Soda-lime Glass Specimens Research Articles

Slow crack growth of indent cracks in glass with and without applied stress

The slow crack growth behavior occurring in dynamic fatigue and post-indentation fatigue with no applied stress was compared for indented soda-lime glass specimens in six different environments at room temperature. A significant difference between the fatigue behaviors in the two methods was found, indicating that the post-indentation fatigue (slow crack growth) is unique but that such an approach is not appropriate to evaluate fatigue parameters for use in life prediction. The existence of a plateau region in the post-indentation crack growth-time data was attributed to a fatigue limit for each test environment, as verified by the aging strength data.

Effects of polyaxial stress state on fatigue behavior of soda-lime glass.

Soda-lime glass specimens with an indented induced flaw at the center were fractured under a constant load and a cyclic load applied by the four-point bending of plates, concentric-ring loading of plates and diametral compression of disks, respectively. All glass specimens showed a susceptibility to static and cyclic fatigue failure, and their lifetimes increased with decreasing maximum applied stress. Equivalent time-to-failure obtained from the cyclic data, using the assumption that there is no enhanced effect of cycling on the rate of subcritical crack growth, were compared with the static time-to-failure data measured under polyaxial stress states. The influence of cyclic loading on fatigue life was not significant in cases with uniaxial tension, but the cyclic loading effect was obviously seen in both cases of tension-compression and equibiaxial tension.

Effects of polyaxial stress state on static fatigue behavior of soda-lime glass.

Soda-lime glass specimens with an indented induced flaw at the center, were fractured under a constant load applied by the four-point bending of the plates, concentric-ring loading of disks, and diametral compression of disks. Then, after indentation, the specimens were quenched in oil to remove the residual tensile stress near the crack tip. The time taken until failure increased with decreasing applied stress, and the degree of the increase was significantly higher in the diametral compression than in other stressing modes. This result was completely contrary to our previous report where a vacuum annealing treatment had been employed to remove residual stress. Further, the scatter in the fatigue data for equibiaxial tension was obviously less than that in the previous report. The subcritical crack-growth parameters, n, determined from a straight line on a logarithmic plot of the fatigue life time as a function of the applied stress were 15.2 for diametral compression, 9.7 for equibiaxial tension, and 9.1 for uniaxial tension. The higher value of n in diametral compression can be attributed to the fact that the crack growth was restricted by the higher hydrostatic compressive stress.

Temperature measurements in shock-loaded glass specimens with very thin aluminium resistors

Temperature measurements in shock-loaded soda-lime glass specimens, with very thin aluminium resistors (of 0.1 mu m thickness), are presented. These measurements are similar to those in earlier works with copper resistors embedded in Plexiglass targets and they show a very good agreement with the calculated temperature rise in the shock-loaded glass specimens. This enhances the author's confidence in the embedded thin-resistor technique as an accurate means to measure the temperature rise in shock-loaded insulators.

Effect of hydrostatic pressure on the fracture strength of soda-lime glass. (Investigation with respect to subcritical crack growth)

In order to examine the effect of subcritical crack growth on fracture strength under multiaxial stress by considering subcritical crack growth, soda-lime glass specimens having a controlled surface flaw introduced by Knoop microhardness indentation were fractured by four-point bending under different hydrostatic pressures up to 100 MPa and different stressing rate conditions. For both as-indented specimens and specimens without residual stresses, it was found that the fracture stress evidently increased under hydrostatic pressure of 100 MPa and a high stressing rate condition, as subcritical crack growth was fully restricted under those conditions.

Comparison of Uniaxial and Biaxial Strengths for Test Pieces with Controlled Flaws

Indentation cracks are used as controlled flaws in soda-lime glass specimens for failure tests in uniaxial and biaxial loading. The inert strength is independent of loading type within the scatter of data. This result is discussed in relation to the conclusions of other workers who have reported systematic differences in similar comparative tests on specimens containing natural flaws.

The Application of the Single-Edge Notched Beam to Fracture Toughness Testing of Ceramics

AbstractThere is a need for easy-to-fabricate fracture toughness specimens for ceramics. The single-edge notched beam satisfies this need, except that the American Society for Testing and Materials (ASTM) specification for notch root crack depth is difficult to achieve in ceramics using standard metallurgical methods. Finite element techniques are used to demonstrate that a minimum ratio of crack depth to notch root radius of 0.5 is sufficient for a valid test in a ceramic. These calculations are confirmed by experiments on soda-lime glass specimens.