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Titanic materials research--英国论文代写范文精选

2015-09-15 | 来源:51due教员组 | 类别:更多范文

51due英国论文代写网精选代写范文:“Titanic materials research”。泰坦尼克号是一艘奥林匹克级邮轮,于1912年4月处女航时撞上冰山后沉没。当时在全球范围内引巨大轰动,而船上1500多人丧生。本篇论文告诉我们,这艘船沉没的主要原因有两个,脆性断裂弱铆钉和船体钢板的问题而引发。

There are two main causes of Titanic sinking: Brittle fracture Weak rivet Facts of the failure in the Titanic steel: From the sample steel that be taken from the hull of the ship, metallurgical analysis was done. There were found that the steel contain the phosphorus which is slightly higher than normal, while the sulphur content is quite high, accompanied by a low manganese content. The presence of relatively high amounts of phosphorous, oxygen, and sulphur is tends to make the steel more brittle at low temperatures.

Brittle fracture is a rapid of cracks through a stressed material. The crack is usually travel so fast and almost no plastic deformation before failure occur. To determine the steel’s mechanical property, Charpy impact test were used to measure the brittleness of a material in the hull of the Titanic. Below are the Charpy impact test comparison between modern steel and Titanic steel in the hull plate. With a large force, the sample of modern steel bent without breaking into pieces; it was ductile. Under the same impact loading, the Titanic steel, on the right, was extremely brittle; it broke in two pieces with little deformation.

The comparison of modern steel and Titanic steel is shown by the graph below: Brittle fracture is a failure of a metal by crack propagation and with the absence of ductility When the titanic samples were examined with a scanning electron microscope, the grain structure of the steel was found to be very large, this coarse structure made it easier for cracks to propagate. Weak Rivets factor. On impact, the rivets were either sheared off or the heads popped off because of excessive loading, which opened up riveted seams. Also, the rivets around the perimeter of the plates elongated due to the stresses applied by the water, which broke the caulking and provided another inlet for the water. When the iceberg hit along sections of the Titanic's hull, the rivets were sheared off, which opened up riveted seams. Also, because of the tremendous forces created on impact with the iceberg, the rivet heads in the areas of contact were simply popped off, which caused more seams to open up.

The diagram show the mechanism occurs right after the Titanic hit the iceberg. The rivet head popped up right after the shear-stress occur. This is two ways in which the brittle fracture damaged the Titanic’s hull. The maximum shear-stress can be interpreted using the equation below: τ_〖max 〗⁡〖in-plane〗 =√(((σx-σy)/2)^2+〖τ_xy〗^2 ) Rivets need to be harder than the materials being joined, they are heat treated to various levels of hardness depending on the materials ductility and hardness. Rivets come in a range of diameters and lengths depending on the materials being joined, head styles are either flush countersunk or pan heads. The wrought iron rivets that fastened the hull plates to the Titanic's main structure also failed because of brittle fracture from the high impact loading of the collision with the iceberg and the low temperature water. The theories that can be applied are theories of failure, which is the fracture of the brittle material is caused only by the maximum tensile stress in the material, and not the compressive stress.

Conclusion: The failure of the hull steel resulted from brittle fractures caused by the high sulphur content of the steel, the low temperature water on the night of the disaster, and the high impact loading of the collision with the iceberg. When the Titanic hit the iceberg, the hull plates split open and continued cracking as the water flooded the ship. Low water temperatures and high impact loading also caused the brittle failure of the rivets used to fasten the hull plates to the ship's main structure. -H

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