Different Poisson’s ratios Shear stress at interface-bonding problems.

• Different Poisson’s ratios• Shear stress at interface-bonding problems

• Less stress concentration when placed centrally

Load-Transfer

• Affected by bonding characteristics at interface– Frictional/adhesive characteristics– Orientation of interface relative to loading

direction– Surface microstructure/texture

• True only when bonded surface is perpendicular to loading direction

• Bonded case, both compressive and shear at interface, shear > compressive for small angles

• Press-fit, get a tensile hoop stress in bone to prevent expansion, and maintain equilibrium-abnormal loading

• Rigidity of stem affects– Bone stresses (may cause resorption)– Interface stresses (may cause loosening)

• Non-cemented stems tend to be canal filling and thicker---hence….(more stiff, more stress shielding)

• Bone stiffness-VERY IMPORTANT

SENIOR DESIGN??