Explain the following observations, using diagrams to illustrate your answer wherever possible:

(a) Steel nails used to hold copper roofing sheet in position failed rapidly by wet corrosion.

(b) The corrosion of an underground steel pipeline was greatly reduced when the pipeline was connected to a buried bar of magnesium alloy.

(c) Mild-steel radiators in a central heating system were found to have undergone little corrosion after several years' service.
(d) A reaction vessel for a chemical plant was fabricated by welding together stainless steel plates containing 18% chromium, 8% nickel and 0.1% carbon. During service, it was observed that the vessel corroded badly near the welds.

A five metre tall, 1 m diameter Flettner rotor mounted on a small cargo vessel, spins at 50 rpm in a steady beam breeze of 15 knots. What is the thrust generated by the rotor? The air density and viscosity may be assumed constant at 1.22 kg/m3 and 1.79 x 10‐5 Pa.s respectively. Note also that 1 knot = 0.514 m/s.   Which direction must the rotor spin to produce forward thrust?

Describe a typical polymer molecule in terms of its chain structure and repeat units. Use a specific example polymer other than polyethylene to illustrate the ideas

The origins of stiffness

Explain the relationship between the cohesive energy of bonding and the observed stiffness of individual bonds.

How does the stiffness of individual bonds in a solid affect the overall stiffness and elastic modulus of the material?

What is the atomic level mechanism of elastic deformation? In other words, what is occurring within a solid when it is elastically deformed?

(Amorphous vs semi-crystalline)

Using words and visuals, describe the amorphous and semi-crystalline arrangements of polymer chains when forming a solid. Using examples of specific polymers, explain why some types of polymer chains do not readily align and tend to be amorphous while others readily form semi-crystalline structures.

Describe a future innovation that you envision may occur during your Mechanical Engineering career (next 40 years), and what your engineering role would be in its development and/or production?

A signal has the functional form f(t) = 5sin(40πt) and is sampled at a rate of 30 samples per second. What false alias frequency would you expect in the discrete data? What sampling rate would avoid aliasing this signal?

A railway buffer consists of a pair of cylinders placed parallel side-by-side. Oil is present in each cylinder and is arranged to bypass through ports, thereby producing a damping resistance, which is proportional to the velocity of the piston within the cylinder. The magnitude of this resistance is 50 kN at a velocity of 0.25 m/s. Each cylinder also contains a compression spring, initially with negligible compression, of stiffness 65 kN/m. A rigid train of mass 250 tons is moving at a speed of 1.6 m/s and collides with the buffer. Determine the distance taken by the train before first coming to rest. Assuming that the train comes into contact and then become attached to the free end of the buffer. Determine the time it takes the train to come to a complete stop. Solution for this problem should show the position and velocity of the train.

What happens to an inventor within an organization,whose invention is not successfully commercialized? Have you seen examples?

Explain the procedure to generate a cylinder placed on top of a rectangular block using any CAD software.

2.

Phase transformations and microstructural control in Fe-C alloy system For the Fe-C alloy of eutectoid composition (shown below in the left graph):

1100

' 800 T TT

500

I I I I I I I I

a + Fe3C

100

M(50%) A/(90%)

1 10

50%

102 103 104 105 Time (s)

400_ I01.0 2.0 10_1

Composition (wt% C)

a) Name the possible types of micro-constituents in microstructures achieved by austeniticphase transformation when subjected to various isothermal heat treatments. [1]

b) Mark these micro-constituents directly on the time-temperature-transformation (ill)diagram (shown above in the right graph). [2]

c) Rank microhardness of these micro-constituents in increasing order. [1]

d) Using the TTT diagram, specify the final microstructure (in terms of micro-constituentsand approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. In each case, assume that the specimen begins at 760 °C and that it has been held at this temperature long enough to have achieved acomplete and homogeneous austenitic structure. [5]

Consider the brass alloy the stress-strain behavior of which is shown in the Animated Figure 6.12. A cylindrical specimen of this alloy 19 mm in diameter and 177 mm long is to be pulled in tension. Calculate the force necessary to cause a 0.00969 mm reduction in diameter. Assume a value of 0.34 for Poisson's ratio.

Find a materials property plot of elastic modulus and density.

Identify a composite, a polymer, and a metal with densities less than 3000 kg/m³ (Mg = 10⁶ g) and the highest possible elastic modulus. Provide an example of an engineering design that might require this combination of material properties and explain why those properties would be important. What design advantages could a polymer offer over a metal even though the polymer has a lower stiffness?

A paper on the ‘Hyperloop Alpha’ concept for a high speed transportation system was published in 2013. Since then, there has been a lot of hype, time, and money directed toward the concept. Your task this week is to evaluate the hyperloop concept purely from a 2D particle kinetics point of view.

For this assignment, the important specifications from the paper are as follows:

Urban cruise speed: 300 mph (480 kph)

Inter-city cruise speed: 760 mph (1,220 kph)

Axial Acceleration (along direction of travel): 1 g

Lateral Acceleration (normal to direction of travel): 0.5 g

Capsule weight (incl. passengers): 57,000 lb (26,000 kg)

Pylon support spacing: 100’ (30 m)

3. At a minimum, any motion path must be continuous in position, velocity, and acceleration to avoid impacts. Suppose the path deviates from the theoretical line by a distance h, due to a relative displacement of one pylon with respect to its neighbors. If we assume a polynomial path along these two pylon spacings, for a total distance of 2L, the lowest-acceleration shape that meets these end-conditions is given by the function:

y(x) = 64h((x/2L)^3-3(x/2L)^4+3(x/2L)^5-(x/2L)^6)

c. Assuming that the velocity in the nominal motion direction ( ˙x) is constant, so that v = ˙xˆI + ˙yJˆ, and assuming that y˙ ≪ v, so that y/v ˙ ≈ 0, determine an expression for the tangential velocity, the tangential acceleration, and the normal acceleration of the capsule as a function of the amount of deviation (h), the pylon spacing (L), and the nominal velocity ˙x.

d. At what position x does the peak value of the normal acceleration, an occur?

e. At the location of peak normal acceleration, you determined in part ‘d’, determine an expression for the radius of curvature ρ of the motion of the capsule as a function of the amount of deviation (h) of the pylon.

g. Could you allow the same h in a curved section of track? Why or why not?

h. Does this level of precision in straightness sound plausible? Based on the values you calculated, would you expect there to be any significant impact on the cost?

A mass of 5kg of saturated water vapor at 150 kpa is heated at a constant pressure until the temperature reaches 200 C. Calculate the work done by the steam during this process?