Mechanical Behavior of metallic Materials 2.6 D/d=1.5 3.0 D/d=2 2.2 M 2.6 20 Did= 3 k 2.2 1.8 16 D/d=5 1.4 1.0 D=15 0 4 a/d hole diam. /diam. shaft d) 2 3 ③大季
Mechanical Behavior of Metallic Materials
Mechanical Behavior of metallic Materials 4.2 b=d/4 3.8 d/8 3.4 3.0 3.0 2.6 2.6 2.2 2.2 k 1.8 ZaZa 1.4 1.4 1.0 1.0 02 0810.12 a/w rld (e) (f) CHONGOING UNIVENTTY
Mechanical Behavior of Metallic Materials
Mechanical Behavior of metallic Materials The maximum stress and strain level that any component may support decreases with increasing the stress-concentration factor in the completely elastic materials k,、b→kt1 E ③大季
Mechanical Behavior of Metallic Materials The maximum stress and strain level that any component may support decreases with increasing the stress-concentration factor in the completely elastic materials
Mechanical Behavior of metallic Materials Fortunately, stress concentrations in most materials will not result in the escalation of the local crack-tip stress to dangerously high levels. This potentially damaging stress elevation is avoided by plastic deformation processes in the highly stressed crack-tip region. As a result, the local stress does not greatly exceed the materials yield strength level as the crack tip blunts, thereby reducing the severity of the stress concentration CHONGQING UNIVENTTY
Mechanical Behavior of Metallic Materials Fortunately, stress concentrations in most materials will not result in the escalation of the local crack-tip stress to dangerously high levels. This potentially damaging stress elevation is avoided by plastic deformation processes in the highly stressed crack-tip region. As a result, the local stress does not greatly exceed the material’s yield strength level as the crack tip blunts, thereby reducing the severity of the stress concentration
Mechanical Behavior of metallic Materials Notch Strengthening Plastic restraint is developed in the necked region of a tensile bar as a result of a tri-axial stress state. the unnecked regions of the bar experience a lower true stress than the necked section and therefore restrict the lateral contraction of the material in the neck. Similar stress conditions exist in the vicinity of a notch in a round bar and the higher the axial stress must be to de form e aint The deeper the notch, the greater in the plastic consti sample CHONGQING UNIVENTTY
Mechanical Behavior of Metallic Materials Notch Strengthening • Plastic restraint is developed in the necked region of a tensile bar as a result of a tri-axial stress state, the unnecked regions of the bar experience a lower true stress than the necked section and therefore, restrict the lateral contraction of the material in the neck. • Similar stress conditions exist in the vicinity of a notch in a round bar. • The deeper the notch, the greater in the plastic constraint and the higher the axial stress must be to deform the sample