Subcritical crack growth in glass, rock, and cementitious material was investigated experimentally by Double Torsion (DT) test. Especially, relations between the crack velocity and the stress intensity factor were investigated, controlling the temperature and humidity. It was shown that the relations between the crack velocity and the stress intensity factor in glass and rock were affected by temperature and humidity. When the temperature and the relative humidity were higher, the crack velocity at a given stress intensity factor was higher in both glass and rock. It is considered that subcritical crack growth in glass and rock is controlled by stress corrosion. On the other hand, the relation between the crack velocity and the stress intensity factor in cementitious material was insensitive to the environmental condition in this study. It is concluded that the nature of subcritical crack growth in cementitious material is quite different from that in rock.
In classical fracture mechanics, it has been postulated that the crack propagates rapidly, once the critical stress intensity factor (fracture toughness) has been reached. In fact, the crack can propagate even when the stress intensity factor is lower than the critical stress intensity factor. This phenomenon is called “subcritical crack growth” (Atkinson 1984, Atkinson & Meredith 1987). Subcritical crack growth is one of the main causes of time-dependent behavior. Information on time-dependent crack propagation is important for considering the longterm stability and lifetime of brittle materials. In this study, subcritical crack growth in brittle materials was investigated. Especially, the relation between the crack velocity and the stress intensity factor was determined experimentally by a fracture mechanics test, and dependence of subcritical crack growth on the environmental conditions, such as temperature and the relative humidity, was investigated. Soda-lime glass, rock, and a cementitious material were used.