Evaluation of the Accuracy of Out-of-Plane Normal Stress Detection Using Novel Piezoresistive CMOS Sensors

This paper discusses the measurement opportunities arising from a novel piezoresistance sensor featuring vertical currents. Temperature-compensated measurements of a sum of the three normal stress components including the vertical normal stress, are presented. In specific applications with sensors located at free surfaces where the vertical normal stress component vanishes, a combination of this temperature-compensated measurement and a pseudo-Hall measurement yields the individual in-plane normal stresses. Furthermore, the temperature-uncompensated extraction of the vertical normal stress component is discussed with respect to the new measurement possibilities provided by the presented sensor. A sensitivity analysis illustrates the influence of individual uncertainty sources to the overall uncertainty of the measurement. Based on these results possible improvements in stress detection are suggested.

Thermomechanical Intereactions in Porous Generalized Thermoelastic Material Permeated with Heat Sources

The Laplace and Fourier transforms have been employed to find the general solution to the fields equations in porous generalized thermoelastic medium subjected to thermomechanical boundary conditions permeated with various heat sources; in the transformed form. On the boundary surface, the distributed sources have been taken. To get the solution in the physical form, a numerical inversion technique has been used. The effect of continuous and moving heat sources with the thermomechanical boundary conditions; and the response of boundary sources (concentrated and continuous) with heat source varying with depth; on the normal stress component, change in volume fraction field and temperature distribution have been depicted graphically for a particular model. A particular case is also deduced from the present formulation.

Non-Linear Two-Equation Model Taking Into Account the Wall-Limiting Behaviour and Redistribution of Stress Components

Nonlinear k–ε models have been extensively used in technological applications. It is clear from the assessment of the existing nonlinear k–ε models using DNS databases that the nonlinear models can not satisfy and reproduce exactly the wall-limiting behaviour and the anisotropy of Reynolds normal stress components. Especially, the Reynolds normal stress component, u22, in the wall-normal direction, which is proportional to x24 near the wall is not satisfied. Since the wall limiting behaviour of Reynolds normal stress components in the nonlinear model is determined by the turbulence energy k, which is proportional to x22 in the model, the Reynolds stress components, u12, u22 and u32 are proportional to x22. In this study, we have proposed a new nonlinear k–ε model which satisfies exactly the wall limiting behaviour of Reynolds normal stress components in the inertial and the noninertial frames. The proposed model can also predict well the anisotropy of the Reynolds normal stress components near the wall.

Contact Stress Analysis of Normally Loaded Rough Spheres

The Hertz analysis of contact stresses is extended to include the effects of friction on the interface between two elastic spheres compressed along the line connecting their centers. The problem is shown to be one of a class which requires incremental formulation. Stress functions of interest in connection with the analysis of the shear-loaded half-space in the linear theory of elasticity are developed. The distribution of shear stress needed to prevent relative slip of surficial points after they enter the contact region is found to be finite everywhere in the region. The ratio of this shear stress to the coexisting normal stress component is shown to exhibit a singularity at the edge of the contact region. This implies that when elastically dissimilar spheres are pressed together microscopic slip must occur in a narrow annulus at the boundary of the contact region.

Representation of Three-Dimensional Stress Distributions by Mohr Circles

O. Mohr has developed a diagram representing the normal stress component snn = σn and the total shearing stress component τn on an element of surface of any prescribed orientation with respect to the directions of the principal stresses. His procedure, however, does not give the orientation of the shearing stress τn within the element or, which is equivalent, the components of this shearing stress in a plane co-ordinate system within the element under consideration. An extension of the Mohr method that overcomes this limitation is presented in this note.