AutoCAD Inventor :: Decreasing Mesh Size Drastically

I'm currently working on a model where I'm subjecting a vertical wire (5 micron radius, 20 micron height) to a transverse load. I made an assembly of a 18 micron length section and a 2 micron length section, so that I can apply my force to the 2 micron tip, while leaving the bottom face of the wire fixed. I am trying to find the minimal force needed to fracture the wire (i.e., altering the force until the max stress hits the material's ultimate tensile strength). However, I've realized that decreasing the mesh size drastically changes my results, Obviously, decreasing mesh size should increase the accuracy of the results. Instead, by decreasing the mesh size, I actually am diverging from my results.