Skip to main content

Manufacturing Science - short answer questions from AMIE exams (Summer 2018)

Answer the following (2 x 10)

What is the proof stress?

The proof stress of a material is defined as the amount of stress it can endure until it undergoes a relatively small amount of plastic deformation. Specifically, proof stress is the point at which the material exhibits 0.2% of plastic deformation.

A straight line offset at 0.2% strain is extended parallel to the linear portion of the graph until it meets the stress-strain curve. The stress at the intersection between this line and the curve is the value of the proof stress.

What is the proportionality limit?

The proportional limit is defined as the highest stress at which stress and strain are directly proportional so that the stress-strain graph is a straight line such that the gradient is equal to the elastic modulus of the material.

What is strain hardening?

Strain hardening also referred to as cold working or work hardening, is the process where metals are made stronger and harder through permanent deformation. 

Why intensifier is used in the AWJ machine?

The intensifier increases the pressure of the water to the required level. Usually, the water is pressurized to 200 to 400 MPa. Pressurized water is then sent to the accumulator. The accumulator temporarily stores the pressurized water.

Cold and hot metal spinning

  • Hot Spinning: In hot spinning, the metal blank is heated to forging temperature and then forming it into the desired shape. Hot spinning produces parts such as heads for pressure vessels, refinery equipment and large tanks.
  • Cold Spinning: Cold spinning process is similar to hot spinning except that the metal blank is worked at room temperature.

What is arc blow in welding?

Magnetic arc blow, also known as arc wander is the arc deflection caused by the distortion of the magnetic field produced by an electric arc current. When welding ferromagnetic steels, lack of fusion imperfections can be caused by uncontrolled deflection of the arc, usually termed arc blow.

What is twinning?

Twinning is a form of deformation caused by shear stress. The plane of atoms forms into two mirror-image planes along a boundary called the twin plane.

What is casting yield?

The efficiency, or yield, of casting, is defined as the weight of the casting divided by the weight of the total amount of metal poured. 

Expandable graphite mould is used for ⸻

Expandable graphite is also used in metallurgy to cover melts and moulds. The material serves here as oxidation protection and insulator.

What do you understand by the term "modulus extension factor" used in the design of riser in casting?

Modulus extension factor (MEF) is the effective ratio of the sand riser and riser sleeve. MEF values are determined by comparing the modulus of the sleeved riser with the modulus of the sand riser by using the solidification rate.

---

The study material for AMIE/Junior Engineer exams is available at https://amiestudycircle.com
Labels:

Comments

Post a Comment

Popular posts from this blog

Mechanics of Fluids (Solved Numerical Problems)

Numerical The surface Tension of water in contact with air at 20°C is 0.0725 N/m. The pressure inside a droplet of water is to be 0.02 N/cm² greater than the outside pressure. Calculate the diameter of the droplet of water. (7 marks) (AMIE Summer 2023) Solution Surface tension, σ = 0.0725 N/m Pressure intensity, P = 0.02 N/m 2 P = 4σ/d Hence, the Diameter of the dropd = 4 x 0.0725/200 = 1.45 mm Numerical Find the surface tension in a soap bubble of 40 mm diameter when the inside pressure is 2.5 N/m² above atmospheric pressure. (7 marks) (AMIE Summer 2023) Answer: 0.0125 N/m Numerical The pressure outside the droplet of water of diameter 0.04 mm is 10.32 N/cm² (atmospheric pressure). Calculate the pressure within the droplet if surface tension is given as 0.0725 N/m of water. (AMIE Summer 2023, 7 marks) Answer: 0.725 N/cm 2   Numerical An open lank contains water up to a depth of 2 m and above it an oil of specific gravity 0.9 for a depth of 1 m. Find the pressure intensity (i) at t...
Post a Comment
Read more

Design of Electrical Systems (Solved Numerical Problems)

Important note There is something wrong with this question paper. It seems that instead of "Design of Electrical Systems" the IEI has given problems from "Electrical Machines". You should raise a complaint to director_eea@ieindia.org in this regard. Numerical A 120 V DC shunt motor draws a current of 200A. The armature resistance is 0.02 ohms and the shunt field resistance is 30 ohms. Find back emf. If the lap wound armature has 90 slots with 4 conductors per slots, at what speed will the motor run when flux per pole is 0.04 Wb?​ (AMIE Summer 2023, 8 marks) Solution The back EMF (E b ) of a DC motor can be calculated using the formula: E b = V - I a R a   Given: V = 120 V I a = 200 A R a = 0.02 ohms Substituting the values into the formula: E b = 120 − 200 × 0.02 = 120 − 4​ = 116 V Now, let's calculate the speed (N) at which the motor will run using the given flux per pole (φ p ). The formula to calculate the speed of a DC motor is: N = 60×E b /(P×φ p ) Wh...
Post a Comment
Read more

Energy Systems (Solved Numerical Problems)

Wind at 1 standard atmospheric pressure and \({15^0}C\) has velocity of 15 m/s, calculate (i) the total power density in the wind stream (ii) the maximum obtainable power density (iii) a reasonably obtainable power density (iv) total power (v) torque and axial thrust Given: turbine diameter = 120 m, and turbine operating speed = 40 rpm at maximum efficiency. Propeller type wind turbine is considered. (AMIE Winter 2023) Solution For air, the value of gas constant is R = 0.287 kJ/kg.K 1 atm = 1.01325 x 105 Pa Air density \(\rho  = \frac{P}{{RT}} = \frac{{1.01325x{{10}^5}}}{{287}}(288) = 1.226\,kg/{m^3}\) Total Power \({P_{total}} = \rho A{V_1}^3/2\) Power density \(\begin{array}{l}\frac{{{P_{total}}}}{A} = \frac{1}{2}\rho {V_1}^3\\ = \frac{1}{2}(1.226){(15)^3}\\ = 2068.87{\mkern 1mu} W/{m^2}\end{array}\) Maximum power density \(\begin{array}{l}\frac{{{P_{\max }}}}{A} = \frac{8}{{27}}\rho A{V^3}_1\\ = \frac{8}{{27}}(1.226){(15)^3}\\ = 1226{\mkern 1mu} W/{m^2}\end{array}\) Assuming eff...
Post a Comment
Read more