Materials Engineering

a) Compare planar densities in terms of atoms per area in terms of a, the lattice parameter for the (100), (110), and (111) planes for FCC. Which is the closest packed (densest) plane or FCC?

b) Compare planar densities in terms of atoms per area for the (100), (110), and (111) planes for BCC. Which is the closest packed (densest) plane for BCC?

The output shaft of a 120 Watt electric motor has a 20° full-depth steel spur pinion with 20 teeth and a module of 2.5 mm driving a 36-tooth gear attached to an air blower. The pinion speed is 100 rpm. Both the pinion and gear are manufactured from grade 2 steel using hobs shaping cutters, have a 18mm wide face, through-hardened steel at 200 Brinell, and are aligned in service such that kH = 1.6. For a service life of 108 cycles, a reliability of 99%, determine the bending fatigue stress and the associated factor of safety

A tidal power plant of single-basin type, has a basin area of (24+n1000) km². The tide has a range of 10 m. The turbine stops when the head on it falls below 3m. Calcualte the average power generated during one filling/emptying proces in MW. Assume the turbine-generator efficiency is 70% and the time taken as 22350 seconds. Take sea water density = 1025 kg/m³. n=57

18-3 For the case study problem, use helical gears and design the intermediate shaft. Compare your
results with the spur gear design presented in this chapter.

Case Study Problem Specification:

Section 1–18, p. 34, presents the background for this case study involving a speed reducer. A two-stage, compound reverted gear train such as shown in Fig. 18–1 will be designed. In this chapter, the design of the intermediate shaft and its components is presented, taking into account the other shafts as necessary.

A subset of the pertinent design specifications that will be needed for this part of the design are given here.

-Power to be delivered: 20 hp
-Input speed: 1750 rpm
-Output speed: 82–88 rev/min
-Usually low shock levels, occasional moderate shock Input and output shafts extend 4 in outside gearbox
-Maximum gearbox size: 14-in x 14-in base, 22-in height
-Output shaft and input shaft in-line
-Gear and bearing life > 12 000 hours; infinite shaft life

As engineer you are asking and based on your study to refrigeration cycles and absorption cycle to take the benefits of the available energy resources and to design absorption air conditioning system to your home and your car. a-With the help of sketch design your cycles b- What is your input and output in each case c- If these cycles are reversible what is the COP equation for each case

3. Describe 3 different cases having corrosion by determining the material (the alloys with the codes and composition), describing the component having corrosion, the environment making corrosion to the component. You will give suggestions to the user that will solve the corrosion problem. However, there are some constraints that you need to check. - The reasons for the corrosion should be different for all cases. - The environment, the material, the component should be different for all situations. - The suggestions that solve the corrosion problem should be different for all situations. - There is no option for changing the material.

Saturated water vapor has a flow rate of 1.5 kg/s and a pressure of 0.51 bar. The vapor is to be completely condensed to saturated liquid in the shell of a shell-and-tube heat exchanger. In this case, the water vapor enters and the water exits at the same temperature, which represents a case with infinitely high m_dot * Cp for this condensing steam application. On the tube side, city water is used as the cold fluid. The city water enters the thin-walled tubes at 17°C and leaves at 57°C. Assume an overall heat transfer coefficient of 2000 W/m2-K.

After extended operation, fouling causes the overall heat transfer coefficient to decrease to 1000 W/m2-K, and to completely condense the vapor, there must be a reduction in the vapor flow rate. For the same inlet temperature of the city water and flow rate of the city water, calculate the following:

11. Fouled NTU = ?
12. Fouled epsilon = ? (No need for derivation. Use the provided equation for Cr = 0)
13. Fouled qmax = ? Is there a reason for fouled qmax to be different from the clean qmax?
14. Fouled q = ?
15. What is the vapor flow rate required for complete condensation in the fouled exchanger?

If you have three samples Alluminum, Copper and Nylon and I do a full experiment on them to find their yield strengths, all the modulus data, their haderning and so forth, where would you use each model?

1. Alluminum.......
2. Copper........
3. Nylon......

Determine the heat transfer rate per unit width for a 0.9-m long plate with a surface temperature of 125°C for critical Reynolds numbers corresponding to (A) 10⁵, (B) 5 x 10⁵, and (C) 10⁶. Air flows over the plate at 25°C with a velocity of 25m/s.

Calculate the Reynolds number. R ⁢ e =

Hammering and shaping a hot steel block on an anvil is an example of: a) Open-die forging. b) Closed-die forging. c) Flashless forging. d) Impression die forging.

Resistance spot welding can be used to join sheets of _______ and_______. a) Rubber, steel. b) PVC plastics, copper. c) Stainless steel, leather. d) None of the above.

An advantage of forward extrusion over backward extrusion is: a) Lower pressure. b) Lower force. c) All of the above. d) None of the above.

In a rolling process, if both roller diameters reduce by 25%, then the required power to rotate the rollers would: a) Increase 25%. b) Decrease 25%. c) Increase 50%. d) Decrease 50%.

Which of the following bulk deformation processes are involved in the production of nails for lumber construction? a) Wire drawing, flashless forging, and impression die forging. b) Wire drawing, flashless forging, and rolling. c) Flashless forging, impression die forging, and upsetting. d) Extrusion, flashless forging, and wire drawing

The thickness of each of the two sheets to be resistance spot welded is 3.5 mm. It is desired to form a weld nugget that is 5.5 mm in diameter and 5.0 mm thick after 0.3 sec welding time. The unit melting energy for a certain sheet metal is 9.5 J/mm3 . The electrical resistance between the surfaces is 140 micro ohms, and only one third of the electrical energy generated will be used to form the weld nugget (the rest being dissipated), determine the minimum current level required.

A GTAW operation is performed on low carbon steel, whose unit melting energy is 10.3 J/mm3 . The welding voltage is 22 volts and the current is 135 amps. The heat transfer factor is 0.7 (convection heat loss of 30%) and the melting factor is 0.65 (conduction heat loss of 35%). If filler metal wire of 3.5 mm diameter is added to the operation, the final weld bead is composed of 60% volume of filler and 40% volume base metal. If the travel speed in the operation is 5 mm/sec, determine:

(a) The cross sectional area of the weld bead

(b) The feed rate (mm/sec) at which the filler wire must be supplied.

Describe your plan or countermeasures, regarding to developing a Cost Estimating Relationship, as an engineer in controlling the effects/impacts given by the following items from the perspective of Engineering Economics

- Direct labor hours

-. Machine hours

-. Number of units

-. Number of production runs

-. Number of orders