This past Sunday marked 100 years since the Titanic sank in the icy waters of the northern Atlantic Ocean. Yet after all this time, questions still remain about what really caused the ship to go down.
In her most recent video, materials scientist Ainissa Ramirez, at Yale University, looks at two theories of how metals used to build the ship could have contributed to the damage.
One theory is that the frigid water cooled the ship’s hull enough to change its mechanical properties from flexible to brittle. If so, the metal sheets would crack easily upon impact, instead of denting like a car that’s been in an accident. If the boat was in warmer waters when it hit the iceberg, perhaps the gash in the hull would have been smaller, Ramirez says.
In her video, Ramirez demonstrates how temperature can change flexible materials, like rubber, into brittle materials that shatter like glass. Rubber is a tangle of strands called polymers. Normally, individual polymer strings slide past each other like noodles in a bowl of spaghetti, she says. These strands stiffen as the rubber cools, making the material brittle and easily broken.
At the end of the video, Ramirez mentions another theory for how materials contributed to the Titanic’s demise: the rivets that held the metal sheets together were inherently weak. The manufacturing process for these rivets introduced clusters of impurities into the iron. These clusters disrupt and weaken the neat network of atoms in a strong metal. Clumps can lead to cracks. And cracked rivets cause open joints.
Metal workers used to identify strong rivets by listening for a ting as they pounded the rivets into a joint. But workers building the Titanic could not hear this sound because they pounded in the rivets using noisy hydraulic hammers, Ramirez says. Perhaps if they built the boat by hand, workers could have heard that these rivets were not ideal, she says.
If you’re hooked on materials, learn about the tiles that keep the space shuttle cool as it enters our atmosphere, how materials can convert heat to electricity to power a cell phone and more from Dr. Ramirez’s videos at Material Marvels.