DEVELOPMENT OF FATIGUE TESTING TECHNOLOGY FOR A FATIGUE ISSUE (Case Study of The Crash of China Airlines Flight 611)

1. DEVELOPMENT OF FATIGUE TESTING
TECHNOLOGY FOR A FATIGUE ISSUE
H a r b i n E n g i n e e r i n g U n i v e r s i t y
Student: Abdul Majid
Student Number: S32002006W
Major: Civil and Structural Engineering
Shattered in Seconds: The Crash of China Airlines
Flight 611

2. 01 Introduction
Fatigue in Airplanes
Traditional Test Method
Advanced Tests
Materials for Test
CONTENTS
02
03
04
05
2
Case Study
06
07 Conclusion

3. Part.1
Introduction
3

4. This presentation will explore the history of fatigue testing
technology, current methods and techniques, and future advancements
in the field.
We will also discuss how this technology can be used to address real-
world fatigue issues and improve the safety and reliability of structures
and materials.
4
Introduction Scope &
Objective
Methodology Conclusion
Progress

5. Fatigue
Fatigue: Fatigue is a common failure mode in engineering and materials
science, where repeated loading and unloading of a structure or material can
lead to progressive damage and ultimately, failure. Fatigue failures can
occur at stress levels significantly lower than the yield or ultimate strength
of a material and are often difficult to predict.
Fatigue Testing Technology: Fatigue testing technology is used to assess the
fatigue resistance of materials and structures under various loading
conditions. The objective of fatigue testing is to determine the number of
loading cycles that a material or structure can withstand before it fails. The
results of fatigue testing can be used to estimate the expected lifespan of a
material or structure and to determine the appropriate design parameters to
prevent fatigue failure.
5
Introduction Scope &
Objective
Methodology Conclusion
Progress

6. Why Fatigue Testing is Important for Ensuring the Safety and
Reliability of Materials and Structures, Especially in Industries
Like Aerospace and Automotive
Fatigue testing is important for ensuring the safety and reliability of
materials and structures in industries like aerospace and automotive
because it allows for the identification of potential fatigue failure
points and enables the determination of the fatigue limit of a material.
This information is critical for the design and construction of durable
and safe components, which can prevent catastrophic failures and
ensure the longevity of the structure or system.
6
Introduction Scope &
Objective
Methodology Conclusion
Progress

7. Traditional Fatigue Testing Methods
Fatigue testing is used to determine the durability and strength of
materials under cyclic loading.
Traditional methods of fatigue testing include axial, bending, torsion,
and combined loading.
Axial loading involves applying a constant load in one direction,
while bending loading applies a cyclic load perpendicular to the long
axis of the sample. Torsion loading applies a twisting force to the
sample, while combined loading applies two or more of these types of
loading simultaneously to simulate real-world conditions.
7
Introduction Scope &
Objective
Methodology Conclusion
Progress

8. Advanced Fatigue Testing Methods
Advanced fatigue testing methods such as high-cycle fatigue, low-
cycle fatigue, and very-high-cycle fatigue testing have been developed
in recent years to better understand the behavior of materials and
components under different loading conditions.
These methods provide unique insights into the fatigue behavior of
materials and are used to test materials in applications where they
experience high or low frequency, high or low amplitude loading
conditions. By using a combination of these testing methods,
researchers and engineers can develop more reliable and durable
products.
8
Introduction Scope &
Objective
Methodology Conclusion
Progress

9. Materials for Fatigue Testing
Metals, polymers, and composites are commonly used for fatigue testing due to
their widespread use in various applications. Composites present unique
challenges due to their complex behavior, while polymers and metals are more
straightforward to test. Choosing materials that accurately represent the materials
used in the actual application is important for effective fatigue testing.
The properties of materials used for fatigue testing, such as their microstructure,
grain size, and composition, can greatly affect the results of the testing. For
example, materials with larger grain sizes are more susceptible to crack initiation
and propagation, which can affect the fatigue life of the material. The composition
of a material can also have a significant impact on its fatigue behavior, as different
materials may have different strengths, stiffness, and resistance to crack growth.
Understanding the properties of the materials being tested is essential for accurate
and meaningful fatigue testing results.
9
Introduction Scope &
Objective
Methodology Conclusion
Progress

10. Part.2
Ca s e Study
Shattered in Seconds: The Crash of
China Airlines Flight 611
10

11. Shattered in Seconds: The Crash of China Airlines Flight
611
China Airlines Flight 611 was a scheduled international passenger
flight from Taipei, Taiwan to Hong Kong. On May 25, 2002, the
aircraft serving the route, a Boeing 747-209B, disintegrated in mid-air
and crashed into the Taiwan Strait, just 20 minutes after taking off
killing all 225 passengers and crew on board. The investigation into
the crash revealed that it was caused by metal fatigue in the aircraft's
structure, specifically the improper repairs made to the rear bulkhead
after a tail strike incident in 1980.
11
Introduction Scope &
Objective
Methodology Conclusion
Progress

12. Passengers
The passengers included a former legislator and two reporters from
the United Daily News. All of the passengers on board were ethnic
Chinese except the passenger from Switzerland. 114 of the passengers
were members of a group tour to Hong Kong organized by five travel
agencies.
12
Introduction Scope &
Objective
Methodology Conclusion
Progress
Nationality Passengers Crew Total
Taiwan 190 19 209
China 9 0 9
Hong Kong 5 0 5
Singapore 1 0 1
Switzerland 1 0 1
Total 206 19 225

13. Metal fatigue
In February 1980, 20 years previous, the aircraft had operating flight
CI 009 from Stockholm Arlanda Airport (ARN) to Taoyuan
International Airport (TPE) via Jeddah and Hong Kong when it
suffered a tail strike. On landing at Kai Tak Airport (demolished,
formerly HKG), one of its two stops on this route, the plane's tail had
scraped along the runway.
Instead of carrying out proper maintenance on the aircraft, the China
Airlines engineering team simply installed a doubler over the damaged
part of the aircraft. This was not sufficient according to Boeing's
Structural Repair Manual (SRM). The constant use of the aircraft had
enlarged the crack within the aircraft, which eventually led to the
aircraft breaking up midair two whole decades later.
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Introduction Scope &
Objective
Methodology Conclusion
Progress

14. Metal fatigue
14
Introduction Scope &
Objective
Methodology Conclusion
Progress
Around 1995, China Airlines started
to ban smoking on board. Cabin
pressurization forced the smoke out
through the cracks. Overtime, the
smoke left the nicotine stains outside
of the plane. These stains were an
indication of a possible hidden cracks
beneath the doubler plate, which
means that the cracks had been there
long before 1995.

15. Metal fatigue
15
Introduction Scope &
Objective
Methodology Conclusion
Progress
B-18255 seat-plan:
Empty seat Not Recovered Recovered Galley
Storage
Toilet Stairs

16. Metal fatigue
16
Introduction Scope &
Objective
Methodology Conclusion
Progress

17. Aircraft Fatigue
17
Introduction Scope &
Objective
Methodology Conclusion
Progress

18. Aircraft Fatigue
The potential for aircraft fatigue and structural failure is something that
anyone in the aircraft industry is familiar with. Aircraft undergo rigorous
testing before they can be considered safe and certified for flight to ensure
that they can operate how they need to.
According to Boeing, equipment failure, which includes structural failures,
only accounts for about 20% of accidents in today’s aircraft. We’ve come a
long way from early flying machines, where nearly 80% of accidents were
related to some kind of mechanical or structural failure.
Still, since safety is at stake, metal fatigue and failure is something that
must be considered with every maintenance inspection. Let’s take a look at
what fatigue and metal failure are and how they can be prevented.
18
Introduction Scope &
Objective
Methodology Conclusion
Progress

19. WHAT IS METAL FATIGUE IN AIRCRAFT?
Fatigue is a common occurrence among all metal airframes. Due to
the repeated flight cycles and frequent use, the metal elements of
planes become weakened over time, and they will eventually require
attention and repair.
This weakness manifests in cracks, which are microscopic at first.
With continued aircraft use over time, though, the cracks grow larger
and eventually become visible. An aircraft begins to age after its first
flight, and the effects of corrosion and fatigue occur almost
immediately. Aging becomes an issue when the aircraft can no longer
be effectively repaired or sustain the rigors of flight.
19
Introduction Scope &
Objective
Methodology Conclusion
Progress

20. WHAT IS METAL FATIGUE IN AIRCRAFT?
The signs of fatigue are more pronounced in aging aircraft and
become more dangerous as the aircraft is continually exposed to
atmospheric pressure. Because of this, after a certain number of flight
cycles — a number calculated by manufacturers to ensure safety — an
aircraft should be retired. This regulation is meant to prevent
catastrophic failure.
Accumulating fatigue damage is an inevitable reality of flying metal
airframes. Atmospheric pressure, G-loads, turbulence and other factors
create the perfect environment for damaging stress. However,
technicians and manufacturers can lengthen the longevity of an aircraft
through routine maintenance and inspection.
20
Introduction Scope &
Objective
Methodology Conclusion
Progress

21. WHAT IS FATIGUE FAILURE?
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Methodology Conclusion
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22. The Fatigue Issue
One specific example of a fatigue issue in the aerospace industry is
the development of fatigue cracks in critical structural components of
an aircraft, such as wing spars, engine mounts, and landing gear.
These components are subjected to cyclic loading during flight, and
the accumulation of damage from repeated cycles can result in the
formation and propagation of fatigue cracks. If left undetected, these
cracks can eventually lead to catastrophic failure.
22
Introduction Scope &
Objective
Methodology Conclusion
Progress

23. WHAT IS FATIGUE FAILURE?
While aircraft fatigue is dangerous if not cared for, it doesn’t
necessarily put a plane out of commission at first occurrence.
However, aging — which leads to a combination of corrosion and
fatigue — is the leading cause of cracks in the metal elements of an
aircraft.
Structural failure occurs when aircraft fatigue is not detected early
enough or is left untended. Since most fatigue cracks are invisible to
the eye initially, it makes them particularly challenging to detect.
23
Introduction Scope &
Objective
Methodology Conclusion
Progress

24. WHAT IS FATIGUE FAILURE?
These cracks are what directly cause large-scale damage and danger.
If an aircraft is continually utilized without proper fatigue inspection
and maintenance, the microscopic-level damage can become visible
cracks in the aircraft’s body and split wider after exposure to the flight
environment. If left to widen or worsen, the results can be
catastrophic. Parts of the aircraft may fracture and break off, or the
aircraft’s skin might peel off during flight.
The danger lies in how quickly fatigue can progress to failure. While
aircraft fatigue is a natural part of flight, both visible cracks and cracks
invisible to the eye mean failure is a real possibility.
24
Introduction Scope &
Objective
Methodology Conclusion
Progress

25. WHY DOES AIRCRAFT FATIGUE OCCUR?
Much like any metal vehicle, heavy use and wear weaken aircraft over
long periods. Any time an aircraft is flown, it endures fatigue.
Pressure is the main cause of weakened metal components. Outside
exposure from straight-and-level flight, turning, accelerating,
decelerating and other maneuvers create repeated changes in the
loading of the wings and other surfaces. Also, with the regular
pressurization and depressurization of flying at high altitudes, the
metal skin of an aircraft expands and contracts. Each cycle begins at
the time of lift-off and ends after landing.
25
Introduction Scope &
Objective
Methodology Conclusion
Progress

26. WHY DOES AIRCRAFT FATIGUE OCCUR?
As metal is bent from its original shape and re-bent back, it becomes
weaker at every hinge or site of expansion. This principle applies to all
scenarios involving metal, even on the scale of bending a soda can tab
back and forth. Eventually, the aluminum weakens and breaks off at
the bend.
The same weakening and breaking eventually happens to aircraft skins
and other metal components when they are exposed to various flight
conditions.
26
Introduction Scope &
Objective
Methodology Conclusion
Progress

27. HOW FATIGUE CRACKS BEGIN
Fatigue cracks mainly originate in three different areas:
Internally, in load-bearing structural elements, potentially developing
small points under high stress.
Externally, in load-bearing aircraft skins, in the case that the skin is
under pressure from a structural load.
Around the edges of fastener holes, such as those for rivets, bolts or
screws, or in any similar area of concentrated stress.
27
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Methodology Conclusion
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28. HOW FATIGUE CRACKS BEGIN
These areas of high pressure are more prone to premature cracking
and exhibiting early signs of fatigue. In the same right, they are often
the areas recorded as the original sites of failure.
Large components moving at high speeds, such as engines, are also
prone to cracking. Adding fast motion to already high stress levels
creates an environment susceptible to damage, which is likely to
progress to structural failure sooner than unmoving elements.
Aircraft undergo immense amounts of stress each time they fly, and
they are not exempt from the effects of aging. Aging planes — those
that have endured many miles of flight time — accumulate extensive
wear and fatigue, creating a need for heavy monitoring and inspection.
28
Introduction Scope &
Objective
Methodology Conclusion
Progress

29. AIRCRAFT FATIGUE TESTING AND REGULATIONS
29
Introduction Scope &
Objective
Methodology Conclusion
Progress

30. AIRCRAFT FATIGUE TESTING AND REGULATIONS
30
Introduction Scope &
Objective
Methodology Conclusion
Progress
While accurate methods of testing for aircraft fatigue are relatively new, there is a way to
determine the amount of time an aircraft or particular metal has before fatigue causes
severe damage.
To determine how many cycles an aircraft or type of metal can take, there has to be a
measurable factor with which to make a comparison. This factor is called the Limit of
Validity, or LOV.
The LOV is the time period — defined in hours, the number of flight cycles or both — an
aircraft frame can withstand before it experiences structural failure or widespread fatigue
damage (WFD). The manufacturer determines the LOV based on evidence gathered
through various methods of fatigue testing, such as full-scale fatigue and component tests,
less than full-scale tests, disassembly and refurbishment of an aged aircraft and fleet-
proven statistics. Using the LOV helps to avoid aircraft fatigue at the microscopic level.
Measuring against the determined LOV is not only crucial for safety, but it is also an FAA
regulation. Effective as of 2011, the FAA requires all aircraft manufacturers and operators
to report the LOV levels of active aircraft on a set schedule, and they may not fly beyond
the LOV unless an extended one is approved.

31. AIRCRAFT FATIGUE TESTING AND REGULATIONS
31
Introduction Scope &
Objective
Methodology Conclusion
Progress
By maintaining this requirement, the FAA can ensure that documented
aging aircraft are retired prior to experiencing any catastrophic failures.
In addition to LOV measurements, the FAA issues airworthiness directives
(ADs). These require manufacturers to complete necessary work on any
aircraft, engine, propeller or component exhibiting or having the potential to
develop unsafe conditions.
If an AD for a particular aircraft has not been complied with, the aircraft is
not airworthy — which means it shouldn’t be flying. Airworthiness in itself
is a regulation. An aircraft must have an airworthiness certificate for it to be
operated legally — and safely. An airworthiness certificate is issued by the
FAA and can either be a standard certificate or a special certificate.

32. Standards and Regulations
ASTM and ISO are organizations that develop standards for fatigue
testing, which provide guidelines for testing procedures,
instrumentation, and data analysis. Compliance with these standards is
often required for regulatory approval of products in various
industries, ensuring the safety and reliability of products and
preventing failure due to fatigue.
The standards developed by ASTM and ISO provide guidelines for
conducting fatigue testing, which ensures consistency and reliability in
testing results. By adhering to these standards, testing laboratories can
produce accurate and comparable results, and regulatory bodies can
ensure the safety and reliability of products.
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Methodology Conclusion
Progress

33. HOW TO PREVENT AIRCRAFT FATIGUE FAILURE
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Methodology Conclusion
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34. HOW TO PREVENT AIRCRAFT FATIGUE FAILURE
34
Introduction Scope &
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Methodology Conclusion
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By upholding these requirements, aircraft have a better chance of
remaining safe and in-use for longer periods of time.
Inspectors may also use non-destructive testing (NDT) methods to
find points of fatigue, which are the least invasive methods.
NDT involves inspecting metal elements for inconsistencies or
damage without destroying the element in question. This testing may
include the use of ultrasound, X-ray scattering, X-ray absorption,
electrical eddy currents, magnetic particles, liquid penetrants and
optics.
Each test has its own specific purpose and method:

35. HOW TO PREVENT AIRCRAFT FATIGUE FAILURE
35
Introduction Scope &
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Methodology Conclusion
Progress
Ultrasound: Through an ultrasound device, high-voltage electrical pulses
are converted into high-frequency ultrasonic energy. When an ultrasonic
wave hits a defect, it bounces back — which enables the inspector to see the
depth and true size of flaws under the surface.
Eddy currents: A coil sends an electromagnetic field through a metal
surface, producing a loop pattern. Defects will distort the pattern, which is
captured and analyzed by a recording instrument. Technicians are then able
to review the created pattern, seeing defects on and beneath the surface.
Liquid penetrants: Colored liquid applied to a metal’s surface fills small
defects and blemishes. Through the use of colored dye or UV light, these
imperfections become visible to the naked eye.
Magnetic particles: Inspectors apply and draw fine, ferromagnetic
particles into a metal’s surface and defects, making them visible. However,
this method only works on ferromagnetic elements.

36. Part.3
Conclusions
36

37. Conclusion
This presentation covered traditional and advanced methods of fatigue
testing, materials used, instrumentation, and standards. An example
was given, and recent advances in technology were discussed. Overall,
the presentation focused on the development of fatigue testing
technology for a fatigue issue.
Fatigue testing technology plays a crucial role in ensuring the safety
and reliability of materials and structures. By accurately predicting
fatigue behavior and identifying potential failure points, it can prevent
catastrophic failures and save lives. Continued advances in fatigue
testing technology will only increase its importance in industries such
as aerospace, automotive, and construction.
37
Introduction Scope &
Objective
Methodology
Progress Conclusion

38. Part.5
References
38

39. References
 [1] J. Schijve, Fatigue of structures and materials. Kluwer, 2001.
 [2] D. Rhodes, “Fatigue crack growth in aircraft aluminum alloys,” Ph.D. dissertation, Imperial College of
Science & Technology, London, England, 1981.
 [3] T. A.J., “33 years of aircraft fatigue,” in Proceedings of the 10th ICAF Symposium, Brussels, Belgium,
1979.
 [4] J. Schijve, “Fatigue damage in aircraft structures, not wanted, but tolerated?” International Journal of
Fatigue, vol. 31, no. 6, pp. 998–1011, 2009.
 [5] W. D. Pilkey and R. E. Peterson, Peterson’s stress concentration factors.Wiley, 1973.
 [6] R. J. H. Wanhill, “Fatigue requirements for aircraft structures,” in Aerospace Materials and Material
Technologies : Volume 2: Aerospace Material Technologies. Springer Singapore, 2017, pp. 331–352.
 [7] L. Molent and S. Barter, “A comparison of crack growth behaviour in several full-scale airframe fatigue
tests.,” International Journal of Fatigue, vol. 29, no. 6, pp. 1090–1099, 2007.
 [8] M. Guillaume, A. Uebersax, G. Mandanis, and H. Cyril, “Structural integrity – yesterday – today –
tomorrow,” Advanced Materials Research, vol. 891-892, pp. 1053–1058, 2014.
 [9] L. Molent, “The history of structural fatigue testing at Fishermans Bend Australia, ”DSTO Air Vehicles
Division, Melbourne, Vic, Australia, Technical Report, 2005.
 [10] V.Wickramasinghe, C. Yong, and D. Zimcik, “Experimental evaluation of an advanced buffet suppression
system on full-scale F/A-18 fn,” Journal of Aircraft, vol. 44, pp. 733–740, 2007. 39
Test results
and discussion
References
Concrete Mix
Serviceability
Requirements
Conclusion

40. videoplayback.mp4
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41. Thank you
设计：Majid, Abdul 明哲 (S32002006W)
微信公众平台：哈尔滨工程大学学生在线
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