The Central Strain Analytical Modeling and Analysis for the Plate Rolling Process

The strain after rolling plays an important role in the prediction of the microstructure and properties and plate deformation permeability. So it is necessary to establish a more accurate theoretical strain model for the rolling process. This paper studies the modeling method of the equivalent strain based on the upper bound principle and stream function method. The rolling deformation region is divided into three zones (inlet rigid zone, plastic zone, and outlet rigid zone) according to the kinematics. The boundary conditions of adjacent deformation zones are modified according to the characteristics of each deformation zone. A near-real kinematics admissible velocity field is established by the stream function method on this basis. The geometric boundary conditions of the deformation region are obtained. The deformation power, friction power and velocity discontinuous power are calculated according to the redefined geometric boundary conditions. On this basis, the generalized shear strain rate intensity is calculated according to the minimum energy principle. Finally, the equivalent strain model after rolling is obtained by integrating the generalized shear strain rate in time. The plate rolling experiments of AA1060 and the numerical simulations are carried out with different rolling reductions to verify the analytic model precision of the equivalent strain. The results show that the minimum and maximum relative equivalent strain deviation between the analytic model and the experiment is 0.52% and 9.96%, respectively. The numerical calculation and experimental results show that the model can accurately calculate the strain along the plate thickness. This model can provide an important reference for the rolling process setup and the microstructure and properties prediction.

SHVEDOV-BINGHAM MODEL OF STEADY FLOW OF VISCO-PLASTIC BITUMEN BINDER IN CYLINDRICAL TUBE

This paper studies the bitumen binder flow in terms of the Shvedov-Bingham model in a cylindrical tube. The dependence of the fluid flow rate on pressure drop is determined as well as the dependences between the radial velocity distribution and effective flow viscosity. Near the wall, the effective viscosity is low. However, in the vicinity of the rigid zone, a significant increase in the effective viscosity is observed. With increasing strain rates the effective viscosity decreases, which is explained by the destruction of the medium microstructure. With the pressure drop, the size of the hard zone decreases. With the increasing yield stress the fluid becomes less mobile, the rigid zone in the centre of the pipe increases in size. In this case, the velocity values decrease over the entire pipe section. Variation in the plastic viscosity does not affect the position of the rigid zone. It is shown that when the Bingam number Bn < 0.1, the non-Newtonian properties of the flow can be ignored. In this case, the Newtonian flow with viscosity mpl should be considered with an accuracy sufficient for engineering calculations.

Strengthening of the Panel Zone in Steel Moment Resisting Frames

Rehabilitation and retrofitting of structures designed in accordance to standard design codes is an essential practice in structural engineering and design. For steel structures, one of the challenges is to strengthen the panel zone as well as its analysis in moment-resisting frames. In this research, investigations were undertaken to analyze the influence of the panel zone in the response of structural frames through a computational approach using ETABS software. Moment-resisting frames of six stories were studied in supposition of real panel zone, different values of rigid zone factor, different thickness of double plates, and both double plates and rigid zone factor together. The frames were analyzed, designed and validated in accordance to Iranian steel building code. The results of drift values for six stories building models were plotted. After verifying and comparing the results, the findings showed that the rigidity lead to reduction in drifts of frames and also as a result, lower rigidity will be used for high rise building and higher rigidity will be used for low rise building. In frames with story drifts more than the permitted rate, where the frames are considered as the weaker panel zone area, the story drifts can be limited by strengthening the panel zone with double plates. It should be noted that higher thickness of double plates and higher rigidity of panel zone will result in enhancement of the non-linear deformation rates in beam elements. The resulting deformations of the panel zone due to this modification can have significant influence on the elastic and inelastic behavior of the frames.

Research on the Influence of Conical Anvil on Upsetting Process of Forging by Finite Element Simulation

The upsetting process of cylindrical forging was investigated using finite element method. The influence of conical anvil on deformation rule of metal and distribution of strain and stress was studied using software MSC. Marc. The simulated results indicated that it had a smaller rigid zone and more homogeneous deformation zone in the billet during upsetting process with conical anvil compared with flat anvil. The critical reduction in height which could assure the three dimensional compressive stress states for the upsetting with conical anvil was smaller than that for the flat one.

Singular Plastic Fields in Steady Penetration of a Rigid Cone

The essential features of the active plastic zone at the tip of a penetrating rigid cone are investigated for a rigid/perfectly plastic solid. An exact solution is suggested for the plastic zone. A rigid zone exists ahead of the cone and is separated from the plastic zone by a conical surface of discontinuity. It is assumed that the material yields instantaneously by going through a “shear shock” across the rigid/plastic interface. The orientation of the interface is determined by an ad hoc requirement for minimum shear strain jump at the shear shock. Results are presented for different cone angles and friction factors. The stresses within the plastic zone admit a logarithmic singularity whose level increases with cone angle and wall friction.