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Mechanical accidents, fatigue, erosion, corrosion, as well as environmental attacks, are issues that can lead to a crack in a mechanical structure. Cracks are indications of an impending mechanical failure. In view of the fact that the presence of a crack in a structure could lead to devastating results, investigating the structural integrity of pipes was an extremely active area of research in the last two decades. Mechanical structures in real service life are subjected to combined or separate effects of the dynamic load, temperature and corrosive medium, due to the consequent growth of fatigue cracks, cracks due to corrosion and other type damages. Although the theory and technology of non-destructive testing is highly enhanced, inspecting the integrity of a structure is a labour-intensive and protracted process that should only be carried out when truly needed. One approach for reducing inspection related shutdown time and cost is to provide a mechanism with an early warning failure device. Such a device monitors, online, crack-related irregularity in the behaviour of a system. If the device gives a sound signal that a crack is present, a message is given out to the operator to shutdown the machine and have it checked. For the development of such early warning devices, knowledge of the dynamics of cracked structures is important.
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SEMINAR PRESENTATIONON
CRACK DETECTION IN PIPES
UNDER THE GUIDANCE OF
MR. A. V. DEOKARPRESENTED BY
AKANSHA JHADEPARTMENT OF MECHANICAL ENGINEERING
AMRUTVAHINI COLLEGE OF ENGINEERING, SANGAMNER2011-2012
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MAIN POINTS TO BE DISCUSSEDINTRODUCTION
TYPES OF CRACK
CAUSES AND EFFECTS
METHODS OF CRACK DETECTION
NATURAL FREQUENCY BASED METHOD
CONCLUSION
BIBLIOGRAPHY
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INTRODUCTION TO CRACK
• Definition “Any deviation introduced to a structure, either deliberately or
unintentionally, which adversely affect the performance of the system.”
Damage Assessment
Four levels of damage assessment:
1. Determining the presence
2. Locating the damage
3. Quantifying the severity
4. Prediction of the remaining serviceability
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CAUSES OF CRACK EFFECTS OF CRACK
Mechanical Damage
Material Defects
Weld Cracks
Incomplete Fusion
Incomplete Penetration
Fatigue Cracks
External Or Internal Corrosion
Hydrogen Blistering
High production and
maintenance Cost
Leads to Catastrophic Failure
Operational Problem
Premature Failure
Affects the Industrial Economic Growth.
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1) Transverse cracks : Cracks perpendicular to the pipe axis are known as “transverse cracks”
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TYPES OF CRACK
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2) Longitudinal cracks: Cracks parallel to the pipe axis are known as “longitudinal cracks”.
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TYPES OF CRACK
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3) Slant cracks: cracks at an angle to the pipe axis are known as “Slant cracks”
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TYPES OF CRACK
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TYPES OF CRACK
4) Gaping cracks: Cracks that always remain open are known as “gaping cracks” or “notches”.
5)Surface cracks: Cracks that open on the surface are called “surface cracks”.
6)Subsurface cracks: Cracks that do not show on the surface are called “subsurface cracks”.
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CONVENTIONAL METHODS :
(Non- Destructive techniques)1. Pipeline injection gauze
2. Sewer scanner & evaluation technology
3. Automated pipe crack detection
4. Ultrasound acoustics based assessment technique
NON-CONVENTIONAL METHOD :• Natural Frequency
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METHODS OF CRACK DETECTION
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CONVENTIONAL METHODS
1) Pipeline Injection Gauze(PIG) :‘Smart’ and Intelligent inline inspection tools sent through the pipe via the circulation of fluid.
Fully automatic Data stored on solid state memoriesReliable in a hostile environmentCannot be supervised during a runThe inspection speed depends on the medium
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2) Sewer Scanner & Evaluation Technology(SSET) :
Technology for obtaining images of the interior of pipe
It can travel through the pipe at a uniform speed
Higher quality image data
Enables us to make critical rehabilitation decisions.
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CONVENTIONAL METHODS
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3) Automated Pipe Crack Detection :Successfully able to detect cracks in varying pipe backgrounds, colour, and crack patterns.
Better 2-D features from segmented crack images are available
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CONVENTIONAL METHODS
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DATA OF UNCRACKED PIPE(l=900 mm, di=16 mm, do=21 mm
EXPERIMENTAL DATA OF 1st PIPE(300 mm from one end for d=1 mm and d=2 mm)
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Analytical Experimental FE modelω1
(Hz) 146.9 147.50 146.54
ω2 (Hz) 404.98 399.63 401.69
ω3 (Hz) 793.95 786.75 787.17
Depth=1mm Depth=2mmω1
(Hz) 147.25 147.0
ω2 (Hz) 398.63 397.75
ω3 (Hz) 786.63 786.38
NATURAL FREQUENCY AS BASIC CRITERION
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NATURAL FREQUENCY AS BASIC CRITERION
x-coordinate : Normalized distance of the crack (x/l) where, x= crack location l=length of pipey-coordinate: Crack dimensions(d/w) where ,d= depth of crack w=width of pipez-coordinate: Natural frequency
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NATURAL FREQUENCY AS BASIC CRITERION
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NATURAL FREQUENCY AS BASIC CRITERION
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NATURAL FREQUENCY AS BASIC CRITERION
FE results Experimentalω1
(Hz) 1084.2 1083.5
ω2 (Hz) 1413.0 1411.1
ω3 (Hz) 1659.4 1658.1
DATA OF UNCRACKED PIPE(l=650 mm, do =104.5 mm, di=112.5 mm
EXPERIMENTAL DATA OF 2nd PIPE(325 mm from one end for d=1.5 mm)
depth=1.5mmω1
(Hz) 1077.6
ω2 (Hz) 1412.0
ω3 (Hz) 1652.3
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NATURAL FREQUENCY AS BASIC CRITERION
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Significant changes in natural frequencies of the vibrating pipes are observed at the vicinity of crack location.
With the increase in crack depth, the natural frequency of the pipe decreases
The less is the wall thickness, less is the computational effort
This method is promising and can be used over a large-scale ,compared to other NDE techniques.
CONCLUSION:
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“Material Science And Metallurgy”; V.D.Kodgire and S.V Kodgire; Everest Publishing House; 25th Edition.
“Crack Location In Pipes Using Modal Frequencies And Fem”; M.J. Mahboob, A. Marzban and A.Shahsavri; The 11th International Conference On Vibration Engineering, Timissoara, Romania, 2005.
“Crack Detection In Aluminum Structures”; Brad A. Butrym, M.S. Thesis; Virginia Polytechnic Institute And State University; 2010.
“Vibration Analysis Of Cracked Beam”; Prabhakar M.S, Thesis Of M. Tech; National Institute Of Technology, Rourkela; 2009.
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QUESTIONS?
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THANK YOU
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