V Livescu

Publications (2)3.21 Total impact

• Source

  Available from: Bjorn Clausen

  Article: Design, implementation, and testing of a cryogenic loading capability on an engineering neutron diffractometer.

  T R Woodruff, V B Krishnan, B Clausen, T Sisneros, V Livescu, D W Brown, M A M Bourke, R Vaidyanathan
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  ABSTRACT: A novel capability was designed, implemented, and tested for in situ neutron diffraction measurements during loading at cryogenic temperatures on the spectrometer for materials research at temperature and stress at Los Alamos National Laboratory. This capability allowed for the application of dynamic compressive forces of up to 250 kN on standard samples controlled at temperatures between 300 and 90 K. The approach comprised of cooling thermally isolated compression platens that in turn conductively cooled the sample in an aluminum vacuum chamber which was nominally transparent to the incident and diffracted neutrons. The cooling/heat rate and final temperature were controlled by regulating the flow of liquid nitrogen in channels inside the platens that were connected through bellows to the mechanical actuator of the load frame and by heaters placed on the platens. Various performance parameters of this system are reported here. The system was used to investigate deformation in Ni-Ti-Fe shape memory alloys at cryogenic temperatures and preliminary results are presented.
  The Review of scientific instruments 06/2010; 81(6):063903. · 1.52 Impact Factor
• Article: In situ loading response of WC–Ni: Origins of toughness

  J.W. Paggett, A.D. Krawitz, E.F. Drake, M.A.M. Bourke, V. Livescu, B. Claussen, D.W. Brown
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  ABSTRACT: The strain response of WC and Ni in WC–Ni cemented carbide composites (5, 10 and 20 wt.% Ni) was studied under uniaxial compressive load to −2000 MPa using neutron diffraction. Measurements of elastic strain were made simultaneously in the axial and transverse directions of the samples, for both phases. Thermal residual stresses (TRS) were also measured, before and after loading. Ni plasticity was observed from the earliest load levels. The superposition of tensile Poisson strain (in the transverse direction) on pre-existing tensile Ni strain due to TRS produces anisotropic yielding in binder regions. Yielding is progressive with applied strain, leading to a reversal of transverse binder strain, and anisotropic relaxation of the TRS. The effect is greatest for 20 wt.% Ni, where Ni constraint is much less than for 5 wt.% Ni. These results provide a quantitative basis for the mechanical origins of the toughness of cemented carbide composites.
  International Journal of Refractory Metals and Hard Materials 24:122-128. · 1.69 Impact Factor