Premium
Mechanisms of Improvement of Fracture Strength in Laser‐Surface‐Modified Ceramics
Author(s) -
Jagannadham Kasichainula,
Narayan Jagdish
Publication year - 1989
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1989.tb09706.x
Subject(s) - materials science , overlayer , fracture (geology) , composite material , laser , ceramic , compressive strength , fracture mechanics , optics , chemistry , physics
Three mechanisms of improvement in fracture strength of laser‐surface‐modied ceramic materials are proposed to explain the experimental observations of more than 50% increase in fracture strength. First, the improvement in fracture strength by about 50% is considered to arise from either a complete or partial closure of crack surfaces at the interface of the laser‐modified overlayer. The second mechanism of improvement in fracture strength is derived from the physical displacement of the crack tip away from the free surface when a laser‐modified layer is introduced. Thus, the critical crack size, defmed as a crack that propagates with decreasing energy, is increased almost 100%. The Wid mechanism is based upon the compressive stresses introduced in the laser‐modified region. The fast cooling rates attained after laser irradiation are responsible for development of regions of compressive internal stresses. These sources of improvement in fracture strength are analyzed and the results of the calculations compared with experimental results. Through the present understanding of the mechanisms of improvement in fracture strength, it has become possible to calculate a critical thickness of the laser‐modifed layer. It is concluded that the possible improvement of fracture strength is achieved when the thickness of the laser‐modified overlayer is equal to or greater than this critical value.