You are considering two columns with identical dimensions. One is constructed out of steel, the other aluminium, which will buckle at a smaller load? The euler formula for critical buckling force for column, pin jointed at both ends is given by Pcr = pi^2 EI/ L^2 if the end of the column are constrained to prevent rotation, how will the buckling force change?

In: Mechanical Engineering

When designing a column against buckling, how do you decide weather to use the Johnson or Euler formula in your calculations when computing the critical buckling load?

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Based on the Pb-Sn alloy phase diagram, explain why Pb-Sn
alloy was widely used as the solder material in the reflow
soldering process in the past and it is much less used in the
electronic packaging nowadays.

Figure Q1 below shows the equilibrium phase diagram of Lead (Pb)-Tin (Sn) alloy system.

Figure Q1 The equilibrium phase diagram of Lead (Pb)-Tin (Sn) alloy system

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Q2 The pump of a LiBr--water absorption refrigeration
system delivers (0.7 kg/s) of

solution. The absorption system operates at the following
temperatures: generator (I 10 'C);

condenser (40 'C); evaporator (lO 'C); and absorber (33 'C).
Calculate;

(a) The refrigerant mass flow rate, the refrigerating capacity, and
the COP of the system.

(b) The COP of an ideal heat-operated refrigeration system that
operates with the same

temperatures.

In: Mechanical Engineering

We will find the Moment of Inertia Moment and Polar Moment of Inertia of a U profile that will determine its dimensions by ourselves.

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steps to drill, boring and reaming for 30 mm diameter of
workpiece

In: Mechanical Engineering

Excellent combinations of hardness, strength, and toughness are
obtained from

tempered martensite. An employee in a heat treatment facility
austenitized an eutectoid

steel at 9500C for 45 min and finally allowed the steel to slowly
cooled in furnace. Do

you think the required tempered martensite structure was produced?
If not, support

your answer with a detail heat treatment that can be employed for
the steel.

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Water enters the condenser of surface type; the temperatures of the water that is used to cool the steam is 17oC and 28oC respectively. The pressure of the condenser is at 0.055 bar and 0.87 dry fraction. The overall heat transfer coefficient in the condenser is 3 kW/m2.oC. The condenser has three passes and tubes used have 17.6 mm internal diameter and 20 mm external diameter. If the flow area is 1.3 m2, Design the condenser. If the condenser is used to condense 240 tons of steam per hour.

In: Mechanical Engineering

- You are preparing a spaghetti dinner for guests when you realize that your heat transfer training can be used to answer some fundamental questions about the process. The pot you are using holds four liters of water. The atmospheric pressure is 101 kPa. When on its high setting, the electric stove heating unit consumes 1.8 kW of electrical power of which 20% is transferred to the surroundings, rather than to the water. The pot is made of 4 mm thick polished AISI 304 stainless steel and it has a diameter of 0.25 m. The burner diameter is also 0.25 m.

a.) How much time is required to heat
the water from 15 ^{◦}C to its boiling temperature?

b.) What are the temperatures of the outside and inside surfaces of the bottom of pot while the water is boiling?

In: Mechanical Engineering

For the given plane of a cubic crystal structure, find the followings

1. Miller indices

2. Type of a cubic crystal structure

3. Relation of lattice parameter "a" and the radius "r"

4. If the radius of the atom is "6 nm", find the planar density in atoms/nm

5. In your opinion, is it the densest plane of this cubic crystal structure? In case otherwise draw the densest plane of this cubic crystal structure and compare its planar density in atoms/nm2.

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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?

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Defects and Slip

Chromium metal has a metallic atomic radius of 0.200 nm. It shows plastic deformation via slip along the <111> directions.

a) What is the planar density (atoms/m2) for its densest family of planes? What is the magnitude of the Burgers vector for the dislocations that promote slip in chromium metal?

c) A chromium ingot has tensile stress applied at a 25° angle to the slip plane normal and a 63° angle to the slip direction. It experiences a resolved shear stress of 25 MPa. What is the total tensile stress applied to the ingot?

d) What is the maximum resolved shear stress, in any direction, for this applied tensile stress?

e) It is observed that polycrystalline chromium has a higher tensile stren than single crystalline chromium. Propose a reason for this difference in tensile strength.

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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

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A tidal power plant of single-basin type, has a basin area of
(24*+**n**1000*) km^{2}. 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/m^{3}. n=57

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**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

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