WWII Welded Merchant Vessel Structural Failures (Fleet-Wide)

The 1946 US Navy report data — 4,700 Liberty ships, ~1,000 with fracture casualties, 24 strength-deck fractures, 8 ships lost, 26 lives lost. The USS Schenectady at dry dock and USS Esso Manhattan at sea cited as the canonical photographs. Used to motivate the postwar interest in Griffith's flaw-size theory.

We had a number of problems, and this is the 1946 US Navy report on design and methods of construction of welded steel merchant vessels. It's an investigation the US Navy ran right after World War II, because during the war they built Liberty ships, and they were building some of them from laying the keel to sailing away in 2 weeks at the height of the war. They really learned how to pump them out. They built 4,700 Liberty ships, of which a thousand suffered casualties involving fractures. 24 vessels sustained a complete fracture of the strength deck — the top deck would give strength in bending. One vessel sustained a complete fracture of the bottom, eight vessels were lost. Of these, four broke in two, 26 lives lost. The famous picture of the USS Schenectady sitting at dry dock, never having been out to sea — it just decided to break in two one day, sitting at dry dock. If you go to a fracture book, this is the classic book they usually show. What they don't show is one of the plates from this book of the USS Esso Manhattan, where the same thing happened out in the middle of the ocean, which was a lot worse than doing it at dry dock. They lost a few ships.

So, it turns out — we learned about this property of toughness around the turn of the 20th century, around 1900. That Charpy bar — it was just celebrated about five years ago, the 100th anniversary of Charpy testing, and it's still used. But what happened was in World War II we had some problems with the Liberty ships. Anybody know the Liberty ship story?

Hard numbers: 4,700 welded vessels built, 970 had fracture casualties, 24 complete strength-deck fractures, 8 lost, 4 broke in two. Established why post-WWII fracture mechanics arose at three institutions.

From the 1850s or 1880s until the 1950s, that's what all the mechanical and civil engineers, design materials engineers, designed to: strength. And then came World War II and the Liberty ships. I've already shown you some of the Liberty ships and how they broke in two. But I don't know that I showed you the numbers.

Tom reads from the postwar damage report — 4,694 ships, 970 with fracture casualties, 24 complete hull fractures, 26 lives lost. Frames the rest of the lecture as the story of how welding technology had to be invented to support mass-produced welded ships.

So I did find the part in the report. 4,694 [Liberty ships] floated — literally ships born to join the war effort. 970 of these vessels suffered casualties involving fractures, 24 sustained complete fracture of the hull, one sustained complete fracture at the bottom, eight were lost or broken due to brittle fracture, 26 lives were lost. The fractures came from a combination of low temperatures and stress.

The fleet-wide statistical case (4,694 / 970 / 24 / 8 / 4+4 / 26) sourced from the 1946 report. Distinguished from the Schenectady case proper, which is the iconic image; this is the underlying epidemiology.

If you look at the data: 4,694 welded steel merchant vessels were built by the Maritime Commission. These were not all Liberty ships, some were T1 and T2 tankers. 970 suffered casualties involving fractures. By casualty I mean a metal casualty, not a person casualty — though some of them probably suffered the other type too. 24 sustained a complete fracture of the strength deck, one vessel sustained a complete fracture at the bottom, eight vessels were lost, four broken in two, and four were abandoned after fracture occurred. 26 lives were lost in these structural failures.