ME6503 Design of Machine Elements question bank

ANNA UNIVERSITY,CHENNAI

REGULATION 2013

DEPARTMENT OF MECHANICAL ENGINEERING

ME 6503 DESIGN OF MACHINE ELEMENTS

UNIT 3 TEMPORARY AND PERMANENT JOINTS

PART-A

1.      What are the different stresses setups in a bolt due to initial tightening

2.      Why reinforcement is normally required in welded joints?

3.      How is a bolt designated?

4.      Why are welded joints preferred over riveted joints?

5.      Differentiate with a neat sketch the fillet welds subjected to parallel loading and transverse loading?

6.      What are different types of cotter joints?

7.      State the two types of eccentric welded connections.

8.      What is a gib? Why is it provided in a cotter joint?

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PART-B

9.      The cylinder head of a steam engine is subjected to a steam pressure of 0.7 N/mm². It is held in position by means of 12 bolts. A soft copper gasket is used to make the joint leak-proof. The effective diameter of cylinder is 300 mm. Find the size of the bolts so that the stress in the bolts is not exceed 100MPa.

10.  A plate of 200mm width is welded to a vertical plate by fillet welding on three sides to form a cantilever with an overlap of 150mm and overhang of 400mm. A vertical downward load of 35kN is applied at free end for a weld stress of 75 N/mm². Determine the size of the weld.

11.  A steam engine cylinder has an effective diameter of 350mm and the maximum steam pressure acting on the cylinder cover is 1.25 N/mm². Calculate the number and size of studs required to fix the cylinder cover. Assume the permissible stress in the studs to be 70 N/mm².

12.  A bracket is welded to the vertical plate by mean of two fillet welds as shown in figure. Determine the size of the welds, if the permissible shear stress is limited to 70 N/mm².

13.  A cast iron cylinder head is fastened to a cylinder of 500 mm bore with 8stud bolts. The maximum pressure inside the cylinder is 2MPa. The stiffness of part is thrice the stiffness of the bolt. What should be the initial tightening load so that the point is leak proof at maximum pressure? Also choose a suitable bolt for the above application.

14.  (i) What is an eccentric loaded welded joint? Dicuss the procedure for designing such a joint.

(ii) A 50mm diameter solid shaft is welded to a flat plate as shown in figure. If the size of the weld is 15mm, find the maximum normal and shear stress in the weld.

15.  For supporting the travelling crane in a workshop the brackets are fixed on steel columns as shown in figure. The maximum load that comes on the bracket is 12 kN acting vertically at a distance of 400 mm from the face of the column. The vertical face of the bracket is secure dto a column by four bolts in two rows (two in each row) at a distance of 50 mm from the lower edge of the bracket. Determine the size of the bolt material is 84 Mpa. Also find the cross section of the arm of the bracket which is rectangular.

16.  Find the maximum shear stress induced in the weld of 6 mm size when a channel as shown in figure , is welded to a plate and loaded with 20 kN force at a distance of 200 mm.

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ME6503 Design of Machine Elements 2 marks

ANNA UNIVERSITY,CHENNAI

REGULATION 2013

DEPARTMENT OF MECHANICAL ENGINEERING

SUBJECT CODE:ME 6503

SUBJECT NAME:DESIGN OF MACHINE ELEMENTS

UNIT II SHAFTS AND COUPLINGS 

Design of solid and hollow shafts based on strength, rigidity and critical speed – Keys, key ways and splines - Rigid and flexible couplings.

PART-A ( Two Marks)

1.What is a shaft? List out the types of shafts.

A shaft is a rotating machine element,which transmits power from one point to another point.

Types of shafts:

i.Line shaft 

ii.Spindle 

iii. Stub shaft 

iv. Counter shaft

2.What is key?

Key is a device which is used for connecting tow machine parts for preventing relative motion of rotation with respect to each other.

Types of Keys:

 i. Saddle key 

ii.Tangent key 

iii.Sunk key 

iv.Round key and 

taper pins.

3.Define the term critical speed?

The speed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite, is known as critical speed.

4.What are the types of Flexible coupling?

i.Universal coupling,

ii.Oldham’s coupling,

iii.Pushed pin type coupling.

5.What are the types of Rigid coupling?

i.Sleeve coupling, 

ii.Flange coupling, 

iii.Clamp coupling.

6.Under what circumstances flexible couplings are used?

They are used to join the abutting ends of shafts when they are not in exact alignment. They are used to permit an axial misalignment of the shafts without under absorption of the power, which the shafts are transmitting.  

7.How are sunk key designed?List the various failures occurred in sunk keys.

Sunk keys are designed to fit in a sunk key way. Whose bed is parallel to the axis of the shaft.

Various failures:

1.Shear failure 2.Crushing failure 

8.What is the function of a coupling between two shafts?

 Couplings are used to connect sections of long transmission shafts and to connect the shaft of a driving machine to the shaft of a driven machine.

9.What are the purposes in machinery for which couplings are used?

i.To provide the connection of shafts of units those are manufactured separately such as motor and generator and to provide for disconnection for repairs or alterations.

ii.To provide misalignment of the shafts or to introduce mechanical flexibility.

iii.To reduce the transmission of shock from one shaft to another. 

iv.To introduce protection against over load.

10.What are the different measures followed to control the lateral deflection?

i. Reducing the span length 

ii. Increasing the number of supports 

iii. Selecting the cross-section in which the area moment of inertia as in case of hollow shaft.

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ME6503 Design of Machine Elements 2 marks with answers

ANNA UNIVERSITY,CHENNAI

REGULATION 2013

DEPARTMENT OF MECHANICAL ENGINEERING

SUBJECT CODE:ME 6503

SUBJECT NAME:DESIGN OF MACHINE ELEMENTS

UNIT I    STEADY STRESSES AND VARIABLE STRESSES IN MACHINE MEMBERS 

Introduction to the design process - factors influencing machine design, selection of materials based on mechanical properties - Preferred numbers, fits and tolerances – Direct, Bending and torsional stress equations – Impact and shock loading – calculation of principle stresses for various load combinations, eccentric loading – curved beams – crane hook and ‘C’ frame- Factor of safety - theories of failure – Design based on strength and stiffness – stress concentration – Design for variable loading.

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PART-A ( Two Marks)

    1.What are the various phases of design process?

    i.Recognition of need. 

    ii.Definition of problem

    iii.Synthesis 

    iv.Analysis and optimization 

    v.Evaluation

    vi.Presentation

   2.Define stress concentration and stress concentration factor.

 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.

3..What are the factors to be considered in the selection of materials for a machine element?

       i.Required material properties

       ii.Manufacturing ease 

       iii.Material availability 

       iv.Cost

4. 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.

   5.Write the torsion equation.

. 

                T/J = CØ/L = Fs/R 

          T – Torque  J -   Polar moment of intertia  C-   Rigidity modulus  Ø – Angle of twist  

          L –   Length of the shaft  Fs – Shear stress  R -   Radius of the shaft  

   6.Write the bending equation.

      M/I = E/R = Fs/Y.        

         M –  Bending moment         

         I  -    Moment of intertia 

        E -   Youngs modulus 

        R -   Radius of the shaft 

        Fs – Shear stress 

        Y  -  Distance from neutral axis  

  7.Define: Factor of safety

      The ratio between maximum stresses to working stress is known as factor of safety.

Factor of safety =    Maximum stress / Working stress

   8.What are the types of variable stresses?

        a.Completely reversed or cyclic stresses 

        b.Fluctuating stresses 

        c.Repeated stresses

   9.Distinguish between brittle fracture and ductile fracture.

    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.

10.Explain size factor in endurance strength.

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, 

Actual endurance strength = Theoretical endurance limit x K 

11.What are various theories of failure?

      i.Maximum principal stress theory. 

      ii.Maximum shear stress theory. 

      iii.Maximum principal strain theory.

    12..List out the factors involved in arriving at factor of         safety. 

      i.material properties 

     ii.nature of loads 

     iii.presence of localized stresses

     iv.mode of failures 

   13.Explain notch sensitivity and State the relation between     stress concentration factor, fatigue stress concentration          factor and notch sensitivity.

Notch sensitivity (q) is the degree to which the theoretical effect of stress concentration is actually reached.

The relation is, Kf  = 1 + q (Kt-1)

14.What are the factors that effect notch sensitivity?

 i.Material 

 ii.Notch radius 

 iii.Size of component 

 iv.Type of loading 

 v.Grain Structure            

15.Define Ductility

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. (Examples) Ni, Al, Cu

  

 16.Define fatigue 

         

   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.

  17.What are preferred Numbers.

    Preferred numbers are the standard guidelines for choosing exact     product dimensions within a given set of constraints and It is      denoted as R. It helps to minimize the number of that need to be       manufactured an element.

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