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Chapter 17: D. Testing Methods 187
C. Surplus wiped off leaving penetrant in crack
D. Developer powder applied, dye soaks into powder
E. View colored indications, or UV lamp shows up fluorescent indications
2. DESTRUCTIVE TESTING
Define methods such as tensile, force testing,
and leak testing. (Knowledge)
Body of Knowledge III.D.2
Destructive testing puts the sample object under certain circumstances until it
actually fails. The failed pieces are then studied and compared to known standards
to determine the quality of the object. This type of testing is generally much
easier to carry out, yields more information, and is easier to interpret than nondestructive
testing (Integrated Publishing 2008).
Destructive Testing Applications and Objectives
Destructive testing usually provides a more reliable assessment of objects,
but destruction of the test object usually makes this type of test more costly to the
test object’s owner than nondestructive testing. Destructive testing is also inappropriate
in many circumstances, such as forensic investigation. A tradeoff has to
be made between the cost of the test and its reliability. If a nondestructive test can
provide the required results, the destructive test can perhaps be waived. Destructive
testing may be performed on a sampling of test objects that is drawn randomly
for the purpose of characterizing the testing reliability of the nondestructive test
(Integrated Publishing 2008).
Destructive testing is mostly used in metal testing, especially to test the
strength of welded parts. It is also used to determine the ability of a metal
to stretch or bend. It is common in automobile manufacturing testing and other
metal manufacturing industries.
Part III.D.2
Methods of Destructive Testing
Tensile Testing. A tensile test, also known as a tension test, is the method for
determining behavior of materials under axial stretch loading. Data from this test
are used to determine elastic limit, stretching, modulus of elasticity, proportional
limit, and reduction in area, tensile strength, yield point, yield strength, and other
tensile properties. This test is probably the most fundamental type of mechanical
test that can be performed on a material. Tensile tests are simple, relatively inexpensive,
and fully standardized. By pulling on something, you will very quickly
determine how the material will react to forces being applied in tension. As the
material is pulled, you will find out its strength along with how much it will