ABSTRACT
Abstract Impact strength of material is usually evaluated by the impact bending test. However, impact fracture behaviour of a structural element is often quite different from the static behaviour. One example is the mechanical size effect due to the interference between stress waves, which is contrary to the well-known size effect of material under a static load. The effect of specimen size on dynamic bending strain is investigated using large and small strips, but dynamic strain distribution generated in a bending specimen is extremely complicated. Therefore, impact compression and torsional experiments were performed using a rod specimen and the size dependence in the results are considered theoretically. Impact fatigue experiments and impact fracture toughness tests are also performed. These results also show size dependence. All these results are due to the additive superposition of stress waves. Therefore, it is expected that the superposition of waves with reversed phase will reduce the magnitude of a stress pulse and thus improve the impact strength of the specimen. This is verified experimentally. Keywords: Impact bending, impact fatigue, impact fracture toughness, mechanical size effect, strain pulse, stress waves, wave propagation.
