Civil Engineering Reference
In-Depth Information
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Temperature, F
FIGURE SP3.5
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3.8.4
Bend Test
In many engineering applications, steel is bent to a desired shape, especial-
ly in the case of reinforcing steel. The ductility to accommodate bending is
checked by performing the semiguided bend test (ASTM E290). The test
evaluates the ability of steel, or a weld, to resist cracking during bending.
The test is conducted by bending the specimen through a specified angle
and to a specified inside radius of curvature. When complete fracture does
not occur, the criterion for failure is the number and size of cracks found on
the tension surface of the specimen after bending.
The bend test is made by applying a transverse force to the specimen in
the portion that is being bent, usually at midlength. Three arrangements can
be used, as illustrated in Figure 3.21. In the first arrangement, the specimen
is fixed at one end and bent around a reaction pin or mandrel by applying a
force near the free end, as shown in Figure 3.21(a). In the second arrange-
ment, the specimen is held at one end and a rotating device is used to bend
the specimen around the pin or mandrel, as shown in Figure 3.21(b). In the
third arrangement, a force is applied in the middle of a specimen simply
supported at both ends, Figure 3.21(c).
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3.8.5
Hardness Test
Hardness is a measure of a material's resistance to localized plastic deforma-
tion, such as a small dent or scratch on the surface of the material. A certain
hardness is required for many machine parts and tools. Several tests are
available to evaluate the hardness of materials. In these tests an indenter
(penetrator) is forced into the surface of the material with a specified load
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