## General Mechanical

#### Affect of load path on my stress results.

• Rameez_ul_Haq
Subscriber
I am curious and eager to know how will changing the load path abruptly affect the stresses within my ANSYS model? What is the theory and background? How can it result in stress singularities?nShould I expect the same results, as shown by ANSYS, due to sudden load path change in the reality as well?n
• peteroznewman
Subscriber
You ask a general question, but there is not a general answer. If you give a specific example, then we can talk about that example.nA specific example is a snap fit analysis, where the red part is moving downward. Obviously, as the snap hook passes the undercut edge on the blue part, that will be an abrupt change in the load path and have a huge effect on the stress in the parts, both in reality and in the ANSYS model.nStress singularities is a separate topic and independent of changes in load path. There is a stress singularity in the square interior corner at the base of the snap arm.n
• Rameez_ul_Haq
Subscriber
Kindly consider this picture and the region marked in blue. Assume the top-left end to be fixed and the extreme right end of the structure has a force applied along -Z direction. nSince there is a sudden change in the load path in the region marked in blue, I thought this causes very high stresses within that region. If that is a sharp corner, then those are singularities (verified by mesh convergence). If there is a sharp fillet, then still the stresses are going to be immensly high (relative to the rest of the structure). If the fillet's radius is increased, then the stress intensity and its concentration also decreases. What I wanted to ask is that why does this happen? Is it because of sudden change in load path? Whats the theory behind it? Or is it just all natural?n
• peteroznewman
Subscriber
A perfectly sharp interior corner has a stress singularity which means the mathematical solution of the PDEs that describe the stress is infinite.nWhen you put a fillet in that interior corner, the stress is finite. The larger the blend radius, the lower the stress.nHere is a good video using ANSYS.nHere is a good video that is more general for any FEA tool.n