A Study of the Effect of the Ion Exchange Method of Chemical Tempering on a Macroflaw in Soda-Lime Glass

摘要

The work examines the strengthening effect of the ion exchange method of chemical tempering on a macroflaw in glass. Use of a macroflaw allows a quantitative fracture mechanics analysis of the amount of strengthening. Precracked soda-lime glass specimens were treated for various lengths of time in a potassium nitrate salt bath held at lengths of time in a potassium nitrate salt bath held at 365C. The behavior of the macroflaw while being treated and at fracture was closely observed. The strain energy release rate, G sub c, and the fracture toughness, K sub c, were found by using the double cantilever cleavage technique of measuring fracture surface energies. The average strengthening which occurred at this temperature was found to be almost linear with time with a maximum increase of G sub c of approximately 300 per cent at twenty-four hours. The diffusion of ions was determined to be inward from the sides of the flaw rather than across the entire flaw tip. (Author)