NON DESTRUCTIVE AND DESTRUCTIVE ANALYSIS OR TESTING
NONDESTRUCTIVE TESTING (NDT)
Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials,
components or assemblies for discontinuities, or differences in characteristics without destroying
the serviceability of the part or system. In other words, when the inspection or test is completed the
part can still be used.
In contrast to NDT, other tests are destructive in nature and are therefore done on a limited number
of samples ("lot sampling"), rather than on the materials, components or assemblies actually being
put into service.
These destructive tests are often used to determine the physical properties of materials such as
impact resistance, ductility, yield and ultimate tensile strength, fracture toughness and fatigue
strength, but discontinuities and differences in material characteristics are more effectively found by
NDT.
NDT Test Methods
NDT methods may rely upon use of electromagnetic radiation, sound, and inherent properties of
materials to examine samples. This includes some kinds of microscopy to examine external surfaces
in
detail,
although
sample
preparation
techniques
for metallography, optical
microscopy and electron microscopy are generally destructive as the surfaces must be made smooth
through polishing or the sample must be electron transparent in thickness. The inside of a sample
can be examined with penetrating radiation, such as X-rays or neutrons. Sound waves are utilized in
the case of ultrasonic testing. Contrast between a defect and the bulk of the sample may be
enhanced for visual examination by the unaided eye by using liquids to penetrate fatigue cracks.
Test method names often refer to the type of penetrating medium or the equipment used to perform
that test. Current NDT methods are: Acoustic Emission Testing (AE), Electromagnetic Testing
(ET), Laser Testing Methods (LM), Leak Testing (LT), Liquid Penetrant Testing (PT), Magnetic
Particle Testing (MT), Neutron Radiographic Testing (NR), Radiographic Testing (RT),
Thermal/Infrared Testing (IR), Ultrasonic Testing (UT), Vibration Analysis (VA) and Visual
Testing (VT),... and Chemical Analysis!!!
1
IG
DESTRUCTIVE TESTING (DT)
In destructive testing, or (Destructive Physical Analysis DPA) tests are carried out to the specimen's
failure, in order to understand a specimen's structural performance or material behavior under
different loads. These tests are generally much easier to carry out, yield more information, and are
easier to interpret than nondestructive testing. Destructive testing is most suitable, and economic,
for objects which will be mass-produced, as the cost of destroying a small number of specimens is
negligible.
DT Test Methods
As the name suggests, destructive testing (DT) includes methods where your material is broken
down in order to determine mechanical properties, such as: Tensile Testing (TT), Hardness Testing
(HT) Stress Rupture Testing (SRT),... and Chemical Analysis!!!.
2
IG
DESTRUCTIVE AND NON DESTRUCTIVE CHEMICAL ANANLYSIS
The story that follows is predominantly valid for inorganic materials.
COMMON TYPE OF DESTRUCTIVE TESTING IS CHEMICAL NANLYSIS
SAMPLES
SAMPLE
PREPARATION
→
PREPARED SAMPLES FOR
ANALYSIS
These tests are generally more complicated to carry out than nondestructive testing, yield all
necessary information, but have quite complicated procedures for sample preparation.
Sampling methods are almost the same as for nondestructive analysis.
Sample preparation requires different laboratory procedures to chemically destroy the sample and
extract required substrates for analysis (wet chemistry is very involved). Usually one converts solid
or gaseous sample into liquid ones before analysis.
MOST POPULAR METHODS: Flame Atomic Absorption Spectrometry (FAAS), Graphite furnace
atomic absorption spectrometry (GFAAS), Inductively Coupled Plasma Optical Emission
Spectrometry (ICP-OES), Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
3
IG
SPECAL TYPE OF NON DESTRUCTIVE TESTING IS CHEMICAL NANLYSIS
SAMPLES
SAMPLE
PREPARATION
→
PREPARED SAMPLES FOR
ANALYSIS
These tests are generally much easier and faster to carry out than destructive chemical analysis,
usually they yield all necessary information and are equally complicated to interpret as destructive,
but instrumentation is quite expensive.
Sampling methods are almost the same as for destructive analysis.
Sample preparation requires different laboratory procedures to prepare chemically and physically
unchanged sample for analysis. Some simple mechanical preparations are enough.
MOST POPULAR METHODS:
Corpuscular induced (electron, protons, neutrons or atom nuclei): Scanning Electron Microscopy
(SEM), Scanning Electron Microscopy with Wavelength Dispersive Spectrometry (SEM-WDS),
Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS), Particle-induced
X-ray emission spectrometry (PIXE), Neutron Activation Analysis (NAA)…
4
IG
Wave induced (X-rays, Gamma-rays): Wavelength Dispersive X-Ray Fluorescent Spectrometry
(WDXRF), Energy Dispersive X-Ray Fluorescent Spectrometry (EDXRF)…
5
IG