تشخيص الانبعاج لساق طرف صناعي متراكب

BUCKLING CHARACTERIZATION OF A COMPOSITE PYLON PROSTHESIS

Abstract

The prosthetic pylon is an essential part of the artificial lower limb, it is an exciting area of biomedical engineering today. Pylon is generally made of lightweight metal such as aluminum, titanium, and stainless steel, or an alloy of these. This research aims to develop prosthetic pylon by suggesting new composite materials to be used in its manufacture, making it lighter, less expensive, and more comfortable for the user.
Suggested samples comprise (which were with constant 2.5 mm thick) a constant number of perlon layers and different numbers (one, two, or three) layers of carbon or glass fiber layers at (0º/90º) orientation relative to the applied load (as reinforcement materials) and orthocryl (617H19) (80:20) lamination as a resin. The vacuum bagging technique was used in its manufacture.
The mechanical properties test as tensile, flexural, and buckling were carried out. Besides, a physical test, as the density test, was studied.
Theoretically, these properties were calculated using appropriate equations; it was a good agreement between experimental and theoretical results as the discrepancy percentage reached (6.4 %) only.
These results showed that the modulus of elasticity, tensile strength, flexural modulus, flexural strength, and critical buckling load increase when the number of layers of reinforcement fibers increases. Also, it was found that the better composite samples contain three layers of carbon fibers oriented relative to the applied load by (0 º /90 º). The ultimate tensile stress, critical buckling load, Young modulus, flexural strength, and flexural modulus for this sample were (204.5N, 175 MPa, 4.63GPa, 230.7 MPa, and 6.38 GPa) respectively.
Based on these results, two types of pylons were manufactured with thickness 2.5 mm), the first pylon from the sixth sample, which consists of (2 perlon, 3 carbon fibers, and 2 perlon) layers, and the other pylon from the third sample consist of (2 perlon, 3 glass fibers, and 2 perlon) layers.
The Buckling test for the two pylons made of composite materials in addition to the currently used metallic pylon made of stainless steel was performed to investigate the critical load and maximum deflection for each pylon.
Using the Finite Element Method (ANSYS WORKBENCH 17.2), maximum deformation, Von-Mises elastic strain, equivalent Von-Mises stress, critical buckling stress, and the buckling mode shape for the two composite pylons beside the metallic pylon were analyzed.
Validation of the experimental results (buckling test) was conducted by comparing with numerical results, where it was an excellent agreement between them as the discrepancy percentage did not exceed (3.01 %).
A case study was considered to verify the durability of the manufactured pylons proposed in the current study and compare it with the metallic pylons used in terms of strength, weight, flexibility, and user comfort. For this purpose, one of the patients at Babylon Center for Artificial Limbs was chosen. The patient was weighty (80 kg), height (1.7 m), and was (55) years old. The patient’s left leg was amputated below the knee; the ground reaction force was tested by comparing the results of parameters for gait cycle for the patient with the new pylons (I) and pylon (II) with their counterparts of the prosthetic leg with standard pylon. Relating to the foot rotation angle, the difference was decreased between the injured leg and the regular leg, where the improvement was by (95%) and (38%). At the same time, the step length has been enhanced by (75%) and (50%). In addition, the step time improved by (88%) and (66%) in pylon (I) and pylon (II), respectively.