BLACK-HOLE HAVING ELECTRIC HAIRS FOR POSITIVE COSMOLOGICAL CONSTANT Λ>0 ON A COSMIC HORIZON SCALE ~1/√Λ

This paper is a technical review for a more deliberate paper (Bhattacharya & Lahiri, 2007) where it has been shown that on a positive cosmological scale with Λ>0 having a cosmic horizon scale ~1/√Λ, there exists the soft electric hairs for the solution having the T_00 components of the stress-energy tensor T_μν i.e., ρ=0 on black hole horizon B_H having the maximum density at black hole singularity B_S where cosmic horizon C_H and black hole horizon B_H has only been considered. KEYWORDS: Black Hole – Cosmic Horizon – TOV Limit – Stress-Energy Tensor – Positive Cosmological Constant

Fracture Characteristics and Fatigue Damage of Noncoplanar Fractured Rocklike Specimens under Uniaxial Graded Cyclic Loading and Unloading

To study the fracture characteristics and fatigue damage of fractured rock masses, noncoplanar fractured rocklike specimens prepared using cement mortar were used for a graded cyclic loading–unloading test. The results showed that the two ends of the horizontal crack were the main stress concentration areas, and they inhibited crack initiation of the inclined fracture. With increasing crack inclination, the inhibitory effect became more obvious. Under the condition that the lower limit stress is constant, as the upper limit stress increases, energy dissipation of the specimen increases, becoming relatively stable in each stage of the cycle. With increasing crack inclination, the increase in the energy dissipation value decreases. Specimens with large changes in the shape of their hysteresis loop tend to exhibit large fluctuations in the elastic modulus. As the loading progressed, the elastic modulus exhibited a downward trend, and the damping ratio tended to be stable. The change in the damping ratio is affected by the dynamic elastic modulus and area of the hysteresis loop. Based on the Weibull probability distribution function, the evolution curve of the damage variable of the specimen can be obtained. This curve reflects the trend of the damage change of the rocklike specimens under various levels of cyclic loading and unloading.

Extension of a basic hypoplastic model for overconsolidated clays

This paper presents a new rate-dependent hypoplastic constitutive model for overconsolidated clays. The model is developed based on a basic hypoplastic model proposed recently for sand. New density and stiffness factors are introduced to account for history dependence. The Matsuoka-Nakai failure surface is incorporated for the limit stress criterion. With six constitutive parameters, the model is capable of predicting the hardening/softening, shear dilation/contraction, and asymptotic state for overconsolidated clays. Comparison between numerical predictions and experimental results shows this model can properly describe the main features of both reconstituted and undisturbed clays with different overconsolidation ratios.

Compliance with strength criteria for a model polymeric-composite grillage taking into account nonlinearity of the filler in different loading scenarios

This study compares different strength criteria in static loading simulation of a polymeric-composite grillage for different loading scenarios, boundary conditions and models of physical material behaviour. The paper discusses a detailed, structurally similar model of grillage made up by three-layered parts taking into account contact interaction (not the joint one) at the boundaries of bearing layers and the filler, with consideration of physically linear and nonlinear model of filler behaviour. The study applies volume-shell FE idealization. The loading (distributed and local)is simulated as per a step-wise procedure until the selected failure criteria are met, i.e. until limit loads (according to various hypotheses) are achieved. The paper gives examples of limit load calculations and their respective states of grillage for different variants of bearing circuit fastening and different loading types. The study yielded the fields of stress-strain parameters and the four principal complex failure criteria. The study discusses the effect of overall grillage compliance, as well as the effect of local (i.e. not affecting the compliant areas of the flooring) and distributed loading upon the limit state pattern of the structure and the level of its bearing capacity. It also estimates the effect of soft non-linearity of the filler upon limit stress-strain state pattern and limit load level, as well as upon the localization of «triggering» zones for non-dimensional criteria.

Change of Specimen Temperature during the Monotonic Tensile Test and Correlation between the Yield Strength and Thermoelasto-Plastic Limit Stress on the Example of Aluminum Alloys

This paper presents an attempt to generalize the description of the course of specimen temperature changes during the tensile test and to connect the value of the thermoelasto-plastic limit stress with the value of a clear (physical) or proof strength (offset yield strength) on the example of tests of the following aluminum alloy sheets used in Poland for airplane structures: 2024-T3 and D16 in three grades: D16ATV, D16CzATV, and D16UTV. A thermographic camera was used for specimen surface temperature measurement during the tensile test. The Portevine–Le Chatelier effect (the so-called PLC effect) was observed for tests of specimens cut from sheet plates, which was strongly reflected in the temperature fluctuations. The course of temperature change during tensile tests was divided into four characteristic stages related to the occurrence of a clear or offset yield strength. It was found that if there is a clear yield strength, the value of the thermoelasto-plastic limit stress was greater than this yield strength. If there was an offset yield strength, the value of the thermoelasto-plastic limit stress was lower than this yield strength. The differences in the aforementioned values of individual yield strengths did not exceed several percent. Thus, it can be concluded that the thermoelasto-plastic limit stress determined on the basis of the course of specimen temperature changes during the tensile test is well correlated with the value of the yield strength of the material.