TABLE OF CONTENTS There is no nondestructive test method that is a panacea. Each method has its advantages and limitations. It is a matter of selecting the test method that offers the most effective approach to solving the examination problem. When determining whether ultrasonics is the most appropriate test method, consideration should be given to the following:
Part and geometry to be examined
Material type
Material thickness
Material process cast, wrought, etc.
Type of discontinuities to be detected
Minimum discontinuity size to be detected
Location of the discontinuities surface-breaking or internal
Orientation of discontinuities (very important when selecting a test technique)
Accessibility to areas of interest
Surface conditions
Type of examination record required
Ultrasonic inspection is ideal for locating small, tight discontinuities assuming the following:
The sound energy can be projected at some angle that will respond favorably to the orientation of the reflector.
The relationship between the size of the discontinuity and the material s grain structure allows for an acceptable signal to noise ratio.
The surface condition is suitable for scanning. A poor scanning surface will not only require a more viscous couplant but possibly the use of a lower test frequency. This may not provide the necessary resolution for the test.
The advantages of ultrasonic examination are as follows:
Inspection can be accomplished from one surface
Small discontinuities can be detected
Considerable control over test variables
Varieties of techniques are available...
