Hydrostatic stress

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

A full-field crystal plasticity study on how texture and grain structure influences hydrostatic stress in thermally strained β-Sn films

Abstract: The present study uses full-field thermo-mechanically coupled crystal plasticity to simulate the stress distribution in thermally strained β-Sn films to better understand the conditions causing the generally rare nucleation of whiskers from such films. Following the notion that stress-driven diffusion along the grain boundary network is leading to and supporting whisker formation, the goal is to identify critical factors of crystallographic and/or geometric nature that influence the hydrostatic stress in such films prior to the onset of actual whisker formation. Approximating the film as a periodic structure of around a hundred columnar grains on an isotropic substrate, the simulations reveal a strong spatial variation of hydrostatic stress over distances comparable to the grain size but without apparent long-range gradients, suggesting whisker nucleation to be a phenomenon that depends on specifics within a relatively small neighborhood of grains. Furthermore, neither the grain size distribution nor the presence of oblique surface grains alters the width of the stress distribution by much. In contrast, the variation of hydrostatic stress notably depends on the crystallographic texture of the film, where β-Sn films for which the film normal is aligned with ⟨ 0 0 1 ] show a narrower distribution than films with ⟨ 1 0 0 ] parallel to the normal. The former film texture, therefore, is predicted to be less prone to whisker formation than the latter.

The critical stress criterion for gaseous hydrogen embrittlement

Abstract: A criterion for susceptibility to hydrogen embrittlement based on the development of a critical hydrostatic stress has been proposed. The hydrostatic stress distribution ahead of plastically strained notches has been described analytically and correlated with measured susceptibility to hydrogen embrittlement. The predictions of the analysis are in good agreement with available experimental data and support the critical stress criterion for hydrogen embrittlement.

Numerical analysis of vacancy transport by residual stress in electromigration on LSI interconnects

Abstract: The Li multiplication method for the driving force induced particle migration equation was proposed to solve numerically the stress and electric fields induced vacancy migration equation. On the basis of this method, vacancy migration behaviors were found to be predicted under the competitive relationship between stress and electric field. When a residual stress is dominant, vacancies concentrate around the maximum hydrostatic stress region, such as elastic–plastic boundary. On the other hand, when the electric field is dominant, vacancies do not concentrate around the maximum hydrostatic stress region, but move from the cathode end to the anode end. An in situ observation of electromigration on AlCuSi interconnect was conducted to verify the simulation results. A void nucleated and grew at the tip of a notch on an AlCuSi line without passivation film, while many voids appeared and grew in cathode side in a line with passivation film. Greater hydrostatic stress gradient is considered to occur in the line without passivation film, owing to a small scale of yielding, and this leads to concentrate void formation at the tip of the notch. These results indicate that numerical analysis of electromigration is valid to represent the experimental result. Based on results mentioned above, various failure modes in interconnects cased by electromigration are predictable by the proposed Li multiplication method.