Volume effects on yield strength of equine cortical bone.

This study investigates the volume effect on the yield strength of equine bone materials. Particular focus was on assessing whether smaller volumes possess greater yield strength than larger volumes, and whether specimen volume accounts for significant differences in yield strength.

Introduction

• The research commenced with a focus on the volume effects, a key determinant of structural failure. This property ensures that the failure features of a material greatly depend on the volume of the specimen.
• Various elements like the load on structure due to “critical” flaws, the number and location of such flaws, and effect of the stress field within the tensioned volume contribute to the failure properties of the structure.
• Large volumes of materials are likely to contain more flaws than smaller volumes, making large volumes more susceptible to failure when subjected to similar stress conditions.
• The study hypothesized that this volume effect, previously observed in brittle ceramic and composite structures, would similarly impact the mechanical properties of bone.

Hypotheses of Study

• Two primary hypotheses were proposed. Firstly, the researchers predicted that smaller volumes of cortical bone would display higher yield strengths than larger volumes. Secondly, they supposed that the specimen volume is responsible for a comparable degree of variation in yield strength as the microstructural features.

Research Methodology

• Rectangular specimens (n=24) from the diaphyseal part of an equine third metacarpal, with nominal cross-sections of 3 x 4 mm and gage lengths of 10.5, 21, or 42 mm, were tested under tension to study the volume effect on their yield strength.
• The volume effect was demonstrated by the notable comparison of the smallest volume group’s yield strength to that of the largest volume group.

Results and Conclusions

• Results confirmed an affirmative correlation between the logarithm of yield strength and cumulative failure probability, suggesting that the yield strength data adheres to the two-parameter Weibull distribution.
• The researchers found a negative correlation between log yield strength and log volume, supporting their initial hypothesis—smaller volumes of cortical bone have a higher yield strength compared to larger volumes subjected to similar stress conditions.