Dome 6th Sem. Sp_09

BIRLA INSTITUTE OF TECHNOLOGY DEPARTMENT OF MECHANICAL ENGINEERING,MESRA, RANCHI B.E. VI SEMESTER( Mech. Engg.) DESIGN OF MACHINE ELEMENTS

TS-1 ( Design Introduction, Fits and Tolerances) 1.

Define Design, Mechanical Design, Machine Design and Design of Machine

Components. 2.

What are the steps involved in design of machine element? Differentiate between

analysis and synthesis. 3.

What are the various factors to be considered while selecting a manufacturing process?

Discuss briefly. 4.

What do you mean by standardization? What are the advantages of standardization of

machine components? 5.

What are preferred numbers? What are their advantages to a machines designer?

Discuss the basic series for preferred numbers. 6.

What is the importance of tolerance and fits in designing machine components?

Discuss the systems of fit. Why hole basis system is preferred over the shaft basis system? Discuss the various types of fits. 7.

What are three basic types of standards used in design office?

8.

What are ergonomic considerations in design of control?

9.

Write short notes on aesthetic considerations in design.

10.

What is derived series? What is R20/4(1, . . . . . .1000) designation of derived series?

11.

Find out the numbers of R20/3(200,…………..) derived series.

12.

It is required to standardize 11 speeds from 72 to 720 rpm for a machine component.

Specify the speeds. 13.

What is FG200 designation of cast iron?

14.

What is 55C4 designation of steel?

15.

How will you designate plain carbon steel with min tensile strength of 200N/mm2.

16.

What is X20Cr18Ni2 designation of steel?

17.

How will you designate alloy steel with following compositions

(1)

Carbon =0.12-0.20%, Nickel=0.8-1.2%, Chromium=0.6-1.0%.

(2)

Carbon =0.35-0.45%, Chromium=0.9-1.1% .

BIRLA INSTITUTE OF TECHNOLOGY DEPARTMENT OF MECHANICAL ENGINEERING,MESRA, RANCHI B.E. VI SEMESTER( Mech. Engg.) DESIGN OF MACHINE ELEMENTS

TS-2( Design against static and fluctuating loads) 18.

What is static load?

19.

Distinguish between stress-strain diagram for ductile material and brittle material.

20.

Differentiate between elastic and yield limit.

21.

What are three basic modes of failure of mechanical components? Give some exaples

of parts which fails by these modes. 22.

What is factor of safety? What are the factors to be considered for deciding the

magnitude of factor of safety? 23.

What is allowable stress ? How it is calculated for ductile and brittle materials?

24.

Mention the different theories of failures and also suggest which is suited for ductile and

brittle materials. 25.

State and proof distortion energy theory of failure.

26.

The shaft of an overhang crank subjected to a force P of 2 kN is shown in fig. If the

shaft is made of 45C8 determine the diameter of the shaft assuming factor of safety equal to 2.

27.

The dimensions of an overhang crank are given in fig. The force P acting at the

crankpin is 2 kN. The crank is made of 30C8. determine the diameter at section X-X assuming factor of safety equal to 2.

28.

A hollow circular column carries a projectin bracket, which supports a load of 25kN as

shown in fig. The internal diameter of the column is 0.8 times that of external. The column is made of FeE200 and the factor of safety is 4. Determine the dimensions of the cross-section of the column.

29.

An offset link made of FG300 subjected to a force of 25kN is shown in fig. Determine

the dimensions of the cross-section of the link.

30.

What is stress concentration? How will you account for stress concentration in

design of the machine part? 31.

What is stress concentration factor? What are the causes of stress

concentration? 32.

What are the methods of reducing stress concentration?

33.

What is fluctuating stress? Draw stress-time curve for fluctuating stress.

34.

What is fatigue failure?

35.

What is endurance limit?

36.

Explain S-N curve.

37.

Fig shows a machine component made of 45C8. Determine the plate thickness

for infinite life if factor of safety is 2 and notch sensitivity factor is 0.8. Expected reliability is 90%.

38.

A rotating shaft made of 45C8 is subjected to a completely reversed bending

stress. The corrected endurance limit of the bar is 315 N/mm2. Calculate the fatigue strength of the bar for a life of 100000 cycles.

39.

A forged steel bar, 50 mm in diameter is subjected to reversed bending stress of

250N/mm2. Assume the material and calculate the life of the bar for 90% reliability. 40.

A rotating shaft subjected to a non rotating force of 5kN and simply supported as

shown in fig. What is the life of the shaft if shaft is made of 30C8 and expected reliability is 90%, fillet radius is 3mm.

41.

The work cycle of a mechanical component ( 50C4) subjected to completely

reversed bending stresses consists of the following three elements. i.

+/- 350 N/mm2 for 85% of time.

ii.

+/- 400 N/mm2 for 12% of time

iii.

+/- 500 N/mm2 for 3% of time If the corrected endurance limit of the component is 280 N/mm2, determine the life of the component.

42.

A cantilever beam made of cold drawn steel 50C4 is shown in fig. Determine the

diameter of the beam at fillet cross-section if expected reliability is 90% and the factor of safety is 2. Assume notch sensitivity factor at the fillet as 0.9.

43.

A machine component is subjected to two-dimensional stresses. The tensile

stress in X direction varies from 50 to 110 N/mm2 while the stress in Y direction varies from 10 to 80 N/mm2. The corrected endurance limit of the component is 270 N/mm2 and ultimate tensile strength of the material is 660 N/mm2. Determine the factor of safety used by the designer. 44.

A transmission shaft carries a pulley midway between two bearings. The

bending moment at the pulley varies from 200 to 600 N-m, as the tensional moment of the shaft varies from 7 to 20 kg-m. The frequency of variation of bending and tensional moments is equal to the shaft speed. The corrected endurance limit of the component is 270 N/mm2 and ultimate tensile strength of the material is 660 N/mm2. Determine the diameter of the shaft using factor of safety 2. The shaft is made of FeE 400.

BIRLA INSTITUTE OF TECHNOLOGY DEPARTMENT OF MECHANICAL ENGINEERING,MESRA, RANCHI B.E. VI SEMESTER( Mech. Engg.) DESIGN OF MACHINE ELEMENTS

TS-3 ( Cotter, Knuckle and Threaded Joints) 45.

It is required to design a cotter joint to connect two steel rods of equal diameter. Each

rod is subjected to an axial tensile force of 50kN. Design the joint and specify its main dimensions. 46.

It is required to design a knuckle joint to connect two steel rods of equal diameter. Each

rod is subjected to an axial tensile force of 50kN. Design the joint and specify its main dimensions. 47.

What is threaded joint? What are the advantages and disadvantages of threaded joints?

48.

The structural connection shown in fig is subjected to an eccentric load P of 10kN with

an eccentricity of 500 mm from the C. G. of the bolts. The centre-distance between bolts 1 and 2 is 200 mm, and between 1 and 3 is 150 mm. All the bolts are identical. The bolts are made of 30C8 and the FS is 2.5. Determine the size of the bolts. 49.

A steel plate subjected to a force of 5 kN and fixed to a channel by means of three

identical bolts as shown in fig. All the bolts are identical. The bolts are made of 45C8 and the FS is 2.5. Determine the size of the bolts. 50.

Following data are given for the bracket illustrated in fig. P=25 kN e=100mm

mm

l2 = 25mm.

l1=150

The bolts are made of 45C8 and FS is 2.5. Using maximum shear stress theory, specify the size of the bolts. 51.

7. Following data are given for the bracket illustrated in fig. P=50 kN l1=300 mm

l=250mm

l2 = 200mm. l3 = 100mm

Neglecting shear stress, determine the size of the bolts, if the maximum permissible tensile stress in any bolt is limited to 100 N/mm2.