Glass cracking

When a glass cracks, it shatters. When a crystal cracks, it cleaves along a flat plane. Explain why. 

All else being equal, a toughening effect occurs if the crack tilts or twists away from a planar geometry because this reduces the net crack driving force. In homogeneous materials such as glass, cracks tend to propagate in... 

Why does thick glass crack when suddenly heated ... 

After closing and unloading the vials, they have to be visually inspected for glass cracks, cake surface, and product splashes. This inspection can be done fully... 

Figure 25 Fully automatic inspection machine with vision system for inspection of vials filled with lyophilized product. 1, Inspection of cap, crimp, and shoulder and neck area 2, feed-in 3, inspection for heel cracks 4, inspection for particulates on the bottom of the cake or glass cracks on the bottom 5, inspection for particulates on the cake surface 6, inspection of side wall for glass cracks, product splashes, and melt-backs 7, inspection of side wall for glass cracks, product splashes, fill levels, melt-backs 8, exit of good product 9, exit of rejected vials class A 10, exit of rejected vials class B 11, inspection of neck and shoulder area. (Drawing and equipment, Seidenader Maschinenbau GmbH, D-85551 Kirchheim/Miinchen, and Seidenader Equipment Inc., Florham Park, NJ 07932.)...

As the arrow indicates, the flow of events is from A to B but not necessarily vice versa. In other words, B —> A is not necessarily true. For example, if the glass cracked, then it was not because you dropped it but you poured boiling water into it. 

Glass Crack initiation load /N Weibull modulus,... 

Glass Crack initiation load (in heptane)/N Brittleness / pm Young s modulus / GPa Vickers hardness / GPa Fracture toughness / MPam ... 

Figure 3. Diagonal length (a) and Knoop hardness (b) for the alumino silicate glass. Cracked indenta tions were as much as 10 p.m longer than uncracked indentations.

Most persons who have tried to make the electrode have found at some time or other that the glass cracks after the capillaries are drawn out. The incidence of this difficulty is less if the filled capillaries are allowed to remain on the hot plate for a few hours prior to pulling. A second major problem is in the etching process. The recess must be absolutely clean prior to plating. We can offer no help here except to say it is an art which takes time to learn. 

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