where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
Technical Discussions
05:58 Jun-01-2009
direction control of guided waves

Could anybody help me solve the problem with direction control of guided waves?

In my research, I need to control guided waves, torsional waves, to propagate in a single direction, that is unidirectional propagation, I know that it can be carried out when arranging two coils which have an interval of 1/4 wavelength of guided waves, but I can't get detailed information about it, especially electrocircuit design such as phase shift circuit.

I have searched for many ariticles, but rarely related information could be gotten, can anybody help me solve this problem? or advise some articles?

Thank you!

Sang Kim
Consultant, NDT Trainer
Guided Wave Analysis LLC, USA, Joined Feb 2008, 44

Sang Kim

Consultant, NDT Trainer
Guided Wave Analysis LLC,
Joined Feb 2008
23:59 Jun-02-2009
Re: direction control of guided waves
In Reply to talortang at 05:58 Jun-01-2009 (Opening).

You can do direction control of guided wave with two or multiple probes and time-delaying circuit. Follow this procedure for controlling the direction of guided wave:
1) Find the velocity of torsional wave mode in the applied material; The torsional mode velocity is about 3250 m/sec in steel. The fundamental torsional mode velocity is the same to shear wave velocity of the material.
2) Decide the operating frequency of your wave such as 128 kHz.
3) Calculate the wavelength with the velocity and frequency. In this example, it is about 1 inch.
4) Calculate ¼ of wavelength of the wave. It is 0.25 inch.
5) Install two probes in 0.25 inch of center-to-center separation
6) For transmitting the guided wave, make electric circuit so that the transmitters trigger the high-power electric currents with a delay of ¼ period to each other. In this example, 1/(4*128000) sec
7) For receiving the guided wave, make electric circuit that can add the two signals after delaying ¼ of period from each other.
8) For good direction control, you need two transmitters and two receivers.
9) If you use multiple probes, you will have better direction-controlled signal.

If you need simple test in the lab for a paper, try to use one probe that is bonded at ¼ wavelength separation (The center of probe should be ¼ wavelength separation from the edge of specimen) from the end of specimen such as pipe or plate. Then you will have perfect direction-controlled signal with only one channel equipment.

For more information about long-range ultrasonic testing (LRUT) using guided wave, please refer to this website (www.gwanalysis.com) or email me.


10:46 Jun-08-2009
Re: direction control of guided waves
In Reply to Sang Kim at 23:59 Jun-02-2009 .

Thanks! I don't need simple test in the lab for a paper, but long time and deeply research for controlling the direction of guided wave.
I have known the procedure for controlling the direction of guided wave, and I have painted the figures of vibration of two particles in one period ,which stand for two transmite coils bonded at 1/4 wavelength separation and delaying 1/4 of period from each other.
But unfortunately, I don't know how to upload the figures to forum, so, I have to e-mail to you with the figures.
I have two problems with the procedure.
1)when the vibration direction of two particles ,which stand for two probes installed at 1/4 wavelength of center-to-center separation, are the same or the converse, we get different results when two waves compound,as the figures show. which one should I choose? It seems that we can get pure direction-controlling when the vibration direction of two particles are the converse,but the amplitude of first half-period wave is half of the amplitude of second half-period wave, this wave may affect our test result. However, we can't get ture direction-controlling when vibration direction of two particles are the same. In one direction, we get half-period wave; in another direction, we get one period wave, which amplitude is two times as the half-period wave.
So, should I choose the converse one? Then how to avoid the affect as a result of different amplitude of the first half-period and the second half-period? or whether it will affect the test result?
2)for good direction contorl, I know two transitters are necessary, but why we need two receivers, too? when we use two transitters installed as you said in your message, we can control guided waves to propagate in a single direction, then receiving the single-dierction guided waves, one receiver is enough, why do we need two receivers? You said it is for good direction control, could you explain it in details?


Product Spotlight

On-Demand Webinar: Advanced Ultrasonic Techniques for HTHA Detection & Assessment

In the Oil and Gas industry, High Temperature Hydrogen Attack (HTHA) can occur in steels operating a
t high temperature, usually above 205°C (400°F). Early stages of HTHA are very difficult to detect. Join us for a webinar presented by Guy Maes, Zetec Sales Engineer Director. The webinar will demonstrate how advanced ultrasonic techniques are deployed for efficient and reliable HTHA inspections.

GEKKO, Standard and Advanced phased-array for Easier inspection

M2M Gekko® is a field-proven flaw detector offering PAUT, UT, TOFD and TFM through the streamline
d user interface Capture™. Released in 32:128, 64:64 or 64:128 channel configurations, Gekko combines high- resolution and speed while reducing inspectors’ training time.

Semi-Automated Phased Array Immersion System for Small Composite Parts

Turn-key semi-automated system as an improved and affordable solution for inspection of small comp
osite parts. Includes support table, immersion tank, scanner, PA instrument, PC, Analysis software, database, wedge management and other options.

Immersion systems

ScanMaster ultrasonic immersion systems are designed for high throughput, multi shift operation in a
n industrial or lab environment. These fully integrated systems provide various scanning configurations and incorporate conventional and phased arrays technologies to support diverse applications, such as inspection of disks, bars, shafts, billets and plates. All of ScanMaster immersion systems are built from high accuracy scanning frames allowing for scanning of complex parts and include a multi-channel ultrasonic instrument with exceptional performance. The systems are approved by all major manufacturers for C-scan inspection of jet engine forged discs. Together with a comprehensive set of software modules these flexible series of systems provide the customer with the best price performance solutions.

We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
this is debug window