Hydrostatic stress

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

Molecular Dynamics Study on Grain Boundary Diffusion in Aluminum under Hydrostatic Stress.

Abstract: Fracture in an aluminum conductor of an LSI(large-scale integrated circuit) is often caused by stress-induced diffusion of atoms along a grain boundary, which is called"stress migration". As the conductor is subjected to tensile hydrostatic stress at a high temperature due to thermal mismatch, it is important to understand the effect of hydrostatic stress on the diffusion. However, this effect has not yet been examined since experiments under tensile hydrostatic stress are extremely difficult. In this study, the effect is investigated on the basis of a molecular dynamics simulation using the Nose-Hoover and the Parrinello-Rahman methods. The simulation enabled us to observe the motion of atoms under constant stress and temperature. The results obtained are summarized as follows. (1)The simulated coefficient of lattice diffusion under a stress-free condition agrees very well with the experimental ones. This indicates the validity of the present simulation. (2)The motion of atoms is accelerated by tensile hydrostatic stress in the region of about 5 atomic layers near the grain boundary. (3)Tensile hydrostatic stress accelerates the diffusion along the grain boundary, while compressive stress suppresses it. (4)The coefficient is proportional to exp(-(ΔE)/(k(T/Tm)))regardless of the magnitude of hydrostatic stress where T and Tm are the temperature and the melting temperature of the grain boundary under the corresponding hydrostatic stress, respectively.

Finite element analysis of the stress and deformation fields around the blunting crack tip

Abstract: The main object is to define the stress and deformation fields in a vicinity of a crack in an elasto-plastic power law hardening material under plane strain tensile loading. Hydrogen-enhanced localized plasticity (HELP) is recognized as an acceptable mechanism of hydrogen embrittlement and hydrogen-induced failure in materials. A possible way by which the HELP mechanism can bring about macroscopic material failure is through hydrogen-induced cracking. The distributions of the hydrostatic stress and plastic strain are simulated around the blunting hydrogen induced crack tip. The model of Sofronis and McMeeking is used in order to investigate the crack plasticity state. The approach is valid as long as small scale yielding conditions hold. Finite element analyses are employed to solve the boundary value problems of large strain elasto-plasticity in the vicinity of a blunting crack tip under mode I (tensile) plane-strain opening and small scale yielding conditions. Three different FEM softwares; MSC.Marc, ADVENTURE-Solid and ZeBuLoN are used for structural analysis and results are verified by the previous works. The aim is to compare the results of different rate equilibrium equations in the case of large deformation and large strain elasto-plastic analysis.

Finite element equilibrium analysis of creep using the mean value of the equivalent shear modulus

Abstract: The paper deals with the nonlinear creep analysis using equilibrium finite elements. In adopting a concept of the mean value of the equivalent shear modulus, a direct iterative procedure is proposed with the minimum calculation in the modification of the global stiffness matrix. The difficulties due to the incompressibility of the creep flow are overcome by a numerical artifice where the hydrostatic stress component is considered as a Lagrange parameter. Some numerical results are shown and compared with the analytical method.

Influence of carbon content on workability behavior in the formation of sintered plain carbon steel preforms

Abstract: Complete experimental investigation on the workability behavior of sintered plain carbon steel cylindrical preforms with carbon contents of 0%, 0.35%, 0.75%, and 1.1%, under cold upsetting, has been studied in order to understand the influence of carbon content on the workability process. The abovementioned powder metallurgy sintered preforms with constant initial theoretical density of 84% and aspect ratio of 0.4 were prepared using a suitable die set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1,200°C. Each sintered preform was cold upset under nil/no frictional constraint. Under triaxial stress state condition, densification, axial stress, hoop stress, hydrostatic stress, effective stress, and formability stress index against axial strain relationship were established and presented in this work. Further, attained density is considered to establish formability stress index and various stress ratio parameters’ behavior.