Terms Of Stress Variations Research Articles

Numerical Analysis of Residual Stresses Effect in Multi-materials

Background: In this study, the effect of mechanical and physical properties of the metal and temperature is highlighted. The purpose of this study is to analyze the effect of these stresses on multi-materials. This work aimed to conduct a three-dimensional numerical study by the finite element method on the levels and distributions of the stresses in the Al2O3/NI/HAYNES multi-materials. These stresses of thermal and mechanical origin are generally detrimental to the service life of multi-material. Methods: The use of numerical resolution by finite element method is the most suitable for complex mechanical problems. It allows a more in-depth analysis of all points of the structure. In this study, a fundamental tool was constructed to resolve the mechanical behavior of materials subjected to complex solicitations. Therefore, the ABAQUS calculation code version 6.14 was used to analyze the residual stresses. Results: By interpreting the results in terms of stress variation, we identified the areas at risk; in particular, the nature of a joint effect plays a decisive role in the assembly of the right material in its mechanical resistance. This nature is defined in terms of stiffness (Young's modulus) and differential expansion (coefficient of thermal expansion). Conclusion: The presence of strong residual stresses can constitute a risk of damage to several materials. The difference between the coefficients of thermal expansion of the two materials (metal and ceramic) linked together induces, in these two constituents, normal internal stresses. This difference determines the level and distribution of these constraints. Moreover, the sign of this difference determines the state of the normal stresses.

On the use of dislocations to model interseismic strain and stress build-up at intracontinental thrust faults

Creeping dislocations in an elastic half-space are commonly used to model interseismic deformation at subduction zones, and might also apply to major intracontinental thrust faults such as the Main Himalayan Thrust. Here, we compare such models with a more realistic 2-D finite element model that accounts for the mechanical layering of the continental lithosphere and surface processes, and that was found to fit all available constraints on interseismic and long-term surface displacements. These can also be fitted satisfactorily from dislocation models. The conventional back-slip model, commonly used for subduction zones, may, however, lead to a biased inference about the geometry of the locked portion of the thrust fault. We therefore favour the use of a creeping buried dislocation that simulates the ductile shear zone in the lower crust. A limitation of dislocation models is that the mechanical response of the lithosphere to the growth of the topography by bending of the elastic cores and ductile flow in the lower crust cannot be easily introduced. Fortunately these effects can be neglected because we may assume, to first order, a stationary topography. Moreover, we show that not only can dislocation models be used to adjust surface displacements but, with some caution, they can also provide a physically sound rationale to interpret interseismic microseismicity in terms of stress variations.