University of Southern CaliforniaSonny Astani Department Of Civil and Environmental Engineering

CE 334L Mechanical Behavior of MaterialsGroup 13/14

Margaret GwynneJeremy Molayem

Wonbae Yoon

STUDIES INTO DAMAGE DETECTION IN STEEL BARS

USING STRAIN GAUGES

Background

• Instrumentation

• Structural Health Monitoring

Experimental Model

1 ¾” x ½” x 30” Steel Bar

• Healthy/ Undamaged

• ½” Diameter Hole At Center

• ¾” Diameter Hole At Center

Experiments

Static

Dynamic

SATEC Bending

Abaqus Model

Strain at Center

Strain at Left Support

Small Hole -1.31*10^-6 9.02*10^-7

Big Hole -1.45*10^-6 8.39*10^-7

½” Diameter Holed Bar Model

Strain at Center

Strain at Left Support

Small Hole -1.31*10^-6 9.02*10^-7

Big Hole -1.45*10^-6 8.39*10^-7

¾” Diameter Holed Bar Model

Results + Discussion: Static Test

Results + Discussion: Static TestHookes Law: Stress = Young’s Modulus [E] * Strain

S=Mc/I – Stress & Moment greatest at fixed end

Results + Discussion: Dynamic Test

Damping Ratio Increase in damage, increase in damping ratio

Results + Discussion: SATEC Bending

¼” deflection 79 lbf vs. 72 lbf 8.8% Change in LoadRMS Equation: (√Σ(yo-y)2 /(Σyo)2)*100= % Change Strain

Results + Discussion: SATEC Bending

Theoretical v. Experimental

Equal frequency

Strain concentration at hole

Conclusion

Two Major Factors in Determining Damage

• Location from damage

• Type and amount of force applied

Static v. Dynamic v. SATEC Bending

Ideal Conditions needed

We would like to extend our sincerest thanks to our

teaching assistant Armen Derkevorkian, Lab Director

Lance Hill and Professor Masri for their time, guidance and encouragement throughout the duration of this project.

Acknowledgements

Thank You!