Damage rate is a predictor of fatigue life and creep strain rate in tensile fatigue of human cortical bone samples.
We present results on the growth of damage in 29 fatigue tests of human femoral cortical bone from four individuals, aged 53-79. In these tests we examine the interdependency of stress, cycles to failure, rate of creep strain, and rate of modulus loss. The behavior of creep rates has been reported recently for the same donors as an effect of stress and cycles. In the present paper we first examine how the evolution of damage (drop in modulus per cycle) is associated with the stress level or the "normalized stress" level (stress divided by specimen modulus), and results show the rate of modulus loss fits better as a function of normalized stress. However, we find here that even better correlations can be established between either the cycles to failure or creep rates versus rates of damage than any of these three measures versus normalized stress. The data indicate that damage rates can be excellent predictors of fatigue life and creep strain rates in tensile fatigue of human cortical bone for use in practical problems and computer simulations.
Cotton
John R
JR
Department of Engineering Science and Mechanics, Virginia Tech-Wake Forest School of Biomedical Engineering and Science, Virginia Tech, Mail code 0219, Blacksburg, VA 24061, USA. jcotton@vt.edu
Winwood
Keith
K
Zioupos
Peter
P
Taylor
Mark
M
D000368:Aged; D000375:Aging; D002102:Cadaver; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004548:Elasticity; D005260:Female; D005264:Femoral Fractures / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D015775:Fractures, Stress / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010812:Physical Stimulation / Q000009:adverse effects*; D011379:Prognosis; D013314:Stress, Mechanical; D013718:Tensile Strength; D014783:Viscosity