Toward sheet testing by dynamic bending.

Behaviour of specimens arranged of steel sheets of various thickness into a V Gharpy sample under conditions of dynamic bending has been investigated. The theoretical analysis into the dependence of the sheet thickness B1 on the “crack driving force” Gc shows that the function Gc(B1) can be split into four zones characterized by different course of fracture. In the first zone ductile cleavage accurs and the Gc(B1) relation is linear. The second zone is characterized by origination of complex configuration of the fracture surfaces of comparable thickness, which results to fractures well-demanding from the view point of energy. In the third zone the mixed fracture originates. That part of curve Gc(B1) is originating in principle by the transient curves Gc (t) of specimens of a greater thickness. The fourth zone is characterized by occurrence of brittle fractures only.From the experimental part of the work it follows, that the results acquired with the structural weldable steels are in reasonable conformity with the following equation Z•Bk51=k6 where, Z=KCVmax-KCVmin/RpdynB1|tp|/t is a dimensionless parameter describing behaviour of specimens at the transition from a cleavage to ductile fracture.