Exam Details
| Subject | mechanical engineering | |
| Paper | paper 1 | |
| Exam / Course | indian forest service | |
| Department | ||
| Organization | union public service commission | |
| Position | ||
| Exam Date | 2015 | |
| City, State | central government, |
Question Paper
I.F.S. 2015 fc,eflTll DETACHABLE
MECHANICAL ENGINEERING
Paper I
Tzme Allowed Three Hours
Maximum Marks 200
QUESTION PAPER SPECIFIC INSTRUCTIONS
Please read each of the following instructions carefully before attempting questions.
There are EIGHT questions in all, out of which FIVE are to be attempted.
Question No. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and B.
Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer ..ooklet must be clearly struck off.
AU questions carry equal marks. The number of marks carried by a question/part is indicated against it.
Answers must be written in ENGLISH only.
Unless otherwise mentioned, symbols and notations have their usual standard meanings.
Assume suitable data, if necessary and indicate the same clearly.
Neat sketches may be drawn, wherever required.
SECTION
What is contact ratio for a pair of gears. What is its importance? Determine contact ratio for a pair of two involute gears of 8 mm module having 23 and 57 teeth. If the addenda on the gears
are equal to module, find the contact ratio. 8
I What is critical speed of a shaft Determine critical speed of a shaft 24 mm dia carrying a mass 12 kg at its mid span measuring 1 m. The eccentricity of the mass is 0· 11 mm. The material of the shaft is steel with E 200 GN/m2 .Find the critical speed of the shaft. 8
A circular steel rod tapers uniformly from 40 nun diameter to 150 mm diameter in a length of 400 mm. How much the bar will elongate under an axial pull of 40 kN? Take E 200 GPa. 8
A square bar 20 mm x 20 mm in section, 1·5 m long, is freely supported at its ends in a horizontal position and is loaded with a central load of 200 N. The central deflection due to concentrated load is found to be 5 mm. If the same bar is placed vertically (both ends hinged) and ioaded centrally along its axis, what load is likely to cause the bar to buck.le 8
What are dual-phase steels? Why are dual-phase steels named so? Enlist important characteristics of dual-phase steels. 8
Two pulleys of diameters 480 mm and 640 mm are connected by an open belt drive with distance between two pulleys set at 3 m. It was decided to change the direction of drivep. pu11ey (640 mm dia). How much extra length of the. belt is required? 10
What is partial balancing of reciprocating masses What are its implications Determine, the unbalanced force when the crank has turned by 45° from t.d.c., after the balancing is done by a mass at 320 mm radius. Only 60% of the reciprocating parts and all the revolving masses are balanced. Determine also the magnitude of balance mass. Single cylinder reciprocating engine data is as below
Mass of reciprocating parts 40 kg
Mass of revolving parts 30 kg at crank radius
Speed of the crankshaft 150 rpm
Stroke of the engine 350 mm 10
The torque delivered by a two-stroke engine is represented by
T (1000 +'300sin2 teta- 500cos 26) N-m .
where teta is the angle turned by the crank from inner dead centre. The engine speed is 250 rpm. Mass of the flywheel is 400 kg and radius of gyration 400 mm. Determine
power developed
total peycentage fluctuation of speed
maximum and minimum torques
plot torque vs teta for significant points 20 ·
A cantilever of length L carries a wtiformly distributed load w/unit length over the entire length. The free end is supported from bottom by a rigid prop. Determine the reaction of the prop. 10
A close coiled helical spring made of 8 mm diameter wire has 16 coils. Each coil is 80 mm mean diameter. If the maximum allowable stress in the spring is 150 MPa, determine the maximum allowable load on the spring, the elongation of the spring and stiffuess of the spring. Take G Shearing modulus 82 GPa. 10
A thin cylindrical shell with hemispherical ends as thickness of cylindrical portion and thickness of hemispherical portion The internal pressure for both is same. For no distortion ofthe junction under pressure what will be the value of ratio of thickness if the material has a Poisson's ratio V 0·3. 10
A state of stress at a point are given by
sigma 100 MPa,sigma 80 MPa and txy ±50 MPa.
Determine the principal stresses and the maximum shearing stress.·
Take E=200 GPa, sigma 200 MPa and Poisson's ratio v 0·3.
Determine the factor of safety according to
maximum principal stress theory
maximum strain theory and
maximwn shearing stress theory 10
Silver is face-centred cubic with lattice constant 4·086 A0 Calculate the planar density of atoms on the plane, on the plane and the linear density of atoms along the direction. 10
Calculate percentage of vacant atomic sites in Cu (density 8900 kg/ml) at 20°C. Assume that vacancies in Cu at 400 C are l ·62 x 1022/m3 and constants have following values
delta E .for vacancy formation 0·90 eV per vacancy
Boltzman constant, K 8·62 x 10-s eV/K
Avogadro's number 6-02 x 1023
Atomic mass of Cu 63 ·54 g/mol. 10
A tensile test specimen having a diameter of 12·7 mm was loaded up to a load of 76 kN and its diameter was measured as 12 mm. Compare true stress and strain with engineering stress and strain. 10
What are tp.e .characteristics required for good b-earing material? Compare the properties of bearing bronzes, babbits materials and copper-lead alloys for bearings. 10
SECTION
What is the function of MCU·in NC machine A de servomotor is coupled directly to a lead screw which drives the table of an NC machine tool. A digital encoder which emits 500 pulses per revolution is mounted on the other end df the lead screw. If thelead screw pitch is 5 mm and the motor rotates at 650 rpm, calculate
The linear velocity of the table
The BLU of the NC system
The frequency of the pulses transmitted by the encoder 8
Define a comparator. Write at least six desirable features it should possess. Also name four types of comparators. 8
Write Taylor's tool-life equation. Draw tool-life curves for a variety of cutting tool materials like ceramic, high speed steel, cast alloy and carbide. Why the knowledge of the thrust force.in cutting is important 8
What is bill of material Describe single level and multilevel bill of materials. 8
The following information is available for a factory Daily working hours 8
Number of working days in week 6
Number of operators 20
Standard hours per unit production 4
During a particular week
Number of units produced 48
Absentee man-days
40
Idle time due to load shedding 30 man-days
Find
Absenteeism percentage
Labour utilisation percentage
Productive efficiency of labour
Overall productivity of labour in terms of units produced/week/employee. 8
Write the design criteria of a jig. Draw a box-jig with open sides arranged for drilling two sides of a block. Name four types of clamping devices. 10
Draw a figure to show the wire drawing process and name the. process variables. What is recrystallization temperature Explain impact extrusion. 10
Discuss with a figure ultrasonic machining and its apphcations. Write some characteristics of chemical machining. 10
In economics of machining discuss with the help of figures the variation of machining cost and tool cost with cutting speed. The length of a machining clement is 500 mm and the part diameter is 100 mm OD. Velocity and feed for this material are 6·9 m/min and 0·5 mmirev. What is the time to machine 10
Using LPP Graphical method, find the maximum value of
Z 5x1 +3x2
subject to constraints
3x1 5x2 15
5x1 2x2 10
and x1 x2
Find the values of x1 and x2 for the condition for maximization. 10
7 In queueing theory define the following terms
Queue time
Move time
Wait time
Queue length 10
Draw the network diagram for the given data. Find critical path and the project time duration.
Activity Time Activity Time
1-2 2 4-8 8
1-4 2 5-6 4
1-7 1 6-9 9
2-3 4 7-8 3
3-5 1 8-9 5
4-6 5 10
7 What are the advantages of exponential smoothing method of forecasting The demand for a wooden article in terms of units for last 8 prior months is given in the table. Compute exponentially smoothed forecast for the periods using alfa= O· l and 0·3 .
Month 1 2 3 4 5 6 7 8
Demand (units) 10 18 29 15 30 12 16 8 10
Discuss with a figure Plasma Arc cutting. Write some advantages of plasma arc torch. Also show with figure cost advantages of plasma over oxyfuel. 10
What is QED Describe the following two methods of implementing QFD
House of Quality
Quality Circles 10
A company has demand of 12,000 units/year for an item and it can produce 2,000 such items per month. The cost of one setup is Rs. 400 and the holding cost/unit/month is Rs. 0· 15. Find the optimum lot size and the total cost per year, assuming the cost of one unit as Rs. 4. Also find the maximum inventory manufacturing time and total time. 10
Write a C-program to store the information of AC units in an electronic retail shop. Use bit fields to store the status information. Assume the AC object consists of the following
Company name Samsung LG, Valtas, Blue Star
Capacity One ton, one and half ton
Power consumption
2 star, 3 star, 5 star
Assume appropriate number of bits for each field. 10
MECHANICAL ENGINEERING
Paper I
Tzme Allowed Three Hours
Maximum Marks 200
QUESTION PAPER SPECIFIC INSTRUCTIONS
Please read each of the following instructions carefully before attempting questions.
There are EIGHT questions in all, out of which FIVE are to be attempted.
Question No. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and B.
Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer ..ooklet must be clearly struck off.
AU questions carry equal marks. The number of marks carried by a question/part is indicated against it.
Answers must be written in ENGLISH only.
Unless otherwise mentioned, symbols and notations have their usual standard meanings.
Assume suitable data, if necessary and indicate the same clearly.
Neat sketches may be drawn, wherever required.
SECTION
What is contact ratio for a pair of gears. What is its importance? Determine contact ratio for a pair of two involute gears of 8 mm module having 23 and 57 teeth. If the addenda on the gears
are equal to module, find the contact ratio. 8
I What is critical speed of a shaft Determine critical speed of a shaft 24 mm dia carrying a mass 12 kg at its mid span measuring 1 m. The eccentricity of the mass is 0· 11 mm. The material of the shaft is steel with E 200 GN/m2 .Find the critical speed of the shaft. 8
A circular steel rod tapers uniformly from 40 nun diameter to 150 mm diameter in a length of 400 mm. How much the bar will elongate under an axial pull of 40 kN? Take E 200 GPa. 8
A square bar 20 mm x 20 mm in section, 1·5 m long, is freely supported at its ends in a horizontal position and is loaded with a central load of 200 N. The central deflection due to concentrated load is found to be 5 mm. If the same bar is placed vertically (both ends hinged) and ioaded centrally along its axis, what load is likely to cause the bar to buck.le 8
What are dual-phase steels? Why are dual-phase steels named so? Enlist important characteristics of dual-phase steels. 8
Two pulleys of diameters 480 mm and 640 mm are connected by an open belt drive with distance between two pulleys set at 3 m. It was decided to change the direction of drivep. pu11ey (640 mm dia). How much extra length of the. belt is required? 10
What is partial balancing of reciprocating masses What are its implications Determine, the unbalanced force when the crank has turned by 45° from t.d.c., after the balancing is done by a mass at 320 mm radius. Only 60% of the reciprocating parts and all the revolving masses are balanced. Determine also the magnitude of balance mass. Single cylinder reciprocating engine data is as below
Mass of reciprocating parts 40 kg
Mass of revolving parts 30 kg at crank radius
Speed of the crankshaft 150 rpm
Stroke of the engine 350 mm 10
The torque delivered by a two-stroke engine is represented by
T (1000 +'300sin2 teta- 500cos 26) N-m .
where teta is the angle turned by the crank from inner dead centre. The engine speed is 250 rpm. Mass of the flywheel is 400 kg and radius of gyration 400 mm. Determine
power developed
total peycentage fluctuation of speed
maximum and minimum torques
plot torque vs teta for significant points 20 ·
A cantilever of length L carries a wtiformly distributed load w/unit length over the entire length. The free end is supported from bottom by a rigid prop. Determine the reaction of the prop. 10
A close coiled helical spring made of 8 mm diameter wire has 16 coils. Each coil is 80 mm mean diameter. If the maximum allowable stress in the spring is 150 MPa, determine the maximum allowable load on the spring, the elongation of the spring and stiffuess of the spring. Take G Shearing modulus 82 GPa. 10
A thin cylindrical shell with hemispherical ends as thickness of cylindrical portion and thickness of hemispherical portion The internal pressure for both is same. For no distortion ofthe junction under pressure what will be the value of ratio of thickness if the material has a Poisson's ratio V 0·3. 10
A state of stress at a point are given by
sigma 100 MPa,sigma 80 MPa and txy ±50 MPa.
Determine the principal stresses and the maximum shearing stress.·
Take E=200 GPa, sigma 200 MPa and Poisson's ratio v 0·3.
Determine the factor of safety according to
maximum principal stress theory
maximum strain theory and
maximwn shearing stress theory 10
Silver is face-centred cubic with lattice constant 4·086 A0 Calculate the planar density of atoms on the plane, on the plane and the linear density of atoms along the direction. 10
Calculate percentage of vacant atomic sites in Cu (density 8900 kg/ml) at 20°C. Assume that vacancies in Cu at 400 C are l ·62 x 1022/m3 and constants have following values
delta E .for vacancy formation 0·90 eV per vacancy
Boltzman constant, K 8·62 x 10-s eV/K
Avogadro's number 6-02 x 1023
Atomic mass of Cu 63 ·54 g/mol. 10
A tensile test specimen having a diameter of 12·7 mm was loaded up to a load of 76 kN and its diameter was measured as 12 mm. Compare true stress and strain with engineering stress and strain. 10
What are tp.e .characteristics required for good b-earing material? Compare the properties of bearing bronzes, babbits materials and copper-lead alloys for bearings. 10
SECTION
What is the function of MCU·in NC machine A de servomotor is coupled directly to a lead screw which drives the table of an NC machine tool. A digital encoder which emits 500 pulses per revolution is mounted on the other end df the lead screw. If thelead screw pitch is 5 mm and the motor rotates at 650 rpm, calculate
The linear velocity of the table
The BLU of the NC system
The frequency of the pulses transmitted by the encoder 8
Define a comparator. Write at least six desirable features it should possess. Also name four types of comparators. 8
Write Taylor's tool-life equation. Draw tool-life curves for a variety of cutting tool materials like ceramic, high speed steel, cast alloy and carbide. Why the knowledge of the thrust force.in cutting is important 8
What is bill of material Describe single level and multilevel bill of materials. 8
The following information is available for a factory Daily working hours 8
Number of working days in week 6
Number of operators 20
Standard hours per unit production 4
During a particular week
Number of units produced 48
Absentee man-days
40
Idle time due to load shedding 30 man-days
Find
Absenteeism percentage
Labour utilisation percentage
Productive efficiency of labour
Overall productivity of labour in terms of units produced/week/employee. 8
Write the design criteria of a jig. Draw a box-jig with open sides arranged for drilling two sides of a block. Name four types of clamping devices. 10
Draw a figure to show the wire drawing process and name the. process variables. What is recrystallization temperature Explain impact extrusion. 10
Discuss with a figure ultrasonic machining and its apphcations. Write some characteristics of chemical machining. 10
In economics of machining discuss with the help of figures the variation of machining cost and tool cost with cutting speed. The length of a machining clement is 500 mm and the part diameter is 100 mm OD. Velocity and feed for this material are 6·9 m/min and 0·5 mmirev. What is the time to machine 10
Using LPP Graphical method, find the maximum value of
Z 5x1 +3x2
subject to constraints
3x1 5x2 15
5x1 2x2 10
and x1 x2
Find the values of x1 and x2 for the condition for maximization. 10
7 In queueing theory define the following terms
Queue time
Move time
Wait time
Queue length 10
Draw the network diagram for the given data. Find critical path and the project time duration.
Activity Time Activity Time
1-2 2 4-8 8
1-4 2 5-6 4
1-7 1 6-9 9
2-3 4 7-8 3
3-5 1 8-9 5
4-6 5 10
7 What are the advantages of exponential smoothing method of forecasting The demand for a wooden article in terms of units for last 8 prior months is given in the table. Compute exponentially smoothed forecast for the periods using alfa= O· l and 0·3 .
Month 1 2 3 4 5 6 7 8
Demand (units) 10 18 29 15 30 12 16 8 10
Discuss with a figure Plasma Arc cutting. Write some advantages of plasma arc torch. Also show with figure cost advantages of plasma over oxyfuel. 10
What is QED Describe the following two methods of implementing QFD
House of Quality
Quality Circles 10
A company has demand of 12,000 units/year for an item and it can produce 2,000 such items per month. The cost of one setup is Rs. 400 and the holding cost/unit/month is Rs. 0· 15. Find the optimum lot size and the total cost per year, assuming the cost of one unit as Rs. 4. Also find the maximum inventory manufacturing time and total time. 10
Write a C-program to store the information of AC units in an electronic retail shop. Use bit fields to store the status information. Assume the AC object consists of the following
Company name Samsung LG, Valtas, Blue Star
Capacity One ton, one and half ton
Power consumption
2 star, 3 star, 5 star
Assume appropriate number of bits for each field. 10