figures and shown in fig1 and 12 designate d l diameter at the bottoms 26 of the extensions 25 s depth of slotting equal to d 1 in the remaining figures t thickness of original plate corresponds to t in the other figures it is to be noted in fig1 that when a body such as a plate with the backing ribs 18 and additional bars 28 is rolled compression forces are active in section 30 and tension forces act at section 31 the boundary 32 between sections 30 31 is referred to as a gt gt neutral axis lt lt ______________________________________5 slots in are cut p 5 sl inplate rolled to 24 34 id d 24 in depth of slots is 0 155 s 0 155 in depth of contour is 0 045 34 c 0 045 in original plate thickness 0 400 t 0 400 in height of backing bars 3 8 34 b 0 375 in ______________________________________ 2 the closing of the slots due to metal compression u03b4w 1 is equivalent to the difference between the circumference at the bottom of the slots and the circumference at the neutral axis 32 c m is the circumference of the neutral axis 32 and 3 the closing u03b4w 2 of the slot 21 due to geometry this is equal to the difference between the circumference c s at the bottom 26 of the slots 21 and the circumference c l at the inlets 23 of the slots 21 it can be seen from the above that the present invention provides a significant advance in the art as it brings about the possibility of providing.