Fatigue occurs when a material is subjected to repeated cyclic stresses that cause cracks to form over time even when the stresses are much lower than the material's strength. The document discusses various types of fatigue loading and summarizes key concepts like fatigue life diagrams, factors that influence fatigue crack growth rates, and methods for analyzing fatigue failure. It provides examples of calculating stress levels to avoid fatigue failure based on a given number of cycles.
Fatigue is important as it is the largest cause of failure in metals, estimated to comprise approximately 90% of all metallic failures; polymers and ceramics are also susceptible to this type of failure.
This presentation is by Flt Lt Dinesh Gupta, Associate Professor (Mechanical Engineering) NIET, Alwar (Rajasthan). It covers topic on Fluctuating Stresses related to Machine Design subject.
Fatigue is important as it is the largest cause of failure in metals, estimated to comprise approximately 90% of all metallic failures; polymers and ceramics are also susceptible to this type of failure.
This presentation is by Flt Lt Dinesh Gupta, Associate Professor (Mechanical Engineering) NIET, Alwar (Rajasthan). It covers topic on Fluctuating Stresses related to Machine Design subject.
Mumbai University.
Mechanical Engineering
SEM III
Material Technology
Module 2.2
Fatigue Failure:
Definition of fatigue and significance of cyclic stress, Mechanism of fatigue and theories of fatigue failure, Fatigue testing, Test data presentation and statistical evolution, S-N Curve and its interpretation, Influence of important factors on fatigue, Notch effect, surface effect, Effect of pre-stressing, corrosion fatigue, Thermal fatigue.
This PPT discusses Fatigue and Fracture mechanism, some history and problems. It has included on research paper. You can refer the literature review for further study of the topic.
CROSS-CORRELATION OF STRESSES IN THE TRAN REINFORCEMENT UNDER SHEAR LOAD AND ...IAEME Publication
The main aim of the present study is to give an answer to the question whether the transverse reinforcement, which is required for the shear resistance of columns, must be added to the one required for the cross section confinement, or it is possible for one to substitute the other. The superposition of these reinforcements is defended by the fact that the shear reinforcement results from the shear action, while the transverse reinforcement, required by the confinement, results from the axial compression of the section. The present study is experimental and uses strain gauges, in order to check the stresses of the transverse reinforcement. Useful conclusions are drawn.
Mumbai University.
Mechanical Engineering
SEM III
Material Technology
Module 2.2
Fatigue Failure:
Definition of fatigue and significance of cyclic stress, Mechanism of fatigue and theories of fatigue failure, Fatigue testing, Test data presentation and statistical evolution, S-N Curve and its interpretation, Influence of important factors on fatigue, Notch effect, surface effect, Effect of pre-stressing, corrosion fatigue, Thermal fatigue.
This PPT discusses Fatigue and Fracture mechanism, some history and problems. It has included on research paper. You can refer the literature review for further study of the topic.
CROSS-CORRELATION OF STRESSES IN THE TRAN REINFORCEMENT UNDER SHEAR LOAD AND ...IAEME Publication
The main aim of the present study is to give an answer to the question whether the transverse reinforcement, which is required for the shear resistance of columns, must be added to the one required for the cross section confinement, or it is possible for one to substitute the other. The superposition of these reinforcements is defended by the fact that the shear reinforcement results from the shear action, while the transverse reinforcement, required by the confinement, results from the axial compression of the section. The present study is experimental and uses strain gauges, in order to check the stresses of the transverse reinforcement. Useful conclusions are drawn.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
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Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Student information management system project report ii.pdfKamal Acharya
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Design and Analysis of Algorithms-DP,Backtracking,Graphs,B&B
fatigue
1.
2. Fatigue / Introduction
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ By Hussein Ghanim HASAN (PhD. Student)
Fatigue was discovered when several
investigators noted that bridge and railroad
components were cracking when subjected
to repeated loading.
Fatigue is caused by repeated application of
stress to the metal. It is the failure of a
material by fracture when subjected to a
cyclic stress .
Fatigue occurring suddenly and without
warning. There is very little gross plastic
deformation associated with fatigue failure
and so is brittle like.
railroad
bridge
aircraft
3. Fatigue / Introduction
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
Fatigue is an important form of behaviour in all materials
including metals, plastics, rubber and concrete when rotating
and subjected to alternating stresses.
There are many other situations where fatigue failure will be
very dangerous.
Examples: door springs, aircraft wings are subjected to
repeated loads, oil and gas pipes are often subjected to static
loads will cause fatigue.
4. Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
Fatigue / DEFINITIONS
• A fatigue cycle is defined as the time between two successive max (or min) in
the stress. The number of fatigue cycles per second is defined as the cyclic
frequency.
𝑆 𝑚: mean stress
𝑆 𝑎 : Amplitude stress
R : ratio stress
5. Type of Fatigue loading
I. Completely reversed cycle of
stress:
Explains the type of fatigue
loading where a member is
subjected to opposite loads
alternately with a mean stress
(𝑆 𝑚) is zero.
For example bending of steel
wire continuously in other
direction leads to alternate
tensile and compressive stresses
on its surface layers and failure
fatigue.
(a) Completely reversed stress cycle
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
6. Type of Fatigue loading
ii. Repeated stress cycles:
where a member is subjected to
only tension but to various
degrees.
For example: A spring subjected to
repeated tension as in a toy would
lead to fatigue failure.
(b) repeated stress cycle
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
7. Type of Fatigue loading
iii. Irregular or random stress
cycle:
This type of fatigue loading
where a member could be
subjected to irregular loads just as
in the case of aircraft wings
subjected to wind loads.
(c) random stress cycle
i.e. if the load changes from one magnitude to another the load is said to be
fluctuating load. (the direction does not necessarily change)
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
8. Cyclic Stress-Strain Behavior
Consider a stress-strain response curve
from a fatigue test of a specimen as
shown, When the strain is increased from
0 to Ԑ max , the stress is also increased
from 0 to σmax.
Then, when we unload the specimen
from the strain Ԑmax to Ԑmin the stress-
strain curve follows the unloaded line,
and the stress is decreased from σ max to
σ min. Finally, if we reload the specimen
from Ԑ min to Ԑ max , the stress is
increased from σ min to σ max by
following the reload curve.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
9. Fatigue failure
The crack is developed from a small flaw until it reaches the
critical size.
It is usually developed at high stress gradient area. The stress
gradient becomes larger and larger, and the crack progresses
more rapidly.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
10. Fatigue Crack Propagation
Normally, Crack propagation can be caused by cyclic
loading. Typical constant amplitude crack propagation as
shown in Fig
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
11. Fatigue Crack Propagation
The crack propagation rate
𝑑𝑎
𝑑𝑁
versus stress
intensity range ∆𝑘
Region i : Crack growth rate is slow and its
behavior is associated with fatigue crack growth
edge value Δk below which the crack growth is
negligible.
Region II: The relationship between log
𝑑𝑎
𝑑𝑁
versus
logΔk is linear and steeper than the curve in Region I.
This is due to unstable crack growth of the test
specimen.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
12. Fatigue Crack Propagation
Region III: The crack growth rate is very high and
little fatigue life is involved.
The relationship in this line is
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
The value of m is important since it indicates the degree of
sensitivity of the growth rate of the stress.
13. Fatigue - Failures
m
KC
dN
da
if we integrate between the initial size of a crack (𝑎 𝑜) and
the crack size required for fracture to occur (𝑎 𝑓), we find
that the number of cycles to failure is given by
From the steady state crack growth relationship of
Y = dimensionless geometric constant that varies depending on the
geometry of the crack, but usually taken as 1.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
14. Example I
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
to
15. Example I
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
16. “S-N” curve is mean the
amplitude stress versus cycles to
failure, which when plotted using
the stress amplitude on the
vertical axis and the number of
cycle to failure on the horizontal
axis.
S - N Diagram and Stress Life Relation
S-N curve is A very useful way to visual the failure for a specific
material with the S-N curve.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
17. S - N Diagram and Stress Life Relation
Se = endurance limit of the specimen (infinite life > 106
)
For (ferrous) materials exhibiting a knee in the S-N curve at 106
cycles.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
For most nonferrous metal such as aluminum, there have not endurance
limit and the S - N curve has a continuous slope. An endurance limit for
these materials is taken on the stress value corresponding to 5×108
cycles.
Sf = fatigue strength of the specimen (infinite life > 5x 108
)
18. Fatigue Strength Diagram
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
Mean Stress Correction for Endurance Limit
19. Modified Goodman Diagram
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ By Hussein Ghanim HASAN (PhD. Student)
Mean stress
Alternating
stress
m
a
Sut
Goodman line
Sy
Yield line
Sy
Se
Safe zone
C
20. Factors Affecting the Fatigue Crack Growth
Stress ratio effect
The increasing of R ratio will lead to increase a crack growth
rate.
Frequency effect
At normal environmental condition, frequency has little effect
on fatigue life for metallic structure. However, the growth rate
will be significantly affected if under an adverse environment.
Temperature effect
Fatigue life will be reduced if the temperature is increased.
Surface Roughness:
Smoothly polished specimens have higher fatigue strength.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
21. Example III
Where the magnitude of the stress varies from σ min =-0.6 σ max to max σ . The
shaft is made of stress-relieved, the ultimate stress of 830 MPa , yielding
stress of 660 MPa , the endurance limit of 410 MPa. Determine the magnitude
of max σ based on a factor of safety of 1.80 against the failure at 𝑁𝑓 =
107
cycles.
Since the steel is a ductile material, we will use the Gerber relation to determine the magnitude of σ max.
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ
23. Video about a Fatigue test
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ By Hussein Ghanim HASAN (PhD. Student)
Theory of Elasticity
CE-527
24. References
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ By Hussein Ghanim HASAN (PhD. Student)
Advanced mechanics of materials, Dr. Sittichai Seangatith. May
(2001)
Experimental Techniques In Materials And Mechanics, C.
Suryanarayana.(2011).
Modern Metal Fatigue Analysis, Draper John (2008)..
Fatigue Damage, Lalanne, C. (2009).
25. Fatigue / Discussion
Theory of Elasticity CE-527 (Fatigue) submitted to Dr. Nildem TAYŞİ By Hussein Ghanim HASAN (PhD. Student)
Thank You for
your attention