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Magnetostrictive Composite Sensors for Stress Sensing Applications
Edward Lynch
Ashraf Al-Hajjeh
Department of Electrical Engineering
University of Wisconsin -Milwaukee
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Background
• Sensors were molded onto aluminum substrates in the form as rectangular prisms at angles of 0°, 30°, 45°, 60°, and 90°.
• The magnetostrictive composite stress sensors work on the principle of the Villari effect, also know as inverse magnetostriction.
• Inverse magnetostriction is a change in magnetic susceptibility when a mechanical stress is applied to a material.
forceforce
x
y
• A magnetic circuit consisting of a toroidal sensing coil with an air gap core and sensor was formed.
• Inductance measurements were taken at the terminals of the coil.
• These measurements were then used to determine the relative change in susceptibility.
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• Relative change in magnetic susceptibility was determined from inductance measurements using the following relationship:
Change in Magnetic Susceptibility
• Where L is the inductance for a given stress. L0 is the inductance for zero stress, and La is the inductance of the coil measured in air.
• This was determined through magnetic circuit analysis.
A fit function was developed based on the experimental results:
where χ is susceptibility at a given stress, χ0 is
the susceptibility at zero stress, C1 and C2 are fit parameters, σ is stress in the aluminum, and ϕσ is the sensor rotation angle.
aLL
LL
0
0
0
21 cos0
CC
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Results
Percent change in magnetic susceptibility as a function of stress in the aluminum substrate.
-80 -40 0 40 80
-10
0
10
[MPa]
m
[%
]
45
90
60
30
0
-80 -40 0 40 80
-10
0
10
[MPa]
m
[%
]
90
60
45
30
0
Fit function plots for each angle of sensor rotation.
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Acknowledgements
Faculty AdvisorsChiu Tai Law, PhDRani El-Hajjar, PhD
Financial SupportResearch Growth Initiative (RGI)
Thank You!