Application of FM-BEM in rolled piece deformation analysisof straightening process

Rolled piece deformation is analyzed by FM-BEM in straightening process. Deformation rule of plastic deformation area is analyzed in different straightening force, especially the area of the nodes in neutral axis. Through numerical analysis, it shows that plastic deformation of neutral axis nodes applied 250 kN straightening force is smaller than adjacent nodes. With straightening force increasing, this difference disappeared and formed a relatively flat area in 500 kN. The results obtained by FM-BEM demonstrate that neutral layer has some offset under straightening force. Compression bending amount has relationship with the neutral layer offset and it is one of reasons that compression bending amount is inaccurate. These conclusions are not obtained by FEM.     

Roller Bearing by Plate Unit Analogue

Mill Roller bearing is made up of internal ring,middle rolls and external ring,which belongs to multi bodies contact problem.So it is rather difficult and complex to analyze load peculiarities of mill roller bearing directly.In this paper,based on three dimensional elastic contact BEM,it is introduced that middle rolling bodies can be described as plate units,placed on the internal ring,therefore the contact problem can be changed from multi bodies to two bodies.As the elastic deformation of plate unit,it can be calculated by Hertz contact formula and is regarded as a gap to be substituted to the total matrix equality,so the three dimensional distribution of load peculiarities of mill roller bearing can be achieved.The calculating model of this method is visualized and simple, and has higher accuracy,therefore it become effective numerical method to design and analyze load peculiarities of mill roller bearing.     

A novel viscoelastroplastic constitutive model of rubber materials and parameter identification

The plastic unit with a yielding process is used to describe rubber’s amplitude-related characteristic, and the method to identify the number of plastic unit and the distribution of the yielding point is researched. A novel hyperelastic-viscoelastic-plastoelastic constitutive model of rubber is built and its parameters are identified according to the results of the rubber material property experiments. The theoretical model is transfered into the material parameters of rubber in the finite element software, which are used to create the finite element model of rubber material. Finite element simulation results of rubber are in good agreement with the experimental results, so the model can be used for subsequent modeling of rubber bushing and analysis of suspension system.     

Control model for secondary cooling of continuous casting based on compensation temperature of the difference between liquidus and solidus

During continuous casting process, the composition of molten steel often varies with different heats, which leads to the big fluctuation of billet surface temperature when the traditional parameter water control model is applied to control the process. Additionally, it is difficult to keep the temperature at the straightening point of the billet within a reasonable range. Given above consideration, a new control model for secondary cooling of continuous casting based on compensation temperature of the difference between liquidus and solidus has been presented. Meanwhile, the temperature field of the billet is simulated with both the parameter water control model and the new secondary cooling control model, and the results indicate that the new control model for secondary cooling of continuous casting could perform better when it is used to control the surface temperature at straightening points of billet, thereby ensuring the quality of the billet.     

Mechanical Model of Steel Plate Composite Shear Walls

Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed.     

Shear Performance of Steel Plate with Trilateral Constrained

The load carrying test for four steel plate shear walls specimens with various ratio of width thickness are carried out so as to test the failure mode and the shear strength of steel plate with trilateral constrained, and the lateral stiffness and the buckling mode are investigated in the test. The result indicates that the ratio of width thickness of steel plate exerts effects on the shear carrying capacity and failure mode; the buckling of steel plate does not have lateral stiffness. Based on the failure mode of steel plate, the computation model of lateral performance is presented by theoretical analysis. The restraining stiffness of double angle and the buckling restrained stiffness of steel plate are the important design conditions. Formulae to determine the elastic lateral stiffness and the angle type is proposed, which can be used in the preliminary design of steel plate with trilateral constrained.     

Study on strain localization and progressive failureof surrounding rock under high pressure environment

This paper uses the Mohr-Coulomb criterion with tension cut-off strain-softening model and the large-strain calculation method to study the localized deformation and progressive failure.It investigates the process of stain localization appearing,growing and sample failure,and uses the physical and numerical simulation to explore the relationship between strain localization and progressive failure of surrounding rock.The results show that the soften character of rock sample is caused by stain localization.The breach point of progressive failure is founded based on the distribution law of plastic zones and soften strips.The key causes of the tunnel convergence deformation after opening are the plastic extrusion and the elastic deformation of rock yield units caused by stress release.     

Analysis of ultimate load and mechanismsof failure in large cast steel joints

Based on a project of pipe truss roof framing in Chengdu, the ultimate limit state analysis is performed on cast steel joints by using FEM, in which Linear hardening elastic-plastic constitutive model is considered. The results show that, the joint has a great accumulation of plastic strain in ultimate loads, and the point of maximum stress is different from that in elastic with the development of the yielding zone. The paper propoes to use rate-type tensor for the large strain geometric nonlinear problem, shows the criterion of failure formation , and indicates that its essential to apply limit state analysis to the determination of the weakest location on cast steel joint design, which provides basis for understanding the failure modes and failure mechanism of cast steel joint and the cast steel joint design.     

INTELLIGENT MOISTURE METER

This paper introduces the intelligent moisture meter with a single-component microcomputer.The meter ismade according to a mathematical model tot moisture measurement.The paper mainly discusses the characeristics of hardware struc-ture and design of procedure.The meter is accurate,stable abd widely used.The appraisal of the meter is made and it is produced in hatches.     

A simplified approach to define the yield surface of concrete-filled square steel tubes subjected to compression-bending

When the plastic hinge method is used to simulate the elasto-plastic properties of concrete-filled steel tubular structures,the plastic interactive yield surfaces of concrete-filled steel tubular column sections need to be defined.Although the fiber model approach can be well applied to the yield surface analysis,the numerical method is still complicated for the real applications.Therefore based on the experimental and theoretical researches on concrete-filled square steel tubular (CFST) members,this paper develops one method to determine the elastic element parameters.Then a simplified approach to quickly define the axial force-moment interactive plastic yield surface of concrete-filled square steel tubular columns is developed through theoretical analysis and a large number of parametric analyses.Finally,the fiber model method is adopted to verify the feasibility and validity of the proposed method.Results of the two methods are in good agreement,which indicates that the proposed method is reliable.     

Seismic Behavior of a Slope Protected by a Soil Nailing Retaining Wall during an Earthquake

The dynamic elastic plastic finite element method was used to study the seismic performance of a slope protected by a soil nailing retaining wall. On the basis of working in parallel and interaction between loess and a flexible retaining wall, a 3 D nonlinear finite element method (ADINA) also was established. Rational earthquake excitation and damping were discussed for geological engineering. Horizontal and vertical excitations were considered simultaneously in the analyses. A model capable of simulating the nonlinear static and dynamic elastic plastic behavior of soil was used to model the soil, and a bilinear elastic plastic model having hardening behavior was used to model the soil nailing. A friction element was employed to describe the soil structure interaction behavior. Our research focused on the seismic performance of the horizontal and vertical slope deformation, soil nailing axial force, and earth pressure subjected to horizontal and vertical excitations. The results show that the seismic performance of slope protected by soil nailing is good; soil nailing axial force increases after an earthquake; permanent slope displacement occurs during an earthquake; and the peak earth pressure distribution during an earthquake is similar to the earth pressure before the earthquake. These conclusions can provide references for seismic analyses and design in soil nailing engineering.     

Closed-form Analytical Solution for Beam on Elastic Foundation with Different Tension and Compression Modulus

On the basis of the theory of different modulus, the closed-form analytical solution for beams on elastic foundations with different modulus has been derived. A comparison is made between the results of the analytical solution and those calculated from the classic mechanic theories, in which the tension modulus are equal to the compression modulus. It is shown from the numerical results that the ratio of compressive modulus to tensile modulus will greatly affect the elastic characteristic values,internal forces and flexibilities. The present theory satisfies the mechanical behavior of materials. The amount of materials can be economized through rational design by using the elastic theory of different modulus.     

Numerical simulation and experimental investigation of residualstress in the stretching process of the 7075 aluminum alloy

Numerical simulation of the direct thermo-mechanical coupling of temperature field and stress field during the 7075 aluminium alloy plate’s quenching process is investigated and the distribution tendency of residual stress is acquired. Numerical simulation of the elimination effect of varying stretching rates on the residual stress in the stretching process is carried out based on isotropic hardening Mises yield criterion and Prandtl-Reuss plastic flow rule with incremental theory. Then blind hole method is adopted to measure the residual stress. Both results show the optimum stretching rate for 12 mm thick 7075 aluminum alloy plate is 1%. From the residual stress distribution rules, it is showed that with varying stretching rates, the elimination effects of surface and internal residual stresses have similar variation tendency.     

Numerical simulation and experimental investigation of double-stage sheet incremental forming

In order to find a method to reduce excessive sheet thinning in the forming process of small half-apex angle parts by incremental sheet forming, a finite element model (FEM) for simulating double-stage process is developed in ABAQUS. Then, the simulation results, such as sheet thickness distribution and equivalent plastic strain history, are compared with those of single-stage simulation. The effects of double-stage on formability of sheet are discussed. The results show that using double-stage process instead of single-stage in forming parts, the maximum deformation is nearer to the parts’ bottom surface, and the maximum equivalent plastic strain of node A, B, C is reduced by 66.2%, 81.9% and 36.0% respectively. The sheet thickness is better distributed, and the minimum thickness increases by 16%. In addition, double-stage incremental forming can greatly improve the formability of sheet. The simulation results are in a good agreement with experimental results.     

3D Meso scale Failure Simulation of Four phase Composite Concrete

Taking into account the influence of the internal micro cracks on the strength and deformation of concrete, a four phase composite material model was proposed, in which it included mortar, aggregate, interface and random defects. Meso scale unit in concrete was subjected to elastic plastic damage constitutive of increments form in strain space. With the simulation of mesh concrete crack growth by damage elimination, the damage processes of concrete under 3 D uniaxial compression and the elasto plastic damage process of concrete under uniaxial tension with heterogeneous specimen were obtained. It was shown that the proposed four phase model added the simulation of random defects, with which it was more appropriate to the actual situation in concrete forming. The percentage of random defects in volume was the key to determine the weakening degree of macro strength of concrete. The cracks occlusion was obvious for the lower homogeneous uniaxial tension specimen and the fracture was clearer for higher homogeneous specimen. The simulation results was in good agreement with test results.     

Analysis of the Double-layer Sub-grade with Rigid Upper Layer and Soft Lower Layer by FEM

The double layer subgrade with rigid upper layer and soft lower layer is common in engineering construction. In this paper, the elastic and elasto-plastic analysis on such subgrade by ANSYS was carried out. According to the calculation results of FEM, the plastic zone of subgrade would appear in the upper layer soil of interface, then, it would be expanded up and down with increase of the load. As for the lower layer soil is relatively soft, the plastic zone is expanding rapidly. Finally, as the plastic zone reaches the bottom and the subgrade in the state of ultimate bearing capacity, the calculation starts to be non-convergent. The results can serve as reference to the engineering designers.     

Analysis on Reinforced Concrete Flexural Members Using Deformation Condensation Method

Traditional nonlinear analysis of RC structures usually adopts nonlinear FEM based on continuum mechanics, and it is hard to reflect macroscopic deformation characteristic, such as local rotation in crack sections and plastic hinge of failure stage. From the perspective of physical model, a new deformation condensation method is developed. The analysis of RC flexural members in the 1-D elastic problem involve three stages based on the concept of deformation condensation. RC flexural members were divided into several elements according to average crack spacing to get numerical model consistent with the physical model with higher computational efficiency tests of RC flexural members reinforced with high strength rebars conducted by Institute of Prestressed Structures in Tongji University, were simulated and the simulation results agreed well with the experimental data indicating that this novel method is applicable.     

Design in the mandrel land and smoothing the deformation of rectangular tube drawing

With mandrel drawing process and the mechanisms of smoothing deformation have been analyzed. A method of smoothing deformation is brought forward that rectangular tube should be extruded uniformity out of die land with little amount of deformation. The dynamics model simplified and FE model of with mandrel drawing process are established based on FEM software, then simulations are performed. Three points including the center of long side, the center of short side, and the center of corner are positioned for further analysis. As for linear type and step type mandrel lands, the effective plastic strain and contact stress of three key points are evaluated. As for the plastic strain at the center of long side, a most difficult place to ensure surface quality, step type mandrel land can improve 45.5%. As for the contact stress, step type mandrel land can increase to 13MPa from 0. Drawing with step type mandrel land achieves the stress status tensile stress in one orientation and compressive stress in other two orientations, which purposes of little amount of deformation to correct thickness tolerance and improve inner and outer surface quality of rectangular tube.     

Thermodynamical analysis and simulation of smelting reduction process in magnesium production

In order to improve the response speed of materials in silicothermic reduction process for magnesium production, a new technology-smelting reduction process is presented. Adding an appropriate amount of Al2O3 and SiO2 can make slag completely melt in whole reduction process, thus the reaction rate can be sped up. Through software simulation, thermodynamic analysis and experimental verification, it’s found that completely molten CaO-MgO-Al2O3-SiO2 slag can be got at 1 600 ℃ with appropriate material component. The new reduction process is thermodynamically analyzed, and the results show that in equilibrium state, when the reduction temperature is 1 600 ℃, the dew-point temperature of the magnesium vapor is 870 ℃. It suggests that the new technology is feasible.     

Finite element model of coupled systems for vibration reduction plates with smart constrained layer damping

Considering the relationships of coupling movement and compatible displacement among bonding layer, piezoelectric layer, damping layer, and base structure, a finite element dynamic model of coupled systems for vibration reduction plates is established. The model combined with piezoelectric theory, finite element theory and ADF model of viscoelastic damping material can be suitable for vibration model of complex SCLD structure. The dynamics parameters for clamped-clamped steel plate with partially treated smart constrained layer damping are obtained by theoretical calculation, ANSYS modal analysis and modal experiment. The results show that theoretical values are closer to the test results and ANSYS analysis, and the methods proposed is more accurate and effective.