Skip to main content
2024 BMES Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Biomechanics

Biomechanics - Poster Session C

Poster D3 - Finite Element Modeling of Elastomeric Prosthetic Elbow Joint

Friday, October 25, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  A stable and controlled elbow prosthesis holds a promising future for the prosthetic industry, offering significant opportunities for people with disabilities who have suffered major upper limb amputation. The elbow's anatomy includes various stabilizing components. Creating a prosthetic elbow that mimics the abilities of the natural elbow with comparable stiffness, flexibility, and control is challenging. One significant issue is how stress is distributed throughout the model coupled with the overall flexibility of the joint. While many different prosthetic elbows exist, they are limited in the strength, flexibility, and shock absorption that they offer. As well as a good flexible prosthesis that can provide the full flexion range of natural elbow for a model to be acceptable, it should have a good range of stress distribution and the lowest stress possible. The stress distribution varies depending on the elbow's design. We analyzed the different geometries of an elastic elbow component to design a model with the least stress, best stress distribution, and overall stiffness of the joint.

Materials and

Methods:  The research used SolidWorks to conduct a design study of the Elbow model. In the analysis, we used a range of control variables for the inner radius, outer radius, and width of the model, as shown in Figure 1. The inner radius values were 0.2 to 0.8 inches in 0.2 inch increments, outer radius ranged from 1.0 to 3.0 in 0.2 inch increments, and width were 2.0 to 3.0 in 0.25 inch increments. Within SolidWorks, a static finite element simulation was created with a moment of 20 N*m was applied to one side of the model, while the other side was fixed. From the analysis, we acquired the stress distribution, maximum stress, maximum displacement, and the volume of elastic component for all values of the control variables.

We used Excel to organize the data and calculate angular stiffness and angular displacement. We put all the data acquired from the SolidWorks analysis into pivot tables. The tables showed the average maximum stress, volume, and angular displacement within the different parameters of the models. To visualize the data, we also used MATLAB to create graphs that compared the different parameters of the model results.

Results, Conclusions, and Discussions: The data showed that the outer radius had the strongest influence on the maximum stress throughout the model. This is evident in the Max Stress (Table 1), where a larger outer radius correlated with lower max stresses. The inner radius also played a role, though smaller. When the inner radius was close to the outer radius size, the model was weaker. Smaller inner radii, like 0.2 inches and 0.4 inches, resulted in stronger models with better stress distributions. Outer radius also has a strong impact on the stiffness of the model, as shown in Table 2. A larger outer radius also resulted in a greater volume of elastic components. Figure 3 shows the relationship between outer radius, inner radius, and volume for 2 different widths, and shows how volume increases as the radius and width increase and decreases as inner radius increases.

This study's results are significant for the biomechatronic industry. Knowing the optimal parameters for an elbow prosthetic can lead to models that closely mimic a real arm and joint. A strong, low-stress model reduces the risk of breaking under pressure, ensuring reliability. Additionally, a low-volume prosthetic ensures mobility, as no one wants a bulky joint that hinders daily use. However, larger volumes tend to correlate with lower stress for the geometries studied.

Acknowledgements (Optional):