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The PPI value of open foams and its estimation using image analysis

  • Joachim Ohser , Claudia Redenbach and Ali Moghiseh
Published/Copyright: August 15, 2014
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International Journal of Materials Research
From the journal International Journal of Materials Research Volume 105 Issue 7

Abstract

The mean number of pores per inch (PPI value) is one of the most important geometric characteristics of cellular materials such as open or closed foams. It is defined as the number of pores (cells) along a straight test line related to the line length. Counting cells along a test line sounds very simple, but on the surface of an open foam specimen it is often hard to decide whether a cell hits the line or not. Thus, there exists no quick and safe method to estimate the PPI value from an optical image taken from the specimen's surface. In this article, we present a very efficient method of estimating the PPI value of foams from optical dark-field images of the surface of a foam sample. The method is based on the computation of the spectral density of the (two-dimensional) dark field images. It turns out that the radius of the first interference ring in the spectral density is proportional to the PPI value. The constant of proportionality can be determined from geometric models for open foams or analysis of three-dimensional images of foam samples. These techniques allow calibration of the estimation of the PPI value from the spectral density of two-dimensional dark field images.

Keywords: Open foam; Pore number; Image analysis; Optical measurements; Microtomography
*Correspondence address, Prof. Joachim Ohser, University of Applied Sciences, Dept. Math. & Nat. Sci., Schöfferstraße 3, D-64295 Darmstadt, Germany, Tel.: +49(0)6151 16 8655, Fax: +49(0)6151 16 8754, E-mail:

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Received: 2013-09-10
Accepted: 2013-11-26
Published Online: 2014-08-15
Published in Print: 2014-07-14

© 2014, Carl Hanser Verlag, München

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https://doi.org/10.3139/146.111051
Keywords for this article
Open foam; Pore number; Image analysis; Optical measurements; Microtomography

Articles in the same Issue

  1. Contents
  2. Contents
  3. Editorial
  4. Materials tomography is coming of age
  5. Original Contributions
  6. Microtomographic assessment of damage in P91 and E911 steels after long-term creep
  7. Imaging of nano-seeded nucleation in cement pastes by X-ray diffraction tomography
  8. High-speed in-situ tomography of liquid protein foams
  9. Imaging of hydrogen in steels using neutrons
  10. Characterization of multilayer structures in fiber reinforced polymer employing synchrotron and laboratory X-ray CT
  11. Ptychographic Fresnel coherent diffraction tomography at the nanoscale
  12. Materials research and non-destructive testing using neutron tomography methods
  13. The PPI value of open foams and its estimation using image analysis
  14. Combined use of micro computed tomography and histology to evaluate the regenerative capacity of bone grafting materials
  15. Assessing the grain structure of highly X-ray absorbing metallic alloys
  16. Microstructural analysis of a C/SiC ceramic based on the segmentation of X-ray phase contrast tomographic data
  17. People
  18. Prof. Dr. Dr. h. c. Lorenz Ratke on his 65th birthday
  19. DGM News
  20. DGM News
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