulated and compared. The material with the best combination, Titanium Alloys, was chosen.

CES Plot: Level 3 Highlighted materials have a cost close to $50/kg (0.1 kg and $5 at most per part) and are recyclable

Material Options: Level 3 Titanium alloys that meet the restrictions on price and recyclability: – Titanium, alpha alloy, Ti-5Al-2.5Sn-0.5Fe, annealed – Titanium, alpha alloy, Ti-8Al-1Mo-1V, duplex annealed – Titanium, alpha alloy, Ti-8Al-1Mo-1V, single annealed – Titanium, alpha alloy, Ti-8Al-1Mo-1V, solution treated & stabilized – Titanium, alpha-beta alloy, Ti-6Al-2Sn-2Zr-2Mo, annealed – Titanium, alpha-beta alloy, Ti-6Al-2Sn-2Zr-2Mo, solution treated & aged – Titanium, alpha-beta alloy, Ti-6Al-2Sn-2Zr-2Mo, triplex aged – Titanium, alpha-beta alloy, Ti-6Al-4V, aged – Titanium, alpha-beta alloy, Ti-6Al-4V, solution treated & aged – Titanium, beta alloy, Ti-5Al-2Sn-4Mo-2Zn-4Cr (Ti-17) – Titanium, commercial purity, Grade 2

Differences between Ti Alloys

Final Material Selection Titanium, beta alloy Ti-5Al-2Sn-4Mo-2Zn-4Cr (Ti-17) – Only beta alloy available with the set constraints Depth: mm Mass: 28.1 g

Processing Method

Final Recommendation Ti-17 Beta Alloy Processed by sheet forming – Good tolerance Stamped from one large sheet Polished Natural protective layer so no special finishing

References Ashby, Michael F. Materials Selection in Mechanical Design. 4th ed. Oxford: Butterworth-Heinemann, Print. Elerf, Glenn. Force of a Golf Club on a Golf Ball. The Physics Factbook Web. April GOLF CHANNEL Newsroom. USGA, R&A Rule on 'Spring-Like' Effect. The Golf Channel. August 6, Web. March 12, 2012 Johnson, K. L. Contact Mechanics, Chapter 11. Cambridge [Cambridgeshire]: Cambridge University Press, Print. (Page 363, 364) Tirosh, O. "Mechanics - Golf Swing." Golf Swing Analysis. Web. February Titanium and It’s Alloys as Used in Golf Club Heads. In Golf, Inc. Web. April 2, Titanium and Titanium Alloys. Everything Material, ASM International Web. April Titanium Alloys – Characteristics of Alpha, Alpha Beta and Beta Titanium Alloys. A to Z of Materials Web. April What is C.O.R.? What is CT? Wish on Golf. Web. March 12, 2012.