technical interview mechanical engineering objective pdf

All Important Mechanical Engineering Technical Interview Questions & Answers covering all the subjects, Important for Viva Exams & Job Interviews Mechanical Engineering Technical Interview Contents: Subjects Design of Machine Elements - Basic Design of Machine Elements: Springs Page No 3-7 - 13 Design of Machine Elements: Shafts, Keys, Bolts, Nuts, Screws, Fasteners, Bearings, Flywheel & Governor 14 - 20 Design, Strength of Materials, Kinematics of Machine, Manufacturing Process, Engineering Mechanics & Mechanical Vibrations 21 - 33 Fluid Mechanics & Fluid Machinery: Turbine, Boiler, compressor, Pumps, Bearings Etc… 34 - 47 Steam Turbine 48 - 73 All Subjects: Mechanical Engineering (Thermodynamics, Refrigeration & Air-conditioning, Heat & Mass Transfer, Automobile Engineering, I.C Engine, Power plant Engg & all….) 74 - 121 Piping Engineering 122 - 138 Basic Machine Design Design of Machine Elements: Basic Question No.01 Define Ductility Answer: It is the property of the material enabling it to be drawn into wire, with the application of tensile force It must be both strong and plastic It is usually measured in terms of percentage elongation and reduction in area, (e.g.) Ni, Al, and Cu Question No.02 Define fatigue Answer: When a material is subjected to repeated stress, it fails at stresses below the yield point stress; such type of failure of the material is called fatigue Question No.03 Define: Factor of safety Answer: The ratio between maximum stresses to working stress is known as factor of safety Factor of safety = Maximum stress /Working stress Question No.04 Define endurance limit Answer: Endurance limit is the maximum value of completely reversed stress that the standard specimen can sustain an infinite number (106) of cycles without failure Question No.05 What is impact load? Answer: If the time of load application is less than one third of the lowest natural period of vibration of the part, it is called an impact load Question No.06 What are the various phases of design process? Answer: The various phases of design process are: Recognition of need Definition of problem Synthesis Analysis and optimization Evaluation Presentation Question No.07 What is the use of Goodman & Soderberg diagrams? Answer: They are used to solve the problems of variable stresses www.objectivebooks.com Pg.3 Basic Machine Design Question No.08 What are the factors affecting endurance strength Answer: Factors affecting endurance strength are Load Surface finish Size Temperature Impact Reliability Question No.09 What are the types of variable stresses? Answer: types of variable stresses are: Completely reversed or cyclic stresses Fluctuating stresses Repeated stresses Question No.10 Differentiate between repeated stress and reversed stress Answer: Repeated stress refers to a stress varying from zero to a maximum value of same nature Reversed stress of cyclic stress varies from one value of tension to the same value of compression Question No.11 What are the types of fracture? Answer: The two types of fracture are Ductile fracture Brittle fracture Question No.12 Distinguish between brittle fracture and ductile fracture Answer: In brittle fracture, crack growth is up to a small depth of the material In ductile fracture large amount of plastic deformation is present to a higher depth Question No.13 Define stress concentration and stress concentration factor Answer: Stress concentration is the increase in local stresses at points of rapid change in cross section or discontinuities Stress concentration factor is the ratio of maximum stress at critical section to the nominal stress Question No.14 Explain size factor in endurance strength Answer: Size factor is used to consider the effect of the size on endurance strength A large size object will have more defects compared to a small one So, endurance strength is reduced If K is the size factor, then Actual endurance strength = Theoretical endurance limit x K www.objectivebooks.com Pg.4 Basic Machine Design Question No.15 Explain Griffith theory (Or) State the condition for crack growth Answer: A crack can propagate if the energy release rate of crack is greater than crack resistance Question No.16 What are the modes of fracture? Answer: The different the modes of fractures are: Mode I (Opening mode) Displacement is normal to crack surface Mode II (Sliding mode) Displacement is in the plane of the plate Mode III (Tearing mode) Out of plane shear Question No.17 What are the factors to be considered in the selection of materials for a machine element? Answer: While selecting a material for a machine element, the following factors are to be considered Required material properties Manufacturing ease Material availability Cost Question No.18 What are various theories of failure? Answer: The failure theories are: Maximum principal stress theory Maximum shear stress theory Maximum principal strain theory Question No.19 List out the factors involved in arriving at factor of safety Answer: The factors involved in arriving at factor of safety are: Material properties Nature of loads Presence of localized stresses Mode of failures Question No.20 Give some methods of reducing stress concentration Answer: Some of the methods are: Avoiding sharp corners Providing fillets Use of multiple holes instead of single hole Undercutting the shoulder parts www.objectivebooks.com Pg.5 Basic Machine Design Question No.21 Explain notch sensitivity State the relation between stress concentration factor and notch sensitivity Answer: Notch sensitivity (q) is the degree to which the theoretical effect of stress concentration is actually reached The relation is, Kf = + q (Kt-1) Question No.22 What are the factors that affect notch sensitivity? Answer: The factors effecting notch sensitivity are: Material Notch radius Size of component Type of loading Grain Structure Question No.23 What are the different types of loads that can act on machine components? Answer: different loads on machine components are: Steady load Variable load Shock load Impact load Question No.24 Define machinability Answer: It is the property of the material, which refers to a relative ease with which a material can be cut It is measured in a number of ways such as comparing the tool life for cutting different material Question No.25 What is an S-N Curve? Answer: An S- N curve has fatigue stress on Y axis and number of loading cycles in X axis It is used to find the fatigue stress value corresponding to a given number of cycles Question No.26 What is curved beam? Answer: In curved beam the neutral axis does not coincide with the centroidal axis Question No.27 Give some example for curved beam Answer: C frame, crane hook www.objectivebooks.com Pg.6 Basic Machine Design Question No.28 What is principle stress and principle plane? A plane which has no shear stress is called principle plane the corresponding stress is called principle stress Question No.29 Write the bending equation Answer: The bending moment equation is, M/I = f/y= E/R, Where, M Bending moment (M is in N-mm) I - Moment of inertia about centroidal axis (I is in mm ) f Bending Stress (f is in N/mm²) y - Distance from neutral axis (y is in mm) E - Young s modulus (E is in N/mm²) R - Radius of curvature (R is in mm) Question No.30 Write the torsion equation Answer: The torsional equation is, T/J = q/ G L Where, T Torsional moment (T is in N-mm) J - Polar moment of inertia (J is in m q Shear stress in the element (q is in N/mm²) r - Distance of element from centre of shaft (r is in mm) G- Modulus of Rigidity (G is in N/mm²) Angle of twist L Length of the shaft (L is in mm) www.objectivebooks.com Pg.7 Machine Design: Springs Design of Machine Elements: Springs Question No 01 What is a spring? Answer: A spring is an elastic member, which deflects, or distorts under the action of load and regains its original shape after the load is removed Question No 02 State any two functions of springs Answer: To measure forces in spring balance, meters and engine indicators To store energy Question No 03 What are the various types of springs? Answer: Helical springs Spiral springs Leaf springs Disc spring or Belleville springs Question No 04 What are the requirements of spring while designing? Answer: Spring must carry the service load without the stress exceeding the safe value The spring rate must be satisfactory for the given application Question No 05 Classify the helical springs Answer: Close coiled or tension helical spring Open coiled or compression helical spring Question No 06 Define Leaf springs Answer: A leaf spring consists of flat bars of varying lengths clamped together and supported at both ends, thus acting as a simply supported beam Question No 07 What is spring index (C)? Answer: The ratio of mean or pitch diameter to the diameter of wire for the spring is called the spring index www.objectivebooks.com Pg.8 Machine Design: Springs Question No 08 Define Belleville Springs Answer: They are made in the form of a cone disc to carry a high compressive force In order to improve their load carrying capacity, they may be stacked up together The major stresses are tensile and compressive Question No 09 What is pitch? Answer: The axial distance between adjacent coils in uncompressed state Question No 10 What is solid length? Answer: The length of a spring under the maximum compression is called its solid length It is the product of total number of coils and the diameter of wire Ls = nt × d Where, nt = total number of coils Question No 11 What are the end conditions of spring? Answer: Plain end Plain and ground end Squared end Squared and ground end Question No 12 What is buckling of springs? Answer: The helical compression spring behaves like a column and buckles at a comparative small load when the length of the spring is more than times the mean coil diameter Question No 13 What is surge in springs? Answer: The material is subjected to higher stresses, which may cause early fatigue failure This effect is called as spring surge Question No 14 What is a laminated leaf spring? Answer: In order to increase, the load carrying capacity, number of flat plates are placed and below the other Question No 15 What are semi elliptical leaf springs? Answer: The spring consists of number of leaves, which are held together by U-clips The long leaf fastened to the supported is called master leaf Remaining leaves are called as graduated leaves www.objectivebooks.com Pg.9 Machine Design: Springs Question No 16 What is nipping of laminated leaf spring? Answer: Pre-stressing of leaf springs is obtained by a difference of radii of curvature known as nipping Question No 17 What are the various applications of springs? Answer: The springs are used in various applications, they are Used to absorb energy or shocks (e.g shock absorbers, buffers, etc.) To apply forces as in brakes clutches, spring-loaded valves, etc To measure forces as in spring balances and engine indicators To store energy as in watches Question No 18 Define free length Answer: Free length of the spring is the length of the spring when it is free or unloaded condition It is equal to the solid length plus the maximum deflection or compression plus clash allowance Lf = solid length + Ymax + 0.15 Ymax Question No 19 Define spring index Answer: Spring index (C) is defined as the ratio of the mean diameter of the coil to the diameter of the wire C =D/d Question No 20 Define spring rate (stiffness) Answer: The spring stiffness or spring constant is defined as the load required per unit deflection of the spring K= W/y Where, W - Load y - Deflection Question No 21 Define pitch Answer: Pitch of the spring is defined as the axial distance between the adjacent coils in uncompressed state Mathematically Pitch=free length/n-1 Question No 22 What are the points to be taken into consideration while selecting the pitch of the spring? Answer: The points taken into consideration of selecting the pitch of the springs are The pitch of the coil should be such that if the spring is accidentally compressed the stress does not increase the yield point stress in torsion The spring should not be close up before the maximum service load is reached www.objectivebooks.com Pg.10 ...All Important Mechanical Engineering Technical Interview Questions & Answers covering all the subjects, Important for Viva Exams & Job Interviews Mechanical Engineering Technical Interview Contents:... Mechanics & Vibrations Question No 01 What is mechanical engineering? Answer: Mechanical engineering is the discipline that applies the principles of engineering, physics and materials science for... Subjects: Mechanical Engineering (Thermodynamics, Refrigeration & Air-conditioning, Heat & Mass Transfer, Automobile Engineering, I.C Engine, Power plant Engg & all….) 74 - 121 Piping Engineering 122