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echo will be generated, which will cause an incorrect reading in
the thickness measurement result and cause a misjudgment.
In addition, with the coarsening of the grains, the anisotropy in
the crystallographic direction of the metal becomes more
pronounced, resulting in differences in the speed of sound in
different directions, and the maximum difference can even
reach 5.5%. Moreover, the density of the tissue at different
positions in the workpiece is also inconsistent, which will also
cause differences in the speed of sound. These factors will
cause inaccurate measurement results. Therefore, special care
should be taken when measuring castings.
● When measuring castings with rough surfaces, a couplant
with a higher viscosity must be used.
● It is recommended to use the same material as the object to
be tested and a test block with the same measurement
direction as the object to be tested to calibrate the sound
velocity of the material.
When measuring castings, pay attention to:
Using any ultrasonic thickness gauge, when the thickness of the
material to be tested falls below the lower limit of the probe, it
will cause measurement errors. If necessary, the minimum limit
thickness can be measured by the test block comparison method.
When measuring ultra-thin materials, an erroneous result called
"double refraction" sometimes occurs, which occurs when the
displayed reading is twice the actual thickness; another
erroneous result is called "pulse envelope, cyclic "Jump", its
phenomenon is that the measured value is greater than the actual
thickness, in order to prevent such errors, the measurement
should be repeated when measuring critical thin materials.
B.6.1 Ultra-thin materials
B.6 Methods to reduce measurement errors
Summary of Contents for SW-6510S
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