Influence on mechanical behaviors considering construction hosting process of large-scale steel structure

In the design of large-scale steel structure, the design calculation of the structure is usually based on the service state. But in the process of steel structure construction, the displacement and stress produced in the construction process cannot be completely consistent with that in the design state. With the progress of construction process, the deformation and stress caused by self-weight and construction load gradually accumulate until the structure is formed, which will produce construction error relative to the design state. In this paper, FEM method was used to simulate the construction process of the steel grid roof of the theater in the Beijing Sub Center Theater project, and the influence of the accumulated deformation and stress on the mechanical properties of the structure during the construction process was analyzed. The results show that the cumulative deformation and stress in the construction process have a great influence on the final deformation and stress distribution of the structure. The maximum vertical displacement in the actual construction state is 599.6% of that in the design state, and the maximum stress is 119.7% of that in the design state. This will lead to the difference between the construction-completed structure and the design structure, which makes the design result dangerous. The measures to optimize the construction process were also given in this paper, which provides guidance for the construction process of large-scale steel structure.

Analysis of Strain Partitioning in Intercritically Deformed Microstructures via Interrupted Tensile Tests

Intercritically deformed steels present combinations of different types of ferrite, such as deformed ferrite (DF) and non-deformed ferrite (NDF) grains, which are transformed during the final deformation passes and final cooling step. Recently, a grain identification and correlation technique based on EBSD has been employed together with a discretization methodology, enabling a distinction to be drawn between different ferrite populations (NDF and DF grains). This paper presents a combination of interrupted tensile tests with crystallographic characterization performed by means of Electron Backscatter Diffraction (EBSD), by analyzing the evolution of an intercritically deformed micro-alloyed steel. In addition to this, and using the nanoindentation technique, both ferrite families were characterized micromechanically and the nanohardness was quantified for each population. NDF grains are softer than DF ones, which is related to the presence of a lower fraction of low-angle grain boundaries. The interrupted tensile tests show the different behavior of low- and high-angle grain boundary evolution as well as the strain partitioning in each ferrite family. NDF population accommodates most of the deformation at initial strain intervals, since strain reaches 10%. For higher strains, NDF and DF grains behave similarly to the strain applied.

Distinguishing contributions of ceramic matrix and binder metal to the plasticity of nanocrystalline cermets

Using the typical WC–Co cemented carbide as an example, the interactions of dislocations within the ceramic matrix and the binder metal, as well as the possible cooperation and competition between the matrix and binder during deformation of the nanocrystalline cermets, were studied by molecular dynamics simulations. It was found that at the same level of strain, the dislocations in Co have more complex configurations in the cermet with higher Co content. With loading, the ratio between mobile and sessile dislocations in Co becomes stable earlier in the high-Co cermet. The strain threshold for the nucleation of dislocations in WC increases with Co content. At the later stage of deformation, the growth rate of WC dislocation density increases more rapidly in the cermet with lower Co content, which exhibits an opposite tendency compared with Co dislocation density. The relative contribution of Co and WC to the plasticity of the cermet varies in the deformation process. With a low Co content, the density of WC dislocations becomes higher than that of Co dislocations at larger strains, indicating that WC may contribute more than Co to the plasticity of the nanocrystalline cermet at the final deformation stage. The findings in the present work will be applicable to a large variety of ceramic–metal composite materials.

STUDY OF MECHANICAL PROPERTIES AND STRUCTURE OF LARGE-SIZED SEMI-FINISHED PRODUCTS MADE OF VT6ch TITANIUM ALLOY

The article presents the results of a complex of studies (analysis of microstructure, as well as determination of mechanical properties under tension, impact strength (KCU), low-cycle fatigue (LCF), fracture toughness (K1с)) of large-sized forgings made of titanium alloy Vt6сh, providing for the final deformation in the (α+β)-region, as well as large-sized profiles and stamping made of titanium alloy Vt6сh, providing for the final deformation in the β-region. A comparative analysis of the data obtained during the research shows the dependence of the mechanical properties of semi-finished products with plate-like structure on the size of the structural components – of primary β-grains and colonies of α-plates. This is especially noticeable for the characteristics of plasticity.

Influence of Pressure Vessel Shape on Explosive Forming

The explosive forming is a characteristic forming method. This technique is a metal forming using an underwater shock wave. The underwater shock wave is generated by underwater explosion of the explosive. The metal plate is formed with involving the high strain rate on this technique. In generally, the pressure vessel is used in this method due to the effective utilization of the explosion energy. The underwater shock wave is propagated in water and reflected on inside wall of the pressure vessel. This reflected shock wave is affected on the deformation shape of a metal plate. Therefore, the inside shape of pressure vessel is often changed. In other words, the shape of pressure vessel is changed, the shock pressure distribution on the metal plate and it is possible that final deformation shape of the metal plate is changed. Some numerical simulations and experiments have been carried out to clear the influence of the inside shape of pressure vessel in the explosive forming. This paper is included the results and discussions on the numerical simulation and experiment used those conditions.

Influence of Hot Rolling Technological Regimes on 6061 Aluminium Alloy Sheet Texture

The effect of the hot rolling speed on the textural and structural state of 6061aluminum alloy sheet was investigated. The final deformation temperature allows avoiding the development of recrystallization processes due the decrease of rolling speed. The heterogeneity of the texture state is provided for by the differences in stress conditions for semifinished rolled plate. The deformation texture of the central layer of the hot-rolled sheet corresponds to the stable orientations of the rolling texture of the fcc material. The deformation texture of the surface area generally corresponds to the shear texture of the material with fcc lattice. The recrystallization texture is more scattered, however its component composition is the same as for the deformation texture, but the main orientations can either be maintained of varied.

Comparison of Experimentally Measured Deformation of the Plate on the Subsoil and the Results of 3D Numerical Model

The purpose of this paper is to compare the measured subsidence of the foundation in experiments and subsidence obtained from FEM calculations. When using 3D elements for creation of a 3D model, it is, in particular, essential to choose correctly the size of the modelled area which represents the subsoil, the boundary conditions and the size of the finite element network. The parametric study evaluates impacts of those parameters on final deformation. The parametric study is conducted of 168 variant models.

The Study on Tunnel Surrounding Rock Displacement Prediction

The traditional regression analysis method cant effectively predict the final deformation of divisional excavation. This paper is going to propose prediction technique of piecewise nonlinear fitting according to deformation law of surrounding rock displacement during divisional tunneling, to construct piecewise nonlinear fitting function. Through comparative analysis in engineering application, it is proved that it can better meet the prediction need for surrounding rock deformation during information zing construction with its higher accurate prediction and correlation coefficient.