Study on the arresting mechanism of two arrest-holes on moving crack in brittle material under impacts

Abstract

To develop the technique of arresting running cracks is essential because it can be used to protect cracked structures being further damaged. In this paper, a specimen of large semicircular edge crack with two arrest-holes (LSECTH) was proposed. The specimens were made of cement, river sand, fly ash and water. Impact experiments were carried out in the LSECTH specimens with different two-hole spacing (35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm and 70 mm) under drop-weight impacts. Crack propagation gauges (CPGs) were used to monitor the fracturing time and crack speed. The interaction characteristic between the crack and two arrest-holes was investigated numerically by the AUTODYN code. In the numerical models, the failure criterion of maximum tensile stress and shear stress were employed for the brittle material. The crack propagation path, the circumferential stress of crack tip and the stress state between the two arrest-holes were analyzed. The calculation results indicate that compressive stresses between the two arrest-holes induced by the shape change from circle to ellipse play a key role in confining the vertical crack propagation. Both experimental and numerical results indicate that the two arrest-holes have suppressing action on moving crack; as the two arrest-hole spacing decreases, the suppressing action intensifies.