Abstract
The purpose of this study is to develop a simulation method for predicting the effect of shape and dimension on shear strength, deformability and fracture behavior of knock-off bolts with circumferential notch and axial hole. Shearing tests for four types of knock-off bolts with various notch depth and axial hole diameter for constant cross-sectional area are conducted. Shear strength of these bolts is almost same value due to same cross-sectional area. On the other hand, the knock-off bolt with a shallower notch has larger deformability. Ductile cracking from notch of knock-off bolts unloaded at maximum load is observed. It is necessary for predicting shear strength and deformability of knock-off bolts to consider ductile crack initiation and growth. Stress states near notch tip of knock-off bolts depend on the angle to loading direction and are influenced by notch depth. The tensile/shear combined stress state dependent ductile damage model is proposed for predicting ductile crack initiation and growth from notch of knock-off bolts. The shear strength and deformability predicted by simulation based on the proposed ductile damage model present good agreement with experimental results. The effect of shape and dimension of knock-off bolt on shear strength and deformability is estimated by means of the developed simulation method. It is demonstrated that cross-sectional area and ratio of notch depth to bolt radius are dominant factor for shear strength and deformability, respectively.
