ASNT

Table 2 Nondestructive test methods and corresponding parts of electromagnetic spectrum

Approximate Wavelengths (m)

Approximate Frequencies (Hz)

Interrogating Energy

Test Method

10 –16 to 10 –8 10 –8 to 10 –7

10 24 to 10 17 10 17 to 10 15

X-rays or gamma rays Ultraviolet radiation Light (visible radiation) Heat or thermal radiation

radiographic testing (RT) various minor methods a

4 × 10 –7 to 7 × 10 –7

10 15

visual testing (VT)

10 –6 to 10 –3 10 –3 to 10 1

10 15 to 10 11 10 11 to 10 7

infrared and thermal testing (IR) radar and microwave methods

Radio waves

a. Ultraviolet radiation is used in various methods: (1) viewing of fluorescent indications in liquid penetrant testing and magnetic particle testing; (2) lasers and optical sensors operating at ultraviolet wavelengths.

Radiation wavelength (nm)

10 6

10 5

10 4

10 3

10 2

10 1

10

10 –1

10 –2

10 –3

10 –4

10 –5

10 –6

X-rays

Cosmic rays

Radio

Infared

Ultraviolet

Gamma rays

Visible light

10 –9

10 –8

10 –7

10 –6

10 –5

10 –4

10 –3

10 –2

10 –1

1

10

10 2

10 3

Photon energy (MeV)

Figure 3 Electromagnetic spectrum.

complete nondestructive test of a test object. For example, if surface cracks must be detected and eliminated and the test object is ferromagnetic, then magnetic particle testing would be the obvious choice. If that same material was aluminum or titanium, then the choice would be penetrant or electromagnetic testing. However, for either of these situations, if internal discontinuities were sought, then ultrasonic or radiographic testing would be selected. The exact technique in either case would depend on the thickness and nature of the material and the type or types of discontinuities that must be detected.

added process in the manufacturing activity of a product. As a result, NDT can be vulnerable to compromise for the illusion of profit. However, referring to the “Purpose of Nondestructive Testing” discussed earlier, there are economic reasons for performing NDT that do add value to the product, not the least of which are reliability and high-quality reputation. Additionally, the reduction in the risk of failure has significant economic benefits that can be calculated. The economic benefit of NDT is acknowledged in many industries such as aerospace, electronics, petrochemical, and infastructure. The profit from NDT is realized when the cost of not performing NDT outweighs the cost of NDT. Performed in conjunction with statistical quality control methods, NDT provides critical information for continuous process improvement, a hallmark of good manufacturing. Nondestructive testing should be used as a control mechanism to ensure that manufactur- ing processes are within design performance

VALUE OF NONDESTRUCTIVE TESTING

The contribution of nondestructive testing to profits is reviewed and justified by Emmanuel Papadakis (Papadakis 2006). Industrial engineering practice has been known to consider NDT as a non-value

CHAPTER 1

9

Part 1