Mechanical Load Assisted Dissolution (MLAD) Research

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Surface roughness evolution of medical implant alloy

Objective

  • Characterize the stress-assisted dissolution mechanism at modular joint implant interface
  • Characterize the roughness evolution by combination of contact and corrosion

Motivation
Modular implant and surface failure due to cyclic contacts between modular interlocked rough surfaces by human behavior in corrosive physiological fluid

  • Biocompatibility problem ex) inflammation and necrosis

 

Modular hip joint replacement and its interlocking surface. b) stem surface, c) tibial head surface.

Approach

  1. Experimental analysis of surface roughness evolution by alternating contact and dissolution test and optical profilometry measurement
  2. Normal compression test with cylindrical CoCrMo specimen as shown in figure at right.
  3. Utilizing FFT calculation of profilometry surface roughness data investigate the most dominant roughness mode change
  4. Numerical analysis of residual stress Surface Model Elastic-perfectly plastic rough surface (E = 230 GPa, σy = 450 MPa, ν = 0.3) Plane strain (2 – dimensional) Half infinite spatial model surface roughness characterized by parameter ; A/λ=0.003

Experimental Results


Surface Roughness Evolution of Preferential material dissolution by corrosion


Tapered stem surface profile and superposed FFT spectrum of specimen surface before and after contact

 

Single asperity dissolution of metallic implant alloy

Single asperity dissolution of copper

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