Stress relaxation function of bone and bone collagen

Area of Science:

• Biomaterials Science
• Materials Science
• Biophysics

Background:

• Bone and bone collagen exhibit complex viscoelastic behaviors crucial for understanding their mechanical properties.
• Previous studies have explored bone's mechanical response, but detailed characterization of relaxation mechanisms remains an active area of research.

Purpose of the Study:

• To investigate the relaxation behavior of Young's and shear moduli in bovine bone and bone collagen.
• To model and identify the underlying stress relaxation mechanisms in bone tissue.

Main Methods:

• Experimental determination of relaxation moduli for bovine bone and bone collagen.
• Application of a combined exponential decay and Kohlrausch-Williams-Watts (KWW) function to model the observed relaxation processes.
• Analysis of structural properties to support the proposed relaxation model.

Main Results:

• Two distinct relaxation stages (Process I and Process II) were identified in bovine bone and bone collagen.
• Process II followed a simple exponential decay, while Process I was accurately described by the Kohlrausch-Williams-Watts (KWW) function.
• A combined model, M(r)(t) = A1exp[-(t/tau 1)B]+A2exp[-(t/tau 2)], successfully represented the overall relaxation modulus.

Conclusions:

• The stress relaxation in bone is primarily governed by the viscoelastic properties of the collagen fiber matrix.
• The KWW function's applicability suggests a disordered glassy structure within the collagen fiber, consistent with structural findings.
• This study provides a quantitative model for understanding bone's viscoelastic relaxation mechanisms.