Stress Analysis: Elbow Flexion
The load was applied downward at the last two holes of the arm. The load used here was far in excess of what the arm was expected to experience- the forearm and its corresponding frame weighed about 10lbs together, while the simulated weight applied in ANSYS was 15lbs perpendicular to the frame. At most, the stress that the forearm plate was exposed to was 985 psi, which, compared to the yield strength of the aluminum (40ksi), shows that the forearm design is very safe.
Stress Analysis: Shoulder at Rest
A load of 16lbs was applied downward where the arc would connect to the upper arm segment. The stress was most concentrated at the point around which the arc would rotate, peaking at 5628.6psi.
Stress Analysis: Shoulder Extension (Bending Load)
A moment was positioned at the three right holes, where the arc was attached to the upper arm, as with the previous trial. The moment was 192lbin. The figure to the left shows that this moment only resulted in a stress of 12,303psi. This likewise produced the most stress at the point where the motor shaft was attached.
A 16 lb load was applied to simulate the force acting on the arc when the arm was lifted to its highest most point. In this case, the stress was mostly concentrated around the “neck” of the arc, with a maximum of 1413.5psi, This and the previous trials performed on the shoulder arc show that the aluminum used was not at risk for yielding or failure during its use by a patient.