Material Analysis II

Materials Analysis II

After a group meeting where the material of the crane was discussed, we decided that cost was going to be a major issue as well as availability. Using the Materials Analysis it was decided that both Aluminium and Steel would be options for the material of the crane. The following data is the analysis of the different types of Aluminium and Steel available.

Aluminium
First to be analysed was the different types of Aluminium available. There is a wide variety of Aluminium available with varying grades of aluminium mixed with other materials. The beginning number, ranging from 1-8 of the 4 digit number represents the strength of the material. 1 being the weakest form, and 8 being the strongest.
The material will now be analysed. As alot of the numbers are the same, they have been given equal values for the analysis phase. Each section is worth 9 points and a maximum of 54 can be attained.
As alot of the data is similar or the same, the results are ranged quite close together. Out of the 9 materials available only 3 would suffice for the application. Aluminium 6061, Aluminium 6063, and Aluminium 7050. The reason for this is their strength is greater than the latter grades of Aluminium, the stronger the material the more resistant it will be to deformation under loads. The material must also be easily worked with, and due to grades above 7000 having poor weldability and corrosion resistant qualities, Aluminium 7050 must be ruled out. This leaves a choice between Aluminium 6061 and Aluminium 6063.

Steel
The material will now be analysed. As alot of the numbers are the same, they have been given equal values for the analysis phase. Each section is worth 9 points and a maximum of 54 can be attained.
From the table above we can see that there are some quite mixed results. This is due to the different types and grades of steel available. There are alloy steels which are mixed with other materials, and there are varying qualities of steel depending on its purity. Although the materials are very similar in regards to their properties, the two that would be considered for the crane would have to be the Carbon Steel 1023, and Cast Carbon Steel. This is because Carbon Steel has high strength characteristics as well as a low cost factor. In the crane industry alot of cranes are made out of a carbon steel as mentioned in the materials research. However, this is usually for very large cranes which will carry a much heavier load than compared to the crane we are designing. With this in mind we must consider the weight factor of steel compared to Aluminium. The weight of Aluminium is a considerable amount less than the weight of Steel. This can be seen from the Density of both materials. The more Dense the material the more it weights. For a crane that will need to be carried over rough terrain by people, the lighter and easier it is to transport, the better.

The data will be presented to the group in the next meeting, we will discuss further the choice between Aluminium 6061, Aluminium 6063, Cast Carbon Steel, and Carbon Steel 1023.

Material Anaylsis

¹ Aluminium 6061 is a commonly used grade, hence why it is used for the comparison.

² VCB-20 is a commonly used grade of carbon fibre found in the automotive industry, hence why it is used for the comparison.

³ Carbon fibre does not actually have a yield strength. It will always elastically deform in accordance with hookes law until its ultimate tensile strength (UTS). Once it reaches its UTS it will fail.

⁴ Grade 5 (Ti6-4) is a commonly used titanium alloy, found in many industry applications, hence why it is used for the comparison.

Evaluation of Materials

As there are 12 materials, a scoring system ranging from 1-12 will be used, 1 for the worst material and 12 for the best material in a given field.

The table clearly distinguishes the differences between each material, however cost is a more dominating factor and will have more of an influence over the decision of which material is chosen. This is to be discussed between the group and from then we will analyse and choose the final material.

Materials Research

Materials Research

Crane

The type of materials used in a crane generally tends to be Steel. Steel is an alloy of iron and a varying amount of carbon depending on the quality and strength required from the steel. For structures that do not need high strength properties a common form of steel known as carbon steel is used. Carbon steel contains less than 2% of elements other than iron and carbon. The factor that determines the properties of carbon steel is the amount of carbon present, this can range from less than 0.015% to more than 0.5%.

If a structure requires high strength properties, a variety of substances known as high-strength low-alloy (HSLA) steels are used. HSLA steels contain low levels of carbon, generally around 0.05%. They also contain a small amount of one of more other elements for the purpose of adding strength. The elements included can be chromium, nickel, molybdenum, vanadium, titanium, and niobium. Aside from being strong, HSLA steels are more resistant to atmospheric corrosion and are better suited to welding.

Crane Cables

Different cranes require different properties from the cables being used. Width, material, constructions are all varying factors with the cables. The width of the cable must be thin enough to maintain flexibility, but thick enough to be cope with the loads it carries. The material also must be flexible and strong for the same reasons. The construction of the cable will vary with different cables. There are also cables available with reinforced structures for high load operation. Cables will also feature properties such as spin and stress resistance closing, high breaking loads, knock and vibration resistance, and self lubricating properties.

For our structure, a simple carbon-steel alloy would suffice, it would be strong enough to withstand the load that crane would be dealing with. A thin cable would also be strong enough and flexible enough to deal with the specific application. Thin flexible cables and carbon steel will keep costs to a minimum, maintenance will also be less of an issue in regards to cost as they would both be easily replaceable and maintainable.

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Bearing Research - Finite Element Analysis

SolidWorks was used to create these studies which tell us how the bearings would behave under load. Three different types of bearing where studied and the most appropriate was chosen for our final group design. The three types of bearing studied were the roller, thrust and ball type of bearings. The force applied to the bearings was 490 N. This is because the force from the load being lifted would be divided between many bearing in the race.

Roller Bearing

Axial loading - 490 N

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Radial loading - 490 N

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This type of bearing has a low axial load capacity and high friction under axial loads.However, it has a high radial load capacity. This study also shows that the stresses exerted onto the bearing do not exceed the yield strength of the material (chromium stainless steel alloy).This means the bearings used on our design will not plastically deform under load.

Thrust Bearing

Axial loading - 490 N

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Radial loading - 490 N

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This type of bearing has a high axial load capacity but a lower radial load capacity. This study also shows that the stresses exerted onto the bearing do not exceed the yield strength of the material (chromium stainless steel alloy).This means the bearings used on our design will not plastically deform under load.

Ball Bearing

Axial loading - 490 N

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Radial loading - 490 N

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This type of bearing has a high axial load capacity and a high radial load capacity. This study also shows that the stresses exerted onto the bearing do not exceed the yield strength of the material (chromium stainless steel alloy).This means the bearings used on our design will not plastically deform under load.

From doing these studies we can see that the ball type of bearing would be the most suitable for use in our crane. This is because the ball type of bearing can handle axial and radial forces and also moments very well.