Showing papers on "Stress–strain curve published in 1976"

Analysis of stress and strain distribution in thin films and substrates

Abstract: Calculations are presented for the distribution of stress and strain in thin films and substrates from inhomogeneous plane stresses developed in the film during deposition. The results can be applied to the ’’bending‐plate method’’ of determining the unknown stresses in a film, in which the deformation of the substrate surface is measured. Thereby the local values of the stress tensor within the film plane (averaged through the film thickness) and the center of the stress distribution normal to the film plane can be obtained in principle. A more convenient evaluation based on linear approximations is applicable when the film thickness is small. Restrictions are discussed which result from neglecting the conditions of compatibility for the components of the strain tensor.

Seismic Cracking of Concrete Gravity Dams

Abstract: A mathematical model describes properties of concrete under a two-dimensional state of stress. The effects of strain rate — the time rate of change of strain — on the mechanical properties are incorporated in the model. Appropriate assumptions are introduced in the model where experimental data were lacking; it was assumed, for example, that strain rate effects on mechanical properties of concrete under biaxial states of stress are identical to those revealed by uniaxial tests, because experimental data were available only for the latter case. Because no data were available for complete stress and strain reversals, the stress-strain curves in unloading and reloading where hypothesized in terms of the skeleton stress-strain curve. A method is developed for nonlinear analysis of response of concrete gravity dams to earthquake ground motion wherein mechanical properties of concrete are defined by the mathematical model mentioned. Each dam monolith is treated independently and idealized as an assemblage of two-dimensional finite elements.

10 Degree Off-Axis Tensile Test for Intralaminar Shear Characterization of Fiber Composites.

Abstract: : A combined theoretical and experimental investigation was conducted to assess the suitability of the 10 deg off-axis tensile test specimen for the intralaminar shear characterization of uni- directional composites. Composite mechanics, a combined-stress failure criterion, and a finite element analysis were used to determine theoretically the stress-strain variation across the specimen width and the relative stress and strain magnitudes at the 10 deg plane. Strain gages were used to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/ epoxy were used in the experimental program. It was found that the 10 deg off-axis tensile test specimen is suitable for intralaminar shear characterization and it is recommended that it should be considered as a possible standard test specimen for such a characterization. (MM)

Stress-strain curves for niobium crystals deformed at temperatures below ambient

Abstract: Niobium crystals, with a wide range of orientations, have been deformed at temperatures where slip takes place on the anomalous (011) plane. A strong orientation dependence of the axial yield stress was observed in both tension and compression; at 77 K the stress-strain curves were serrated. Both the yield stresses and the stress-strain curves were affected by the surface condition of the test specimens.

Tensile deformation of amorphous nickel-palladium-phosphorous alloys

Abstract: Ni-Pd-P amorphous alloys show inhomogeneous plastic deformation, as do all other amorphous alloys. A few localized deformation bands appear macroscopically just beyond the elastic region of the stress strain curve. It is shown that two types of localized deformation bands can be produced during tensile deformation,i.e., one has sharp steps produced by plastic flow associated with a shear, and the other has interconnecting voids similar to a crazing crack in polymers.

An elastostatic model of stress accumulation on the San Andreas fault

Abstract: Earthquakes on the San Andreas fault in California are due to lateral motion between the Pacific and Americas plates. Some sections of the fault are locked (to a fraction of their depth) between major earthquakes while others are free-sliding. We model this problem by considering two semi-infinite plates sliding past each other. Near the fault an inner solution in the vertical cross-plane is obtained. If the length of the locked sections is large compared with the thickness of the plates an outer solution exists in which the stress and strain components are constant across the plates. Such solutions are obtained for (i) a single locked section, (ii) two locked sections separated by a central crack. The inner and outer solutions are asymptotically matched, and the results used to predict the distribution of stress and strain near the fault. The creep velocities on the freesliding sections are shown to be a fraction of the relative plate velocity. When a great earthquake occurs on one locked section it appears that a significant fraction of the relieved stress is transferred to each adjacent locked section. An expression is obtained for the strain energy so released.

The stress‐strain behavior of materials exhibiting andrade creep

Abstract: The stress-strain behavior of a material exhibiting Andrade creep (for which the creep compliance is linear in the cube-root of time) has been calculated for loading at constant strain rate and at constant stress rate for the limiting case of linear viscoelastic behavior and at constant for one type of nonlinear viscoelastic response. The recoverable strain after the stress has been removed has also been calculated for these three cases. The results of the calculations are compared with experiment.

Rate-dependent stress–strain behavior of polymeric materials

Abstract: The investigation characterizes the rate-dependent uniaxial stress–strain behavior of several polymeric materials. The characterization is done using both a mechanical model with rate-dependent elements and a general nonlinear theory of viscoelasticity. Experimental data were gathered on a Laminac polyester resin, and further data on polycarbonate and PMMA were collected from the work of Brinson. The mechanical model could be called a modified Bingham type, while the nonlinear viscoelastic theory was the single integral constitutive model proposed by Bernstein, Kearsley, and Zapas. Results from the mechanical model gave good agreement with the experimental data, the maximum difference being about 10%. The BKZ theory predictions modeled the data to within 5–12% average error.

Finite-element analysis of creep and plasticity tensile-test specimens: Hourglass and cylindrical test-specimen geometries are compared for uniformity of strain state and accuracy of extensometry for use in high-temperature mechanical-properties studies

Abstract: Traditionally, mechanical properties as determined from sensile-test specimens are assumed to be truly uniaxial and are used directly in finite-element codes for design purposes. In this paper, the stress and strain distributions in two test geometries, an hourglass specimen and a cylindrical specimen, are critically examined by means of the nonlinear finite-element code CREEP-PLAST.

Applicability of Linear Elastic Fracture Mechanics to 5.6-mil Boron/6061 Aluminum

Abstract: A coordinated experimental and analytical program was directed toward assessing the applicability of linear elastic fracture mechanics to 5.6-mil boron/6061 aluminum subjected to Mode I loading. Fifty-nine standard ASTM three-point bend and center-notched specimens were tested. The effects of laminate orientation, specimen thickness, crack length, specimen configuration, and heat treat condition on laminate fracture toughness are reported. A technique of predicting the fracture toughness of an arbitrary (0/±a/90) laminate from critical strain energy release rate data for 0-, =fc«-, and 90° specimens was evaluated for (0/±45) boron/aluminum.

On the Theory of the Stress-Strain State in Adhesive Joints

Abstract: The stress-strain state in adhesive joints is analyzed for normal stressing and an exact solution is obtained for the elastic-theory problem in these three-layer systems The differential equations of equilibrium and boundary conditions are satisfied exactly or (on the surface where the stresses are given) integrally The solution indicates that in addition to the tensile stresses codirectional with the external force field, stresses perpendicular to the latter (ie codirectional with the joint itself) are also produced: compressive in the adherend, tensile in the adhesive In addition, tangential stresses are produced in the end zone of each layer, rendering this zone the most dangerous The classical strength theory shows that the worst danger spot is the bulk of the adhesive rather than the interface Failure criteria are obtained for the system in question, as well as conditions of strength equivalence of its components The latter is effected by reducing the thickness of the adhesive layer

Stress-Strain Relations of Polycrystalline Metals : 3. Proportional Loadings of F.C.C. Metals

Abstract: The theoretical prediction of plastic stress-strain relations of face-centered-cubic polycrystals subjected to proportional loadings is discussed on the basis of K. B.W model. This theory is applied to predict the stress-strain curve of thin-walled aluminium cylinders subjected to internal pressure loading by using the experimental curve of simple tension. A good agreement between the theoretical and experimental results is obtained. Furthermore it is found that Taylor's prediction based on the ratio of the yielding stress of a polycrystal to that of a single crystal gives almost the same results as the K. B. W. model prediction.

Stress-strain behavior of sand

Abstract: The paper presents results of laboratory static and cyclic loading tests on Ottawa Sand. A variety of stress paths was used. The results are analyzed by elastic-plastic-work hardening theory. It is shown that the Mohr-Coulomb failure criterion, combined with an expanding elliptical cap can satisfactorily represent material behavior. The proposed model makes it possible to predict soil response to diverse stress paths from the results of hydrostatic compression and drained triaxial compression tests. The model is applicable to material behavior under both static and cyclic loading.

Stress-strain behavior of polymer-impregnated concrete

Abstract: The paper shows that stress-strain behavior of concrete can be varied over a wide range, from ductile to brittle, by using combinations of plasticizing (n-butyl acrylate) or cross building (TMPTMA) monomers with methyl methacrylate, or both It is also shown that a realistic level of salt (up to 1 percent) in concrete prior to impregnation has little effect on polymer loading mechanical properties, but it requires more rigorous drying While high temperatures accelerate drying out but decrease strength, subsequent polymer impregnation essentially yields a material with properties similar to a conventionally dried material

Rational soil model in calculations of fills in a two-and three-dimensional formulation

Abstract: 1. The use of methods for calculating earth structures or methods for using their state of stress and strain under conditions of the two-and three-dimensional problems based on assigning the average data on deformation properties of the material leads to errors exceeding the requirements imposed on the accuracy of engineering calculations. 2. In calculations based on the use of the nonlinear relationships between stresses and strains it is of considerable practical importance to reflect the properties of contraction and dilatancy of the soils and the relation of the mechanical properties to the form of the three-dimensional stress condition. Consequently, the soil model should include data on the mutual effect of the average stress, stress intensity, and form of the three-dimensional stress condition in all possible variants of its further development (for example, reaction of the effect of the stress trajectory and other factors). 3. In solving problems of the stability of earth structures and forecasting the formation of cracks it is necessary to consider jointly the state of stress and strain of the structure and equation of limit equilibrium; data on the strength of materials alone is insufficient in solving these problems. The relation of the strength of soils to the form of the three-dimensional stress condition is of great importance in this case. 4. Considering the great practical importance of refining the data on the mechanical properties of material in a three-dimensional stress condition in calculation of earth structures, it is important to undertake a further mathematical analysis for the purpose of determining the role of such factors as the effect of the stress trajectory and rotation of the axes of the principal stresses on the mechanical properties of soils. 5. The necessary volume of data on the mechanical properties of soils for calculating the structures can be obtained on triaxial compression devices with independently controlled principal stresses, for example, the apparatus designed by the V. V. Kuibyshev Moscow Institute of Civil Engineering. It is necessary to introduce such devices into research practice for the purpose of designing hydraulic engineering earth structures.