Expt 5(a) - Rotating Bending Fatigue Testing.pdf(2)
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Transcript of Expt 5(a) - Rotating Bending Fatigue Testing.pdf(2)
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ROTATING BENDING FATIGUE TESTING
EXPERIMENT NO.5(A)
M E 2 1 8 : S O L I D M E C H A N I C S L A B O R A T O R Y
B A T C H : A 8
0 7 0 1 0 0 4 2 - 0 7 0 1 0 0 4 6
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RO TAT I N G B E N D I N G FAT I G U E T E S T I N G
EXPERIMENT NO.5(A)
AIM
1. Study the effect of cantilever loading on standard rotating bending fatigue specimen.
2. To study the characteristics of S-N curve for ferrous materials.
APPARATUS
1. Specimen
2. vernier caliper.
3. fatigue testing machine
PROCEDURE
The following procedure has been followed:
1. Measure the specimen dimensions most importantly the least diameter (d).
2. Initially adjust the load to zero position.
3. Load the specimen into the collet of machine spindle and check for runout at different locations. Adjust the specimen until required alignment and trueness is achieved.
4. Adjust the poise weight to known value of bending moment and lock it.
5. With the spindle revolving, adjust the cutoff switch as instructed.
6. Note down the value of bending moment applied and also the no. of stress cycle reached by specimen to failure and plot S-N curve.
OBSERVATIONS
The specimen we have taken is ENI (steel with 0.55% carbon) Diameter of specimen=6.38mm.
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Applied load=110 kgf .cm. No. of cycles=17400 At N=103 , the value of S=0.9 Su. And at N=106, the value of S=0.9 Su.
CALCULATIONS
M = πSd3/32
M = 0.0982 Sd3 .
Where, M = setting for poise weight in kg cm.
S = desired bending stress level in specimen at minimum cross-section in MPa.
d = diameter of specimen at minimum cross-section in cm.
M=110 kg.f.cm
d=6.38mm
→S=423.14MPa
Ultimate tensile strength of the specimen=720MPa
log S=2.63
log N=4.24
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GRAPH
ERROR CALCULATION
Slope=2.81-2.56/(3-6)=-0.0833
Equation of line→y=-0.0833x+3.06
Theoretical value at (x=4.24) =2.70
Stress amplitude at x(=4.24) theoretical=501.18MPa
Relative error=(501.18-423.14)/501.18=0.156
3, 2.81
6, 2.56 10, 2.56 15, 2.56
2.5
2.55
2.6
2.65
2.7
2.75
2.8
2.85
0 2 4 6 8 10 12 14 16
log S vs log N
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CONCLUSION
Experimentally determined point is close to the theoretical value.
No.of cycles are less than actual no.of cycles because stress is high enough for plastic deformation to occur, the account in terms of stress is less useful and the strain in the material offers a simpler description .
DETAILS OF THE STUDENTS
ROLL NUMBER NAME
07010042 Repaka Jyoti Swaroop
07010043 Sharath Chandra Pawar
07010044 Puvvada N V Prudhvi Teja
07010045 J G M V Pramod
07010046 Vishnu Narayanan Suresh