Flaws in glass

Inglis Equation. Relates the stress at the tip of an elliptical flaw in glass to the applied stress, the flaw length and the radius of curvature of the crack tip. 

Tantalum equipment is frequently used in conjunction with glass, glass-lined steel, and other nonmetalhc construction materials. Tantalum is also used extensively to repair damage and flaws in glass-lined steel equipment. 

Mono- and polycrystalline natural and synthetic materials are not subject to plastic strain and have no independent slip system. Stress concentration occurs in them at.crack tips and at flaws in the material, affecting the maximum strength which originates from the chemical or physical cohesion forces present. Non-plastic materials (crystals, rocks, ceramics, glass) show brittle cracks—forming at very low plastic strain—usually originating from surface flaws. 

Thus, when a glass item has slid across benches, rubbed against other pieces of glass, or has had incidental radical changes of temperature, it is soon covered with flaws. Most of these flaws are microscopic, but any one of them could result in glass failure when subjected to sufficient stress. 

There are two different mechanisms that produce stress (or strain) in glass physical and thermal. Either of these can cause a distortion of a glass surface that will create compression and tension at one or more points. If sufficient tension develops in the region of a flaw, the glass will fracture. 

The shape of glassware can be a clue as to how and/or where it can be used. The more rounded its comers, the better it can diffuse thermal stress. This idea is similar in concept to the sharpness of flaws and can be compared to Eq. (1.1), the stress concentration factor. Although that equation is intended to be used for surface flaws on glass, the principle is the same. 

No manufacturer can be considered totally dependable. Some manufacturers make some products better than other manufacturers, and they make some items better than other items. Therefore, in addition to the flaws that can be found in glass as just listed, do not accept the following flaws in manufactured glass items ... 

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