我的理解是,减小厚度,因而增加柔性(actually reduce stiffness)。但如果根部没有原角,你的应力应是无穷的,有现员的结果应是不准确的。不信你可以mesh细一些,你将得到更大的应力。if meshing is refined again, you would get bigger stress again. Durability you get is meaningless.
When adding radius on bottom of beam,it would be compressive upon receiving top bending load.so it will increase stress level because stiffness is increased.