Jaipur Foot Project: Computer Simulation for Determination of Static and Cyclic Stresses

Open Access
Author:
Somers, Sarah Marie
Area of Honors:
Bioengineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Margaret June Slattery, Thesis Supervisor
  • Peter J Butler, Honors Advisor
  • Elizabeth Cunningham Kisenwether, Faculty Reader
Keywords:
  • Jaipur Foot
  • cyclic stress
  • fatigue life
  • prosthetic
Abstract:
The purpose of my thesis is to explore the attachment mechanism that is currently in place to attach the Jaipur prosthetic foot to an artificial limb. The Jaipur foot is a handmade wood and rubber-based foot that is distributed to patients in need in India free of cost. The problem is that the foot to ankle attachment zone is often the first region to fail. This is due to the current design which creates stress concentrations at the attachment zone. The current design is a simple ledge for the limb to sit on and four screws around the ankle through the limb, which is usually a PVC pipe, into the rubber and wood of the foot. In addition to the stress concentration created at the holes, the holes allow water to seep into the wood interior and eventually cause it to rot. I have analyzed the current design through computer modeling. My thesis is composed of two multiphysics models. One model measures the stress due to the stationary forces applied to the ankle and the second model tests the stress due to fatigue over a period of fluctuating stresses that imitate a stride. I predicted that the foot is failing due to the stress concentrations at the screws. Arizona State University, Massachusetts Institute of Technology, and Penn State are all collaborating on research surrounding the Jaipur foot. The problem with the Jaipur foot is that it does not meet many international standards to get funding from sources like the United Nations or the Red Cross because each foot is handmade. Therefore, the universities are working together to improve the foot so that it can be mass produced quickly and cheaply. I hope that, overall, my project can help the collaborating universities improve the design of the Jaipur foot to include some aspects that allow for easy attachment to a prosthetic leg. I have compared the maximum stresses that will result from normal use of the Jaipur foot and leg assembly to acceptable standards and failure points of the materials that make up the assembly. I hope that the results of my study will allow the collaborating universities to move forward in their study of the Jaipur foot and redesign of the foot and leg assembly.