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Theoretical analysis of the experimental artifact in trabecular bone compressive modulus
T M Keaveny1, R E Borchers, L J Gibson
1Department of Orthopaedic Surgery Charles A. Dana Research Institute, Beth Israel Hospital, Boston, MA 02215.
Journal of Biomechanics
|April 1, 1993
Summary
Experimental compression tests on trabecular bone can lead to significant errors in modulus measurements. Eliminating friction improves accuracy but still underestimates Young
Area of Science:
- Biomechanics
- Materials Science
Background:
- Conventional compression testing of trabecular bone relies on platen displacement to determine strain.
- This method is susceptible to experimental artifacts, particularly from friction and specimen damage.
Purpose of the Study:
- To theoretically analyze and quantify experimental artifacts in trabecular bone compression testing.
- To derive equations describing damage and friction artifacts and estimate their impact on modulus measurements.
Main Methods:
- Theoretical analysis using derived equations for damage and friction artifacts.
- Determination of unknown constants via linear finite element analyses and in vitro compression tests.
- Estimation of artifacts across various specimen geometries and sizes using finite element analysis.
Main Results:
- Without friction, Young's modulus can be underestimated by at least 45% due to machining damage.
- Platen's modulus can deviate significantly (30-175%) from Young's modulus depending on geometry and Poisson's ratio.
- Increasing specimen size has minimal effect on reducing artifacts.
Conclusions:
- The precision of conventional compression tests is poor due to potential friction and unknown Poisson's ratio.
- Eliminating friction is crucial for accuracy but leads to underestimation of Young's modulus.
- Both modulus and potentially strength measurements are affected by these experimental artifacts.