Innovation Polymers

Frequency Considerations for Aqualink™ 100

Ed Ginzel — Thu, 16 Jan 2025 00:14:32 +0000

High frequency ultrasonic wheel applications may have become easier based on the Aqualink 100 material.

A series of waveforms were captured from a 6mm diameter 15MHz Alpha2 Aerotech probe. This probe is a typical delay line probe with a Rexolite delay line approximately 9.5mm long.

With the probe coupled to the delay line, the signal from the Rexolite/air interface was captured using a PCPR100 pulser-receiver tuned to 15MHz and using a 1 cycle bipolar pulse at 225V (i.e. 450Vpp). The waveform and FFT are seen here for the Rexolite condition.

A spectral analysis of the FFT indicates that for the -6dB drop, the centre frequency downshifts to 11.7MHz in Rexolite.

The probe was then removed from the Rexolite delay line and placed in a small water column approximately 14mm with a tungsten carbide plate used as a target to ensure a high acoustic impedance. The waveform and FFT were collected and displayed here.

A spectral analysis of the FFT indicates that for the -6dB drop, the centre frequency downshifts to 12.8MHz in water. There is no discernable dispersion in water so it may be assumed that the internal damping (back loading) is limiting the natural frequency of this probe. This would imply that the Rexolite is causing a 1MHz downshift in frequency content.

With the probe removed from the Rexolite delay line it was placed on a 5.5mm thick sample of Aqualink100 and coupled with a medical gel couplant and the tungsten carbide plate coupled to the opposite surface of the Aqualink100. The waveform and FFT were collected and displayed here.

A spectral analysis of the FFT indicates that for the -6dB drop, the centre frequency downshifts to 8.2MHz in Aqualink100 compared to water. This is a relatively large “centre frequency” downshift; however, the bandwidth increased from 29% in water to 114% in Aqualink. There is some variability in signal frequency content with regards to the method used (i.e. manually holding the probe on the sample). The Spectral analysis shows a Peak frequency of just 7.03MHz, yet the above FFT indicates a peak had occurred at a point nearer to 11MHz.

A review of Aqualink properties from the MAPAS software analysis shows that at 5MHz there was essentially no downshift in centre frequency.

With this in mind, a pulse-echo signal was obtained using the 5.5mm thick sample used with the 15MHz probe and it was placed in direct contact on an immersion probe with a 10MHz nominal frequency and 12.5mm diameter.

The probe was driven at 225V negative bipolar and tuned to exactly 10MHz. It was noted that by adjusting the number of cycles from 1 to 4, the centre frequency moved upward. With 4 cycles, the resulting frequency peaks at 8.98MHz.

Aqualink is a tough durable polymer compared to Aqualene. A relatively thin wall tyre may offer an alternative to allow Aqualink 100 to be used for high-frequency (10-12MHz) ultrasonic wheel applications. Consider too that even Rexolite noticeably downshifts high-frequency pulse content.

About Innovation Polymers:

Innovation Polymers is a leader in acoustic capable polymer solutions for the non-destructive testing industry, providing high-quality products and services to clients across a range of industries. With a commitment to innovation and customer satisfaction, the company has the capability to develop a wide range of unique sound coupling polymeric media and has earned a reputation as a trusted partner in the industry.

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Conformable wedge covers inspection of multiple radii

cdurkin — Mon, 24 Jun 2024 21:53:18 +0000

A CONFORMABLE WEDGE WAS KEY TO BEING ABLE TO INSPECT MULTIPLE RADII WITHOUT HAVING A LARGE COLLECTION OF CURVED WEDGES

Kitchener, ON

Innovation Polymers was recently tasked with designing a conformable wedge that could be used with a phased-array probe to inspect the intrados of runner blades in Francis hydraulic turbines. These turbines consist of a set of curved blades arranged radially around an axis of rotation. The blades are welded in position at a crown plate on the top and a shroud ring at the bottom. The contact between the blade and the plate is manually blended to form a smooth radius; however, that radius varies along the length of the contact. Inspection of the welds is carried out using phased-array ultrasonic testing.

In order to accommodate the change in radius without having a large collection of curved wedges, Innovation Polymers designed a conformable wedge that allowed inspection of the length of the blade with a single wedge that could also allow for small irregularities in the blending quality.

About Innovation Polymers:

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New Polymer from Innovation Polymers Provides Higher Conformability & Better Attenuation

cdurkin — Tue, 02 Nov 2021 15:00:07 +0000

Innovation Polymers announces a new material that can conform to a weld cap and produce higher quality scan data for Ultrasonic Testing inspections

March 29, 2022

One of the biggest stumbling blocks to obtaining clear scan data when inspecting irregular or variable surface geometry is the ability of your probe to conform with the surface. Conformability can be obtained with a flexible delay line, bladder or wheel between the transducer and the inspected component. The coupling between the membrane and the component requires a small quantity of water or couplant.

The research and development team at Innovation Polymers have created a new elastomer (ACE 200). The new formulation enhances the conformability as well as the ultrasonic properties of the material. This new material can now easily conform to irregular shapes, which includes processing into flat sheets, bladders or wheels and other custom configurations based on customer specific designs.

Test Data

Acoustic Velocity (@ 20°C):

1531 m/s

Density:

900 kg/m²

Acoustic Impedance:

1.38 MRayIs

Attenuation (@ 5 MHz):

0.58 dB/mm

Innovation Polymers would like to announce the release of ACE 200.

Shore A Hardness of 20
Upgraded conformability characteristics from traditional ACE 400 polymer
Better attenuation (0.58 dB/mm)
An excellent balance of rigidity and comformability to optimize it’s Ultrasonic Testing application

About Innovation Polymers:

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New Conformable Delay Line for Flat, Convex and Concave Surfaces

cdurkin — Tue, 02 Nov 2021 14:58:19 +0000

Innovation Polymers announces a new conformable delay line with a stabilizing holder

April 29, 2021

Ultrasonic thickness testing is probably one of the simplest and most common applications of ultrasonic technology. However, it can be frustrating trying to get a steady signal when the surface is rough or not flat. Innovation Polymers now provides a conformable delay line in a 3-legged holder that can improve the stability of thickness readings.

The research and development team at Innovation Polymers has combined their conformable elastomers with a delay line that has a spherical tip housed inside a 3-legged stabilizer that is threaded to match the most popular probe designs.

Threaded to match popular probe designs
3-legged stabilizer
Selectable conforming materials
Spherical tip

With a 3-legged durable plastic holder design, the delay line holder can adapt to a range of both concave and convex surfaces.
Allows for a range of materials and hardness of low attenuation elastomers.
Pressing the assembly against the test piece compresses the delay line until the three legs stop the compression and provide a steady signal.
The spherical tip helps eliminate air from the couplant at the point of contact and conforms to the test surface shape (flat, convex or concave).
Single 14mm diameter delay line is used with options for several probe housing thread sizes (11/6″ – 32 TPI, 11/16″ – 24 TPI and 5/8″ – 24 TPI).
Delay line length allows for measuring thickness of steel up to 75 mm.

Examples of A-scans using a 5 MHz probe and ACE delay-line

High acoustic impedance difference produces a large interface signal

Polymer materials like polymethyl methacrylate (PMMA) have lower acoustic impedance than steel and provide a lower amplitude surface signal.

High Density PolyEthylene (HDPE) has an acoustic impedance of 2.45 MRayIs compared to 1.37 MRayIs for ACE. This results in the low interface signal. Less than half the amplitude of the air-backed backwall signal.

About Innovation Polymers:

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A Clear Signal for Clean Aerospace Inspections

cdurkin — Tue, 02 Nov 2021 14:50:10 +0000

NDT Couplant Saves Time and Material Costs when Inspecting Composite Materials

February 2021

Using traditional acrylic materials for aircraft inspections can have a tendency to cause issues that ultimately end up costing you time and accuracy. Some examples of this might be maintaining coupling between your probe and the part, issues with the delay scuffing the surface of the part, and the mess of gel cleanup afterward. These examples are just referencing the easy-to-reach portions of the aircraft without even mentioning the inverted inspections under wing and the belly.

“When I first switched to Aqualene, it was a night and day difference.” says Brandon Phillips, NDT Technician (Level III) FAA: DAR-F. “The acoustical characteristics allowed me to decrease the pulser and gain, significantly improving the signal to noise ratio in my inspections for an out-of-autoclave composite aircraft company. Improving the signal to noise ratio decreased my evaluation time by filtering out a lot of hash or transient signals in the scan data.”

When I first switched to Aqualene, it was a night and day difference.

– Brandon Phillips,
NDT Level III

Using Aqualene as a coupling solution for aircraft inspections allows you to add these savings to your inspections:

Consumable material by switching from gel to tap water,
time performing your inspections,
time evaluating the data,
and time cleaning up.

It's been a significant impact for something so simple.” says Phillips. “A light mist of tap water works just as well if not better for wetting the part and maintaining coupling. This also makes the Aqualene plugs excellent for inverted inspections (like under a wing or belly of an aircraft) and automated contact systems.”

Brandon Phillips

NDT Level III

About Innovation Polymers:

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New Elastomeric Wedge Design Improves Phased Array Sectorial Scanning of HDPE Butt Fusion Joints

cdurkin — Mon, 13 Jan 2020 11:22:38 +0000

In a Small Footprint that Easily Adapts to your Scanning System

High Density Polyethylene (HDPE) pipe is used in applications such as slurry transfer lines, water mains, natural gas mains, sewer mains, and fire system supply lines. In addition, HDPE pipe is used to transport cooling water for both non-safety and safety-related applications in nuclear power plants.

To address the inspection of butt fusion joints in HDPE using pulse-echo phased-array or TOFD, ASME Boiler and Pressure Vessel Code Section V Article 4 introduced Mandatory Appendix X in 2015. In 2016 ASTM introduced a similar document, Standard Practice 3044/E3044M – 16 Standard Practice for Ultrasonic Testing of Polyethylene Butt Fusion Joints.

A new ASTM International practice provides a standardized way for manufacturers and construction professionals to examine plastic pipe joints using sound waves. The new standard (E044/E3044M, Practice for Ultrasonic Testing of Polyethylene Butt Fusion Joints) provides a non-destructive way to identify flaws inside the pipe’s butt-fusion joints and to assess the joint’s overall quality.
- e-Journal of Nondestructive Testing (NDT) ISSN 1435-4934 (NDT.net Journal)

Recently, Innovation Polymers in partnership with the Materials Research Institute has developed an innovative design that incorporates a damping material with a low velocity refracting wedge for pulse-echo testing. Until a suitable damping material and processing technique was developed, the advantage of forward refraction from Aqualink (a low acoustic velocity and low attenuation elastomer which Innovation Polymers currently supplies for other customized NDT applications) could not be fully optimised.

The new design overcomes issues commonly associated with the existing options such as negative refraction when using hard plastics such as Rexolite and large footprints limiting close approach when using water membrane designs.

With Aqualink we have a great advantage because we can use the upper most refracted angles at around 85° - 89°. Being able to steer to such high angles allows us to detect flaws near the top of the weld. In steel, we would have to rely on a reflection from the opposite surface to have the beam bounce up to the top again. But with HDPE being so attenuative, this would result in very weak signals.

- Ed Ginzel, Materials Research Institute

Using this design technique, Innovation Polymers has been able to produce wedges that integrate with a number of widely used phased-array probes within the ultrasonic nondestructive testing industry.

About Innovation Polymers:

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Advanced Ultrasonic Couplant for Long Term Probe Placement

cdurkin — Mon, 13 Jan 2020 11:22:22 +0000

June 11, 2019

Applications exist where ultrasonic probes are required to be in place for long periods of time, sometimes in relatively extreme conditions. Typically, ultrasonic corrosion monitoring and ultrasonic flow metering place probes on a surface and take readings on a continuous or periodic basis. Water soluble gels eventually dry and the coupling effect is reduced and then lost.

Innovation Polymers has developed a new ultrasonic coupling that permits long term probe placement without significant coupling losses. The material is a high viscosity liquid polymer with virtually no evaporation at normal working temperatures. The tacky texture makes it an effective pressure sensitive adhesive (i.e. it forms a bond when pressure is applied).

In addition to its longterm coupling capabilities, the new coupling is capable of supporting SH shear waves (i.e. it is a non-Newtonian viscous fluid). Because it is not water soluble, the coupling was selected for application in the North Sea at 300m below the surface. The North Sea application included successful performance demonstration at temperatures from 5°C to 50°C.

To demonstrate the longterm stability of the coupling, a test was configured that coupled a 5MHz compression mode probe and a 5MHz SH shear wave probe to a 9mm thick plate of aluminum.

For the compression mode probe, the A-scan was gated to display two thickness multiples, whereas for the SH shear wave probe, only a single backwall was gated. Over a four-week period, the only significant shift was seen to occur after Day 1 where the thickness of the coupling had gradually reduced to a steady state. Subsequent measurements indicated less than 1 dB variation from the average peak value for both compression and shear modes.

At the time of the initial introduction of AquaBond, the test period was 30 days with the only significant change being at the transition from Day 1 as the thickness of the very viscous coupling thinned to a steady state. The test continued and 120 days after the test started, the results showed no signs of instability or change. Both the compression mode and shear mode signals remained constant.

Some suggested applications of AquaBond:

Clamp-on ultrasonic flow-meters
Longterm probe-to-wedge coupling (i.e. automated systems)
Underwater shear-wave stress testing
Longterm corrosion monitoring
Outdoor applications where weathering could remove water soluble gels

Note: Because the liquid is not water soluble, its removal is made possible with a cloth dampened with naphtha or mineral spirits.

Because the liquid polymer is highly viscous, its application is best made by spreading it onto the probe surface with a knife like blade. Pre-heating to about 40°C helps reduce viscosity for application.

Property	Value	Unit
Specific Gravity	0.91 g/cc	g/cc
Viscosity	*190 000	cps (centipoises)
Appearance	Clear amber liquid	N/A
Flash Point	150 (COC method)	°C
Glass Transition Temperature	-18	°C

* approximate value at 55°C. Note: for comparison, thick molasses is about 10 000 cps and peanut butter is about 150 000 cps.

AquaBond is available from Innovation Polymers in 2 or 8 oz jars.

About Innovation Polymers:

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Introduction of the Multiple Angle TOFD Wedge

cdurkin — Mon, 13 Jan 2020 10:41:00 +0000

This new wedge has been created for ultrasonic testing of High Density Poly Ethylene (HDPE) pipe

High Density Poly Ethylene (HDPE) pipe is now a popular substitute for steel pipe. Varieties of HDPE used in industry have an acoustic velocity range from ≈ 2100 m/s to ≈ 2600 m/s. Using PMMA or polystyrene as a refracting wedge material could result in very little to negative refraction. Elastomeric materials designed by Innovation Polymers range from ≈ 1025 m/s to ≈ 1600 m/s, ensuring positive refraction for all applications on polyethylene.

Innovation Polymers has designed wedges specifically for TOFD applications on HDPE. Interchangeable plugs made from Aqualene, ACE and Aqualink permit the user to select a refracted angle option best suited for the TOFD inspection at hand. These wedges are primarily intended for TOFD inspection of HDPE butt fusion joints. The modular concept of a standard housing, replaceable plug inserts and a threaded plate to accommodate different sized probes up to 12.5 mm (0.5 inches) diameter.

Standard plugs are available in Aqualene, ACE and Aqualink.

Standard plates are anodized aluminum with 3/8-32 or 11/16-24 threaded opening for probes.

Standard incident angle is 35° on a flat contact surface.

Polymer	Aqualene 300 Refracted Angle (°)	ACE 400 Refracted Angle (°)	Aqualink 100 Refracted Angle (°)
Velocity (m/s)	1590 m/s	1540 m/s	1480 m/s
2000	46	48	51
2100	49	51	54
2200	53	55	58
2300	56	59	63
2400	60	63	68
2500	65	69	76
2600	70	76	Internal Refraction

Plug options on HDPE with acoustic velocity 2400 m/s

The flat wedge design with the soft polymer plugs allows the wedge to form to radii as low as 3″ OD. Radiused wedges are available as a special order.

The standard materials provide refracted angles based on the polymer tested. Use determines the best plug material based on the polymer tested, its thickness, and the Probe Centre Spacing (PCS) for the desired depth of the beam crossing point.

Supplied with irrigation nozzles
Custom modifications are available
Different incident angles available
Threaded probe-plates and curvatures can be added

About Innovation Polymers:

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