Magnetostrictive Composite Sensors for Stress Sensing Applications

Edward Lynch

Ashraf Al-Hajjeh

Department of Electrical Engineering

University of Wisconsin -Milwaukee

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.

• 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

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.

Acknowledgements

Faculty AdvisorsChiu Tai Law, PhDRani El-Hajjar, PhD

Financial SupportResearch Growth Initiative (RGI)

Thank You!