The micropolar behaviour of cortical bone: size and surface effects in 3 point bending

Jamie Campbell Frame, Marcus Wheel, Philip Riches

Research output: Contribution to conferencePoster

Abstract

The heterogeneous microstructure of cortical bone may be important in the determination of stress concentrations and shielding in the vicinity of orthopaedic implants. We hypothesise that micropolar elasticity can parameterise the microstructure of cortical bone to better predict local stresses. Threepoint bending tests on bovine mid-diaphyseal bone demonstrated a size effect in which sample stiffness decreased as size reduced. However, computational predictions indicate that the size effect depends entirely on the surface condition: smooth surfaces result in increased stiffness as size decreases, whilst surfaces corrugated by the microstructure demonstrated an identically strong, yet opposite, effect. We have thus established the connection between anti-micropolar behaviour and surface heterogeneity, of significant relevance to all heterogeneous solids. For bone in particular, we have shown that the micropolar characteristic length is consistent with the Haversian canal diameter. Haversian canals are therefore of fundamental importance in understanding local stress and strain fields in cortical bone.

Conference

ConferenceXXIV Congress of the International Society of Biomechanics
CountryBrazil
CityNatal
Period4/08/139/08/13

Fingerprint

Bone
Canals
Microstructure
Stiffness
Orthopedics
Bending tests
Shielding
Stress concentration
Elasticity

Keywords

  • micropolar behaviour
  • cortical bone
  • size and surface effects
  • 3 point bending

Cite this

Frame, J. C., Wheel, M., & Riches, P. (2013). The micropolar behaviour of cortical bone: size and surface effects in 3 point bending. Poster session presented at XXIV Congress of the International Society of Biomechanics, Natal, Brazil.
Frame, Jamie Campbell ; Wheel, Marcus ; Riches, Philip. / The micropolar behaviour of cortical bone : size and surface effects in 3 point bending. Poster session presented at XXIV Congress of the International Society of Biomechanics, Natal, Brazil.
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Frame, JC, Wheel, M & Riches, P 2013, 'The micropolar behaviour of cortical bone: size and surface effects in 3 point bending' XXIV Congress of the International Society of Biomechanics, Natal, Brazil, 4/08/13 - 9/08/13, .

The micropolar behaviour of cortical bone : size and surface effects in 3 point bending. / Frame, Jamie Campbell; Wheel, Marcus; Riches, Philip.

2013. Poster session presented at XXIV Congress of the International Society of Biomechanics, Natal, Brazil.

Research output: Contribution to conferencePoster

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T1 - The micropolar behaviour of cortical bone

T2 - size and surface effects in 3 point bending

AU - Frame, Jamie Campbell

AU - Wheel, Marcus

AU - Riches, Philip

PY - 2013

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N2 - The heterogeneous microstructure of cortical bone may be important in the determination of stress concentrations and shielding in the vicinity of orthopaedic implants. We hypothesise that micropolar elasticity can parameterise the microstructure of cortical bone to better predict local stresses. Threepoint bending tests on bovine mid-diaphyseal bone demonstrated a size effect in which sample stiffness decreased as size reduced. However, computational predictions indicate that the size effect depends entirely on the surface condition: smooth surfaces result in increased stiffness as size decreases, whilst surfaces corrugated by the microstructure demonstrated an identically strong, yet opposite, effect. We have thus established the connection between anti-micropolar behaviour and surface heterogeneity, of significant relevance to all heterogeneous solids. For bone in particular, we have shown that the micropolar characteristic length is consistent with the Haversian canal diameter. Haversian canals are therefore of fundamental importance in understanding local stress and strain fields in cortical bone.

AB - The heterogeneous microstructure of cortical bone may be important in the determination of stress concentrations and shielding in the vicinity of orthopaedic implants. We hypothesise that micropolar elasticity can parameterise the microstructure of cortical bone to better predict local stresses. Threepoint bending tests on bovine mid-diaphyseal bone demonstrated a size effect in which sample stiffness decreased as size reduced. However, computational predictions indicate that the size effect depends entirely on the surface condition: smooth surfaces result in increased stiffness as size decreases, whilst surfaces corrugated by the microstructure demonstrated an identically strong, yet opposite, effect. We have thus established the connection between anti-micropolar behaviour and surface heterogeneity, of significant relevance to all heterogeneous solids. For bone in particular, we have shown that the micropolar characteristic length is consistent with the Haversian canal diameter. Haversian canals are therefore of fundamental importance in understanding local stress and strain fields in cortical bone.

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Frame JC, Wheel M, Riches P. The micropolar behaviour of cortical bone: size and surface effects in 3 point bending. 2013. Poster session presented at XXIV Congress of the International Society of Biomechanics, Natal, Brazil.