UT Lesson 1

Frequency increases

wavelength decreases

Certification of an individual in NDT to Level I, Level II, or Level III is simply a written testimony of qualification. Certification is:

- Meant to document the qualification of an individual. - The responsibility of the employer.

Level III ensures personnel are qualified to perform:

- Develop, qualify, and approve procedures, and establish and approve nondestructive testing methods and techniques to be used by Level I and Level II personnel. - Interpret and evaluate test results in terms of applicable codes, standards, specifications, and procedures. - Assist in establishing acceptance criteria where none are available, based on a practical background in applicable materials, fabrication, and product technology.

Major challenges facing everyone in the nondestructive testing industry

- Education and attitude. - Devotion to the idea that there is always something more to learn, which is crucial to our development into competent technicians.

EARLY TESTING METHODS

- For centuries, objects were tested by hitting them with a mallet and listening for a tonal quality difference. - The natural resonance of an object gave evidence that the struck object was free from imperfections.

Qualification takes place before certification. Recommended Practice No. SNT-TC-1A states qualification should include the following for any method:

- Formal training. - Application-specific experience. - Demonstrated knowledge. - Ability to pass a vision test.

Level III personnel are qualified to:

- Have familiarity with appropriate nondestructive testing methods other than those for which they are specifically certified, as demonstrated by passing an ASNT Level III Basic examination. - Be responsible for, and capable of, training and examination of Level I and Level II personnel for certification in the methods for which they are certified. - Write the written practice as well as other testing procedures.

Ultrasonics

- Is the study and application of sound waves having frequencies above the audible range of the human ear. - Is a branch of acoustics. - Begins at 20 000 cycles per second (20 kHz). - Uses higher frequencies for testing materials.

Level I personnel are qualified to:

- Perform specific calibrations, nondestructive tests, and evaluations for determining the acceptance or rejection of tested objects in accordance with specific written instructions. - Record test results. Normally, Level I personnel do not have the authority to sign off on the acceptance and completion of the nondestructive test unless specifically trained to do so with clearly written instructions. - Carry out nondestructive testing job activities in accordance with written instructions or under the direct supervision of a Level II or Level III technician.

Level II personnel are qualified to:

- Set up and calibrate equipment. - Interpret and evaluate results with respect to applicable codes, standards, and specifications. - Organize and report the results of nondestructive tests. - Oversee on-the-job training of, and guidance to, Level I and trainee personnel. - The Level II technician must understand the scope and limitations of each method for which he or she is certified.

CHARACTERISTICS OF ULTRASOUND

- Sound is the mechanical vibration of particles in a material. - Particles vibrate around a fixed point at the same frequency as the sound wave.

APPLICATIONS OF ULTRASONIC TESTING

- Test a variety of metallic and nonmetallic products. - Economically inspect test objects for subsurface discontinuities. - Provide information to NDT personnel to make quality-control decisions.

V = λ × f (Formula for the velocity of sound) λ = V / f {Formula for wavelength) f = V / λ (Formula for frequency)

- λ= wavelength (most often expressed in mm) - V = velocity (most often expressed in km/s) - f = frequency (most often expressed in MHz) - BASIC MATH OF ULTRASOUND

Pulse-echo technique

Converts time of flight into distance that the sound wave travels within the test object.

pulse-echo technique

Most ultrasonic thickness gaging and discontinuity detection/ evaluation use the ________________.

Level III personnel are expected to be responsible for:

Nondestructive testing operations to which they are assigned and for which they are certified.

The time it takes for the wave to travel

a distance of one complete wavelength is the same amount of time it takes for the atomic structure in the path of that energy to execute one complete vibration.

The length of a sound wave

measured from trough to trough, or crest to crest, is always the same. This distance is known as the wavelength (λ).

λ = V / f

relationship of sonic velocity (V) within the host material, the frequency (f) selected for use by the technician, and the resultant wavelength (λ) determined by the ratio.