dynamic mechanical properties of metals madison minsk, ananya garg, rachel ngai, ian culhane, eric...
TRANSCRIPT
Dynamic Mechanical Properties of MetalsMADISON MINSK, ANANYA GARG, RACHEL NGAI, IAN CULHANE, ERIC SPEAR
Introduction•Internal Friction: the force that resists the motion of the elements in a solid while it undergoes deformation
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
Introduction•Torsion Pendulum: torsion wire is free to twist about its axis, causing the disk to rotate, associated with mechanical deformation
Setup
Experiment1. Twist wire to initiate torsional oscillation
2. Measure frequency of oscillation
3. Measure amount of damping of oscillation
Calculations
Internal Friction
1/20 [ln(T0/T20)]
T0
T20
Calculations Shear Modulus
f = frequency in Hzp = Period in secondsG = Shear ModulusI = Moment of Inertia
=L
=r
Crystal Structure
•Steel is Body Centered Cubic (BCC)
•Carbon atoms occupy interstitial sites
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
Comparison of Shear Modulus and Internal Friction in Five Metals
Frequency (hz)
Internal Friction(milliN) x10^-3
Shear Modulus(Mpa) x10^5
Steel .842 8.73 5.25
Copper .631 8.46 3.01
Bronze .603 2.98 2.79
Titanium .601 2.73 2.66
Aluminum .449 25.0 1.59
0.064”
30.0625”
Dimensions
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)
Special Thanks
•Roy Baggerly•David Starkebaum•Davis Tran•Boeing•Tuesday Kuykendall