Project Examples

Failure Analysis of a Prosthetic Knee

Course: 22.425 - Design Machine Elements
Semester: Fall 2005
Instructor: Chris Niezrecki
Partner: Village Empowerment Peru Project

In addition to mechanical designs for removing canal trash, three other students also worked on a Failure Analysis of a Prosthetic Knee. A single axle knee joint for an economical prosthetic leg was the subject for a static and dynamically loaded failure analysis. A prosthetic leg is a complicated mechanical machine of various components. From prior research performed by the capstone student group that originally designed the leg, the bracket for the knee joint was assessed as the component most susceptible to failure. Since a failure of the prosthetic leg could result in bodily harm to a human, the leg was created based on a safety factor of 4 incorporated into the design.

Also, students designed a ramp for a chiropractor, and assistive devices for a man with only four fingers. Challenges embedded within this S-L course centered on the theme of creating a good fit between student interest linked with an appropriate design challenge/ project. Students with a good match between interest and project expressed their S-L experience as, “the best S-L experience.” On the other hand, students expressed concern if they designed yet didn’t actually have the opportunity to build their design. Students experiencing the opportunity to complete and build a design expressed a greater appreciation for their S-L experience.

Learning objectives met by the S-L project were for students to:

  • Experience the design process, including working directly with a community partners
  • The principles of mechanics and commonly used failure theories were applied to the design and analysis of machine elements subjected to static and dynamic (fatigue) load conditions.
  • Elements studied included power screws, bolts, springs, bearings, gears, lubrication, shafts, brakes, clutches, and belts.
  • Student designs included a stress analysis or fatigue analysis that integrated recommendations
  • Write brief technical reports and incorporate drawings

Community objectives met by the S-L project:

  • Individual partners derived benefit through appropriate mechanical designs tailored to specific needs
  • The LNHP project produced reports that continue to serve as potential mechanical designs to address this ongoing community need