Mechanical Engineering Interview Questions



1. Prototype manufacturing methods:Stereo lithography(SLY)Rapid Prototyping3D PrintingDirect Metal Laser Sintering(DMS)Fused deposition modelling (FDM)Polyjet technology2. Work hardening, also known as?strain hardening or cold working, is the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material.This implies that the metal is becoming stronger as the strain increases. Hence, it is called name "Strain Hardening".3. Pure bending?is a condition of stress where a?bending moment?is applied to a beam without the simultaneous presence of?axial,?shear, or?torsional forces. This is an ideal case.Assumptions made in the theory of Pure BendingThe material of the beam is homogeneous?and isotropic.The value of Young's?Modulus of Elasticity?is same in tension and compression.The transverse sections which were plane before bending, remain plane after bending also.The beam is initially straight and all longitudinal filaments bend into circular arcs with a common centre of curvature.The radius of curvature is large as compared to the dimensions of the cross-section.Each layer of the beam is free to expand or contract, independently of the layer, above or below it.4. Poisson Ratio Range (-1 to ?)1/m = -1 are Auxetic materials, when stretched, they become thicker perpendicular to the applied force. This occurs due to their hinge-like structures, which flex when stretched.?E.g.: foam structures, 5. Why stress is taken in Y axis in STRESS STRAIN CURVE?In tensile test the curve will be drawn b/w load vs change in length. As stress is load per unit area, we put area as constant and this makes to take stress in y axis.We cannot find stress directly, so by using the independent variable strain we can calculate stress. Dependent variable in y axis and Independent variable in X axis.6. Why we use this type of test specimen in tensile test. If there will not be fillet at the corners the crack may form at the I_ type corners7. Dependent Variables: These will be dependent on the other variables. Eg. Stress, Bulk modulus.8. Independent variables: These are not dependent on other variables. Eg: Strain.9. Difference between Displacement: Distance from which one element can be moved from its original position. This could be the result of movement of entire object.Deflection: Distance that an object bends, twists from its original position. This may have transverse load.Deformation: The actual distortion that occurs to a structural member. This will have elastic and plastic deformation.10. Titanium: low density and high strength. Corrosion resistant. This can be used in Jewel rings, added in gold for finning it (carets).11. How Poisson ratio is identified.Negative to the ratio of lateral strain to the linear strain.This is identified by the bulk modulus and modulus of rigidity.Strength: Ability of material to withstand the load.Elasticity: Ability of material to regain to its original position after removing the load.Ductility: Ability of material to deform to a greater extent before sign of crack when it is subjected to tensile load. Deform plastically to a greater extent prior to fracture. Temp inc ---- ductility decBrittleness: Ability of material to withstand much load without plastic deformation.Stiffness / Rigidity: Ability of material to resist deformation under any external load.Modulus of elasticity is major of stiffness, Modulus of rigidity (F/Unit deflection)Hardness: Resistance of material to penetrate or permanent deformation.Strain Hardening: Strengthening of metal by plastic deformation. This strengthening occurs because of dislocation movements and generation with the crystal structure of material. Also called as cold working, work hardening.Malleability: Ability of material to deform to a greater extent before sign of crack when it is subjected to compressive load.Temp inc ---- ductility inc. Eg: Gold, copper, silverResilience: Ability to absorb energy when deformed elastically and release its load elastically and release for spring material.Toughness: Ability of material to absorb energy before fracture.Temp inc ---- toughness decFracture Toughness: Ability of material that can absorb energy at failure against fracture.Fracture: Separation of a body into two or more pieces in response to an imposed stress that is static.Creep: Material subjected to const load (tensile load) at elevated temp will undergo a time-dependent increase in length and this is called creep.Fatigue: The failure of material due to the dynamic loading.Stress vs no.of cyclic loads behaviour of material under changing mechanical load with respect to time.Impact Strength: Ability of the material to resist shock energy before it fractures.12. Why we use I-Section in Railway Tracks, Connecting rods, Electric poles etc…13. How you differentiate Ductile and Brittle material by observing workpiece rod(a) W/p having cup and cone after deformation then it is Ductile Material(b) W/p having no cup and cone it is Brittle Material14. True and Engineering Stress-strain curvesInstantaneous area and Instantaneous length are considered ------- Engg Stress-strain curveInstantaneous area and Instantaneous length are not considered----- True Stress-strain curve15. Poisson ratio of cork is Zero. So it is used in closing of wine and other bottles rather than rubber.16. What are the advantages and dis-advantages of cast iron?Advantages:Mass availability, tooling and reduces costComplex shapes can be obtainedVibrations can be resisted by CIHigh compressive StrengthResistance to wear in the no lubrication conditionDis-advantages:Machinability is low i.e. poorLess tensile in nature (brittle)Tensile strength decreases when thickness of cross-section decreases17. Rigid body, Elastic body, Free body diagram18. Factor of safety (F.S) is ratio of ultimate to allowable. No units19. Scalar -------- only Magnitude, E.g., Time, volume, area, length, mass, etc…20. Vector ------- Magnitude and Direction, E.g., Momentum, acceleration, velocity etc…21. What is stress and strain?22. Can we see stress? If not why? ................
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