In this research, the behavior of plastic concrete materials with a strain Hardening/Softening Elasto-Plastic constitutive model are investigated using FLAC software based on a series of drained triaxial test results. The constitutive model is based on the mobilized strength (friction and cohesion) and mobilized dilatation angle concepts. The results indicate that the assumed functions of modified mobilized friction angle and mobilized cohesion (The Yield function of the model) which are common for geotechnical materials, can predict stress-strain behavior with a sufficient accuracy. However, they cannot simulates the Volume changes due to dilation effects accurately, especially for plastic concrete with a relatively high stiffness and strength. Therefore, the potential function of the model is modified. The stress-strain and Volume strains that have been obtained from the modified model are in good agreement with the experimental data, especially for soft plastic concrete, as well as for hard plastic concrete in a low confining pressure.

Plastic hinge properties play a crucial role in predicting the nonlinear response of structural elements. The plastic hinge region of reinforced concrete normal beams has been previously studied experimentally and analytically. The main objective of this research is to evaluate the behavior of the plastic hinge region of reinforced concrete deep beams and its comparison with normal beams through finite element simulation. To do so, ten beams contain six deep beams, and four normal beams, under concentrated and uniformly distributed loading, are investigated. Lengths in the plastic hinge region involving curvature localization, rebar yielding, and concrete crushing zones are studied. The results indicate that the curvature localization zone is not suitable for the prediction of plastic hinge length in reinforced concrete deep beams. Based on the results it can be stated that in simply supported normal beams the concrete crushing zone is focused on the middle span, but in simply supported deep beams by creating a compression strut between loading place and support, the concrete crushing zone spreads along the compression trajectory. The rebar yielding zone of simply supported beams increases as the loading type is changed from the concentrated load at the middle to the uniformly distributed load.

In this paper, an elasto-plastic analytical-numerical method for the analysis of underwater tunnels is proposed. Seepage flow and secondary permeability of the rock mass due to the mechanical-hydraulic coupling are taken into accounts for plastic zone. Meanwhile, a modified accurate seepage model is used for elastic zone. As the analytical equations do not have closed form solutions, a computer program has been presented to obtain the solutions.

In this study, the effect of geometrical parameters of rectangular vortex extrusion die, including twist angle (𝜑 ), reduction in area (𝑅 𝐴 ), and twist zone length (𝐿 ), on deformation inhomogeneity is investigated using the finite element analysis and response surface methodology. Analysis of variance (ANOVA) was used to determine the primary parameters and accuracy of the mathematical model obtained from response surface methodology results. The results showed that the suggested mathematical model predicts the strain inhomogeneity with high accuracy. Additionally, it revealed that the input parameters of 𝜑 , 𝑅 𝐴 , 𝐿 , the interaction between 𝜑 and 𝑅 𝐴 (𝜑 × 𝑅 𝐴 ), and interaction between 𝑅 𝐴 and 𝐿 (𝑅 𝐴 × 𝐿 ) are the main significant factors affecting the inhomogeneity. Perturbation plots and 3D surface diagrams were used to check the results of ANOVA, the sign, and the magnitude of the coefficient of the suggested mathematical model.

High pressure torsion is an effective Severe Plastic Deformation method for producing nanostructured bulk materials. In this research, deformation behavior of Aluminum 5452 alloy disks obtained from unconstrained high pressure torsion has been studied. There is a region between adhesive zone and sliding zone defined as critical radius (r*) on vicinity of which, microhardness and effective applied strains (PEEQ) are more than those of other regions. Since Number of Turns and Applied Pressure are the most important parameters of HPT process, for studying their effects on r* of disks, in this research the process was simulated by applying conditions of previous experimental research. For this end, ABAQUS software was used and r* values were calculated and recorded. It was observed that by increasing N and applied P, r* values increase. For better studying the properties of disks obtained from unconstrained HPT process, the process was simulated under applied pressure of 2. 7 GPa and 1, 2, 3 … and 10 turns. Eventually by using PEEQ distribution obtained from software, deformation behavior of disks in higher turns was analyzed, and specially the r* of unconstrained HPT that obtained from experimental tests and simulation, was examined.

In most mechanical parts, geometrical discontinuities or notches exist. Usually the material response in these discontinuities is elastoplastic. Because of complexity and time consuming of plastic analysis, researchers have proposed estimation methods based on the linear elastic behavior. In this paper, a new estimation method, based on Dafalias-Popov’s two surface plasticity model, is proposed which is coupled with incremental Neuber’s rule and incremental equivalent strain energy density methods. Although the method has simple equations, but Dafalias-Popov’s plasticity model has complexities and challenges, like bounding line effect on the model prediction and shape parameter determination. To verify the model and evaluating the challenges, a plate with elliptical and traction free hole under remote monotonic uniaxial load is considered. Plane stress condition is assumed and elastoplastic behavior is of Ramberg-Osgood type. Results show that the bounding line effect can be neglected, in most engineering problem which strain range is less that 20 percent. It is shown that the shape parameter has optimum value in certain range. Results show that accuracy of the model in stress-strain prediction is in acceptable range

Background and Aim: In patients with complete denture, some clinicians have used modelling plastic impression compound (MPIC) along tissue conditioner (TC) materials simultaneously. Little information is available on the composition of these materials and the interaction between them. The purpose of this study was to evaluate the influence of two components of MPIC on the structure and chemical composition of TC.Materials and Methods: In this experimental study, MPIC specimens were provided in 25×2 mm discs. Specimens were randomly divided into three groups and were immersed in ethanol 70%, plasticizer (dibutyl phthalate) and a mixture of them (ethanol 70% and dibutyl phthalate). All of the discs were weighed with a digital balance before and 2, 4, 6 and 24 hours after immersion. Values were analyzed by non parametric Kruskal-Wallis (a= 0.05) and SPSS 16 for Windows (SPSS Inc., Chicago, IL) was used for statistical analysis.Results: Statistical analysis indicated significant differences among all groups (p>.05).Conclusion: Dibutyl phthalate (DBP) had high impact on the solubility of MP, while the mixture of dibutyl phthalate (DBP) and ethanol demonstrated the highest impact.