Fasteners—usually the less glamorous part of a mechanical design—have been grabbing headlines lately. First it was a lack of fasteners that created (or was at least blamed for) the first delay announcement for the Boeing Dreamliner. Now two metallurgists have put out a book that really dredges up the past. In “What Really Sank the Titanic” , coauthors Jennifer Hooper McCarty and Tim Foecke say that substandard rivets were responsible for the rapid descent of the supposedly unsinkable vessel. Metallurgical testing of 48 rivets recovered from the Titanic showed that slag concentrations were at 9 percent, six or seven percent higher than they should have been. Slag is a brittle byproduct of the iron making process. Design engineers put the weaker rivets in areas expected to see less stress, such as the bow. Unfortunately, that is right where the Titanic scraped an iceberg. McCarty and Foecke postulate that fewer compartments would have burst if better rivets had been used. It’s possible, they say, that the Titanic could even have limped into Halifax. They also suggest that the bad rivets may have resulted from a rush to get the boat built at a time when rivets were in tight supply.
At IMTS last week, Stratasys introduced two new multi-materials PolyJet 3D printers, plus a new UV-resistant material for its FDM production 3D printers. They can be used in making jigs and fixtures, as well as prototypes and small runs of production parts.
Plastic bags can become useful as either raw materials for plastics or feedstock for fuel. It's when they're not recycled that they become a major problem. That's what California's bag ban will prevent.
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