X-ray computed tomography and SEM are good methods to observe and quantify porosity in casting. But what are the other possible ways and method to find and measure porosity as casting defect.?
A very effective way to characterise the surface of a material is using non-contact 3D optical surface scanning which is based on laser triangulation. This approach enables you to measure and calculate numerous geometric parameters of a surface related to surface porosity regardless of the material it is made of. This method is very fast and precise and also allows complete reconstruction of a surface. Below, you can find my article with a short description of this method, I used for an asphalt surface characterisation, but the principle is mostly the same in the mechanical engineering and has numerous applications in many fields of industry.
You can also find more information on the following websites:
http://lmi3d.com/
http://lmi3d.com/products/technologies/3d-measurement
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You can try to measure the density and compare it to density without porosity the other method is one of the most common light microscope based metallographic investigation on polished samples.
@Miomir Miljković
thanks alot for your reply. and your idea seems to be very satisfying. can you tell me what equipment will be required because I think its almost similar to scanning electron microscope (SEM) being used for same purpose.
@Grzegorz Cios
@Medhat Awad El-Hadek
thanks alot for your response.
you are suggesting Archimedean porosimetry method to measure and compare densities. I am still looking if any researcher have tried this method on finding porosity in metals during casting process.
My research is based in porous titanium alloys for biomedical applications, and I realised that Achimedes test, Hellium picnometry, and geometric measurements of the sample, could be used to measure the porosity and all of them gave almost the same result, considering their errors. Measure porosity area in micrographs also works very well to. But if you wish to investigate the porous morphology, interconectivity and distribution in your sample, I have read that X-ray CT is best choice, but I didn't had acess to this techniche yet.
Dear Mr Hafeez,
The difference from SEM is that SEM uses electron beam, while the 3D optical measurement uses an emitter of a structured (usually having a typical fringe pattern) laser light projected on a whole field of view that is observed. The projection of the laser is recorded by a CCD camera. By this approach you get a surface height profile based on which you can calculate any relevant numerical parameter. The field of view in this method can range from few milometers to few tens of centimetres followed by a corresponding resolution. There ara also various sizes of the instruments, from those operated from a hand to those mounted on a vehicle. The measurement can give only information on geometry of a surface. You can go to the following website, login, and get better informed. For the beginning, you can also refer to the texture parameters defined in the standard ISO 25178.
http://downloads.lmi3d.com/node/971
Open porosity is usually measured with nitrogen adsorption or mercury porosimetry. Pore size distribution is obtained with both techniques. Closed porosity can be determined as difference from true porosity determined from mercury porosimetry measurements when mercury penetrated pores or helium pycnometry and theoretical density from XRD JCPDS cards by subtracting them. If these techniques are too sophisticated for sand, use the principals and penetrate the pores with smaller particles and calculate the usage ...