QUALITY CONTROL OF COMPLEX GEOMETRIES

Background

Mission success depends on reliable, high-performance parts. Effective quality

control of manufactured parts is necessary to ensure they perform their

intended function without fail. This is especially true for advanced parts with

complex geometries. One way of verifying conformance to specification is

through-thickness gauging. On complex parts, accurate and repeatable thickness

readings can be difficult to obtain with standard mechanical measurement

methods. More advanced methods, like radiography, are expensive and have

their limitations. For these types of applications, Ultrasonic Thickness Gauging

provides a precise, reliable, and economical solution.

Ultrasonic Thickness Gauging delivers a precise measurement of wall thickness

by sending out a sound wave and “listening” for the return echo. This “pulseecho” method only requires access to one side of a wall, enabling measurement

where one side of the part is obstructed. Probe faces can be small, and attached

to angled handles, allowing measurement within physically restrictive

dimensions. Measurements can also be performed quickly. Once a probe and

gauge are set up for a specific material, contact with the part at different

locations will yield instant and repeatable readings.

Equipment

TG-410 Thickness Gauge

• Single and dual element transducers
• Contact, delay/immersion, through-transmission, shear mode
• High-Speed LCD Display
• Freeze-screen direct access button
• Split-View: Dual A-Trace display
• Split-Scan: View A-Scan and time-encoded B-Scan simultaneously
• Peak Echo Hold: Fixed or timed "waterfall" reset
• Default and user-programmable setups
• Rugged aluminum case with rubber end caps
• Optional Windows-based Data Transfer software

Technical Outline / Procedure

A regular customer of NDT Systems required assistance in improving

their quality control process. They needed to measure the wall

thickness of various regions on the pictured part but were not able to

take reliable readings with other methods they tried. It was

determined to use an NDT Systems TG-410 Thickness Gauge in

conjunction with an AE12205-A ultrasonic probe. The TG-410 is an Atrace capable device with adjustable gain and gates, and the AE12205-

A is a 12MHz pencil-style probe with an angled shaft.

Cast parts are generally acoustically attenuative, and the higher

frequency needed for precise measurements can be difficult to resolve

without a waveform trace and adjustable gates. By setting the gain

high enough on the TG-410, and blocking out the excess noise from the

initial pulse, repeatable measurements down to four decimal places

with an 80% FSH are achievable. The delay line on the AE12205-A

enables higher gain settings than a comparable contact transducer by

delaying the interface echo, allowing the user to determine which

signals are noise and which are valid echoes.

After observing the successful measurement of the part, the

customer decided to purchase the TG-410 and the AE12205-A and

implement them in their production quality control process.

For thicker parts manufactured with more acoustically attenuative

materials, pairing the AE12205-A with the NDT Systems Novascope

6000 Precision Thickness Gauges would be a more robust solution.