In this research, the STRAIN HARDENING behavior of dual phase steel containing 0.11% C 1.30% Mn is studied, using the tensile tests. The empirical relationshipa=k(e°+e)n , which has been suggested by several investigators for STRAIN HARDENING behavior, is conformed. It is also shown that dual phase steels with up to 50% martensite have two stages of STRAIN HARDENING and by increasing martensite over than 50% there is only one stage of this process. Finally it was observed that increasing martensite volume fraction results in decreasing STRAIN HARDENING exponent (n) and increasing STRAIN HARDENING coefficient (k).

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.

In the current work, the STRAIN HARDENING behavior of dual-phase steels with different silicon content (0.34- 2.26 Wt. %) was examined using the modified Crussard-Jaoul analysis. It was shown that these dual-phase steels deform in two stages over a uniform STRAIN range. Each stage exhibited a different STRAIN HARDENING exponent varying with silicon content. At the first stage, work HARDENING exponent remind significantly constant, while during the second stage, it decreased with increasing silicon content from 0.34% to 1.51% and then increased for the higher silicon contents (1.51% to 2.26%). It was found that the STRAIN HARDENING behavior of these steels was predominantly affected by the volume fraction of marten site at low silicon contet and the ferrite strengthening induced by silicon at the higher silicon content. The effect of silicon content on the volume fraction of martensite and tensile properties were also considered.

This paper derives kinematic admissible bending moment – axial force (M-P) interaction relations for mild steel by considering STRAIN HARDENING idealisations. Two models for STRAIN HARDENING – Linear and parabolic have been considered, the parabolic model being closer to the experiments. The interaction relations can predict STRAINs, which is not possible in a rigid, perfectly plastic idealization. The relations are obtained for all possible cases pertaining to the locations of neutral axis. One commercial rolled steel T-section has been considered for studying the characteristics of interaction curves for different models. On the basis of these interaction curves, most significant cases for the position of neutral axis which are enough for the establishment of interaction relations have been suggested. The influence of STRAIN HARDENING in the interaction study has been highlighted. The STRAINs and hence the STRAIN rates due to bending and an axial force can be separated only for the linear-elastic case because the principle of superposition is not valid for the nonlinear case. The difference between the interaction curves for linear and parabolic HARDENING for the particular material is small.

This paper presents a macro model to predict unreinforced masonry structures in plane behavior. The model is based on the concept of multilaminate theory. In the past, the method has been used to model behavior of soil, disregarding the cohesion and the tensile strength. Regarding its mathematical base, and the possibility of applying in other cases, this method is used to predict the ultimate failur load in URM structures in present study. This model is intrinsically capable of spotting induced anisotropy of brittle material such as concrete, rocks and masonry, develponig as a result of cracking. Here, the yield surface applied, consists an generalized mohr-coulomb yield surface, along with a cap model and a cut-off tensile. Comparing numerical results predicted to be obtained in non-linear analysis of masonry structures unreinforced against lateral load, with the results of ther experimental data shows capability of the model in failure analysis of URM structures.

The effect of STRAIN HARDENING modulus on axisymmetric buckling of circular cylindrical shells made of aluminum and steel materials is investigated, so the nonlinear dynamic equations of cylindrical shells with different STRAIN HARDENING modulus for cylindrical shells made of aluminum material and different linear and multi-linear STRAIN HARDENING modulus for cylindrical shells made of steel material are solved for three types of boundary conditions and two types of loading. It is found that under investigated conditions, changing of STRAIN HARDENING modulus for cylindrical shells made of aluminum and steel materials transmit the buckling shape from plastic buckling to progressive buckling.

In this research, the mode II fracture toughness of O-notched diagonally loaded square plate samples with pre-existing cracks which are made of stainless steel 316L with specifications of highly ductile behavior and great STRAIN HARDENING is investigated theoretically and experimentally. For this purpose, several fracture tests are carried out on the pre-cracked specimens to determine the fracture toughness experimentally. The experimental observations and the load-displacement curves obtained from the fracture tests illustrate that the pre-cracked specimens undergo large plastic deformations at the onset of crack propagation. Afterward, the fictitious material concept is used to estimate the values of fracture toughness achieved experimentally. By using the fictitious material concept, the fracture toughness of pre-cracked specimens fabricated from stainless steel 316L could be estimated without the need for complicated and time-consuming elastic-plastic failure analysis and by performing only linear elastic analysis. For this purpose, the fictitious material concept is simply combined with mean stress, generalized mean stress, maximum tangential stress, generalized maximum tangential stress, STRAIN energy density, and generalized STRAIN energy density criteria. It is shown that the combination of fictitious material concepts with four linear elastic brittle fracture criteria is quite successful in predicting the mode II fracture toughness of ductile pre-cracked specimens.

In the present study, the effect of srain HARDENING exponent of material on flow characteristics, STRAIN and damage distribution in sample and the load requred for the execution of the deformation process was investigated using finite element simulation. Results showed that the corner gap is not formed during deformation of ideally plastic material and the amount of equivalent STRAIN is higher in the bottom side of sample compared with other regions. However, with increassing the work HARDENING exponent, the size of corner gap increases and the bottom side recieves less amount of STRAIN. Also, damage factor in the sample of idealy plastic material is higher at the top side compared with other regions and the tensile stresses are applied on this area. Whereas, in the STRAIN hardened material the higher damage factor was observed at the lower half of the sample. Finally, it was concluded that the pressing force increases with increassing the work HARDENING exponent.

In this study, the effect of pulse like and non-pulsed near field records on the displacement and axial force of the nail in the soil nail wall has been investigated. Pulse liked records are created under physical factors such as the effect of Forward directivity, Fling Step, the effect Hanging wall, etc., A pulse has a large amplitude with medium to long period, which contains most of the energy due to fault rupture. It has been used to investigate the effects of near-field records by the finite element method and by using the HSS behavioral model due to considering the effect of small STRAINs and hysteresis damping. In this research, Song and Rodrigues seismic bank in 2015 including 62 pulsed and non-pulsed near field records has been used. The obtained results showed that the soil nailed walls have good performance against seismic loads. pulsed records have a direct effect on the axial force and displacement of the nailed wall, also the axial force of the nails and displacements in the pulsed records have a good correlation with the PGV (peak ground velocity) parameter, the axial force of the nails in the non-pulsed records with the parameter It had Ia (Arias intensity) and non-pulse displacement with seismic parameter PGV.