FIELD OF THE INVENTION
The present invention relates to a reference block for ultrasonic testing of spot
welded components. More particularly, the invention relates to a device for
setting amplifier gain, measuring sensitivity of an ultrasonic testing equipment
with a probe and evaluating the presence of defects in spot welds in terms of
percentage of nugget area.
BACKGROUND OF THE INVENTION
Ultrasonic testing is a non-destructive testing method for evaluating the quality
of spot welded products. The probable defects in spot weld are lack of bonding
between the two bonded surfaces, and porosity. When there is a requirement to
identify the porosity/lack of bonding present including quantizing the defects
based on acceptable percentage of nugget area, it is to be evaluated by sizing of
the lack of bonding and porosity as a percentage of the nugget area.
US 5,837,880 teaches an ultrasonic calibration block which performs all the
functions of an IIW block, except representing the expected defects in the job.
Us 5,163,027 discloses a calibration block to generate a look-up table of standard
waveform amplitudes.
JP 2007057414 describes an ultrasonic calibration block with ceramic embedded
welded sample as reference with foreign material (ceramic rectangular body) as
defect.
CA 779622 teaches a method of evaluating the characteristics of spot weld by
UT.

WO 2004/005913 discloses spot weld ultrasonic testing by analyzing echo signals
of higher order.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for setting amplifier
gain, measuring sensitivity of an ultrasonic testing equipment with a probe and
evaluating the presence of defects in spot welds in terms of percentage of
nugget area, which is operable as a reference reflector.
Another object of the invention is to propose a device for setting amplifier gain,
measuring sensitivity of an ultrasonic testing equipment with a probe and
evaluating the presence of defects in spot welds in terms of percentage of
nugget area, which is formed of a material as that of the job.
A still another object of the invention is to propose a device for setting amplifier
gain, measuring sensitivity of an ultrasonic testing equipment with a probe and
evaluating the presence of defects in spot welds in terms of percentage of
nugget area, which is configured such that the surface of the reflector is similar
to the actual defect.
Yet another object of the invention is to propose a device for setting amplifier
gain, measuring sensitivity of an ultrasonic testing equipment with a probe and
evaluating the presence of defects in spot welds in terms of percentage of
nugget area, where a specific size of the surface of the natural defect is used as
the reference.
A further object of the invention is to propose a device for setting amplifier gain,
measuring sensitivity of an ultrasonic testing equipment with a probe and

evaluating the presence of defects in spot welds in terms of percentage of
nugget area, where the natural defect of the specific size is used as the
reference at a specified bonding region.
A still further object of the invention is to propose a device for setting amplifier
gain, measuring sensitivity of an ultrasonic testing equipment with a probe and
evaluating the presence of defects in spot welds in terms of percentage of
nugget area, which exhibit the natural defects.
These and other objects and advantages of the invention will be apparent from
the ensuring description.
At the outset of the description, which follows, it is to be understood that the
ensuring description only illustrates a particular form of this invention. However,
such a particular form is only an exemplary embodiment and the teaching of the
invention is not intended to be taken restrictively.
SUMMARY OF THE INVENTION
Accordingly, there is provided a device for setting the amplifier gain in an
ultrasonic testing equipment with a probe combination, the device comprising; a
single block having a projected face, incorporating an equivalent weld defect at
the interface between two materials bonded, the block being produced by a
material identical to the material of the job-piece and a correspondingly sized
reflector.
The surface of the block constitutes a true representative of the job. The
material of the device is required to have the same heat treatment, geometrical,
metallurgical and acoustic properties as that of the job under test.

The single block is formed of material identical to that of the job material used
for spot welding and having at least three flat bottom holes at three different
depths representing three thicknesses, wherein three plates are spot welded.
Number of holes may vary depending upon number of plates spot welded. The
device is configured with identical heat treatment, geometrical, metallurgical and
acoustic properties as that of the job under test.
The present invention provides a device which represents the defects expected in
the job, and capable for setting amplifier gain and sensitivity of ultrasonic testing
equipment.
Thus, the present invention incorporates flat bottom hole to represent natural
defect, and sizing of natural defects as percentage of nugget size.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Shows an embodiment of the device according to the invention.
Figure 2 - Shows the process of evaluating the weld defects using the device of
Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
The device comprises a single block formed of material identical to that of the
job under spot welding and having at least three flat bottom hole(l). The device
is configured with heat treatment, geometrical, metallurgical and acoustic
properties as that of the job under test

The UT probe (not shown) is initially set on top surface of the block and the UT
probe (not shown) is moved forward and backward till an echo from the
reference reflector (1) i.e. the first Flat bottom hole size 1.0 mm is maximized.
Then the gain control is adjusted to bring the echo height to 40% and the echo
tip is marked on a first screen (a). Without altering the amplifier gain setting, the
UT probe is set on the top surface of the block (1) where the second Flat bottom
hole size 1.0 mm is available, and the echo is maximized and marked on a
second screen (b). Without altering the amplifier gain setting, the UT probe is set
on the top surface of the block (1) where the third Flat bottom hole size 1.0 mm
is available and echo is maximized and marked on a third screen (c) ( Fig 2 ).


WE CLAIM
1. A device for setting amplifier gain, measuring sensitivity of an ultrasonic
testing equipment with a probe and evaluating the presence of defects in
spot welds in terms of percentage of nugget area, the device comprising:
- a single block having a projected face incorporating at the interface
between two components under welding, the weld defect being
substantially equivalent to an expected defect in the welded joint;
- an ultrasonic testing (UT) probe of an UT-equipment locatable and
movable along the top surface of the single block;
wherein the single block is formed of material identical to that of the job
with heat treatment, geometrical, metallurgical, and acoustic properties
corresponding to those of the job, wherein the block having at least three
flat-bottom holes at different depth representing different thickness, and
wherein a horizontal movement of the probe over the flat bottom surface
of the block is enabled to generate echo at said three different holes
allowing evaluation of the defects on the actual weld.
2. The device as claimed in claim 1, wherein the echo from the first hole is
maximized at hole size 1.0 mm, wherein the gain control is adjusted to
maintain a 40% echo-height with a simultaneous marking of the echo tip
on a first screen, wherein the echo is further adjusted by moving the
probe where the second hole size of 1.00 mm is located so as to maximize
the echo with a simultaneous marking of the echo-tip on a second screen,
and wherein the probe is set on the third hole without altering the

amplifier gain setting where the hole size is 1.0mm such that the echo is
maximized and marked on a third screen.
3. The device as claimed in claim 1 or claim 2, wherein the area of the
reflector is equal to that of the natural defect used as reference at a
specified bonding region of the job.