Jordan University of Science and Technology
Faculty of Engineering
Industrial Engineering Department
Engineering Materials lab (IE367)
Experiments Name: Fatigue Test
Due Date: 17-11-2020 Wednesday (12:00 AM )
Name : Fatema Eyad Abu-Zaideh
ID: 126746
Section: 4 ( 2:30 – 4:30 )
Objectives 3
Introduction 3
Experimental Setup 4-5
Experimental Procedure 5
Experimental Results 6-7-8-9-10-11
Discussion and Analysis 11
Conclusion 11-12
References 12
Page|1
Table of Contents
1-Cover page
Objectives -2
Table of contest -3
Introduction -4
Experemental Setup-5
Experemental procedure-6
Experemental Results-7
Discussion and analysis-8
Conclusions-9
REFERENCE
Page|2
:Objectives
1- To understand the behavior of different materials under fluctuating
(cyclic or periodic) loads in service.
2- To differentiate the appearance of fatigue fracture from other types of
fractures.
3- To draw the S-N diagram and determine the endurance limit.
Introduction
Fatigue failure accounts for the majority of mechanical failure of metallic
materials subjected to cyclic loads. Fatigue failures result from repeated
applications of stress which is usually well below the static yield stress.
Fatigue cycles are often completely reversed state of stress, i.e. tension
and compression in a rotating beam but can also be tension-tension. In all
cases the number of cycles to produce failure increases with the lowering
of the stress level.
Fluctuating load The fatigue limit is an additional mechanical property
which is required to rate the material under such types of action, this
property can be defined as the maximum stress the material can be
subjected without fatigue failure, regardless to the number of cycles.
The variety of fatigue test programs reported in the literature is large,
and the number of publication is steadily growing. Different types of
fatigue loads, specimens, environments, and test equipment are used.
Fatigue tests generally require significant experimental effort and time,
which implies that these tests are more expensive than simple tests of
several other mechanical properties
There are different types of fatigue testing machines:
Fig 1: fatigue test machine
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Experimental setup
Fatigue Testing Machine & specimens (In the experiment we used Aluminum)
specimen Fig 2: fatigue test
:Machine Fatigue Testing
Fatigue test machines use static,
dynamic, and fatigue tests to
evaluate the sturdiness of raw
materials, components or
finished products. Fatigue
testing machines conduct tests by
measuring the force put onto the
sample over many, many cycles until the sample fails. Fatigue tests help to determine a test
sample's life
expectancy under actual service loads in real-world applications. The elongation, impact,
tearing and indentation tests performed by fatigue testing machines are used to determine
peak load, elongation percentage, modulus of elongation, and yield to break, all of which are
crucial factors for describing a material's durability .
In this machine a standard specimen is used. The specimen is supported in a rotating
chunk at one end, and at the other end a load (P) is applied through a ball race. In this type of
cantilever loading each point in the circumference of the specimen is subjected to alternate
stress between tension and compression once during each revaluation. To find the fatigue
limit a number of specimen are tested in this way, each at different load , until failure occurs.
:The applied stress can be calculated from the following general bending equation
YM
I
Fatigue Testing Machine
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location of specimen in the
machine
Experimental Procedure:
1. Select two materials, one shows a fatigue limit (ferrous metal) and the other does
not show this limit (non-ferrous metal).
2. Take at least two standard specimens from each material.
3. Mount the specimen in the machine and fix it properly, then apply the required load
by the loading system.
4. Make sure, that the reading of the revolution counter is zero, and then start the
machine.
5. When the specimen is broken, read the number of revolutions (cycles), as indicated
by the revolution counter of the machine.
6. Determine the applied stress.
7. Tabulate the obtained results
***You have to examine the appearance of the fatigue fracture & plot the S-N
diagram for each tested material.
:Experimental Results and Calculations
D
2
=C
4
πD
46
=I
M C
σxaM =
I
Page|5
: Where
C = Distance from the neutral surface (half the thickness for a sample of symmetrical
cross section). ( mm or inch )
D = Diameter of specimen. ( mm or inch )
I = Second moment of area of the cross section. ( mm4
or inch4 )
σ Max =¿Maximum applied stress ( Pa or psi )
M = Bending moment ( N.m or Ib.inch(
Results and Calculations:
Table 1: Data for Cold Worked Steel
(Fracture Shape : flat & burnished with crystalline appearance)
Page|6
Do Moment
Do( inch) # of Cycles Max Stress (psi) I
( mm) (Ib.In)
C ( inch4 )
9.57 0.37677 240 40000000 0.18838 0.00098
45687.97566
2 6 9
9.57 0.37677 250 18875100 0.18838 0.00098
47591.64131
2 6 9
9.57 0.37677 260 827000 0.18838 0.00098
49495.30696
2 6 9
9.57 0.37677 270 477000 0.18838 0.00098
51398.97261
2 6 9
9.57 0.37677 280 427000 0.18838 0.00098
53302.63827
2 6 9
9.57 0.37677 290 425600 0.18838 0.00098
55206.30392
2 6 9
9.57 0.37677 295 340000 0.18838 0.00098
56158.13674
2 6 9
9.57 0.37677 300 254000 0.18838 0.00098
57109.96957
2 6 9
9.57 0.37677 320 107000 0.18838 0.00098
60917.30087
2 6 9
9.57 0.37677 330 95900 0.18838 0.00098
62820.96653
2 6 9
9.57 0.37677 340 95300 0.18838 0.00098
64724.63218
2 6 9
9.57 0.37677 350 93500 0.18838 0.00098
66628.29783
2 6 9
9.57 0.37677 360 87100 0.18838 0.00098
68531.96348
2 6 9
9.57 0.37677 370 77100 0.18838 0.00098
70435.62914
2 6 9
9.57 0.37677 380 74000 0.18838 0.00098
72339.29479
2 6 9
9.57 0.37677 390 72700 0.18838 0.00098
74242.96044
2 6 9
9.57 0.37677 390 66500 0.18838 0.00098
74242.96044
2 6 9
9.57 0.37677 390 51000 0.18838 0.00098
74242.96044
2 6 9
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80000
70000
S-N Diagram
60000
50000
Max stress
40000
30000
20000
10000
0
0 10000000 20000000 30000000 40000000 50000000
# of cycles
S-N Diagram for Cold Worked Steel
**fatigue limits = 45000 psi ( nearly )
Page|8
Table 2: Data for Cold Worked Aluminum
(Fracture Shape: flat & burnished with crystalline appearance )
Max
# of Moment Do ( mm
Stress Do( inch)
Cycles ( Ib . In ) )
( psi ) C I ( inch4 )
1284000 130 9.57 0.37677
24758
2 0.188386 0.000989
955400 135 9.75 0.37677
25710
2 0.188386 0.000989
785000 140 9.57 0.37677
26662
2 0.188386 0.000989
436000 150 9.57 0.37677
28566
2 0.188386 0.000989
333000 150 9.57 0.37677
28566
2 0.188386 0.000989
157000 165 9.57 0.37677
31423
2 0.188386 0.000989
131000 170 9.57 0.37677
32375
2 0.188386 0.000989
130000 175 9.57 0.37677
33327
2 0.188386 0.000989
101000 180 9.57 0.37677
34280
2 0.188386 0.000989
94000 185 9.57 0.37677
35232
2 0.188386 0.000989
93000 185 9.57 0.37677
35232
2 0.188386 0.000989
92000 190 9.57 0.37677
36184
2 0.188386 0.000989
90000 190 9.57 0.37677
36184
2 0.188386 0.000989
83000 195 9.57 0.37677
37136
2 0.188386 0.000989
58000 200 9.57 0.37677
38089
2 0.188386 0.000989
37000 205 9.57 0.37677
39041
2 0.188386 0.000989
37000 205 9.57 0.37677
39041
2 0.188386 0.000989
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37000 205 9.57 0.37677
39041
2 0.188386 0.000989
S-N Diagram
45000
40000
35000
30000
max stress
25000
20000
15000
10000
5000
0
0 200000 400000 600000 800000 1000000 1200000 1400000
# of cycles
S-N Diagram for Cold Worked Aluminum
**fatigue limit = 25000 psi
For Cold Worked Steel:
P a g e | 10
D = 9.57 mm = 0.3768 inch
C = D/2 = 0.3768 /2 = 0.18883858 inch
π D4
I = 64
π 0.3768 4
= =9.895∗10 inch4
−4
64
M C
σxaM =
I
=( 240 *0.1883858 ) / 0.000989595
= 45687.975psi
For Cold Worked Aluminum
D = 9.57 mm = 0.376771654 inch
C = D/2 = 0.376771654 /2 = 0.1884 inch
π D4
I = 64
π 0.3768 4
= =9.895∗10 inch4
−4
64
M C
σxaM =
I
= ( 130 *0.1883858 ) / 0.000989595
= 24751.8949 psi
Discussion
P a g e | 11
-Cold Worked Steel, in general, has a higher resistance against cyclic stresses when
compared to Cold Worked Aluminum.
-The fatigue limit for metals is related to their tensile strength. For steels
the endurance limit is about one half their tensile strength. Although
many metals, especially steels, have a definite fatigue limit, other metals
do not have such limit, and the S-N diagram continues
Conclusion:
- Fatigue is a common type of catastrophic failure in which the applied stress level
fluctuates with time; it occurs when the maximum stress level may be considerably
lower than the static tensile or yield strength
-For many metals and alloys, stress decreases continuously with increasing number of
cycles at failure; fatigue strength and fatigue life are parameters used to characterize
the fatigue behavior of these materials.
-Fatigue cracks normally nucleate on the surface of a component at some point of
stress concentration
-Purpose of fatigue test is to determine the lifespan that may be expected from a material
subjected to cyclic loading
-A fatigue test is also used for the determination of the maximum load that a sample can
withstand for a specified number of cycles.
-The fatigue test will take long time as many specimens must be broken in order to collect
enough data.
-The fatigue limit for metals is related to their tensile strength.
References :
Manual lab martial
https://www.azom.com/materials-equipment.aspx?cat=47
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