Mechanical engineering questions and answers pdf

  1. [MOST ASKED] MECHANICAL ENGINEERING Multiple Choice Questions and Answers
  2. Mechanical Engineering Questions and Answers
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  4. Mechanical Engineering (MCQ) questions and answers - Engineering

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Mechanical Engineering Questions And Answers Pdf

BASIC MECHANICAL ENGINEERING Interview Questions Answers PDF free download mcqs objective type questions lab viva online quiz test. Below are the lost of top MECHANICAL ENGINEERING Multiple Choice Questions and Answers pdf free we can provide. ME: MECHANICAL ENGINEERING 1st Feb Shift1 Wrong answer for MCQ will result in negative marks, (-1/3) for 1 mark Questions and (-2/3) for 2 marks.

Question How Does Hydraulics Work? Answer : A positive displacement pump gear, vane, or piston pump is driven by a prime mover Electrical Motor or Engine it sucks fluid from reservoir and delivers oil to system. Answer : Nitrogen is used to prevent porosity in the welding member by preventing oxygen and air from entering the molten metal during the welding process. Other gases are also used for this purpose such as Argon, Helium, Carbon Dioxide, and the gases given off when the flux burns away during SMAW stick welding. Answer : That is the engine running too lean lack of fuel. This condition will lead to overheating and failure of the engine. Answer : Both the hydraulic and engine oils are made from base oils with additives mixed in. The additives used change the characteristics of the oils so that they function differently. Generally, hydraulic oils final product including additives are expected to have very low compressibility and very predictable friction and viscosity stability under pressure.

Addition of nickel and chromium increases the tensile strength and increase in resistance to corrosion takes place. Mention two types of dislocations. Dislocation refers to a break in the continuity of the lattice. In edge dislocation, one plane of atoms gets squeezed out. In screw dislocation the lattice atoms move fom their regular ideal positions. What are the principal constituents of brass?

Principal constituents of brass are copper and zinc. What is Curie point? Curie point is the temperature at which ferromagnetic materials can no longer be magnetised by outside forces. Specific strength of materials is very high when they are in fibre size but lower when they are in bar form Why? Crystal structure has ordered, repeating arrangement of atoms.

Fibres are liable to maintain this and thus have high specific strength. What is the percentage of carbon in cast iron? Which element is added in steel to increase resistance to corrosion?

Whether individual components in composite materials retain their characteristics or not? An elastomer is a polymer when its percentage elongation rate is? Why is it that the maximum value which the residual stress can reach is the elastic limit of the material? A stress in excess of elastic limit, with no external force to oppose it, will relieve itself by plastic deformation until it reaches the value of the yield stress.

Why fatigue strength decreases as size of a part increases beyond around 10 mm? Perfection of material conditions is possible at lower sizes and as size increases, it is not possible to attain uniform structure of the material. Distinguish between creep and fatigue. Creep is low and progressive deformation of a material with time under a constant stress at high temperature applications.

Fatigue is the reduced tendency of material to offer resistance to applied stress under repeated or fluctuating loading condition. While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength.

By excessive treatment the high compressive stresses are introduced but these are balanced by high internal tensile stresses of equal value and the subsurface fatigue cracks may develop in the regions of high tensile stress and lead to early fatigue failure. List at least two factors that promote transition from ductile to brittle fracture. Manner of loading, and the rate of loading promote transition from ductile to brittle fracture. A machine member may have ductile failure under static loading but may fail in brittle fashion when the load is fluctuating.

Similarly a material may evidence ductile failure under tensile loading at ordinary testing speed but if load is applied at a high velocity then failure may be brittle.

Which theories of failure are used for a ductile materials, and b brittle materials? For ductile materials, theories of failure used are maximum shear stress theory, and maximum energy of distortion theory; while for brittle materials, theory of maximum principal stress, and maximum strain are used. What does thermal diffusivity of metals signify. Thermal diffusivity is associated with the speed of propagation of heat into solids during changes in temperature with time.

For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these? Area of the section of the heat flow path, perpendicular to the direction of heat flow.

Thermal conductivity of material. How convective heat transfer is effected and on what factors it depends? Convective heat transfer is effected between a solid and fluid by a combination of molecular conduction within the fluid in combination with energy transport resulting from the motion of fluid particles.

It depends on boundary layer configuration, fluid properties and temperature difference. Which is the common element between brass and bronze? What does following alloy designation indicate FG ? Grey cast iron with tensile strength of MPa. How is ceramic defined?

It is a solid formed by combination of metallic and non-metallic elements. What is the name of solid solution of carbon in alpha iron and delta iron? Ferrite and austenite respectively. Explain the difference between pearlite and cementile? Pearlite is eutectoid mixture of ferrite and cementile.

Cementite is chemical compound of iron and carbon. Give one example each of the following proportion of materials dimensional, physical, technological and mechanical. Roughness, enthalpy, toughness, and hardness respectively.

For which parts the Wahl factor and Lewis form factor used? For springs and gears respectively. How oxygen can be removed from steel during melting? What are fully killed steels? 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.

Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel? Execessive hydrogen results in the formation of small fissures often described as hairline cracks or flakes in the steel. Large forgings in alloy steel are particularly sensitive to this phenomenon. What is allotrope? In what forms of cubic pattern, iron exists? Some elements exist in more than one crystalline form.

Iron exists in two forms of cubic pattern, namely body centered cubic bcc and face-centered cubic fee.

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

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Alloys are produced by melting or sintering two ore 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, transformations and properties of metals and alloys.

A combination of phases in a state of equilibrium is called a system. A phase is a homogeneous 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. The structural components of an alloy are its individual portions, each having a single structure with its characteristic features. What is the difference between isotropic material and homogeneous material? 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. Explain the terms solid solution, eutectic, eutectoid and peritectic. Solid Solution. When a homogeneous mixture of two or more atomic forms exists in solid state, it is known as solid solution.

Mechanical Engineering Questions and Answers

A mixture of two or more phases which solidify simultaneously from the liquid alloy is called an eutectic. Alloys in which the components solidify simultaneously at a constant temperature the lowest for the given system, are called eutectic alloys. Eutectoid alloys are the alloys for which two solid phases which are completely soluble become completely insoluble on cooling before a certain temperature called eutectoid temperature.

A peritectic transformation involves a reaction between a solid and liquid that form a different and new solid phase. This three phase transformation occurs at a point called peritectic point. 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 the percentage of chromium in 18 : 4 : 1 IISS?

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. Car tyres are usually made of? Styrene-butadine rubber. 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 are the major effects of alloying elements?

To alter the transformation temperatures and times To modify the room temperature and elevated temperature strengths of given structures by a stiffening the crystals and b introducing complex precipitates which tend to harden the steel.

To modify the type of oxide film formed on the surface of the steel and thereby affect its corrosion resistance. What is the difference between austenite stabilisers and ferrite stabilisers?

Austenite stabilisers have the effect of extending the temperature range overwhich austenite is formed. Such elements are carbon, manganese, nickel, copper and cobalt. Ferrite stabilisers have the effect of extending the temperature range over which alpha and delta ferrite are formed, which consequently reduces temperature range over which austenite is formed. Such elements are silicon, chromium, molybdenum, tungsten, titanium and niobium.

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 difference between conjugate beam and continuous beam? A conjugate beam is an imaginary beam of same size as original beam and carrying a distributed load in accordance with the bending moment diagram. A continuous beam is one which is resting on more than two supports.

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?

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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. Low melting point and high fluidity making it suitable for castings of intricate shape. Relatively good erosion and corrosion resistance.

High damping capacity, with respect to vibration. Relatively good mechanical properties under compressive loading. 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?

Mechanical Engineering (MCQ) questions and answers - Engineering

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?

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? The heat capacity of a material is the amount of heat transformed to raise unit mass of a material 1 degree in temperature.

The specific heat of a material is the ratio of the amount of heat transferred to raise unit mass of a material 1 degree in temperature to that required to raise unit mass of water 1 degree of temperature at some specified temperature. For most engineering purposes, heat capacities may be assumed numerically equal to;specific heats. 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.

Which parameter remains constant in isochoric process? 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. Whether superheated steam can be treated like ideal gas? 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. Generally, hydraulic oils final product including additives are expected to have very low compressibility and very predictable friction and viscosity stability under pressure. Generally engine oils Engine Lubrication Oils anyway are intended to have high resistance to heat degradation including chemical and viscosity due to heat resistance to burning and resistance to absorption of fuels and chemical compounds produced during combustion.

Both classes of oils are likely to have additives intended to provide detergency and to reduce foaming.

Base oils are most commonly petroleum oil bases due to cost, but other bases oil can be used including mineral oils especially for hydraulic oils and plant oils especially for engine oils and oils from animal sources.

Answer : Hydraulic fluid has to pass a different set of standards than motor oil. Motor oil has tackifiers, lower sulfur content, and other ingredients that could prove harmful to the seals and other components in a hydraulic system. If it is an emergency only should you do it.

Answer : Angular momentum is an expression of an objects mass and rotational speed. Momentum is the velocity of an object times it is mass, or how fast something is moving how much it weigh. Therefore, angular momentum is the objects mass times the angular velocity where angular velocity is how fast something is rotating expressed in terms like revolutions per minute or radians per second or degrees per second. Answer : The total process of a the refining business starts at the oil field or gas field and runs all the way to the sending of processed hydrocarbon to a final user.

Upstream applies to the operation of exploration, drilling, hydrocarbon production, and transmission via truck, rail or ship or pipeline to the refinery intake valve. Downstream includes all work done at the refinery, distillation, cracking, reforming, blending storage, mixing and shipping.

The case of heavy oil processing oil sands etc. Most are regarded as upstream operations even though downstream type operations are part of the processes.

The production of chemical side products at gas plants e. Additional hydrocarbon production operations such as saddle plants, which remove a component from pipeline gas, are generally lumped with upstream. Answer : Rolling offsets are used in the piping and sheet metal ductwork trades, a rolling offset changes the elevation and locaton of the piping or duct usually by using two fittings to offset around obstacles.

Rolling offsets are used mostly when you are limited to the size of the fittings in order to change your elevation and location. Answer : Thickest paper has the greatest mass and therefore potential energy. Potential energy equals kinetic energy speed. Speed equals lift. Lift equals a greater flight distance. Thicker planes fly farther. Answer : Two pans of equal balances are placed at the end of the beam, one at each end.

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