1. On the Lusitania, the reason the ship sunk was because of the war. It was shot by German torpedoes from submarines. For the Lusitania, there wasnt much in terms of engineering issues that made it sink. One of the reason that can be a cause the Lusitania to sink, was the longitudal compartments in the bottom of the ship. Because these compartments were watertight, it made it so that the water would have a hard time evening out leading to a capsize. The Titanic also had some problems with led to the sinking of it. One reason that could have let it sink was the overconfidence of the captain because he had never gotten into an accident at sea. The builders of the Titanic also decided to build 2 ships, the Olympic and the Britanic, at the same time. These ships were similar in size so the quality of the materials being used might not be standard. This was found to be true based off the steel from both the hull and the rivet from the Titanic. Both were found to have more traces of elements that worsen the material strength. This was certain in the chart between the Titanic's hull, Lock Gate, and ASTM A36 steel. The ratio between Mn and S were more than double that of the Titanic. The weather was another important factor that lead to the sinking because at very low temperatures, the energy needed to fracture steel was a lot smaller. Another thing that most think was the largest reason for the sinking was the rivets that held the hull together. The rivets were found to have been weaker than standard rivets which containted less slag. Something I found interesting, but it makes sense fi you think about it, is that if the Titanic hit the iceberg head on, there might have been a possibility that it might have been able to stay afloat longer. This makes sense because the damage of the Titanic was along the bottom of the hull and it broke open multiple watertight compartments. However, if they hit head on, there might have been significant damage to the front, but the water damage might have only been to the front compartments evening the water level.
Steel has many variations that change the internal structure of it. According to the World Steel Association, there are over 3500 different grades for steel. The such wide varieties come from different chemical compositions in the mixture. Depending on what you add or subtract from the composition of the iron and oxygen, it results in steel has different structural strength, heat resistance, durability, formability, weldability or ductility. In structures such as building, the type of steel used is reinforced steel. This steel is a combination of concrete and steel. This specific kind of steel is used because concrete is cheap and does not rust but it is not good under torsion. While steel is able to resist a large amount of tension. Both of these are also good materials to fit together because of their coefficient of thermal expansion are similar. In bridges, there are a few kinds of steel used with different properties. These can be heat treated steel, carbon steel, and high strength steel. Heating steel is a good way to make it stronger because after heating steel to a certain temperature, it will allow the steel to absorb carbon. When in steel, carbon increases the hardness of the material. Heat treated steel can change other properties such as shear strength and tensile strength.
2b. Impact tests are an important property for materials to indicate which part of them will most likely fail or to test the extend of a material. Learning the tension, and torsion is important to see how that material would fail. It is also important to forensic engineering when they see engineering disasters because they would be able to see how certain materials fail and what kind of impact could cause it.
This link is a downloadable pdf on a weight drop test of a U-shaped concrete. This study found that the cracks on the concrete were all around the same area. It shows the compressive strength of the many trials on concrete that were tried. They concluded that when the concrete was put in this certain orientation, the crack was going to happen in a predetermined area. This is a very helpful thing to find because that means that if the piece of concrete were to fail, you have a general idea on where it will break. With this information, you would be able to either strengthen the cracking point, or have a preventative measure to stop the crack from completely seperating the concrete.
The test in this link is the izod impact test. It is similar to the Charpy impact test but the material being held is in a different orientation. Both tests are able to show the aftermath of a material hit in a certain direction. Both of these tests are able to show us the effects of a large object hitting certain things and show engineers which materials will need to be paid more attention to so that they are not going to fail.