Transcript Auger Electron Spectroscopy AES

Non-destructive Evaluation
NDE
Dept. of Physics and Materials Science
City University of Hong Kong
References:
1.
H.E. Davis, G.E. Troxell, in chapter 16 of “The Testing of Engineering
Materials”, 1982.
2.
J.S. Ceurter et al., “Advanced Materials Processes” (April 2002), p.29-31.
3.
T. Adams, “Advanced Materials Processes” (April 2002), p.32-34.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
1
Various Purposes
• Locate defects (Why ?)
• Determine dimension, physical, or mechanical
characteristics
• Determine Residue Stress (XRD)
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
2
Advantage of Knowing the defects
• Defects are usually stress raiser
• Stress raiser can cause pre-mature failure
Over design to overcome pre-mature failure
Bulky/heavy design
• Catastrophic/sudden/unpredicted failure
loss of lives and money
• Quality control
• Better design
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
3
Better design (example)
Consider a rectangular bar 10mm x 5 mm which will be
used to support some load. The steel chosen had
yield strength, tensile strength and fracture
toughness being 600MPa, 900MPa and 40MPam. If
the corresponding design safety factors are 1.2, 1.6
and 1.5 respectively. What is the allowable load?
(a)Yielding failure (>25 kN)
(b)Tensile fracture (>28.1 kN)
(c)Fracture toughness (crack size dependant)2 mm:
16.8kN; 1mm: 23.6kN; 0.1mm: 75.2kN
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
4
Yield strength (plastic deformation)
area = 10 mm x 5 mm = 50 x 10-6 m2
max. load
= (yield strength x area)  safety factor
= (600MPa x 50 x 10-6 m2)  1.2
= 25 kN
(plastic deformation at load > 25 kN)
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
5
Tensile strength (Catastrophic failure)
area = 10 mm x 5 mm = 50 x 10-6 m2
max. load
= (tensile strength x area)  safety factor
= (900MPa x 50 x 10-6 m2)  1.6
= 28.1 kN
(tensile fracture at load > 28.1 kN)
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
6
Fracture Toughness
(require information of crack length)
KIC =   (a)
Assume geometric correction factor,  = 1
max = KIC /(a)
Max load
=  x A  (safety factor)
= KIC /(a) x A  (safety factor)
= 40MPam /(3.1416 x a) x 50 x 10-6 m2  (safety factor)
When a = 2 mm, max load = (2000  0.07927)/1.5 = 16.8 kN
When a = 1 mm, max load = (2000  0.05605)/1.5 = 23.6 kN
When a = 0.1 mm, max load = (2000  0.01772)/1.5 = 75.2 kN
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
7
NDE methods for location of defects
Internal defects detection
Surface defects
detection


Visual inspection
Liquid penetrant test
Magnetic particle
method



2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
Magnetic particle method
Radiographic methods
Electromagnetic methods

Eddy current method
Barkhausen Noise Inspection
Principle
Material defects (grinding damage,
re-tempering burn, Rehardening burn, residue
stresses
Acoustic methods
8
Visual inspection
 It should never be omitted.
 Use low-power magnifying glass or microscopes
(remember to take permanent photographic record)
 Surface roughness:
Touch inspection using finger along the surface (2-3 cm/s.)
Light reflection method
No-parallex method
 Penetrant test
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
9
Penetrant test
 Suitable for locating surface discontinuities, such as cracks,
seams, laps, laminations in non-porous materials.
 Applicable to in-process, final, and maintenance inspection.
 ASTM E 165
General procedure:
 Thoroughly clean the surface
 Apply penetrant on the surface
 Liquid penetrant enter small openings by capillary
action
 Remove liquid completely and apply developer (dry or
wet)
 The penetant bleed out onto the surface showing the
location of the surface defect
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
10
Enhancing the penetrant test
 Strike the part to force the liquid out of the defect
 Fluorescent-penetant
depth of surface defects may be correlated with the
richness of color and speed of bleed out
 Filtered-particle inspection:
-This method depends on the unequal absorption into a
porous surface of a liquid containing fine particles in
suspension.
-Preferential absorption causes the fine particles in the
solution to be filtered out and concentrated directly over
the crack, producing a visual indication.
 Cracks on Non-conducting materials:
-A cloud of fine electrically charged particle is blown over
the surface, causing a buildup of powder at the defect.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
11
Magnetic Particle Test
 Use to locate the defects at or near the surface of ferromagnetic
objects.
 The magnetic particles tends to pile up and bridge over
discontinuities.
 A surface crack is indicated by a line of the fine particle following
the outline of the crack.
 A subsurface defect by a fuzzy collection of the fine particles on the
surface near the defect.
 Fatigue crack in an airplane gear.
 Orientation of cracks
 Some cracks are more difficult to detect.
 DC current is often employed, since it permit deeper defects
detection.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
12
Permanent magnets with soft iron
keepers
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
13
Fixture for yoke induction of
longitudinal magnetic field
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
14
Leakage Flux
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
15
Fatigue cracks in
airplane gear
detected by the
magnetic-particle
method
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
16
Orientation of magnetic fields
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
17
Some cracks are more difficult to detect
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
18
Threshold indications of near-surface
cavities
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
19
Radiographic methods
•
•
•
•
X-rays method (Exograph)
Gamma rays (Gammagraph)
Neutron
Infra-red (FT-IR) imaging
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
20
X-ray method (ASTM E 94)
 High energy photon (short wavelength, high frequency) can
penetrate materials better
 Formation of the radiograph
 X-ray source
 Arrangement for radio graphing a welded joint
 Xeroradiography: static electricity, fine powders, specially coated Al plate, image
available in seconds





On-line Soft X-ray scanning: low energy X-ray
Influence of size of source and sharpness of image
Interpretation of the radiograph: (e.g. Radiograph of a 20 mm weld)
Quality of image
Safety (Biology effect)
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
21
Formation of a radiograph
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
22
X-ray source
• X-ray method (seconds/minutes) is faster than
gamma-ray method (hours)
• The quality of the image depends on the
stability of the high voltage electron tube and
the penetration power of the x-ray.
• Industrial units (40-400kV)
• High resolution system (30-150kV)
• High energy system (>400kV)
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
23
Radio graphing a welding joint
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
24
Interpretation of Radiographs
 Contrast due to difference in thickness, density, composition.
 Gas cavities and blowholes are indicated by well defined circular dark
areas.
 Shrinkage porosity appears as fibrous irregular dark region having an
indistinct outline.
 Cracks appear as darkened areas of variable width.
 Sand inclusions are represented by gray or black spots of an uneven or
granular texture with indistinct boundaries.
 Inclusions in steel castings appear as dark areas of definite outline. In light
alloys the inclusion may be more dense than the base metal and thus
cause light areas.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
25
Influence
of size of
source on
sharpness
of image
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
26
Radiograph of a 20 mm weld
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
27
Quality of image
• The absorption increase rapidly with the
thickness exponentially
• The longer the wavelength, the greater the
absorption.
• Penetrameter: a calibration device helps in
determining the smallest detectable defect
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
28
Radiation Monitoring and Safety
 Observe the rules, regulation and monitoring measures set by the
local and international nuclear and radiation monitoring bodies.
 Be EXTREMELY careful, don’t perform this in a rush.
 Once the operation manual have been set, the engineers and
technicians must follow it STRICTLY.
 Don’t make arbitrary compromise.
 Get advices from the licensed radiographers.
 Select appropriate personal monitoring devices.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
29
Biological Effects
• Relaxation lengths of various shielding
materials.
• Estimated radiation does to U.S. population
• Acute doses of penetration radiation.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
30
Relaxation lengths of various shielding
materials
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
31
Estimated radiation does to U.S.
population
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
32
Acute doses of penetration radiation.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
33
a
b
Neutron
Radiography
a.
b.
c
d
c.
d.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
Brass bullet with
gunpowder
Steel airbag
inflator with
packets of fastburn pyrotechnic
38 mm long
turbine blade
Turbine blade
with flaw
34
FT-IR imaging
Inclusion in polypropylene film
Red: amide
Red: ester
2015/7/17
IR spectra showing impurities (1)
ester and (2) amide.
Dr.
Jonathan C.Y. Chung: NDE
35
Perkin-Elmer FT-IR
imaging system
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
36
FT-IR imaging
An image a fly’s wing
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
37
Fingerprint image
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
38
PCB sample
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
39
Electromagnetic methods
• Magnetic measurement is sensitive to
chemical composition, structure, internal
strains, temperature and dimensions.
• Limitations:
– Magnetic properties cannot be simply related to
the mechanical properties
– Sensitive to internal strains and temperature. This
is more significant when high frequencies or low
magnetizing forces are employed.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
40
Encircling Coils
If the test coil
moved over a
crack or defect in
a metal plate, at a
constant
clearance speed,
a momentary
change will occur
in coil reactance
and coil current.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
41
Effect of similar inner and outer defects
on flux pattern and measurement
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
42
Barkhausen Noise Inspection
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
43
Barkhausen Noise (Principle)
 Magnetizing field causes the materials undergo a
magnetization change in ferromagnetic material
 This change is a result of the microscopic motions of magnetic
domain walls within the metal.
 Domain wall movement emit electrical pulse that can be
detected by a coil of conducting wire.
 These discrete pulses are measured in a bulk manner,
resulting in a compilation of thousands of electrical pulses
referred to as Barkhausen noise.
 The amplitude of this signal magneto-elastic parameter
(MP).
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
44
Acoustic Methods
(Sonic methods)
Ultrasonic methods
– Detection of defects by ultrasonic waves
– Oscilloscope screen of ultrasonic tester
– Ultrasonic Virtual Images:
• 2-D image (C-scan)
• 3-D image
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
45
Ultrasonic NDT methods
(ASTM E 127, E478, Eb500)
 Frequency used: 100k-20MHz (audible: 20-20kHz)
 Produced by piezoelectric crystals, such as quartz, in electric fields. An a/s
voltage produces mechanical oscillations
 The divergence angle depends on the ratio of the wavelength to the
diameter of the source (e.g. In steel a sound at 5MHz has a wavelength of
only 1.25mm, a crystal <25mm will have a small divergence angle
 Usually one crystal probe both sends and receives sound
 The probe is moved progressively along the surface
 Cracks parallel to the waves reflect very little to the beam; hence, 2 tests
normal to each other are required.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
46
Detection of defects by ultrasonic waves
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
47
Oscilloscope screen of ultrasonic tester
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
48
2-D image (C-scan)
single depth
2015/7/17
Dr.
3-D image Multiple depth
(only the layer with
problem is shown)
Jonathan C.Y. Chung: NDE
49
To determine dimension, physical
or mechanical characteristics








Thickness of paint and enamel
Nickel coating
Hardness tests
Moisture content by electrical means
Proof tests
Surface roughness tests
Concrete test hammer
Sonic method for measuring thickness
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
50
Enamel and paint coating thickness
• The reluctance of the magnetic circuit of the
sensitive gauge head when placed on a coated
steel surface varies with the thickness of
enamel/paint.
• The gauge head is calibrated to read thickness
directly in thousands of an inch.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
51
Nickel coating thickness
• One type of instrument employs a portable
spring balance for test.
• Thickness of nickel coating on nonmagnetic
base metals is determined by force required to
detach the magnet from the coating.
• The greater the thickness of the nickel coating,
the larger the force required.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
52
Electronic device for measuring surface roughness
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
53
Concrete test hammer
A NDT impact test for
determining the
hardness, and the
probable compressive
strength of concrete in a
structure is by causing a
spring-loaded hammer
inside the tube
automatically to strike
the concrete.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
54
Ultrasonic
tester for
measuring
thickness
from one
side only.
2015/7/17
Dr.
Jonathan C.Y. Chung: NDE
55