Diagrma de esfuerzos estructuras, metodologia

U0.C01.

Describe the differences between Materials Science and Engineering.

We can define the Materials Science as the “discipline that studies the relationship that exists between the structure and the properties of materials”. On the other hand, we can define Materials Engineering as the “discipline that designs the structure of a material to achieve a certain set of properties based on a correspondence between structure and known properties.” In this way, we can affirm that in Materials Science, existing phenomena are studied, and in engineering, we seek to create based on our improvement needs, drawing on previous knowledge.

Another point of differentiation is found in the aim of their designs. Scientists "design experiments to validate theories" while engineers "design machines capable of validating theories."

While scientists "prefer abstract knowledge (although they rely on tacit knowledge)" engineers "prefer applied knowledge".

U0.C02.

According to your criteria, what property /ies would you look for in the blade material of a knife?

-Corrosion resistance: The ability of the steel to resist deterioration because of reaction with its environment

-Hardness: A measure of the steel's ability to resist permanent deformation

-Toughness: The steel’s ability to absorb energy prior to fracturing

- Ease of Resharpening

- Edge Retention: The ability of the steel blade to hold an edge without frequent resharpening

- Hardenability: The ability of a steel to be hardened (through the heat-treating process)

- Strength: The steel’s ability to resist applied forces

- Ductility: The steel's ability to flex or bend without fracturing

- Initial Sharpness: The sharpness of the blade "out of the box"

- Wear Resistance: The ability to resist wear and abrasion during use

- Manufacturability: The ease with which steel can be machined, blanked, ground, and heat-treated (made into a blade)

- Stiffness (meaning modulus): the extent to which it resists deformation in response to an applied force

U0.C03.

In the past, plastic bicycles have been tried on several occasions, but they were very flexible. What property limited their use according to this? Justify your answer.

Flexibility is lack of stiffness. The stiffness of a structure depends on its shape, size and value of Young's modulus (E). We can mention that the value of the Young’s modulus (E) is a design-limiting property in design for stiffness. In bicycle design the values of E offered by plastics are insufficiently large. To increase the stiffness, plastic can be reinforced the with carbon or fiberglass.

U0.C04.

According to your criteria, what property /ies would you look for in a glove to be used to operate an oven?

-Low thermal conductivity: hands should be protected from high temperatures (to avoid burns)

-Flexibility: they are used with hands (they are articulated)

-Tolerance of water (to be washed)

-Maximum operating temperature: it should be high (ovens reach temperatures over 200 degrees C).

U0.C05.

According to your criteria, what property or properties would you look for in the material for the filament of a light bulb?

-Good Electrical conductivity

-High operating temperature

-Ductility (ductility to enable it to be drawn to fine wire)

U0.C07.

Identify three applications where it is necessary to use a material with high rigidity and low weight. Justify your answer.

-Paperboard for boxes: a rigid material is needed so that the box can hold the weight of the objects it contains without breaking. If the box broke, it would not be used to transport objects. In addition, as its function is the transport of goods, it cannot have a high weight.

-PET for food packaging: it is a plastic of high rigidity, as it must contain substances without deforming and when caught it must maintain the shape. In addition, because it is used for food, it cannot have a high weight because it would hinder its handling.

-Polypropylene (PP) for orthopaedics: must be rigid because when applied forces (when tightening the teeth if it is a dental splint or when walking in the case of a stabilizing orthosis) must maintain the form to fulfil its function of restraint. In addition, it cannot have a high weight because they are used by human beings in their functions of locomotion.

U0.C08.

Steel is often coated with a thin layer of zinc when used exposed to the weather. What characteristics do you think this coating brings? What precautions do you think should be taken when producing it? Do you think that the recyclability of steel will be affected?

Zinc acts as a protection against atmospheric corrosion of sheets and pieces made of steel in its different alloys. The function of this metal is to act as a physical barrier that isolates the metal substrate from the medium and the corrosive agents.

When producing it, caution should be taken when making the coating since it should be homogeneous and without pores. Through the pores or uncovered parts, Steel could be oxidized and we could not visualize this oxidation.

It is also important to use only the necessary amount of zinc to save on material costs.

The presence of the zinc coating on the steel does not restrict the recyclability of the assembly, since it is possible to separate and recover the two original metals taking advantage of the fact that the volatilization temperature of the zinc is lower than the melting temperature of the steel.

U0.C09.

Aluminum has a density of 2.7 g / cm3. Suppose you want to produce a composite material based on aluminum but with a density of 1.5 g / cm3. Design the material with that density. Is introducing polyethylene with a density of 0.95 g / cm3 an option?

To produce a material with a density of 1.5 g / cm3, we would need a material with a density considerably lower.

A possible option would be nylon 66 with a density of 1.14g / cm3, obtaining the following composition:

[pic 2]

[pic 3]

[pic 4]

As for its density, polyethylene could be used, obtaining the following composition:

[pic 5]

[pic 6]

[pic 7]

U0.C10.

Describe the enabling materials property of each of the following and why it is so:

(a) silica tiles for the space shuttle; (b) steel for I-beams in skyscrapers; (c) a cobalt chrome molybdenum alloy for hip implants; (d) polycarbonate for eyeglass lenses; and (e) bronze for sculptures.

1. During the landing on Earth, the space shuttle reaches extreme heat levels as it enters the Earth's atmosphere. Because of this, silicates must have a low thermal conductivity to prevent heat from transferring from the surface of the shuttle to the interior.
2. It must be strong to withstand the heavy weight of the structure.
3. It should have wear resistance, because it is in continuous friction due to movement. It must also be strong, since it must support the weight of the body. Finally, it must be biocompatible (it cannot be degraded or toxic).
4. The polycarbonate must be transparent to be used for vision. It must also be shock resistant so it does not break as easily as glass lenses.
5. It must be resistant to corrosion since the sculptures are usually exposed to the external environment. It also has to melt to give the desired shape to the sculpture.

U0.C11.

Describe the enabling materials property of each of the following and why it is so:

(a) aluminum for airplane bodies; (b) polyurethane for teeth aligners (invisible braces); (c) steel for the ball bearings in a bicycle’s wheel hub; (d) polyethylene terephthalate for water bottles; and (e) glass for wine bottles.

1. When designing an airplane, we should try to reduce its weight as much as possible (taking into account that it must resist the weight of the load) in order to achieve less force needed to lift the plane into the air. The lighter the plane, the lower the cost and the use of fuel. Among the advantageous characteristics of aluminium, we find strength, weight and corrosion. In this way, the aluminium supports the load of the airplane well without supposing a heavy material that would make impossible the flight of the airplane. In addition, the resistance to corrosion is important for its application in airplanes since the airplanes are exposed to the outside and can withstand pressures, temperatures and extreme humidity, in addition to the friction of the air.
2.  Each person needs personalized teeth aligners, that is why the material must be easily formable to give it the desired shape. In addition, this must be transparent, because teeth aligners are used daily and aesthetically to be transparent disguise their use.
3. Among the advantageous characteristics of steel, we find high strength and hardness, which is necessary because its function in this application is to reduce friction between metal surfaces
4. Polyethylene terephthalate is recyclable, a very useful feature for water containers, one of the most necessary and therefore commercialized products in the world (high consumption equals high contamination, so it should be recyclable). In addition, It is a linear thermoplastic polymer, with a high degree of crystallinity. Like all thermoplastics can be processed by extrusion, injection, injection and blow moulding, preform blowing and thermoforming. In this manner, we emphasize that it is formable.
5.  The glass container is inert, hygienic, does not interfere with the flavour of food and beverages or the composition of perfumes and medicines, thus guaranteeing the original quality of its contents. To maintain the taste of the wine for long periods, the Glass bottles are a good choice. The glass has a good chemical resistance, so it keeps the wine well without losing its properties or acquires flavour from the container. The glass is neutral in relation to the product that it packs, it does not maintain any chemical interaction with its content and can store any product throughout its useful life. It does not allow the transfer of oxygen or carbon dioxide; therefore, it does not alter the colour or flavour of the contents of the container. Nothing goes through the glass or escapes from the container. The inertia of the glass also makes it possible for the products packed with this material to have validity periods superior to other materials, up to twice as much. The same happens when it is discarded, the glass container resists the aggression of substances and does not degrade in the environment. Finally, glass has tensile strength and sufficient compressive strength for good performance against impacts and pressures, either in the production line and packaging or in the transport of the package or final product already packed.