After a new structure had been designed, calculations were completed using Python. The Python script determined the spring constant and damper coefficient to ensure that the structure’s material would have the additional energy absorbent characteristics to withstand the peak loading force. The results of the Python predictions was a spring with a constant of 360 lbf/in and a damper with a coefficient of 14.5 lbf*s/in. These characteristics were then added to the simulation model, and a simulation was used to verify the model could withstand the indicated forces. The final force applied to the foot was the Loading Force. All of the user’s weight will be transferred through the ball joint and into the cup of the foot. Because the peak load predicted by the python script under test conditions was approximately 7000 N in the “up” position, we chose this value and position for static testing.

With all the materials squared away, the group could run the simulation. The simulation that the group is doing is when the foot is at its maximum extended distance (the damper is all the way extended). This is because the maximum values of the forces that are applied to the foot occur at this point. The model is considered static and the simulation is simulated the model at the instance of time when the force is applied. If the model can withstand the maximum amount of forces, then it will be able to withstand the rest of the loading forces as the damper compresses and foot becomes dynamic.Each simulation will produce three simulated model: strain, stress and displacement. Stress and strain measure the amount of stress and strain throughout the entire structure. The goal for these two models it to have as much uniform stress and strain values as possible (the more of the same color there is the better). The displacement model shows how far each part of the structure moved. The goal for these models is to have all little movement as possible (the more red, the higher the displacement).

The red regions indicate areas of large displacement. For reference, the displacements here are in the millimeter range, and does not represent sufficient deflection to cause permanent deformation. It is also important to note that some of this movement can be attributed to the use of the spring restraint. The group simulated the ABS plastic model. Because the parameters were calculated in python for ABS as the primary material, stresses on the order of the yield strength were anticipated.

Plastic - Strain Simulation