Q11. Which is the common element between brass and bronze ?

Ans. Copper.


Q12. How is ceramic defined ?

Ans. It is a solid formed by combination of metallic and non-metallic elements.


Q13. What is the name of solid solution of carbon in alpha iron and delta iron ?

Ans. Ferrite and austenite respectively.


Q14. Give one example each of the following proportion of materials-dimensional, physical, technological and mechanical.

Ans. Roughness, enthalpy, toughness, and hardness respectively.

Q15.  How oxygen can be removed from steel during melting? What are fully killed steel?

Ans. Oxygen can be removed by adding elements such as manganese, silicon or aluminium which, because of their high affinity for oxygen, react with it to form non-metallic oxides which rise into the slag. Steels which have had most of their dissolved oxygen removed are called “fully killed steels”.


Q16. What is the difference between alpha iron, delta iron and gamma iron?

Ans. The bee form of iron exists between room temperature and 910°C, and between 1400°C and the melting point at 1539°C. The lower temperature form is known as “alpha” -iron and the higher temperature form as “delta”-iron. The face-centered cubic form existing between 910°C and 1400°C is referred to as “gama-iron”.


Q17. Metals, in general are of low strength and do not possess required physio-chemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.

Ans. Alloys are produced by melting or sintering two or more metals, or metals and a non-metal, together. Alloys possess typical properties inherent in the metallic state. The chemical elements that make up an alloy are called its components. An alloy can consist of two or more components.

The phase and structures of alloys describe the constitution, transformation and properties of metals and alloys. Acombination of phases in a state of equilibrium is called a system. A phase is a homogenous portion of a system having the same composition and the same state of aggregation throughout its volume, and separated from the other portions of the system by interfaces. For instance, a homogeneous pure metal or alloy is a single-phase system. A state in which a liquid alloy (or metal) coexists with its crystals is a two-phase system. Structure refers to the shape, size or the mutual arrangement of the corresponding phases in metals or alloys.


Q18. Explain the difference between the points of inflexion and contraflexure.

Ans. At points of inflexion in a loaded beam the bending moment is zero and at points of contraflexure in loaded beam the bending moment changes sign from increasing to decreasing.


Q19. What do you understand by critical points in iron, iron-carbide diagram ?

Ans. The temperatures at which the phase changes occur are called critical points (or temperatures).

Austenite is the solid solution of carbon and other constituents in gamma-iron. It exists in ordinary steels at elevated temperatures, but it is also found at ordinary temperatures in some stainless steels.


Q20. Which rays are produced by cobalt-60 in industrial radiography ?

Ans. Gamma rays.



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Mechanical Engg. Interview Questions – Section-6


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