Wave2000 Example #3:
Flaw Detection (scattering from a crack).
Wave2000 has an easy to use graphics file format to represent arbitrary
structures. With Wave2000 we say: "If you can draw it, you can
simulate it." A simple example of this is shown in the figure below which
is a "PCX" graphics file representing an object to be ultrasonically interrogated.
It represents a solid block of Plexiglas, within which is a small (1 mm
x 3 mm) crack. The "crack" is a void (vacuum) region, represented in Wave2000
by a (reserved) pixel value of 255. By changing the grey level associated
with the crack region, a crack containing virtually any liquid or solid
can be simulated.
In this example, a 1 MHz Gaussian modulated sine wave is input into the block
with a 1.5 cm source transducer (not shown) located on the left side of the
object. The transducer is defined to operate in pulse-echo mode, thus allowing
the backscattered ultrasound signal to be measured (i.e., plotted and saved
in an ASCII file). The "movie" below shows the beautiful structure of the scattered
ultrasound wave. Note that only a few frames of the propagating wavefront are
shown; Wave2000 of course allows the user to control the "relative frequency" of
display on their own computer.
Pulse-echo configurations are just one of Wave2000's many transducer
options. Shown below is a plot of the receiver and source waveforms.
The source waveform, appearing at the left side of the graph, is a sinusoid
with a Gaussian envelope. The reflected wave, due to the presence of the
crack, appears later in time (at about 8 microseconds).
Explore many "what if" scenarios with Wave2000. It is straightforward
in Wave2000 to modify the simulation model to address a variety of questions.
In the context of this simulation example, these may include: What happens
to the reflected wave if the crack is made longer or shorter, thicker or thinner,
is oriented obliquely or off-center with respect to the source, or contains
some (non-void) material (e.g., water)? These and similar questions may be
addressed with Wave2000 usually as easily as this one shown here. In general, "if
you can draw it you can simulate it" with Wave2000.