Investigation of Load Capacity of Steel Concrete Composite Columns Src Reinforced by IPE

In this study, a column with section IPE and different lengths, completely embedded in concrete, is modelled by finite element software ABAQUS. Columns under different bi-axial loading were used and graphs of axial force-axial deformation, interaction axial force, and bending moment and column curve were mapped. The results show that the load capacity of the column, with increasing length and also increasing eccentricity of the axial load, will be reduced. With increasing length, the effect of an increased eccentricity of the reduced load capacity was increased. Equations for the design of the column are also presented. The results of the presented equations were compared with the values obtained from finite element and building national institute 10th topic.

Residual stress and fatigue behavior of riveted lap joints with various riveting sequences, rivet patterns, and pitches

The residual stress of multi-rivet structures is related with the riveting sequence, the rivet pattern, and the pitch due to the deformation interaction of different rivets. The stress amplitude of riveted structures subjected to the cyclic loads is affected by the residual stress, which increases the difficulty in the prediction of fatigue life. In this article, the riveting processes for single-row and triple-row riveted lap joints with various riveting sequences, rivet patterns, and pitches are studied numerically and experimentally. The residual stresses for both types of riveted structures are verified by the testing data. Significant difference appears in the residual stress field for riveted lap joints with various riveting sequences and rivet patterns. The decrease in the rivet pitch increases the compressive residual stress at the edge of the rivet hole. Furthermore, the fatigue life prediction model is developed for multi-rivet structures, in which the coupling effect of residual stress and cyclic load is considered. The fatigue experiments are conducted for riveted lap joints with various riveting sequences, rivet patterns, and pitches. The accuracies of the numerical results obtained from the Homan model and the developed model are compared with the experimental data. The proposed fatigue model shows better performance to predict fatigue life for multiple rivet structures.

Молекулярно-динамическое моделирование влияния кремния на упорядочение углерода в решетке мартенсита

The results of computer simulation of the influence of silicon impurities on the degree of tetragonality and on the interaction of carbon atoms in the body-centered cubic (BCC) lattice of iron by the molecular-dynamics method are reported. The influence of silicon on the martensite-lattice parameters has been established, as well as the dependence of the deformation interaction parameter λ_0 determining the critical temperature of the BCC–BCT (body-centered tetragonal) transition on the silicon concentration, is calculated on the basis of the Zener–Khachaturyan theory of ordering. It is found that the λ_0 parameter decreases by 18% from 5.2 to 4.2 eV/atom upon an increase in the silicon content up to 10 at %.

Study of the Deformation/Interaction Model: How Interactions Increase the Reaction Barrier

The interactions (including weak interactions) between dienophiles and dienes play an important role in the Diels-Alder reaction. To elucidate the influence of these interactions on the reactivity, a popular DFT functional and a variational DFT functional corrected with dispersion terms are used to investigate different substituent groups incorporated on the dienophiles and dienes. The bond order is used to track the trajectory of the cycloaddition reaction. The deformation/interaction model is used to obtain the interaction energy from the reactant complex to the inflection point until reaching the saddle point. The interaction energy initially increases with a decrease in the interatomic distance, reaching a maximum value, but then decreases when the dienophiles and dienes come closer. Reduced density gradient and chemical energy component analysis are used to analyse the interaction. Traditional transition state theory and variational transition state theory are used to obtain the reaction rates. The influence of tunneling on the reaction rate is also discussed.

A Model for the Conductivity and Compliance of Unpropped and Natural Fractures

Summary Fluid flow in unpropped and natural fractures is critical in many geophysical processes and engineering applications. The flow conductivity in these fractures depends on their closure under stress, which is a complicated mechanical process that is challenging to model. The challenges come from the deformation interaction and the close coupling among the fracture geometry, pressure, and deformation, making the closure computationally expensive to describe. Hence, most of the previous models either use a small grid system or disregard deformation interaction or plastic deformation. In this study, a numerical model is developed to simulate the stress-driven closure and the conductivity for fractures with rough surfaces. The model integrates elastoplastic deformation and deformation interaction, and can handle contact between heterogeneous surfaces. Computation is optimized and accelerated by use of an algorithm that combines the conjugate-gradient (CG) method and the fast-Fourier-transform (FFT) technique. Computation time is significantly reduced compared with traditional methods. For example, a speedup of five orders of magnitude is obtained for a grid size of 512 × 512. The model is validated against analytical problems and experiments, for both elastic-only and elastoplastic scenarios. It is shown that interaction between asperities and plastic deformation cannot be ignored when modeling fracture closure. By applying our model, roughness and yield stress are found to have a larger effect on fracture closure and compliance than Young's modulus. Plastic deformation is a dominant contributor to closure and can make up more than 70% of the total closure in some shales. The plastic deformation also significantly alters the relationship between fracture stiffness and conductivity. Surfaces with reduced correlation length produce greater conductivity because of their larger apertures, despite more fracture closure. They have a similar fraction of area in contact as compared with surfaces with longer fracture length, but the pattern of area in contact is more scattered. Contact between heterogeneous surfaces with more soft minerals leads to increased plastic deformation and fracture closure, and results in lower fracture conductivity. Fracture compliance appears not to be as sensitive to the distribution pattern of hard and soft minerals. Our model compares well with experimental data for fracture closure, and can be applied to unpropped or natural fractures. These results are obtained for a wide range of conditions: surface profile following Gaussian distribution with correlation length of 50 µm and roughness of 4 to 50 µm, yield stress of 100 to 1500 MPa, and Young's modulus of 20 to 60 GPa. The results may be different for situations outside this range of parameters.

Effect of Gaseous Hydrogen Charging on Nanohardness of Austenitic Stainless Steels

Understanding of hydrogen effect on local mechanical properties of metals is important for understanding hydrogen embrittlement mechanisms. The effect of thermal gaseous hydrogen precharging on the nanomechanics of SUS310S and SUS304 austenitic stainless steels has been investigated using a combination of nanoindentation and atomic force microscopy (AFM). It is observed that hydrogen precharging decreases the first excursion load in load versus displacement curves and enhances the slip steps around indentations for both the materials, which experimentally support the hydrogen-enhanced localized plasticity (HELP) mechanism. The nanohardness in SUS310S stable austenitic stainless steel is increased by hydrogen precharging while that in SUS304 metastable austenitic stainless steel is decreased by hydrogen precharging. The hydrogen-induced hardening in SUS310S and softening in SUS304 are discussed in terms of the hydrogen/deformation interaction and the effect of hydrogen on strain-induced martensite transformation.