Hydrostatic stress

About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.

Strain Directed Assembly of Nanoparticle Arrays Within a Semiconductor

Abstract: The use of strain to direct the assembly of nanoparticle arrays in a semiconductor is investigated experimentally and theoretically. The process uses crystal strain produced by a surface structure and variations in layer composition to guide the formation of arsenic precipitates in a GaAs-based structure grown at low temperature by molecular beam epitaxy. Remarkable patterning effects, including the formation of single and double one-dimensional arrays with completely clear fields are achieved for particles in the 10-nm size regime at a depth of about 50-nm from the semiconductor surface. Experimental results on the time dependence of the strain patterning indicates that strain controls the late stage of the coarsening process, rather than the precipitate nucleation. Comparison of the observed particle distributions with theoretical calculations of the stress and strain distributions reveals that the precipitates form in regions of maximum strain energy, rather than near extremum points of hydrostatic stress or dilatation strain. It is therefore concluded that the patterning results from modulus differences between the particle and matrix materials rather than from other strain related effects. The results presented here should be useful for extending strain directed assembly to other materials systems and to other configurations of particles.

Finite element formulation for shear modulus reconstruction in transient elastography

Abstract: In order to image the shear modulus in soft tissue, for medical diagnosis, given one component of measured displacements as a function of time on an imaging plane, two related direct finite element-based inversion algorithms are presented. One algorithm is based on the governing equations expressed in the frequency domain, and the other is in the time domain. The algorithms consider the complete equations of isotropic, small deformation, elasto-dynamics, where the hydrostatic stress is also treated as an unknown. The algorithms reconstruct both the shear modulus and hydrostatic stress fields, and regularization is used to stabilize the hydrostatic stress recovery. An algorithm is also developed for reconstructing the second displacement component, while simultaneous finding a smooth approximation to the measured displacement component to reduce noise. Shear modulus reconstruction results from both algorithms, using experimental ultrasound measurements on a tissue-mimicking phantom, are presented, and the ...

Mechanical behaviour of transversely isotropic porous neo-hookean solids

Abstract: In this paper, the mechanical responses of a recently developed hyperelastic model for the neo-Hookean solids with aligned continuous cylindrical pores under finite homogeneous deformation that can capture the anisotropic compressibility as well as the coupling between the volumetric and deviatoric behaviours are examined. To this end, the strain energy function of this hyperelastic compressible transversely isotropic model contains terms for the coupling of volumetric and deviatoric behaviours. It is shown that, the asymptotic response of this anisotropic compressible model under extreme loading situations is considerably different from that of incompressible models. The unstable behaviour of the porous solid under hydrostatic stress/strain loadings is discussed in detail. When a general simple 2D shear deformation is applied to this porous solid in i1 – i2 plane, the normal stress in the third axial direction (i3) is nonzero. The loss of monotonicity of the stress tensor under off-axis simple 2D shear loading is demonstrated as well.