**Design of Machine Elements N scheme important questions**

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**Subject : Design of Machine Elements Scheme : N**

**Design of Machine Elements N scheme important questions **

**Unit – 1, ENGINEERING MATERIALS, JOINTS AND FASTENERS**

**5 Marks **

1. Name atleast five mechanical properties of materials .

2. What are factors to be considered for the selection of materials for the design of machine

elements(

3. Define factor of safety for ductile and brittle materials

4. Explain preferred number with an examples(

5. What is free cutting steel? How it is designated?

6. How engineering materials are classified

7. Write composition designated as given below XT 15 Cr 16 Ni 2

Part – B

1. Define factor of safety for ductile and brittle materials **(7 marks)**

- A hydraulic press exerts a total load of 3.5MN. The load is carried by two steel rods supporting the upper heads of the press. If the safe stress is 85MPA and E=210kN/m
^{2}. Find (i) diameter of the rods (2) Extension in each rod in a length of 2.5m.**(10 marks)** - Design a sleeve and cotter joint to transmit a tensile load of 60kN, assuming that all the parts are made of the same materials. The permissible stresses are 60 N/mm
^{2}in tension, 125 N/mm^{2}in bearing and 70N/mm^{2}in shear**(15 marks)** - What are the factors to be considered for the selection of materials for the design of machine elements
**(7 marks)** - Design a knuckle joint to take a load of 140kN for the following permissible stresses 75MPa in tension, 140 MPa in compression and 65MPa in shear.
**(15 marks)** - Explain preffered number with an example.
**(7 marks)** - The head of a steam engine cylinder 500mm diameter is subjected to a pressure of 1N/mm
^{2}. The head is held in position by 16 numbers of M30 bolts. A copper gasket is used to make the joint steam tight. Determine the stress induced in the bolt. Assume K = 0.5**(14 marks)** - Define creep strain and creep curve
**(5 marks)** - Define stress concentration. Write its causes and remedies.
**( 10 marks)** - Design a sleeve and cotter joint to withstand a tensile load of 60kN. All parts of the joint are made of the same material and the permissible stresses are given below.

f_{t} = 60 N/mm^{2}, f_{c} = 125 N/mm^{2}, f_{s }= 70 N/mm^{2} **(15 marks)**

Design of Machine Elements N scheme important questions

- Define maximum shear stress theory and maximum distortion energy theory.
**(5 marks)** - In a steam engine cylinder 0f 300mm diameter the maximum pressure across the piston is 0.65 N/mm
^{2}. Determine the diameter of the piston rod, if the maximum tensile or compressive stress on the piston is limited to 40 N/mm^{2}**(10 marks)**

- A mild Steel rod supports a tensile load of 50 kN. If the stress in the rod is limited to 100 N/mm2, Determine the size of the rod when the cross section is (i) circular (ii) square (iii) rectangle with width = 3 x thickness (10 marks)
- A pipe is used as a short compression member with the outside and inside diameters in the proportion of 4 to 3. The stress in the material is to be limited to 60MN/m2. When the applied load is 35 kN. Determine the diameters of the pipe. (15 Marks)
- A gudgeon pin circular section is used to connect the piston and the connecting rod of an IC Engine. If the maximum pressure on the piston is 1.5 N/mm2 and the diameter of the piston is 80 mm. Determine the diameter of the pin against the shear failure. Permissible shear stress for the pin material is 30N/mm2 (10 Marks)
- The piston of a reciprocating compressor has a diameter of 60mm. The maximum pressure on the piston face is 1.25Mpa. The pin passing through the small end of the connecting rod can be safely loaded in shear upto 10Mpa. Calculate the minimum diameter of the gudgeon pin. (10 Marks)
- A single acting internal combustion engine has a bore of 200mm and the maximum explosion pressure of 3.8 Mpa. Assuming the bearing length of the gudgeon pin as 0.45 times the bore. Determine the diameter of the gudgeon pin for a permissible bearing pressure intensity of 20MPa (10 Marks)
- In an I.C Engine, the diameter of the piston is 300 mm and the pressure inside the cylinder is 0.8 N/mm2. Find the diameter of the rod if the tensile or compressive stress for the rod is 60 N/mm
^{2}. (7 Marks) - Two circular rods of 50 mm diameter are connected at a knuckle joint by a pin of 40 mm diameter. If a pull of 120 KN acts at each end, find the tensile stress in the rod and shear stress in the pin. (10 Marks)
**A knuckle joint is subjected to a pull of 80 kN. If the maximum permissible tensile stress in the rods is 100 N/mm**^{2}and the permissible shear stress in the pin is 80N/mm^{2}. Calculate the diameter of the rods and the pin. (14 marks)- Calculate the smallest size of a hole that can be punched in a steel of 15mm thickness. Ultimate shear stress 330 N/mm
^{2}and crushing stress 1200 N/mm^{2} - Two plates of 16 mm thick are joined by a double riveted lap joint. The rivets are 25 mm in diameter. Find the crushing stress induced between the plate and the rivet if the maximum tensile load on the Joint is 48KN
- A double riveted lap joint is used to connect two plates each of 15 mm thickness and carries a tensile load of 40KN. Find the suitable diameter of rivet, if the crushing stress on rivet is 162 N/mm
^{2}

**Unit – 2 **

**5 Marks**

1.What are the types of shaft?

2.What are the advantages and disadvantages of keys?

3. What are keys? How are they classified?

4. What are the requirements of couplings?

5. Name three types of couplings used in engineering

**Part – B**

1. Design the give the complete specification of a protected type flange coupling to transmit a power of 15KW at 240Rpm.The Permissible shear stress for the shaft, bolt and key materials is 35N/mm2, The permissible crushing stress for the bolt and key materials is 60N/mm2 and the permissible shear stress for the flange materials is 15N/mm2.Assume that the maximum torque exceeds the mean torque by 20%.

2. Design a protective type flange coupling to connect two shafts to transmit 7.5KW at 720 Rpm. The Permissible shear stress for shafts, bolt and key materials is 33N/mm2, Permissible crushing strength for the bolt and key materials of 60N/mm2 and permissible shear stress for CI is 15N/mm2.

3. Design a protective type of cast iron flange coupling for a steel shaft transmitting 15KW at 200Rpm. The allowable shear stress is 40N/mm2. The working stress in the bolts should not exceed 30N/mm2. Assume that the same material is used for shaft and key. The crushing stress is twice the value of shear stress. The maximum torque is 25% greater than full load torque. The shear stress for cast iron is 14N/mm2. Check your design for Hub, Key, Flange and Bolts.

4. A rigid flange coupling is to be designed to transmit 20KW at 1000rpm. Allowable shear stress for shaft, key and bolts is 40N/mm2. Allowable crushing stress for key and bolts is 80N/mm2, and Allowable shear stress for flange material is 15N/mm2. Design the coupling

17. The shaft and flange of marine coupling is to be transmitting 3MW at 100 rpm. The shear stress for shaft and bolts is 60N/mm2 The number of bolt is 8. The P. C. D of the bolt is 1.6d. Design the coupling.

UNIT-3

1. The following data refers to a V-belt drive; Power to be transmitted-75KW; Speed of driving wheel1440rpm;Speed of driven wheel 400rpm;Diameter of driving wheel-300rpm;Center distance-2.5m;Smaller pulley factor-1.07;Service factor-1.3;Correction factor for length-1.07.Design and give the complete details of the drive.

2. Design V-belt drive for the following specifications; Power to be transmitted- 75KW, Speed of driving wheel – 1440rpm, Speed of driven wheel – 400rpm, Diameter of driving wheel – 300mm,Center distance – 2500mm, Small pulley factor, kd – 1.14, Service factor, ks -1.3,Correction factor for length kl – 1.07

3. Design a V-belt drive using manufacture’s data to the following specifications;

Power to be transmitted=75KW;

Speed of driving pulley=1000rpm

Speed of driven pulley – 300rpm

Diameter of driving pulley – 150mm

Diameter of driven pulley – 500mm

Center distance between pulleys – 925mm

Service -16 hrs/day.

4. Design a V-belt drive using manufactures data to the following specifications:

Power to be transmitted=75KW;

Speed of driving wheel=1440rpm;

Speed of driven =400rpm;

Diameter of driven wheel=300mm;

Center distance =2500mm;

Service =16hrs/day.

5. Design a V-belt drive to transmit 15KW to a compressor. The Motor Speed is 1200RPM and the Compressor Pulley runs at 400RPM. Determine the size and numbers of belts.

6. Design a V-belt drive on Manufacturer’s data to the following Specifications;

Diameter of driven Pulley = 600mm,

Diameter of driving Pulley = 200mm,

Center distance between Pulleys = 1000mm (approx.),

Speed of driven Pulley = 400 rpm ,

Speed of driving Pulley = 1200 rpm

Power transmitted = 10KW ,

Service –heavy duty = 16 hrs/day.

UNIT-4

. Design a suitable journal bearing for a centrifugal pump having a following specifications:

Load on bearing-13.25kN;

Diameter of the journal-80mm;

Speed-1440 Rpm;

Permissible bearing pressure-0.7 to 1.4 N/mm^2;

Ambient temperature-30oC. L/D Ratio-1.6 ;

Average temperature of oil-75oC (SAE 40) ;

K – 0.273 for heavy construction and well ventilated bearings and ; temp rise -8 oC. Specific heat of oil = 1710 J/Kg o C . Calculate the cooling requirements.

2. Design a suitable journal bearing for a centrifugal pump having a following specifications: Load on bearing-14kN; Diameter of the journal-80mm; Speed-1440rpm; Bearing characteristic number-30×10^-6 ; Permissible bearing pressure-0.7 to 1.4N/mm^2; Average atmospheric temperature-30*c L/D ratio-2; average temperature of oil-75*c; coefficient of heat dissipation-0.273W/m^2/*c; temp rise -6*c. Calculate the cooling requirements using laches `equations and McKee’s equation for calculating friction Coefficient.

3. Design a Suitable journal bearing for a centrifugal pump to withstand a load of 60kN.the diameter and the speed of the journal are 150mm and 960 rpm respectively.

4. Design a Journal bearing for a centrifugal pump from the following data: Load on the journal = 20kN, speed = 900rpm, type of oil used is SAE10 for which the absolute viscosity at 55oc=17centipoise, ambient temp of oil=15.5oc, Max bearing pressure =1.5N/mm^2 .Heat dissipation co efficient =1232 J/s/m^2/oC. Calculate mass of lubricating oil required for artificial cooling, rise of temp of oil is limited to 10o .

5. Journal bearing is proposed for a centrifugal pump. The diameter of the journal is 150mm and the load on its 40kN and its speed is 900rpm .design and give the complete calculation of the bearing.

6. Design a Journal bearing for a centrifugal pump from the following data:

Load on the journal= 20kN,

Speed = 900rpm

Type of oil used SAE10

Absolute viscosity at 55*c=17cP

Amp ion temp of oil=15.5*c

Max bearing Press =1.5N/mm^2

Heat dissipation Co Efficient =1232 J/s/m^2/*c

Calculate mass o lubricating oil required for Artificial

cooling, if rise of temp of oil is limited to 10*c .

7. A Journal bearing 75mm long support a load of 7.5kN and the 50mm diameter. Journal running at 750rpm the diameter clearance is 0.0693mm. Determine the viscosity of oil if operating temp of bearing surface is limited to 77oC, Ambient temperature is 21oc heat dissipating co efficient is 210W /m^2/oc .

8. In a journal bearing diameter of the shaft is 75 mm , L/D = 1 , Radial Clearance = 0.05 mm, Minimum film thickness = 0.002mm ,Speed of journal = 400 Rpm ,Radial Load = 3.5 KN , Specific gravity of oil = 0.9 , Specific heat of oil = 1.75 KJ/kgoC .Calculate the viscosity of suitable oil, Power lost in friction and

resultant temperature rise.

UNIT-5

1. Explain product development cycle.

2. Explain the Shigley’s design process.

3. Explain the Pahl and Beitz model.

4. Explain the sequential engineering.

5. Explain the concurrent engineering.

6. Explain the 2D transformations with example.

7. Explain the 3D transformations with example.

8. Explain the w i r e f r a m e modeling.

9. Explain the surface modeling techniques.

10. Explain the solid modeling techniques.

11. Compare wireframe model, surface model and solid model.

12. Explain the basic steps of FEA.