1. Dynamic Mechanical Properties of Metals MADISON MINSK, ANANYA GARG, RACHEL NGAI, IAN CULHANE, ERIC SPEAR

2. Introduction Internal Friction: the force that resists the motion of the elements in a solid while it undergoes deformation

3. Introduction Shear Modulus: the ratio of shear stress to the shear strain; describes the material's response to shear stress  Higher shear modulus results in less deformation from force

4. Introduction Torsion Pendulum: torsion wire is free to twist about its axis, causing the disk to rotate, associated with mechanical deformation

6. Setup

7. Experiment 1.Twist wire to initiate torsional oscillation 2.Measure frequency of oscillation 3.Measure amount of damping of oscillation

8. Calculations Internal Friction 1/20 [ln(T 0 /T 20 )] T0T0 T 20

9. Calculations Shear Modulus f = frequency in Hz p = Period in seconds G = Shear Modulus I = Moment of Inertia =L =r

10. Crystal Structure Steel is Body Centered Cubic (BCC) Carbon atoms occupy interstitial sites

11. Dynamic Mechanical Analysis (DMA) Oscillating stress is applied, strain is measured Frequency of oscillation or temp is altered Output: Frequency (hz) vs Probe position (mm) graph

12. Comparison of Shear Modulus and Internal Friction in Five Metals Frequency (hz) Internal Friction (milliN) x10^-3 Shear Modulus (Mpa) x10^5 Steel.8428.735.25 Copper.6318.463.01 Bronze.6032.982.79 Titanium.6012.732.66 Aluminum.44925.01.59 0.064” 30.0625” Dimensions

14. Conclusion/Application The shear modulus- important when materials will be subjected to shear stress The internal friction- important in applications like airplane engines (subjected to vibrations)

15. Special Thanks Roy Baggerly David Starkebaum Davis Tran Boeing Tuesday Kuykendall