The aim of this work is to find general expressions to determine the stress intensity factor of a one point bend beam like specimen, whether from the measurement of the applied load or the crack mouth opening displacement. The expressions, obtained by applying the superposition principle, involve the decomposition of the general case into three auxiliary problems. The solution of two of them (pure bending and three point bending) is well known, while the solution of the third (one point bending) is developed in the present work. The proposed expressions are compared to numerical results obtained by the finite element method and their accuracy is equal to or better than available expressions published elsewhere.

Abstract. The use of dynami c o ne-point bending tests as an alternative to three-point bending tes ts all ows fracture prope rt ies such as dynami c initi ati o n frac ture toughness to be obtained at hi gh strain rate. To perfo rm thi s kin d of test, experimental dev ices based on modifi cati ons of the Hopkinson bar ca n be used. Several autho rs have been proposed si mpli fied procedures to obtain the dynami c stress intensity fac tor, K,( t ), considerin g the specimen as a Timos henko crac ked beam subj ected to a concentrated load at the ce ntral cross-secti on. T he di sad vantage of thi s procedure is th at norm all y it is diffi cult to measure the force applied to the specimen in the above-menti oned tests. Here a simplifi ed met hod is proposed for the calcul ati o n of K 1 (I), based on an analys is of the behav io ur of a Timos henko cracked beam, know ing the di splacement of the point of loading, whi ch can be measured more acc urate ly than the applied load. The resu lts were compared with those of a fin ite element numeri cal simulatio n and good agreement was fo und.