Fatigue Testing Machine.docx

MINI PROJECT Report On FATIGUE TESTING MACHINE This mini project report is submitted in partial fulfillment of the requirements of Fourth semester B.E. in Mechanical Engineering.

Submitted By SWATI MISHRA (08) AKSHAY AGRAWAL

(14) AYUSH S. JAIN (21)

DIVYANSHU S. TRIPATHI (25) VEDANG V. BAKHSHI (65) Under The Guidance of Dr. SWATI MOGHE

Department of Mechanical Engineering SHRI RAMDEOBABA COLLEGE OF ENGINEERING & MANAGEMENT, KATOL ROAD, NAGPUR, INDIA-440013

2017-2018

SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND MANAGEMENT

Department of Mechanical Engineering

CERTIFICATE This is to certify that SWATI MISHRA, AKSHAY AGRAWAL, AYUSH JAIN, DIVYANSHU TRIPATHI, VEDANG BAKSHI has completed the mini project work on FATIGUE TESTING MACHINE in partial fulfillment of the requirements of fourth semester B.E. in Mechanical Engineering as prescribed by S.R.C.O.E.M., Nagpur under Autonomous status. .

Dr. SWATI MOGHE Mini project Guide Mechanical Engg. Deptt.

Dr. K.N.Agrawal H.O.D. Mechanical Engg. Deptt.

SHRI RAMDEOBABA COLLEGE OF

ENGINEERING AND MANAGEMENT

FATIGUE TESTING MACHINE PROJECT REPORT SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF DEGREE IN MECHANICAL ENGINEERING. SUBMITTED BY:1. AKSHAY AGRAWAL 2. SWATI MISHRA 3. AYUSH.S. JAIN 4. DIVYANSHU.S.TRIPATHI 5. VEDANG.V. BAKSHI

-14 - 08 - 21 - 25 - 65

GUIDED BY : Dr. S.D.MOGHE ( DEPARTMENT OF MECHANICAL ENGINEERING)

DECLARATION

We hereby declare that the work being presented in project report entitled “ FATIGUE TESTING MACHINE” by us in partial fulfillment of requirement for the mini project submitted in the Department of MECHANICAL ENGINEERING is record of our own work carried out during 2017-18 guided by Dr. S. Moghe.

PROJECT GROUP AKSHAY R. AGRAWAL

-14

SWATI MISHRA

- 08

AYUSH S. JAIN

- 21

DIVYANSHU S. TRIPATHI

- 25

VEDANG V. BAKSHI

- 65

ACKNOWLEDGEMENT The success and final outcome of this project required a lot of guidance and assistance from many people and we are extremely fortunate to have such guidance for the completion of our project work.

We respect and thank our project guide Dr. S. MOGHE for giving us an opportunity to do this mini project and providing us all the support and guidance which made us complete the project on time. We are extremely grateful to her for providing such a nice support and guidance despite of her busy schedule. She is and always will continue to be our inspiration, in absence of whom we would always have fallen short of our mark. We are thankful to our respected Dr. K.N. AGRAWAL, H.O.D for his encouragement and belief in our abilities to succeed in our project. We extend our thanks to our Principal Dr. R.S.PANDE for being constant source of motivation this year. Lastly we are thankful to all the teaching and non-teaching staff of Mechanical Department and our friends for their contribution and support.

ABSTRACT Usually the purpose of a fatigue test is to determine the lifespan that may be expected from a material subjected to cyclic loading, however fatigue strength and crack resistance are commonly sought values as well. The fatigue life of a material is the total number of cycles that a material can be subjected to under a

single loading scheme. A fatigue test is also used for the determination of the maximum load that a sample can withstand for a specified number of cycles. All of these characteristics are extremely important in any industry where a material is subject to fluctuating instead of constant forces. The aim of this thesis work is to discuss the principle of fatigue failure, research the state of the art fatigue testing methods and finally design a verification fatigue test set-up to evaluate the performance of the newly developed dynamic testing machine. A comprehensive study of the underlying principle, stages and numerous factors that makes fatigue such a complex phenomenon was carried out. This was closely followed by research work on the standard fatigue testing methods and statistical analysis of fatigue test results. Based on the knowledge gained from the research work stated above, a four-point fully reversed bending set-up design was developed to put into test the functionality of the dynamic testing machine once it is ready to run and also a planned fatigue test suitable for laboratory exercise in a material science or engineering design class was developed.

Index 1. Introduction  Working of fatigue testing machine  S-N Curve

2. Literature Review 3. Construction Details 4. Cost Analysis 5. Testing  Purpose of testing  Design and calculations 6. Scope and applicability 7. Discussion 8. Conclusion 9. Reference

1. INTRODUCTION There are millions of materials and their uses are also multitudinous. These large number of materials came into existence because of various number of industrial needs

for them. The particular property or combination of properties of material should possess, depends on its specific use and service conditions. With the development of various machines structure of most of them for simple, the necessities for materials which possess properties within narrow specific ranges are arisen. The properties can be classified as; 1. Physical 2. Chemical 3. Mechanical The fatigue testing machine is based on the material property of mechanical properties. These mechanical properties include strength properties like tensile, compression, shear, torsion, impact, fatigue and creep. Fatigue testing machine is used for determine the fatigue limit or endurance limit of any material.

Working of fatigue testing machine:0.5 HP motor is used to drive the MS shaft. O.5 HP motor is connected with 3 inch cast iron pulley and MS shaft is connected with the 6 inch cast iron pulley. Both the pulley is join with V – belt drive & power is transmitted throw motor to 3 inch cast iron pulley , than 3 inch pulley to 6 inch cast iron pulley with the help of V – Belt drive and MS shaft start rotating with 6720 RPM speed. Two pedestal bearing with bearing housing is connected to MS shaft. Both of the end of MS shaft has two bearing housing because they are used to support the MS shaft. So due to this bearing hosing moment of MS shaft is easily done. Between the 6 inch pulley and one bearing housing one 2.5 inch plastic pulley is mounted. Plastic pulley is connected with small cast iron mechanical counters pulley. Than power is transmitted throw plastic pulley to mechanical counter 2.5 inch cast iron pulley and then mechanical counter count the rotation. Before the one bearing housing 3 jaw drill chuck is mounted. Due to connection of MS shaft and 3 jaw drill chuck, rotation of shaft is transmitted throw 3 jaw drill chuck and 3 jaw drill chuck start rotating. At one end of Specimen is fixed at 3 jaw drill chuck and another end of specimen is fixed with load hanger. When machine is start, specimen gets start rotating and due to rotation and load hanger weight twisting, bending & combined twisting – bending stress are produce in specimen and after some rotation specimen gets break. With the help of total loads and number of rotation, S-N curve graph is produce and fatigue limit of specimen is determine.

For determining fatigue limit we should take three reading .for taking three reading break three specimen. Then put all three reading on S-N curve graph and in this way we can find the specimens fatigue limit.

S-N CURVE:Fatigue is generally understood as the gradual deterioration of a material which is subjected to cyclic loads. In fatigue testing, a specimen is subjected to periodically varying constant amplitude stress. The applied stresses may alternate between equal positive and negative value from zero to maximum positive or negative value, or between equal positive and negative values or between unequal positive and negative values. A series of fatigue tests are made on a number of specimens of the material at different stress levels. The stress endured is then plotted against the number of cycle sustained. By choosing lower and lower stresses, a value may be found which will not produce failure, regardless of the number of applied cycle. This stress value is called the fatigue limit of the material or the endurance limit. The plot of the two terms is called stress cycle diagram or S-N diagram. The fatigue limit may be established for most steels between 2 and 10 million cycles. Non-ferrous metals such as aluminum usually show no clearly defined fatigue limit. (Mark´s Standard-Handbook/Strength of Materials).

Fig. 1.1. S-N Curve for Fatigue failure

2. LITERATURE REVIEW 2.1. Literature Design of a Cantilever - Type Rotating Bending Fatigue Testing Machine K. K. Alaneme, Vol. 10, No.11, pp.1027-1039, 2011 Jmmce.org Printed in the USA. Journal of Minerals & Materials Characterization & Engineering Department of Metallurgical and Materials Engineering Federal University of Technology, Akure, PMB 704, Nigeria This research is centered on the design of a low–cost cantilever loading rotating bending fatigue testing machine using locally sourced materials. The design principle

was based on the adaptation of the technical theory of bending of elastic beams. Design drawings were produced and components/materials selections were based on functionality, durability, cost and local availability. The major parts of the machine: the machine main frame, the rotating shaft, the bearing and the bearing housing, the specimen clamping system, pulleys, speed counter, electric motor, and dead weights; were fabricated and then assembled following the design specifications. The machine performance was evaluated using test specimens which were machined in conformity with standard procedures. It was observed that the machine has the potentials of generating reliable bending stress – number of cycle’s data also the machine has the advantages of ease of operation and maintenance, and is safe for use

2.2.

Literature 2:-

Design and Characterization of a Fatigue Testing machine Gbasouzor Austine Ikechukwu, Member, IAENG, Okeke Ogochukwu Clementina and Chima Lazarus Onyebuchi Proceedings of the World Congress on Engineering and Computer Science 2013 Vol I WCECS 2013, 23-25 October, 2013, San Francisco, USA Mechanical Engineering, Anambra State University, P. M. B. 02 Uli, Many engineering machines and mechanical components are subjected to fluctuating stresses, taking place at relatively high frequencies and under these conditions failure is found to occur. This is “fatigue failure”. And this led to the invention of a fatigue testing machine. In view of effective design that will not fail accidentally, this research is conceived. This testing machine will determine the strength of materials under the action of fatigue load. Specimens are subjected to repeated varying forces or fluctuating loading of specific magnitude while the cycles or stress reversals are counted to destruction. The first test is made at a stretch that is somewhat under the ultimate strength of the material. The second test is made at a stress that is less that than that used in the first. The process is continued, and results are plotted.

2.3.

Literature 3:-

Design and Fabrication of Rotating Bending Fatigue Testing Machine – International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056

Volume: 03 Issue: 04 | Apr-2016 www.irjet.net p-ISSN: 2395-0072 Santosh J. Chauhan1, Aarti Misal2, Akanksha Jadhav3, Rahul Jadhav4 Abhir Bhalavi5, Rohit Jagdale 6 1Assistant Professor, Mechanical Engineering Department, Fr. C. Rodrigues Institute of Technology, Vashi, Navi, Mumbai, India. 23456 Undergraduate Students. Mechanical Department, Fr.C.Rodrigues Institute of Technology. Fatigue failures are reported to account for more than 75% of documented materials failures of which a great percent occur catastrophically. Study of fatigue life is essential in many industrial and specialized fields such as aerospace, defense, power generation etc. Fatigue life of a component can be found by various fatigue testing machines based on the loading condition. In the present study a low–cost four point loading rotating bending fatigue testing machine is designed, fabricated and tested. The design principle is based on the adaptation of the technical theory of bending of elastic beams. The machine performance was evaluated using test specimens which were machined in conformity with standard procedures. It was observed that the machine has the potentials of generating combined bending and torsional stress. Specimens of diameter varying between 6 to 8 mm where subjected to loads between 30Kgs to 90Kgs and the number of cycles to failure was found by both experimental method and theoretical calculations. It was observed that the results are under close agreement.

3. CONSTRUCTION DETAILS

3.1 Construction of fatigue testing machine:This fatigue testing machine consist of 0.5 HP motor , one plastic & 3 cast iron pulley , one MS shaft, two bearings ,one V- belt & one round belt, mechanical counter, 3 jaw drill chuck , loads , load hanger & frame. One 6 inch cast iron pulley is mounted on 0.5 HP motor & 3 inch cast iron pulley is mounted on MS shaft. Both the pulleys are connected with V – belt so power is transmitted throw motor to MS shaft. 3 inch cast iron pulley is mounted at the center of MS shaft. 3 jaw drill chuck is mounted at the one end of MS shaft. One plastic pulley is also mounted in MS shaft and it is connected to mechanical counter. This mechanical Counter has one small cast iron

pulley and this mechanical counter pulley is connected to MS shaft plastic pulley throw rubber round belt. Two pedestals bearing with bearing housing is mounted on the both of the ends of MS shaft. This bearing is used to support the MS shaft. Specimen is putted in 3 jaw drill chuck, so one end of specimen is connected to 3 jaw drill chuck and another end of specimen is connected with load hanger with loads. One rounded rubber thread is used to fixed load hanger in specimen one end. This entire component is mounted in frame and fatigue testing machine is complete.

3.2 Layout Of Fatigue Testing Machine:-

Fig 3.2.1 Layout Of Fatigue Testing Machine

3.3 Components:Part list of machine:-

1. 2. 3. 4. 5. 6. 7.

Motor. MS Shaft. Pedestal bearing. 3 jaw drill chuck. Specimen. (MS) Loading hanger. Frame of angle.

3.3.1 Motor:-

Fig: 3.3.1 Electric Motor The electrically driven motor is use to rotate the shaft and mechanical counter is used to count the number of revolution of shaft which is driven by the belt arrangement.

Motor specification :1. 2. 3. 4. 5.

3.3.2. Pulleys:-

Power Main supply RPM Frequency Motor shaft diameter

-

0.5 HP 220 VOLTS ( Single Phase) 2800 50 HZ a-c 19 mm

Fig: 3.3.2 Pulleys

In all we used 2 cast iron pulleys. The 3 inch cast iron pulley is mounted on motor shaft and 6 inch pulley is mounted on main shaft also the 3 inch plastic pulley is mounted on shaft which drives the counter as shown in fig.3.2. A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable, supporting shell is referred to as a “block.”A pulley may also be called a sheave or drum and may have a groove or grooves between two flanges around its circumference. The drive element of a pulley system can be a rope , cable ,belt , or chain that runs over the pulley inside the groove or grooves. Pulleys are also assembled as part of belt and chain drives in order to transmit power from one rotating shaft.

3.3.5. Shaft:-

Fig. 3.3.5 Shaft

The shaft is made up of mild steel with minimum diameter of 16mm at the point where chuck is mounted. The maximum diameter of shaft is 28mm and the diameter at the parts where bearing are press fitted is 25mm, length of shaft is 330mm.The shaft Rotates at speed of 3000rpm or more. The shaft is supported by two bearing housing. The details of the shaft are as shown in fig.3 .5



They are mainly classified into two types:-

Transmission shafts are used to transmit power between the source and the machine absorbing power; e.g. counter shafts and line shafts. Machine shafts are the integral part of the machine itself; e.g. crankshaft .



Materials:-

The material used for ordinary shafts is mild steel . When high strength is required, an alloy steel such as nickel, nickel-chromium or chromium-vanadium steel is used. Shafts are generally formed by hot rolling and finished to size by cold drawing or turning.

3.3.5. Bearing Housing:-

Fig: - 3.3.5. Bearing housing

Bearing housing are used to locate the bearing which is turn support the shaft for proper working. It is split type housing, the upper part is fitted to the base part by means of nuts and bolts. It is made of cast iron. Firstly the bearings are mounting on the shaft by press fitting. Then we placed the shaft in housing in such a way that the bearing of shaft gets located into the slots provided in the housing. Finally we put the cap of the housing and tighten it with nuts and bolts. Bearing housings are usually made of grey cast iron. However, various grades of metals can be used to manufacture the same, including ductile iron, steel, stainless steel, and various types of thermoplastics and polyethylene-based plastics. The bearing element may be manufactured from 52100 chromium steel alloy (the most common), stainless steel, plastic, or bushing materials such as SAE660 cast bronze, or SAE851 oil impregnated sintered bronze, or synthetic materials.

3.3.6. Jaw drill chuck:-

Fig: 3.3.6 Jaw drill chuck

The chuck is used to hold the specimen it is a three jaw drill which is selfcentered. It has three jaws which are housed in slot cut 120 apart in the chuck body, which houses these jaws having thread cut at the back that mashes with a ring nut. The ring nut is attached to the sleeve. Bevel teeth are cut along around the sleeve body. This sleeve may be rotated by rotating a key having bevel teeth on the sleeve. The rotation of the sleeve causes the ring nut to rotate in affixed position and the entire three jaws center, holding or releasing the job. The chuck is having 16TPI threads at the back and hence it is screwed to the shaft. Some high precision chucks used ball thrust bearings to reduce friction in the closing mechanism and maximize drilling torque. One brand name for this type of chuck, which is often generalized in colloquial used although not in catalogues, is super-chucks.

3.8. Specimen:-

Fig. 3.3.8. Specimen

Specimen material: - Mild steel. Manufacturing process:-it is made by following process like turning, grinding and surface finishing. The specimen is made accounting to the IS code 5075. The dimension is as shown in fig 3.3.8. In this particular works are have tested only mild steel specimen was of mild steel.

3.3.9. Loading Hanger:-

Fig.3.3.9. Load hanger

The loading assembly consists of one round type of thread to which a load is attached to it. The number of load is made is up of hollow raw material rod. As there are total 20 Kg of weights which is used to attach to the specimen with the help of rounded rope.

3.3.10. Frame:A frame is made of a steel and welded together so to form the stable platform the supporting various components mounted on it. The description of the different part required for the fabrication and high strength. Designation

-

ISA 5050

Size

-

6 x 13 (mm)

Thickness (T)

-

6.0 (mm)

3.3.11. Bearing:-

Bearing used are ball bearing. [SKF mark] made up of high quality steel. In all we have used two bearing which are used to support the shaft i.e. [SKF6205]. Ball bearings tend to have lower load capacity for their size than other kinds of Fig: 4.3.11. Bearing rolling element bearings due to the smaller contact area between the balls and races. However, they can tolerate some miss alignment of the inner and outer races.

.

3.3.12.Setting Up The Machine The base should first of all be set leveled so that the weight will hang perpendicularly to the axis of the specimen. Wires in conduct from the power supply

are run to the connecting block in the base of the machine and soldered to the lugs provided. The machine is equipped to operate from an AC power source at 10volts, 60 cycles, and single phase. Motor and relay equipment to operate from a power source of different rating can be provided on special order. With mild steel legs, the machine is set on five rubber tyres. The weight hanger is of such length that it will clear the desk since it is mounted on the legs. A shock absorber in the hanger prevents the slight vibration of the housing from being impacted to the weight. The base is provided with holes so it can be bolted down if desired. Assemble the housing with a sample of specimen provided in accordance with the direction given below, and start the machine to see if there is any misalignment. This will be indicated by noise and vibration. Examine the housing wind for oil. It should stand about midway of the windows when the machine is idle.

Fig 3.3.13 Fatigue testing machine

4. COST ANALYSIS

Sr.No.

Total

Components

Rates ( INR)

1

AC motor

5000

2

Bearing Housing

400

3

Specimen

100

4

Drill chuck

500

5

Frame

600

6

Weights

-

7

Coupling

500

7 Parts

6100

5. TESTING Purpose of testing:“One of the important considerations in design of a machine is ‘strength’, a characteristic that enables the device to serve its function safely and well”. Mechanical testing is concerned with determination of load and change in length. These are than translated into terms of stress and strain through considerations of the dimensions of the test piece. Mechanical properties include the strength properties like tension, bending, compression, shear, torsion, impact, creep, fatigue and hardness. Fatigue test is a long time test in which the specimen is subjected to repeated load of small magnitude whereas the creep test can be practically considered as a high temperature tensile test. Taking into account all the properties, these tests can be classified into two major categories as follows:1. Reactive test. 2. Service condition test. Reactive test:In reactive test, the tensile, bending, shear, compression, torsion test are accommodated, while the fatigue, creep and impact test are the actually service

condition tests. In any testing process, the actual use of material is kept in view and the necessity for the test is first decided. The two groups of tests, destructive type and non-destructive type can be classified further:-

Destructive Type:a) b) c) d) e) f) g) h)

Tension Test. Compression Test. Shear Test. Bending Test. Impact Test. Creep Test. Fatigue Test. Hardness Test.

a) b) c) d) e) f) g) h)

Visual Examination. Leakage Testing. Penitent Method. Magnetic Method. Acoustic Method. Radiography. Thermal Tests. Electrical Methods.

Non-destructive type:-

Test Procedure:A number of standards test specimens are made from the metal under test. The first specimen is tested at a high value of load. The number of revolutions the specimen experienced before fracturing is noted on the counter. Another specimen is fixed in the machine and this time, the load is slightly decreased the number of revolutions that are indicated in the counter this time, will be more than that in the previous case. The other specimens are also time reducing the load, and noting the number of revolutions .The procedure is continued until a value of stress is reached when the specimen dose not fail, say even after 10 million revolutions. From the data thus obtained, the stress number of reversals of referred to as an S-N diagram, is plotted .The stress value is plotted on the Y-axis &the number of stress value at which the curve become nearly horizontal, is taken to be endurance limit of the metal. Fatigue Failure In Service:Fatigue failure is most common in shafts, main shafts of automobile and naval vessels etc. The keyways, changes in sections, screw threads & oil-holes, are the general originators fatigue failure. Very interesting fatigue failure occurred in the midfifties due to which the B.O.A.C comet air craft were cost.

The plane leakages recovered from the sea beds were investigated into and it was determined that the fatigue failure of the fuselage. It was assumed that the cracks originated at the corners of the aerial windows. Torsion Fatigue Testing:The advent of torsion bar suspension of automobiles and the requirements of the service condition testing of springs brought out the necessity of torsion fatigue testing. The Scheck Torstar is one that operates on the principle of mechanical response. torsion fatigue can also be determined by the combined stress fatigue testing machine this machine, practically can test the fatigue strength under any type of loading by a suitable variation of the specimen mounting

The Role Of Testing:The extensive use of experimental studies preliminary to design and construction of new mechanical and structural elements and use of testing procedure for control for established process for manufacturing and construction are significant as well as recognized features of our technical development. Practically all branches of engineering those dealing with structures and machines are concerned with materials the properties of which must be determined by test successfully mass production depends on inspection and control of quality of manufactured product which implies system of sampling and testing. The preparation of adequate specifications and acceptance of material purchased under specifications involved and understanding methods of testing and inspection. Engineering research and development functions in large measures on an experimental basis and call for carefully planned and well devised test.

DESIGN & CALCULATION :Design Of Shaft & Bearings:. TO FIND TENSION T 1 & T 2 :2 πNT 60 P = Power (W) N = Speed (RPM) T = Torque (N-MM)

Power = Where,

0.5 x 735 =

2 π × 1496 ×T 60

T = 2.34 × 103 N-mm T1 T2

e µθ cosec

=

β

µ = 0.3 …… (From Design Data Book) Sinβ =

R 1−¿ R x ¿

2

Where, x = Distance between two center of pulleys. R1

= Radius of larger pulleys.

R2 = Radius of small pulley.

R1 = 750 mm,

X = 520 mm,

R2 = 35 mm

But 2β = 40 ° Sin

β = β

R 1−R2 2x

=

750−350 2 ×520

= sin −1 (0.038)

β = 2.20 ° 2β = 4.40 ° θ = 80 + 2 × 4.40

θ = 188.82 ° T1 T2 T1 T2

=

e

µθcosecβ

= e 0.3×188.82× cosec 2,92

T1 T2 ( T 1 −T 2 )

= 17.85 ×r p

=T

Where, r p = radius of pulley (6 inch) = 75 mm

T1 T2

= 17.85

T 1 =17.85T 2 ¿ (17.85 T 2 −T 2 )×75=1.25× 103 T 1 = 17.85 ×T 2 ( T 1 −T 2 ) ×r p (17.85

=T

2−¿ T 2 ) × 75 = 1.25 ×103 T¿ T2 T1 T1

= 1.02 N

= 17.85 ×T 2 = 17.85 × 1.02 T1

= 18.88 N

Reaction considering belt tension:R A + R B=3.9+T 1 +T 2+147 R A + R B=3.9+18.88+ 1.02+147 R A + R B=170.8 N

Taking moment about A:99.5 × R B=¿ 3.9 ×107.5+ ( 18.88+1.02 ) ×138.5+147 × 227 RB =183.17 N R A + R B=170.8 R A + 1832.17 = 170.8

RA

Negative

R A =−12 .37 indicates that reaction at A is in downward direction. Torque on shaft

=

T 2.4

We are increasing the speed by 2.4 times So,

Torque on shaft

= 520.83

N –mm

For the Equivalent Torque:Te

For M:-

=

√ M2 +T 2

Find SFD & BMD 3.9N

19.9N

147N

107.5

77.5 138.5

61

Rᴀ = 12.37

Rʙ = 183.17 N

For SFD:-

SFA

= -12.37 N

SFCL = 147- 183.17 = -12.37 N SFCR = -12.37+ 3.9 N = -8.47 N SFBL = 3.9 -12.37 = -8.47 N SFDR = -12.37 + 3.9 + 19.9 = 11.42 N SFDR = 19.9 + 3.9 -12.37 = 11.42 N SFBL = -12.37 + 3.9 + 19.9 – 183.17 + 147 = 183.17 N SFBR = 147 - 183.17 + 19.9 + 3.9 -12.37 = 183.17 N For BMD:BMA = 0 N BMC = -12.37 × 107.5 = -1329.778 N BMD = -12.37 × (138.5) – 3.9× 31 BMD = -1837.14 N BME = -12.37 × 199.5 – 3.9 × 92 – 19.9 × 61 BME = -4040.51 N BMB = 0 N

SFD & BMD:-

.˙. M = 4040 .51 N .˙.

Te =

√ M2 +T 2

Te =

.˙.

√ 4040 . S ₁2+520.83 2

T e = 4073.93 N-mm

.˙.

.˙. Since minimum diameter of shaft is 16.8 mm .˙. D = 16.8 mm

Te =

4073.93 =

π × τ × D³ 16

π × τ × 16.8³ 16

.˙. τ = f s = 8.75 N/mm²

.˙. Equivalent moment:Me =

π × 6ъ × d³ 32

Me =

1 × [M + T e ] = 2

Me

1 × [4040.51 +4073.93] 2

= 4057.22 N-mm

4057.22 =

π × 6ъ × 16.8³ 32

.˙. Fъ = 6ъ = 17.43 N/mm² Taking value, Fъ = 6ъ = 17.83 N/mm² Maximum permissible working stress for shaft without allowance for key way= 88N/mm². Since the stress value that we have obtained i.e. 17.43 N/mm² is much less than the max permissible stress value i.e. 88 N/mm² and our design is safe.

Selection of bearing used for supporting the Shaft:-

Calculate the reactions

R A ∧RB

R A + R B = 190 N ------1

Taking moment about ‘A’ (3×3 107.5) + (30× 138.5) + (157×277) = 199.5 RB

= 240.43 N

R A = -50.43 N Negative sign indicates that at section ‘A’ is in downward direction. Out of the two bearing the max reaction is on bearing design the bearing for load = 240.43 N equivalent load P = (XFV+ YFA) S P = (1× 240.43 + 0) 1.1 P = 264.43 N a) Dynamic capacity of bearing Life of bearing = 40000 hours (M/C for Continuous use ) C/P = 22.9 C = 22.9 x 264.43 C = 6055.44 N Select deep groove ball bearing for C=

6055.44 9.81

= 617.27 Kgf

And Max permissible speed 6720 rpm. The bearing we have chosen as Design No. [SKF] = 6205 having dynamic capacity = 1100 kgf. And max permissible speed 13000rpm.

b) Design of loading assembly bearing:Equivalent load (P) = (1x 147 + 0) 1.11 P = 163.17 N Life of the bearing = 20,000 hour C/P = 14.50 C = 14.50 x 163.17 = 2365.965 N

R A , Hence we will

Select deep groove ball bearing for C = 241.178 Kgf. And Max. Permissible speed

= 6720 rpm.

We have chosen Design no. (SKF) = 6202 having dynamic capacity = 610 kgf. And max rpm

= 16000.

OPERATING PRINCIPLE:The specimen loading arrangement results in a constant bending moment W × L over the test length of specimen. Where,W = Load (kg) L = Length =95.5 mm ∴ Bending moment (M) = W × L

∴ Bending moment (M) = 95.5 x W (kg-mm) ∴ Bending strength (fb) = M/Z kg/mm2 ∴ Z = section modulus =

fB =

Where:-

d3 32 M ×32 π ×d ³

W in kg RB

In kg/mm2

M in kg-mm d in mm Note: - The load ‘w’ includes the weight of loading assembly and hanger.

Testing example:The testing machine is mainly used for the two purposes 1. To study the behavior of material to draw S-N curve. 2. To study the material for expected number of revolution at specific stress. In the first case, large number of specimen out of the same stock of subject material is prepared. Different loads are applied producing different bending stresses on this specimen and the number of revolutions at which specimen fail are revolution on x-

axis and y-axis. The S-N dia. which is a graph of stress on y-axis and number of revolutions on x-axis on semi logarithmic graph is then drawn. This diagram tells us about the behavior of material under application of repeated load. In the second case, generally the bending stress to be applied is decided upon the design requirements suppose the design requirement is such that it should with stand a bending stress of 4000 Kg/mm². Then the load is to be applied is calculated as follows:Rb =

W=

95.5× W ×32 π×d ³

π × d ³ × Rb 32× 9.55

Where, d=0.70cm W=

3.14 ×(0.70) ³ × 4000 32 ×9.95

∴ W=15.33Kg This load is applied and the number of revolution at which the specimen fails are recorded and checked against the expected.

Observation & S-N Curve Diagram:We test the specimen of the material on the machine for different stress value, i.e. for different loads. The number of stress cycles after which the specimen fails is noted from the mechanical counter reading. The first specimen is tested at large stress value so that the failure will occur after small number of application of stress. Succeeding specimens are then tested at lower stress value so that the number of revolution required will be increase or the stress decreases.

At least three reading should be taken for each load and the observation table is made. Ex. (1) Load 20kg .˙. Stress =

Load Area

.˙. Load [N] =

20 × 9.81 Area

Area =

π ×d² 4

Area=

π ×7² 4

Area = 5.09 N/ mm² Where d = 7 mm So stress = 5.09 N/ mm²

Observation Table:Stress

Load in N

Stress

No of revolution.

1

20 × 9.81 N

5.09 N/mm²

2455 rpm

2

17 × 9.81 N

4.33 N/mm²

2625 rpm

3

15 × 9.81 N

3.82 N/mm²

2792 rpm

After taking the reading we plot curve between stress on Y axis and number of stress cycles on X axis on semi logarithmic graph. The number of the curve is as shown in Fig.

Fig: - S-N Curve

Result Analysis We test the specimen of the material on the machine for different stress value i.e. for different loads. The number of stress cycles after which the specimens fails is noted from the mechanical counter reading. The first specimen is tested at larger stress value so that the failure will occur after small number of application of stress. Succeeding specimen are then tested at lower stress values so that the number of revolution required will be increase as the stress decrease. At least three reading should be taken for each load and the observation table is made. We multiply the reading of mechanical counter by 5.4 so as to get the actual number of stress cycles. After taking the readings we plot curve between stress on Y-axis and number of stress cycles on X -axis on semi logarithmic graph. As results S-N curve shows the fatigue limit of tested specimen and life of specimen is determined.

6.SCOPE AND APPLICABILITY

Most of element of structure or machine that are subjected to repeated stresses are made of metal principally steel-only in certain type of structure does the question of fatigue require consideration. In general, fluctuation in the stress. In bridges and building are large enough occur often enough to produce failure. In instances, notably in rapidly moving machines, and in parts subjected to server vibration, appreciable stress fluctuation may occur during the useful life of machine or structure. The crank shaft of piston type airplane motor is subjected to about 20million reversals of stress in less than 200 hours of flying. Fatigue must be considered in design of many parts subjected ti cycles of stress such as motor shaft, bolts, springs, gears teeth, turbine blades, airplane and automobile parts, steam and gas engine parts and gas engine parts and many machine parts subjected to cyclic loading. .

7. DISCUSSION:-

7.1. Advantges Of Fatigue Testing Machine:1. 2. 3. 4. 5. 6. 7.

This Fatigue testing machine is suitable for determining any shapes & sizes specimen fatigue limit. Any type of materials specimen can easily tested by our fatigue testing machine. Machine satisfy the all particular property of component in which the component proved to be deficient by testing. Proper life of specimen can easily determine by this machine. No requirement of any skilled worker. Total cost of this machine is less as compare to any other machine which present in market. Size of machine less as compare to other machine which present in market.

7.2 Limitation Of Fatigue Testing Machine:1. Machine is totally manually operated. 2. Requirement of operator is necessary. 3. Testing is purely based on calculation. 4. Machine take more time for determining fatigue limit of specimen due to calculation. 5. Wastage of specimen is done due to testing. 6. Machine used power supply for testing.

7.3 Precautions Of Fatigue Testing Machine:1. Proper arrangement of all component of fatigue testing machine. 2. Tightly fitting of all nuts and bolts. Loose fitting of nuts and bolts cause more vibration on machine. 3. Do not take hand on belts drive and pulley while machine running. 4. Properly fitting of specimen in 3 jaw drill chuck. 5. While taking test reset every time mechanical counter. 6. Proper maintenance and oiling of machine in every 6 to 10 days.

8. CONCLUSION From the S-N curve graph we get the value of endurance limit or fatigue limit of the tested material. The stress value at which the curve turns parallel to X- axis

indicating that if we apply stress below this value for infinite number of stress / cycles the specimen will not break this stress value is called endurance limit or fatigue limit of the material. In our fatigue testing machine case, we have carried out the testing of mild steel and the endurance limit was found out to be 4 kg/ mm2 . When fatigue stress is induced on a material due to the action of force reversing and fluctuating, a failure known as fatigue failure takes place. The study and test conducted so far shows that fatigue failure cannot be predicted accurately since material failure under fatigue are affected not by just reversal loading alone but also the number of revolution (cycle per minute) and fluctuating stress and other factors such as temperature, atmospheric condition, both internal and external defect on material subjected under fatigue stress. Such defect includes notch, inclusion, stress concentration and non-homogeneity Suggesions:This fatigue testing machine is used for determining the endurance limit or fatigue limit of any material .for determining the endurance limit or fatigue limit of any material this type of machine is very important. Many fatigue testing machine are present in market but all these machine are very costly and big in size and shape .our machine cost is less as compare to any other machine which are present in market and our machine size and shape is also less as compare to any other machines which are present in market. But one limitation of our fatigue testing machine is that our machine is totally manually operated and one operator is necessary for our fatigue testing machine. But future scope for our machine is, we add some sensor on our fatigue machine and make fully automatic fatigue testing machine in less price and in less size.

9. REFERENCES 1. Machine Design - R.S. KHURMI - S. Chand Publication

2. http://qspace.qu.edu.qa/bitstream/handle/10576/7995/06-90-304-fulltext.pdf;sequence=8 3. http://slideplayer.com/slide/5334039/ 4. International Journal of Research in Advent Technology, Vol.4, No.2, February(Paper id 42201609)