ME 412
Class No. 14937
S. F. Felszeghy

Spring 2009
1Apr. 2Photoelasticity (Demo only)
2Apr. 9Photoelasticity
3Apr. 16Photoelasticity
4Apr. 23Photoelasticity
5Apr. 30Compressed Split-Ring
6May 7Shear Center of Channel Beam
7May 14Buckling of Columns
8May 21Adhesive-Bonded Joints
9May 28Fatigue
10Jun. 4Fatigue


History of CR-39

Perhaps the most important single development in the history of plastic lenses came out of an experimental program being conducted during World War II at the Columbia Southern Chemical Company, now the Chemical Division of PPG Industries. They were involved in the quest for a plastic substitute for window glass, and formulated a series of just under 200 experimental polymers. It is the 39th of these materials which we, and the whole industry, use today as the basis for virtually all plastic ophthalmic lenses. The material, commonly referred to as CR-39 (the 39th Columbia Resin), is allyl diglycol carbonate. It has the product advantage of being thermosetting rather than thermoplastic, so will not soften and distort at elevated temperatures. It must, however, be cast rather than molded. Itís most unique property, and the one which makes it so well suited to ophthalmic application, is its scratch resistance. It is by far the most scratch resistant of the optical plastics.

  • Strain Gage Knowledge Base, by Vishay Micro-Measurements

  • Inelastic Buckling

  • LOCTITE WORLDWIDE DESIGN HANDBOOK, 2nd Edition (Archived) (Discusses adhesives and joints.)

  • 3M Scotch-Weld Epoxy Adhesive DP-460 (Data Sheet)

  • Rotating Beam Fatigue Test Machine

  • Updated April 3, 2009
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