What is the difference between ultrasound and dye penetrant tests for metal?

I understand both techniques can be used to detect subsurface (micro fractures) metal cracks, such as in pinion gears, or any other heavy rotary type equipment. Which method is a) more sensitive to picking up microscopic cracks, 2) less costly to initially buy equipment and run on a regular basis, and 3) easier to implement (train people, etc)


*DP Test is less costlier,easy to train people, but as far as more sensitive to picking up microscopic cracks is concern, ultrasound test is more reliable.
*Ultra sound test requires a capital investment.
*Please visit:
*Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more.
-A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.
For DP test, please visit:
The primary difference between ultrasound and dye penetrant tests is that the dye penetrant test can only detect surface defects, whereas ultrasound test is meant for detecting flaws inside the metal through its thickness. In fact ultrasound test cannot detect any flaw within few millimeters from the surface.

The answers post by the user, for information only, FunQA.com does not guarantee the right.

More Questions and Answers:
  • Where Specific gravity and Density can apply and how?
  • Is an engineer also a scientist?
  • About color coding of resistors...?
  • Circuit diagram for a sine wave inverter?
  • I have a sample of PVC pipe how i know if it is a PVC or UPVC and is the colour of pipe state somthing?
  • Which new construction(s) ?
  • What would you like to see invented in your life time?
  • Is it true that a rechargeable drill's battery became out of order if you let it lost its entery charge?
  • How do u find out the capacity of a tank which can either be cylinder, square or rectangle??