Hydrostatic stress

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

Nature Inspired Strategy to Enhance Mechanical Properties via Liquid Reinforcement

Abstract: Solid-solid interface mechanism understanding of composite inclusions, when extended to solid-liquid interface design of composite using Eshelby theory, indicates a possibility of decreasing effective stiffness with increasing liquid inclusion in a solid matrix. In contrast, experimental evidence in the current paper suggests high stiffness and enhanced dynamic energy absorption in a soft polymer (polydimethylsiloxane) with high bulk modulus liquid inclusions (gallium). The basic deformation mechanism is governed by hydrostatic stress causing shape change of the liquid inclusion in large deformation regime and strain hardening of a soft polymer matrix. In addition, dynamic viscoelasticity and fluid motion also play a significant role. These understandings are developed here based on analytical modeling and a detailed finite element with smooth particle hydrodynamic simulations. The large deformation with viscoelasticity of gallium composite shows higher energy absorption and dissipation. Similar strategies of liquid reinforcement to compliant solid matrices are abundant in nature, for example, the intervertebral discs in the spinal cord and deep sea animal skin and lungs.

Nondestructive Measurement of the Residual Stresses in Copper Through-Silicon Vias Using Synchrotron-Based Microbeam X-Ray Diffraction

Abstract: In this paper, we report a new method for achieving depth resolved determination of the full stress tensor in buried Cu through-silicon vias (TSVs), using a synchrotron-based X-ray microdiffraction technique. Two adjacent Cu TSVs were analyzed; one capped with SiO2 (0.17 \(\mu \) m) and the other without. The uncapped Cu TSV was found to have higher stresses with an average hydrostatic stress value of \(145\pm 37\) MPa, as compared with the capped Cu TSV, which had a value of \(89\pm 28\) MPa. Finite element-based parametric analyses of the effect of cap thickness on TSV stress were also performed. The differences in the stresses in the adjacent Cu TSVs were attributed to their microstructural differences and not to the presence of a cap layer. Based on the experimentally determined stresses, the stresses in the surrounding Si for both Cu TSVs were calculated and the FinFET keep-out-zone (KOZ) from the Cu TSV was estimated. The FinFET KOZ is influenced by the microstructural variations in their neighboring Cu TSVs, thus, it should be accounted for in KOZ design rules.

Failure Criteria for Glass-Fiber Reinforced Composites under Confining Pressure*

Abstract: An experimental study of glass-fiber mat laminates discloses the complexity of mechanical behavior of such composites, including pronounced anisotropy of the discontinuous type, very marked stress sign sensitivity, hydrostatic stress effects, and appearance of different failure modes. The Tsai and Wu criterion, which is widely used in engineering, is no longer adequate to predict properly the actual directional strengths of these materials. A new, more elaborate failure condition is proposed, which accounts for the different observed phenomena, predicts different failure modes, and proves to be reliable when compared with experimental data.