Very tasty. I'd like to know more about bone strength and breaking
properties for my students' "karate physics day" in mechanics, but
who can trust a popularized excerpt presenting gibberish like this?
Dan M
and more similar.
and the Phys-l thread: The thread is broken, so the below is where it becomes significant.
At the time of this conversation (thread) Dec. 2005, I had not taught engineering materials, so didn’t recognize that there were two confusions. Yes there is a measure of material strength measured in Joules, resilience is not the correct term. It’s impact strength, tho. resilience “sort of” does convey the idea. The standard tests are the Charpy, and Izod. The Charpy was the one we used in the lab. Our apparatus is a pendulum which strikes the notched [1] specimen held in a vice (at bottom dead center). The amount of energy to break the specimen reduces the amplitude of the pendulum, which is a measure of the energy expended in breaking the sample. We tested various “grades” of steel, and various heat treatments. I added one, not done by the previous instructors. I obtained some LN2 from UCSC to cool one of the samples, the result was a shock. The top half (above the notch) flew across the room and banged against the wall. The reduction in amplitude was not measurable This explained the pic. I had seen of the broken keel in the launch of a ship one very cold day. The article described a different test, one now common in HS labs, the three point force test. I attended, back twenty years ago?, a workshop at Vernier where we, inter alia, built bridges (IIRC, Duco cement and stir sticks), and then used a three point press. The criterion was, again IIRC, force /mass of the bridge.
bc … remembers “fondly” the course, as it was great fun!
[1] note the article mentioned notching.
p.s. I also had the students make samples for testing. One student brought in ice in the correct shape and ice made from jello Results: the ice similar to the cold steel, and, surprise, the jello had considerable strength.