I just modelled a single square plate of size 50x50 and thick 1 and applied a force on two nodes(total force is hence 100). The software i used is nastran. The force vector is shown as arrow in the image. My doubt is all the points in the plate should have the stress=100/area=100/(50*1)=2. But in the four nodes, two have a stress of 1.90 and two others have 2.03. Any body can explain this?