“Vector method” was used in the calculation of the maximum bending strain (machine and specimen components) for circular and rectangular cross-section specimens under axial loading and bending. This method satisfactorily solved the orientation angle calculation problem for rectangular cross-section specimens (including thick and thin rectangular cross-section) caused by the testing machine component and the specimen component under the maximum bending strain, which is not solved in the ASTM E1012-12 and ISO 23788.