E45, 2010:Properties of Materials Santa Rosa Junior College Ductile - PowerPoint PPT Presentation

E45, 2010:Properties of Materials Santa Rosa Junior College Ductile to Brittle Transition Temperature(DBTT) of a Hotdog Ben Miller, Cameron Roberson, Joe Mazzanti

Our Inspiration  Our first idea was to find the tonal quality of guitar strings  Guitar string samples failed without any data  Our second idea was to test Younes's hotdog claim, but it was only a joke.  Jokingly asked Younes about the Hotdog experiment, and he thought it was a good idea, so here we are.

Theory  A hotdog (or any object) will vary in ductility and brittleness with respect to temperature.  Younes said that at a certain temperature, a hotdog should be strong enough so that you can, “hammer in a nail with it”.  Finding the DBTT of a hotdog will allow us to predict where the hotdog is most able to hammer in a nail.

Theory  To measure the DBT of a Hotdog we used a pendulum with a .5 kg weight attached.  With the length of the string, mass of the weight, and velocity, we are able to find the kinetic energy needed to break the hotdog

Theory

Setup Liquid Nitrogen Storage

Setup Insulating container for hotdogs inside and out See us add the liquid nitrogen!

Original Setup Motion Detector Laptop with Logger Pro Weight Connected to String

The revised setup String (50 cm) 500 g. mass Motion detector Hot dog and holder If you don’t understand this slide, come see for yourself.

Setup Thermocoupler

Making the Temperature Profile Tem perature Profile of Hotdog Temperature = 26.749Ln(m inutes) - 106.73 0 0 5 10 15 20 25 30 35 -50 Tem perature( degrees C) -100 -150 -200 -250 Tim e( m inutes) Please note that the temperature values are adjusted by -5 ° C due to some error in the thermocoupler.

Logger Pro sample See the trial that corresponds!

Sample Calculations Find theoretical velocity of the pendulum at the instant before impact: = − V 2 g ( h h ) theoretica l 0 f m = − V 2 ( 9 . 8 (. 95 m . 51 m ) theoretica l 2 s = m 2 . 937 s Final velocity equation derived in earlier slide.

Sample calculations Energy required to break a hot dog sample: 1 − 2 2 m(V V ) theoretica l actual 2 1 m m = − 2 2 (.5kg)(2.9 37 1.489 ) 2 s s = 1.602J

DBT theory explained In all, we ended up with six decent data points. Not enough to form the high quality curve you can find in a textbook. The point of inflection (concave up to concave down) is the DBTT. We plot kinetic energy required to destroy the hot dog against the temperature that the hot dog was at when it was destroyed.

DBT Graph DBT of a Hotdog 2.5 2 Energy required to break ( J) 1.5 1 0.5 0 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 Tem perature ( degrees C) The point of inflection exists at about -30 ° C It took us between 17 and 20 minutes to reach DBT

Younes on trial Now that a reasonable temperature for DBT has been found, we must test a hot dog to see if Younes’s claim stands. Hot Dog after warming for less than 15 mins. Hot Dog after warming for 18 min.

Conclusion Younes is right. It is possible to hammer in a nail with a hot dog. Our DBTT is in a range of about + or - 10 ° C. Some sources of error Other sources of error include the string we used, the timer we used, and the range of the motion detector, among other things.

Conclusion How to eliminate errors: If we were to experiment again, we would definitely replace our string on the pendulum. We would use a rod attached to a ball bearing so our mass does not miss our sample or hit the frame of our support structure. We would also run multiple timers on our different groups of hot dogs in order to keep better track of their temperature/time ratio.

Special Thanks to: The SRJC Chemistry Department: for their advice concerning liquid nitrogen The SRJC Physics Department: for lending our group all the equipment (excluding hot dogs and nitrogen) required to run our trials. And lastly…

Our lab mascot That was Fantastic!!!