ME 3752 Chapter : ME 3752 HWSet3 Solution 311 1
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Answer the following questions briefly: a) explain the differences in the two major ways of expressing the fracture toughness of materials. Fracture toughness is defined as the resistance to applied force for cracking down. One is by finding the energy needed to fracture the specimen per unit volume. The other is by finding a critical stress intensity factor where the normal mechanical fracture process initiates. The former measures the mechanical energy needed to cause fracture using the tensile test or decide the impact energy required to break the specimen via the impact test. Ductile materials would resist fracture very efficiently and undergo plastic deformation, preventing failure, directly increasing its fracture toughness value. Brittle materials, however, give in easily without plastic deformation and simply fail under a certain load. The best method to improve fatigue resistance of materials is to introduce surface compressive stresses by shot peening, sand blasting, etc.
