Wallner lines

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Wallner lines or Wallner's lines are undulating interference lines that form on the surface of the crack as the crack propagates in isotropic materials (such as glass). The physicist Helmut Wallner (1910–1984) first described these lines in 1939 in the Zeitschrift für Physik . He documented it during the investigation of the bending behavior of glass rods, which he carried out in 1938 at Adolf G. Smekal's Institute of Materials Science in Halle.

description

Wallner lines arise "through the interaction of the primary breaking process with elastic disturbance waves that are triggered at notches in the glass". The speed of propagation of the interfering waves is greater than that of the primary crack front. Using the Wallner lines, it is possible to determine the speed of crack propagation in the material. Wallner lines on broken glass include forensic technology to the technical form traces and analyzed by standard methods today. More recent research has looked at Wallner's lines for other isotropic materials, for example polymers , epoxy resins , tungsten or carbon-filled rubber.

Use of the term in archeology

Even with stone tools made of obsidian or very fine-grained flint , Wallner lines can appear on the ventral surface of tees . However, these are not identical to the crack front waves, called impact waves or wave rings in the case of chipped stones , which spread out exactly concentrically from the primary impulse of the crack and are usually easy to see. Here Frank Kerkhof and Hansjürgen Müller-Beck took the view that the origin of fracture-defining elastic impulses in the production of tees often lies vertically above the fracture surface, therefore the fracture front and Wallner lines are identical. In this generalized sense, the impact waves on the tees should also be viewed as Wallner lines. This generalization is not shared by other archaeologists, especially in the English-speaking world.

literature

  • Helmut Wallner: Line structures on fracture surfaces. In: Journal of Physics. 114, 1939, pp. 368-378. doi: 10.1007 / BF01337002

Web links

Individual evidence

  1. ^ A. Rabinovitch, V. Frid, D. Bahat: Wallner lines revisited. In: Journal of Applied Physics. 99, 2006, p. 076102, doi: 10.1063 / 1.2181692 .
  2. ^ Andreas Momber: The materials scientist Adolf G. Smekal 1895-1959. In: Research in Engineering. Volume 70, No. 2, 2005, pp. 114-119 doi: 10.1007 / s10010-005-0020-2
  3. ↑ Wallner 1939, p. 368.
  4. ↑ Glass Fractures (PDF) Website of the Scientific Working Group for Materials Analysis (SWGMAT) of the FBI (accessed February 3, 2016)
  5. ↑ K. Ravi-Chandar: Dynamic fracture . Elsevier, 2004, ISBN 0-08-044352-4 .
  6. ↑ Jürgen Hertling: Propagation speed of unstable cracks in polymers at low temperatures. Institute for Materials Research. Karlsruhe, Univ., Diss .; 1999
  7. ↑ Frank Kerkhof, Hansjürgen Müller-Beck: On the fracture-mechanical interpretation of the impact marks on stone tools. In: Glass technical reports. Volume 42, 1969, pp. 439-448.
  8. ^ A b B. Cotterell, J. Kamminga: The mechanics of flaking. In: B. Hayden (Ed.): Lithic Use-Wear Analysis. Academic Press, New York 1979, pp. 97-112.
  9. ↑ Frank Kerkhof, Hansjürgen Müller-Beck: On the fracture-mechanical interpretation of the impact marks on stone tools. In: Glass technical reports. Volume 42, 1969, p. 448.
  10. ^ Wallner lines. In: George H. Odell: Lithic Analysis. (= Manuals in Archaeological Method, Theory and Technique ). Springer, 2004, ISBN 1-4419-9009-7 , pp. 55-56. doi: 10.1007 / 978-1-4419-9009-9