STEEL - Materials for Civil and Construction Engineers - page 124

FIGURE 3.22 Rockwell hardness test machine.

Hardness tests are simple, inexpensive, nondestructive, and do not re-
quire special specimens. In addition, other mechanical properties, such as
the tensile strength, can be estimated from the hardness numbers. Therefore,
hardness tests are very common and are typically performed more frequently
than other mechanical tests.

■ 3.8.6 Ultrasonic Testing

Ultrasonic testing is a nondestructive method for detecting flaws in materi-
als. It is particularly useful for the evaluation of welds. During the test, a
sound wave is directed toward the weld joint and reflected back from a dis-
continuity, as shown on Figure 3.23. A sensor captures the energy of the re-
flected wave and the results are displayed on an oscilloscope. This method is
highly sensitive in detecting planar defects, such as incomplete weld fusion,
delamination, or cracks (Hassett, 2003).

Ultrasonic tester

Slag

Porosity

FIGURE 3.23 Ultrasonic

test of welds.