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Putting the stone cutting industry on a solid foundation

 

What good are neutrons to the EU stone-cutting industry?


In breakthrough applied research, the Institut Laue Langevin (ILL) and the Institute of Physics of the ASCR Prague have collaborated within the European Pro-Stone project to apply advanced neutron scattering techniques to aid the EU stone-cutting industry compete internationally. Using the unique capabilities of the advanced neutron strain scanner at the ILL, the researchers designed steel stone-cutting disks that use smart alloy inserts to control stress in the disks. The result is better stone-cutting tools for the EU stone-cutting industry—a big boost to the EU economy from some small particles.

The European stone production industry, accounting for over 500,000 EU jobs, has been under threat by cheaper international competition. In support of the threatened industry, the EU launched project “Pro-Stone”. The project aims to boost the efficiency of stone-cutting tools by exploiting advanced materials technologies to improve tool performance and lifetime.

During service, steel cutting discs are subjected to elevated temperatures and high, inhomogeneous stress fields. The applied stresses combine with the inherent residual stresses in the disc to cause fatigue and crack propagation. The novel solution found by the ILL-ASCR-ILL researchers is to incorporate into the steel cutting disc smart alloy inserts that activate when the disc reaches the appropriate operating temperature. At a given temperature the smart alloy inserts switch on, imparting a large, compressive, residual stress close to the cutting edge, protecting against crack growth and metal fatigue. Smart alloys offer the advantage of the shape memory effect, whereby a previous shape for a given activation temperature is recalled. This phenomenon is based on a reversible austenite-martensite phase transformation.
 
Using the advanced neutron strain scanner at the ILL, the ILL-ASCR collaboration studied stress changes around NiTi inserts in steel plates [2, 3]. Neutron strain scanning is particularly applicable to measuring the three-dimensional stress state in metallic components, and the high-flux ILL reactor enables rapid and precise measurements. The ILL-ASCR collaboration began by measuring the stress state at ambient temperatures. Subsequently, using in-situ procedures, the steel matrix and its NiTi inserts were heated to 130 °C (which is beyond the insert activation temperature), following which the new stress state was investigated (see figure below). The results show that the NiTi inserts trigger a dramatic change in the stress experienced by the steel matrix.

This is the first time that in-situ stress changes in a steel matrix have been observed with such high resolution. The neutron strain scanning technique shows that, above the activation temperature, it is possible to trigger a dramatic change in the stress field of the steel cutting disc. Through careful placement of smart inserts in cutting discs, it is now possible to improve the performance and lifetime of stone-cutting tools, giving the EU stone-cutting industry a new competitive edge.





 

 

a) Change in macroscopic strain (perpendicular to the insert face) in the steel matrix measured using neutrons. At 130 °C, the smart inserts activate, causing a strong, beneficial, compressive strain. The process is fully reversible.
b) Placement of smarts inserts in a cutting disc.


[1] www.dappolonia-research.com/prostonecm/

[2] B. Malard, P. Šittner, J. Pilch, V. Davydov, E.C. Oliver. Stress distributions around active NiTi inserts in smart cutting discs. Highlight - ISIS Annual Report 2008
[3] V. Davydov, M. Vrána, P. Lukáš, B. Malard, J. Pilch and P. Šittner. Neutron diffraction study of stress distribution in steel sheet around active NiTi inserts. ICRS8, Denver, 2008

2009 :
B. Malard, J. Pilch, V. Davydov, P. Sittner – FZU Prague
D.J. Hughes and K. Konstantinidis – ILL Grenoble


If you would like more information about this topic, please contact:
Darren J Hughes, ILL



Collective project FP6
Title: Eco-efficient and high productive stone processing by multifunctional materials
Acronym PRO-STONE
Contract no.COOL-CT-2005-516417
Term: 2005-8


The PRO-STONE consortium consists of 25 partners including R&D centres, SMEs and the EUROROC stone industry association.