New Way to Perform Ultrasonic Inspection on NASA Test Articles

Recently, Jason Eldridge, one of our ESSSA employees who works at Marshall Space Flight Center, won an Innovation Award for the Materials and Processes Laboratory.  Jason’s job is to use ultrasonic technology to inspect for any defects in welds on test articles that pass through the Center.  An issue he has encountered in using the ultrasonic scan is that he must have water in between the ultrasonic device and the area he is inspecting (ultrasonic scans do not like and air between the scanner and the article being tested).  The pictures below show a basic setup when they are performing Phased Array Ultrasonic Test (PAUT) inspections in the field.

PAUT Setup

PAUT Setup

PAUT Setup

PAUT Setup

The picture below is a closer look at the wedge/transducer configuration showing how the group currently incorporates the water. If you zoom in closely on picture three, you will see the water leaking out of the wedge during an actual inspection.

PAUT Testing showing water leakage

PAUT Testing showing water leakage

Another view of PAUT Testing

Containing the water for clean up

The picture above shows one attempt to contain the water (unfortunately, it wasn’t very successful). This is what prompted Jason to start thinking about creating a new wedge design, with a new conduit that would allow the team to perform inspections without the use of water.  Jason’s idea came from his home 10-gallon aquarium with fish and snails.  Jason was thinking about a better way to perform the inspection when he saw a snail crawling up the side of the tank.  Noticing how the snail was almost suctioned to the side of the tank, Jason immediately knew the design he should test.  From there, Jason researched different materials they could use in the snail mold, before settling on a ballistics gel used by the military and police forces.    

Snail Wedge Drawing

Snail Wedge Drawing

Along with solving the water issue, Jason’s design can eliminate other issues that are present in certain setup configurations due to a design flaw in the wedge currently in use.  This design also allows the team to inspect thicker material and, because the snail design has a sloped front, the team has the option to position the transducer more easily near flanges.

Currently, Jason is working with the ballistics gel, which has a density similar to human tissue and transmits sounds well. After receiving samples from the manufacturer, he tested the gel for material velocity properties. What he is finding interesting is that the gel is very similar to water in terms of velocity, but because of the difference in density, it takes quite a bit more energy to produce signal responses comparable to those produced using the current wedge. Using a calibrated standard, Jason can nearly match the responses from the reflectors, but in order to do so he has to increase the energy input, or gain level (measured in dB), by approximately 230%.  With this, Jason almost has a design ready for the the testing phase of this project. Hopefully, within the next few days, Jason will have the latest revision in hand.

When Jason first began designing this new idea, he brought it up to the NASA NDE team lead. His NASA lead thought it was a good enough idea that they put together a proposal for funding through EM20’s Technical Excellence program. Each year, EM20 chooses a number of proposals to fund. Jason and his team received the award, so this entire project has been funded through NASA.

Prototype Molds

Prototype Molds

Prototype Molds

Prototype Molds