Basic mechanical engineering interview questions answers pdf

The mechanical engineering is one of the oldest engineering branches that are being pursued by many students on a global scale.

A mechanical engineering interview can be intimidating. A good idea is to practice answering questions that you may be asked. You will need to study hard for this test, as it will cover all of the basics of mechanical engineering. If you are not prepared, you run the risk of losing valuable time on the job training process. This page gives you interview mechanical engineering questions and answers for students, frequently asked mechanical engineering questions for interviews.

These questions are not arranged in any order of difficulty. Engineers mostly ask these questions to find out the level of your knowledge and whether you can reason logically. In the case hardening process , it adds a thin layer of metal alloy to the outer surface of the metal. Thus, this process can minimize wear and tear of metals and also, it increases the strength of steels parts surface. Pattern draft is the taper placed on the pattern surfaces that are parallel to the direction in which the pattern is withdrawn from the mould i.

The back plate is mounted into the shaft and the front plate is coupled by the vanes. This type of vanes has only backside plate. This rugged pump will handle liquids containing fibrous material such as paper pulp, sugar molasses and sewage water etc. This type of impellers had no plate on either side i.

This type of rough duty pumps which handles abrasive liquids such as concrete the mixture of water, sand, pebbles and clay and slurry. When selecting a pump for any industrial or personal use, it is critical to first establish the total head needed for the operation as well as the required flow rate for the application. All of this information is essential because each pump that is produced by a manufacturer has a characteristic value of head and flow at which it operates at peak efficiency.

In a pump performance curve , the relationship between differential head and operating flow rate is graphed. Pump curves are used to determine whether or not the pumps would still be the best match for the changed needs that have been identified. The water enters from the penstock enters the casing and from their it enters into stationary guide wheels.

The water enters at outer diameter of runner and discharge at inner diameter of the runner. Hot extrusion is the process of heating appropriate metals and alloys to the right temperature and then inserting the heated stock into the cylinder of an extrusion press to produce a finished product.

Using the pressure created by a moving ram or piston, plastic metal is forced through a die that has been designed specifically for it. In hot extrusion, one of the most difficult issues to deal with is the impact of hot metal on the equipment. To keep the dies safe , a variety of techniques are used.

For each component, the die may be replaced and let to cool completely. A bonding substance holds the abrasive grains together in a grinding wheel. During the grinding process, the bonding substance does not cut. Its primary purpose is to secure the grains in different degrees of strength. Silicate, vitrified, resinoid, shellac, rubber, and metal are all common grinding wheel bonds. Rubber bond wheels are very robust and durable. Their primary applications are narrow cut-off wheels and drive wheels for centerless grinding machines.

Additionally, they are utilized when very fine finishes on bearing surfaces are needed. These bonds are composed of finely powdered clay and fluxes that are completely combined with the abrasive. When the heat produced by grinding must be kept to a minimum, silicate bonding materials are utilized. This substance easily dislodges the abrasive grains in comparison to other bonding agents. This is the most flexible bond available in a grinding wheel.

This is an organic bond that is utilized in grinding wheels to create very smooth finishes on components such as rolls, silverware, camshafts, and crank pins.

In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions. Explain the difference between the points of inflexion and contraflexure. 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.

What is the difference between proof resilience and modulus of resilience? Proof resilience is the maximum strain energy that can be stored in a material without permanent deformation. Modulus of resilience is the maximum strain energy stored in a material per unit volume. What is the difference between column and strut?

Both column and strut carry compressive load. Column is always vertical but strut as member of structure could carry axial compressive load in any direction.

Explain the difference between ferrite, austenite and graphite? Ferrite is the solid solution of carbon and other constituents in alpha-iron. It is soft, ductile and relatively weak. 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. Graphite has a hexagonal layer lattice. What do you understand by critical points in iron, iron-carbide diagram?

The temperatures at which the phase changes occur are called critical points or temperatures. PERT is based on the approach of multiple time estimates for each activity. What is stellite?

It is a non-ferrous cast alloy containing cobalt, chromium and tungsten. Which rays are produced by cobalt in industrial radiography? Gamma rays. What are killed steels and what for these are used? Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification no gas evolution occurs in these steels because they are free from oxygen. What is critical temperature in metals? It is the temperature at which the phase change occurs in metals.

What is the structure of pure iron and whether it is soft or hard? Ferrite and it is soft. Which elements increase the corrosion resistance of steel? Chromium and nickel. What causes hardness in steel? How heat treatment alters properties of steel? The shape and distribution of the carbides in the iron determines the hardness of the steel. Carbides can be dissolved in austenite is the basis of the heat treatment of steel.

If steel is heated above the A critical temperature to dissolve all the carbides, and then cooled, suitable cooling through the cooling range will produce the desired size and distribution of carbides in the ferrite, imparting different properties. Explain the formation of microstructures of pearlite, bainite and martensite in steel. If austenite containing about 0. This microstructure is called pearlite. At temperatures just belot the A1, the transformation from austenite. This phase has a tetragonal crystal structure and contains carbon in supersaturated solid solution.

How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment? A prerequisite to the hardening of steels is that martensite should be formed on cooling, but this can only be achieved if the rate of cooling is great enough to suppress the formation of pearlite or bainite and in plain carbon steels this can be achieved by quenching relatively small specimens.

What is the difference between austenite stabilisers and ferrite stabilisers? What are the effects of carbon on the properties of steel. In general, an increase in carbon content produces higher ultimate strength and hardness but lowers ductility and toughness of steel alloys. Carbon also increases air-hardening tendencies and weld hardness, especially in the presence of chromium.

In low-alloy steel for high-temperature applications, the carbon content is usually restricted to a maximum of about 0. To minimize intergranular corrosion caused by carbide precipitation, the carbon content of austenitic type alloys is limited in commercial specifications to a maximum of 0. An increase in carbon content lessens the thermal and electrical conductivities of steel and increases its hardness on quenching. What is the role of silicon as alloying element in steels?

Silicon contributes greatly to the production of sound steel because of its deoxidizing and degasifying properties. When added in amounts up to 2. Silicon in excess of 2. Resistance to oxidation and surface stability of steel are increased by the addition of silicon. These desirable effects partially compensate for the tendency of silicon to lower the creep properties of steel.

Silicon increases the electrical resistivity of steel and decreases hysteresis losses. Discuss the role of manganese in alloying steels. Manganese is an excellent deoxidizer and sulfur neutralizer, and improves the mechanical properties of steel, notably the ratio of yield strength to tensile strength at normal temperatures. It improves rolling properties, hardenability, and resistance to wear. However manganese increases the crack sensitivity of weldments, particularly with steels of higher carbon content.

Define buckling factor. It is the ratio of the equivalent length of column to the minimum radius of gyration. What do you understand by catenary cable? A cable attached to the supports and carrying its own weight. What is coaxing? It is the process of improving fatigue properties by first under-stressing and then increasing the stress in small increments.

What is isotropic material? It is a material having same elastic constants in all directions. Explain difference between modulus of resilience and modulus of rigidity?

Modulus of resilience is the maximum strain energy stored in a material per unit volume and modulus of rigidity is the ratio of shearing stress to the shearing strain within the elastic limit. What is the difference between basic hole and basic shaft? A basic hole is one whose lower deviation is zero and in case of basic shaft the upper deviation is zero. What for pyranometer is used?

It is used to measure the total hemispherical solar radiation. Describe transfer machines in brief. It is an automatic machine in which workpiece alongwith fixture is transferred from one station to other automatically and several operation on workpiece are performed at each station. What is burnt-out point? It corresponds to maximum heat flux at which transition occurs from nucleate boiling to film boiling.

What do you understand by eutectic? It is mechanical mixture of two or more phases which solidify simultaneously from the liquid alloy. Explain the difference between grey iron and white iron.

What is mottled iron? The carbon in cast iron could exist at room temperature as either iron carbide, or as graphite which is the more stable form.

The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Grey iron is extensively used in engineering because of following characteristics.

Under what condition a convergent divergent nozzle required? When pressure ratio is greater than critical pressure ratio. What is endurance limit and what is its value for steel? Endurance limit is the maximum level of fluctuating stress which can be tolerated indefinitely. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume?

Work remains unaltered and volumetric efficiency decreases. What do you understand by sulphur print? Sulphides, when attached with dilute acid, evolve hydrogen sulphide gas which stains bromide paper and therefore can be readily detected in ordinary steels and cast irons. While sulphur is not always as harmful as is sometimes supposed, a sulphur print is a ready guide to the distribution of segregated impurities in general.

What is the different between brass and bronze? Brass is an alloy of copper with zinc; and bronze is alloy of copper with tin. What is the effect of addition of zinc in copper? By addition of zinc in copper, both tensile strength and elongation increases. What for admirality brass used?

Aluminium is also added to brass to improve corrosion resistance. What is the maximum use of magnesium? Magnesium is used to alloy with aluminium and as an additive for making SG Spheroidal Graphite iron. What for zinc finds applications? Galvanizing consumes the largest proportion of zinc. Zinc is resistant to corrosion but is attacked by acids and alkalies.

Zinc alloy. Which factors influence the type of fracture in failure of a material? Seven factors influencing type of failure are :. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency.

Efficiency ratio. List two effects of manganese in plain carbon steels. Manganese increases tensile strength and hardness. It decreases weldability. Name the strongest and weakest type of atomic bonds. Metallic bond is strongest and molecular bond also known as Vander Waals bond is weakest. In which process internal energy remains constant? Isothermal process. What is temper embrittlement in alloy steels and what are its effects?

Embrittlement attack is usually intergranular in metals, i. It imparts a tendency to fail under a static load after a given period of time in those alloy steels which are susceptible to embrittlement. What are whiskers? Whiskers are very small crystals which are virtually free from imperfections and dislocations. What is Bauschinger effect? According to Bauschinger, the limit of proportionality of material does not remain constant but varies according to the direction of stress under cyclic stresses.

What is the difference between heat capacity and specific heat of a material? Explain the rule to find specific heat of aqueous solutions. For aqueous solutions of salts, the specific heat can be estimated by assuming the specific heat of the solution equal to that of the water alone.

What do you understand by latent heat? Give four examples of latent heats. For pure substances, the heat effects accompanying changes in state at constant pressure no temperature change being evident are known as latent heats.

Examples of latent heats are : heat of fusion, vaporisation, sublimation, and change in crystal form. Define the terms free energy and free enthalpy. What is their significance and importance? It is equal to the work during a constant-volume isothermal reversible nonflow process.

For reversible isothermal steady-flow processes or for reversible constant-pressure isothermal nonflow processes, change in free energy is equal to net work. What is polytropic process? Under what conditions it approaches isobaric, isothermal, and isometric process? In which reversible process no work is done? No work is done in isometric process.

Out of constant pressure and constant volume lines on TS diagram which line has higher slope? And whether slope is constant or variable? Constant volume line. Slope is variable. Whether entropy is intensive property or extensive property? Entropy is extensive property. In which process fluid expands but does no work?

Throttling process. What is the difference between scavenging and supercharging? Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.

Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion?

Why entropy change for a reversible adiabatic process is zero? Because there is no heat transfer in this process. What are two essential conditions of perfect gas? It satisfies equation of state and its specific heats are constant. Enthalpy and entropy are functions of one single parameter. Which is that? Why rate of condensation is higher on a polished surface compared to rusty surface?

Polished surface promotes drop wise condensation and does not wet the surface. How much resistance is offered to heat flow by drop wise condensation?

What is the relationship between COP of heating and cooling? When maximum discharge is obtained in nozzle? At the critical pressure ratio. Under what condition the work done in reciprocating compressor will be least? It is least when compression process approaches isothermal.

For this purpose, attempts are made to cool the air during compression. What is the difference between stalling and surging in rotary compressions? Stalling is a local phenomenon and it occurs when How breaks away from the blades.

Surging causes complete breakdown of flow and as such it affects the whole machine. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition? How cavitation causes damage? Answer: In a a closed system pipelines, or pumps , water vaporises rapidly in regions where the pressure drops below the vapour pressure. This phenomenon is called cavitation. The vapour bubbles formed in cavitation usually collapse in a violent manner, which may cause considerable damage to the system.

In milling process, how the arbor torque can be smoothend? Answer: Arbor torque can be smoothened by increasing number of teeth, using higher spiral angle of teeth, using higher cutting depth.

What are webs in a twist drill? Answer: Webs are the metal column in the drill which separates the flutes. What is bluff body? Answer: It is a body with such shape that the flow is separated much ahead of its rear end resulting in a large wake, the pressure drag being much greater than the friction drag. What is bulk modulus? Answer: It is the ratio of hydrostatic stress to volumetric strain within the elastic limits.

Define boundary layer. Answer: It is the fluid layer in the neighborhood of a solid boundary where the effects of fluid friction are predominant. What is creep flow? Answer: It is flow at very low Reynolds number where viscous forces are larger than the inertia forces. What is Torricellis theorem? Answer: According to it velocity of jet flowing out of a small opening is proportional to the square root of head of liquid above it. How does cavitation manifest itself in a centrifugal pump?

Answer: Usual symptoms of cavitation of pump are noise, vibration, a drop in head and capacity with a decrease in efficiency, accompanied by pitting and corrosion of the impeller vanes. What happens if centrifugal pump is operated at excessive speeds?

Repeated erosive action results in complete honey combing and total destruction of blade, with resultant loss in pump performance. On what parameters the head developed by a centrifugal pump depends? Answer: It depends upon the impeller diameter and its rotative speed.

Which factors determine the selection of electrolyte for electrochemical machining process? Answer: Electrolyte should be chemically stable and have high electrical conductivity.

What is the disadvantages of centrifugal pump having very low specific speed? Answer: For a. On what factors the efficiency of pump depends? Answer: Efficiency of a pump centrifugal depends on the size, speed, and proportions of the impeller and casing. On what factors the cavitation in centrifugal pumps is dependent? Answer: Cavitation in centrifugal pumps depends on the velocity of water entering tne impeller and on the relatiave velocity of the impeller blades where the water is picked up.

What are the losses in a centrifugal pump? Answer: The losses in a centrifugal pump are : Friction losses due to eddies in flow, leakage, friction loss due to rotation of impeller in chamber of water, gland and bearing power losses.

What should be done to avoid cavitation in pumps? Answer: In order to avoid cavitation, the suction lift and the operating speed must be carefully chosen.

What will happen if speed of reciprocating pump is increased? Answer: If speed of a reciprocating pump is increased beyond a limit, then atmospheric pressure would be insufficient to force water into the pump at the same speed as the piston. This would a break in the continuity of the water in suction pipe cavitation and give rise to vibration, noise, and chemical attack by any dissolved gases which may be released from the water owing to the high vacuum and the breaking of the water column.

What is the order of efficiency of cenetrifugal and reciprocating pumps? What are the basic operations performed in a slotter? Answer: The different operations done in slotter are : 1. Machining grooves 2. Machining cylindrical surface 3. Machining irregular profiles. How the positive displacement is obtained in rotary pumps? Answer: Positive displacement in rotary pumps is achieved in two ways : i A rotor carries radially adjustable vanes, the outer tips of which are constrained by a circular casing, whose centre is remote from that of the rotor.

How a slotter differs from shaper? Answer: Slotter Shaper a Ram reciprocates vertically a Ram reciprocates horizontally b It has a circular table b It has a rectangular table c Suited for machining internal surfaces c Suited for machining external surfaces d Table can take less load d Table can take much load.

Under what condition the flow and power of pump vary as square of the size? Answer: The flow and power vary as size2 when the geometric size changes as inverse of change of speed. How the incidence of cavitation detected? Answer: The incidence of cavitation is detected by the following in order of appearance.

How cavitation erosion is assessed? Answer: Cavitation erosion is assessed by depth of attack or weight of metal removed. At which temperature the cavitation erosion is negligible and why? What is an arbor? Answer: An arbor is an accurately machined shaft for holding and driving the arbor type cutter. It is tapered at one end to fit the spindle nose and has two slots to fit the nose keys for locating and driving it. For a body to float in stable equilibrium where the e.

Answer: e. What is the condition for a flow to be fully developed through a pipe? Answer: Ratio of maximum velocity to average velocity should be 2. When a fluid is moving with uniform velocity, whether the pressure of fluid will depend on its depth and orientation? Answer: No.

How much is the vertical component of force on a curved surface submerged in a static liquid? Answer: It is equal to weight of the liquid above the curved surface. On which factors depends the friction factor in a rough turbulent flow in a pipe? Answer: It depends on pipe diameter and the condition of the pipe.

What does the realisation of velocity potential in fluid flow indicate? Answer: It indicates that flow is irrotational. What is the difference between potential flow and creep flow? Answer: Potential flow assumes viscous forces to be zero but same is considered larger than inertia forces in creep flow. For which application Mach number and Froude numbers are significant? Answer: Mach no. Froude number is significant in the study of ship hulls.

What is the difference between geometric, kinematic, and dynamic similarities between model and prototype? Answer: Geometric similarity is mainly for same shape for model and prototype, kinematic similarity is concerned with stream line pattern, whereas dynamic similarity concerns the ratio of forces.