Non-destructive testing methods
Vibration analysis, infrared thermography,
acoustic emission analysis, ultrasonic imaging,
x-ray computer tomography, ground penetrating radar,
digital radiography, optical testing methods,
eddy current imaging, magneto-inductive cable testing
Vibration analyses can be carried out on a wide
range of structures such as bridges, dams, buildings,
etc. The tests are designed to determine the dynamic characteristics of the structures such as natural frequency, modes of vibration and damping. The
results are used to gain basic information for the
evaluation of earthquake safety, long-term monitoring, short-term condition tests and optimising of analytic models. The two methods available are «ambient vibration analysis» and «forced vibration analysis».
Impulse excitation for large structures
IR thermography is a method for measuring the temperature distribution of a surface. It permits to detect regions of heat production (e.g. due to a crack under
cyclic loading or a hot spot in a defective IC) or
regions of inhomogeneous cooling (e.g. due to blisters
or air voids in a pavement or under waterproof membranes). In the building phase of road constructions, IR thermography can be used to control the temperature of the single components. When flashes or a sine-modulated radiator heat an object, voids and debondings buried below the
Phase display of a CFRP plate
with defective bonding
surface hinder the heat transfer. The resulting transient thermal contrast on the surface is made visible with pulse or lock-in thermography.
Acoustic emission analysis uses sensors mounted
on the surface of parts or structures to record elastic
Acoustic emission analysis is
also used for load tests carried
out during investigations on a
car chassis made of carbon
fibre reinforced plastic.
waves caused inside by microscopic processes
such as, e.g., crack growth. In principle, the analysis
allows a qualitative and, under certain conditions,
During filling with silage,
selected locations (in this case
the hatches) of an agricultural
silo (height approx. 10 m,
ø approx. 4 m) are monitored
using acoustic emission analysis.
quantitative assessment of the integrity of the part or
structure. Acoustic emission analysis is also suited for other industrial applications, e.g., process monitoring.
Ultrasonic waves permit non-destructive testing of
materials for the detection of component defects.
Using this test procedure the precise location of
cracks, pores, inclusions and fusion flaws can be
determined. This method is used for testing metal,
ceramic and plastic materials together with their
bonding system (adhesion, welding, soldering). Images are generated either with
20 MHz ultrasonic images of
Top: good bonding
Middle: faulty bonding
Bottom: as comparison a test
block with flat-bottom holes
(ø = 1-6 mm).
a high-precision mechanical scanner or a phased array system.
Computer tomography is a well-known test method
used for medical diagnostics. Using industrial scanners, cross-sectional pictures of the object being investigated are taken in any selected plane, recorded
and processed. Three-dimensional views, surface
point clouds and first-article inspections can be pro-
duced by stacking contiguous tomograms.
The tomogram shows a section through a metal-ceramic
joint. The metal and ceramic
plates are soldered with a mattress-shaped interlayer. The
aim of the investigation was
non-destructive testing of the
solder joints. The tomogram
shows that one joint has no
GPR is used for investigations on roads, bridges and
other elements of infrastructure. The test method is
based on an electromagnetic signal which is...
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