Blog Post 11: Preliminary FEA for Design Concept 2

Here are the results of the first round of Finite Element Analysis I carried out on my second design concept:

Gripper:

I attained the results seen above by simulating the force exerted by both the compression springs on their respective mounts and in turn the equal reactive force exerted on the gripping face by the jar lid, the 5Nm of torque exerted by the jar lid was also applied to the same gripping face.

You can see from these results that the component in its current state is going to be prone to failure near the compression spring mounts whilst high stress concentrations are also prevalent where the racks meet the gripping face. The edges of the spring mounts will need to be supported more effectively and rounded off to allow the force from the springs to dissipate further into the surrounding material, only then will it be able to withstand these forces.

Bottom Section:

I decided to run FEA on the entire rotating bottom section as results taken from the ring cover/base plate and traction pads separately would have yielded results significantly less representative of the device’s intended operation. In this study, 5Nm of torque was applied to the top of the assembly with fixed points being located on the traction pads and grippers as these will be the first points of contact between the device and the jar lid. It is clear to see that there are multiple points of failure present on the sides of the grippers and so component optimisation at this stage needs to be based around the addition of support material at these points to negate the torsional stress caused by the unscrewing motion.

Top Section:

It is clear to see that results from FEA carried out on the top section (plunger) show an even distribution of stress within the component's walls, indicating that material reductions can be made to the lip of the top geometry without affecting the structural integrity of the component. The 100N of downward force simulated in this study is purely an estimate of the typical force the end user will be able to apply. Given that this equates to an 11kg weight being placed on the device, I think that 100N is by no means unrealistic, especially if you consider the fact that people use their body weight to operate devices of this nature.

To do:

• Add material to, or round off the gripper's spring mount to negate the high stress caused by its sharp edge and remove material where obsolete.

• Remove obsolete material from traction pads, top and bottom sections.