Numerical simulation and experimental testing for static failure prediction in additively manufactured below-knee...

Area of Science:

• Biomedical Engineering
• Materials Science
• Mechanical Engineering

Background:

• Customized transtibial prosthesis sockets are crucial for amputees.
• Additive manufacturing (AM) offers potential for cost-effective socket production.
• The mechanical fracture behavior of AM lower limb prostheses requires further investigation.

Purpose of the Study:

• To propose and validate a novel experimental and numerical method for assessing the mechanical strength and fracture behavior of additively manufactured lower limb prosthetic sockets.
• To evaluate the accuracy of the finite element method (FEM) using Hashin's damage model for predicting socket failure.
• To establish a basis for selecting optimal socket thickness for safety and performance.

Main Methods:

• Reverse-engineering of a transtibial socket using computer-aided design (CAD) from an amputee's residual limb.
• Fabrication of acrylonitrile butadiene styrene (ABS) sockets using fused filament fabrication (FFF).
• Experimental testing of socket strength and fracture, coupled with FEM simulations using Hashin's damage model.

Main Results:

• Experimental fracture of a 4 mm thick socket occurred at 918.5 N, initiating at the lobe corner.
• FEM predicted the failure load with a low error of 2.45% (896.6 N).
• FEM accurately predicted failure loads for sockets of varying thicknesses (3, 5, and 6 mm).

Conclusions:

• The developed experimental and FEM approach provides a dependable method for static failure testing of below-knee prosthetic sockets.
• Hashin's damage model is effective for simulating the mechanical behavior and fracture of layered AM sockets.
• This work enables a factor-of-safety (FoS) based selection of socket thickness for personalized prosthetic fitting.