Subcritical crack growth of glass

Effects of composition and phase relations on mechanical properties and crystallization of silicate glasses

“…Lateral cracks and further residual stresses can be generated by the indentation process, and these might alter stress intensity at the crack tip and thus lead to erroneous fracture toughness values. [32][33][34][35] Hence the standard recommends removing the residual stress zone by grinding the indented face of the bend specimen. On the other hand, extra residual stresses can be generated as a result of the grinding process.…”

Mechanical properties of soda–lime–silica glasses with varying alkaline earth contents

“…Fracture toughness of the glasses was measured using bend testing with a controlled defect 14,15,16,17 . The standard therefore recommends grinding the indented surface of the specimen in order to remove the residual stress zone, however grinding can also introduce extra residual stresses in glasses 16 .…”

Crack growth of C(T) specimens and indentation cracks in glass

“…In this case, the maximum stress intensity factor for a semi-elliptical crack is calculated by [13] K I = Mo/L'zg)I# (2) wher~ ~ is the crack depth, ~the complete elliptic integral of the second kind, and M the correction factor. The average ratio £ /c of the crack depth ~ to the surface crack length c was taken to be 0.8 by observing arrest lines which show the contour of the developing crack front [9]. As can be seen in Fig.…”

“…The cracks were subjected to bend stress o in water with the four-point bend test apparatus [9]. The shape of the initial Knoop indentation crack is semicircular, but the crack grows gradually into a well-defined semi-elliptical shape, unlike the pyramid indentation cracks which include a lateral crack [9]. Figure 2 shows the crack velocity da/dt-stress intensity factor K_ curves for the C(T) specimens.…”