dynamic mechanical properties of metals madison minsk, ananya garg, rachel ngai, ian culhane, eric...
TRANSCRIPT
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Dynamic Mechanical Properties of MetalsMADISON MINSK, ANANYA GARG, RACHEL NGAI, IAN CULHANE, ERIC SPEAR
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Introduction•Internal Friction: the force that resists the motion of the elements in a solid while it undergoes deformation
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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
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Introduction•Torsion Pendulum: torsion wire is free to twist about its axis, causing the disk to rotate, associated with mechanical deformation
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Setup
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Experiment1. Twist wire to initiate torsional oscillation
2. Measure frequency of oscillation
3. Measure amount of damping of oscillation
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Calculations
Internal Friction
1/20 [ln(T0/T20)]
T0
T20
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Calculations Shear Modulus
f = frequency in Hzp = Period in secondsG = Shear ModulusI = Moment of Inertia
=L
=r
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Crystal Structure
•Steel is Body Centered Cubic (BCC)
•Carbon atoms occupy interstitial sites
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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
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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
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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)
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Special Thanks
•Roy Baggerly•David Starkebaum•Davis Tran•Boeing•Tuesday Kuykendall