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LIBERTY SHIP CONSTRUCTION WELDING CRACK
Engineers applied several reinforcements to the ship hulls to arrest crack propagation and initiation problems. Also contributing to failures was heavy overloading of the ships, which increased the stress on the hull. Many of the cracks were nucleated at an edge where a weld was positioned next to a hatch the edge of the crack and the weld itself both acted as crack concentrators. Because the hulls were welded together, the cracks could propagate across very large distances this would not have been possible in riveted ships.Ī crack stress concentrator contributed to many of the failures. Ships operating in the North Atlantic were often exposed to temperatures below a critical temperature, which changed the failure mechanism from ductile to brittle. She found that the grade of steel used to make Liberty ships suffered from embrittlement, in which materials become brittle. The cause of the failures was discovered by Constance Tipper, an engineering professor at Cambridge. Rather, the failures were caused by a design oversight.
![liberty ship construction welding liberty ship construction welding](https://www.bowdoin.edu/news/2021/img/liberty-ship-ssneal.jpg)
Though the work force was largely untrained in the method of welding ships together, it was not worker error that caused these failures. About 1,200 ships suffered from cracks during the war (about 30% of all Liberty-class ships), and 3 were lost when the ship suddenly split in two. Many early Liberty ships were affected by deck and hull cracks and indeed several were lost. The armament was a 4 or 5 inch stern gun, a 3 inch bow gun, two 37 mm bow guns, and six 20 mm machine guns.
LIBERTY SHIP CONSTRUCTION WELDING FULL
They were staffed by a full crew of about 44 men, plus 12 to 25 national guardsmen. The ships were 441.5 feet long, with a 57 foot beam and a 28 foot draft. The Liberty ship model used two oil boilers and was propelled by a single-screw steam engine, which gave the liberty ship a cruise speed of 11 to 11.5 knots. Because of this, early ships took quite a long time to build - the Patrick Henry taking 244 days - but the average building time eventually came down to just 42 days. Additionally, much of the shipyards' labor force had been replaced with women as men joined the armed forces.
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This was a new technique, so workers were inexperienced and engineers had little data to go on. The ships were designed to minimize labor and material costs this was done in part by replacing many rivets with welds. They were given the designation “EC2-S-C1,” the EC standing for emergency cargo. The Liberty class was designed to fill a void in merchant marine ships as the United States rapidly ramped up its war effort. Image: Wikimedia Commons - Liberty Ship at Sea Design of the Liberty Class The short timescale from design to construction, however, led to the inclusion of several fatal flaws in the ship design, and many ships were lost due brittle steel failures. Nearly 3000 of the ships were built in an extremely short period the first ship was built in just 70 days. Described variously as “dreadful looking” and an “ugly duckling,” the Liberty class of ships nonetheless came to represent the immense industrial might of the United States early on in the war effort. The Liberty ships were a so-called “emergency” class of ships developed during World War II.