00:53 Jul-06-1999 X. Chen Student Institute of Biomedical Engineering, China, Joined Oct 1999 1
Need help in inspecting the bond condition of a composite material, which is four layers. From the top to the bottom, they are steel in 8-10mm thick, hard rubber in 4-5mm thick, 0.5mm envelop and substrate. We need to test the bond condiction of bond I (between the steel and the hard rubber) and bond II (between the hard rubber and the envelop). Usually the bond I can be detected easily. But the bond II has some difficulties.
Dose anyone know of a ultrasonic system that will allow us to inspect the bond I and II?
If anyone know some ultrasonic articles about this, also let me know please! thanks!
02:22 Jul-06-1999 Richard Freemantle NDT Inspector, Consultant, R&D Wavelength NDT Limited, United Kingdom, Joined Nov 1998 15
Re: bond inspection Hi,
The second interface will be difficult. We have some experience of detecting bond II disbonding steel automotive structures but the dimensions are very different to the ones you have stated. I think the main problem for a time domain pulse method will be the strong reflection coefficient at the steel rubber interface and the signal loss through the rubber. This makes it very difficult to distinguish echoes which have interfacted with the second bondline at the rubber-envelope interface.
Lower frequency resonance techniques may offer a practical solution. A lot of theoretical work on mode 1 resonance technqiues has been done at Imperial College London. This is based on detecting the through bond resonances of the joint which will shift in frequency when delaminations are present.
You don't mention what the envelope and substrate material is - this will have an impact on the strength of resonance or time domain signals.
I will try and dig out some references and email them to you.
You could try contacting the imperial college group via their web site http://babbage.me.ic.ac.uk/dynamics/ndt/ndt.html
: Need help in inspecting the bond condition of a composite material, which is four : layers. From the top to the bottom, they are steel in 8-10mm thick, hard rubber in : 4-5mm thick, 0.5mm envelop and substrate. We need to test the bond condiction of bond I : (between the steel and the hard rubber) and bond II (between the hard rubber and the : envelop). Usually the bond I can be detected easily. But the bond II has some : difficulties.
: Dose anyone know of a ultrasonic system that will allow us to inspect the bond I and II?
: If anyone know some ultrasonic articles about this, also let me know please! : thanks!
03:38 Jul-07-1999 Linas Svilainis R & D, Kaunas University of Technology, Lithuania, Joined Nov 1998 66
Re: bond inspection I think main problem is not only a system, but a method too. Yes, rubber layer will attenuate the signal and it will be hard to detect bond II, but I believe the differential signal extraction (DSE) procedure we've developed(http://www.ultrasonics.ktu.lt/delamin.htm) should work for bond II signal extraction. Publication: 1.R.Kazys, L.Svilainis. Ultrasonic detection and characterization of delaminations in thin composite plates using signal processing techniques. Ultrasonics, 1997, Vol.35, No.5, p.367-383 2.http://www.ultrasonics.ktu.lt/c26_1a.htm#2 3.R. Kazys, L. Mazeika, R.Sliteris, A. Voleisis. Ultrasonic NDT system of journal bearings. Proceedings of the XVI Conference of NDT of metalworks, Sankt Peterburg,1998, p.207-211.
Imaging for lossy materials(abstract): http://www.ultrasonics.ktu.lt/c28_2a.htm#1
Acquisition system configuration will depend on test conditions and the method used. For laboratory use we can offer our acquisition system IZOGRAF(http://www.ultrasonics.ktu.lt/izogr.htm) DSE is one of the signal post-processing procedures included. Or we can can inspect your sample for such possibility.
Re: bond inspection I think we can help you. We manufacture new bond tester BT-C. BT-C is a multimode instrument offering: Resonance, Pitch/Catch, Mechanical Impedance Analysis and C-image reconstructing. General description of BT-C you can find at our Internet-page: www.votum.md
If you send us a sample, we can answer all your question concerning inspection of bond II.
Re: bond inspection I have had good results in inspecting multilayer systems using a pitch-catch method. The transducers would be set up to generate 45 deg shear in the steel. This would generate roughly a 20 degree longitudinal wave in the rubber (depending on acoustic properties). Set up pitch-catch system to geometrically focus on the bond line of interest. The transmitter should also be a focused transducer that is focused on the bond line. The angled geometry removes most of the reflections from layers that are not of interest. Of course, you cannot see a bond if the bond above it is unbonded. For a thin layer, focus on the surface below the bond. Then you are looking at a signal that has traveled through the bond and back so that the signal is lost (rather than just changed amplitude) when there is no bond.