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188 Part III: Inspection and Test
Testing
machine
ZSB
furnace
Typical use
Figure 17.8 Tensile test for a furnace.
Part III.D.2
stretch. Figure 17.8 shows a tensile test for a furnace (Integrated Publishing 2008)
(Instron 2008).
The results of tensile testing are used in selecting materials for engineering
applications. Tensile properties are included in material specifications to ensure
quality. Tensile properties are used to predict the behavior of materials under
certain forms of tension (Davis 2004).
Force Testing. Force testing includes free bend, guided bend, nick-break, impact,
and crash testing. The free-bend test is designed to measure the flexibility of a weld
deposit and the heat-affected area adjacent to the weld. It is also used to determine
the percentage of stretching of the weld metal (Integrated Publishing 2008).
Figure 17.9 shows a free-bend test and the forces applied in the test to measure the
flexibility.
The guided bend test is used to determine the quality of weld metal at the face
and root of a welded joint. The sample object is placed across the supports of the
die. A plunger, operated from above by hydraulic pressure, forces the sample into
the die. To fulfill the requirements of this test, the sample object has to be bent
to 180 degrees with no cracks on the surface greater than 1/8 inch (Integrated
Publishing 2008).
The nick-break test is useful for determining the internal quality of the weld
metal. This test is used for detecting whether internal defects exist, such as slag
inclusions, gas pockets, lack of fusion, and oxidized or burned metal. For example,
there should not be more than six pores or gas pockets per square inch of the
exposed broken surface of the weld.
The impact test is used to check the ability of a weld to absorb energy under
impact without fracturing. This is a dynamic test in which a test specimen is
broken by a single blow, with the energy used in breaking the piece measured in
foot-pounds. This test compares the toughness of the weld metal with the base