Complete Stress-strain Relation Research Articles

Analysis of deformation localization and the complete stress–strain relation for brittle rock subjected to dynamic compressive loads

Analysis of deformation localization and the complete stress–strain relation for brittle rock subjected to dynamic compressive loads

Analysis of the localization of deformation and the complete stress–strain relation for mesoscopic heterogeneous brittle rock under dynamic uniaxial tensile loading

Stress redistribution induced by excavation results in the tensile zone in parts of the surrounding rock mass. It is significant to analyze the localization of deformation and damage, and to study the complete stress–strain relation for mesoscopic heterogeneous rock under dynamic uniaxial tensile loading. On the basis of micromechanics, the complete stress–strain relation including linear elasticity, nonlinear hardening, rapid stress drop and strain softening is obtained. The behaviors of rapid stress drop and strain softening are due to localization of deformation and damage. The constitutive model, which analyze localization of deformation and damage, is distinct from the conventional model. Theoretical predictions have shown to consistent with the experimental results.

Uniaxial Compressional Stress‐Strain Relation of Concrete

A new formula that represents both ascending and descending portions of uniaxial compressional stress-strain relation is suggested. This formula consists of two parameters, one governing the steepness of ascending portion and the other controlling the steepness of descending portion. For all possible variations of the parameters, the suggested formula implicitly satisfies the basic properties of a complete stress-strain relation that the stress ascends, reaches its peak value, and then descends, as the strain increases. Expressing the parameters in term of concrete strength, the suggested formula automatically satisfies the behavior of concrete under uniaxial compression that the descending portion becomes steeper as concrete strength is higher. Using the suggested formula, the entire range of strength-stress relation can be favorably determined upon comparing to available test data.

Crack softening zone in plain concrete under static loading

Starting from the fictitious crack model the softening zone at the tip of a discrete crack in concrete is studied. Using a power relation for the stress distribution in the softening zone, the extension of this zone is a function of the exponent. If the fully softened cross-section is taken as a failure criterion, the exponent can be considered as a measure for the true strength of the material. Supporting the theory concrete plates were tested under uniaxial tensile loading. Since stress distribution cannot be measured the strain distribution around the crack was determined. Using the complete stress-strain relation the strains were translated into stresses. The test results are discussed and compared to the theoretical model. Further studies are encouraged to improve the accuracy of the experiments and to extend the model to cyclic loading.

低側圧３軸圧縮下のコンクリートの塑性変形挙動

The ductility improvement of confined concrete and steel fiber reinforced concrete is mainly due to the lateral confining effect of lateral bars and steel fiber, respectively, caused by the Poisson's effect of concrete after failure; and this effect can be related to the behavior of plain concrete under multiaxial stress states. Thus, it is quite important to obtain the complete stress-strain relation from the reliable experimental data on the post-failure behavior of concrete under low hydro-pressure, when the ductility improvement of such composite concretes is analytically discussed.In the present study, the effects of various parameters on the plastic deformation behavior of axially loaded plain concrete subjected to low lateral confining stress were examined. The parameters used included the shape of specimen, water-cement ratio, magnitude and loading path of lateral stress, and ratio of two lateral stresses. Furthermore, the effects of the end confinement by steel ring, end friction, and steel fiber reinforcement on the plastic deformation behavior of concrete were discussed.

A finite element method for stress analysis or elastoplastic body with polygonal line strain-hardening

In this paper, the stress-strain curve of material is fitted by polygonal line composed of three lines. According to the theory of proportional loading in elastoplasticity, we simplify the complete stress-strain relations, which are given by the increment theory of elastoplasticity. Thus, the finite element equation with the solution of displacement is derived. The assemblage elastoplastic stiffness matrix can be obtained by adding something to the elastic matrix, hence it will shorten the computing time. The determination of every loading increment follows the von Mises yield criteria. The iterative method is used in computation. It omits the redecomposition of the assemblage stiffness matrix and it will step further to shorten the computing time. Illustrations are given to the high-order element application departure from proportional loading, the computation of unloading fitting to the curve and the problem of load estimation.

Researches into the complete stress-strain curve for concrete

Summary This paper describes two series of tests on concrete specimens for the purpose of determining the complete stress-strain relation in uniaxial compression, including the falling branch. In the second series, lateral as well as longitudinal strains were measured which showed that initial tension cracking occurs locally within the gauge length and that portions of this length may be uncracked at maximum load on the specimen. The results included in the paper demonstrate the ability of concrete to undergo very large changes in length without ceasing to carry load.

Mechanical Behavior of Viscoelastic Fibers

The under-determined equation M(F,D,dF/dt,dD/dt)=0, where F=F(t), D=D(t) are measures of force and deformation and t is time, can be transformed into a first-order partial differential equation in F, D, ∂F/∂D, ∂F/∂t whose characteristics represent the totality of all possible force-elongation trajectories in F, D, t space. Historically, M has seen considerable service either as a complete stress-strain relation or an element in a distribution of such relations. A geometric interpretation of M useful in rheological studies of fibers is given. Necessary conditions are given for M to provide a satisfactory description of a fiber's mechanical behavior. An operational procedure is outlined for constructing M in the laboratory based on direct measurements instead of on a priori assumptions involving springs and dash pots. The discussion is brief and theoretical.

The Stress-Strain Relation in Celanese Single Fibres

In order to prove that the technique is capable of giving reproducible results the complete stress-strain relations for two nearly identical Celanese fibres have been obtained. The fibres differed somewhat in cross-section area. This introduces a difference in rate of stressing. A correction for this has been developed and applied. In the plastic region where pronounced shear slip is expected the stress-strain curve is found to be made up of a series of straight line segments, along any given, one of which the strain. hardening is proportional to the elongation. A change in rate of strain introduces errors which the simple Maxwell relaxation law cannot account for.