Hydrostatic stress

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

Applying x-ray microscopy and finite element modeling to identify the mechanism of stress-assisted void growth in through-silicon vias

Abstract: Fabricating through-silicon vias (TSVs) is challenging, especially for conformally filled TSVs, often hampered by the seam line and void inside the TSVs. Stress-assisted void growth in TSVs has been studied by finite element stress modeling and x-ray computed tomography (XCT). Because x-ray imaging does not require TSVs to be physically cross-sectioned, the same TSV can be imaged before and after annealing. Using 8 keV laboratory-based XCT, voids formed during copper electroplating are observed in as-deposited samples and void growth is observed at the void location after annealing. We hypothesize that the mechanism generating voids is hydrostatic stress-assisted void growth. Stresses in a copper-filled TSV with a pre-existing void were simulated by finite element methods. The peaks of the hydrostatic stress and its gradient are shown to be around the edge of the void. Comparing simulated results and experimental data shows that void growth in TSVs is stress-assisted: vacancies diffuse and coalesce at the void as a result of the hydrostatic stress gradient.

Stress field induced by swift heavy ion irradiation in cubic yttria stabilized zirconia

Abstract: X-ray diffraction (XRD) was used to investigate the damage and the correlated stress induced by the slowing down of swift heavy ions in cubic zirconia polycrystals doped with 10 mol % Y2O3. Samples were irradiated at room temperature with 940 MeV Pb ions at fluences ranging from 5×1011 to 4×1013 cm−2. Changes of XRD profiles were examined at increasing fluences. Residual macroscopic stresses induced by irradiation were determined using XRD by the “sin2 ψ method.” The state of stress in the irradiated layer was described by a combination of: (i) a hydrostatic stress caused by the formation of damaged tracks leading to swelling and (ii) a biaxial stress imposed by the bulk undamaged material, which controls the lateral expansion of the surface damaged layer. The evolution of the stress as a function of irradiation fluence was also determined: the intensity of the hydrostatic stress increases from 80 to 460 MPa when the fluence is increased from 5×1011 to 4×1013 cm−2 and that of the biaxial stress increases ...

Influence of axial stress and dilatancy on rock tunnel stability

Abstract: In many existing elastoplastic plane-strain solutions for a circular tunnel excavated in a homogeneous, isotropic rock mass under a hydrostatic stress field, the longitudinal axial stress (or the out-of-plane stress) {sigma}{sub z} is not correctly evaluated. This paper describes the concepts and a numerical method to calculate this stress component and proposes analytical solutions for practical applications. The computed numerical solutions are compared with theoretical solutions where possible. The relations between rock-mass dilatancy, tunnel displacements, and the in-situ stress field are investigated. Mohr-Coulomb and Hoek-Brown yield criteria with appropriate plastic potential functions and nonassociated flow rules are used in the brittle plastic calculations. The effects of various boundary conditions on the numerical analyses are discussed and several important practical conclusions are drawn from the investigations.

Slip-line field solutions for three-point notch-bend specimens

Abstract: The slip-line field solutions for three-point bend specimens are reviewed for both deep and shallow notches. Plastic constraint factors, hydrostatic stress at the notch root and rotation constant to enable the crack upp opening displacement to be determined are given for a wide range of notch geometries. These values can be used in the fracture analysis of low strength metal specimens.