Bending Stresses in Bones At a given location, stress depends on 1. Properties of cross-section 2. Bending moments(moment arm lengths and force magnitudes
Bending Stresses in Bones Bending Stresses in Bones At a given location, stress depends on: At a given location, stress depends on: 1. Properties of cross Properties of cross -section section 2. Bending Moments (moment arm Bending Moments (moment arm lengths and force magnitudes) lengths and force magnitudes)
Bending stresses in cantilever beam ensue 4—d stress M I= Cross-sectional Moment of inertia Compressive M=Fxd stress
Bending stresses in cantilever beam Bending stresses in cantilever beam σ = My I F y d I = Cross-sectional Moment of Inertia Compressive stress Tensile stress M = F x d
Maximum Bending Stress M= bending moment I cross-sectional moment of inertia y= distance from centroid to surface y Z= Section modulus M M Section Modulus predicts maximum stress(o)on subperiosteal (outer) surface
Maximum Bending Stress Maximum Bending Stress σmax = y My I = M Z Section Modulus predicts maximum stress ( Section Modulus predicts maximum stress ( σ) on subperiosteal (outer) surface subperiosteal (outer) surface M = bending moment M = bending moment I = cross I = cross -sectional moment of inertia sectional moment of inertia y = distance from centroid y = distance from centroid to surface to surface Z = section modulus Z = section modulus
Structural Changes in Adulthood 1. Bone material is continually being absorbed and reforme (remodeling 2. Bones adapt to changes in mechanical loading through life (modeling)
Structural Changes in Adulthood Structural Changes in Adulthood 1. Bone material is continually being Bone material is continually being absorbed and reformed absorbed and reformed (remodeling). (remodeling). 2. Bones adapt to changes in Bones adapt to changes in mechanical loading through life mechanical loading through life (modeling). (modeling)
The mechanism. Skeletal Loading and Strain Stimuli a Stresses cause loaded bones to distort slight a These minute changes in shape or dimension are strains Strains are detected at the cellular level a Bone is adapted to maintain a specific level and frequency of daily strain
The Mechanism: The Mechanism: Skeletal Loading and Strain Stimuli Skeletal Loading and Strain Stimuli Stresses cause loaded bones to distort slightly Stresses cause loaded bones to distort slightly These minute changes in shape or dimension These minute changes in shape or dimension are strains are strains Strains are detected at the cellular level Strains are detected at the cellular level Bone is adapted to maintain a specific level Bone is adapted to maintain a specific level and frequency of daily strain and frequency of daily strain