Effect of cyclic bending on the notch sensitivity to fracture

Abstract

An experimental investigation on the fatigue behavior of mild steel shaft is presented. A newly developed machine in Mechanical Engineering Department, BUET, was useq to test the fatigue behavior of mild steel shaft. Specially, notch sensitivity of mild steel shaft with V-notches were examined in tenus of fatigue life of the notched specimens and compared with those of. plain mild steel specimens. The experiments were done at higher stress level. Three notch angles were selected as 30°, 60° and 90°. Inclined loading was permitted in the machine with a view to introduce the combined effect of tensile stress and flexural stress on the fatigue life of the specimens. The effect of tensile stress over flexural stress was noted. The effect of notch angle on fatigue life of mild steel specimens were investigated. Maximum stress levels were selected in the range of 60 percent to 85 percent of ultimate tensile strength of plain specimens. The effect of notch- root radius of V-notched specimens were also investigated. Two sets of V-notched specimens were selected to test the size effect of the specimens on the notch sensitivity to fracture. All the tests were done in the laboratory environment at ambient temperature.